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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 17:43:51 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 17:43:51 +0000 |
| commit | be58c81aff4cd4c0ccf43dbd7998da4a6a08c03b (patch) | |
| tree | 779c248fb61c83f65d1f0dc867f2053d76b4e03a /docs/components | |
| parent | Initial commit. (diff) | |
| download | arm-trusted-firmware-be58c81aff4cd4c0ccf43dbd7998da4a6a08c03b.tar.xz arm-trusted-firmware-be58c81aff4cd4c0ccf43dbd7998da4a6a08c03b.zip | |
Adding upstream version 2.10.0+dfsg.upstream/2.10.0+dfsgupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
31 files changed, 8969 insertions, 0 deletions
diff --git a/docs/components/activity-monitors.rst b/docs/components/activity-monitors.rst new file mode 100644 index 0000000..5c1c2c2 --- /dev/null +++ b/docs/components/activity-monitors.rst @@ -0,0 +1,34 @@ +Activity Monitors +================= + +FEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors +extension. This extension describes the architecture for the Activity Monitor +Unit (|AMU|), an optional non-invasive component for monitoring core events +through a set of 64-bit counters. + +When the ``ENABLE_FEAT_AMU=1`` build option is provided, Trusted Firmware-A +sets up the |AMU| prior to its exit from EL3, and will save and restore +architected |AMU| counters as necessary upon suspend and resume. + +.. _Activity Monitor Auxiliary Counters: + +Auxiliary counters +------------------ + +FEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also +known as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` +build option. + +As a security precaution, Trusted Firmware-A does not enable these by default. +Instead, platforms may configure their auxiliary counters through one of two +possible mechanisms: + +- |FCONF|, controlled by the ``ENABLE_AMU_FCONF`` build option. +- A platform implementation of the ``plat_amu_topology`` function (the default). + +See :ref:`Activity Monitor Unit (AMU) Bindings` for documentation on the |FCONF| +device tree bindings. + +-------------- + +*Copyright (c) 2021, Arm Limited. All rights reserved.* diff --git a/docs/components/arm-sip-service.rst b/docs/components/arm-sip-service.rst new file mode 100644 index 0000000..b51a94d --- /dev/null +++ b/docs/components/arm-sip-service.rst @@ -0,0 +1,435 @@ +Arm SiP Services +================ + +This document enumerates and describes the Arm SiP (Silicon Provider) services. + +SiP services are non-standard, platform-specific services offered by the silicon +implementer or platform provider. They are accessed via ``SMC`` ("SMC calls") +instruction executed from Exception Levels below EL3. SMC calls for SiP +services: + +- Follow `SMC Calling Convention`_; +- Use SMC function IDs that fall in the SiP range, which are ``0xc2000000`` - + ``0xc200ffff`` for 64-bit calls, and ``0x82000000`` - ``0x8200ffff`` for 32-bit + calls. + +The Arm SiP implementation offers the following services: + +- Performance Measurement Framework (PMF) +- Execution State Switching service +- DebugFS interface + +Source definitions for Arm SiP service are located in the ``arm_sip_svc.h`` header +file. + +Performance Measurement Framework (PMF) +--------------------------------------- + +The :ref:`Performance Measurement Framework <firmware_design_pmf>` +allows callers to retrieve timestamps captured at various paths in TF-A +execution. + +Execution State Switching service +--------------------------------- + +Execution State Switching service provides a mechanism for a non-secure lower +Exception Level (either EL2, or NS EL1 if EL2 isn't implemented) to request to +switch its execution state (a.k.a. Register Width), either from AArch64 to +AArch32, or from AArch32 to AArch64, for the calling CPU. This service is only +available when Trusted Firmware-A (TF-A) is built for AArch64 (i.e. when build +option ``ARCH`` is set to ``aarch64``). + +``ARM_SIP_SVC_EXE_STATE_SWITCH`` +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Arguments: + uint32_t Function ID + uint32_t PC hi + uint32_t PC lo + uint32_t Cookie hi + uint32_t Cookie lo + + Return: + uint32_t + +The function ID parameter must be ``0x82000020``. It uniquely identifies the +Execution State Switching service being requested. + +The parameters *PC hi* and *PC lo* defines upper and lower words, respectively, +of the entry point (physical address) at which execution should start, after +Execution State has been switched. When calling from AArch64, *PC hi* must be 0. + +When execution starts at the supplied entry point after Execution State has been +switched, the parameters *Cookie hi* and *Cookie lo* are passed in CPU registers +0 and 1, respectively. When calling from AArch64, *Cookie hi* must be 0. + +This call can only be made on the primary CPU, before any secondaries were +brought up with ``CPU_ON`` PSCI call. Otherwise, the call will always fail. + +The effect of switching execution state is as if the Exception Level were +entered for the first time, following power on. This means CPU registers that +have a defined reset value by the Architecture will assume that value. Other +registers should not be expected to hold their values before the call was made. +CPU endianness, however, is preserved from the previous execution state. Note +that this switches the execution state of the calling CPU only. This is not a +substitute for PSCI ``SYSTEM_RESET``. + +The service may return the following error codes: + +- ``STATE_SW_E_PARAM``: If any of the parameters were deemed invalid for + a specific request. +- ``STATE_SW_E_DENIED``: If the call is not successful, or when TF-A is + built for AArch32. + +If the call is successful, the caller wouldn't observe the SMC returning. +Instead, execution starts at the supplied entry point, with the CPU registers 0 +and 1 populated with the supplied *Cookie hi* and *Cookie lo* values, +respectively. + +DebugFS interface +----------------- + +The optional DebugFS interface is accessed through an SMC SiP service. Refer +to the component documentation for details. + +String parameters are passed through a shared buffer using a specific union: + +.. code:: c + + union debugfs_parms { + struct { + char fname[MAX_PATH_LEN]; + } open; + + struct mount { + char srv[MAX_PATH_LEN]; + char where[MAX_PATH_LEN]; + char spec[MAX_PATH_LEN]; + } mount; + + struct { + char path[MAX_PATH_LEN]; + dir_t dir; + } stat; + + struct { + char oldpath[MAX_PATH_LEN]; + char newpath[MAX_PATH_LEN]; + } bind; + }; + +Format of the dir_t structure as such: + +.. code:: c + + typedef struct { + char name[NAMELEN]; + long length; + unsigned char mode; + unsigned char index; + unsigned char dev; + qid_t qid; + } dir_t; + + +* Identifiers + +======================== ============================================= +SMC_OK 0 +SMC_UNK -1 +DEBUGFS_E_INVALID_PARAMS -2 +======================== ============================================= + +======================== ============================================= +MOUNT 0 +CREATE 1 +OPEN 2 +CLOSE 3 +READ 4 +WRITE 5 +SEEK 6 +BIND 7 +STAT 8 +INIT 10 +VERSION 11 +======================== ============================================= + +MOUNT +~~~~~ + +Description +^^^^^^^^^^^ +This operation mounts a blob of data pointed to by path stored in `src`, at +filesystem location pointed to by path stored in `where`, using driver pointed +to by path in `spec`. + +Parameters +^^^^^^^^^^ +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``MOUNT`` +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if mount operation failed +=============== ========================================================== + +OPEN +~~~~ + +Description +^^^^^^^^^^^ +This operation opens the file path pointed to by `fname`. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``OPEN`` +uint32_t mode +======== ============================================================ + +mode can be one of: + +.. code:: c + + enum mode { + O_READ = 1 << 0, + O_WRITE = 1 << 1, + O_RDWR = 1 << 2, + O_BIND = 1 << 3, + O_DIR = 1 << 4, + O_STAT = 1 << 5 + }; + +Return values +^^^^^^^^^^^^^ + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if open operation failed + +uint32_t w1: file descriptor id on success. +=============== ========================================================== + +CLOSE +~~~~~ + +Description +^^^^^^^^^^^ + +This operation closes a file described by a file descriptor obtained by a +previous call to OPEN. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``CLOSE`` +uint32_t File descriptor id returned by OPEN +======== ============================================================ + +Return values +^^^^^^^^^^^^^ +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if close operation failed +=============== ========================================================== + +READ +~~~~ + +Description +^^^^^^^^^^^ + +This operation reads a number of bytes from a file descriptor obtained by +a previous call to OPEN. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``READ`` +uint32_t File descriptor id returned by OPEN +uint32_t Number of bytes to read +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +On success, the read data is retrieved from the shared buffer after the +operation. + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if read operation failed + +uint32_t w1: number of bytes read on success. +=============== ========================================================== + +SEEK +~~~~ + +Description +^^^^^^^^^^^ + +Move file pointer for file described by given `file descriptor` of given +`offset` related to `whence`. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``SEEK`` +uint32_t File descriptor id returned by OPEN +sint32_t offset in the file relative to whence +uint32_t whence +======== ============================================================ + +whence can be one of: + +========= ============================================================ +KSEEK_SET 0 +KSEEK_CUR 1 +KSEEK_END 2 +========= ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if seek operation failed +=============== ========================================================== + +BIND +~~~~ + +Description +^^^^^^^^^^^ + +Create a link from `oldpath` to `newpath`. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``BIND`` +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if bind operation failed +=============== ========================================================== + +STAT +~~~~ + +Description +^^^^^^^^^^^ + +Perform a stat operation on provided file `name` and returns the directory +entry statistics into `dir`. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``STAT`` +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ========================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if stat operation failed +=============== ========================================================== + +INIT +~~~~ + +Description +^^^^^^^^^^^ +Initial call to setup the shared exchange buffer. Notice if successful once, +subsequent calls fail after a first initialization. The caller maps the same +page frame in its virtual space and uses this buffer to exchange string +parameters with filesystem primitives. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``INIT`` +uint64_t Physical address of the shared buffer. +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ====================================================== +int32_t w0 == SMC_OK on success + + w0 == DEBUGFS_E_INVALID_PARAMS if already initialized, + or internal error occurred. +=============== ====================================================== + +VERSION +~~~~~~~ + +Description +^^^^^^^^^^^ +Returns the debugfs interface version if implemented in TF-A. + +Parameters +^^^^^^^^^^ + +======== ============================================================ +uint32_t FunctionID (0x82000030 / 0xC2000030) +uint32_t ``VERSION`` +======== ============================================================ + +Return values +^^^^^^^^^^^^^ + +=============== ====================================================== +int32_t w0 == SMC_OK on success + + w0 == SMC_UNK if interface is not implemented + +uint32_t w1: On success, debugfs interface version, 32 bits + value with major version number in upper 16 bits and + minor version in lower 16 bits. +=============== ====================================================== + +* CREATE(1) and WRITE (5) command identifiers are unimplemented and + return `SMC_UNK`. + +-------------- + +*Copyright (c) 2017-2020, Arm Limited and Contributors. All rights reserved.* + +.. _SMC Calling Convention: https://developer.arm.com/docs/den0028/latest diff --git a/docs/components/cot-binding.rst b/docs/components/cot-binding.rst new file mode 100644 index 0000000..4f8c8b7 --- /dev/null +++ b/docs/components/cot-binding.rst @@ -0,0 +1,332 @@ +Chain of trust bindings +======================= + +The device tree allows to describe the chain of trust with the help of +'cot' node which contain 'manifests' and 'images' as sub-nodes. +'manifests' and 'images' nodes contains number of sub-nodes (i.e. 'certificate' +and 'image' nodes) mentioning properties of the certificate and image respectively. + +Also, device tree describes 'non-volatile-counters' node which contains number of +sub-nodes mentioning properties of all non-volatile-counters used in the chain of trust. + +cot +------------------------------------------------------------------ +This is root node which contains 'manifests' and 'images' as sub-nodes + + +Manifests and Certificate node bindings definition +---------------------------------------------------------------- + +- Manifests node + Description: Container of certificate nodes. + + PROPERTIES + + - compatible: + Usage: required + + Value type: <string> + + Definition: must be "arm, cert-descs" + +- Certificate node + Description: + + Describes certificate properties which are used + during the authentication process. + + PROPERTIES + + - root-certificate + Usage: + + Required for the certificate with no parent. + In other words, certificates which are validated + using root of trust public key. + + Value type: <boolean> + + - image-id + Usage: Required for every certificate with unique id. + + Value type: <u32> + + - parent + Usage: + + It refers to their parent image, which typically contains + information to authenticate the certificate. + This property is required for all non-root certificates. + + This property is not required for root-certificates + as root-certificates are validated using root of trust + public key provided by platform. + + Value type: <phandle> + + - signing-key + Usage: + + This property is used to refer public key node present in + parent certificate node and it is required property for all + non-root certificates which are authenticated using public-key + present in parent certificate. + + This property is not required for root-certificates + as root-certificates are validated using root of trust + public key provided by platform. + + Value type: <phandle> + + - antirollback-counter + Usage: + + This property is used by all certificates which are + protected against rollback attacks using a non-volatile + counter and it is an optional property. + + This property is used to refer one of the non-volatile + counter sub-node present in 'non-volatile counters' node. + + Value type: <phandle> + + + SUBNODES + - Description: + + Hash and public key information present in the certificate + are shown by these nodes. + + - public key node + Description: Provide public key information in the certificate. + + PROPERTIES + + - oid + Usage: + + This property provides the Object ID of public key + provided in the certificate which the help of which + public key information can be extracted. + + Value type: <string> + + - hash node + Description: Provide the hash information in the certificate. + + PROPERTIES + + - oid + Usage: + + This property provides the Object ID of hash provided in + the certificate which the help of which hash information + can be extracted. + + Value type: <string> + +Example: + +.. code:: c + + cot { + manifests { + compatible = "arm, cert-descs” + + trusted-key-cert: trusted-key-cert { + root-certificate; + image-id = <TRUSTED_KEY_CERT_ID>; + antirollback-counter = <&trusted_nv_counter>; + + trusted-world-pk: trusted-world-pk { + oid = TRUSTED_WORLD_PK_OID; + }; + non-trusted-world-pk: non-trusted-world-pk { + oid = NON_TRUSTED_WORLD_PK_OID; + }; + }; + + scp_fw_key_cert: scp_fw_key_cert { + image-id = <SCP_FW_KEY_CERT_ID>; + parent = <&trusted-key-cert>; + signing-key = <&trusted_world_pk>; + antirollback-counter = <&trusted_nv_counter>; + + scp_fw_content_pk: scp_fw_content_pk { + oid = SCP_FW_CONTENT_CERT_PK_OID; + }; + }; + . + . + . + + next-certificate { + + }; + }; + }; + +Images and Image node bindings definition +----------------------------------------- + +- Images node + Description: Container of image nodes + + PROPERTIES + + - compatible: + Usage: required + + Value type: <string> + + Definition: must be "arm, img-descs" + +- Image node + Description: + + Describes image properties which will be used during + authentication process. + + PROPERTIES + + - image-id + Usage: Required for every image with unique id. + + Value type: <u32> + + - parent + Usage: + + Required for every image to provide a reference to + its parent image, which contains the necessary information + to authenticate it. + + Value type: <phandle> + + - hash + Usage: + + Required for all images which are validated using + hash method. This property is used to refer hash + node present in parent certificate node. + + Value type: <phandle> + + Note: + + Currently, all images are validated using 'hash' + method. In future, there may be multiple methods can + be used to validate the image. + +Example: + +.. code:: c + + cot { + images { + compatible = "arm, img-descs"; + + scp_bl2_image { + image-id = <SCP_BL2_IMAGE_ID>; + parent = <&scp_fw_content_cert>; + hash = <&scp_fw_hash>; + }; + + . + . + . + + next-img { + + }; + }; + }; + +non-volatile counter node binding definition +-------------------------------------------- + +- non-volatile counters node + Description: Contains properties for non-volatile counters. + + PROPERTIES + + - compatible: + Usage: required + + Value type: <string> + + Definition: must be "arm, non-volatile-counter" + + - #address-cells + Usage: required + + Value type: <u32> + + Definition: + + Must be set according to address size + of non-volatile counter register + + - #size-cells + Usage: required + + Value type: <u32> + + Definition: must be set to 0 + + SUBNODE + - counters node + Description: Contains various non-volatile counters present in the platform. + + PROPERTIES + - id + Usage: Required for every nv-counter with unique id. + + Value type: <u32> + + - reg + Usage: + + Register base address of non-volatile counter and it is required + property. + + Value type: <u32> + + - oid + Usage: + + This property provides the Object ID of non-volatile counter + provided in the certificate and it is required property. + + Value type: <string> + +Example: +Below is non-volatile counters example for ARM platform + +.. code:: c + + non_volatile_counters: non_volatile_counters { + compatible = "arm, non-volatile-counter"; + #address-cells = <1>; + #size-cells = <0>; + + trusted-nv-counter: trusted_nv_counter { + id = <TRUSTED_NV_CTR_ID>; + reg = <TFW_NVCTR_BASE>; + oid = TRUSTED_FW_NVCOUNTER_OID; + }; + + non_trusted_nv_counter: non_trusted_nv_counter { + id = <NON_TRUSTED_NV_CTR_ID>; + reg = <NTFW_CTR_BASE>; + oid = NON_TRUSTED_FW_NVCOUNTER_OID; + }; + }; + +Future update to chain of trust binding +--------------------------------------- + +This binding document needs to be revisited to generalise some terminologies +which are currently specific to X.509 certificates for e.g. Object IDs. + +*Copyright (c) 2020, Arm Limited. All rights reserved.* diff --git a/docs/components/debugfs-design.rst b/docs/components/debugfs-design.rst new file mode 100644 index 0000000..2536515 --- /dev/null +++ b/docs/components/debugfs-design.rst @@ -0,0 +1,125 @@ +======== +Debug FS +======== + +.. contents:: + +Overview +-------- + +The *DebugFS* feature is primarily aimed at exposing firmware debug data to +higher SW layers such as a non-secure component. Such component can be the +TFTF test payload or a Linux kernel module. + +Virtual filesystem +------------------ + +The core functionality lies in a virtual file system based on a 9p file server +interface (`Notes on the Plan 9 Kernel Source`_ and +`Linux 9p remote filesystem protocol`_). +The implementation permits exposing virtual files, firmware drivers, and file blobs. + +Namespace +~~~~~~~~~ + +Two namespaces are exposed: + + - # is used as root for drivers (e.g. #t0 is the first uart) + - / is used as root for virtual "files" (e.g. /fip, or /dev/uart) + +9p interface +~~~~~~~~~~~~ + +The associated primitives are: + +- Unix-like: + + - open(): create a file descriptor that acts as a handle to the file passed as + an argument. + - close(): close the file descriptor created by open(). + - read(): read from a file to a buffer. + - write(): write from a buffer to a file. + - seek(): set the file position indicator of a file descriptor either to a + relative or an absolute offset. + - stat(): get information about a file (type, mode, size, ...). + +.. code:: c + + int open(const char *name, int flags); + int close(int fd); + int read(int fd, void *buf, int n); + int write(int fd, void *buf, int n); + int seek(int fd, long off, int whence); + int stat(char *path, dir_t *dir); + +- Specific primitives : + + - mount(): create a link between a driver and spec. + - create(): create a file in a specific location. + - bind(): expose the content of a directory to another directory. + +.. code:: c + + int mount(char *srv, char *mnt, char *spec); + int create(const char *name, int flags); + int bind(char *path, char *where); + +This interface is embedded into the BL31 run-time payload when selected by build +options. The interface multiplexes drivers or emulated "files": + +- Debug data can be partitioned into different virtual files e.g. expose PMF + measurements through a file, and internal firmware state counters through + another file. +- This permits direct access to a firmware driver, mainly for test purposes + (e.g. a hardware device that may not be accessible to non-privileged/ + non-secure layers, or for which no support exists in the NS side). + +SMC interface +------------- + +The communication with the 9p layer in BL31 is made through an SMC conduit +(`SMC Calling Convention`_), using a specific SiP Function Id. An NS +shared buffer is used to pass path string parameters, or e.g. to exchange +data on a read operation. Refer to :ref:`ARM SiP Services <arm sip services>` +for a description of the SMC interface. + +Security considerations +----------------------- + +- Due to the nature of the exposed data, the feature is considered experimental + and importantly **shall only be used in debug builds**. +- Several primitive imply string manipulations and usage of string formats. +- Special care is taken with the shared buffer to avoid TOCTOU attacks. + +Limitations +----------- + +- In order to setup the shared buffer, the component consuming the interface + needs to allocate a physical page frame and transmit its address. +- In order to map the shared buffer, BL31 requires enabling the dynamic xlat + table option. +- Data exchange is limited by the shared buffer length. A large read operation + might be split into multiple read operations of smaller chunks. +- On concurrent access, a spinlock is implemented in the BL31 service to protect + the internal work buffer, and re-entrancy into the filesystem layers. +- Notice, a physical device driver if exposed by the firmware may conflict with + the higher level OS if the latter implements its own driver for the same + physical device. + +Applications +------------ + +The SMC interface is accessible from an NS environment, that is: + +- a test payload, bootloader or hypervisor running at NS-EL2 +- a Linux kernel driver running at NS-EL1 +- a Linux userspace application through the kernel driver + +-------------- + +*Copyright (c) 2019-2020, Arm Limited and Contributors. All rights reserved.* + +.. _SMC Calling Convention: https://developer.arm.com/docs/den0028/latest +.. _Notes on the Plan 9 Kernel Source: http://lsub.org/who/nemo/9.pdf +.. _Linux 9p remote filesystem protocol: https://www.kernel.org/doc/Documentation/filesystems/9p.txt +.. _ARM SiP Services: arm-sip-service.rst diff --git a/docs/components/el3-spmc.rst b/docs/components/el3-spmc.rst new file mode 100644 index 0000000..1a2d427 --- /dev/null +++ b/docs/components/el3-spmc.rst @@ -0,0 +1,597 @@ +EL3 Secure Partition Manager +**************************** + +.. contents:: + +Foreword +======== + +This document describes the design of the EL3 SPMC based on the FF-A specification. +EL3 SPMC provides reference FF-A compliant implementation without S-EL2 virtualization support, +to help adopt and migrate to FF-A early. +EL3 SPMC implementation in TF-A: + +- Manages a single S-EL1 Secure Partition +- Provides a standard protocol for communication and memory sharing between FF-A endpoints. +- Provides support for EL3 Logical Partitions to support easy migration from EL3 to S-EL1. + +Sample reference stack +====================== + +The following diagram illustrates a possible configuration when the +FEAT_SEL2 architecture extension is not implemented, showing the SPMD +and SPMC at EL3, one S-EL1 secure partition, with an optional +Hypervisor: + +.. image:: ../resources/diagrams/ff-a-spm-at-el3.png + +TF-A build options +================== + +This section explains the TF-A build options involved in building +an FF-A based SPM where the SPMD and SPMC are located at EL3: + +- **SPD=spmd**: this option selects the SPMD component to relay the FF-A + protocol from NWd to SWd back and forth. It is not possible to + enable another Secure Payload Dispatcher when this option is chosen. +- **SPMC_AT_EL3**: this option adjusts the SPMC exception level to being + at EL3. +- **ARM_SPMC_MANIFEST_DTS**: this option specifies a manifest file + providing SP description. It is required when + ``SPMC_AT_EL3`` is enabled, the secure partitions are loaded + by BL2 on behalf of the SPMC. + +Notes: + +- BL32 option is re-purposed to specify the S-EL1 TEE or SP image. + BL32 option can be omitted if using TF-A Test Secure Payload as SP. +- BL33 option can specify the TFTF binary or a normal world loader + such as U-Boot or the UEFI framework payload. + +Sample TF-A build command line when the SPMC is located at EL3: + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + SPD=spmd \ + SPMD_SPM_AT_SEL2=0 \ + SPMC_AT_EL3=1 \ + BL32=<path-to-tee-binary> (opt for TSP) \ + BL33=<path-to-bl33-binary> \ + PLAT=fvp \ + all fip + +FVP model invocation +==================== + +Sample FVP command line invocation: + +.. code:: shell + + <path-to-fvp-model>/FVP_Base_RevC-2xAEMvA -C pctl.startup=0.0.0.0 \ + -C cluster0.NUM_CORES=4 -C cluster1.NUM_CORES=4 -C bp.secure_memory=1 \ + -C bp.secureflashloader.fname=trusted-firmware-a/build/fvp/debug/bl1.bin \ + -C bp.flashloader0.fname=trusted-firmware-a/build/fvp/debug/fip.bin \ + -C bp.pl011_uart0.out_file=fvp-uart0.log -C bp.pl011_uart1.out_file=fvp-uart1.log \ + -C bp.pl011_uart2.out_file=fvp-uart2.log -C bp.vis.disable_visualisation=1 + + +Platform Guide +============== + +- Platform Hooks See - `[4]`_ + + - plat_spmc_shmem_begin + - plat_spmc_shmem_reclaim + +SPMC provides platform hooks related to memory management interfaces. +These hooks can be used for platform specific implementations like +for managing access control, programming TZ Controller or MPUs. +These hooks are called by SPMC before the initial share request completes, +and after the final reclaim has been completed. + +- Datastore + + - plat_spmc_shmem_datastore_get + + EL3 SPMC uses datastore for tracking memory transaction descriptors. + On FVP platform datastore is allocated from TZC DRAM section. + Other platforms need to allocate a similar secure memory region + to be used as shared memory datastore. + + The accessor function is used during SPMC initialization to obtain + address and size of the datastore. + SPMC will also zero out the provided memory region. + +- Platform Defines See - `[5]`_ + + - SECURE_PARTITION_COUNT + Number of Secure Partitions supported: must be 1. + + - NS_PARTITION_COUNT + Number of NWd Partitions supported. + + - MAX_EL3_LP_DESCS_COUNT + Number of Logical Partitions supported. + +Logical Secure Partition (LSP) +============================== + +- The SPMC provides support for statically allocated EL3 Logical Secure Partitions + as per FF-A v1.1 specification. +- The DECLARE_LOGICAL_PARTITION macro can be used to add a LSP. +- For reference implementation See - `[2]`_ + +.. image:: ../resources/diagrams/ff-a-lsp-at-el3.png + +SPMC boot +========= + +The SPMD and SPMC are built into the BL31 image along with TF-A's runtime components. +BL2 loads the BL31 image as a part of (secure) boot process. + +The SPMC manifest is loaded by BL2 as the ``TOS_FW_CONFIG`` image `[9]`_. + +BL2 passes the SPMC manifest address to BL31 through a register. + +At boot time, the SPMD in BL31 runs from the primary core, initializes the core +contexts and launches the SPMC passing the following information through +registers: + +- X0 holds the SPMC manifest blob address. +- X4 holds the currently running core linear id. + +Parsing SP partition manifests +------------------------------ + +SPMC consumes the SP manifest, as defined in `[7]`_. +SP manifest fields align with Hafnium SP manifest for easy porting. + +.. code:: shell + + compatible = "arm,ffa-manifest-1.0"; + + ffa-version = <0x00010001>; /* 31:16 - Major, 15:0 - Minor */ + id = <0x8001>; + uuid = <0x6b43b460 0x74a24b78 0xade24502 0x40682886>; + messaging-method = <0x3>; /* Direct Messaging Only */ + exception-level = <0x2>; /* S-EL1 */ + execution-state = <0>; + execution-ctx-count = <8>; + gp-register-num = <0>; + power-management-messages = <0x7>; + + +Passing boot data to the SP +--------------------------- + +In `[1]`_ , the section "Boot information protocol" defines a method for passing +data to the SPs at boot time. It specifies the format for the boot information +descriptor and boot information header structures, which describe the data to be +exchanged between SPMC and SP. +The specification also defines the types of data that can be passed. +The aggregate of both the boot info structures and the data itself is designated +the boot information blob, and is passed to a Partition as a contiguous memory +region. + +Currently, the SPM implementation supports the FDT type which is used to pass the +partition's DTB manifest. + +The region for the boot information blob is statically allocated (4K) by SPMC. +BLOB contains Boot Info Header, followed by SP Manifest contents. + +The configuration of the boot protocol is done in the SP manifest. As defined by +the specification, the manifest field 'gp-register-num' configures the GP register +which shall be used to pass the address to the partitions boot information blob when +booting the partition. + +Supported interfaces +==================== + +The following interfaces are exposed to SPs only: + +- ``FFA_MSG_WAIT`` +- ``FFA_MEM_RETRIEVE_REQ`` +- ``FFA_MEM_RETRIEVE_RESP`` +- ``FFA_MEM_RELINQUISH`` +- ``FFA_SECONDARY_EP_REGISTER`` + +The following interfaces are exposed to both NS Client and SPs: + +- ``FFA_VERSION`` +- ``FFA_FEATURES`` +- ``FFA_RX_RELEASE`` +- ``FFA_RXTX_MAP`` +- ``FFA_RXTX_UNMAP`` +- ``FFA_PARTITION_INFO_GET`` +- ``FFA_ID_GET`` +- ``FFA_MSG_SEND_DIRECT_REQ`` +- ``FFA_MSG_SEND_DIRECT_RESP`` +- ``FFA_MEM_FRAG_TX`` +- ``FFA_SPM_ID_GET`` + +The following additional interfaces are forwarded from SPMD to support NS Client: + +- ``FFA_RUN`` +- ``FFA_MEM_LEND`` +- ``FFA_MEM_SHARE`` +- ``FFA_MEM_FRAG_RX`` +- ``FFA_MEM_RECLAIM`` + + +FFA_VERSION +----------- + +``FFA_VERSION`` requires a *requested_version* parameter from the caller. +SPMD forwards call to SPMC, the SPMC returns its own implemented version. +SPMC asserts SP and SPMC are at same FF-A Version. + +FFA_FEATURES +------------ + +FF-A features supported by the SPMC may be discovered by secure partitions at +boot (that is prior to NWd is booted) or run-time. + +The SPMC calling FFA_FEATURES at secure physical FF-A instance always get +FFA_SUCCESS from the SPMD. + +The request made by an Hypervisor or OS kernel is forwarded to the SPMC and +the response relayed back to the NWd. + + +FFA_RXTX_MAP +------------ + +FFA_RXTX_UNMAP +-------------- + +When invoked from a secure partition FFA_RXTX_MAP maps the provided send and +receive buffers described by their PAs to the EL3 translation regime +as secure buffers in the MMU descriptors. + +When invoked from the Hypervisor or OS kernel, the buffers are mapped into the +SPMC EL3 translation regime and marked as NS buffers in the MMU +descriptors. + +The FFA_RXTX_UNMAP unmaps the RX/TX pair from the translation regime of the +caller, either it being the Hypervisor or OS kernel, as well as a secure +partition. + +FFA_PARTITION_INFO_GET +---------------------- + +Partition info get call can originate: + +- from SP to SPMC +- from Hypervisor or OS kernel to SPMC. The request is relayed by the SPMD. + +The format (v1.0 or v1.1) of the populated data structure returned is based upon the +FFA version of the calling entity. + +EL3 SPMC also supports returning only the count of partitions deployed. + +All LSPs and SP are discoverable from FFA_PARTITION_INFO_GET call made by +either SP or NWd entities. + +FFA_ID_GET +---------- + +The FF-A ID space is split into a non-secure space and secure space: + +- FF-A ID with bit 15 clear relates to VMs. +- FF-A ID with bit 15 set related to SPs or LSPs. +- FF-A IDs 0, 0xffff, 0x8000 are assigned respectively to the Hypervisor + (or OS Kernel if Hyp is absent), SPMD and SPMC. + +This convention helps the SPM to determine the origin and destination worlds in +an FF-A ABI invocation. In particular the SPM shall filter unauthorized +transactions in its world switch routine. It must not be permitted for a VM to +use a secure FF-A ID as origin world by spoofing: + +- A VM-to-SP direct request/response shall set the origin world to be non-secure + (FF-A ID bit 15 clear) and destination world to be secure (FF-A ID bit 15 + set). +- Similarly, an SP-to-LSP direct request/response shall set the FF-A ID bit 15 + for both origin and destination IDs. + +An incoming direct message request arriving at SPMD from NWd is forwarded to +SPMC without a specific check. The SPMC is resumed through eret and "knows" the +message is coming from normal world in this specific code path. Thus the origin +endpoint ID must be checked by SPMC for being a normal world ID. + +An SP sending a direct message request must have bit 15 set in its origin +endpoint ID and this can be checked by the SPMC when the SP invokes the ABI. + +The SPMC shall reject the direct message if the claimed world in origin endpoint +ID is not consistent: + +- It is either forwarded by SPMD and thus origin endpoint ID must be a "normal + world ID", +- or initiated by an SP and thus origin endpoint ID must be a "secure world ID". + + +FFA_MSG_SEND_DIRECT_REQ +----------------------- + +FFA_MSG_SEND_DIRECT_RESP +------------------------ + +This is a mandatory interface for secure partitions participating in direct request +and responses with the following rules: + +- An SP can send a direct request to LSP. +- An LSP can send a direct response to SP. +- An SP cannot send a direct request to an Hypervisor or OS kernel. +- An Hypervisor or OS kernel can send a direct request to an SP or LSP. +- An SP and LSP can send a direct response to an Hypervisor or OS kernel. +- SPMD can send direct request to SPMC. + +FFA_SPM_ID_GET +-------------- + +Returns the FF-A ID allocated to an SPM component which can be one of SPMD +or SPMC. + +At initialization, the SPMC queries the SPMD for the SPMC ID, using the +FFA_ID_GET interface, and records it. The SPMC can also query the SPMD ID using +the FFA_SPM_ID_GET interface at the secure physical FF-A instance. + +Secure partitions call this interface at the virtual FF-A instance, to which +the SPMC returns the SPMC ID. + +The Hypervisor or OS kernel can issue the FFA_SPM_ID_GET call handled by the +SPMD, which returns the SPMC ID. + +FFA_ID_GET +---------- + +Returns the FF-A ID of the calling endpoint. + +FFA_MEM_SHARE +------------- + +FFA_MEM_LEND +------------ + +- If SP is borrower in the memory transaction, these calls are forwarded to SPMC. + SPMC performs Relayer responsibilities, caches the memory descriptors in the datastore, + and allocates FF-A memory handle. +- If format of descriptor was v1.0, SPMC converts the descriptor to v1.1 before caching. + In case of fragmented sharing, conversion of memory descriptors happens after last + fragment has been received. +- Multiple borrowers (including NWd endpoint) and fragmented memory sharing are supported. + +FFA_MEM_RETRIEVE_REQ +-------------------- + +FFA_MEM_RETRIEVE_RESP +--------------------- + +- Memory retrieve is supported only from SP. +- SPMC fetches the cached memory descriptor from the datastore, +- Performs Relayer responsiilities and sends FFA_MEM_RETRIEVE_RESP back to SP. +- If descriptor size is more than RX buffer size, SPMC will send the descriptor in fragments. +- SPMC will set NS Bit to 1 in memory descriptor response. + +FFA_MEM_FRAG_RX +--------------- + +FFA_MEM_FRAG_TX +--------------- + +FFA_MEM_FRAG_RX is to be used by: + +- SP if FFA_MEM_RETRIEVE_RESP returned descriptor with fragment length less than total length. +- or by SPMC if FFA_MEM_SHARE/FFA_MEM_LEND is called with fragment length less than total length. + +SPMC validates handle and Endpoint ID and returns response with FFA_MEM_FRAG_TX. + +FFA_SECONDARY_EP_REGISTER +------------------------- + +When the SPMC boots, secure partition is initialized on its primary +Execution Context. + +The FFA_SECONDARY_EP_REGISTER interface is to be used by a secure partition +from its first execution context, to provide the entry point address for +secondary execution contexts. + +A secondary EC is first resumed either upon invocation of PSCI_CPU_ON from +the NWd or by invocation of FFA_RUN. + +Power management +================ + +In platforms with or without secure virtualization: + +- The NWd owns the platform PM policy. +- The Hypervisor or OS kernel is the component initiating PSCI service calls. +- The EL3 PSCI library is in charge of the PM coordination and control + (eventually writing to platform registers). +- While coordinating PM events, the PSCI library calls backs into the Secure + Payload Dispatcher for events the latter has statically registered to. + +When using the SPMD as a Secure Payload Dispatcher: + +- A power management event is relayed through the SPD hook to the SPMC. +- In the current implementation CPU_ON (svc_on_finish), CPU_OFF + (svc_off), CPU_SUSPEND (svc_suspend) and CPU_SUSPEND_RESUME (svc_suspend_finish) + hooks are registered. + +Secure partitions scheduling +============================ + +The FF-A specification `[1]`_ provides two ways to relinquinsh CPU time to +secure partitions. For this a VM (Hypervisor or OS kernel), or SP invokes one of: + +- the FFA_MSG_SEND_DIRECT_REQ interface. +- the FFA_RUN interface. + +Additionally a secure interrupt can pre-empt the normal world execution and give +CPU cycles by transitioning to EL3. + +Partition Runtime State and Model +================================= + +EL3 SPMC implements Partition runtime states are described in v1.1 FF-A specification `[1]`_ + +An SP can be in one of the following state: + +- RT_STATE_WAITING +- RT_STATE_RUNNING +- RT_STATE_PREEMPTED +- RT_STATE_BLOCKED + +An SP will transition to one of the following runtime model when not in waiting state: + +- RT_MODEL_DIR_REQ +- RT_MODEL_RUN +- RT_MODEL_INIT +- RT_MODEL_INTR + +Platform topology +================= + +SPMC only supports a single Pinned MP S-EL1 SP. The *execution-ctx-count* +SP manifest field should match the number of physical PE. + +Interrupt handling +================== + +Secure Interrupt handling +------------------------- + +- SPMC is capable of forwarding Secure interrupt to S-EL1 SP + which has preempted the normal world. +- Interrupt is forwarded to SP using FFA_INTERRUPT interface. +- Interrupt Number is not passed, S-EL1 SP can access the GIC registers directly. +- Upon completion of Interrupt handling SP is expected to return to + SPMC using FFA_MSG_WAIT interface. +- SPMC returns to normal world after interrupt handling is completed. + +In the scenario when secure interrupt occurs while the secure partition is running, +the SPMC is not involved and the handling is implementation defined in the TOS. + +Non-Secure Interrupt handling +----------------------------- + +The 'managed exit' scenario is the responsibility of the TOS and the SPMC is not involved. + +Test Secure Payload (TSP) +========================= + +- TSP provides reference implementation of FF-A programming model. +- TSP has the following support: + + - SP initialization on all CPUs. + - Consuming Power Messages including CPU_ON, CPU_OFF, CPU_SUSPEND, CPU_SUSPEND_RESUME. + - Event Loop to receive Direct Requests. + - Sending Direct Response. + - Memory Sharing helper library. + - Ability to handle secure interrupt (timer). + +TSP Tests in CI +--------------- + +- TSP Tests are exercised in the TF-A CI using prebuilt FF-A Linux Test driver in NWd. +- Expected output: + +.. code:: shell + + #ioctl 255 + Test: Echo Message to SP. + Status: Completed Test Case: 1 + Test Executed Successfully + + Test: Message Relay vis SP to EL3 LSP. + Status: Completed Test Case: 2 + Test Executed Successfully + + Test: Memory Send. + Verified 1 constituents successfully + Status: Completed Test Case: 3 + Test Executed Successfully + + Test: Memory Send in Fragments. + Verified 256 constituents successfully + Status: Completed Test Case: 4 + Test Executed Successfully + + Test: Memory Lend. + Verified 1 constituents successfully + Status: Completed Test Case: 5 + Test Executed Successfully + + Test: Memory Lend in Fragments. + Verified 256 constituents successfully + Status: Completed Test Case: 6 + Test Executed Successfully + + Test: Memory Send with Multiple Endpoints. + random: fast init done + Verified 256 constituents successfully + Status: Completed Test Case: 7 + Test Executed Successfully + + Test: Memory Lend with Multiple Endpoints. + Verified 256 constituents successfully + Status: Completed Test Case: 8 + Test Executed Successfully + + Test: Ensure Duplicate Memory Send Requests are Rejected. + Status: Completed Test Case: 9 + Test Executed Successfully + + Test: Ensure Duplicate Memory Lend Requests are Rejected. + Status: Completed Test Case: 10 + Test Executed Successfully + + 0 Tests Failed + + Exiting Test Application - Total Failures: 0 + + +References +========== + +.. _[1]: + +[1] `Arm Firmware Framework for Arm A-profile <https://developer.arm.com/docs/den0077/latest>`__ + +.. _[2]: + +[2] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/plat/arm/board/fvp/fvp_el3_spmc_logical_sp.c + +.. _[3]: + +[3] `Trusted Boot Board Requirements +Client <https://developer.arm.com/documentation/den0006/d/>`__ + +.. _[4]: + +[4] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/plat/arm/board/fvp/fvp_el3_spmc.c + +.. _[5]: + +[5] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/plat/arm/board/fvp/include/platform_def.h + +.. _[6]: + +[6] https://trustedfirmware-a.readthedocs.io/en/latest/components/ffa-manifest-binding.html + +.. _[7]: + +[7] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/plat/arm/board/fvp/fdts/fvp_tsp_sp_manifest.dts + +.. _[8]: + +[8] https://lists.trustedfirmware.org/archives/list/tf-a@lists.trustedfirmware.org/thread/CFQFGU6H2D5GZYMUYGTGUSXIU3OYZP6U/ + +.. _[9]: + +[9] https://trustedfirmware-a.readthedocs.io/en/latest/design/firmware-design.html#dynamic-configuration-during-cold-boot + +-------------- + +*Copyright (c) 2020-2022, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/exception-handling.rst b/docs/components/exception-handling.rst new file mode 100644 index 0000000..6f223c6 --- /dev/null +++ b/docs/components/exception-handling.rst @@ -0,0 +1,619 @@ +Exception Handling Framework +============================ + +This document describes various aspects of handling exceptions by Runtime +Firmware (BL31) that are targeted at EL3, other than SMCs. The |EHF| takes care +of the following exceptions when targeted at EL3: + +- Interrupts +- Synchronous External Aborts +- Asynchronous External Aborts + +|TF-A|'s handling of synchronous ``SMC`` exceptions raised from lower ELs is +described in the :ref:`Firmware Design document <handling-an-smc>`. However, the +|EHF| changes the semantics of `Interrupt handling`_ and :ref:`synchronous +exceptions <Effect on SMC calls>` other than SMCs. + +The |EHF| is selected by setting the build option ``EL3_EXCEPTION_HANDLING`` to +``1``, and is only available for AArch64 systems. + +Introduction +------------ + +Through various control bits in the ``SCR_EL3`` register, the Arm architecture +allows for asynchronous exceptions to be routed to EL3. As described in the +:ref:`Interrupt Management Framework` document, depending on the chosen +interrupt routing model, TF-A appropriately sets the ``FIQ`` and ``IRQ`` bits of +``SCR_EL3`` register to effect this routing. For most use cases, other than for +the purpose of facilitating context switch between Normal and Secure worlds, +FIQs and IRQs routed to EL3 are not required to be handled in EL3. + +However, the evolving system and standards landscape demands that various +exceptions are targeted at and handled in EL3. For instance: + +- Starting with ARMv8.2 architecture extension, many RAS features have been + introduced to the Arm architecture. With RAS features implemented, various + components of the system may use one of the asynchronous exceptions to signal + error conditions to PEs. These error conditions are of critical nature, and + it's imperative that corrective or remedial actions are taken at the earliest + opportunity. Therefore, a *Firmware-first Handling* approach is generally + followed in response to RAS events in the system. + +- The Arm `SDEI specification`_ defines interfaces through which Normal world + interacts with the Runtime Firmware in order to request notification of + system events. The |SDEI| specification requires that these events are + notified even when the Normal world executes with the exceptions masked. This + too implies that firmware-first handling is required, where the events are + first received by the EL3 firmware, and then dispatched to Normal world + through purely software mechanism. + +For |TF-A|, firmware-first handling means that asynchronous exceptions are +suitably routed to EL3, and the Runtime Firmware (BL31) is extended to include +software components that are capable of handling those exceptions that target +EL3. These components—referred to as *dispatchers* [#spd]_ in general—may +choose to: + +.. _delegation-use-cases: + +- Receive and handle exceptions entirely in EL3, meaning the exceptions + handling terminates in EL3. + +- Receive exceptions, but handle part of the exception in EL3, and delegate the + rest of the handling to a dedicated software stack running at lower Secure + ELs. In this scheme, the handling spans various secure ELs. + +- Receive exceptions, but handle part of the exception in EL3, and delegate + processing of the error to dedicated software stack running at lower secure + ELs (as above); additionally, the Normal world may also be required to + participate in the handling, or be notified of such events (for example, as + an |SDEI| event). In this scheme, exception handling potentially and + maximally spans all ELs in both Secure and Normal worlds. + +On any given system, all of the above handling models may be employed +independently depending on platform choice and the nature of the exception +received. + +.. [#spd] Not to be confused with :ref:`Secure Payload Dispatcher + <firmware_design_sel1_spd>`, which is an EL3 component that operates in EL3 + on behalf of Secure OS. + +The role of Exception Handling Framework +---------------------------------------- + +Corollary to the use cases cited above, the primary role of the |EHF| is to +facilitate firmware-first handling of exceptions on Arm systems. The |EHF| thus +enables multiple exception dispatchers in runtime firmware to co-exist, register +for, and handle exceptions targeted at EL3. This section outlines the basics, +and the rest of this document expands the various aspects of the |EHF|. + +In order to arbitrate exception handling among dispatchers, the |EHF| operation +is based on a priority scheme. This priority scheme is closely tied to how the +Arm GIC architecture defines it, although it's applied to non-interrupt +exceptions too (SErrors, for example). + +The platform is required to `partition`__ the Secure priority space into +priority levels as applicable for the Secure software stack. It then assigns the +dispatchers to one or more priority levels. The dispatchers then register +handlers for the priority levels at runtime. A dispatcher can register handlers +for more than one priority level. + +.. __: `Partitioning priority levels`_ + + +.. _ehf-figure: + +.. image:: ../resources/diagrams/draw.io/ehf.svg + +A priority level is *active* when a handler at that priority level is currently +executing in EL3, or has delegated the execution to a lower EL. For interrupts, +this is implicit when an interrupt is targeted and acknowledged at EL3, and the +priority of the acknowledged interrupt is used to match its registered handler. +The priority level is likewise implicitly deactivated when the interrupt +handling concludes by EOIing the interrupt. + +Non-interrupt exceptions (SErrors, for example) don't have a notion of priority. +In order for the priority arbitration to work, the |EHF| provides APIs in order +for these non-interrupt exceptions to assume a priority, and to interwork with +interrupts. Dispatchers handling such exceptions must therefore explicitly +activate and deactivate the respective priority level as and when they're +handled or delegated. + +Because priority activation and deactivation for interrupt handling is implicit +and involves GIC priority masking, it's impossible for a lower priority +interrupt to preempt a higher priority one. By extension, this means that a +lower priority dispatcher cannot preempt a higher-priority one. Priority +activation and deactivation for non-interrupt exceptions, however, has to be +explicit. The |EHF| therefore disallows for lower priority level to be activated +whilst a higher priority level is active, and would result in a panic. +Likewise, a panic would result if it's attempted to deactivate a lower priority +level when a higher priority level is active. + +In essence, priority level activation and deactivation conceptually works like a +stack—priority levels stack up in strictly increasing fashion, and need to be +unstacked in strictly the reverse order. For interrupts, the GIC ensures this is +the case; for non-interrupts, the |EHF| monitors and asserts this. See +`Transition of priority levels`_. + +.. _interrupt-handling: + +Interrupt handling +------------------ + +The |EHF| is a client of *Interrupt Management Framework*, and registers the +top-level handler for interrupts that target EL3, as described in the +:ref:`Interrupt Management Framework` document. This has the following +implications: + +- On GICv3 systems, when executing in S-EL1, pending Non-secure interrupts of + sufficient priority are signalled as FIQs, and therefore will be routed to + EL3. As a result, S-EL1 software cannot expect to handle Non-secure + interrupts at S-EL1. Essentially, this deprecates the routing mode described + as :ref:`CSS=0, TEL3=0 <EL3 interrupts>`. + + In order for S-EL1 software to handle Non-secure interrupts while having + |EHF| enabled, the dispatcher must adopt a model where Non-secure interrupts + are received at EL3, but are then :ref:`synchronously <sp-synchronous-int>` + handled over to S-EL1. + +- On GICv2 systems, it's required that the build option ``GICV2_G0_FOR_EL3`` is + set to ``1`` so that *Group 0* interrupts target EL3. + +- While executing in Secure world, |EHF| sets GIC Priority Mask Register to the + lowest Secure priority. This means that no Non-secure interrupts can preempt + Secure execution. See `Effect on SMC calls`_ for more details. + +As mentioned above, with |EHF|, the platform is required to partition *Group 0* +interrupts into distinct priority levels. A dispatcher that chooses to receive +interrupts can then *own* one or more priority levels, and register interrupt +handlers for them. A given priority level can be assigned to only one handler. A +dispatcher may register more than one priority level. + +Dispatchers are assigned interrupt priority levels in two steps: + +.. _Partitioning priority levels: + +Partitioning priority levels +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Interrupts are associated to dispatchers by way of grouping and assigning +interrupts to a priority level. In other words, all interrupts that are to +target a particular dispatcher should fall in a particular priority level. For +priority assignment: + +- Of the 8 bits of priority that Arm GIC architecture permits, bit 7 must be 0 + (secure space). + +- Depending on the number of dispatchers to support, the platform must choose + to use the top *n* of the 7 remaining bits to identify and assign interrupts + to individual dispatchers. Choosing *n* bits supports up to 2\ :sup:`n` + distinct dispatchers. For example, by choosing 2 additional bits (i.e., bits + 6 and 5), the platform can partition into 4 secure priority ranges: ``0x0``, + ``0x20``, ``0x40``, and ``0x60``. See `Interrupt handling example`_. + +.. note:: + + The Arm GIC architecture requires that a GIC implementation that supports two + security states must implement at least 32 priority levels; i.e., at least 5 + upper bits of the 8 bits are writeable. In the scheme described above, when + choosing *n* bits for priority range assignment, the platform must ensure + that at least ``n+1`` top bits of GIC priority are writeable. + +The priority thus assigned to an interrupt is also used to determine the +priority of delegated execution in lower ELs. Delegated execution in lower EL is +associated with a priority level chosen with ``ehf_activate_priority()`` API +(described `later`__). The chosen priority level also determines the interrupts +masked while executing in a lower EL, therefore controls preemption of delegated +execution. + +.. __: `ehf-apis`_ + +The platform expresses the chosen priority levels by declaring an array of +priority level descriptors. Each entry in the array is of type +``ehf_pri_desc_t``, and declares a priority level, and shall be populated by the +``EHF_PRI_DESC()`` macro. + +.. warning:: + + The macro ``EHF_PRI_DESC()`` installs the descriptors in the array at a + computed index, and not necessarily where the macro is placed in the array. + The size of the array might therefore be larger than what it appears to be. + The ``ARRAY_SIZE()`` macro therefore should be used to determine the size of + array. + +Finally, this array of descriptors is exposed to |EHF| via the +``EHF_REGISTER_PRIORITIES()`` macro. + +Refer to the `Interrupt handling example`_ for usage. See also: `Interrupt +Prioritisation Considerations`_. + +Programming priority +~~~~~~~~~~~~~~~~~~~~ + +The text in `Partitioning priority levels`_ only describes how the platform +expresses the required levels of priority. It however doesn't choose interrupts +nor program the required priority in GIC. + +The :ref:`Firmware Design guide<configuring-secure-interrupts>` explains methods +for configuring secure interrupts. |EHF| requires the platform to enumerate +interrupt properties (as opposed to just numbers) of Secure interrupts. The +priority of secure interrupts must match that as determined in the +`Partitioning priority levels`_ section above. + +See `Limitations`_, and also refer to `Interrupt handling example`_ for +illustration. + +Registering handler +------------------- + +Dispatchers register handlers for their priority levels through the following +API: + +.. code:: c + + int ehf_register_priority_handler(int pri, ehf_handler_t handler) + +The API takes two arguments: + +- The priority level for which the handler is being registered; + +- The handler to be registered. The handler must be aligned to 4 bytes. + +If a dispatcher owns more than one priority levels, it has to call the API for +each of them. + +The API will succeed, and return ``0``, only if: + +- There exists a descriptor with the priority level requested. + +- There are no handlers already registered by a previous call to the API. + +Otherwise, the API returns ``-1``. + +The interrupt handler should have the following signature: + +.. code:: c + + typedef int (*ehf_handler_t)(uint32_t intr_raw, uint32_t flags, void *handle, + void *cookie); + +The parameters are as obtained from the top-level :ref:`EL3 interrupt handler +<el3-runtime-firmware>`. + +The :ref:`SDEI dispatcher<SDEI: Software Delegated Exception Interface>`, for +example, expects the platform to allocate two different priority levels— +``PLAT_SDEI_CRITICAL_PRI``, and ``PLAT_SDEI_NORMAL_PRI`` —and registers the +same handler to handle both levels. + +Interrupt handling example +-------------------------- + +The following annotated snippet demonstrates how a platform might choose to +assign interrupts to fictitious dispatchers: + +.. code:: c + + #include <common/interrupt_props.h> + #include <drivers/arm/gic_common.h> + #include <exception_mgmt.h> + + ... + + /* + * This platform uses 2 bits for interrupt association. In total, 3 upper + * bits are in use. + * + * 7 6 5 3 0 + * .-.-.-.----------. + * |0|b|b| ..0.. | + * '-'-'-'----------' + */ + #define PLAT_PRI_BITS 2 + + /* Priorities for individual dispatchers */ + #define DISP0_PRIO 0x00 /* Not used */ + #define DISP1_PRIO 0x20 + #define DISP2_PRIO 0x40 + #define DISP3_PRIO 0x60 + + /* Install priority level descriptors for each dispatcher */ + ehf_pri_desc_t plat_exceptions[] = { + EHF_PRI_DESC(PLAT_PRI_BITS, DISP1_PRIO), + EHF_PRI_DESC(PLAT_PRI_BITS, DISP2_PRIO), + EHF_PRI_DESC(PLAT_PRI_BITS, DISP3_PRIO), + }; + + /* Expose priority descriptors to Exception Handling Framework */ + EHF_REGISTER_PRIORITIES(plat_exceptions, ARRAY_SIZE(plat_exceptions), + PLAT_PRI_BITS); + + ... + + /* List interrupt properties for GIC driver. All interrupts target EL3 */ + const interrupt_prop_t plat_interrupts[] = { + /* Dispatcher 1 owns interrupts d1_0 and d1_1, so assigns priority DISP1_PRIO */ + INTR_PROP_DESC(d1_0, DISP1_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + INTR_PROP_DESC(d1_1, DISP1_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + + /* Dispatcher 2 owns interrupts d2_0 and d2_1, so assigns priority DISP2_PRIO */ + INTR_PROP_DESC(d2_0, DISP2_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + INTR_PROP_DESC(d2_1, DISP2_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + + /* Dispatcher 3 owns interrupts d3_0 and d3_1, so assigns priority DISP3_PRIO */ + INTR_PROP_DESC(d3_0, DISP3_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + INTR_PROP_DESC(d3_1, DISP3_PRIO, INTR_TYPE_EL3, GIC_INTR_CFG_LEVEL), + }; + + ... + + /* Dispatcher 1 registers its handler */ + ehf_register_priority_handler(DISP1_PRIO, disp1_handler); + + /* Dispatcher 2 registers its handler */ + ehf_register_priority_handler(DISP2_PRIO, disp2_handler); + + /* Dispatcher 3 registers its handler */ + ehf_register_priority_handler(DISP3_PRIO, disp3_handler); + + ... + +See also the `Build-time flow`_ and the `Run-time flow`_. + +.. _Activating and Deactivating priorities: + +Activating and Deactivating priorities +-------------------------------------- + +A priority level is said to be *active* when an exception of that priority is +being handled: for interrupts, this is implied when the interrupt is +acknowledged; for non-interrupt exceptions, such as SErrors or :ref:`SDEI +explicit dispatches <explicit-dispatch-of-events>`, this has to be done via +calling ``ehf_activate_priority()``. See `Run-time flow`_. + +Conversely, when the dispatcher has reached a logical resolution for the cause +of the exception, the corresponding priority level ought to be deactivated. As +above, for interrupts, this is implied when the interrupt is EOId in the GIC; +for other exceptions, this has to be done via calling +``ehf_deactivate_priority()``. + +Thanks to `different provisions`__ for exception delegation, there are +potentially more than one work flow for deactivation: + +.. __: `delegation-use-cases`_ + +.. _deactivation workflows: + +- The dispatcher has addressed the cause of the exception, and decided to take + no further action. In this case, the dispatcher's handler deactivates the + priority level before returning to the |EHF|. Runtime firmware, upon exit + through an ``ERET``, resumes execution before the interrupt occurred. + +- The dispatcher has to delegate the execution to lower ELs, and the cause of + the exception can be considered resolved only when the lower EL returns + signals complete (via an ``SMC``) at a future point in time. The following + sequence ensues: + + #. The dispatcher calls ``setjmp()`` to setup a jump point, and arranges to + enter a lower EL upon the next ``ERET``. + + #. Through the ensuing ``ERET`` from runtime firmware, execution is delegated + to a lower EL. + + #. The lower EL completes its execution, and signals completion via an + ``SMC``. + + #. The ``SMC`` is handled by the same dispatcher that handled the exception + previously. Noticing the conclusion of exception handling, the dispatcher + does ``longjmp()`` to resume beyond the previous jump point. + +As mentioned above, the |EHF| provides the following APIs for activating and +deactivating interrupt: + +.. _ehf-apis: + +- ``ehf_activate_priority()`` activates the supplied priority level, but only + if the current active priority is higher than the given one; otherwise + panics. Also, to prevent interruption by physical interrupts of lower + priority, the |EHF| programs the *Priority Mask Register* corresponding to + the PE to the priority being activated. Dispatchers typically only need to + call this when handling exceptions other than interrupts, and it needs to + delegate execution to a lower EL at a desired priority level. + +- ``ehf_deactivate_priority()`` deactivates a given priority, but only if the + current active priority is equal to the given one; otherwise panics. |EHF| + also restores the *Priority Mask Register* corresponding to the PE to the + priority before the call to ``ehf_activate_priority()``. Dispatchers + typically only need to call this after handling exceptions other than + interrupts. + +The calling of APIs are subject to allowed `transitions`__. See also the +`Run-time flow`_. + +.. __: `Transition of priority levels`_ + +Transition of priority levels +----------------------------- + +The |EHF| APIs ``ehf_activate_priority()`` and ``ehf_deactivate_priority()`` can +be called to transition the current priority level on a PE. A given sequence of +calls to these APIs are subject to the following conditions: + +- For activation, the |EHF| only allows for the priority to increase (i.e. + numeric value decreases); + +- For deactivation, the |EHF| only allows for the priority to decrease (i.e. + numeric value increases). Additionally, the priority being deactivated is + required to be the current priority. + +If these are violated, a panic will result. + +.. _Effect on SMC calls: + +Effect on SMC calls +------------------- + +In general, Secure execution is regarded as more important than Non-secure +execution. As discussed elsewhere in this document, EL3 execution, and any +delegated execution thereafter, has the effect of raising GIC's priority +mask—either implicitly by acknowledging Secure interrupts, or when dispatchers +call ``ehf_activate_priority()``. As a result, Non-secure interrupts cannot +preempt any Secure execution. + +SMCs from Non-secure world are synchronous exceptions, and are mechanisms for +Non-secure world to request Secure services. They're broadly classified as +*Fast* or *Yielding* (see `SMCCC`__). + +.. __: https://developer.arm.com/docs/den0028/latest + +- *Fast* SMCs are atomic from the caller's point of view. I.e., they return + to the caller only when the Secure world has finished serving the request. + Any Non-secure interrupts that become pending meanwhile cannot preempt Secure + execution. + +- *Yielding* SMCs carry the semantics of a preemptible, lower-priority request. + A pending Non-secure interrupt can preempt Secure execution handling a + Yielding SMC. I.e., the caller might observe a Yielding SMC returning when + either: + + #. Secure world completes the request, and the caller would find ``SMC_OK`` + as the return code. + + #. A Non-secure interrupt preempts Secure execution. Non-secure interrupt is + handled, and Non-secure execution resumes after ``SMC`` instruction. + + The dispatcher handling a Yielding SMC must provide a different return code + to the Non-secure caller to distinguish the latter case. This return code, + however, is not standardised (unlike ``SMC_UNKNOWN`` or ``SMC_OK``, for + example), so will vary across dispatchers that handle the request. + +For the latter case above, dispatchers before |EHF| expect Non-secure interrupts +to be taken to S-EL1 [#irq]_, so would get a chance to populate the designated +preempted error code before yielding to Non-secure world. + +The introduction of |EHF| changes the behaviour as described in `Interrupt +handling`_. + +When |EHF| is enabled, in order to allow Non-secure interrupts to preempt +Yielding SMC handling, the dispatcher must call ``ehf_allow_ns_preemption()`` +API. The API takes one argument, the error code to be returned to the Non-secure +world upon getting preempted. + +.. [#irq] In case of GICv2, Non-secure interrupts while in S-EL1 were signalled + as IRQs, and in case of GICv3, FIQs. + +Build-time flow +--------------- + +Please refer to the `figure`__ above. + +.. __: `ehf-figure`_ + +The build-time flow involves the following steps: + +#. Platform assigns priorities by installing priority level descriptors for + individual dispatchers, as described in `Partitioning priority levels`_. + +#. Platform provides interrupt properties to GIC driver, as described in + `Programming priority`_. + +#. Dispatcher calling ``ehf_register_priority_handler()`` to register an + interrupt handler. + +Also refer to the `Interrupt handling example`_. + +Run-time flow +------------- + +.. _interrupt-flow: + +The following is an example flow for interrupts: + +#. The GIC driver, during initialization, iterates through the platform-supplied + interrupt properties (see `Programming priority`_), and configures the + interrupts. This programs the appropriate priority and group (Group 0) on + interrupts belonging to different dispatchers. + +#. The |EHF|, during its initialisation, registers a top-level interrupt handler + with the :ref:`Interrupt Management Framework<el3-runtime-firmware>` for EL3 + interrupts. This also results in setting the routing bits in ``SCR_EL3``. + +#. When an interrupt belonging to a dispatcher fires, GIC raises an EL3/Group 0 + interrupt, and is taken to EL3. + +#. The top-level EL3 interrupt handler executes. The handler acknowledges the + interrupt, reads its *Running Priority*, and from that, determines the + dispatcher handler. + +#. The |EHF| programs the *Priority Mask Register* of the PE to the priority of + the interrupt received. + +#. The |EHF| marks that priority level *active*, and jumps to the dispatcher + handler. + +#. Once the dispatcher handler finishes its job, it has to immediately + *deactivate* the priority level before returning to the |EHF|. See + `deactivation workflows`_. + +.. _non-interrupt-flow: + +The following is an example flow for exceptions that targets EL3 other than +interrupt: + +#. The platform provides handlers for the specific kind of exception. + +#. The exception arrives, and the corresponding handler is executed. + +#. The handler calls ``ehf_activate_priority()`` to activate the required + priority level. This also has the effect of raising GIC priority mask, thus + preventing interrupts of lower priority from preempting the handling. The + handler may choose to do the handling entirely in EL3 or delegate to a lower + EL. + +#. Once exception handling concludes, the handler calls + ``ehf_deactivate_priority()`` to deactivate the priority level activated + earlier. This also has the effect of lowering GIC priority mask to what it + was before. + +Interrupt Prioritisation Considerations +--------------------------------------- + +The GIC priority scheme, by design, prioritises Secure interrupts over Normal +world ones. The platform further assigns relative priorities amongst Secure +dispatchers through |EHF|. + +As mentioned in `Partitioning priority levels`_, interrupts targeting distinct +dispatchers fall in distinct priority levels. Because they're routed via the +GIC, interrupt delivery to the PE is subject to GIC prioritisation rules. In +particular, when an interrupt is being handled by the PE (i.e., the interrupt is +in *Active* state), only interrupts of higher priority are signalled to the PE, +even if interrupts of same or lower priority are pending. This has the side +effect of one dispatcher being starved of interrupts by virtue of another +dispatcher handling its (higher priority) interrupts. + +The |EHF| doesn't enforce a particular prioritisation policy, but the platform +should carefully consider the assignment of priorities to dispatchers integrated +into runtime firmware. The platform should sensibly delineate priority to +various dispatchers according to their nature. In particular, dispatchers of +critical nature (RAS, for example) should be assigned higher priority than +others (|SDEI|, for example); and within |SDEI|, Critical priority +|SDEI| should be assigned higher priority than Normal ones. + +Limitations +----------- + +The |EHF| has the following limitations: + +- Although there could be up to 128 Secure dispatchers supported by the GIC + priority scheme, the size of descriptor array exposed with + ``EHF_REGISTER_PRIORITIES()`` macro is currently limited to 32. This serves most + expected use cases. This may be expanded in the future, should use cases + demand so. + +- The platform must ensure that the priority assigned to the dispatcher in the + exception descriptor and the programmed priority of interrupts handled by the + dispatcher match. The |EHF| cannot verify that this has been followed. + +-------------- + +*Copyright (c) 2018-2020, Arm Limited and Contributors. All rights reserved.* + +.. _SDEI specification: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf diff --git a/docs/components/fconf/amu-bindings.rst b/docs/components/fconf/amu-bindings.rst new file mode 100644 index 0000000..047f75e --- /dev/null +++ b/docs/components/fconf/amu-bindings.rst @@ -0,0 +1,142 @@ +Activity Monitor Unit (AMU) Bindings +==================================== + +To support platform-defined Activity Monitor Unit (|AMU|) auxiliary counters +through FCONF, the ``HW_CONFIG`` device tree accepts several |AMU|-specific +nodes and properties. + +Bindings +^^^^^^^^ + +.. contents:: + :local: + +``/cpus/cpus/cpu*`` node properties +""""""""""""""""""""""""""""""""""" + +The ``cpu`` node has been augmented to support a handle to an associated |AMU| +view, which should describe the counters offered by the core. + ++---------------+-------+---------------+-------------------------------------+ +| Property name | Usage | Value type | Description | ++===============+=======+===============+=====================================+ +| ``amu`` | O | ``<phandle>`` | If present, indicates that an |AMU| | +| | | | is available and its counters are | +| | | | described by the node provided. | ++---------------+-------+---------------+-------------------------------------+ + +``/cpus/amus`` node properties +"""""""""""""""""""""""""""""" + +The ``amus`` node describes the |AMUs| implemented by the cores in the system. +This node does not have any properties. + +``/cpus/amus/amu*`` node properties +""""""""""""""""""""""""""""""""""" + +An ``amu`` node describes the layout and meaning of the auxiliary counter +registers of one or more |AMUs|, and may be shared by multiple cores. + ++--------------------+-------+------------+------------------------------------+ +| Property name | Usage | Value type | Description | ++====================+=======+============+====================================+ +| ``#address-cells`` | R | ``<u32>`` | Value shall be 1. Specifies that | +| | | | the ``reg`` property array of | +| | | | children of this node uses a | +| | | | single cell. | ++--------------------+-------+------------+------------------------------------+ +| ``#size-cells`` | R | ``<u32>`` | Value shall be 0. Specifies that | +| | | | no size is required in the ``reg`` | +| | | | property in children of this node. | ++--------------------+-------+------------+------------------------------------+ + +``/cpus/amus/amu*/counter*`` node properties +"""""""""""""""""""""""""""""""""""""""""""" + +A ``counter`` node describes an auxiliary counter belonging to the parent |AMU| +view. + ++-------------------+-------+-------------+------------------------------------+ +| Property name | Usage | Value type | Description | ++===================+=======+=============+====================================+ +| ``reg`` | R | array | Represents the counter register | +| | | | index, and must be a single cell. | ++-------------------+-------+-------------+------------------------------------+ +| ``enable-at-el3`` | O | ``<empty>`` | The presence of this property | +| | | | indicates that this counter should | +| | | | be enabled prior to EL3 exit. | ++-------------------+-------+-------------+------------------------------------+ + +Example +^^^^^^^ + +An example system offering four cores made up of two clusters, where the cores +of each cluster share different |AMUs|, may use something like the following: + +.. code-block:: + + cpus { + #address-cells = <2>; + #size-cells = <0>; + + amus { + amu0: amu-0 { + #address-cells = <1>; + #size-cells = <0>; + + counterX: counter@0 { + reg = <0>; + + enable-at-el3; + }; + + counterY: counter@1 { + reg = <1>; + + enable-at-el3; + }; + }; + + amu1: amu-1 { + #address-cells = <1>; + #size-cells = <0>; + + counterZ: counter@0 { + reg = <0>; + + enable-at-el3; + }; + }; + }; + + cpu0@00000 { + ... + + amu = <&amu0>; + }; + + cpu1@00100 { + ... + + amu = <&amu0>; + }; + + cpu2@10000 { + ... + + amu = <&amu1>; + }; + + cpu3@10100 { + ... + + amu = <&amu1>; + }; + } + +In this situation, ``cpu0`` and ``cpu1`` (the two cores in the first cluster), +share the view of their AMUs defined by ``amu0``. Likewise, ``cpu2`` and +``cpu3`` (the two cores in the second cluster), share the view of their |AMUs| +defined by ``amu1``. This will cause ``counterX`` and ``counterY`` to be enabled +for both ``cpu0`` and ``cpu1``, and ``counterZ`` to be enabled for both ``cpu2`` +and ``cpu3``. diff --git a/docs/components/fconf/fconf_properties.rst b/docs/components/fconf/fconf_properties.rst new file mode 100644 index 0000000..3479576 --- /dev/null +++ b/docs/components/fconf/fconf_properties.rst @@ -0,0 +1,42 @@ +DTB binding for FCONF properties +================================ + +This document describes the device tree format of |FCONF| properties. These +properties are not related to a specific platform and can be queried from +common code. + +Dynamic configuration +~~~~~~~~~~~~~~~~~~~~~ + +The |FCONF| framework expects a *dtb-registry* node with the following field: + +- compatible [mandatory] + - value type: <string> + - Must be the string "fconf,dyn_cfg-dtb_registry". + +Then a list of subnodes representing a configuration |DTB|, which can be used +by |FCONF|. Each subnode should be named according to the information it +contains, and must be formed with the following fields: + +- load-address [mandatory] + - value type: <u64> + - Physical loading base address of the configuration. + If secondary-load-address is also provided (see below), then this is the + primary load address. + +- max-size [mandatory] + - value type: <u32> + - Maximum size of the configuration. + +- id [mandatory] + - value type: <u32> + - Image ID of the configuration. + +- secondary-load-address [optional] + - value type: <u64> + - A platform uses this physical address to copy the configuration to + another location during the boot-flow. + +-------------- + +*Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/fconf/index.rst b/docs/components/fconf/index.rst new file mode 100644 index 0000000..029f324 --- /dev/null +++ b/docs/components/fconf/index.rst @@ -0,0 +1,149 @@ +Firmware Configuration Framework +================================ + +This document provides an overview of the |FCONF| framework. + +Introduction +~~~~~~~~~~~~ + +The Firmware CONfiguration Framework (|FCONF|) is an abstraction layer for +platform specific data, allowing a "property" to be queried and a value +retrieved without the requesting entity knowing what backing store is being used +to hold the data. + +It is used to bridge new and old ways of providing platform-specific data. +Today, information like the Chain of Trust is held within several, nested +platform-defined tables. In the future, it may be provided as part of a device +blob, along with the rest of the information about images to load. +Introducing this abstraction layer will make migration easier and will preserve +functionality for platforms that cannot / don't want to use device tree. + +Accessing properties +~~~~~~~~~~~~~~~~~~~~ + +Properties defined in the |FCONF| are grouped around namespaces and +sub-namespaces: a.b.property. +Examples namespace can be: + +- (|TBBR|) Chain of Trust data: tbbr.cot.trusted_boot_fw_cert +- (|TBBR|) dynamic configuration info: tbbr.dyn_config.disable_auth +- Arm io policies: arm.io_policies.bl2_image +- GICv3 properties: hw_config.gicv3_config.gicr_base + +Properties can be accessed with the ``FCONF_GET_PROPERTY(a,b,property)`` macro. + +Defining properties +~~~~~~~~~~~~~~~~~~~ + +Properties composing the |FCONF| have to be stored in C structures. If +properties originate from a different backend source such as a device tree, +then the platform has to provide a ``populate()`` function which essentially +captures the property and stores them into a corresponding |FCONF| based C +structure. + +Such a ``populate()`` function is usually platform specific and is associated +with a specific backend source. For example, a populator function which +captures the hardware topology of the platform from the HW_CONFIG device tree. +Hence each ``populate()`` function must be registered with a specific +``config_type`` identifier. It broadly represents a logical grouping of +configuration properties which is usually a device tree file. + +Example: + - FW_CONFIG: properties related to base address, maximum size and image id + of other DTBs etc. + - TB_FW: properties related to trusted firmware such as IO policies, + mbedtls heap info etc. + - HW_CONFIG: properties related to hardware configuration of the SoC + such as topology, GIC controller, PSCI hooks, CPU ID etc. + +Hence the ``populate()`` callback must be registered to the (|FCONF|) framework +with the ``FCONF_REGISTER_POPULATOR()`` macro. This ensures that the function +would be called inside the generic ``fconf_populate()`` function during +initialization. + +:: + + int fconf_populate_topology(uintptr_t config) + { + /* read hw config dtb and fill soc_topology struct */ + } + + FCONF_REGISTER_POPULATOR(HW_CONFIG, topology, fconf_populate_topology); + +Then, a wrapper has to be provided to match the ``FCONF_GET_PROPERTY()`` macro: + +:: + + /* generic getter */ + #define FCONF_GET_PROPERTY(a,b,property) a##__##b##_getter(property) + + /* my specific getter */ + #define hw_config__topology_getter(prop) soc_topology.prop + +This second level wrapper can be used to remap the ``FCONF_GET_PROPERTY()`` to +anything appropriate: structure, array, function, etc.. + +To ensure a good interpretation of the properties, this documentation must +explain how the properties are described for a specific backend. Refer to the +:ref:`binding-document` section for more information and example. + +Loading the property device tree +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``fconf_load_config(image_id)`` must be called to load fw_config and +tb_fw_config devices tree containing the properties' values. This must be done +after the io layer is initialized, as the |DTB| is stored on an external +device (FIP). + +.. uml:: ../../resources/diagrams/plantuml/fconf_bl1_load_config.puml + +Populating the properties +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Once a valid device tree is available, the ``fconf_populate(config)`` function +can be used to fill the C data structure with the data from the config |DTB|. +This function will call all the ``populate()`` callbacks which have been +registered with ``FCONF_REGISTER_POPULATOR()`` as described above. + +.. uml:: ../../resources/diagrams/plantuml/fconf_bl2_populate.puml + +Namespace guidance +~~~~~~~~~~~~~~~~~~ + +As mentioned above, properties are logically grouped around namespaces and +sub-namespaces. The following concepts should be considered when adding new +properties/namespaces. +The framework differentiates two types of properties: + + - Properties used inside common code. + - Properties used inside platform specific code. + +The first category applies to properties being part of the firmware and shared +across multiple platforms. They should be globally accessible and defined +inside the ``lib/fconf`` directory. The namespace must be chosen to reflect the +feature/data abstracted. + +Example: + - |TBBR| related properties: tbbr.cot.bl2_id + - Dynamic configuration information: dyn_cfg.dtb_info.hw_config_id + +The second category should represent the majority of the properties defined +within the framework: Platform specific properties. They must be accessed only +within the platform API and are defined only inside the platform scope. The +namespace must contain the platform name under which the properties defined +belong. + +Example: + - Arm io framework: arm.io_policies.bl31_id + +.. _binding-document: + +Properties binding information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. toctree:: + :maxdepth: 1 + + fconf_properties + amu-bindings + mpmm-bindings diff --git a/docs/components/fconf/mpmm-bindings.rst b/docs/components/fconf/mpmm-bindings.rst new file mode 100644 index 0000000..d3cc857 --- /dev/null +++ b/docs/components/fconf/mpmm-bindings.rst @@ -0,0 +1,48 @@ +Maximum Power Mitigation Mechanism (MPMM) Bindings +================================================== + +|MPMM| support cannot be determined at runtime by the firmware. Instead, these +DTB bindings allow the platform to communicate per-core support for |MPMM| via +the ``HW_CONFIG`` device tree blob. + +Bindings +^^^^^^^^ + +.. contents:: + :local: + +``/cpus/cpus/cpu*`` node properties +""""""""""""""""""""""""""""""""""" + +The ``cpu`` node has been augmented to allow the platform to indicate support +for |MPMM| on a given core. + ++-------------------+-------+-------------+------------------------------------+ +| Property name | Usage | Value type | Description | ++===================+=======+=============+====================================+ +| ``supports-mpmm`` | O | ``<empty>`` | If present, indicates that |MPMM| | +| | | | is available on this core. | ++-------------------+-------+-------------+------------------------------------+ + +Example +^^^^^^^ + +An example system offering two cores, one with support for |MPMM| and one +without, can be described as follows: + +.. code-block:: + + cpus { + #address-cells = <2>; + #size-cells = <0>; + + cpu0@00000 { + ... + + supports-mpmm; + }; + + cpu1@00100 { + ... + }; + } diff --git a/docs/components/ffa-manifest-binding.rst b/docs/components/ffa-manifest-binding.rst new file mode 100644 index 0000000..ee322ac --- /dev/null +++ b/docs/components/ffa-manifest-binding.rst @@ -0,0 +1,309 @@ +FF-A manifest binding to device tree +======================================== + +This document defines the nodes and properties used to define a partition, +according to the FF-A specification. + +Partition Properties +-------------------- + +- compatible [mandatory] + - value type: <string> + - Must be the string "arm,ffa-manifest-X.Y" which specifies the major and + minor versions of the device tree binding for the FFA manifest represented + by this node. The minor number is incremented if the binding changes in a + backwards compatible manner. + + - X is an integer representing the major version number of this document. + - Y is an integer representing the minor version number of this document. + +- ffa-version [mandatory] + - value type: <u32> + - Must be two 16 bits values (X, Y), concatenated as 31:16 -> X, + 15:0 -> Y, where: + + - X is the major version of FF-A expected by the partition at the FFA + instance it will execute. + - Y is the minor version of FF-A expected by the partition at the FFA + instance it will execute. + +- uuid [mandatory] + - value type: <prop-encoded-array> + - An array consisting of 4 <u32> values, identifying the UUID of the service + implemented by this partition. The UUID format is described in RFC 4122. + +- id + - value type: <u32> + - Pre-allocated partition ID. + +- auxiliary-id + - value type: <u32> + - Pre-allocated ID that could be used in memory management transactions. + +- description + - value type: <string> + - Name of the partition e.g. for debugging purposes. + +- execution-ctx-count [mandatory] + - value type: <u32> + - Number of vCPUs that a VM or SP wants to instantiate. + + - In the absence of virtualization, this is the number of execution + contexts that a partition implements. + - If value of this field = 1 and number of PEs > 1 then the partition is + treated as UP & migrate capable. + - If the value of this field > 1 then the partition is treated as a MP + capable partition irrespective of the number of PEs. + +- exception-level [mandatory] + - value type: <u32> + - The target exception level for the partition: + + - 0x0: EL1 + - 0x1: S_EL0 + - 0x2: S_EL1 + +- execution-state [mandatory] + - value type: <u32> + - The target execution state of the partition: + + - 0: AArch64 + - 1: AArch32 + +- load-address + - value type: <u64> + - Physical base address of the partition in memory. Absence of this field + indicates that the partition is position independent and can be loaded at + any address chosen at boot time. + +- entrypoint-offset + - value type: <u64> + - Offset from the base of the partition's binary image to the entry point of + the partition. Absence of this field indicates that the entry point is at + offset 0x0 from the base of the partition's binary. + +- xlat-granule [mandatory] + - value type: <u32> + - Translation granule used with the partition: + + - 0x0: 4k + - 0x1: 16k + - 0x2: 64k + +- boot-order + - value type: <u16> + - A unique number amongst all partitions that specifies if this partition + must be booted before others. The partition with the smaller number will be + booted first. + +- rx-tx-buffer + - value type: "memory-regions" node + - Specific "memory-regions" nodes that describe the RX/TX buffers expected + by the partition. + The "compatible" must be the string "arm,ffa-manifest-rx_tx-buffer". + +- messaging-method [mandatory] + - value type: <u8> + - Specifies which messaging methods are supported by the partition, set bit + means the feature is supported, clear bit - not supported: + + - Bit[0]: partition can receive direct requests if set + - Bit[1]: partition can send direct requests if set + - Bit[2]: partition can send and receive indirect messages + +- managed-exit + - value type: <empty> + - Specifies if managed exit is supported. + - This field is deprecated in favor of ns-interrupts-action field in the FF-A + v1.1 EAC0 spec. + +- ns-interrupts-action [mandatory] + - value type: <u32> + - Specifies the action that the SPMC must take in response to a Non-secure + physical interrupt. + + - 0x0: Non-secure interrupt is queued + - 0x1: Non-secure interrupt is signaled after a managed exit + - 0x2: Non-secure interrupt is signaled + + - This field supersedes the managed-exit field in the FF-A v1.0 spec. + +- other-s-interrupts-action + - value type: <u32> + - Specifies the action that the SPMC must take in response to a Other-Secure + physical interrupt. + + - 0x0: Other-Secure interrupt is queued + - 0x1: Other-Secure interrupt is signaled + +- has-primary-scheduler + - value type: <empty> + - Presence of this field indicates that the partition implements the primary + scheduler. If so, run-time EL must be EL1. + +- time-slice-mem + - value type: <empty> + - Presence of this field indicates that the partition doesn't expect the + partition manager to time slice long running memory management functions. + +- gp-register-num + - value type: <u32> + - The field specifies the general purpose register number but not its width. + The width is derived from the partition's execution state, as specified in + the partition properties. For example, if the number value is 1 then the + general-purpose register used will be x1 in AArch64 state and w1 in AArch32 + state. + Presence of this field indicates that the partition expects the address of + the FF-A boot information blob to be passed in the specified general purpose + register. + +- stream-endpoint-ids + - value type: <prop-encoded-array> + - List of <u32> tuples, identifying the IDs this partition is acting as + proxy for. + +- power-management-messages + - value type: <u32> + - Specifies which power management messages a partition subscribes to. + A set bit means the partition should be informed of the power event, clear + bit - should not be informed of event: + + - Bit[0]: CPU_OFF + - Bit[1]: CPU_SUSPEND + - Bit[2]: CPU_SUSPEND_RESUME + +Memory Regions +-------------- + +- compatible [mandatory] + - value type: <string> + - Must be the string "arm,ffa-manifest-memory-regions". + +- description + - value type: <string> + - Name of the memory region e.g. for debugging purposes. + +- pages-count [mandatory] + - value type: <u32> + - Count of pages of memory region as a multiple of the translation granule + size + +- attributes [mandatory] + - value type: <u32> + - Mapping modes: ORed to get required permission + + - 0x1: Read + - 0x2: Write + - 0x4: Execute + - 0x8: Security state + +- base-address + - value type: <u64> + - Base address of the region. The address must be aligned to the translation + granule size. + The address given may be a Physical Address (PA), Virtual Address (VA), or + Intermediate Physical Address (IPA). Refer to the FF-A specification for + more information on the restrictions around the address type. + If the base address is omitted then the partition manager must map a memory + region of the specified size into the partition's translation regime and + then communicate the region properties (including the base address chosen + by the partition manager) to the partition. + +Device Regions +-------------- + +- compatible [mandatory] + - value type: <string> + - Must be the string "arm,ffa-manifest-device-regions". + +- description + - value type: <string> + - Name of the device region e.g. for debugging purposes. + +- pages-count [mandatory] + - value type: <u32> + - Count of pages of memory region as a multiple of the translation granule + size + +- attributes [mandatory] + - value type: <u32> + - Mapping modes: ORed to get required permission + + - 0x1: Read + - 0x2: Write + - 0x4: Execute + - 0x8: Security state + +- base-address [mandatory] + - value type: <u64> + - Base address of the region. The address must be aligned to the translation + granule size. + The address given may be a Physical Address (PA), Virtual Address (VA), or + Intermediate Physical Address (IPA). Refer to the FF-A specification for + more information on the restrictions around the address type. + +- smmu-id + - value type: <u32> + - On systems with multiple System Memory Management Units (SMMUs) this + identifier is used to inform the partition manager which SMMU the device is + upstream of. If the field is omitted then it is assumed that the device is + not upstream of any SMMU. + +- stream-ids + - value type: <prop-encoded-array> + - A list of (id, mem-manage) pair, where: + + - id: A unique <u32> value amongst all devices assigned to the partition. + +- interrupts [mandatory] + - value type: <prop-encoded-array> + - A list of (id, attributes) pair describing the device interrupts, where: + + - id: The <u32> interrupt IDs. + - attributes: A <u32> value, containing attributes for each interrupt ID: + + +----------------------+----------+ + |Field | Bit(s) | + +----------------------+----------+ + | Priority | 7:0 | + +----------------------+----------+ + | Security state | 8 | + +----------------------+----------+ + | Config(Edge/Level) | 9 | + +----------------------+----------+ + | Type(SPI/PPI/SGI) | 11:10 | + +----------------------+----------+ + + Security state: + - Secure: 1 + - Non-secure: 0 + + Configuration: + - Edge triggered: 0 + - Level triggered: 1 + + Type: + - SPI: 0b10 + - PPI: 0b01 + - SGI: 0b00 + +- interrupts-target + - value type: <prop-encoded-array> + - A list of (id, mpdir upper bits, mpidr lower bits) tuples describing which + mpidr the interrupt is routed to, where: + + - id: The <u32> interrupt ID. Must be one of those specified in the + "interrupts" field. + - mpidr upper bits: The <u32> describing the upper bits of the 64 bits + mpidr + - mpidr lower bits: The <u32> describing the lower bits of the 64 bits + mpidr + +- exclusive-access + - value type: <empty> + - Presence of this field implies that this endpoint must be granted exclusive + access and ownership of this device's MMIO region. + +-------------- + +*Copyright (c) 2019-2022, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/firmware-update.rst b/docs/components/firmware-update.rst new file mode 100644 index 0000000..1ba1e1c --- /dev/null +++ b/docs/components/firmware-update.rst @@ -0,0 +1,497 @@ +Firmware Update (FWU) +===================== + +This document describes the design of the various Firmware Update (FWU) +mechanisms available in TF-A. + +1. PSA Firmware Update (PSA FWU) +2. TBBR Firmware Update (TBBR FWU) + +PSA Firmware Update implements the specification of the same name (Arm document +IHI 0093), which defines a standard firmware interface for installing firmware +updates. +On the other hand, TBBR Firmware Update only covers firmware recovery. Arguably, +its name is somewhat misleading but the TBBR specification and terminology +predates PSA FWU. Both mechanisms are complementary in the sense that PSA FWU +assumes that the device has a backup or recovery capability in the event of a +failed update, which can be fulfilled with TBBR FWU implementation. + +.. _PSA Firmware Update: + +PSA Firmware Update (PSA FWU) +----------------------------- + +Introduction +~~~~~~~~~~~~ +The `PSA FW update specification`_ defines the concepts of ``Firmware Update +Client`` and ``Firmware Update Agent``. +The new firmware images are provided by the ``Client`` to the ``Update Agent`` +to flash them in non-volatile storage. + +A common system design will place the ``Update Agent`` in the Secure-world +while the ``Client`` executes in the Normal-world. +The `PSA FW update specification`_ provides ABIs meant for a Normal-world +entity aka ``Client`` to transmit the firmware images to the ``Update Agent``. + +Scope +~~~~~ +The design of the ``Client`` and ``Update Agent`` is out of scope of this +document. +This document mainly covers ``Platform Boot`` details i.e. the role of +the second stage Bootloader after FWU has been done by ``Client`` and +``Update Agent``. + +Overview +~~~~~~~~ + +There are active and update banks in the non-volatile storage identified +by the ``active_index`` and the ``update_index`` respectively. +An active bank stores running firmware, whereas an update bank contains +firmware updates. + +Once Firmwares are updated in the update bank of the non-volatile +storage, then ``Update Agent`` marks the update bank as the active bank, +and write updated FWU metadata in non-volatile storage. +On subsequent reboot, the second stage Bootloader (BL2) performs the +following actions: + +- Read FWU metadata in memory +- Retrieve the image specification (offset and length) of updated images + present in non-volatile storage with the help of FWU metadata +- Set these image specification in the corresponding I/O policies of the + updated images using the FWU platform functions + ``plat_fwu_set_images_source()`` and ``plat_fwu_set_metadata_image_source()``, + please refer :ref:`Porting Guide` +- Use these I/O policies to read the images from this address into the memory + +By default, the platform uses the active bank of non-volatile storage to boot +the images in ``trial state``. If images pass through the authentication check +and also if the system successfully booted the Normal-world image then +``Update Agent`` marks this update as accepted after further sanitisation +checking at Normal-world. + +The second stage Bootloader (BL2) avoids upgrading the platform NV-counter until +it's been confirmed that given update is accepted. + +The following sequence diagram shows platform-boot flow: + +.. image:: ../resources/diagrams/PSA-FWU.png + +If the platform fails to boot from active bank due to any reasons such +as authentication failure or non-fuctionality of Normal-world software then the +watchdog will reset to give a chance to the platform to fix the issue. This +boot failure & reset sequence might be repeated up to ``trial state`` times. +After that, the platform can decide to boot from the ``previous_active_index`` +bank. + +If the images still does not boot successfully from the ``previous_active_index`` +bank (e.g. due to ageing effect of non-volatile storage) then the platform can +choose firmware recovery mechanism :ref:`TBBR Firmware Update` to bring system +back to life. + +.. _TBBR Firmware Update: + +TBBR Firmware Update (TBBR FWU) +------------------------------- + +Introduction +~~~~~~~~~~~~ + +This technique enables authenticated firmware to update firmware images from +external interfaces such as USB, UART, SD-eMMC, NAND, NOR or Ethernet to SoC +Non-Volatile memories such as NAND Flash, LPDDR2-NVM or any memory determined +by the platform. +This feature functions even when the current firmware in the system is corrupt +or missing; it therefore may be used as a recovery mode. It may also be +complemented by other, higher level firmware update software. + +FWU implements a specific part of the Trusted Board Boot Requirements (TBBR) +specification, Arm DEN0006C-1. It should be used in conjunction with the +:ref:`Trusted Board Boot` design document, which describes the image +authentication parts of the Trusted Firmware-A (TF-A) TBBR implementation. + +It can be used as a last resort when all firmware updates that are carried out +as part of the :ref:`PSA Firmware Update` procedure have failed to function. + +Scope +~~~~~ + +This document describes the secure world FWU design. It is beyond its scope to +describe how normal world FWU images should operate. To implement normal world +FWU images, please refer to the "Non-Trusted Firmware Updater" requirements in +the TBBR. + +Overview +~~~~~~~~ + +The FWU boot flow is primarily mediated by BL1. Since BL1 executes in ROM, and +it is usually desirable to minimize the amount of ROM code, the design allows +some parts of FWU to be implemented in other secure and normal world images. +Platform code may choose which parts are implemented in which images but the +general expectation is: + +- BL1 handles: + + - Detection and initiation of the FWU boot flow. + - Copying images from non-secure to secure memory + - FWU image authentication + - Context switching between the normal and secure world during the FWU + process. + +- Other secure world FWU images handle platform initialization required by + the FWU process. +- Normal world FWU images handle loading of firmware images from external + interfaces to non-secure memory. + +The primary requirements of the FWU feature are: + +#. Export a BL1 SMC interface to interoperate with other FWU images executing + at other Exception Levels. +#. Export a platform interface to provide FWU common code with the information + it needs, and to enable platform specific FWU functionality. See the + :ref:`Porting Guide` for details of this interface. + +TF-A uses abbreviated image terminology for FWU images like for other TF-A +images. See the :ref:`Image Terminology` document for an explanation of these +terms. + +The following diagram shows the FWU boot flow for Arm development platforms. +Arm CSS platforms like Juno have a System Control Processor (SCP), and these +use all defined FWU images. Other platforms may use a subset of these. + +|Flow Diagram| + +Image Identification +~~~~~~~~~~~~~~~~~~~~ + +Each FWU image and certificate is identified by a unique ID, defined by the +platform, which BL1 uses to fetch an image descriptor (``image_desc_t``) via a +call to ``bl1_plat_get_image_desc()``. The same ID is also used to prepare the +Chain of Trust (Refer to the :ref:`Authentication Framework & Chain of Trust` +document for more information). + +The image descriptor includes the following information: + +- Executable or non-executable image. This indicates whether the normal world + is permitted to request execution of a secure world FWU image (after + authentication). Secure world certificates and non-AP images are examples + of non-executable images. +- Secure or non-secure image. This indicates whether the image is + authenticated/executed in secure or non-secure memory. +- Image base address and size. +- Image entry point configuration (an ``entry_point_info_t``). +- FWU image state. + +BL1 uses the FWU image descriptors to: + +- Validate the arguments of FWU SMCs +- Manage the state of the FWU process +- Initialize the execution state of the next FWU image. + +FWU State Machine +~~~~~~~~~~~~~~~~~ + +BL1 maintains state for each FWU image during FWU execution. FWU images at lower +Exception Levels raise SMCs to invoke FWU functionality in BL1, which causes +BL1 to update its FWU image state. The BL1 image states and valid state +transitions are shown in the diagram below. Note that secure images have a more +complex state machine than non-secure images. + +|FWU state machine| + +The following is a brief description of the supported states: + +- RESET: This is the initial state of every image at the start of FWU. + Authentication failure also leads to this state. A secure + image may yield to this state if it has completed execution. + It can also be reached by using ``FWU_SMC_IMAGE_RESET``. + +- COPYING: This is the state of a secure image while BL1 is copying it + in blocks from non-secure to secure memory. + +- COPIED: This is the state of a secure image when BL1 has completed + copying it to secure memory. + +- AUTHENTICATED: This is the state of an image when BL1 has successfully + authenticated it. + +- EXECUTED: This is the state of a secure, executable image when BL1 has + passed execution control to it. + +- INTERRUPTED: This is the state of a secure, executable image after it has + requested BL1 to resume normal world execution. + +BL1 SMC Interface +~~~~~~~~~~~~~~~~~ + +BL1_SMC_CALL_COUNT +^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x0 + + Return: + uint32_t + +This SMC returns the number of SMCs supported by BL1. + +BL1_SMC_UID +^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x1 + + Return: + UUID : 32 bits in each of w0-w3 (or r0-r3 for AArch32 callers) + +This SMC returns the 128-bit `Universally Unique Identifier`_ for the +BL1 SMC service. + +BL1_SMC_VERSION +^^^^^^^^^^^^^^^ + +:: + + Argument: + uint32_t function ID : 0x3 + + Return: + uint32_t : Bits [31:16] Major Version + Bits [15:0] Minor Version + +This SMC returns the current version of the BL1 SMC service. + +BL1_SMC_RUN_IMAGE +^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x4 + entry_point_info_t *ep_info + + Return: + void + + Pre-conditions: + if (normal world caller) synchronous exception + if (ep_info not EL3) synchronous exception + +This SMC passes execution control to an EL3 image described by the provided +``entry_point_info_t`` structure. In the normal TF-A boot flow, BL2 invokes +this SMC for BL1 to pass execution control to BL31. + +FWU_SMC_IMAGE_COPY +^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x10 + unsigned int image_id + uintptr_t image_addr + unsigned int block_size + unsigned int image_size + + Return: + int : 0 (Success) + : -ENOMEM + : -EPERM + + Pre-conditions: + if (image_id is invalid) return -EPERM + if (image_id is non-secure image) return -EPERM + if (image_id state is not (RESET or COPYING)) return -EPERM + if (secure world caller) return -EPERM + if (image_addr + block_size overflows) return -ENOMEM + if (image destination address + image_size overflows) return -ENOMEM + if (source block is in secure memory) return -ENOMEM + if (source block is not mapped into BL1) return -ENOMEM + if (image_size > free secure memory) return -ENOMEM + if (image overlaps another image) return -EPERM + +This SMC copies the secure image indicated by ``image_id`` from non-secure memory +to secure memory for later authentication. The image may be copied in a single +block or multiple blocks. In either case, the total size of the image must be +provided in ``image_size`` when invoking this SMC for the first time for each +image; it is ignored in subsequent calls (if any) for the same image. + +The ``image_addr`` and ``block_size`` specify the source memory block to copy from. +The destination address is provided by the platform code. + +If ``block_size`` is greater than the amount of remaining bytes to copy for this +image then the former is truncated to the latter. The copy operation is then +considered as complete and the FWU state machine transitions to the "COPIED" +state. If there is still more to copy, the FWU state machine stays in or +transitions to the COPYING state (depending on the previous state). + +When using multiple blocks, the source blocks do not necessarily need to be in +contiguous memory. + +Once the SMC is handled, BL1 returns from exception to the normal world caller. + +FWU_SMC_IMAGE_AUTH +^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x11 + unsigned int image_id + uintptr_t image_addr + unsigned int image_size + + Return: + int : 0 (Success) + : -ENOMEM + : -EPERM + : -EAUTH + + Pre-conditions: + if (image_id is invalid) return -EPERM + if (secure world caller) + if (image_id state is not RESET) return -EPERM + if (image_addr/image_size is not mapped into BL1) return -ENOMEM + else // normal world caller + if (image_id is secure image) + if (image_id state is not COPIED) return -EPERM + else // image_id is non-secure image + if (image_id state is not RESET) return -EPERM + if (image_addr/image_size is in secure memory) return -ENOMEM + if (image_addr/image_size not mapped into BL1) return -ENOMEM + +This SMC authenticates the image specified by ``image_id``. If the image is in the +RESET state, BL1 authenticates the image in place using the provided +``image_addr`` and ``image_size``. If the image is a secure image in the COPIED +state, BL1 authenticates the image from the secure memory that BL1 previously +copied the image into. + +BL1 returns from exception to the caller. If authentication succeeds then BL1 +sets the image state to AUTHENTICATED. If authentication fails then BL1 returns +the -EAUTH error and sets the image state back to RESET. + +FWU_SMC_IMAGE_EXECUTE +^^^^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x12 + unsigned int image_id + + Return: + int : 0 (Success) + : -EPERM + + Pre-conditions: + if (image_id is invalid) return -EPERM + if (secure world caller) return -EPERM + if (image_id is non-secure image) return -EPERM + if (image_id is non-executable image) return -EPERM + if (image_id state is not AUTHENTICATED) return -EPERM + +This SMC initiates execution of a previously authenticated image specified by +``image_id``, in the other security world to the caller. The current +implementation only supports normal world callers initiating execution of a +secure world image. + +BL1 saves the normal world caller's context, sets the secure image state to +EXECUTED, and returns from exception to the secure image. + +FWU_SMC_IMAGE_RESUME +^^^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x13 + register_t image_param + + Return: + register_t : image_param (Success) + : -EPERM + + Pre-conditions: + if (normal world caller and no INTERRUPTED secure image) return -EPERM + +This SMC resumes execution in the other security world while there is a secure +image in the EXECUTED/INTERRUPTED state. + +For normal world callers, BL1 sets the previously interrupted secure image state +to EXECUTED. For secure world callers, BL1 sets the previously executing secure +image state to INTERRUPTED. In either case, BL1 saves the calling world's +context, restores the resuming world's context and returns from exception into +the resuming world. If the call is successful then the caller provided +``image_param`` is returned to the resumed world, otherwise an error code is +returned to the caller. + +FWU_SMC_SEC_IMAGE_DONE +^^^^^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x14 + + Return: + int : 0 (Success) + : -EPERM + + Pre-conditions: + if (normal world caller) return -EPERM + +This SMC indicates completion of a previously executing secure image. + +BL1 sets the previously executing secure image state to the RESET state, +restores the normal world context and returns from exception into the normal +world. + +FWU_SMC_UPDATE_DONE +^^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x15 + register_t client_cookie + + Return: + N/A + +This SMC completes the firmware update process. BL1 calls the platform specific +function ``bl1_plat_fwu_done``, passing the optional argument ``client_cookie`` as +a ``void *``. The SMC does not return. + +FWU_SMC_IMAGE_RESET +^^^^^^^^^^^^^^^^^^^ + +:: + + Arguments: + uint32_t function ID : 0x16 + unsigned int image_id + + Return: + int : 0 (Success) + : -EPERM + + Pre-conditions: + if (secure world caller) return -EPERM + if (image in EXECUTED) return -EPERM + +This SMC sets the state of an image to RESET and zeroes the memory used by it. + +This is only allowed if the image is not being executed. + +-------------- + +*Copyright (c) 2015-2022, Arm Limited and Contributors. All rights reserved.* + +.. _Universally Unique Identifier: https://tools.ietf.org/rfc/rfc4122.txt +.. |Flow Diagram| image:: ../resources/diagrams/fwu_flow.png +.. |FWU state machine| image:: ../resources/diagrams/fwu_states.png +.. _PSA FW update specification: https://developer.arm.com/documentation/den0118/a/ diff --git a/docs/components/granule-protection-tables-design.rst b/docs/components/granule-protection-tables-design.rst new file mode 100644 index 0000000..07637dd --- /dev/null +++ b/docs/components/granule-protection-tables-design.rst @@ -0,0 +1,235 @@ +Granule Protection Tables Library +================================= + +This document describes the design of the granule protection tables (GPT) +library used by Trusted Firmware-A (TF-A). This library provides the APIs needed +to initialize the GPTs based on a data structure containing information about +the systems memory layout, configure the system registers to enable granule +protection checks based on these tables, and transition granules between +different PAS (physical address spaces) at runtime. + +Arm CCA adds two new security states for a total of four: root, realm, secure, and +non-secure. In addition to new security states, corresponding physical address +spaces have been added to control memory access for each state. The PAS access +allowed to each security state can be seen in the table below. + +.. list-table:: Security states and PAS access rights + :widths: 25 25 25 25 25 + :header-rows: 1 + + * - + - Root state + - Realm state + - Secure state + - Non-secure state + * - Root PAS + - yes + - no + - no + - no + * - Realm PAS + - yes + - yes + - no + - no + * - Secure PAS + - yes + - no + - yes + - no + * - Non-secure PAS + - yes + - yes + - yes + - yes + +The GPT can function as either a 1 level or 2 level lookup depending on how a +PAS region is configured. The first step is the level 0 table, each entry in the +level 0 table controls access to a relatively large region in memory (block +descriptor), and the entire region can belong to a single PAS when a one step +mapping is used, or a level 0 entry can link to a level 1 table where relatively +small regions (granules) of memory can be assigned to different PAS with a 2 +step mapping. The type of mapping used for each PAS is determined by the user +when setting up the configuration structure. + +Design Concepts and Interfaces +------------------------------ + +This section covers some important concepts and data structures used in the GPT +library. + +There are three main parameters that determine how the tables are organized and +function: the PPS (protected physical space) which is the total amount of +protected physical address space in the system, PGS (physical granule size) +which is how large each level 1 granule is, and L0GPTSZ (level 0 GPT size) which +determines how much physical memory is governed by each level 0 entry. A granule +is the smallest unit of memory that can be independently assigned to a PAS. + +L0GPTSZ is determined by the hardware and is read from the GPCCR_EL3 register. +PPS and PGS are passed into the APIs at runtime and can be determined in +whatever way is best for a given platform, either through some algorithm or hard +coded in the firmware. + +GPT setup is split into two parts: table creation and runtime initialization. In +the table creation step, a data structure containing information about the +desired PAS regions is passed into the library which validates the mappings, +creates the tables in memory, and enables granule protection checks. In the +runtime initialization step, the runtime firmware locates the existing tables in +memory using the GPT register configuration and saves important data to a +structure used by the granule transition service which will be covered more +below. + +In the reference implementation for FVP models, you can find an example of PAS +region definitions in the file ``include/plat/arm/common/arm_pas_def.h``. Table +creation API calls can be found in ``plat/arm/common/arm_bl2_setup.c`` and +runtime initialization API calls can be seen in +``plat/arm/common/arm_bl31_setup.c``. + +Defining PAS regions +~~~~~~~~~~~~~~~~~~~~ + +A ``pas_region_t`` structure is a way to represent a physical address space and +its attributes that can be used by the GPT library to initialize the tables. + +This structure is composed of the following: + +#. The base physical address +#. The region size +#. The desired attributes of this memory region (mapping type, PAS type) + +See the ``pas_region_t`` type in ``include/lib/gpt_rme/gpt_rme.h``. + +The programmer should provide the API with an array containing ``pas_region_t`` +structures, then the library will check the desired memory access layout for +validity and create tables to implement it. + +``pas_region_t`` is a public type, however it is recommended that the macros +``GPT_MAP_REGION_BLOCK`` and ``GPT_MAP_REGION_GRANULE`` be used to populate +these structures instead of doing it manually to reduce the risk of future +compatibility issues. These macros take the base physical address, region size, +and PAS type as arguments to generate the pas_region_t structure. As the names +imply, ``GPT_MAP_REGION_BLOCK`` creates a region using only L0 mapping while +``GPT_MAP_REGION_GRANULE`` creates a region using L0 and L1 mappings. + +Level 0 and Level 1 Tables +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The GPT initialization APIs require memory to be passed in for the tables to be +constructed, ``gpt_init_l0_tables`` takes a memory address and size for building +the level 0 tables and ``gpt_init_pas_l1_tables`` takes an address and size for +building the level 1 tables which are linked from level 0 descriptors. The +tables should have PAS type ``GPT_GPI_ROOT`` and a typical system might place +its level 0 table in SRAM and its level 1 table(s) in DRAM. + +Granule Transition Service +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The Granule Transition Service allows memory mapped with GPT_MAP_REGION_GRANULE +ownership to be changed using SMC calls. Non-secure granules can be transitioned +to either realm or secure space, and realm and secure granules can be +transitioned back to non-secure. This library only allows memory mapped as +granules to be transitioned, memory mapped as blocks have their GPIs fixed after +table creation. + +Library APIs +------------ + +The public APIs and types can be found in ``include/lib/gpt_rme/gpt_rme.h`` and this +section is intended to provide additional details and clarifications. + +To create the GPTs and enable granule protection checks the APIs need to be +called in the correct order and at the correct time during the system boot +process. + +#. Firmware must enable the MMU. +#. Firmware must call ``gpt_init_l0_tables`` to initialize the level 0 tables to + a default state, that is, initializing all of the L0 descriptors to allow all + accesses to all memory. The PPS is provided to this function as an argument. +#. DDR discovery and initialization by the system, the discovered DDR region(s) + are then added to the L1 PAS regions to be initialized in the next step and + used by the GTSI at runtime. +#. Firmware must call ``gpt_init_pas_l1_tables`` with a pointer to an array of + ``pas_region_t`` structures containing the desired memory access layout. The + PGS is provided to this function as an argument. +#. Firmware must call ``gpt_enable`` to enable granule protection checks by + setting the correct register values. +#. In systems that make use of the granule transition service, runtime + firmware must call ``gpt_runtime_init`` to set up the data structures needed + by the GTSI to find the tables and transition granules between PAS types. + +API Constraints +~~~~~~~~~~~~~~~ + +The values allowed by the API for PPS and PGS are enumerated types +defined in the file ``include/lib/gpt_rme/gpt_rme.h``. + +Allowable values for PPS along with their corresponding size. + +* ``GPCCR_PPS_4GB`` (4GB protected space, 0x100000000 bytes) +* ``GPCCR_PPS_64GB`` (64GB protected space, 0x1000000000 bytes) +* ``GPCCR_PPS_1TB`` (1TB protected space, 0x10000000000 bytes) +* ``GPCCR_PPS_4TB`` (4TB protected space, 0x40000000000 bytes) +* ``GPCCR_PPS_16TB`` (16TB protected space, 0x100000000000 bytes) +* ``GPCCR_PPS_256TB`` (256TB protected space, 0x1000000000000 bytes) +* ``GPCCR_PPS_4PB`` (4PB protected space, 0x10000000000000 bytes) + +Allowable values for PGS along with their corresponding size. + +* ``GPCCR_PGS_4K`` (4KB granules, 0x1000 bytes) +* ``GPCCR_PGS_16K`` (16KB granules, 0x4000 bytes) +* ``GPCCR_PGS_64K`` (64KB granules, 0x10000 bytes) + +Allowable values for L0GPTSZ along with the corresponding size. + +* ``GPCCR_L0GPTSZ_30BITS`` (1GB regions, 0x40000000 bytes) +* ``GPCCR_L0GPTSZ_34BITS`` (16GB regions, 0x400000000 bytes) +* ``GPCCR_L0GPTSZ_36BITS`` (64GB regions, 0x1000000000 bytes) +* ``GPCCR_L0GPTSZ_39BITS`` (512GB regions, 0x8000000000 bytes) + +Note that the value of the PPS, PGS, and L0GPTSZ definitions is an encoded value +corresponding to the size, not the size itself. The decoded hex representations +of the sizes have been provided for convenience. + +The L0 table memory has some constraints that must be taken into account. + +* The L0 table must be aligned to either the table size or 4096 bytes, whichever + is greater. L0 table size is the total protected space (PPS) divided by the + size of each L0 region (L0GPTSZ) multiplied by the size of each L0 descriptor + (8 bytes). ((PPS / L0GPTSZ) * 8) +* The L0 memory size must be greater than or equal to the table size. +* The L0 memory must fall within a PAS of type GPT_GPI_ROOT. + +The L1 memory also has some constraints. + +* The L1 tables must be aligned to their size. The size of each L1 table is the + size of each L0 region (L0GPTSZ) divided by the granule size (PGS) divided by + the granules controlled in each byte (2). ((L0GPTSZ / PGS) / 2) +* There must be enough L1 memory supplied to build all requested L1 tables. +* The L1 memory must fall within a PAS of type GPT_GPI_ROOT. + +If an invalid combination of parameters is supplied, the APIs will print an +error message and return a negative value. The return values of APIs should be +checked to ensure successful configuration. + +Sample Calculation for L0 memory size and alignment +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Let PPS=GPCCR_PPS_4GB and L0GPTSZ=GPCCR_L0GPTSZ_30BITS + +We can find the total L0 table size with ((PPS / L0GPTSZ) * 8) + +Substitute values to get this: ((0x100000000 / 0x40000000) * 8) + +And solve to get 32 bytes. In this case, 4096 is greater than 32, so the L0 +tables must be aligned to 4096 bytes. + +Sample calculation for L1 table size and alignment +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Let PGS=GPCCR_PGS_4K and L0GPTSZ=GPCCR_L0GPTSZ_30BITS + +We can find the size of each L1 table with ((L0GPTSZ / PGS) / 2). + +Substitute values: ((0x40000000 / 0x1000) / 2) + +And solve to get 0x20000 bytes per L1 table. diff --git a/docs/components/index.rst b/docs/components/index.rst new file mode 100644 index 0000000..30d80fc --- /dev/null +++ b/docs/components/index.rst @@ -0,0 +1,28 @@ +Components +========== + +.. toctree:: + :maxdepth: 1 + :caption: Contents + + spd/index + activity-monitors + arm-sip-service + debugfs-design + exception-handling + fconf/index + firmware-update + measured_boot/index + mpmm + platform-interrupt-controller-API + ras + romlib-design + sdei + secure-partition-manager + el3-spmc + secure-partition-manager-mm + xlat-tables-lib-v2-design + cot-binding + realm-management-extension + rmm-el3-comms-spec + granule-protection-tables-design diff --git a/docs/components/measured_boot/event_log.rst b/docs/components/measured_boot/event_log.rst new file mode 100644 index 0000000..c102bea --- /dev/null +++ b/docs/components/measured_boot/event_log.rst @@ -0,0 +1,43 @@ +DTB binding for Event Log properties +==================================== + +This document describes the device tree format of Event Log properties. +These properties are not related to a specific platform and can be queried +from common code. + +Dynamic configuration for Event Log +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Measured Boot driver expects a *tpm_event_log* node with the following field +in 'tb_fw_config', 'nt_fw_config' and 'tsp_fw_config' DTS files: + +- compatible [mandatory] + - value type: <string> + - Must be the string "arm,tpm_event_log". + +Then a list of properties representing Event Log configuration, which +can be used by Measured Boot driver. Each property is named according +to the information it contains: + +- tpm_event_log_sm_addr [fvp_nt_fw_config.dts with OP-TEE] + - value type: <u64> + - Event Log base address in secure memory. + +Note. Currently OP-TEE does not support reading DTBs from Secure memory +and this property should be removed when this feature is supported. + +- tpm_event_log_addr [mandatory] + - value type: <u64> + - Event Log base address in non-secure memory. + +- tpm_event_log_size [mandatory] + - value type: <u32> + - Event Log size. + +- tpm_event_log_max_size [mandatory] + - value type: <u32> + - Event Log maximum size. + +-------------- + +*Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/measured_boot/index.rst b/docs/components/measured_boot/index.rst new file mode 100644 index 0000000..e7f2634 --- /dev/null +++ b/docs/components/measured_boot/index.rst @@ -0,0 +1,12 @@ +Measured Boot Driver (MBD) +========================== + +.. _measured-boot-document: + +Properties binding information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. toctree:: + :maxdepth: 1 + + event_log diff --git a/docs/components/mpmm.rst b/docs/components/mpmm.rst new file mode 100644 index 0000000..1b1c6d8 --- /dev/null +++ b/docs/components/mpmm.rst @@ -0,0 +1,30 @@ +Maximum Power Mitigation Mechanism (MPMM) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +|MPMM| is an optional microarchitectural power management mechanism supported by +some Arm Armv9-A cores, beginning with the Cortex-X2, Cortex-A710 and +Cortex-A510 cores. This mechanism detects and limits high-activity events to +assist in |SoC| processor power domain dynamic power budgeting and limit the +triggering of whole-rail (i.e. clock chopping) responses to overcurrent +conditions. + +|MPMM| is enabled on a per-core basis by the EL3 runtime firmware. The presence +of |MPMM| cannot be determined at runtime by the firmware, and therefore the +platform must expose this information through one of two possible mechanisms: + +- |FCONF|, controlled by the ``ENABLE_MPMM_FCONF`` build option. +- A platform implementation of the ``plat_mpmm_topology`` function (the + default). + +See :ref:`Maximum Power Mitigation Mechanism (MPMM) Bindings` for documentation +on the |FCONF| device tree bindings. + +.. warning:: + + |MPMM| exposes gear metrics through the auxiliary |AMU| counters. An + external power controller can use these metrics to budget SoC power by + limiting the number of cores that can execute higher-activity workloads or + switching to a different DVFS operating point. When this is the case, the + |AMU| counters that make up the |MPMM| gears must be enabled by the EL3 + runtime firmware - please see :ref:`Activity Monitor Auxiliary Counters` for + documentation on enabling auxiliary |AMU| counters. diff --git a/docs/components/platform-interrupt-controller-API.rst b/docs/components/platform-interrupt-controller-API.rst new file mode 100644 index 0000000..4de39d1 --- /dev/null +++ b/docs/components/platform-interrupt-controller-API.rst @@ -0,0 +1,309 @@ +Platform Interrupt Controller API +================================= + +This document lists the optional platform interrupt controller API that +abstracts the runtime configuration and control of interrupt controller from the +generic code. The mandatory APIs are described in the +:ref:`Porting Guide <porting_guide_imf_in_bl31>`. + +Function: unsigned int plat_ic_get_running_priority(void); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : void + Return : unsigned int + +This API should return the priority of the interrupt the PE is currently +servicing. This must be be called only after an interrupt has already been +acknowledged via ``plat_ic_acknowledge_interrupt``. + +In the case of Arm standard platforms using GIC, the *Running Priority Register* +is read to determine the priority of the interrupt. + +Function: int plat_ic_is_spi(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : int + +The API should return whether the interrupt ID (first parameter) is categorized +as a Shared Peripheral Interrupt. Shared Peripheral Interrupts are typically +associated to system-wide peripherals, and these interrupts can target any PE in +the system. + +Function: int plat_ic_is_ppi(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : int + +The API should return whether the interrupt ID (first parameter) is categorized +as a Private Peripheral Interrupt. Private Peripheral Interrupts are typically +associated with peripherals that are private to each PE. Interrupts from private +peripherals target to that PE only. + +Function: int plat_ic_is_sgi(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : int + +The API should return whether the interrupt ID (first parameter) is categorized +as a Software Generated Interrupt. Software Generated Interrupts are raised by +explicit programming by software, and are typically used in inter-PE +communication. Secure SGIs are reserved for use by Secure world software. + +Function: unsigned int plat_ic_get_interrupt_active(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : int + +This API should return the *active* status of the interrupt ID specified by the +first parameter, ``id``. + +In case of Arm standard platforms using GIC, the implementation of the API reads +the GIC *Set Active Register* to read and return the active status of the +interrupt. + +Function: void plat_ic_enable_interrupt(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : void + +This API should enable the interrupt ID specified by the first parameter, +``id``. PEs in the system are expected to receive only enabled interrupts. + +In case of Arm standard platforms using GIC, the implementation of the API +inserts barrier to make memory updates visible before enabling interrupt, and +then writes to GIC *Set Enable Register* to enable the interrupt. + +Function: void plat_ic_disable_interrupt(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : void + +This API should disable the interrupt ID specified by the first parameter, +``id``. PEs in the system are not expected to receive disabled interrupts. + +In case of Arm standard platforms using GIC, the implementation of the API +writes to GIC *Clear Enable Register* to disable the interrupt, and inserts +barrier to make memory updates visible afterwards. + +Function: void plat_ic_set_interrupt_priority(unsigned int id, unsigned int priority); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Argument : unsigned int + Return : void + +This API should set the priority of the interrupt specified by first parameter +``id`` to the value set by the second parameter ``priority``. + +In case of Arm standard platforms using GIC, the implementation of the API +writes to GIC *Priority Register* set interrupt priority. + +Function: bool plat_ic_has_interrupt_type(unsigned int type); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : bool + +This API should return whether the platform supports a given interrupt type. The +parameter ``type`` shall be one of ``INTR_TYPE_EL3``, ``INTR_TYPE_S_EL1``, or +``INTR_TYPE_NS``. + +In case of Arm standard platforms using GICv3, the implementation of the API +returns *true* for all interrupt types. + +In case of Arm standard platforms using GICv2, the API always return *true* for +``INTR_TYPE_NS``. Return value for other types depends on the value of build +option ``GICV2_G0_FOR_EL3``: + +- For interrupt type ``INTR_TYPE_EL3``: + + - When ``GICV2_G0_FOR_EL3`` is ``0``, it returns *false*, indicating no support + for EL3 interrupts. + + - When ``GICV2_G0_FOR_EL3`` is ``1``, it returns *true*, indicating support for + EL3 interrupts. + +- For interrupt type ``INTR_TYPE_S_EL1``: + + - When ``GICV2_G0_FOR_EL3`` is ``0``, it returns *true*, indicating support for + Secure EL1 interrupts. + + - When ``GICV2_G0_FOR_EL3`` is ``1``, it returns *false*, indicating no support + for Secure EL1 interrupts. + +Function: void plat_ic_set_interrupt_type(unsigned int id, unsigned int type); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Argument : unsigned int + Return : void + +This API should set the interrupt specified by first parameter ``id`` to the +type specified by second parameter ``type``. The ``type`` parameter can be +one of: + +- ``INTR_TYPE_NS``: interrupt is meant to be consumed by the Non-secure world. + +- ``INTR_TYPE_S_EL1``: interrupt is meant to be consumed by Secure EL1. + +- ``INTR_TYPE_EL3``: interrupt is meant to be consumed by EL3. + +In case of Arm standard platforms using GIC, the implementation of the API +writes to the GIC *Group Register* and *Group Modifier Register* (only GICv3) to +assign the interrupt to the right group. + +For GICv3: + +- ``INTR_TYPE_NS`` maps to Group 1 interrupt. + +- ``INTR_TYPE_S_EL1`` maps to Secure Group 1 interrupt. + +- ``INTR_TYPE_EL3`` maps to Secure Group 0 interrupt. + +For GICv2: + +- ``INTR_TYPE_NS`` maps to Group 1 interrupt. + +- When the build option ``GICV2_G0_FOR_EL3`` is set to ``0`` (the default), + ``INTR_TYPE_S_EL1`` maps to Group 0. Otherwise, ``INTR_TYPE_EL3`` maps to + Group 0 interrupt. + +Function: void plat_ic_raise_el3_sgi(int sgi_num, u_register_t target); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : int + Argument : u_register_t + Return : void + +This API should raise an EL3 SGI. The first parameter, ``sgi_num``, specifies +the ID of the SGI. The second parameter, ``target``, must be the MPIDR of the +target PE. + +In case of Arm standard platforms using GIC, the implementation of the API +inserts barrier to make memory updates visible before raising SGI, then writes +to appropriate *SGI Register* in order to raise the EL3 SGI. + +Function: void plat_ic_set_spi_routing(unsigned int id, unsigned int routing_mode, u_register_t mpidr); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Argument : unsigned int + Argument : u_register_t + Return : void + +This API should set the routing mode of Share Peripheral Interrupt (SPI) +specified by first parameter ``id`` to that specified by the second parameter +``routing_mode``. + +The ``routing_mode`` parameter can be one of: + +- ``INTR_ROUTING_MODE_ANY`` means the interrupt can be routed to any PE in the + system. The ``mpidr`` parameter is ignored in this case. + +- ``INTR_ROUTING_MODE_PE`` means the interrupt is routed to the PE whose MPIDR + value is specified by the parameter ``mpidr``. + +In case of Arm standard platforms using GIC, the implementation of the API +writes to the GIC *Target Register* (GICv2) or *Route Register* (GICv3) to set +the routing. + +Function: void plat_ic_set_interrupt_pending(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : void + +This API should set the interrupt specified by first parameter ``id`` to +*Pending*. + +In case of Arm standard platforms using GIC, the implementation of the API +inserts barrier to make memory updates visible before setting interrupt pending, +and writes to the GIC *Set Pending Register* to set the interrupt pending +status. + +Function: void plat_ic_clear_interrupt_pending(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : void + +This API should clear the *Pending* status of the interrupt specified by first +parameter ``id``. + +In case of Arm standard platforms using GIC, the implementation of the API +writes to the GIC *Clear Pending Register* to clear the interrupt pending +status, and inserts barrier to make memory updates visible afterwards. + +Function: unsigned int plat_ic_set_priority_mask(unsigned int id); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : int + +This API should set the priority mask (first parameter) in the interrupt +controller such that only interrupts of higher priority than the supplied one +may be signalled to the PE. The API should return the current priority value +that it's overwriting. + +In case of Arm standard platforms using GIC, the implementation of the API +inserts to order memory updates before updating mask, then writes to the GIC +*Priority Mask Register*, and make sure memory updates are visible before +potential trigger due to mask update. + +.. _plat_ic_get_interrupt_id: + +Function: unsigned int plat_ic_get_interrupt_id(unsigned int raw); [optional] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + Argument : unsigned int + Return : unsigned int + +This API should extract and return the interrupt number from the raw value +obtained by the acknowledging the interrupt (read using +``plat_ic_acknowledge_interrupt()``). If the interrupt ID is invalid, this API +should return ``INTR_ID_UNAVAILABLE``. + +In case of Arm standard platforms using GIC, the implementation of the API +masks out the interrupt ID field from the acknowledged value from GIC. + +-------------- + +*Copyright (c) 2017-2023, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/ras.rst b/docs/components/ras.rst new file mode 100644 index 0000000..747367a --- /dev/null +++ b/docs/components/ras.rst @@ -0,0 +1,346 @@ +Reliability, Availability, and Serviceability (RAS) Extensions +************************************************************** + +This document describes |TF-A| support for Arm Reliability, Availability, and +Serviceability (RAS) extensions. RAS is a mandatory extension for Armv8.2 and +later CPUs, and also an optional extension to the base Armv8.0 architecture. + +For the description of Arm RAS extensions, Standard Error Records, and the +precise definition of RAS terminology, please refer to the Arm Architecture +Reference Manual and `RAS Supplement`_. The rest of this document assumes +familiarity with architecture and terminology. + +**IMPORTANT NOTE**: TF-A implementation assumes that if RAS extension is present +then FEAT_IESB is also implmented. + +There are two philosophies for handling RAS errors from Non-secure world point +of view. + +- :ref:`Firmware First Handling (FFH)` +- :ref:`Kernel First Handling (KFH)` + +.. _Firmware First Handling (FFH): + +Firmware First Handling (FFH) +============================= + +Introduction +------------ + +EA’s and Error interrupts corresponding to NS nodes are handled first in firmware + +- Errors signaled back to NS world via suitable mechanism +- Kernel is prohibited from accessing the RAS error records directly +- Firmware creates CPER records for kernel to navigate and process +- Firmware signals error back to Kernel via SDEI + +Overview +-------- + +FFH works in conjunction with `Exception Handling Framework`. Exceptions resulting from +errors in Non-secure world are routed to and handled in EL3. Said errors are Synchronous +External Abort (SEA), Asynchronous External Abort (signalled as SErrors), Fault Handling +and Error Recovery interrupts. +RAS Framework in TF-A allows the platform to define an external abort handler and to +register RAS nodes and interrupts. It also provides `helpers`__ for accessing Standard +Error Records as introduced by the RAS extensions + + +.. __: `Standard Error Record helpers`_ + +.. _Kernel First Handling (KFH): + +Kernel First Handling (KFH) +=========================== + +Introduction +------------ + +EA's originating/attributed to NS world are handled first in NS and Kernel navigates +the std error records directly. + +- KFH is the default handling mode if platform does not explicitly enable FFH mode. +- KFH mode does not need any EL3 involvement except for the reflection of errors back + to lower EL. This happens when there is an error (EA) in the system which is not yet + signaled to PE while executing at lower EL. During entry into EL3 the errors (EA) are + synchronized causing async EA to pend at EL3. + +Error Syncronization at EL3 entry +================================= + +During entry to EL3 from lower EL, if there is any pending async EAs they are either +reflected back to lower EL (KFH) or handled in EL3 itself (FFH). + +|Image 1| + +TF-A build options +================== + +- **ENABLE_FEAT_RAS**: Enable RAS extension feature at EL3. +- **HANDLE_EA_EL3_FIRST_NS**: Required for FFH +- **RAS_TRAP_NS_ERR_REC_ACCESS**: Trap Non-secure access of RAS error record registers. +- **RAS_EXTENSION**: Deprecated macro, equivalent to ENABLE_FEAT_RAS and + HANDLE_EA_EL3_FIRST_NS put together. + +RAS internal macros + +- **FFH_SUPPORT**: Gets enabled if **HANDLE_EA_EL3_FIRST_NS** is enabled. + +RAS feature has dependency on some other TF-A build flags + +- **EL3_EXCEPTION_HANDLING**: Required for FFH +- **FAULT_INJECTION_SUPPORT**: Required for testing RAS feature on fvp platform + +TF-A Tests +========== + +RAS functionality is regularly tested in TF-A CI using `RAS test group`_ which has multiple +configurations for testing lower EL External aborts. + +All the tests are written in TF-A tests which runs as NS-EL2 payload. + +- **FFH without RAS extension** + + *fvp-ea-ffh,fvp-ea-ffh:fvp-tftf-fip.tftf-aemv8a-debug* + + Couple of tests, one each for sync EA and async EA from lower EL which gets handled in El3. + Inject External aborts(sync/async) which traps in EL3, FVP has a handler which gracefully + handles these errors and returns back to TF-A Tests + + Build Configs : **HANDLE_EA_EL3_FIRST_NS** , **PLATFORM_TEST_EA_FFH** + +- **FFH with RAS extension** + + Three Tests : + + - *fvp-ras-ffh,fvp-single-fault:fvp-tftf-fip.tftf-aemv8a.fi-debug* + + Inject an unrecoverable RAS error, which gets handled in EL3. + + - *fvp-ras-ffh,fvp-uncontainable:fvp-tftf.fault-fip.tftf-aemv8a.fi-debug* + + Inject uncontainable RAS errors which causes platform to panic. + + - *fvp-ras-ffh,fvp-ras-ffh-nested:fvp-tftf-fip.tftf-ras_ffh_nested-aemv8a.fi-debug* + + Test nested exception handling at El3 for synchronized async EAs. Inject an SError in lower EL + which remain pending until we enter EL3 through SMC call. At EL3 entry on encountering a pending + async EA it will handle the async EA first (nested exception) before handling the original SMC call. + +- **KFH with RAS extension** + + Couple of tests in the group : + + - *fvp-ras-kfh,fvp-ras-kfh:fvp-tftf-fip.tftf-aemv8a.fi-debug* + + Inject and handle RAS errors in TF-A tests (no El3 involvement) + + - *fvp-ras-kfh,fvp-ras-kfh-reflect:fvp-tftf-fip.tftf-ras_kfh_reflection-aemv8a.fi-debug* + + Reflection of synchronized errors from EL3 to TF-A tests, two tests one each for reflecting + in IRQ and SMC path. + +RAS Framework +============= + + +.. _ras-figure: + +.. image:: ../resources/diagrams/draw.io/ras.svg + +Platform APIs +------------- + +The RAS framework allows the platform to define handlers for External Abort, +Uncontainable Errors, Double Fault, and errors rising from EL3 execution. Please +refer to :ref:`RAS Porting Guide <External Abort handling and RAS Support>`. + +Registering RAS error records +----------------------------- + +RAS nodes are components in the system capable of signalling errors to PEs +through one one of the notification mechanisms—SEAs, SErrors, or interrupts. RAS +nodes contain one or more error records, which are registers through which the +nodes advertise various properties of the signalled error. Arm recommends that +error records are implemented in the Standard Error Record format. The RAS +architecture allows for error records to be accessible via system or +memory-mapped registers. + +The platform should enumerate the error records providing for each of them: + +- A handler to probe error records for errors; +- When the probing identifies an error, a handler to handle it; +- For memory-mapped error record, its base address and size in KB; for a system + register-accessed record, the start index of the record and number of + continuous records from that index; +- Any node-specific auxiliary data. + +With this information supplied, when the run time firmware receives one of the +notification mechanisms, the RAS framework can iterate through and probe error +records for error, and invoke the appropriate handler to handle it. + +The RAS framework provides the macros to populate error record information. The +macros are versioned, and the latest version as of this writing is 1. These +macros create a structure of type ``struct err_record_info`` from its arguments, +which are later passed to probe and error handlers. + +For memory-mapped error records: + +.. code:: c + + ERR_RECORD_MEMMAP_V1(base_addr, size_num_k, probe, handler, aux) + +And, for system register ones: + +.. code:: c + + ERR_RECORD_SYSREG_V1(idx_start, num_idx, probe, handler, aux) + +The probe handler must have the following prototype: + +.. code:: c + + typedef int (*err_record_probe_t)(const struct err_record_info *info, + int *probe_data); + +The probe handler must return a non-zero value if an error was detected, or 0 +otherwise. The ``probe_data`` output parameter can be used to pass any useful +information resulting from probe to the error handler (see `below`__). For +example, it could return the index of the record. + +.. __: `Standard Error Record helpers`_ + +The error handler must have the following prototype: + +.. code:: c + + typedef int (*err_record_handler_t)(const struct err_record_info *info, + int probe_data, const struct err_handler_data *const data); + +The ``data`` constant parameter describes the various properties of the error, +including the reason for the error, exception syndrome, and also ``flags``, +``cookie``, and ``handle`` parameters from the :ref:`top-level exception handler +<EL3 interrupts>`. + +The platform is expected populate an array using the macros above, and register +the it with the RAS framework using the macro ``REGISTER_ERR_RECORD_INFO()``, +passing it the name of the array describing the records. Note that the macro +must be used in the same file where the array is defined. + +Standard Error Record helpers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The |TF-A| RAS framework provides probe handlers for Standard Error Records, for +both memory-mapped and System Register accesses: + +.. code:: c + + int ras_err_ser_probe_memmap(const struct err_record_info *info, + int *probe_data); + + int ras_err_ser_probe_sysreg(const struct err_record_info *info, + int *probe_data); + +When the platform enumerates error records, for those records in the Standard +Error Record format, these helpers maybe used instead of rolling out their own. +Both helpers above: + +- Return non-zero value when an error is detected in a Standard Error Record; +- Set ``probe_data`` to the index of the error record upon detecting an error. + +Registering RAS interrupts +-------------------------- + +RAS nodes can signal errors to the PE by raising Fault Handling and/or Error +Recovery interrupts. For the firmware-first handling paradigm for interrupts to +work, the platform must setup and register with |EHF|. See `Interaction with +Exception Handling Framework`_. + +For each RAS interrupt, the platform has to provide structure of type ``struct +ras_interrupt``: + +- Interrupt number; +- The associated error record information (pointer to the corresponding + ``struct err_record_info``); +- Optionally, a cookie. + +The platform is expected to define an array of ``struct ras_interrupt``, and +register it with the RAS framework using the macro +``REGISTER_RAS_INTERRUPTS()``, passing it the name of the array. Note that the +macro must be used in the same file where the array is defined. + +The array of ``struct ras_interrupt`` must be sorted in the increasing order of +interrupt number. This allows for fast look of handlers in order to service RAS +interrupts. + +Double-fault handling +--------------------- + +A Double Fault condition arises when an error is signalled to the PE while +handling of a previously signalled error is still underway. When a Double Fault +condition arises, the Arm RAS extensions only require for handler to perform +orderly shutdown of the system, as recovery may be impossible. + +The RAS extensions part of Armv8.4 introduced new architectural features to deal +with Double Fault conditions, specifically, the introduction of ``NMEA`` and +``EASE`` bits to ``SCR_EL3`` register. These were introduced to assist EL3 +software which runs part of its entry/exit routines with exceptions momentarily +masked—meaning, in such systems, External Aborts/SErrors are not immediately +handled when they occur, but only after the exceptions are unmasked again. + +|TF-A|, for legacy reasons, executes entire EL3 with all exceptions unmasked. +This means that all exceptions routed to EL3 are handled immediately. |TF-A| +thus is able to detect a Double Fault conditions in software, without needing +the intended advantages of Armv8.4 Double Fault architecture extensions. + +Double faults are fatal, and terminate at the platform double fault handler, and +doesn't return. + +Engaging the RAS framework +-------------------------- + +Enabling RAS support is a platform choice + +The RAS support in |TF-A| introduces a default implementation of +``plat_ea_handler``, the External Abort handler in EL3. When ``ENABLE_FEAT_RAS`` +is set to ``1``, it'll first call ``ras_ea_handler()`` function, which is the +top-level RAS exception handler. ``ras_ea_handler`` is responsible for iterating +to through platform-supplied error records, probe them, and when an error is +identified, look up and invoke the corresponding error handler. + +Note that, if the platform chooses to override the ``plat_ea_handler`` function +and intend to use the RAS framework, it must explicitly call +``ras_ea_handler()`` from within. + +Similarly, for RAS interrupts, the framework defines +``ras_interrupt_handler()``. The RAS framework arranges for it to be invoked +when a RAS interrupt taken at EL3. The function bisects the platform-supplied +sorted array of interrupts to look up the error record information associated +with the interrupt number. That error handler for that record is then invoked to +handle the error. + +Interaction with Exception Handling Framework +--------------------------------------------- + +As mentioned in earlier sections, RAS framework interacts with the |EHF| to +arbitrate handling of RAS exceptions with others that are routed to EL3. This +means that the platform must partition a :ref:`priority level <Partitioning +priority levels>` for handling RAS exceptions. The platform must then define +the macro ``PLAT_RAS_PRI`` to the priority level used for RAS exceptions. +Platforms would typically want to allocate the highest secure priority for +RAS handling. + +Handling of both :ref:`interrupt <interrupt-flow>` and :ref:`non-interrupt +<non-interrupt-flow>` exceptions follow the sequences outlined in the |EHF| +documentation. I.e., for interrupts, the priority management is implicit; but +for non-interrupt exceptions, they're explicit using :ref:`EHF APIs +<Activating and Deactivating priorities>`. + +-------------- + +*Copyright (c) 2018-2023, Arm Limited and Contributors. All rights reserved.* + +.. _RAS Supplement: https://developer.arm.com/documentation/ddi0587/latest +.. _RAS Test group: https://git.trustedfirmware.org/ci/tf-a-ci-scripts.git/tree/group/tf-l3-boot-tests-ras?h=refs/heads/master + +.. |Image 1| image:: ../resources/diagrams/bl31-exception-entry-error-synchronization.png diff --git a/docs/components/realm-management-extension.rst b/docs/components/realm-management-extension.rst new file mode 100644 index 0000000..f228e6b --- /dev/null +++ b/docs/components/realm-management-extension.rst @@ -0,0 +1,420 @@ + +Realm Management Extension (RME) +==================================== + +FEAT_RME (or RME for short) is an Armv9-A extension and is one component of the +`Arm Confidential Compute Architecture (Arm CCA)`_. TF-A supports RME starting +from version 2.6. This chapter discusses the changes to TF-A to support RME and +provides instructions on how to build and run TF-A with RME. + +RME support in TF-A +--------------------- + +The following diagram shows an Arm CCA software architecture with TF-A as the +EL3 firmware. In the Arm CCA architecture there are two additional security +states and address spaces: ``Root`` and ``Realm``. TF-A firmware runs in the +Root world. In the realm world, a Realm Management Monitor firmware (`RMM`_) +manages the execution of Realm VMs and their interaction with the hypervisor. + +.. image:: ../resources/diagrams/arm-cca-software-arch.png + +RME is the hardware extension to support Arm CCA. To support RME, various +changes have been introduced to TF-A. We discuss those changes below. + +Changes to translation tables library +*************************************** +RME adds Root and Realm Physical address spaces. To support this, two new +memory type macros, ``MT_ROOT`` and ``MT_REALM``, have been added to the +:ref:`Translation (XLAT) Tables Library`. These macros are used to configure +memory regions as Root or Realm respectively. + +.. note:: + + Only version 2 of the translation tables library supports the new memory + types. + +Changes to context management +******************************* +A new CPU context for the Realm world has been added. The existing +:ref:`CPU context management API<PSCI Library Integration guide for Armv8-A +AArch32 systems>` can be used to manage Realm context. + +Boot flow changes +******************* +In a typical TF-A boot flow, BL2 runs at Secure-EL1. However when RME is +enabled, TF-A runs in the Root world at EL3. Therefore, the boot flow is +modified to run BL2 at EL3 when RME is enabled. In addition to this, a +Realm-world firmware (`RMM`_) is loaded by BL2 in the Realm physical address +space. + +The boot flow when RME is enabled looks like the following: + +1. BL1 loads and executes BL2 at EL3 +2. BL2 loads images including RMM +3. BL2 transfers control to BL31 +4. BL31 initializes SPM (if SPM is enabled) +5. BL31 initializes RMM +6. BL31 transfers control to Normal-world software + +Granule Protection Tables (GPT) library +***************************************** +Isolation between the four physical address spaces is enforced by a process +called Granule Protection Check (GPC) performed by the MMU downstream any +address translation. GPC makes use of Granule Protection Table (GPT) in the +Root world that describes the physical address space assignment of every +page (granule). A GPT library that provides APIs to initialize GPTs and to +transition granules between different physical address spaces has been added. +More information about the GPT library can be found in the +:ref:`Granule Protection Tables Library` chapter. + +RMM Dispatcher (RMMD) +************************ +RMMD is a new standard runtime service that handles the switch to the Realm +world. It initializes the `RMM`_ and handles Realm Management Interface (RMI) +SMC calls from Non-secure. + +There is a contract between `RMM`_ and RMMD that defines the arguments that the +former needs to take in order to initialize and also the possible return values. +This contract is defined in the `RMM`_ Boot Interface, which can be found at +:ref:`rmm_el3_boot_interface`. + +There is also a specification of the runtime services provided by TF-A +to `RMM`_. This can be found at :ref:`runtime_services_and_interface`. + +Test Realm Payload (TRP) +************************* +TRP is a small test payload that runs at R-EL2 and implements a subset of +the Realm Management Interface (RMI) commands to primarily test EL3 firmware +and the interface between R-EL2 and EL3. When building TF-A with RME enabled, +if the path to an RMM image is not provided, TF-A builds the TRP by default +and uses it as the R-EL2 payload. + +Building and running TF-A with RME +---------------------------------- + +This section describes how you can build and run TF-A with RME enabled. +We assume you have read the :ref:`Prerequisites` to build TF-A. + +The following instructions show you how to build and run TF-A with RME +on FVP for two scenarios: + +- Three-world execution: This is the configuration to use if Secure + world functionality is not needed. TF-A is tested with the following + software entities in each world as listed below: + + - NS Host (RME capable Linux or TF-A Tests), + - Root (TF-A) + - R-EL2 (`RMM`_ or TRP) + +- Four-world execution: This is the configuration to use if both Secure + and Realm world functionality is needed. TF-A is tested with the following + software entities in each world as listed below: + + - NS Host (RME capable Linux or TF-A Tests), + - Root (TF-A) + - R-EL2 (`RMM`_ or TRP) + - S-EL2 (Hafnium SPM) + +To run the tests, you need an FVP model. Please use the :ref:`latest version +<Arm Fixed Virtual Platforms (FVP)>` of *FVP_Base_RevC-2xAEMvA* model. If NS +Host is Linux, then the below instructions assume that a suitable RME enabled +kernel image and associated root filesystem are available. + +Three-world execution +********************* + +**1. Clone and build RMM Image** + +Please refer to the `RMM Getting Started`_ on how to setup +Host Environment and build `RMM`_. The build commands assume that +an AArch64 toolchain and CMake executable are available in the +shell PATH variable and CROSS_COMPILE variable has been setup +appropriately. + +To clone `RMM`_ and build using the default build options for FVP: + +.. code:: shell + + git clone --recursive https://git.trustedfirmware.org/TF-RMM/tf-rmm.git + cd tf-rmm + cmake -DRMM_CONFIG=fvp_defcfg -S . -B build + cmake --build build + +This will generate **rmm.img** in **build/Release** folder. + +**2. Clone and build TF-A Tests with Realm Payload** + +This step is only needed if NS Host is TF-A Tests. The full set +of instructions to setup build host and build options for +TF-A-Tests can be found in the `TFTF Getting Started`_. TF-A Tests +can test Realm world with either `RMM`_ or TRP in R-EL2. In the TRP case, +some tests which are not applicable will be skipped. + +Use the following instructions to build TF-A with `TF-A Tests`_ as the +non-secure payload (BL33). + +.. code:: shell + + git clone https://git.trustedfirmware.org/TF-A/tf-a-tests.git + cd tf-a-tests + make CROSS_COMPILE=aarch64-none-elf- PLAT=fvp DEBUG=1 ENABLE_REALM_PAYLOAD_TESTS=1 all + +This produces a TF-A Tests binary (**tftf.bin**) with Realm payload packaged +and **sp_layout.json** in the **build/fvp/debug** directory. + + +**3. Build RME Enabled TF-A** + +The `TF-A Getting Started`_ has the necessary instructions to setup Host +machine and build TF-A. + +To build for RME, set ``ENABLE_RME`` build option to 1 and provide the path to +the `RMM`_ binary ``rmm.img`` using ``RMM`` build option. + +.. note:: + + ENABLE_RME build option is currently experimental. + +.. note:: + + If the ``RMM`` option is not specified, TF-A builds the TRP to load and + run at R-EL2. + +.. code:: shell + + git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git + cd trusted-firmware-a + make CROSS_COMPILE=aarch64-none-elf- \ + PLAT=fvp \ + ENABLE_RME=1 \ + RMM=<path/to/rmm.img> \ + FVP_HW_CONFIG_DTS=fdts/fvp-base-gicv3-psci-1t.dts \ + DEBUG=1 \ + BL33=<path/to/bl33> \ + all fip + +``BL33`` can point to a Non Secure Bootloader like UEFI/U-Boot or +the TF-A Tests binary(**tftf.bin**) from the previous step. + +This produces **bl1.bin** and **fip.bin** binaries in the **build/fvp/debug** +directory. + +TF-A can also directly boot Linux kernel on the FVP. The kernel needs to be +`preloaded` to a suitable memory location and this needs to be specified via +``PRELOADED_BL33_BASE`` build option. Also TF-A should implement the Linux +kernel register conventions for boot and this can be set using the +``ARM_LINUX_KERNEL_AS_BL33`` option. + +.. code-block:: shell + + cd trusted-firmware-a + make CROSS_COMPILE=aarch64-none-elf- \ + PLAT=fvp \ + ENABLE_RME=1 \ + RMM=<path/to/rmm.img> \ + FVP_HW_CONFIG_DTS=fdts/fvp-base-gicv3-psci-1t.dts \ + DEBUG=1 \ + ARM_LINUX_KERNEL_AS_BL33=1 \ + PRELOADED_BL33_BASE=0x84000000 \ + all fip + +The above command assumes that the Linux kernel will be placed in FVP +memory at 0x84000000 via suitable FVP option (see the next step). + +.. _fvp_3_world_cmd: + +**4. Running FVP for 3 world setup** + +Use the following command to run the tests on FVP. + +.. code:: shell + + FVP_Base_RevC-2xAEMvA \ + -C bp.refcounter.non_arch_start_at_default=1 \ + -C bp.secureflashloader.fname=<path/to/bl1.bin> \ + -C bp.flashloader0.fname=<path/to/fip.bin> \ + -C bp.refcounter.use_real_time=0 \ + -C bp.ve_sysregs.exit_on_shutdown=1 \ + -C cache_state_modelled=1 \ + -C bp.dram_size=4 \ + -C bp.secure_memory=1 \ + -C pci.pci_smmuv3.mmu.SMMU_ROOT_IDR0=3 \ + -C pci.pci_smmuv3.mmu.SMMU_ROOT_IIDR=0x43B \ + -C pci.pci_smmuv3.mmu.root_register_page_offset=0x20000 \ + -C cluster0.NUM_CORES=4 \ + -C cluster0.PA_SIZE=48 \ + -C cluster0.ecv_support_level=2 \ + -C cluster0.gicv3.cpuintf-mmap-access-level=2 \ + -C cluster0.gicv3.without-DS-support=1 \ + -C cluster0.gicv4.mask-virtual-interrupt=1 \ + -C cluster0.has_arm_v8-6=1 \ + -C cluster0.has_amu=1 \ + -C cluster0.has_branch_target_exception=1 \ + -C cluster0.rme_support_level=2 \ + -C cluster0.has_rndr=1 \ + -C cluster0.has_v8_7_pmu_extension=2 \ + -C cluster0.max_32bit_el=-1 \ + -C cluster0.stage12_tlb_size=1024 \ + -C cluster0.check_memory_attributes=0 \ + -C cluster0.ish_is_osh=1 \ + -C cluster0.restriction_on_speculative_execution=2 \ + -C cluster0.restriction_on_speculative_execution_aarch32=2 \ + -C cluster1.NUM_CORES=4 \ + -C cluster1.PA_SIZE=48 \ + -C cluster1.ecv_support_level=2 \ + -C cluster1.gicv3.cpuintf-mmap-access-level=2 \ + -C cluster1.gicv3.without-DS-support=1 \ + -C cluster1.gicv4.mask-virtual-interrupt=1 \ + -C cluster1.has_arm_v8-6=1 \ + -C cluster1.has_amu=1 \ + -C cluster1.has_branch_target_exception=1 \ + -C cluster1.rme_support_level=2 \ + -C cluster1.has_rndr=1 \ + -C cluster1.has_v8_7_pmu_extension=2 \ + -C cluster1.max_32bit_el=-1 \ + -C cluster1.stage12_tlb_size=1024 \ + -C cluster1.check_memory_attributes=0 \ + -C cluster1.ish_is_osh=1 \ + -C cluster1.restriction_on_speculative_execution=2 \ + -C cluster1.restriction_on_speculative_execution_aarch32=2 \ + -C pctl.startup=0.0.0.0 \ + -C bp.smsc_91c111.enabled=1 \ + -C bp.hostbridge.userNetworking=1 \ + -C bp.virtioblockdevice.image_path=<path/to/rootfs.ext4> + +The ``bp.virtioblockdevice.image_path`` option presents the rootfs as a +virtio block device to Linux kernel. It can be ignored if NS Host is +TF-A-Tests or rootfs is accessed by some other mechanism. + +If TF-A was built to expect a preloaded Linux kernel, then use the following +FVP argument to load the kernel image at the expected address. + +.. code-block:: shell + + --data cluster0.cpu0=<path_to_kernel_Image>@0x84000000 \ + + +.. tip:: + Tips to boot and run Linux faster on the FVP : + 1. Set the FVP option ``cache_state_modelled`` to 0. + 2. Disable the CPU Idle driver in Linux either by setting the kernel command line + parameter "cpuidle.off=1" or by disabling the ``CONFIG_CPU_IDLE`` kernel config. + +If the NS Host is TF-A-Tests, then the default test suite in TFTF +will execute on the FVP and this includes Realm world tests. The +tail of the output from *uart0* should look something like the following. + +.. code-block:: shell + + ... + + > Test suite 'FF-A Interrupt' + Passed + > Test suite 'SMMUv3 tests' + Passed + > Test suite 'PMU Leakage' + Passed + > Test suite 'DebugFS' + Passed + > Test suite 'RMI and SPM tests' + Passed + > Test suite 'Realm payload at EL1' + Passed + > Test suite 'Invalid memory access' + Passed + ... + +Four-world execution +******************** + +Four-world execution involves software components in each security state: root, +secure, realm and non-secure. This section describes how to build TF-A +with four-world support. + +We use TF-A as the root firmware, `Hafnium SPM`_ is the reference Secure world +component running at S-EL2. `RMM`_ can be built as described in previous +section. The examples below assume TF-A-Tests as the NS Host and utilize SPs +from TF-A-Tests. + +**1. Obtain and build Hafnium SPM** + +.. code:: shell + + git clone --recurse-submodules https://git.trustedfirmware.org/hafnium/hafnium.git + cd hafnium + # Use the default prebuilt LLVM/clang toolchain + PATH=$PWD/prebuilts/linux-x64/clang/bin:$PWD/prebuilts/linux-x64/dtc:$PATH + +Feature MTE needs to be disabled in Hafnium build, apply following patch to +project/reference submodule + +.. code:: diff + + diff --git a/BUILD.gn b/BUILD.gn + index cc6a78f..234b20a 100644 + --- a/BUILD.gn + +++ b/BUILD.gn + @@ -83,7 +83,6 @@ aarch64_toolchains("secure_aem_v8a_fvp") { + pl011_base_address = "0x1c090000" + smmu_base_address = "0x2b400000" + smmu_memory_size = "0x100000" + - enable_mte = "1" + plat_log_level = "LOG_LEVEL_INFO" + } + } + +.. code:: shell + + make PROJECT=reference + +The Hafnium binary should be located at +*out/reference/secure_aem_v8a_fvp_clang/hafnium.bin* + +**2. Build RME enabled TF-A with SPM** + +Build TF-A with RME as well as SPM enabled. + +Use the ``sp_layout.json`` previously generated in TF-A Tests +build to run SP tests. + +.. code:: shell + + make CROSS_COMPILE=aarch64-none-elf- \ + PLAT=fvp \ + ENABLE_RME=1 \ + FVP_HW_CONFIG_DTS=fdts/fvp-base-gicv3-psci-1t.dts \ + SPD=spmd \ + BRANCH_PROTECTION=1 \ + CTX_INCLUDE_PAUTH_REGS=1 \ + DEBUG=1 \ + SP_LAYOUT_FILE=<path/to/sp_layout.json> \ + BL32=<path/to/hafnium.bin> \ + BL33=<path/to/tftf.bin> \ + RMM=<path/to/rmm.img> \ + all fip + +**3. Running the FVP for a 4 world setup** + +Use the following arguments in addition to the FVP options mentioned in +:ref:`4. Running FVP for 3 world setup <fvp_3_world_cmd>` to run tests for +4 world setup. + +.. code:: shell + + -C pci.pci_smmuv3.mmu.SMMU_AIDR=2 \ + -C pci.pci_smmuv3.mmu.SMMU_IDR0=0x0046123B \ + -C pci.pci_smmuv3.mmu.SMMU_IDR1=0x00600002 \ + -C pci.pci_smmuv3.mmu.SMMU_IDR3=0x1714 \ + -C pci.pci_smmuv3.mmu.SMMU_IDR5=0xFFFF0475 \ + -C pci.pci_smmuv3.mmu.SMMU_S_IDR1=0xA0000002 \ + -C pci.pci_smmuv3.mmu.SMMU_S_IDR2=0 \ + -C pci.pci_smmuv3.mmu.SMMU_S_IDR3=0 + +.. _Arm Confidential Compute Architecture (Arm CCA): https://www.arm.com/why-arm/architecture/security-features/arm-confidential-compute-architecture +.. _Arm Architecture Models website: https://developer.arm.com/tools-and-software/simulation-models/fixed-virtual-platforms/arm-ecosystem-models +.. _TF-A Getting Started: https://trustedfirmware-a.readthedocs.io/en/latest/getting_started/index.html +.. _TF-A Tests: https://trustedfirmware-a-tests.readthedocs.io/en/latest +.. _TFTF Getting Started: https://trustedfirmware-a-tests.readthedocs.io/en/latest/getting_started/index.html +.. _Hafnium SPM: https://www.trustedfirmware.org/projects/hafnium +.. _RMM Getting Started: https://tf-rmm.readthedocs.io/en/latest/getting_started/index.html +.. _RMM: https://www.trustedfirmware.org/projects/tf-rmm/ diff --git a/docs/components/rmm-el3-comms-spec.rst b/docs/components/rmm-el3-comms-spec.rst new file mode 100644 index 0000000..009ac28 --- /dev/null +++ b/docs/components/rmm-el3-comms-spec.rst @@ -0,0 +1,591 @@ +RMM-EL3 Communication interface +******************************* + +This document defines the communication interface between RMM and EL3. +There are two parts in this interface: the boot interface and the runtime +interface. + +The Boot Interface defines the ABI between EL3 and RMM when the CPU enters +R-EL2 for the first time after boot. The cold boot interface defines the ABI +for the cold boot path and the warm boot interface defines the same for the +warm path. + +The RMM-EL3 runtime interface defines the ABI for EL3 services which can be +invoked by RMM as well as the register save-restore convention when handling an +SMC call from NS. + +The below sections discuss these interfaces more in detail. + +.. _rmm_el3_ifc_versioning: + +RMM-EL3 Interface versioning +____________________________ + +The RMM Boot and Runtime Interface uses a version number to check +compatibility with the register arguments passed as part of Boot Interface and +RMM-EL3 runtime interface. + +The Boot Manifest, discussed later in section :ref:`rmm_el3_boot_manifest`, +uses a separate version number but with the same scheme. + +The version number is a 32-bit type with the following fields: + +.. csv-table:: + :header: "Bits", "Value" + + [0:15],``VERSION_MINOR`` + [16:30],``VERSION_MAJOR`` + [31],RES0 + +The version numbers are sequentially increased and the rules for updating them +are explained below: + + - ``VERSION_MAJOR``: This value is increased when changes break + compatibility with previous versions. If the changes + on the ABI are compatible with the previous one, ``VERSION_MAJOR`` + remains unchanged. + + - ``VERSION_MINOR``: This value is increased on any change that is backwards + compatible with the previous version. When ``VERSION_MAJOR`` is increased, + ``VERSION_MINOR`` must be set to 0. + + - ``RES0``: Bit 31 of the version number is reserved 0 as to maintain + consistency with the versioning schemes used in other parts of RMM. + +This document specifies the 0.2 version of Boot Interface ABI and RMM-EL3 +services specification and the 0.2 version of the Boot Manifest. + +.. _rmm_el3_boot_interface: + +RMM Boot Interface +__________________ + +This section deals with the Boot Interface part of the specification. + +One of the goals of the Boot Interface is to allow EL3 firmware to pass +down into RMM certain platform specific information dynamically. This allows +RMM to be less platform dependent and be more generic across platform +variations. It also allows RMM to be decoupled from the other boot loader +images in the boot sequence and remain agnostic of any particular format used +for configuration files. + +The Boot Interface ABI defines a set of register conventions and +also a memory based manifest file to pass information from EL3 to RMM. The +Boot Manifest and the associated platform data in it can be dynamically created +by EL3 and there is no restriction on how the data can be obtained (e.g by DTB, +hoblist or other). + +The register convention and the manifest are versioned separately to manage +future enhancements and compatibility. + +RMM completes the boot by issuing the ``RMM_BOOT_COMPLETE`` SMC (0xC40001CF) +back to EL3. After the RMM has finished the boot process, it can only be +entered from EL3 as part of RMI handling. + +If RMM returns an error during boot (in any CPU), then RMM must not be entered +from any CPU. + +.. _rmm_cold_boot_interface: + +Cold Boot Interface +~~~~~~~~~~~~~~~~~~~ + +During cold boot RMM expects the following register values: + +.. csv-table:: + :header: "Register", "Value" + :widths: 1, 5 + + x0,Linear index of this PE. This index starts from 0 and must be less than the maximum number of CPUs to be supported at runtime (see x2). + x1,Version for this Boot Interface as defined in :ref:`rmm_el3_ifc_versioning`. + x2,Maximum number of CPUs to be supported at runtime. RMM should ensure that it can support this maximum number. + x3,Base address for the shared buffer used for communication between EL3 firmware and RMM. This buffer must be of 4KB size (1 page). The Boot Manifest must be present at the base of this shared buffer during cold boot. + +During cold boot, EL3 firmware needs to allocate a 4KB page that will be +passed to RMM in x3. This memory will be used as shared buffer for communication +between EL3 and RMM. It must be assigned to Realm world and must be mapped with +Normal memory attributes (IWB-OWB-ISH) at EL3. At boot, this memory will be +used to populate the Boot Manifest. Since the Boot Manifest can be accessed by +RMM prior to enabling its MMU, EL3 must ensure that proper cache maintenance +operations are performed after the Boot Manifest is populated. + +EL3 should also ensure that this shared buffer is always available for use by RMM +during the lifetime of the system and that it can be used for runtime +communication between RMM and EL3. For example, when RMM invokes attestation +service commands in EL3, this buffer can be used to exchange data between RMM +and EL3. It is also allowed for RMM to invoke runtime services provided by EL3 +utilizing this buffer during the boot phase, prior to return back to EL3 via +RMM_BOOT_COMPLETE SMC. + +RMM should map this memory page into its Stage 1 page-tables using Normal +memory attributes. + +During runtime, it is the RMM which initiates any communication with EL3. If that +communication requires the use of the shared area, it is expected that RMM needs +to do the necessary concurrency protection to prevent the use of the same buffer +by other PEs. + +The following sequence diagram shows how a generic EL3 Firmware would boot RMM. + +.. image:: ../resources/diagrams/rmm_cold_boot_generic.png + +Warm Boot Interface +~~~~~~~~~~~~~~~~~~~ + +At warm boot, RMM is already initialized and only some per-CPU initialization +is still pending. The only argument that is required by RMM at this stage is +the CPU Id, which will be passed through register x0 whilst x1 to x3 are RES0. +This is summarized in the following table: + +.. csv-table:: + :header: "Register", "Value" + :widths: 1, 5 + + x0,Linear index of this PE. This index starts from 0 and must be less than the maximum number of CPUs to be supported at runtime (see x2). + x1 - x3,RES0 + +Boot error handling and return values +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +After boot up and initialization, RMM returns control back to EL3 through a +``RMM_BOOT_COMPLETE`` SMC call. The only argument of this SMC call will +be returned in x1 and it will encode a signed integer with the error reason +as per the following table: + +.. csv-table:: + :header: "Error code", "Description", "ID" + :widths: 2 4 1 + + ``E_RMM_BOOT_SUCCESS``,Boot successful,0 + ``E_RMM_BOOT_ERR_UNKNOWN``,Unknown error,-1 + ``E_RMM_BOOT_VERSION_NOT_VALID``,Boot Interface version reported by EL3 is not supported by RMM,-2 + ``E_RMM_BOOT_CPUS_OUT_OF_RAGE``,Number of CPUs reported by EL3 larger than maximum supported by RMM,-3 + ``E_RMM_BOOT_CPU_ID_OUT_OF_RAGE``,Current CPU Id is higher or equal than the number of CPUs supported by RMM,-4 + ``E_RMM_BOOT_INVALID_SHARED_BUFFER``,Invalid pointer to shared memory area,-5 + ``E_RMM_BOOT_MANIFEST_VERSION_NOT_SUPPORTED``,Version reported by the Boot Manifest not supported by RMM,-6 + ``E_RMM_BOOT_MANIFEST_DATA_ERROR``,Error parsing core Boot Manifest,-7 + +For any error detected in RMM during cold or warm boot, RMM will return back to +EL3 using ``RMM_BOOT_COMPLETE`` SMC with an appropriate error code. It is +expected that EL3 will take necessary action to disable Realm world for further +entry from NS Host on receiving an error. This will be done across all the PEs +in the system so as to present a symmetric view to the NS Host. Any further +warm boot by any PE should not enter RMM using the warm boot interface. + +.. _rmm_el3_boot_manifest: + +Boot Manifest +~~~~~~~~~~~~~ + +During cold boot, EL3 Firmware passes a memory Boot Manifest to RMM containing +platform information. + +This Boot Manifest is versioned independently of the Boot Interface, to help +evolve the former independent of the latter. +The current version for the Boot Manifest is ``v0.2`` and the rules explained +in :ref:`rmm_el3_ifc_versioning` apply on this version as well. + +The Boot Manifest v0.2 has the following fields: + + - version : Version of the Manifest (v0.2) + - plat_data : Pointer to the platform specific data and not specified by this + document. These data are optional and can be NULL. + - plat_dram : Structure encoding the NS DRAM information on the platform. This + field is also optional and platform can choose to zero out this structure if + RMM does not need EL3 to send this information during the boot. + +For the current version of the Boot Manifest, the core manifest contains a pointer +to the platform data. EL3 must ensure that the whole Boot Manifest, including +the platform data, if available, fits inside the RMM EL3 shared buffer. + +For the data structure specification of Boot Manifest, refer to +:ref:`rmm_el3_manifest_struct` + +.. _runtime_services_and_interface: + +RMM-EL3 Runtime Interface +__________________________ + +This section defines the RMM-EL3 runtime interface which specifies the ABI for +EL3 services expected by RMM at runtime as well as the register save and +restore convention between EL3 and RMM as part of RMI call handling. It is +important to note that RMM is allowed to invoke EL3-RMM runtime interface +services during the boot phase as well. The EL3 runtime service handling must +not result in a world switch to another world unless specified. Both the RMM +and EL3 are allowed to make suitable optimizations based on this assumption. + +If the interface requires the use of memory, then the memory references should +be within the shared buffer communicated as part of the boot interface. See +:ref:`rmm_cold_boot_interface` for properties of this shared buffer which both +EL3 and RMM must adhere to. + +RMM-EL3 runtime service return codes +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The return codes from EL3 to RMM is a 32 bit signed integer which encapsulates +error condition as described in the following table: + +.. csv-table:: + :header: "Error code", "Description", "ID" + :widths: 2 4 1 + + ``E_RMM_OK``,No errors detected,0 + ``E_RMM_UNK``,Unknown/Generic error,-1 + ``E_RMM_BAD_ADDR``,The value of an address used as argument was invalid,-2 + ``E_RMM_BAD_PAS``,Incorrect PAS,-3 + ``E_RMM_NOMEM``,Not enough memory to perform an operation,-4 + ``E_RMM_INVAL``,The value of an argument was invalid,-5 + +If multiple failure conditions are detected in an RMM to EL3 command, then EL3 +is allowed to return an error code corresponding to any of the failure +conditions. + +RMM-EL3 runtime services +~~~~~~~~~~~~~~~~~~~~~~~~ + +The following table summarizes the RMM runtime services that need to be +implemented by EL3 Firmware. + +.. csv-table:: + :header: "FID", "Command" + :widths: 2 5 + + 0xC400018F,``RMM_RMI_REQ_COMPLETE`` + 0xC40001B0,``RMM_GTSI_DELEGATE`` + 0xC40001B1,``RMM_GTSI_UNDELEGATE`` + 0xC40001B2,``RMM_ATTEST_GET_REALM_KEY`` + 0xC40001B3,``RMM_ATTEST_GET_PLAT_TOKEN`` + +RMM_RMI_REQ_COMPLETE command +============================ + +Notifies the completion of an RMI call to the Non-Secure world. + +This call is the only function currently in RMM-EL3 runtime interface which +results in a world switch to NS. This call is the reply to the original RMI +call and it is forwarded by EL3 to the NS world. + +FID +--- + +``0xC400018F`` + +Input values +------------ + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + fid,x0,[63:0],UInt64,Command FID + err_code,x1,[63:0],RmiCommandReturnCode,Error code returned by the RMI service invoked by NS World. See Realm Management Monitor specification for more info + +Output values +------------- + +This call does not return. + +Failure conditions +------------------ + +Since this call does not return to RMM, there is no failure condition which +can be notified back to RMM. + +RMM_GTSI_DELEGATE command +========================= + +Delegate a memory granule by changing its PAS from Non-Secure to Realm. + +FID +--- + +``0xC40001B0`` + +Input values +------------ + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + fid,x0,[63:0],UInt64,Command FID + base_pa,x1,[63:0],Address,PA of the start of the granule to be delegated + +Output values +------------- + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 2 4 + + Result,x0,[63:0],Error Code,Command return status + +Failure conditions +------------------ + +The table below shows all the possible error codes returned in ``Result`` upon +a failure. The errors are ordered by condition check. + +.. csv-table:: + :header: "ID", "Condition" + :widths: 1 5 + + ``E_RMM_BAD_ADDR``,``PA`` does not correspond to a valid granule address + ``E_RMM_BAD_PAS``,The granule pointed by ``PA`` does not belong to Non-Secure PAS + ``E_RMM_OK``,No errors detected + +RMM_GTSI_UNDELEGATE command +=========================== + +Undelegate a memory granule by changing its PAS from Realm to Non-Secure. + +FID +--- + +``0xC40001B1`` + +Input values +------------ + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + fid,x0,[63:0],UInt64,Command FID + base_pa,x1,[63:0],Address,PA of the start of the granule to be undelegated + +Output values +------------- + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 2 4 + + Result,x0,[63:0],Error Code,Command return status + +Failure conditions +------------------ + +The table below shows all the possible error codes returned in ``Result`` upon +a failure. The errors are ordered by condition check. + +.. csv-table:: + :header: "ID", "Condition" + :widths: 1 5 + + ``E_RMM_BAD_ADDR``,``PA`` does not correspond to a valid granule address + ``E_RMM_BAD_PAS``,The granule pointed by ``PA`` does not belong to Realm PAS + ``E_RMM_OK``,No errors detected + +RMM_ATTEST_GET_REALM_KEY command +================================ + +Retrieve the Realm Attestation Token Signing key from EL3. + +FID +--- + +``0xC40001B2`` + +Input values +------------ + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + fid,x0,[63:0],UInt64,Command FID + buf_pa,x1,[63:0],Address,PA where the Realm Attestation Key must be stored by EL3. The PA must belong to the shared buffer + buf_size,x2,[63:0],Size,Size in bytes of the Realm Attestation Key buffer. ``bufPa + bufSize`` must lie within the shared buffer + ecc_curve,x3,[63:0],Enum,Type of the elliptic curve to which the requested attestation key belongs to. See :ref:`ecc_curves` + +Output values +------------- + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + Result,x0,[63:0],Error Code,Command return status + keySize,x1,[63:0],Size,Size of the Realm Attestation Key + +Failure conditions +------------------ + +The table below shows all the possible error codes returned in ``Result`` upon +a failure. The errors are ordered by condition check. + +.. csv-table:: + :header: "ID", "Condition" + :widths: 1 5 + + ``E_RMM_BAD_ADDR``,``PA`` is outside the shared buffer + ``E_RMM_INVAL``,``PA + BSize`` is outside the shared buffer + ``E_RMM_INVAL``,``Curve`` is not one of the listed in :ref:`ecc_curves` + ``E_RMM_UNK``,An unknown error occurred whilst processing the command + ``E_RMM_OK``,No errors detected + +.. _ecc_curves: + +Supported ECC Curves +-------------------- + +.. csv-table:: + :header: "ID", "Curve" + :widths: 1 5 + + 0,ECC SECP384R1 + +RMM_ATTEST_GET_PLAT_TOKEN command +================================= + +Retrieve the Platform Token from EL3. + +FID +--- + +``0xC40001B3`` + +Input values +------------ + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + fid,x0,[63:0],UInt64,Command FID + buf_pa,x1,[63:0],Address,PA of the platform attestation token. The challenge object is passed in this buffer. The PA must belong to the shared buffer + buf_size,x2,[63:0],Size,Size in bytes of the platform attestation token buffer. ``bufPa + bufSize`` must lie within the shared buffer + c_size,x3,[63:0],Size,Size in bytes of the challenge object. It corresponds to the size of one of the defined SHA algorithms + +Output values +------------- + +.. csv-table:: + :header: "Name", "Register", "Field", "Type", "Description" + :widths: 1 1 1 1 5 + + Result,x0,[63:0],Error Code,Command return status + tokenSize,x1,[63:0],Size,Size of the platform token + +Failure conditions +------------------ + +The table below shows all the possible error codes returned in ``Result`` upon +a failure. The errors are ordered by condition check. + +.. csv-table:: + :header: "ID", "Condition" + :widths: 1 5 + + ``E_RMM_BAD_ADDR``,``PA`` is outside the shared buffer + ``E_RMM_INVAL``,``PA + BSize`` is outside the shared buffer + ``E_RMM_INVAL``,``CSize`` does not represent the size of a supported SHA algorithm + ``E_RMM_UNK``,An unknown error occurred whilst processing the command + ``E_RMM_OK``,No errors detected + +RMM-EL3 world switch register save restore convention +_____________________________________________________ + +As part of NS world switch, EL3 is expected to maintain a register context +specific to each world and will save and restore the registers +appropriately. This section captures the contract between EL3 and RMM on the +register set to be saved and restored. + +EL3 must maintain a separate register context for the following: + + #. General purpose registers (x0-x30) and ``sp_el0``, ``sp_el2`` stack pointers + #. EL2 system register context for all enabled features by EL3. These include system registers with the ``_EL2`` prefix. The EL2 physical and virtual timer registers must not be included in this. + +As part of SMC forwarding between the NS world and Realm world, EL3 allows x0-x7 to be passed +as arguments to Realm and x0-x4 to be used for return arguments back to Non Secure. +As per SMCCCv1.2, x4 must be preserved if not being used as return argument by the SMC function +and it is the responsibility of RMM to preserve this or use this as a return argument. +EL3 will always copy x0-x4 from Realm context to NS Context. + +EL3 must save and restore the following as part of world switch: + #. EL2 system registers with the exception of ``zcr_el2`` register. + #. PAuth key registers (APIA, APIB, APDA, APDB, APGA). + +EL3 will not save some registers as mentioned in the below list. It is the +responsibility of RMM to ensure that these are appropriately saved if the +Realm World makes use of them: + + #. FP/SIMD registers + #. SVE registers + #. SME registers + #. EL1/0 registers with the exception of PAuth key registers as mentioned above. + #. zcr_el2 register. + +It is essential that EL3 honors this contract to maintain the Confidentiality and integrity +of the Realm world. + +SMCCC v1.3 allows NS world to specify whether SVE context is in use. In this +case, RMM could choose to not save the incoming SVE context but must ensure +to clear SVE registers if they have been used in Realm World. The same applies +to SME registers. + +Types +_____ + +.. _rmm_el3_manifest_struct: + +RMM-EL3 Boot Manifest structure +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The RMM-EL3 Boot Manifest v0.2 structure contains platform boot information passed +from EL3 to RMM. The size of the Boot Manifest is 40 bytes. + +The members of the RMM-EL3 Boot Manifest structure are shown in the following +table: + ++-----------+--------+----------------+----------------------------------------+ +| Name | Offset | Type | Description | ++===========+========+================+========================================+ +| version | 0 | uint32_t | Boot Manifest version | ++-----------+--------+----------------+----------------------------------------+ +| padding | 4 | uint32_t | Reserved, set to 0 | ++-----------+--------+----------------+----------------------------------------+ +| plat_data | 8 | uintptr_t | Pointer to Platform Data section | ++-----------+--------+----------------+----------------------------------------+ +| plat_dram | 16 | ns_dram_info | NS DRAM Layout Info structure | ++-----------+--------+----------------+----------------------------------------+ + +.. _ns_dram_info_struct: + +NS DRAM Layout Info structure +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +NS DRAM Layout Info structure contains information about platform Non-secure +DRAM layout. The members of this structure are shown in the table below: + ++-----------+--------+----------------+----------------------------------------+ +| Name | Offset | Type | Description | ++===========+========+================+========================================+ +| num_banks | 0 | uint64_t | Number of NS DRAM banks | ++-----------+--------+----------------+----------------------------------------+ +| banks | 8 | ns_dram_bank * | Pointer to 'ns_dram_bank'[] array | ++-----------+--------+----------------+----------------------------------------+ +| checksum | 16 | uint64_t | Checksum | ++-----------+--------+----------------+----------------------------------------+ + +Checksum is calculated as two's complement sum of 'num_banks', 'banks' pointer +and DRAM banks data array pointed by it. + +.. _ns_dram_bank_struct: + +NS DRAM Bank structure +~~~~~~~~~~~~~~~~~~~~~~ + +NS DRAM Bank structure contains information about each Non-secure DRAM bank: + ++-----------+--------+----------------+----------------------------------------+ +| Name | Offset | Type | Description | ++===========+========+================+========================================+ +| base | 0 | uintptr_t | Base address | ++-----------+--------+----------------+----------------------------------------+ +| size | 8 | uint64_t | Size of bank in bytes | ++-----------+--------+----------------+----------------------------------------+ + + + diff --git a/docs/components/romlib-design.rst b/docs/components/romlib-design.rst new file mode 100644 index 0000000..d34b3cc --- /dev/null +++ b/docs/components/romlib-design.rst @@ -0,0 +1,155 @@ +Library at ROM +============== + +This document provides an overview of the "library at ROM" implementation in +Trusted Firmware-A (TF-A). + +Introduction +~~~~~~~~~~~~ + +The "library at ROM" feature allows platforms to build a library of functions to +be placed in ROM. This reduces SRAM usage by utilising the available space in +ROM. The "library at ROM" contains a jump table with the list of functions that +are placed in ROM. The capabilities of the "library at ROM" are: + +1. Functions can be from one or several libraries. + +2. Functions can be patched after they have been programmed into ROM. + +3. Platform-specific libraries can be placed in ROM. + +4. Functions can be accessed by one or more BL images. + +Index file +~~~~~~~~~~ + +.. image:: ../resources/diagrams/romlib_design.png + :width: 600 + +Library at ROM is described by an index file with the list of functions to be +placed in ROM. The index file is platform specific and its format is: + +:: + + lib function [patch] + + lib -- Name of the library the function belongs to + function -- Name of the function to be placed in library at ROM + [patch] -- Option to patch the function + +It is also possible to insert reserved spaces in the list by using the keyword +"reserved" rather than the "lib" and "function" names as shown below: + +:: + + reserved + +The reserved spaces can be used to add more functions in the future without +affecting the order and location of functions already existing in the jump +table. Also, for additional flexibility and modularity, the index file can +include other index files. + +For an index file example, refer to ``lib/romlib/jmptbl.i``. + +Wrapper functions +~~~~~~~~~~~~~~~~~ + +.. image:: ../resources/diagrams/romlib_wrapper.png + :width: 600 + +When invoking a function of the "library at ROM", the calling sequence is as +follows: + +BL image --> wrapper function --> jump table entry --> library at ROM + +The index file is used to create a jump table which is placed in ROM. Then, the +wrappers refer to the jump table to call the "library at ROM" functions. The +wrappers essentially contain a branch instruction to the jump table entry +corresponding to the original function. Finally, the original function in the BL +image(s) is replaced with the wrapper function. + +The "library at ROM" contains a necessary init function that initialises the +global variables defined by the functions inside "library at ROM". + +Script +~~~~~~ + +There is a ``romlib_generate.py`` Python script that generates the necessary +files for the "library at ROM" to work. It implements multiple functions: + +1. ``romlib_generate.py gentbl [args]`` - Generates the jump table by parsing + the index file. + +2. ``romlib_generator.py genvar [args]`` - Generates the jump table global + variable (**not** the jump table itself) with the absolute address in ROM. + This global variable is, basically, a pointer to the jump table. + +3. ``romlib_generator.py genwrappers [args]`` - Generates a wrapper function for + each entry in the index file except for the ones that contain the keyword + ``patch``. The generated wrapper file is called ``<fn_name>.s``. + +4. ``romlib_generator.py pre [args]`` - Preprocesses the index file which means + it resolves all the include commands in the file recursively. It can also + generate a dependency file of the included index files which can be directly + used in makefiles. + +Each ``romlib_generate.py`` function has its own manual which is accessible by +runing ``romlib_generator.py [function] --help``. + +``romlib_generate.py`` requires Python 3 environment. + + +Patching of functions in library at ROM +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``romlib_generator.py genwrappers`` does not generate wrappers for the +entries in the index file that contain the keyword ``patch``. Thus, it allows +calling the function from the actual library by breaking the link to the +"library at ROM" version of this function. + +The calling sequence for a patched function is as follows: + +BL image --> function + +Memory impact +~~~~~~~~~~~~~ + +Using library at ROM will modify the memory layout of the BL images: + +- The ROM library needs a page aligned RAM section to hold the RW data. This + section is defined by the ROMLIB_RW_BASE and ROMLIB_RW_END macros. + On Arm platforms a section of 1 page (0x1000) is allocated at the top of SRAM. + This will have for effect to shift down all the BL images by 1 page. + +- Depending on the functions moved to the ROM library, the size of the BL images + will be reduced. + For example: moving MbedTLS function into the ROM library reduces BL1 and + BL2, but not BL31. + +- This change in BL images size can be taken into consideration to optimize the + memory layout when defining the BLx_BASE macros. + +Build library at ROM +~~~~~~~~~~~~~~~~~~~~~ + +The environment variable ``CROSS_COMPILE`` must be set appropriately. Refer to +:ref:`Performing an Initial Build` for more information about setting this +variable. + +In the below example the usage of ROMLIB together with mbed TLS is demonstrated +to showcase the benefits of library at ROM - it's not mandatory. + +.. code:: shell + + make PLAT=fvp \ + MBEDTLS_DIR=</path/to/mbedtls/> \ + TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 \ + ARM_ROTPK_LOCATION=devel_rsa \ + ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem \ + BL33=</path/to/bl33.bin> \ + USE_ROMLIB=1 \ + all fip + +-------------- + +*Copyright (c) 2019, Arm Limited. All rights reserved.* diff --git a/docs/components/sdei.rst b/docs/components/sdei.rst new file mode 100644 index 0000000..60259c8 --- /dev/null +++ b/docs/components/sdei.rst @@ -0,0 +1,369 @@ +SDEI: Software Delegated Exception Interface +============================================ + +This document provides an overview of the SDEI dispatcher implementation in +Trusted Firmware-A (TF-A). + +Introduction +------------ + +Software Delegated Exception Interface (|SDEI|) is an Arm specification for +Non-secure world to register handlers with firmware to receive notifications +about system events. Firmware will first receive the system events by way of +asynchronous exceptions and, in response, arranges for the registered handler to +execute in the Non-secure EL. + +Normal world software that interacts with the SDEI dispatcher (makes SDEI +requests and receives notifications) is referred to as the *SDEI Client*. A +client receives the event notification at the registered handler even when it +was executing with exceptions masked. The list of SDEI events available to the +client are specific to the platform [#std-event]_. See also `Determining client +EL`_. + +.. _general SDEI dispatch: + +The following figure depicts a general sequence involving SDEI client executing +at EL2 and an event dispatch resulting from the triggering of a bound interrupt. +A commentary is provided below: + +.. uml:: ../resources/diagrams/plantuml/sdei_general.puml + +As part of initialisation, the SDEI client binds a Non-secure interrupt [1], and +the SDEI dispatcher returns a platform dynamic event number [2]. The client then +registers a handler for that event [3], enables the event [5], and unmasks all +events on the current PE [7]. This sequence is typical of an SDEI client, but it +may involve additional SDEI calls. + +At a later point in time, when the bound interrupt triggers [9], it's trapped to +EL3. The interrupt is handed over to the SDEI dispatcher, which then arranges to +execute the registered handler [10]. The client terminates its execution with +``SDEI_EVENT_COMPLETE`` [11], following which the dispatcher resumes the +original EL2 execution [13]. Note that the SDEI interrupt remains active until +the client handler completes, at which point EL3 does EOI [12]. + +Other than events bound to interrupts, as depicted in the sequence above, SDEI +events can be explicitly dispatched in response to other exceptions, for +example, upon receiving an *SError* or *Synchronous External Abort*. See +`Explicit dispatch of events`_. + +The remainder of this document only discusses the design and implementation of +SDEI dispatcher in TF-A, and assumes that the reader is familiar with the SDEI +specification, the interfaces, and their requirements. + +Defining events +--------------- + +A platform choosing to include the SDEI dispatcher must also define the events +available on the platform, along with their attributes. + +The platform is expected to provide two arrays of event descriptors: one for +private events, and another for shared events. The SDEI dispatcher provides +``SDEI_PRIVATE_EVENT()`` and ``SDEI_SHARED_EVENT()`` macros to populate the +event descriptors. Both macros take 3 arguments: + +- The event number: this must be a positive 32-bit integer. + +- For an event that has a backing interrupt, the interrupt number the event is + bound to: + + - If it's not applicable to an event, this shall be left as ``0``. + + - If the event is dynamic, this should be specified as ``SDEI_DYN_IRQ``. + +- A bit map of `Event flags`_. + +To define event 0, the macro ``SDEI_DEFINE_EVENT_0()`` should be used. This +macro takes only one parameter: an SGI number to signal other PEs. + +To define an event that's meant to be explicitly dispatched (i.e., not as a +result of receiving an SDEI interrupt), the macro ``SDEI_EXPLICIT_EVENT()`` +should be used. It accepts two parameters: + +- The event number (as above); + +- Event priority: ``SDEI_MAPF_CRITICAL`` or ``SDEI_MAPF_NORMAL``, as described + below. + +Once the event descriptor arrays are defined, they should be exported to the +SDEI dispatcher using the ``REGISTER_SDEI_MAP()`` macro, passing it the pointers +to the private and shared event descriptor arrays, respectively. Note that the +``REGISTER_SDEI_MAP()`` macro must be used in the same file where the arrays are +defined. + +Regarding event descriptors: + +- For Event 0: + + - There must be exactly one descriptor in the private array, and none in the + shared array. + + - The event should be defined using ``SDEI_DEFINE_EVENT_0()``. + + - Must be bound to a Secure SGI on the platform. + +- Explicit events should only be used in the private array. + +- Statically bound shared and private interrupts must be bound to shared and + private interrupts on the platform, respectively. See the section on + `Configuration within Exception Handling Framework`_. + +- Both arrays should be one-dimensional. The ``REGISTER_SDEI_MAP()`` macro + takes care of replicating private events for each PE on the platform. + +- Both arrays must be sorted in the increasing order of event number. + +The SDEI specification doesn't have provisions for discovery of available events +on the platform. The list of events made available to the client, along with +their semantics, have to be communicated out of band; for example, through +Device Trees or firmware configuration tables. + +See also `Event definition example`_. + +Event flags +~~~~~~~~~~~ + +Event flags describe the properties of the event. They are bit maps that can be +``OR``\ ed to form parameters to macros that define events (see +`Defining events`_). + +- ``SDEI_MAPF_DYNAMIC``: Marks the event as dynamic. Dynamic events can be + bound to (or released from) any Non-secure interrupt at runtime via the + ``SDEI_INTERRUPT_BIND`` and ``SDEI_INTERRUPT_RELEASE`` calls. + +- ``SDEI_MAPF_BOUND``: Marks the event as statically bound to an interrupt. + These events cannot be re-bound at runtime. + +- ``SDEI_MAPF_NORMAL``: Marks the event as having *Normal* priority. This is + the default priority. + +- ``SDEI_MAPF_CRITICAL``: Marks the event as having *Critical* priority. + +Event definition example +------------------------ + +.. code:: c + + static sdei_ev_map_t plat_private_sdei[] = { + /* Event 0 definition */ + SDEI_DEFINE_EVENT_0(8), + + /* PPI */ + SDEI_PRIVATE_EVENT(8, 23, SDEI_MAPF_BOUND), + + /* Dynamic private events */ + SDEI_PRIVATE_EVENT(100, SDEI_DYN_IRQ, SDEI_MAPF_DYNAMIC), + SDEI_PRIVATE_EVENT(101, SDEI_DYN_IRQ, SDEI_MAPF_DYNAMIC) + + /* Events for explicit dispatch */ + SDEI_EXPLICIT_EVENT(2000, SDEI_MAPF_NORMAL); + SDEI_EXPLICIT_EVENT(2000, SDEI_MAPF_CRITICAL); + }; + + /* Shared event mappings */ + static sdei_ev_map_t plat_shared_sdei[] = { + SDEI_SHARED_EVENT(804, 0, SDEI_MAPF_DYNAMIC), + + /* Dynamic shared events */ + SDEI_SHARED_EVENT(3000, SDEI_DYN_IRQ, SDEI_MAPF_DYNAMIC), + SDEI_SHARED_EVENT(3001, SDEI_DYN_IRQ, SDEI_MAPF_DYNAMIC) + }; + + /* Export SDEI events */ + REGISTER_SDEI_MAP(plat_private_sdei, plat_shared_sdei); + +Configuration within Exception Handling Framework +------------------------------------------------- + +The SDEI dispatcher functions alongside the Exception Handling Framework. This +means that the platform must assign priorities to both Normal and Critical SDEI +interrupts for the platform: + +- Install priority descriptors for Normal and Critical SDEI interrupts. + +- For those interrupts that are statically bound (i.e. events defined as having + the ``SDEI_MAPF_BOUND`` property), enumerate their properties for the GIC + driver to configure interrupts accordingly. + + The interrupts must be configured to target EL3. This means that they should + be configured as *Group 0*. Additionally, on GICv2 systems, the build option + ``GICV2_G0_FOR_EL3`` must be set to ``1``. + +See also :ref:`porting_guide_sdei_requirements`. + +Determining client EL +--------------------- + +The SDEI specification requires that the *physical* SDEI client executes in the +highest Non-secure EL implemented on the system. This means that the dispatcher +will only allow SDEI calls to be made from: + +- EL2, if EL2 is implemented. The Hypervisor is expected to implement a + *virtual* SDEI dispatcher to support SDEI clients in Guest Operating Systems + executing in Non-secure EL1. + +- Non-secure EL1, if EL2 is not implemented or disabled. + +See the function ``sdei_client_el()`` in ``sdei_private.h``. + +.. _explicit-dispatch-of-events: + +Explicit dispatch of events +--------------------------- + +Typically, an SDEI event dispatch is caused by the PE receiving interrupts that +are bound to an SDEI event. However, there are cases where the Secure world +requires dispatch of an SDEI event as a direct or indirect result of a past +activity, such as receiving a Secure interrupt or an exception. + +The SDEI dispatcher implementation provides ``sdei_dispatch_event()`` API for +this purpose. The API has the following signature: + +.. code:: c + + int sdei_dispatch_event(int ev_num); + +The parameter ``ev_num`` is the event number to dispatch. The API returns ``0`` +on success, or ``-1`` on failure. + +The following figure depicts a scenario involving explicit dispatch of SDEI +event. A commentary is provided below: + +.. uml:: ../resources/diagrams/plantuml/sdei_explicit_dispatch.puml + +As part of initialisation, the SDEI client registers a handler for a platform +event [1], enables the event [3], and unmasks the current PE [5]. Note that, +unlike in `general SDEI dispatch`_, this doesn't involve interrupt binding, as +bound or dynamic events can't be explicitly dispatched (see the section below). + +At a later point in time, a critical event [#critical-event]_ is trapped into +EL3 [7]. EL3 performs a first-level triage of the event, and a RAS component +assumes further handling [8]. The dispatch completes, but intends to involve +Non-secure world in further handling, and therefore decides to explicitly +dispatch an event [10] (which the client had already registered for [1]). The +rest of the sequence is similar to that in the `general SDEI dispatch`_: the +requested event is dispatched to the client (assuming all the conditions are +met), and when the handler completes, the preempted execution resumes. + +Conditions for event dispatch +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +All of the following requirements must be met for the API to return ``0`` and +event to be dispatched: + +- SDEI events must be unmasked on the PE. I.e. the client must have called + ``PE_UNMASK`` beforehand. + +- Event 0 can't be dispatched. + +- The event must be declared using the ``SDEI_EXPLICIT_EVENT()`` macro + described above. + +- The event must be private to the PE. + +- The event must have been registered for and enabled. + +- A dispatch for the same event must not be outstanding. I.e. it hasn't already + been dispatched and is yet to be completed. + +- The priority of the event (either Critical or Normal, as configured by the + platform at build-time) shouldn't cause priority inversion. This means: + + - If it's of Normal priority, neither Normal nor Critical priority dispatch + must be outstanding on the PE. + + - If it's of a Critical priority, no Critical priority dispatch must be + outstanding on the PE. + +Further, the caller should be aware of the following assumptions made by the +dispatcher: + +- The caller of the API is a component running in EL3; for example, a RAS + driver. + +- The requested dispatch will be permitted by the Exception Handling Framework. + I.e. the caller must make sure that the requested dispatch has sufficient + priority so as not to cause priority level inversion within Exception + Handling Framework. + +- The caller must be prepared for the SDEI dispatcher to restore the Non-secure + context, and mark that the active context. + +- The call will block until the SDEI client completes the event (i.e. when the + client calls either ``SDEI_EVENT_COMPLETE`` or ``SDEI_COMPLETE_AND_RESUME``). + +- The caller must be prepared for this API to return failure and handle + accordingly. + +Porting requirements +-------------------- + +The porting requirements of the SDEI dispatcher are outlined in the +:ref:`Porting Guide <porting_guide_sdei_requirements>`. + +Note on writing SDEI event handlers +----------------------------------- + +*This section pertains to SDEI event handlers in general, not just when using +the TF-A SDEI dispatcher.* + +The SDEI specification requires that event handlers preserve the contents of all +registers except ``x0`` to ``x17``. This has significance if event handler is +written in C: compilers typically adjust the stack frame at the beginning and +end of C functions. For example, AArch64 GCC typically produces the following +function prologue and epilogue: + +:: + + c_event_handler: + stp x29, x30, [sp,#-32]! + mov x29, sp + + ... + + bl ... + + ... + + ldp x29, x30, [sp],#32 + ret + +The register ``x29`` is used as frame pointer in the prologue. Because neither a +valid ``SDEI_EVENT_COMPLETE`` nor ``SDEI_EVENT_COMPLETE_AND_RESUME`` calls +return to the handler, the epilogue never gets executed, and registers ``x29`` +and ``x30`` (in the case above) are inadvertently corrupted. This violates the +SDEI specification, and the normal execution thereafter will result in +unexpected behaviour. + +To work this around, it's advised that the top-level event handlers are +implemented in assembly, following a similar pattern as below: + +:: + + asm_event_handler: + /* Save link register whilst maintaining stack alignment */ + stp xzr, x30, [sp, #-16]! + bl c_event_handler + + /* Restore link register */ + ldp xzr, x30, [sp], #16 + + /* Complete call */ + ldr x0, =SDEI_EVENT_COMPLETE + smc #0 + b . + +-------------- + +*Copyright (c) 2017-2019, Arm Limited and Contributors. All rights reserved.* + +.. rubric:: Footnotes + +.. [#std-event] Except event 0, which is defined by the SDEI specification as a + standard event. + +.. [#critical-event] Examples of critical events are *SError*, *Synchronous + External Abort*, *Fault Handling interrupt* or *Error + Recovery interrupt* from one of RAS nodes in the system. + +.. _SDEI specification: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf +.. _Software Delegated Exception Interface: `SDEI specification`_ diff --git a/docs/components/secure-partition-manager-mm.rst b/docs/components/secure-partition-manager-mm.rst new file mode 100644 index 0000000..d9b2b1b --- /dev/null +++ b/docs/components/secure-partition-manager-mm.rst @@ -0,0 +1,827 @@ +Secure Partition Manager (MM) +***************************** + +Foreword +======== + +This document describes the implementation where the Secure Partition Manager +resides at EL3 and management services run from isolated Secure Partitions at +S-EL0. The communication protocol is established through the Management Mode +(MM) interface. + +Background +========== + +In some market segments that primarily deal with client-side devices like mobile +phones, tablets, STBs and embedded devices, a Trusted OS instantiates trusted +applications to provide security services like DRM, secure payment and +authentication. The Global Platform TEE Client API specification defines the API +used by Non-secure world applications to access these services. A Trusted OS +fulfils the requirements of a security service as described above. + +Management services are typically implemented at the highest level of privilege +in the system, i.e. EL3 in Trusted Firmware-A (TF-A). The service requirements are +fulfilled by the execution environment provided by TF-A. + +The following diagram illustrates the corresponding software stack: + +|Image 1| + +In other market segments that primarily deal with server-side devices (e.g. data +centres and enterprise servers) the secure software stack typically does not +include a Global Platform Trusted OS. Security functions are accessed through +other interfaces (e.g. ACPI TCG TPM interface, UEFI runtime variable service). + +Placement of management and security functions with diverse requirements in a +privileged Exception Level (i.e. EL3 or S-EL1) makes security auditing of +firmware more difficult and does not allow isolation of unrelated services from +each other either. + +Introduction +============ + +A **Secure Partition** is a software execution environment instantiated in +S-EL0 that can be used to implement simple management and security services. +Since S-EL0 is an unprivileged Exception Level, a Secure Partition relies on +privileged firmware (i.e. TF-A) to be granted access to system and processor +resources. Essentially, it is a software sandbox in the Secure world that runs +under the control of privileged software, provides one or more services and +accesses the following system resources: + +- Memory and device regions in the system address map. + +- PE system registers. + +- A range of synchronous exceptions (e.g. SMC function identifiers). + +Note that currently TF-A only supports handling one Secure Partition. + +A Secure Partition enables TF-A to implement only the essential secure +services in EL3 and instantiate the rest in a partition in S-EL0. +Furthermore, multiple Secure Partitions can be used to isolate unrelated +services from each other. + +The following diagram illustrates the place of a Secure Partition in a typical +Armv8-A software stack. A single or multiple Secure Partitions provide secure +services to software components in the Non-secure world and other Secure +Partitions. + +|Image 2| + +The TF-A build system is responsible for including the Secure Partition image +in the FIP. During boot, BL2 includes support to authenticate and load the +Secure Partition image. A BL31 component called **Secure Partition Manager +(SPM)** is responsible for managing the partition. This is semantically +similar to a hypervisor managing a virtual machine. + +The SPM is responsible for the following actions during boot: + +- Allocate resources requested by the Secure Partition. + +- Perform architectural and system setup required by the Secure Partition to + fulfil a service request. + +- Implement a standard interface that is used for initialising a Secure + Partition. + +The SPM is responsible for the following actions during runtime: + +- Implement a standard interface that is used by a Secure Partition to fulfil + service requests. + +- Implement a standard interface that is used by the Non-secure world for + accessing the services exported by a Secure Partition. A service can be + invoked through a SMC. + +Alternatively, a partition can be viewed as a thread of execution running under +the control of the SPM. Hence common programming concepts described below are +applicable to a partition. + +Description +=========== + +The previous section introduced some general aspects of the software +architecture of a Secure Partition. This section describes the specific choices +made in the current implementation of this software architecture. Subsequent +revisions of the implementation will include a richer set of features that +enable a more flexible architecture. + +Building TF-A with Secure Partition support +------------------------------------------- + +SPM is supported on the Arm FVP exclusively at the moment. The current +implementation supports inclusion of only a single Secure Partition in which a +service always runs to completion (e.g. the requested services cannot be +preempted to give control back to the Normal world). + +It is not currently possible for BL31 to integrate SPM support and a Secure +Payload Dispatcher (SPD) at the same time; they are mutually exclusive. In the +SPM bootflow, a Secure Partition image executing at S-EL0 replaces the Secure +Payload image executing at S-EL1 (e.g. a Trusted OS). Both are referred to as +BL32. + +A working prototype of a SP has been implemented by re-purposing the EDK2 code +and tools, leveraging the concept of the *Standalone Management Mode (MM)* in +the UEFI specification (see the PI v1.6 Volume 4: Management Mode Core +Interface). This will be referred to as the *Standalone MM Secure Partition* in +the rest of this document. + +To enable SPM support in TF-A, the source code must be compiled with the build +flag ``SPM_MM=1``, along with ``EL3_EXCEPTION_HANDLING=1`` and ``ENABLE_SVE_FOR_NS=0``. +On Arm platforms the build option ``ARM_BL31_IN_DRAM`` must be set to 1. Also, the +location of the binary that contains the BL32 image +(``BL32=path/to/image.bin``) must be specified. + +First, build the Standalone MM Secure Partition. To build it, refer to the +`instructions in the EDK2 repository`_. + +Then build TF-A with SPM support and include the Standalone MM Secure Partition +image in the FIP: + +.. code:: shell + + BL32=path/to/standalone/mm/sp BL33=path/to/bl33.bin \ + make PLAT=fvp SPM_MM=1 EL3_EXCEPTION_HANDLING=1 ENABLE_SVE_FOR_NS=0 ARM_BL31_IN_DRAM=1 all fip + +Describing Secure Partition resources +------------------------------------- + +TF-A exports a porting interface that enables a platform to specify the system +resources required by the Secure Partition. Some instructions are given below. +However, this interface is under development and it may change as new features +are implemented. + +- A Secure Partition is considered a BL32 image, so the same defines that apply + to BL32 images apply to a Secure Partition: ``BL32_BASE`` and ``BL32_LIMIT``. + +- The following defines are needed to allocate space for the translation tables + used by the Secure Partition: ``PLAT_SP_IMAGE_MMAP_REGIONS`` and + ``PLAT_SP_IMAGE_MAX_XLAT_TABLES``. + +- The functions ``plat_get_secure_partition_mmap()`` and + ``plat_get_secure_partition_boot_info()`` have to be implemented. The file + ``plat/arm/board/fvp/fvp_common.c`` can be used as an example. It uses the + defines in ``include/plat/arm/common/arm_spm_def.h``. + + - ``plat_get_secure_partition_mmap()`` returns an array of mmap regions that + describe the memory regions that the SPM needs to allocate for a Secure + Partition. + + - ``plat_get_secure_partition_boot_info()`` returns a + ``spm_mm_boot_info_t`` struct that is populated by the platform + with information about the memory map of the Secure Partition. + +For an example of all the changes in context, you may refer to commit +``e29efeb1b4``, in which the port for FVP was introduced. + +Accessing Secure Partition services +----------------------------------- + +The `SMC Calling Convention`_ (*Arm DEN 0028B*) describes SMCs as a conduit for +accessing services implemented in the Secure world. The ``MM_COMMUNICATE`` +interface defined in the `Management Mode Interface Specification`_ (*Arm DEN +0060A*) is used to invoke a Secure Partition service as a Fast Call. + +The mechanism used to identify a service within the partition depends on the +service implementation. It is assumed that the caller of the service will be +able to discover this mechanism through standard platform discovery mechanisms +like ACPI and Device Trees. For example, *Volume 4: Platform Initialisation +Specification v1.6. Management Mode Core Interface* specifies that a GUID is +used to identify a management mode service. A client populates the GUID in the +``EFI_MM_COMMUNICATE_HEADER``. The header is populated in the communication +buffer shared with the Secure Partition. + +A Fast Call appears to be atomic from the perspective of the caller and returns +when the requested operation has completed. A service invoked through the +``MM_COMMUNICATE`` SMC will run to completion in the partition on a given CPU. +The SPM is responsible for guaranteeing this behaviour. This means that there +can only be a single outstanding Fast Call in a partition on a given CPU. + +Exchanging data with the Secure Partition +----------------------------------------- + +The exchange of data between the Non-secure world and the partition takes place +through a shared memory region. The location of data in the shared memory area +is passed as a parameter to the ``MM_COMMUNICATE`` SMC. The shared memory area +is statically allocated by the SPM and is expected to be either implicitly known +to the Non-secure world or discovered through a platform discovery mechanism +e.g. ACPI table or device tree. It is possible for the Non-secure world to +exchange data with a partition only if it has been populated in this shared +memory area. The shared memory area is implemented as per the guidelines +specified in Section 3.2.3 of the `Management Mode Interface Specification`_ +(*Arm DEN 0060A*). + +The format of data structures used to encapsulate data in the shared memory is +agreed between the Non-secure world and the Secure Partition. For example, in +the `Management Mode Interface specification`_ (*Arm DEN 0060A*), Section 4 +describes that the communication buffer shared between the Non-secure world and +the Management Mode (MM) in the Secure world must be of the type +``EFI_MM_COMMUNICATE_HEADER``. This data structure is defined in *Volume 4: +Platform Initialisation Specification v1.6. Management Mode Core Interface*. +Any caller of a MM service will have to use the ``EFI_MM_COMMUNICATE_HEADER`` +data structure. + +Runtime model of the Secure Partition +===================================== + +This section describes how the Secure Partition interfaces with the SPM. + +Interface with SPM +------------------ + +In order to instantiate one or more secure services in the Secure Partition in +S-EL0, the SPM should define the following types of interfaces: + +- Interfaces that enable access to privileged operations from S-EL0. These + operations typically require access to system resources that are either shared + amongst multiple software components in the Secure world or cannot be directly + accessed from an unprivileged Exception Level. + +- Interfaces that establish the control path between the SPM and the Secure + Partition. + +This section describes the APIs currently exported by the SPM that enable a +Secure Partition to initialise itself and export its services in S-EL0. These +interfaces are not accessible from the Non-secure world. + +Conduit +^^^^^^^ + +The `SMC Calling Convention`_ (*Arm DEN 0028B*) specification describes the SMC +and HVC conduits for accessing firmware services and their availability +depending on the implemented Exception levels. In S-EL0, the Supervisor Call +exception (SVC) is the only architectural mechanism available for unprivileged +software to make a request for an operation implemented in privileged software. +Hence, the SVC conduit must be used by the Secure Partition to access interfaces +implemented by the SPM. + +A SVC causes an exception to be taken to S-EL1. TF-A assumes ownership of S-EL1 +and installs a simple exception vector table in S-EL1 that relays a SVC request +from a Secure Partition as a SMC request to the SPM in EL3. Upon servicing the +SMC request, Trusted Firmware-A returns control directly to S-EL0 through an +ERET instruction. + +Calling conventions +^^^^^^^^^^^^^^^^^^^ + +The `SMC Calling Convention`_ (*Arm DEN 0028B*) specification describes the +32-bit and 64-bit calling conventions for the SMC and HVC conduits. The SVC +conduit introduces the concept of SVC32 and SVC64 calling conventions. The SVC32 +and SVC64 calling conventions are equivalent to the 32-bit (SMC32) and the +64-bit (SMC64) calling conventions respectively. + +Communication initiated by SPM +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A service request is initiated from the SPM through an exception return +instruction (ERET) to S-EL0. Later, the Secure Partition issues an SVC +instruction to signal completion of the request. Some example use cases are +given below: + +- A request to initialise the Secure Partition during system boot. + +- A request to handle a runtime service request. + +Communication initiated by Secure Partition +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A request is initiated from the Secure Partition by executing a SVC instruction. +An ERET instruction is used by TF-A to return to S-EL0 with the result of the +request. + +For instance, a request to perform privileged operations on behalf of a +partition (e.g. management of memory attributes in the translation tables for +the Secure EL1&0 translation regime). + +Interfaces +^^^^^^^^^^ + +The current implementation reserves function IDs for Fast Calls in the Standard +Secure Service calls range (see `SMC Calling Convention`_ (*Arm DEN 0028B*) +specification) for each API exported by the SPM. This section defines the +function prototypes for each function ID. The function IDs specify whether one +or both of the SVC32 and SVC64 calling conventions can be used to invoke the +corresponding interface. + +Secure Partition Event Management +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The Secure Partition provides an Event Management interface that is used by the +SPM to delegate service requests to the Secure Partition. The interface also +allows the Secure Partition to: + +- Register with the SPM a service that it provides. +- Indicate completion of a service request delegated by the SPM + +Miscellaneous interfaces +------------------------ + +``SPM_MM_VERSION_AARCH32`` +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +- Description + + Returns the version of the interface exported by SPM. + +- Parameters + + - **uint32** - Function ID + + - SVC32 Version: **0x84000060** + +- Return parameters + + - **int32** - Status + + On success, the format of the value is as follows: + + - Bit [31]: Must be 0 + - Bits [30:16]: Major Version. Must be 0 for this revision of the SPM + interface. + - Bits [15:0]: Minor Version. Must be 1 for this revision of the SPM + interface. + + On error, the format of the value is as follows: + + - ``NOT_SUPPORTED``: SPM interface is not supported or not available for the + client. + +- Usage + + This function returns the version of the Secure Partition Manager + implementation. The major version is 0 and the minor version is 1. The version + number is a 31-bit unsigned integer, with the upper 15 bits denoting the major + revision, and the lower 16 bits denoting the minor revision. The following + rules apply to the version numbering: + + - Different major revision values indicate possibly incompatible functions. + + - For two revisions, A and B, for which the major revision values are + identical, if the minor revision value of revision B is greater than the + minor revision value of revision A, then every function in revision A must + work in a compatible way with revision B. However, it is possible for + revision B to have a higher function count than revision A. + +- Implementation responsibilities + + If this function returns a valid version number, all the functions that are + described subsequently must be implemented, unless it is explicitly stated + that a function is optional. + +See `Error Codes`_ for integer values that are associated with each return +code. + +Secure Partition Initialisation +------------------------------- + +The SPM is responsible for initialising the architectural execution context to +enable initialisation of a service in S-EL0. The responsibilities of the SPM are +listed below. At the end of initialisation, the partition issues a +``MM_SP_EVENT_COMPLETE_AARCH64`` call (described later) to signal readiness for +handling requests for services implemented by the Secure Partition. The +initialisation event is executed as a Fast Call. + +Entry point invocation +^^^^^^^^^^^^^^^^^^^^^^ + +The entry point for service requests that should be handled as Fast Calls is +used as the target of the ERET instruction to start initialisation of the Secure +Partition. + +Architectural Setup +^^^^^^^^^^^^^^^^^^^ + +At cold boot, system registers accessible from S-EL0 will be in their reset +state unless otherwise specified. The SPM will perform the following +architectural setup to enable execution in S-EL0 + +MMU setup +^^^^^^^^^ + +The platform port of a Secure Partition specifies to the SPM a list of regions +that it needs access to and their attributes. The SPM validates this resource +description and initialises the Secure EL1&0 translation regime as follows. + +1. Device regions are mapped with nGnRE attributes and Execute Never + instruction access permissions. + +2. Code memory regions are mapped with RO data and Executable instruction access + permissions. + +3. Read Only data memory regions are mapped with RO data and Execute Never + instruction access permissions. + +4. Read Write data memory regions are mapped with RW data and Execute Never + instruction access permissions. + +5. If the resource description does not explicitly describe the type of memory + regions then all memory regions will be marked with Code memory region + attributes. + +6. The ``UXN`` and ``PXN`` bits are set for regions that are not executable by + S-EL0 or S-EL1. + +System Register Setup +^^^^^^^^^^^^^^^^^^^^^ + +System registers that influence software execution in S-EL0 are setup by the SPM +as follows: + +1. ``SCTLR_EL1`` + + - ``UCI=1`` + - ``EOE=0`` + - ``WXN=1`` + - ``nTWE=1`` + - ``nTWI=1`` + - ``UCT=1`` + - ``DZE=1`` + - ``I=1`` + - ``UMA=0`` + - ``SA0=1`` + - ``C=1`` + - ``A=1`` + - ``M=1`` + +2. ``CPACR_EL1`` + + - ``FPEN=b'11`` + +3. ``PSTATE`` + + - ``D,A,I,F=1`` + - ``CurrentEL=0`` (EL0) + - ``SpSel=0`` (Thread mode) + - ``NRW=0`` (AArch64) + +General Purpose Register Setup +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +SPM will invoke the entry point of a service by executing an ERET instruction. +This transition into S-EL0 is special since it is not in response to a previous +request through a SVC instruction. This is the first entry into S-EL0. The +general purpose register usage at the time of entry will be as specified in the +"Return State" column of Table 3-1 in Section 3.1 "Register use in AArch64 SMC +calls" of the `SMC Calling Convention`_ (*Arm DEN 0028B*) specification. In +addition, certain other restrictions will be applied as described below. + +1. ``SP_EL0`` + + A non-zero value will indicate that the SPM has initialised the stack pointer + for the current CPU. + + The value will be 0 otherwise. + +2. ``X4-X30`` + + The values of these registers will be 0. + +3. ``X0-X3`` + + Parameters passed by the SPM. + + - ``X0``: Virtual address of a buffer shared between EL3 and S-EL0. The + buffer will be mapped in the Secure EL1&0 translation regime with read-only + memory attributes described earlier. + + - ``X1``: Size of the buffer in bytes. + + - ``X2``: Cookie value (*IMPLEMENTATION DEFINED*). + + - ``X3``: Cookie value (*IMPLEMENTATION DEFINED*). + +Runtime Event Delegation +------------------------ + +The SPM receives requests for Secure Partition services through a synchronous +invocation (i.e. a SMC from the Non-secure world). These requests are delegated +to the partition by programming a return from the last +``MM_SP_EVENT_COMPLETE_AARCH64`` call received from the partition. The last call +was made to signal either completion of Secure Partition initialisation or +completion of a partition service request. + +``MM_SP_EVENT_COMPLETE_AARCH64`` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +- Description + + Signal completion of the last SP service request. + +- Parameters + + - **uint32** - Function ID + + - SVC64 Version: **0xC4000061** + + - **int32** - Event Status Code + + Zero or a positive value indicates that the event was handled successfully. + The values depend upon the original event that was delegated to the Secure + partition. They are described as follows. + + - ``SUCCESS`` : Used to indicate that the Secure Partition was initialised + or a runtime request was handled successfully. + + - Any other value greater than 0 is used to pass a specific Event Status + code in response to a runtime event. + + A negative value indicates an error. The values of Event Status code depend + on the original event. + +- Return parameters + + - **int32** - Event ID/Return Code + + Zero or a positive value specifies the unique ID of the event being + delegated to the partition by the SPM. + + In the current implementation, this parameter contains the function ID of + the ``MM_COMMUNICATE`` SMC. This value indicates to the partition that an + event has been delegated to it in response to an ``MM_COMMUNICATE`` request + from the Non-secure world. + + A negative value indicates an error. The format of the value is as follows: + + - ``NOT_SUPPORTED``: Function was called from the Non-secure world. + + See `Error Codes`_ for integer values that are associated with each return + code. + + - **uint32** - Event Context Address + + Address of a buffer shared between the SPM and Secure Partition to pass + event specific information. The format of the data populated in the buffer + is implementation defined. + + The buffer is mapped in the Secure EL1&0 translation regime with read-only + memory attributes described earlier. + + For the SVC64 version, this parameter is a 64-bit Virtual Address (VA). + + For the SVC32 version, this parameter is a 32-bit Virtual Address (VA). + + - **uint32** - Event context size + + Size of the memory starting at Event Address. + + - **uint32/uint64** - Event Cookie + + This is an optional parameter. If unused its value is SBZ. + +- Usage + + This function signals to the SPM that the handling of the last event delegated + to a partition has completed. The partition is ready to handle its next event. + A return from this function is in response to the next event that will be + delegated to the partition. The return parameters describe the next event. + +- Caller responsibilities + + A Secure Partition must only call ``MM_SP_EVENT_COMPLETE_AARCH64`` to signal + completion of a request that was delegated to it by the SPM. + +- Callee responsibilities + + When the SPM receives this call from a Secure Partition, the corresponding + syndrome information can be used to return control through an ERET + instruction, to the instruction immediately after the call in the Secure + Partition context. This syndrome information comprises of general purpose and + system register values when the call was made. + + The SPM must save this syndrome information and use it to delegate the next + event to the Secure Partition. The return parameters of this interface must + specify the properties of the event and be populated in ``X0-X3/W0-W3`` + registers. + +Secure Partition Memory Management +---------------------------------- + +A Secure Partition executes at S-EL0, which is an unprivileged Exception Level. +The SPM is responsible for enabling access to regions of memory in the system +address map from a Secure Partition. This is done by mapping these regions in +the Secure EL1&0 Translation regime with appropriate memory attributes. +Attributes refer to memory type, permission, cacheability and shareability +attributes used in the Translation tables. The definitions of these attributes +and their usage can be found in the `Armv8-A ARM`_ (*Arm DDI 0487*). + +All memory required by the Secure Partition is allocated upfront in the SPM, +even before handing over to the Secure Partition for the first time. The initial +access permissions of the memory regions are statically provided by the platform +port and should allow the Secure Partition to run its initialisation code. + +However, they might not suit the final needs of the Secure Partition because its +final memory layout might not be known until the Secure Partition initialises +itself. As the Secure Partition initialises its runtime environment it might, +for example, load dynamically some modules. For instance, a Secure Partition +could implement a loader for a standard executable file format (e.g. an PE-COFF +loader for loading executable files at runtime). These executable files will be +a part of the Secure Partition image. The location of various sections in an +executable file and their permission attributes (e.g. read-write data, read-only +data and code) will be known only when the file is loaded into memory. + +In this case, the Secure Partition needs a way to change the access permissions +of its memory regions. The SPM provides this feature through the +``MM_SP_MEMORY_ATTRIBUTES_SET_AARCH64`` SVC interface. This interface is +available to the Secure Partition during a specific time window: from the first +entry into the Secure Partition up to the first ``SP_EVENT_COMPLETE`` call that +signals the Secure Partition has finished its initialisation. Once the +initialisation is complete, the SPM does not allow changes to the memory +attributes. + +This section describes the standard SVC interface that is implemented by the SPM +to determine and change permission attributes of memory regions that belong to a +Secure Partition. + +``MM_SP_MEMORY_ATTRIBUTES_GET_AARCH64`` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +- Description + + Request the permission attributes of a memory region from S-EL0. + +- Parameters + + - **uint32** Function ID + + - SVC64 Version: **0xC4000064** + + - **uint64** Base Address + + This parameter is a 64-bit Virtual Address (VA). + + There are no alignment restrictions on the Base Address. The permission + attributes of the translation granule it lies in are returned. + +- Return parameters + + - **int32** - Memory Attributes/Return Code + + On success the format of the Return Code is as follows: + + - Bits[1:0] : Data access permission + + - b'00 : No access + - b'01 : Read-Write access + - b'10 : Reserved + - b'11 : Read-only access + + - Bit[2]: Instruction access permission + + - b'0 : Executable + - b'1 : Non-executable + + - Bit[30:3] : Reserved. SBZ. + + - Bit[31] : Must be 0 + + On failure the following error codes are returned: + + - ``INVALID_PARAMETERS``: The Secure Partition is not allowed to access the + memory region the Base Address lies in. + + - ``NOT_SUPPORTED`` : The SPM does not support retrieval of attributes of + any memory page that is accessible by the Secure Partition, or the + function was called from the Non-secure world. Also returned if it is + used after ``MM_SP_EVENT_COMPLETE_AARCH64``. + + See `Error Codes`_ for integer values that are associated with each return + code. + +- Usage + + This function is used to request the permission attributes for S-EL0 on a + memory region accessible from a Secure Partition. The size of the memory + region is equal to the Translation Granule size used in the Secure EL1&0 + translation regime. Requests to retrieve other memory region attributes are + not currently supported. + +- Caller responsibilities + + The caller must obtain the Translation Granule Size of the Secure EL1&0 + translation regime from the SPM through an implementation defined method. + +- Callee responsibilities + + The SPM must not return the memory access controls for a page of memory that + is not accessible from a Secure Partition. + +``MM_SP_MEMORY_ATTRIBUTES_SET_AARCH64`` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +- Description + + Set the permission attributes of a memory region from S-EL0. + +- Parameters + + - **uint32** - Function ID + + - SVC64 Version: **0xC4000065** + + - **uint64** - Base Address + + This parameter is a 64-bit Virtual Address (VA). + + The alignment of the Base Address must be greater than or equal to the size + of the Translation Granule Size used in the Secure EL1&0 translation + regime. + + - **uint32** - Page count + + Number of pages starting from the Base Address whose memory attributes + should be changed. The page size is equal to the Translation Granule Size. + + - **uint32** - Memory Access Controls + + - Bits[1:0] : Data access permission + + - b'00 : No access + - b'01 : Read-Write access + - b'10 : Reserved + - b'11 : Read-only access + + - Bit[2] : Instruction access permission + + - b'0 : Executable + - b'1 : Non-executable + + - Bits[31:3] : Reserved. SBZ. + + A combination of attributes that mark the region with RW and Executable + permissions is prohibited. A request to mark a device memory region with + Executable permissions is prohibited. + +- Return parameters + + - **int32** - Return Code + + - ``SUCCESS``: The Memory Access Controls were changed successfully. + + - ``DENIED``: The SPM is servicing a request to change the attributes of a + memory region that overlaps with the region specified in this request. + + - ``INVALID_PARAMETER``: An invalid combination of Memory Access Controls + has been specified. The Base Address is not correctly aligned. The Secure + Partition is not allowed to access part or all of the memory region + specified in the call. + + - ``NO_MEMORY``: The SPM does not have memory resources to change the + attributes of the memory region in the translation tables. + + - ``NOT_SUPPORTED``: The SPM does not permit change of attributes of any + memory region that is accessible by the Secure Partition. Function was + called from the Non-secure world. Also returned if it is used after + ``MM_SP_EVENT_COMPLETE_AARCH64``. + + See `Error Codes`_ for integer values that are associated with each return + code. + +- Usage + + This function is used to change the permission attributes for S-EL0 on a + memory region accessible from a Secure Partition. The size of the memory + region is equal to the Translation Granule size used in the Secure EL1&0 + translation regime. Requests to change other memory region attributes are not + currently supported. + + This function is only available at boot time. This interface is revoked after + the Secure Partition sends the first ``MM_SP_EVENT_COMPLETE_AARCH64`` to + signal that it is initialised and ready to receive run-time requests. + +- Caller responsibilities + + The caller must obtain the Translation Granule Size of the Secure EL1&0 + translation regime from the SPM through an implementation defined method. + +- Callee responsibilities + + The SPM must preserve the original memory access controls of the region of + memory in case of an unsuccessful call. The SPM must preserve the consistency + of the S-EL1 translation regime if this function is called on different PEs + concurrently and the memory regions specified overlap. + +Error Codes +----------- + +.. csv-table:: + :header: "Name", "Value" + + ``SUCCESS``,0 + ``NOT_SUPPORTED``,-1 + ``INVALID_PARAMETER``,-2 + ``DENIED``,-3 + ``NO_MEMORY``,-5 + ``NOT_PRESENT``,-7 + +-------------- + +*Copyright (c) 2017-2021, Arm Limited and Contributors. All rights reserved.* + +.. _Armv8-A ARM: https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile +.. _instructions in the EDK2 repository: https://github.com/tianocore/edk2-staging/blob/AArch64StandaloneMm/HowtoBuild.MD +.. _Management Mode Interface Specification: http://infocenter.arm.com/help/topic/com.arm.doc.den0060a/DEN0060A_ARM_MM_Interface_Specification.pdf +.. _SDEI Specification: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf +.. _SMC Calling Convention: https://developer.arm.com/docs/den0028/latest + +.. |Image 1| image:: ../resources/diagrams/secure_sw_stack_tos.png +.. |Image 2| image:: ../resources/diagrams/secure_sw_stack_sp.png diff --git a/docs/components/secure-partition-manager.rst b/docs/components/secure-partition-manager.rst new file mode 100644 index 0000000..5d3adec --- /dev/null +++ b/docs/components/secure-partition-manager.rst @@ -0,0 +1,1673 @@ +Secure Partition Manager +************************ + +.. contents:: + +.. toctree:: + ffa-manifest-binding + +Acronyms +======== + ++--------+--------------------------------------+ +| CoT | Chain of Trust | ++--------+--------------------------------------+ +| DMA | Direct Memory Access | ++--------+--------------------------------------+ +| DTB | Device Tree Blob | ++--------+--------------------------------------+ +| DTS | Device Tree Source | ++--------+--------------------------------------+ +| EC | Execution Context | ++--------+--------------------------------------+ +| FIP | Firmware Image Package | ++--------+--------------------------------------+ +| FF-A | Firmware Framework for Arm A-profile | ++--------+--------------------------------------+ +| IPA | Intermediate Physical Address | ++--------+--------------------------------------+ +| JOP | Jump-Oriented Programming | ++--------+--------------------------------------+ +| NWd | Normal World | ++--------+--------------------------------------+ +| ODM | Original Design Manufacturer | ++--------+--------------------------------------+ +| OEM | Original Equipment Manufacturer | ++--------+--------------------------------------+ +| PA | Physical Address | ++--------+--------------------------------------+ +| PE | Processing Element | ++--------+--------------------------------------+ +| PM | Power Management | ++--------+--------------------------------------+ +| PVM | Primary VM | ++--------+--------------------------------------+ +| ROP | Return-Oriented Programming | ++--------+--------------------------------------+ +| SMMU | System Memory Management Unit | ++--------+--------------------------------------+ +| SP | Secure Partition | ++--------+--------------------------------------+ +| SPD | Secure Payload Dispatcher | ++--------+--------------------------------------+ +| SPM | Secure Partition Manager | ++--------+--------------------------------------+ +| SPMC | SPM Core | ++--------+--------------------------------------+ +| SPMD | SPM Dispatcher | ++--------+--------------------------------------+ +| SiP | Silicon Provider | ++--------+--------------------------------------+ +| SWd | Secure World | ++--------+--------------------------------------+ +| TLV | Tag-Length-Value | ++--------+--------------------------------------+ +| TOS | Trusted Operating System | ++--------+--------------------------------------+ +| VM | Virtual Machine | ++--------+--------------------------------------+ + +Foreword +======== + +Three implementations of a Secure Partition Manager co-exist in the TF-A +codebase: + +#. S-EL2 SPMC based on the FF-A specification `[1]`_, enabling virtualization in + the secure world, managing multiple S-EL1 or S-EL0 partitions. +#. EL3 SPMC based on the FF-A specification, managing a single S-EL1 partition + without virtualization in the secure world. +#. EL3 SPM based on the MM specification, legacy implementation managing a + single S-EL0 partition `[2]`_. + +These implementations differ in their respective SW architecture and only one +can be selected at build time. This document: + +- describes the implementation from bullet 1. when the SPMC resides at S-EL2. +- is not an architecture specification and it might provide assumptions + on sections mandated as implementation-defined in the specification. +- covers the implications to TF-A used as a bootloader, and Hafnium used as a + reference code base for an S-EL2/SPMC secure firmware on platforms + implementing the FEAT_SEL2 architecture extension. + +Terminology +----------- + +- The term Hypervisor refers to the NS-EL2 component managing Virtual Machines + (or partitions) in the normal world. +- The term SPMC refers to the S-EL2 component managing secure partitions in + the secure world when the FEAT_SEL2 architecture extension is implemented. +- Alternatively, SPMC can refer to an S-EL1 component, itself being a secure + partition and implementing the FF-A ABI on platforms not implementing the + FEAT_SEL2 architecture extension. +- The term VM refers to a normal world Virtual Machine managed by an Hypervisor. +- The term SP refers to a secure world "Virtual Machine" managed by an SPMC. + +Support for legacy platforms +---------------------------- + +The SPM is split into a dispatcher and a core component (respectively SPMD and +SPMC) residing at different exception levels. To permit the FF-A specification +adoption and a smooth migration, the SPMD supports an SPMC residing either at +S-EL1 or S-EL2: + +- The SPMD is located at EL3 and mainly relays the FF-A protocol from NWd + (Hypervisor or OS kernel) to the SPMC. +- The same SPMD component is used for both S-EL1 and S-EL2 SPMC configurations. +- The SPMC exception level is a build time choice. + +TF-A supports both cases: + +- S-EL1 SPMC for platforms not supporting the FEAT_SEL2 architecture + extension. The SPMD relays the FF-A protocol from EL3 to S-EL1. +- S-EL2 SPMC for platforms implementing the FEAT_SEL2 architecture + extension. The SPMD relays the FF-A protocol from EL3 to S-EL2. + +Sample reference stack +====================== + +The following diagram illustrates a possible configuration when the +FEAT_SEL2 architecture extension is implemented, showing the SPMD +and SPMC, one or multiple secure partitions, with an optional +Hypervisor: + +.. image:: ../resources/diagrams/ff-a-spm-sel2.png + +TF-A build options +================== + +This section explains the TF-A build options involved in building with +support for an FF-A based SPM where the SPMD is located at EL3 and the +SPMC located at S-EL1, S-EL2 or EL3: + +- **SPD=spmd**: this option selects the SPMD component to relay the FF-A + protocol from NWd to SWd back and forth. It is not possible to + enable another Secure Payload Dispatcher when this option is chosen. +- **SPMD_SPM_AT_SEL2**: this option adjusts the SPMC exception + level to being at S-EL2. It defaults to enabled (value 1) when + SPD=spmd is chosen. +- **SPMC_AT_EL3**: this option adjusts the SPMC exception level to being + at EL3. +- If neither ``SPMD_SPM_AT_SEL2`` or ``SPMC_AT_EL3`` are enabled the SPMC + exception level is set to S-EL1. + ``SPMD_SPM_AT_SEL2`` is enabled. The context save/restore routine + and exhaustive list of registers is visible at `[4]`_. +- **SPMC_AT_EL3_SEL0_SP**: this option enables the support to load SEL0 SP + when SPMC at EL3 support is enabled. +- **SP_LAYOUT_FILE**: this option specifies a text description file + providing paths to SP binary images and manifests in DTS format + (see `Describing secure partitions`_). It + is required when ``SPMD_SPM_AT_SEL2`` is enabled hence when multiple + secure partitions are to be loaded by BL2 on behalf of the SPMC. + ++---------------+------------------+-------------+-------------------------+ +| | SPMD_SPM_AT_SEL2 | SPMC_AT_EL3 | CTX_INCLUDE_EL2_REGS(*) | ++---------------+------------------+-------------+-------------------------+ +| SPMC at S-EL1 | 0 | 0 | 0 | ++---------------+------------------+-------------+-------------------------+ +| SPMC at S-EL2 | 1 (default when | 0 | 1 | +| | SPD=spmd) | | | ++---------------+------------------+-------------+-------------------------+ +| SPMC at EL3 | 0 | 1 | 0 | ++---------------+------------------+-------------+-------------------------+ + +Other combinations of such build options either break the build or are not +supported. + +Notes: + +- Only Arm's FVP platform is supported to use with the TF-A reference software + stack. +- When ``SPMD_SPM_AT_SEL2=1``, the reference software stack assumes enablement + of FEAT_PAuth, FEAT_BTI and FEAT_MTE architecture extensions. +- ``(*) CTX_INCLUDE_EL2_REGS``, this flag is |TF-A| internal and informational + in this table. When set, it provides the generic support for saving/restoring + EL2 registers required when S-EL2 firmware is present. +- BL32 option is re-purposed to specify the SPMC image. It can specify either + the Hafnium binary path (built for the secure world) or the path to a TEE + binary implementing FF-A interfaces. +- BL33 option can specify the TFTF binary or a normal world loader + such as U-Boot or the UEFI framework payload. + +Sample TF-A build command line when the SPMC is located at S-EL1 +(e.g. when the FEAT_SEL2 architecture extension is not implemented): + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + SPD=spmd \ + SPMD_SPM_AT_SEL2=0 \ + BL32=<path-to-tee-binary> \ + BL33=<path-to-bl33-binary> \ + PLAT=fvp \ + all fip + +Sample TF-A build command line when FEAT_SEL2 architecture extension is +implemented and the SPMC is located at S-EL2: + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + PLAT=fvp \ + SPD=spmd \ + ARM_ARCH_MINOR=5 \ + BRANCH_PROTECTION=1 \ + CTX_INCLUDE_PAUTH_REGS=1 \ + CTX_INCLUDE_MTE_REGS=1 \ + BL32=<path-to-hafnium-binary> \ + BL33=<path-to-bl33-binary> \ + SP_LAYOUT_FILE=sp_layout.json \ + all fip + +Sample TF-A build command line when FEAT_SEL2 architecture extension is +implemented, the SPMC is located at S-EL2, and enabling secure boot: + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + PLAT=fvp \ + SPD=spmd \ + ARM_ARCH_MINOR=5 \ + BRANCH_PROTECTION=1 \ + CTX_INCLUDE_PAUTH_REGS=1 \ + CTX_INCLUDE_MTE_REGS=1 \ + BL32=<path-to-hafnium-binary> \ + BL33=<path-to-bl33-binary> \ + SP_LAYOUT_FILE=sp_layout.json \ + MBEDTLS_DIR=<path-to-mbedtls-lib> \ + TRUSTED_BOARD_BOOT=1 \ + COT=dualroot \ + ARM_ROTPK_LOCATION=devel_rsa \ + ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem \ + GENERATE_COT=1 \ + all fip + +Sample TF-A build command line when the SPMC is located at EL3: + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + SPD=spmd \ + SPMD_SPM_AT_SEL2=0 \ + SPMC_AT_EL3=1 \ + BL32=<path-to-tee-binary> \ + BL33=<path-to-bl33-binary> \ + PLAT=fvp \ + all fip + +Sample TF-A build command line when the SPMC is located at EL3 and SEL0 SP is +enabled: + +.. code:: shell + + make \ + CROSS_COMPILE=aarch64-none-elf- \ + SPD=spmd \ + SPMD_SPM_AT_SEL2=0 \ + SPMC_AT_EL3=1 \ + SPMC_AT_EL3_SEL0_SP=1 \ + BL32=<path-to-tee-binary> \ + BL33=<path-to-bl33-binary> \ + PLAT=fvp \ + all fip + +FVP model invocation +==================== + +The FVP command line needs the following options to exercise the S-EL2 SPMC: + ++---------------------------------------------------+------------------------------------+ +| - cluster0.has_arm_v8-5=1 | Implements FEAT_SEL2, FEAT_PAuth, | +| - cluster1.has_arm_v8-5=1 | and FEAT_BTI. | ++---------------------------------------------------+------------------------------------+ +| - pci.pci_smmuv3.mmu.SMMU_AIDR=2 | Parameters required for the | +| - pci.pci_smmuv3.mmu.SMMU_IDR0=0x0046123B | SMMUv3.2 modeling. | +| - pci.pci_smmuv3.mmu.SMMU_IDR1=0x00600002 | | +| - pci.pci_smmuv3.mmu.SMMU_IDR3=0x1714 | | +| - pci.pci_smmuv3.mmu.SMMU_IDR5=0xFFFF0472 | | +| - pci.pci_smmuv3.mmu.SMMU_S_IDR1=0xA0000002 | | +| - pci.pci_smmuv3.mmu.SMMU_S_IDR2=0 | | +| - pci.pci_smmuv3.mmu.SMMU_S_IDR3=0 | | ++---------------------------------------------------+------------------------------------+ +| - cluster0.has_branch_target_exception=1 | Implements FEAT_BTI. | +| - cluster1.has_branch_target_exception=1 | | ++---------------------------------------------------+------------------------------------+ +| - cluster0.has_pointer_authentication=2 | Implements FEAT_PAuth | +| - cluster1.has_pointer_authentication=2 | | ++---------------------------------------------------+------------------------------------+ +| - cluster0.memory_tagging_support_level=2 | Implements FEAT_MTE2 | +| - cluster1.memory_tagging_support_level=2 | | +| - bp.dram_metadata.is_enabled=1 | | ++---------------------------------------------------+------------------------------------+ + +Sample FVP command line invocation: + +.. code:: shell + + <path-to-fvp-model>/FVP_Base_RevC-2xAEMvA -C pctl.startup=0.0.0.0 \ + -C cluster0.NUM_CORES=4 -C cluster1.NUM_CORES=4 -C bp.secure_memory=1 \ + -C bp.secureflashloader.fname=trusted-firmware-a/build/fvp/debug/bl1.bin \ + -C bp.flashloader0.fname=trusted-firmware-a/build/fvp/debug/fip.bin \ + -C bp.pl011_uart0.out_file=fvp-uart0.log -C bp.pl011_uart1.out_file=fvp-uart1.log \ + -C bp.pl011_uart2.out_file=fvp-uart2.log \ + -C cluster0.has_arm_v8-5=1 -C cluster1.has_arm_v8-5=1 \ + -C cluster0.has_pointer_authentication=2 -C cluster1.has_pointer_authentication=2 \ + -C cluster0.has_branch_target_exception=1 -C cluster1.has_branch_target_exception=1 \ + -C cluster0.memory_tagging_support_level=2 -C cluster1.memory_tagging_support_level=2 \ + -C bp.dram_metadata.is_enabled=1 \ + -C pci.pci_smmuv3.mmu.SMMU_AIDR=2 -C pci.pci_smmuv3.mmu.SMMU_IDR0=0x0046123B \ + -C pci.pci_smmuv3.mmu.SMMU_IDR1=0x00600002 -C pci.pci_smmuv3.mmu.SMMU_IDR3=0x1714 \ + -C pci.pci_smmuv3.mmu.SMMU_IDR5=0xFFFF0472 -C pci.pci_smmuv3.mmu.SMMU_S_IDR1=0xA0000002 \ + -C pci.pci_smmuv3.mmu.SMMU_S_IDR2=0 -C pci.pci_smmuv3.mmu.SMMU_S_IDR3=0 + +Boot process +============ + +Loading Hafnium and secure partitions in the secure world +--------------------------------------------------------- + +TF-A BL2 is the bootlader for the SPMC and SPs in the secure world. + +SPs may be signed by different parties (SiP, OEM/ODM, TOS vendor, etc.). +Thus they are supplied as distinct signed entities within the FIP flash +image. The FIP image itself is not signed hence this provides the ability +to upgrade SPs in the field. + +Booting through TF-A +-------------------- + +SP manifests +~~~~~~~~~~~~ + +An SP manifest describes SP attributes as defined in `[1]`_ +(partition manifest at virtual FF-A instance) in DTS format. It is +represented as a single file associated with the SP. A sample is +provided by `[5]`_. A binding document is provided by `[6]`_. + +Secure Partition packages +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Secure partitions are bundled as independent package files consisting +of: + +- a header +- a DTB +- an image payload + +The header starts with a magic value and offset values to SP DTB and +image payload. Each SP package is loaded independently by BL2 loader +and verified for authenticity and integrity. + +The SP package identified by its UUID (matching FF-A uuid property) is +inserted as a single entry into the FIP at end of the TF-A build flow +as shown: + +.. code:: shell + + Trusted Boot Firmware BL2: offset=0x1F0, size=0x8AE1, cmdline="--tb-fw" + EL3 Runtime Firmware BL31: offset=0x8CD1, size=0x13000, cmdline="--soc-fw" + Secure Payload BL32 (Trusted OS): offset=0x1BCD1, size=0x15270, cmdline="--tos-fw" + Non-Trusted Firmware BL33: offset=0x30F41, size=0x92E0, cmdline="--nt-fw" + HW_CONFIG: offset=0x3A221, size=0x2348, cmdline="--hw-config" + TB_FW_CONFIG: offset=0x3C569, size=0x37A, cmdline="--tb-fw-config" + SOC_FW_CONFIG: offset=0x3C8E3, size=0x48, cmdline="--soc-fw-config" + TOS_FW_CONFIG: offset=0x3C92B, size=0x427, cmdline="--tos-fw-config" + NT_FW_CONFIG: offset=0x3CD52, size=0x48, cmdline="--nt-fw-config" + B4B5671E-4A90-4FE1-B81F-FB13DAE1DACB: offset=0x3CD9A, size=0xC168, cmdline="--blob" + D1582309-F023-47B9-827C-4464F5578FC8: offset=0x48F02, size=0xC168, cmdline="--blob" + +.. uml:: ../resources/diagrams/plantuml/fip-secure-partitions.puml + +Describing secure partitions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A json-formatted description file is passed to the build flow specifying paths +to the SP binary image and associated DTS partition manifest file. The latter +is processed by the dtc compiler to generate a DTB fed into the SP package. +Optionally, the partition's json description can contain offsets for both +the image and partition manifest within the SP package. Both offsets need to be +4KB aligned, because it is the translation granule supported by Hafnium SPMC. +These fields can be leveraged to support SPs with S1 translation granules that +differ from 4KB, and to configure the regions allocated within the SP package, +as well as to comply with the requirements for the implementation of the boot +information protocol (see `Passing boot data to the SP`_ for more details). In +case the offsets are absent in their json node, they default to 0x1000 and +0x4000 for the manifest offset and image offset respectively. +This file also specifies the SP owner (as an optional field) identifying the +signing domain in case of dual root CoT. +The SP owner can either be the silicon or the platform provider. The +corresponding "owner" field value can either take the value of "SiP" or "Plat". +In absence of "owner" field, it defaults to "SiP" owner. +The UUID of the partition can be specified as a field in the description file or +if it does not exist there the UUID is extracted from the DTS partition +manifest. + +.. code:: shell + + { + "tee1" : { + "image": "tee1.bin", + "pm": "tee1.dts", + "owner": "SiP", + "uuid": "1b1820fe-48f7-4175-8999-d51da00b7c9f" + }, + + "tee2" : { + "image": "tee2.bin", + "pm": "tee2.dts", + "owner": "Plat" + }, + + "tee3" : { + "image": { + "file": "tee3.bin", + "offset":"0x2000" + }, + "pm": { + "file": "tee3.dts", + "offset":"0x6000" + }, + "owner": "Plat" + }, + } + +SPMC manifest +~~~~~~~~~~~~~ + +This manifest contains the SPMC *attribute* node consumed by the SPMD at boot +time. It implements `[1]`_ (SP manifest at physical FF-A instance) and serves +two different cases: + +- The SPMC resides at S-EL1: the SPMC manifest is used by the SPMD to setup a + SP that co-resides with the SPMC and executes at S-EL1 or Secure Supervisor + mode. +- The SPMC resides at S-EL2: the SPMC manifest is used by the SPMD to setup + the environment required by the SPMC to run at S-EL2. SPs run at S-EL1 or + S-EL0. + +.. code:: shell + + attribute { + spmc_id = <0x8000>; + maj_ver = <0x1>; + min_ver = <0x1>; + exec_state = <0x0>; + load_address = <0x0 0x6000000>; + entrypoint = <0x0 0x6000000>; + binary_size = <0x60000>; + }; + +- *spmc_id* defines the endpoint ID value that SPMC can query through + ``FFA_ID_GET``. +- *maj_ver/min_ver*. SPMD checks provided version versus its internal + version and aborts if not matching. +- *exec_state* defines the SPMC execution state (AArch64 or AArch32). + Notice Hafnium used as a SPMC only supports AArch64. +- *load_address* and *binary_size* are mostly used to verify secondary + entry points fit into the loaded binary image. +- *entrypoint* defines the cold boot primary core entry point used by + SPMD (currently matches ``BL32_BASE``) to enter the SPMC. + +Other nodes in the manifest are consumed by Hafnium in the secure world. +A sample can be found at `[7]`_: + +- The *hypervisor* node describes SPs. *is_ffa_partition* boolean attribute + indicates a FF-A compliant SP. The *load_address* field specifies the load + address at which BL2 loaded the SP package. +- *cpus* node provide the platform topology and allows MPIDR to VMPIDR mapping. + Note the primary core is declared first, then secondary cores are declared + in reverse order. +- The *memory* nodes provide platform information on the ranges of memory + available for use by SPs at runtime. These ranges relate to either + secure or non-secure memory, depending on the *device_type* field. + If the field specifies "memory" the range is secure, else if it specifies + "ns-memory" the memory is non-secure. The system integrator must exclude + the memory used by other components that are not SPs, such as the monitor, + or the SPMC itself, the OS Kernel/Hypervisor, or other NWd VMs. The SPMC + limits the SP's address space such that they do not access memory outside + of those ranges. + +SPMC boot +~~~~~~~~~ + +The SPMC is loaded by BL2 as the BL32 image. + +The SPMC manifest is loaded by BL2 as the ``TOS_FW_CONFIG`` image `[9]`_. + +BL2 passes the SPMC manifest address to BL31 through a register. + +At boot time, the SPMD in BL31 runs from the primary core, initializes the core +contexts and launches the SPMC (BL32) passing the following information through +registers: + +- X0 holds the ``TOS_FW_CONFIG`` physical address (or SPMC manifest blob). +- X1 holds the ``HW_CONFIG`` physical address. +- X4 holds the currently running core linear id. + +Loading of SPs +~~~~~~~~~~~~~~ + +At boot time, BL2 loads SPs sequentially in addition to the SPMC as depicted +below: + +.. uml:: ../resources/diagrams/plantuml/bl2-loading-sp.puml + +Note this boot flow is an implementation sample on Arm's FVP platform. +Platforms not using TF-A's *Firmware CONFiguration* framework would adjust to a +different boot flow. The flow restricts to a maximum of 8 secure partitions. + +Secure boot +~~~~~~~~~~~ + +The SP content certificate is inserted as a separate FIP item so that BL2 loads SPMC, +SPMC manifest, secure partitions and verifies them for authenticity and integrity. +Refer to TBBR specification `[3]`_. + +The multiple-signing domain feature (in current state dual signing domain `[8]`_) allows +the use of two root keys namely S-ROTPK and NS-ROTPK: + +- SPMC (BL32) and SPMC manifest are signed by the SiP using the S-ROTPK. +- BL33 may be signed by the OEM using NS-ROTPK. +- An SP may be signed either by SiP (using S-ROTPK) or by OEM (using NS-ROTPK). +- A maximum of 4 partitions can be signed with the S-ROTPK key and 4 partitions + signed with the NS-ROTPK key. + +Also refer to `Describing secure partitions`_ and `TF-A build options`_ sections. + +Hafnium in the secure world +=========================== + +General considerations +---------------------- + +Build platform for the secure world +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In the Hafnium reference implementation specific code parts are only relevant to +the secure world. Such portions are isolated in architecture specific files +and/or enclosed by a ``SECURE_WORLD`` macro. + +Secure partitions scheduling +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The FF-A specification `[1]`_ provides two ways to relinquinsh CPU time to +secure partitions. For this a VM (Hypervisor or OS kernel), or SP invokes one of: + +- the FFA_MSG_SEND_DIRECT_REQ interface. +- the FFA_RUN interface. + +Additionally a secure interrupt can pre-empt the normal world execution and give +CPU cycles by transitioning to EL3 and S-EL2. + +Platform topology +~~~~~~~~~~~~~~~~~ + +The *execution-ctx-count* SP manifest field can take the value of one or the +total number of PEs. The FF-A specification `[1]`_ recommends the +following SP types: + +- Pinned MP SPs: an execution context matches a physical PE. MP SPs must + implement the same number of ECs as the number of PEs in the platform. +- Migratable UP SPs: a single execution context can run and be migrated on any + physical PE. Such SP declares a single EC in its SP manifest. An UP SP can + receive a direct message request originating from any physical core targeting + the single execution context. + +Parsing SP partition manifests +------------------------------ + +Hafnium consumes SP manifests as defined in `[1]`_ and `SP manifests`_. +Note the current implementation may not implement all optional fields. + +The SP manifest may contain memory and device regions nodes. In case of +an S-EL2 SPMC: + +- Memory regions are mapped in the SP EL1&0 Stage-2 translation regime at + load time (or EL1&0 Stage-1 for an S-EL1 SPMC). A memory region node can + specify RX/TX buffer regions in which case it is not necessary for an SP + to explicitly invoke the ``FFA_RXTX_MAP`` interface. The memory referred + shall be contained within the memory ranges defined in SPMC manifest. The + NS bit in the attributes field should be consistent with the security + state of the range that it relates to. I.e. non-secure memory shall be + part of a non-secure memory range, and secure memory shall be contained + in a secure memory range of a given platform. +- Device regions are mapped in the SP EL1&0 Stage-2 translation regime (or + EL1&0 Stage-1 for an S-EL1 SPMC) as peripherals and possibly allocate + additional resources (e.g. interrupts). + +For the S-EL2 SPMC, base addresses for memory and device region nodes are IPAs +provided the SPMC identity maps IPAs to PAs within SP EL1&0 Stage-2 translation +regime. + +Note: in the current implementation both VTTBR_EL2 and VSTTBR_EL2 point to the +same set of page tables. It is still open whether two sets of page tables shall +be provided per SP. The memory region node as defined in the specification +provides a memory security attribute hinting to map either to the secure or +non-secure EL1&0 Stage-2 table if it exists. + +Passing boot data to the SP +--------------------------- + +In `[1]`_ , the section "Boot information protocol" defines a method for passing +data to the SPs at boot time. It specifies the format for the boot information +descriptor and boot information header structures, which describe the data to be +exchanged between SPMC and SP. +The specification also defines the types of data that can be passed. +The aggregate of both the boot info structures and the data itself is designated +the boot information blob, and is passed to a Partition as a contiguous memory +region. + +Currently, the SPM implementation supports the FDT type which is used to pass the +partition's DTB manifest. + +The region for the boot information blob is allocated through the SP package. + +.. image:: ../resources/diagrams/partition-package.png + +To adjust the space allocated for the boot information blob, the json description +of the SP (see section `Describing secure partitions`_) shall be updated to contain +the manifest offset. If no offset is provided the manifest offset defaults to 0x1000, +which is the page size in the Hafnium SPMC. + +The configuration of the boot protocol is done in the SPs manifest. As defined by +the specification, the manifest field 'gp-register-num' configures the GP register +which shall be used to pass the address to the partitions boot information blob when +booting the partition. +In addition, the Hafnium SPMC implementation requires the boot information arguments +to be listed in a designated DT node: + +.. code:: shell + + boot-info { + compatible = "arm,ffa-manifest-boot-info"; + ffa_manifest; + }; + +The whole secure partition package image (see `Secure Partition packages`_) is +mapped to the SP secure EL1&0 Stage-2 translation regime. As such, the SP can +retrieve the address for the boot information blob in the designated GP register, +process the boot information header and descriptors, access its own manifest +DTB blob and extract its partition manifest properties. + +SP Boot order +------------- + +SP manifests provide an optional boot order attribute meant to resolve +dependencies such as an SP providing a service required to properly boot +another SP. SPMC boots the SPs in accordance to the boot order attribute, +lowest to the highest value. If the boot order attribute is absent from the FF-A +manifest, the SP is treated as if it had the highest boot order value +(i.e. lowest booting priority). + +It is possible for an SP to call into another SP through a direct request +provided the latter SP has already been booted. + +Boot phases +----------- + +Primary core boot-up +~~~~~~~~~~~~~~~~~~~~ + +Upon boot-up, BL31 hands over to the SPMC (BL32) on the primary boot physical +core. The SPMC performs its platform initializations and registers the SPMC +secondary physical core entry point physical address by the use of the +`FFA_SECONDARY_EP_REGISTER`_ interface (SMC invocation from the SPMC to the SPMD +at secure physical FF-A instance). + +The SPMC then creates secure partitions based on SP packages and manifests. Each +secure partition is launched in sequence (`SP Boot order`_) on their "primary" +execution context. If the primary boot physical core linear id is N, an MP SP is +started using EC[N] on PE[N] (see `Platform topology`_). If the partition is a +UP SP, it is started using its unique EC0 on PE[N]. + +The SP primary EC (or the EC used when the partition is booted as described +above): + +- Performs the overall SP boot time initialization, and in case of a MP SP, + prepares the SP environment for other execution contexts. +- In the case of a MP SP, it invokes the FFA_SECONDARY_EP_REGISTER at secure + virtual FF-A instance (SMC invocation from SP to SPMC) to provide the IPA + entry point for other execution contexts. +- Exits through ``FFA_MSG_WAIT`` to indicate successful initialization or + ``FFA_ERROR`` in case of failure. + +Secondary cores boot-up +~~~~~~~~~~~~~~~~~~~~~~~ + +Once the system is started and NWd brought up, a secondary physical core is +woken up by the ``PSCI_CPU_ON`` service invocation. The TF-A SPD hook mechanism +calls into the SPMD on the newly woken up physical core. Then the SPMC is +entered at the secondary physical core entry point. + +In the current implementation, the first SP is resumed on the coresponding EC +(the virtual CPU which matches the physical core). The implication is that the +first SP must be a MP SP. + +In a linux based system, once secure and normal worlds are booted but prior to +a NWd FF-A driver has been loaded: + +- The first SP has initialized all its ECs in response to primary core boot up + (at system initialization) and secondary core boot up (as a result of linux + invoking PSCI_CPU_ON for all secondary cores). +- Other SPs have their first execution context initialized as a result of secure + world initialization on the primary boot core. Other ECs for those SPs have to + be run first through ffa_run to complete their initialization (which results + in the EC completing with FFA_MSG_WAIT). + +Refer to `Power management`_ for further details. + +Notifications +------------- + +The FF-A v1.1 specification `[1]`_ defines notifications as an asynchronous +communication mechanism with non-blocking semantics. It allows for one FF-A +endpoint to signal another for service provision, without hindering its current +progress. + +Hafnium currently supports 64 notifications. The IDs of each notification define +a position in a 64-bit bitmap. + +The signaling of notifications can interchangeably happen between NWd and SWd +FF-A endpoints. + +The SPMC is in charge of managing notifications from SPs to SPs, from SPs to +VMs, and from VMs to SPs. An hypervisor component would only manage +notifications from VMs to VMs. Given the SPMC has no visibility of the endpoints +deployed in NWd, the Hypervisor or OS kernel must invoke the interface +FFA_NOTIFICATION_BITMAP_CREATE to allocate the notifications bitmap per FF-A +endpoint in the NWd that supports it. + +A sender can signal notifications once the receiver has provided it with +permissions. Permissions are provided by invoking the interface +FFA_NOTIFICATION_BIND. + +Notifications are signaled by invoking FFA_NOTIFICATION_SET. Henceforth +they are considered to be in a pending sate. The receiver can retrieve its +pending notifications invoking FFA_NOTIFICATION_GET, which, from that moment, +are considered to be handled. + +Per the FF-A v1.1 spec, each FF-A endpoint must be associated with a scheduler +that is in charge of donating CPU cycles for notifications handling. The +FF-A driver calls FFA_NOTIFICATION_INFO_GET to retrieve the information about +which FF-A endpoints have pending notifications. The receiver scheduler is +called and informed by the FF-A driver, and it should allocate CPU cycles to the +receiver. + +There are two types of notifications supported: + +- Global, which are targeted to a FF-A endpoint and can be handled within any of + its execution contexts, as determined by the scheduler of the system. +- Per-vCPU, which are targeted to a FF-A endpoint and to be handled within a + a specific execution context, as determined by the sender. + +The type of a notification is set when invoking FFA_NOTIFICATION_BIND to give +permissions to the sender. + +Notification signaling resorts to two interrupts: + +- Schedule Receiver Interrupt: non-secure physical interrupt to be handled by + the FF-A driver within the receiver scheduler. At initialization the SPMC + donates a SGI ID chosen from the secure SGI IDs range and configures it as + non-secure. The SPMC triggers this SGI on the currently running core when + there are pending notifications, and the respective receivers need CPU cycles + to handle them. +- Notifications Pending Interrupt: virtual interrupt to be handled by the + receiver of the notification. Set when there are pending notifications for the + given secure partition. The NPI is pended when the NWd relinquishes CPU cycles + to an SP. + +The notifications receipt support is enabled in the partition FF-A manifest. + +Mandatory interfaces +-------------------- + +The following interfaces are exposed to SPs: + +- ``FFA_VERSION`` +- ``FFA_FEATURES`` +- ``FFA_RX_RELEASE`` +- ``FFA_RXTX_MAP`` +- ``FFA_RXTX_UNMAP`` +- ``FFA_PARTITION_INFO_GET`` +- ``FFA_ID_GET`` +- ``FFA_MSG_WAIT`` +- ``FFA_MSG_SEND_DIRECT_REQ`` +- ``FFA_MSG_SEND_DIRECT_RESP`` +- ``FFA_MEM_DONATE`` +- ``FFA_MEM_LEND`` +- ``FFA_MEM_SHARE`` +- ``FFA_MEM_RETRIEVE_REQ`` +- ``FFA_MEM_RETRIEVE_RESP`` +- ``FFA_MEM_RELINQUISH`` +- ``FFA_MEM_FRAG_RX`` +- ``FFA_MEM_FRAG_TX`` +- ``FFA_MEM_RECLAIM`` +- ``FFA_RUN`` + +As part of the FF-A v1.1 support, the following interfaces were added: + + - ``FFA_NOTIFICATION_BITMAP_CREATE`` + - ``FFA_NOTIFICATION_BITMAP_DESTROY`` + - ``FFA_NOTIFICATION_BIND`` + - ``FFA_NOTIFICATION_UNBIND`` + - ``FFA_NOTIFICATION_SET`` + - ``FFA_NOTIFICATION_GET`` + - ``FFA_NOTIFICATION_INFO_GET`` + - ``FFA_SPM_ID_GET`` + - ``FFA_SECONDARY_EP_REGISTER`` + - ``FFA_MEM_PERM_GET`` + - ``FFA_MEM_PERM_SET`` + - ``FFA_MSG_SEND2`` + - ``FFA_RX_ACQUIRE`` + +FFA_VERSION +~~~~~~~~~~~ + +``FFA_VERSION`` requires a *requested_version* parameter from the caller. +The returned value depends on the caller: + +- Hypervisor or OS kernel in NS-EL1/EL2: the SPMD returns the SPMC version + specified in the SPMC manifest. +- SP: the SPMC returns its own implemented version. +- SPMC at S-EL1/S-EL2: the SPMD returns its own implemented version. + +FFA_FEATURES +~~~~~~~~~~~~ + +FF-A features supported by the SPMC may be discovered by secure partitions at +boot (that is prior to NWd is booted) or run-time. + +The SPMC calling FFA_FEATURES at secure physical FF-A instance always get +FFA_SUCCESS from the SPMD. + +The request made by an Hypervisor or OS kernel is forwarded to the SPMC and +the response relayed back to the NWd. + +FFA_RXTX_MAP/FFA_RXTX_UNMAP +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When invoked from a secure partition FFA_RXTX_MAP maps the provided send and +receive buffers described by their IPAs to the SP EL1&0 Stage-2 translation +regime as secure buffers in the MMU descriptors. + +When invoked from the Hypervisor or OS kernel, the buffers are mapped into the +SPMC EL2 Stage-1 translation regime and marked as NS buffers in the MMU +descriptors. The provided addresses may be owned by a VM in the normal world, +which is expected to receive messages from the secure world. The SPMC will in +this case allocate internal state structures to facilitate RX buffer access +synchronization (through FFA_RX_ACQUIRE interface), and to permit SPs to send +messages. + +The FFA_RXTX_UNMAP unmaps the RX/TX pair from the translation regime of the +caller, either it being the Hypervisor or OS kernel, as well as a secure +partition. + +FFA_PARTITION_INFO_GET +~~~~~~~~~~~~~~~~~~~~~~ + +Partition info get call can originate: + +- from SP to SPMC +- from Hypervisor or OS kernel to SPMC. The request is relayed by the SPMD. + +FFA_ID_GET +~~~~~~~~~~ + +The FF-A id space is split into a non-secure space and secure space: + +- FF-A ID with bit 15 clear relates to VMs. +- FF-A ID with bit 15 set related to SPs. +- FF-A IDs 0, 0xffff, 0x8000 are assigned respectively to the Hypervisor, SPMD + and SPMC. + +The SPMD returns: + +- The default zero value on invocation from the Hypervisor. +- The ``spmc_id`` value specified in the SPMC manifest on invocation from + the SPMC (see `SPMC manifest`_) + +This convention helps the SPMC to determine the origin and destination worlds in +an FF-A ABI invocation. In particular the SPMC shall filter unauthorized +transactions in its world switch routine. It must not be permitted for a VM to +use a secure FF-A ID as origin world by spoofing: + +- A VM-to-SP direct request/response shall set the origin world to be non-secure + (FF-A ID bit 15 clear) and destination world to be secure (FF-A ID bit 15 + set). +- Similarly, an SP-to-SP direct request/response shall set the FF-A ID bit 15 + for both origin and destination IDs. + +An incoming direct message request arriving at SPMD from NWd is forwarded to +SPMC without a specific check. The SPMC is resumed through eret and "knows" the +message is coming from normal world in this specific code path. Thus the origin +endpoint ID must be checked by SPMC for being a normal world ID. + +An SP sending a direct message request must have bit 15 set in its origin +endpoint ID and this can be checked by the SPMC when the SP invokes the ABI. + +The SPMC shall reject the direct message if the claimed world in origin endpoint +ID is not consistent: + +- It is either forwarded by SPMD and thus origin endpoint ID must be a "normal + world ID", +- or initiated by an SP and thus origin endpoint ID must be a "secure world ID". + + +FFA_MSG_SEND_DIRECT_REQ/FFA_MSG_SEND_DIRECT_RESP +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This is a mandatory interface for secure partitions consisting in direct request +and responses with the following rules: + +- An SP can send a direct request to another SP. +- An SP can receive a direct request from another SP. +- An SP can send a direct response to another SP. +- An SP cannot send a direct request to an Hypervisor or OS kernel. +- An Hypervisor or OS kernel can send a direct request to an SP. +- An SP can send a direct response to an Hypervisor or OS kernel. + +FFA_NOTIFICATION_BITMAP_CREATE/FFA_NOTIFICATION_BITMAP_DESTROY +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The secure partitions notifications bitmap are statically allocated by the SPMC. +Hence, this interface is not to be issued by secure partitions. + +At initialization, the SPMC is not aware of VMs/partitions deployed in the +normal world. Hence, the Hypervisor or OS kernel must use both ABIs for SPMC +to be prepared to handle notifications for the provided VM ID. + +FFA_NOTIFICATION_BIND/FFA_NOTIFICATION_UNBIND +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Pair of interfaces to manage permissions to signal notifications. Prior to +handling notifications, an FF-A endpoint must allow a given sender to signal a +bitmap of notifications. + +If the receiver doesn't have notification support enabled in its FF-A manifest, +it won't be able to bind notifications, hence forbidding it to receive any +notifications. + +FFA_NOTIFICATION_SET/FFA_NOTIFICATION_GET +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +FFA_NOTIFICATION_GET retrieves all pending global notifications and +per-vCPU notifications targeted to the current vCPU. + +Hafnium maintains a global count of pending notifications which gets incremented +and decremented when handling FFA_NOTIFICATION_SET and FFA_NOTIFICATION_GET +respectively. A delayed SRI is triggered if the counter is non-zero when the +SPMC returns to normal world. + +FFA_NOTIFICATION_INFO_GET +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Hafnium maintains a global count of pending notifications whose information +has been retrieved by this interface. The count is incremented and decremented +when handling FFA_NOTIFICATION_INFO_GET and FFA_NOTIFICATION_GET respectively. +It also tracks notifications whose information has been retrieved individually, +such that it avoids duplicating returned information for subsequent calls to +FFA_NOTIFICATION_INFO_GET. For each notification, this state information is +reset when receiver called FFA_NOTIFICATION_GET to retrieve them. + +FFA_SPM_ID_GET +~~~~~~~~~~~~~~ + +Returns the FF-A ID allocated to an SPM component which can be one of SPMD +or SPMC. + +At initialization, the SPMC queries the SPMD for the SPMC ID, using the +FFA_ID_GET interface, and records it. The SPMC can also query the SPMD ID using +the FFA_SPM_ID_GET interface at the secure physical FF-A instance. + +Secure partitions call this interface at the virtual FF-A instance, to which +the SPMC returns the priorly retrieved SPMC ID. + +The Hypervisor or OS kernel can issue the FFA_SPM_ID_GET call handled by the +SPMD, which returns the SPMC ID. + +FFA_SECONDARY_EP_REGISTER +~~~~~~~~~~~~~~~~~~~~~~~~~ + +When the SPMC boots, all secure partitions are initialized on their primary +Execution Context. + +The FFA_SECONDARY_EP_REGISTER interface is to be used by a secure partition +from its first execution context, to provide the entry point address for +secondary execution contexts. + +A secondary EC is first resumed either upon invocation of PSCI_CPU_ON from +the NWd or by invocation of FFA_RUN. + +FFA_RX_ACQUIRE/FFA_RX_RELEASE +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The RX buffers can be used to pass information to an FF-A endpoint in the +following scenarios: + + - When it was targetted by a FFA_MSG_SEND2 invokation from another endpoint. + - Return the result of calling ``FFA_PARTITION_INFO_GET``. + - In a memory share operation, as part of the ``FFA_MEM_RETRIEVE_RESP``, + with the memory descriptor of the shared memory. + +If a normal world VM is expected to exchange messages with secure world, +its RX/TX buffer addresses are forwarded to the SPMC via FFA_RXTX_MAP ABI, +and are from this moment owned by the SPMC. +The hypervisor must call the FFA_RX_ACQUIRE interface before attempting +to use the RX buffer, in any of the aforementioned scenarios. A successful +call to FFA_RX_ACQUIRE transfers ownership of RX buffer to hypervisor, such +that it can be safely used. + +The FFA_RX_RELEASE interface is used after the FF-A endpoint is done with +processing the data received in its RX buffer. If the RX buffer has been +acquired by the hypervisor, the FFA_RX_RELEASE call must be forwarded to +the SPMC to reestablish SPMC's RX ownership. + +An attempt from an SP to send a message to a normal world VM whose RX buffer +was acquired by the hypervisor fails with error code FFA_BUSY, to preserve +the RX buffer integrity. +The operation could then be conducted after FFA_RX_RELEASE. + +FFA_MSG_SEND2 +~~~~~~~~~~~~~ + +Hafnium copies a message from the sender TX buffer into receiver's RX buffer. +For messages from SPs to VMs, operation is only possible if the SPMC owns +the receiver's RX buffer. + +Both receiver and sender need to enable support for indirect messaging, +in their respective partition manifest. The discovery of support +of such feature can be done via FFA_PARTITION_INFO_GET. + +On a successful message send, Hafnium pends an RX buffer full framework +notification for the receiver, to inform it about a message in the RX buffer. + +The handling of framework notifications is similar to that of +global notifications. Binding of these is not necessary, as these are +reserved to be used by the hypervisor or SPMC. + +SPMC-SPMD direct requests/responses +----------------------------------- + +Implementation-defined FF-A IDs are allocated to the SPMC and SPMD. +Using those IDs in source/destination fields of a direct request/response +permits SPMD to SPMC communication and either way. + +- SPMC to SPMD direct request/response uses SMC conduit. +- SPMD to SPMC direct request/response uses ERET conduit. + +This is used in particular to convey power management messages. + +Memory Sharing +-------------- + +Hafnium implements the following memory sharing interfaces: + + - ``FFA_MEM_SHARE`` - for shared access between lender and borrower. + - ``FFA_MEM_LEND`` - borrower to obtain exclusive access, though lender + retains ownership of the memory. + - ``FFA_MEM_DONATE`` - lender permanently relinquishes ownership of memory + to the borrower. + +The ``FFA_MEM_RETRIEVE_REQ`` interface is for the borrower to request the +memory to be mapped into its address space: for S-EL1 partitions the SPM updates +their stage 2 translation regime; for S-EL0 partitions the SPM updates their +stage 1 translation regime. On a successful call, the SPMC responds back with +``FFA_MEM_RETRIEVE_RESP``. + +The ``FFA_MEM_RELINQUISH`` interface is for when the borrower is done with using +a memory region. + +The ``FFA_MEM_RECLAIM`` interface is for the owner of the memory to reestablish +its ownership and exclusive access to the memory shared. + +The memory transaction descriptors are transmitted via RX/TX buffers. In +situations where the size of the memory transaction descriptor exceeds the +size of the RX/TX buffers, Hafnium provides support for fragmented transmission +of the full transaction descriptor. The ``FFA_MEM_FRAG_RX`` and ``FFA_MEM_FRAG_TX`` +interfaces are for receiving and transmitting the next fragment, respectively. + +If lender and borrower(s) are SPs, all memory sharing operations are supported. + +Hafnium also supports memory sharing operations between the normal world and the +secure world. If there is an SP involved, the SPMC allocates data to track the +state of the operation. + +The SPMC is also the designated allocator for the memory handle. The hypervisor +or OS kernel has the possibility to rely on the SPMC to maintain the state +of the operation, thus saving memory. +A lender SP can only donate NS memory to a borrower from the normal world. + +The SPMC supports the hypervisor retrieve request, as defined by the FF-A +v1.1 EAC0 specification, in section 16.4.3. The intent is to aid with operations +that the hypervisor must do for a VM retriever. For example, when handling +an FFA_MEM_RECLAIM, if the hypervisor relies on SPMC to keep the state +of the operation, the hypervisor retrieve request can be used to obtain +that state information, do the necessary validations, and update stage 2 +memory translation. + +Hafnium also supports memory lend and share targetting multiple borrowers. +This is the case for a lender SP to multiple SPs, and for a lender VM to +multiple endpoints (from both secure world and normal world). If there is +at least one borrower VM, the hypervisor is in charge of managing its +stage 2 translation on a successful memory retrieve. +The semantics of ``FFA_MEM_DONATE`` implies ownership transmission, +which should target only one partition. + +The memory share interfaces are backwards compatible with memory transaction +descriptors from FF-A v1.0. These get translated to FF-A v1.1 descriptors for +Hafnium's internal processing of the operation. If the FF-A version of a +borrower is v1.0, Hafnium provides FF-A v1.0 compliant memory transaction +descriptors on memory retrieve response. + +PE MMU configuration +-------------------- + +With secure virtualization enabled (``HCR_EL2.VM = 1``) and for S-EL1 +partitions, two IPA spaces (secure and non-secure) are output from the +secure EL1&0 Stage-1 translation. +The EL1&0 Stage-2 translation hardware is fed by: + +- A secure IPA when the SP EL1&0 Stage-1 MMU is disabled. +- One of secure or non-secure IPA when the secure EL1&0 Stage-1 MMU is enabled. + +``VTCR_EL2`` and ``VSTCR_EL2`` provide configuration bits for controlling the +NS/S IPA translations. The following controls are set up: +``VSTCR_EL2.SW = 0`` , ``VSTCR_EL2.SA = 0``, ``VTCR_EL2.NSW = 0``, +``VTCR_EL2.NSA = 1``: + +- Stage-2 translations for the NS IPA space access the NS PA space. +- Stage-2 translation table walks for the NS IPA space are to the secure PA space. + +Secure and non-secure IPA regions (rooted to by ``VTTBR_EL2`` and ``VSTTBR_EL2``) +use the same set of Stage-2 page tables within a SP. + +The ``VTCR_EL2/VSTCR_EL2/VTTBR_EL2/VSTTBR_EL2`` virtual address space +configuration is made part of a vCPU context. + +For S-EL0 partitions with VHE enabled, a single secure EL2&0 Stage-1 translation +regime is used for both Hafnium and the partition. + +Schedule modes and SP Call chains +--------------------------------- + +An SP execution context is said to be in SPMC scheduled mode if CPU cycles are +allocated to it by SPMC. Correspondingly, an SP execution context is said to be +in Normal world scheduled mode if CPU cycles are allocated by the normal world. + +A call chain represents all SPs in a sequence of invocations of a direct message +request. When execution on a PE is in the secure state, only a single call chain +that runs in the Normal World scheduled mode can exist. FF-A v1.1 spec allows +any number of call chains to run in the SPMC scheduled mode but the Hafnium +SPMC restricts the number of call chains in SPMC scheduled mode to only one for +keeping the implementation simple. + +Partition runtime models +------------------------ + +The runtime model of an endpoint describes the transitions permitted for an +execution context between various states. These are the four partition runtime +models supported (refer to `[1]`_ section 7): + + - RTM_FFA_RUN: runtime model presented to an execution context that is + allocated CPU cycles through FFA_RUN interface. + - RTM_FFA_DIR_REQ: runtime model presented to an execution context that is + allocated CPU cycles through FFA_MSG_SEND_DIRECT_REQ interface. + - RTM_SEC_INTERRUPT: runtime model presented to an execution context that is + allocated CPU cycles by SPMC to handle a secure interrupt. + - RTM_SP_INIT: runtime model presented to an execution context that is + allocated CPU cycles by SPMC to initialize its state. + +If an endpoint execution context attempts to make an invalid transition or a +valid transition that could lead to a loop in the call chain, SPMC denies the +transition with the help of above runtime models. + +Interrupt management +-------------------- + +GIC ownership +~~~~~~~~~~~~~ + +The SPMC owns the GIC configuration. Secure and non-secure interrupts are +trapped at S-EL2. The SPMC manages interrupt resources and allocates interrupt +IDs based on SP manifests. The SPMC acknowledges physical interrupts and injects +virtual interrupts by setting the use of vIRQ/vFIQ bits before resuming a SP. + +Abbreviations: + + - NS-Int: A non-secure physical interrupt. It requires a switch to the normal + world to be handled if it triggers while execution is in secure world. + - Other S-Int: A secure physical interrupt targeted to an SP different from + the one that is currently running. + - Self S-Int: A secure physical interrupt targeted to the SP that is currently + running. + +Non-secure interrupt handling +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section documents the actions supported in SPMC in response to a non-secure +interrupt as per the guidance provided by FF-A v1.1 EAC0 specification. +An SP specifies one of the following actions in its partition manifest: + + - Non-secure interrupt is signaled. + - Non-secure interrupt is signaled after a managed exit. + - Non-secure interrupt is queued. + +An SP execution context in a call chain could specify a less permissive action +than subsequent SP execution contexts in the same call chain. The less +permissive action takes precedence over the more permissive actions specified +by the subsequent execution contexts. Please refer to FF-A v1.1 EAC0 section +8.3.1 for further explanation. + +Secure interrupt handling +~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section documents the support implemented for secure interrupt handling in +SPMC as per the guidance provided by FF-A v1.1 EAC0 specification. +The following assumptions are made about the system configuration: + + - In the current implementation, S-EL1 SPs are expected to use the para + virtualized ABIs for interrupt management rather than accessing the virtual + GIC interface. + - Unless explicitly stated otherwise, this support is applicable only for + S-EL1 SPs managed by SPMC. + - Secure interrupts are configured as G1S or G0 interrupts. + - All physical interrupts are routed to SPMC when running a secure partition + execution context. + - All endpoints with multiple execution contexts have their contexts pinned + to corresponding CPUs. Hence, a secure virtual interrupt cannot be signaled + to a target vCPU that is currently running or blocked on a different + physical CPU. + +A physical secure interrupt could trigger while CPU is executing in normal world +or secure world. +The action of SPMC for a secure interrupt depends on: the state of the target +execution context of the SP that is responsible for handling the interrupt; +whether the interrupt triggered while execution was in normal world or secure +world. + +Secure interrupt signaling mechanisms +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Signaling refers to the mechanisms used by SPMC to indicate to the SP execution +context that it has a pending virtual interrupt and to further run the SP +execution context, such that it can handle the virtual interrupt. SPMC uses +either the FFA_INTERRUPT interface with ERET conduit or vIRQ signal for signaling +to S-EL1 SPs. When normal world execution is preempted by a secure interrupt, +the SPMD uses the FFA_INTERRUPT ABI with ERET conduit to signal interrupt to SPMC +running in S-EL2. + ++-----------+---------+---------------+---------------------------------------+ +| SP State | Conduit | Interface and | Description | +| | | parameters | | ++-----------+---------+---------------+---------------------------------------+ +| WAITING | ERET, | FFA_INTERRUPT,| SPMC signals to SP the ID of pending | +| | vIRQ | Interrupt ID | interrupt. It pends vIRQ signal and | +| | | | resumes execution context of SP | +| | | | through ERET. | ++-----------+---------+---------------+---------------------------------------+ +| BLOCKED | ERET, | FFA_INTERRUPT | SPMC signals to SP that an interrupt | +| | vIRQ | | is pending. It pends vIRQ signal and | +| | | | resumes execution context of SP | +| | | | through ERET. | ++-----------+---------+---------------+---------------------------------------+ +| PREEMPTED | vIRQ | NA | SPMC pends the vIRQ signal but does | +| | | | not resume execution context of SP. | ++-----------+---------+---------------+---------------------------------------+ +| RUNNING | ERET, | NA | SPMC pends the vIRQ signal and resumes| +| | vIRQ | | execution context of SP through ERET. | ++-----------+---------+---------------+---------------------------------------+ + +Secure interrupt completion mechanisms +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A SP signals secure interrupt handling completion to the SPMC through the +following mechanisms: + + - ``FFA_MSG_WAIT`` ABI if it was in WAITING state. + - ``FFA_RUN`` ABI if its was in BLOCKED state. + +This is a remnant of SPMC implementation based on the FF-A v1.0 specification. +In the current implementation, S-EL1 SPs use the para-virtualized HVC interface +implemented by SPMC to perform priority drop and interrupt deactivation (SPMC +configures EOImode = 0, i.e. priority drop and deactivation are done together). +The SPMC performs checks to deny the state transition upon invocation of +either FFA_MSG_WAIT or FFA_RUN interface if the SP didn't perform the +deactivation of the secure virtual interrupt. + +If the current SP execution context was preempted by a secure interrupt to be +handled by execution context of target SP, SPMC resumes current SP after signal +completion by target SP execution context. + +Actions for a secure interrupt triggered while execution is in normal world +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++-------------------+----------+-----------------------------------------------+ +| State of target | Action | Description | +| execution context | | | ++-------------------+----------+-----------------------------------------------+ +| WAITING | Signaled | This starts a new call chain in SPMC scheduled| +| | | mode. | ++-------------------+----------+-----------------------------------------------+ +| PREEMPTED | Queued | The target execution must have been preempted | +| | | by a non-secure interrupt. SPMC queues the | +| | | secure virtual interrupt now. It is signaled | +| | | when the target execution context next enters | +| | | the RUNNING state. | ++-------------------+----------+-----------------------------------------------+ +| BLOCKED, RUNNING | NA | The target execution context is blocked or | +| | | running on a different CPU. This is not | +| | | supported by current SPMC implementation and | +| | | execution hits panic. | ++-------------------+----------+-----------------------------------------------+ + +If normal world execution was preempted by a secure interrupt, SPMC uses +FFA_NORMAL_WORLD_RESUME ABI to indicate completion of secure interrupt handling +and further returns execution to normal world. + +The following figure describes interrupt handling flow when a secure interrupt +triggers while execution is in normal world: + +.. image:: ../resources/diagrams/ffa-secure-interrupt-handling-nwd.png + +A brief description of the events: + + - 1) Secure interrupt triggers while normal world is running. + - 2) FIQ gets trapped to EL3. + - 3) SPMD signals secure interrupt to SPMC at S-EL2 using FFA_INTERRUPT ABI. + - 4) SPMC identifies target vCPU of SP and injects virtual interrupt (pends + vIRQ). + - 5) Assuming SP1 vCPU is in WAITING state, SPMC signals virtual interrupt + using FFA_INTERRUPT with interrupt id as an argument and resumes the SP1 + vCPU using ERET in SPMC scheduled mode. + - 6) Execution traps to vIRQ handler in SP1 provided that the virtual + interrupt is not masked i.e., PSTATE.I = 0 + - 7) SP1 queries for the pending virtual interrupt id using a paravirtualized + HVC call. SPMC clears the pending virtual interrupt state management + and returns the pending virtual interrupt id. + - 8) SP1 services the virtual interrupt and invokes the paravirtualized + de-activation HVC call. SPMC de-activates the physical interrupt, + clears the fields tracking the secure interrupt and resumes SP1 vCPU. + - 9) SP1 performs secure interrupt completion through FFA_MSG_WAIT ABI. + - 10) SPMC returns control to EL3 using FFA_NORMAL_WORLD_RESUME. + - 11) EL3 resumes normal world execution. + +Actions for a secure interrupt triggered while execution is in secure world +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++-------------------+----------+------------------------------------------------+ +| State of target | Action | Description | +| execution context | | | ++-------------------+----------+------------------------------------------------+ +| WAITING | Signaled | This starts a new call chain in SPMC scheduled | +| | | mode. | ++-------------------+----------+------------------------------------------------+ +| PREEMPTED by Self | Signaled | The target execution context reenters the | +| S-Int | | RUNNING state to handle the secure virtual | +| | | interrupt. | ++-------------------+----------+------------------------------------------------+ +| PREEMPTED by | Queued | SPMC queues the secure virtual interrupt now. | +| NS-Int | | It is signaled when the target execution | +| | | context next enters the RUNNING state. | ++-------------------+----------+------------------------------------------------+ +| BLOCKED | Signaled | Both preempted and target execution contexts | +| | | must have been part of the Normal world | +| | | scheduled call chain. Refer scenario 1 of | +| | | Table 8.4 in the FF-A v1.1 EAC0 spec. | ++-------------------+----------+------------------------------------------------+ +| RUNNING | NA | The target execution context is running on a | +| | | different CPU. This scenario is not supported | +| | | by current SPMC implementation and execution | +| | | hits panic. | ++-------------------+----------+------------------------------------------------+ + +The following figure describes interrupt handling flow when a secure interrupt +triggers while execution is in secure world. We assume OS kernel sends a direct +request message to SP1. Further, SP1 sends a direct request message to SP2. SP1 +enters BLOCKED state and SPMC resumes SP2. + +.. image:: ../resources/diagrams/ffa-secure-interrupt-handling-swd.png + +A brief description of the events: + + - 1) Secure interrupt triggers while SP2 is running. + - 2) SP2 gets preempted and execution traps to SPMC as IRQ. + - 3) SPMC finds the target vCPU of secure partition responsible for handling + this secure interrupt. In this scenario, it is SP1. + - 4) SPMC pends vIRQ for SP1 and signals through FFA_INTERRUPT interface. + SPMC further resumes SP1 through ERET conduit. Note that SP1 remains in + Normal world schedule mode. + - 6) Execution traps to vIRQ handler in SP1 provided that the virtual + interrupt is not masked i.e., PSTATE.I = 0 + - 7) SP1 queries for the pending virtual interrupt id using a paravirtualized + HVC call. SPMC clears the pending virtual interrupt state management + and returns the pending virtual interrupt id. + - 8) SP1 services the virtual interrupt and invokes the paravirtualized + de-activation HVC call. SPMC de-activates the physical interrupt and + clears the fields tracking the secure interrupt and resumes SP1 vCPU. + - 9) Since SP1 direct request completed with FFA_INTERRUPT, it resumes the + direct request to SP2 by invoking FFA_RUN. + - 9) SPMC resumes the pre-empted vCPU of SP2. + +EL3 interrupt handling +~~~~~~~~~~~~~~~~~~~~~~ + +In GICv3 based systems, EL3 interrupts are configured as Group0 secure +interrupts. Execution traps to SPMC when a Group0 interrupt triggers while an +SP is running. Further, SPMC running at S-EL2 uses FFA_EL3_INTR_HANDLE ABI to +request EL3 platform firmware to handle a pending Group0 interrupt. +Similarly, SPMD registers a handler with interrupt management framework to +delegate handling of Group0 interrupt to the platform if the interrupt triggers +in normal world. + + - Platform hook + + - plat_spmd_handle_group0_interrupt + + SPMD provides platform hook to handle Group0 secure interrupts. In the + current design, SPMD expects the platform not to delegate handling to the + NWd (such as through SDEI) while processing Group0 interrupts. + +Power management +---------------- + +In platforms with or without secure virtualization: + +- The NWd owns the platform PM policy. +- The Hypervisor or OS kernel is the component initiating PSCI service calls. +- The EL3 PSCI library is in charge of the PM coordination and control + (eventually writing to platform registers). +- While coordinating PM events, the PSCI library calls backs into the Secure + Payload Dispatcher for events the latter has statically registered to. + +When using the SPMD as a Secure Payload Dispatcher: + +- A power management event is relayed through the SPD hook to the SPMC. +- In the current implementation only cpu on (svc_on_finish) and cpu off + (svc_off) hooks are registered. +- The behavior for the cpu on event is described in `Secondary cores boot-up`_. + The SPMC is entered through its secondary physical core entry point. +- The cpu off event occurs when the NWd calls PSCI_CPU_OFF. The PM event is + signaled to the SPMC through a power management framework message. + It consists in a SPMD-to-SPMC direct request/response (`SPMC-SPMD direct + requests/responses`_) conveying the event details and SPMC response. + The SPMD performs a synchronous entry into the SPMC. The SPMC is entered and + updates its internal state to reflect the physical core is being turned off. + In the current implementation no SP is resumed as a consequence. This behavior + ensures a minimal support for CPU hotplug e.g. when initiated by the NWd linux + userspace. + +Arm architecture extensions for security hardening +================================================== + +Hafnium supports the following architecture extensions for security hardening: + +- Pointer authentication (FEAT_PAuth): the extension permits detection of forged + pointers used by ROP type of attacks through the signing of the pointer + value. Hafnium is built with the compiler branch protection option to permit + generation of a pointer authentication code for return addresses (pointer + authentication for instructions). The APIA key is used while Hafnium runs. + A random key is generated at boot time and restored upon entry into Hafnium + at run-time. APIA and other keys (APIB, APDA, APDB, APGA) are saved/restored + in vCPU contexts permitting to enable pointer authentication in VMs/SPs. +- Branch Target Identification (FEAT_BTI): the extension permits detection of + unexpected indirect branches used by JOP type of attacks. Hafnium is built + with the compiler branch protection option, inserting land pads at function + prologues that are reached by indirect branch instructions (BR/BLR). + Hafnium code pages are marked as guarded in the EL2 Stage-1 MMU descriptors + such that an indirect branch must always target a landpad. A fault is + triggered otherwise. VMs/SPs can (independently) mark their code pages as + guarded in the EL1&0 Stage-1 translation regime. +- Memory Tagging Extension (FEAT_MTE): the option permits detection of out of + bound memory array accesses or re-use of an already freed memory region. + Hafnium enables the compiler option permitting to leverage MTE stack tagging + applied to core stacks. Core stacks are marked as normal tagged memory in the + EL2 Stage-1 translation regime. A synchronous data abort is generated upon tag + check failure on load/stores. A random seed is generated at boot time and + restored upon entry into Hafnium. MTE system registers are saved/restored in + vCPU contexts permitting MTE usage from VMs/SPs. + +SMMUv3 support in Hafnium +========================= + +An SMMU is analogous to an MMU in a CPU. It performs address translations for +Direct Memory Access (DMA) requests from system I/O devices. +The responsibilities of an SMMU include: + +- Translation: Incoming DMA requests are translated from bus address space to + system physical address space using translation tables compliant to + Armv8/Armv7 VMSA descriptor format. +- Protection: An I/O device can be prohibited from read, write access to a + memory region or allowed. +- Isolation: Traffic from each individial device can be independently managed. + The devices are differentiated from each other using unique translation + tables. + +The following diagram illustrates a typical SMMU IP integrated in a SoC with +several I/O devices along with Interconnect and Memory system. + +.. image:: ../resources/diagrams/MMU-600.png + +SMMU has several versions including SMMUv1, SMMUv2 and SMMUv3. Hafnium provides +support for SMMUv3 driver in both normal and secure world. A brief introduction +of SMMUv3 functionality and the corresponding software support in Hafnium is +provided here. + +SMMUv3 features +--------------- + +- SMMUv3 provides Stage1, Stage2 translation as well as nested (Stage1 + Stage2) + translation support. It can either bypass or abort incoming translations as + well. +- Traffic (memory transactions) from each upstream I/O peripheral device, + referred to as Stream, can be independently managed using a combination of + several memory based configuration structures. This allows the SMMUv3 to + support a large number of streams with each stream assigned to a unique + translation context. +- Support for Armv8.1 VMSA where the SMMU shares the translation tables with + a Processing Element. AArch32(LPAE) and AArch64 translation table format + are supported by SMMUv3. +- SMMUv3 offers non-secure stream support with secure stream support being + optional. Logically, SMMUv3 behaves as if there is an indepdendent SMMU + instance for secure and non-secure stream support. +- It also supports sub-streams to differentiate traffic from a virtualized + peripheral associated with a VM/SP. +- Additionally, SMMUv3.2 provides support for PEs implementing Armv8.4-A + extensions. Consequently, SPM depends on Secure EL2 support in SMMUv3.2 + for providing Secure Stage2 translation support to upstream peripheral + devices. + +SMMUv3 Programming Interfaces +----------------------------- + +SMMUv3 has three software interfaces that are used by the Hafnium driver to +configure the behaviour of SMMUv3 and manage the streams. + +- Memory based data strutures that provide unique translation context for + each stream. +- Memory based circular buffers for command queue and event queue. +- A large number of SMMU configuration registers that are memory mapped during + boot time by Hafnium driver. Except a few registers, all configuration + registers have independent secure and non-secure versions to configure the + behaviour of SMMUv3 for translation of secure and non-secure streams + respectively. + +Peripheral device manifest +-------------------------- + +Currently, SMMUv3 driver in Hafnium only supports dependent peripheral devices. +These devices are dependent on PE endpoint to initiate and receive memory +management transactions on their behalf. The acccess to the MMIO regions of +any such device is assigned to the endpoint during boot. Moreover, SMMUv3 driver +uses the same stage 2 translations for the device as those used by partition +manager on behalf of the PE endpoint. This ensures that the peripheral device +has the same visibility of the physical address space as the endpoint. The +device node of the corresponding partition manifest (refer to `[1]`_ section 3.2 +) must specify these additional properties for each peripheral device in the +system : + +- smmu-id: This field helps to identify the SMMU instance that this device is + upstream of. +- stream-ids: List of stream IDs assigned to this device. + +.. code:: shell + + smmuv3-testengine { + base-address = <0x00000000 0x2bfe0000>; + pages-count = <32>; + attributes = <0x3>; + smmu-id = <0>; + stream-ids = <0x0 0x1>; + interrupts = <0x2 0x3>, <0x4 0x5>; + exclusive-access; + }; + +SMMUv3 driver limitations +------------------------- + +The primary design goal for the Hafnium SMMU driver is to support secure +streams. + +- Currently, the driver only supports Stage2 translations. No support for + Stage1 or nested translations. +- Supports only AArch64 translation format. +- No support for features such as PCI Express (PASIDs, ATS, PRI), MSI, RAS, + Fault handling, Performance Monitor Extensions, Event Handling, MPAM. +- No support for independent peripheral devices. + +S-EL0 Partition support +======================= +The SPMC (Hafnium) has limited capability to run S-EL0 FF-A partitions using +FEAT_VHE (mandatory with ARMv8.1 in non-secure state, and in secure world +with ARMv8.4 and FEAT_SEL2). + +S-EL0 partitions are useful for simple partitions that don't require full +Trusted OS functionality. It is also useful to reduce jitter and cycle +stealing from normal world since they are more lightweight than VMs. + +S-EL0 partitions are presented, loaded and initialized the same as S-EL1 VMs by +the SPMC. They are differentiated primarily by the 'exception-level' property +and the 'execution-ctx-count' property in the SP manifest. They are host apps +under the single EL2&0 Stage-1 translation regime controlled by the SPMC and +call into the SPMC through SVCs as opposed to HVCs and SMCs. These partitions +can use FF-A defined services (FFA_MEM_PERM_*) to update or change permissions +for memory regions. + +S-EL0 partitions are required by the FF-A specification to be UP endpoints, +capable of migrating, and the SPMC enforces this requirement. The SPMC allows +a S-EL0 partition to accept a direct message from secure world and normal world, +and generate direct responses to them. +All S-EL0 partitions must use AArch64. AArch32 S-EL0 partitions are not supported. + +Memory sharing, indirect messaging, and notifications functionality with S-EL0 +partitions is supported. + +Interrupt handling is not supported with S-EL0 partitions and is work in +progress. + +References +========== + +.. _[1]: + +[1] `Arm Firmware Framework for Arm A-profile <https://developer.arm.com/docs/den0077/latest>`__ + +.. _[2]: + +[2] :ref:`Secure Partition Manager using MM interface<Secure Partition Manager (MM)>` + +.. _[3]: + +[3] `Trusted Boot Board Requirements +Client <https://developer.arm.com/documentation/den0006/d/>`__ + +.. _[4]: + +[4] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/lib/el3_runtime/aarch64/context.S#n45 + +.. _[5]: + +[5] https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/spm/cactus/plat/arm/fvp/fdts/cactus.dts + +.. _[6]: + +[6] https://trustedfirmware-a.readthedocs.io/en/latest/components/ffa-manifest-binding.html + +.. _[7]: + +[7] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/plat/arm/board/fvp/fdts/fvp_spmc_manifest.dts + +.. _[8]: + +[8] https://lists.trustedfirmware.org/archives/list/tf-a@lists.trustedfirmware.org/thread/CFQFGU6H2D5GZYMUYGTGUSXIU3OYZP6U/ + +.. _[9]: + +[9] https://trustedfirmware-a.readthedocs.io/en/latest/design/firmware-design.html#dynamic-configuration-during-cold-boot + +-------------- + +*Copyright (c) 2020-2023, Arm Limited and Contributors. All rights reserved.* diff --git a/docs/components/spd/index.rst b/docs/components/spd/index.rst new file mode 100644 index 0000000..6857806 --- /dev/null +++ b/docs/components/spd/index.rst @@ -0,0 +1,11 @@ +Secure Payload Dispatcher (SPD) +=============================== + +.. toctree:: + :maxdepth: 1 + :caption: Contents + + optee-dispatcher + tlk-dispatcher + trusty-dispatcher + pnc-dispatcher diff --git a/docs/components/spd/optee-dispatcher.rst b/docs/components/spd/optee-dispatcher.rst new file mode 100644 index 0000000..81476f1 --- /dev/null +++ b/docs/components/spd/optee-dispatcher.rst @@ -0,0 +1,31 @@ +OP-TEE Dispatcher +================= + +`OP-TEE OS`_ is a Trusted OS running as Secure EL1. + +To build and execute OP-TEE follow the instructions at +`OP-TEE build.git`_ + +There are two different modes for loading the OP-TEE OS. The default mode will +load it as the BL32 payload during boot, and is the recommended technique for +platforms to use. There is also another technique that will load OP-TEE OS after +boot via an SMC call by enabling the option for OPTEE_ALLOW_SMC_LOAD that was +specifically added for ChromeOS. Loading OP-TEE via an SMC call may be insecure +depending upon the platform configuration. If using that option, be sure to +understand the risks involved with allowing the Trusted OS to be loaded this +way. ChromeOS uses a boot flow where it verifies the signature of the firmware +before executing it, and then only if the signature is valid will the 'secrets' +used by the TEE become accessible. The firmware then verifies the signature of +the kernel using depthcharge, and the kernel verifies the rootfs using +dm-verity. The SMC call to load OP-TEE is then invoked immediately after the +kernel finishes loading and before any attack vectors can be opened up by +mounting writable filesystems or opening network/device connections. this +ensures the platform is 'closed' and running signed code through the point where +OP-TEE is loaded. + +-------------- + +*Copyright (c) 2014-2023, Arm Limited and Contributors. All rights reserved.* + +.. _OP-TEE OS: https://github.com/OP-TEE/build +.. _OP-TEE build.git: https://github.com/OP-TEE/build diff --git a/docs/components/spd/pnc-dispatcher.rst b/docs/components/spd/pnc-dispatcher.rst new file mode 100644 index 0000000..5be2fc7 --- /dev/null +++ b/docs/components/spd/pnc-dispatcher.rst @@ -0,0 +1,10 @@ +ProvenCore Dispatcher +===================== + +ProvenCore dispatcher (PnC-D) adds support for ProvenRun's ProvenCore micro-kernel +to work with Trusted Firmware-A (TF-A). + +ProvenCore is a secure OS developed by ProvenRun S.A.S. using deductive formal methods. + +Once a BL32 is ready, PnC-D can be included in the image by adding "SPD=pncd" +to the build command. diff --git a/docs/components/spd/tlk-dispatcher.rst b/docs/components/spd/tlk-dispatcher.rst new file mode 100644 index 0000000..a6c658c --- /dev/null +++ b/docs/components/spd/tlk-dispatcher.rst @@ -0,0 +1,76 @@ +Trusted Little Kernel (TLK) Dispatcher +====================================== + +TLK dispatcher (TLK-D) adds support for NVIDIA's Trusted Little Kernel (TLK) +to work with Trusted Firmware-A (TF-A). TLK-D can be compiled by including it +in the platform's makefile. TLK is primarily meant to work with Tegra SoCs, +so while TF-A only supports TLK on Tegra, the dispatcher code can only be +compiled for other platforms. + +In order to compile TLK-D, we need a BL32 image to be present. Since, TLKD +just needs to compile, any BL32 image would do. To use TLK as the BL32, please +refer to the "Build TLK" section. + +Once a BL32 is ready, TLKD can be included in the image by adding "SPD=tlkd" +to the build command. + +Trusted Little Kernel (TLK) +--------------------------- + +TLK is a Trusted OS running as Secure EL1. It is a Free Open Source Software +(FOSS) release of the NVIDIA® Trusted Little Kernel (TLK) technology, which +extends technology made available with the development of the Little Kernel (LK). +You can download the LK modular embedded preemptive kernel for use on Arm, +x86, and AVR32 systems from https://github.com/travisg/lk + +NVIDIA implemented its Trusted Little Kernel (TLK) technology, designed as a +free and open-source trusted execution environment (OTE). + +TLK features include: + +• Small, pre-emptive kernel +• Supports multi-threading, IPCs, and thread scheduling +• Added TrustZone features +• Added Secure Storage +• Under MIT/FreeBSD license + +NVIDIA extensions to Little Kernel (LK) include: + +• User mode +• Address-space separation for TAs +• TLK Client Application (CA) library +• TLK TA library +• Crypto library (encrypt/decrypt, key handling) via OpenSSL +• Linux kernel driver +• Cortex A9/A15 support +• Power Management +• TrustZone memory carve-out (reconfigurable) +• Page table management +• Debugging support over UART (USB planned) + +TLK is hosted by NVIDIA on http://nv-tegra.nvidia.com under the +3rdparty/ote\_partner/tlk.git repository. Detailed information about +TLK and OTE can be found in the Tegra\_BSP\_for\_Android\_TLK\_FOSS\_Reference.pdf +manual located under the "documentation" directory\_. + +Build TLK +--------- + +To build and execute TLK, follow the instructions from "Building a TLK Device" +section from Tegra\_BSP\_for\_Android\_TLK\_FOSS\_Reference.pdf manual. + +Input parameters to TLK +----------------------- + +TLK expects the TZDRAM size and a structure containing the boot arguments. BL2 +passes this information to the EL3 software as members of the bl32\_ep\_info +struct, where bl32\_ep\_info is part of bl31\_params\_t (passed by BL2 in X0) + +Example +~~~~~~~ + +:: + + bl32_ep_info->args.arg0 = TZDRAM size available for BL32 + bl32_ep_info->args.arg1 = unused (used only on Armv7-A) + bl32_ep_info->args.arg2 = pointer to boot args diff --git a/docs/components/spd/trusty-dispatcher.rst b/docs/components/spd/trusty-dispatcher.rst new file mode 100644 index 0000000..a3cb829 --- /dev/null +++ b/docs/components/spd/trusty-dispatcher.rst @@ -0,0 +1,32 @@ +Trusty Dispatcher +================= + +Trusty is a a set of software components, supporting a Trusted Execution +Environment (TEE) on mobile devices, published and maintained by Google. + +Detailed information and build instructions can be found on the Android +Open Source Project (AOSP) webpage for Trusty hosted at +https://source.android.com/security/trusty + +Boot parameters +--------------- + +Custom boot parameters can be passed to Trusty by providing a platform +specific function: + +.. code:: c + + void plat_trusty_set_boot_args(aapcs64_params_t *args) + +If this function is provided ``args->arg0`` must be set to the memory +size allocated to trusty. If the platform does not provide this +function, but defines ``TSP_SEC_MEM_SIZE``, a default implementation +will pass the memory size from ``TSP_SEC_MEM_SIZE``. ``args->arg1`` +can be set to a platform specific parameter block, and ``args->arg2`` +should then be set to the size of that block. + +Supported platforms +------------------- + +Out of all the platforms supported by Trusted Firmware-A, Trusty is only +verified and supported by NVIDIA's Tegra SoCs. diff --git a/docs/components/xlat-tables-lib-v2-design.rst b/docs/components/xlat-tables-lib-v2-design.rst new file mode 100644 index 0000000..cac32f5 --- /dev/null +++ b/docs/components/xlat-tables-lib-v2-design.rst @@ -0,0 +1,442 @@ +Translation (XLAT) Tables Library +================================= + +This document describes the design of the translation tables library (version 2) +used by Trusted Firmware-A (TF-A). This library provides APIs to create page +tables based on a description of the memory layout, as well as setting up system +registers related to the Memory Management Unit (MMU) and performing the +required Translation Lookaside Buffer (TLB) maintenance operations. + +More specifically, some use cases that this library aims to support are: + +#. Statically allocate translation tables and populate them (at run-time) based + upon a description of the memory layout. The memory layout is typically + provided by the platform port as a list of memory regions; + +#. Support for generating translation tables pertaining to a different + translation regime than the exception level the library code is executing at; + +#. Support for dynamic mapping and unmapping of regions, even while the MMU is + on. This can be used to temporarily map some memory regions and unmap them + later on when no longer needed; + +#. Support for non-identity virtual to physical mappings to compress the virtual + address space; + +#. Support for changing memory attributes of memory regions at run-time. + + +About version 1, version 2 and MPU libraries +-------------------------------------------- + +This document focuses on version 2 of the library, whose sources are available +in the ``lib/xlat_tables_v2`` directory. Version 1 of the library can still be +found in ``lib/xlat_tables`` directory but it is less flexible and doesn't +support dynamic mapping. ``lib/xlat_mpu``, which configures Arm's MPU +equivalently, is also addressed here. The ``lib/xlat_mpu`` is experimental, +meaning that its API may change. It currently strives for consistency and +code-reuse with xlat_tables_v2. Future versions may be more MPU-specific (e.g., +removing all mentions of virtual addresses). Although potential bug fixes will +be applied to all versions of the xlat_* libs, future feature enhancements will +focus on version 2 and might not be back-ported to version 1 and MPU versions. +Therefore, it is recommended to use version 2, especially for new platform +ports (unless the platform uses an MPU). + +However, please note that version 2 and the MPU version are still in active +development and is not considered stable yet. Hence, compatibility breaks might +be introduced. + +From this point onwards, this document will implicitly refer to version 2 of the +library, unless stated otherwise. + + +Design concepts and interfaces +------------------------------ + +This section presents some of the key concepts and data structures used in the +translation tables library. + +`mmap` regions +~~~~~~~~~~~~~~ + +An ``mmap_region`` is an abstract, concise way to represent a memory region to +map. It is one of the key interfaces to the library. It is identified by: + +- its physical base address; +- its virtual base address; +- its size; +- its attributes; +- its mapping granularity (optional). + +See the ``struct mmap_region`` type in ``xlat_tables_v2.h``. + +The user usually provides a list of such mmap regions to map and lets the +library transpose that in a set of translation tables. As a result, the library +might create new translation tables, update or split existing ones. + +The region attributes specify the type of memory (for example device or cached +normal memory) as well as the memory access permissions (read-only or +read-write, executable or not, secure or non-secure, and so on). In the case of +the EL1&0 translation regime, the attributes also specify whether the region is +a User region (EL0) or Privileged region (EL1). See the ``MT_xxx`` definitions +in ``xlat_tables_v2.h``. Note that for the EL1&0 translation regime the Execute +Never attribute is set simultaneously for both EL1 and EL0. + +The granularity controls the translation table level to go down to when mapping +the region. For example, assuming the MMU has been configured to use a 4KB +granule size, the library might map a 2MB memory region using either of the two +following options: + +- using a single level-2 translation table entry; +- using a level-2 intermediate entry to a level-3 translation table (which + contains 512 entries, each mapping 4KB). + +The first solution potentially requires less translation tables, hence +potentially less memory. However, if part of this 2MB region is later remapped +with different memory attributes, the library might need to split the existing +page tables to refine the mappings. If a single level-2 entry has been used +here, a level-3 table will need to be allocated on the fly and the level-2 +modified to point to this new level-3 table. This has a performance cost at +run-time. + +If the user knows upfront that such a remapping operation is likely to happen +then they might enforce a 4KB mapping granularity for this 2MB region from the +beginning; remapping some of these 4KB pages on the fly then becomes a +lightweight operation. + +The region's granularity is an optional field; if it is not specified the +library will choose the mapping granularity for this region as it sees fit (more +details can be found in `The memory mapping algorithm`_ section below). + +The MPU library also uses ``struct mmap_region`` to specify translations, but +the MPU's translations are limited to specification of valid addresses and +access permissions. If the requested virtual and physical addresses mismatch +the system will panic. Being register-based for deterministic memory-reference +timing, the MPU hardware does not involve memory-resident translation tables. + +Currently, the MPU library is also limited to MPU translation at EL2 with no +MMU translation at other ELs. These limitations, however, are expected to be +overcome in future library versions. + +Translation Context +~~~~~~~~~~~~~~~~~~~ + +The library can create or modify translation tables pertaining to a different +translation regime than the exception level the library code is executing at. +For example, the library might be used by EL3 software (for instance BL31) to +create translation tables pertaining to the S-EL1&0 translation regime. + +This flexibility comes from the use of *translation contexts*. A *translation +context* constitutes the superset of information used by the library to track +the status of a set of translation tables for a given translation regime. + +The library internally allocates a default translation context, which pertains +to the translation regime of the current exception level. Additional contexts +may be explicitly allocated and initialized using the +``REGISTER_XLAT_CONTEXT()`` macro. Separate APIs are provided to act either on +the default translation context or on an alternative one. + +To register a translation context, the user must provide the library with the +following information: + +* A name. + + The resulting translation context variable will be called after this name, to + which ``_xlat_ctx`` is appended. For example, if the macro name parameter is + ``foo``, the context variable name will be ``foo_xlat_ctx``. + +* The maximum number of `mmap` regions to map. + + Should account for both static and dynamic regions, if applicable. + +* The number of sub-translation tables to allocate. + + Number of translation tables to statically allocate for this context, + excluding the initial lookup level translation table, which is always + allocated. For example, if the initial lookup level is 1, this parameter would + specify the number of level-2 and level-3 translation tables to pre-allocate + for this context. + +* The size of the virtual address space. + + Size in bytes of the virtual address space to map using this context. This + will incidentally determine the number of entries in the initial lookup level + translation table : the library will allocate as many entries as is required + to map the entire virtual address space. + +* The size of the physical address space. + + Size in bytes of the physical address space to map using this context. + +The default translation context is internally initialized using information +coming (for the most part) from platform-specific defines: + +- name: hard-coded to ``tf`` ; hence the name of the default context variable is + ``tf_xlat_ctx``; +- number of `mmap` regions: ``MAX_MMAP_REGIONS``; +- number of sub-translation tables: ``MAX_XLAT_TABLES``; +- size of the virtual address space: ``PLAT_VIRT_ADDR_SPACE_SIZE``; +- size of the physical address space: ``PLAT_PHY_ADDR_SPACE_SIZE``. + +Please refer to the :ref:`Porting Guide` for more details about these macros. + + +Static and dynamic memory regions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The library optionally supports dynamic memory mapping. This feature may be +enabled using the ``PLAT_XLAT_TABLES_DYNAMIC`` platform build flag. + +When dynamic memory mapping is enabled, the library categorises mmap regions as +*static* or *dynamic*. + +- *Static regions* are fixed for the lifetime of the system. They can only be + added early on, before the translation tables are created and populated. They + cannot be removed afterwards. + +- *Dynamic regions* can be added or removed any time. + +When the dynamic memory mapping feature is disabled, only static regions exist. + +The dynamic memory mapping feature may be used to map and unmap transient memory +areas. This is useful when the user needs to access some memory for a fixed +period of time, after which the memory may be discarded and reclaimed. For +example, a memory region that is only required at boot time while the system is +initializing, or to temporarily share a memory buffer between the normal world +and trusted world. Note that it is up to the caller to ensure that these regions +are not accessed concurrently while the regions are being added or removed. + +Although this feature provides some level of dynamic memory allocation, this +does not allow dynamically allocating an arbitrary amount of memory at an +arbitrary memory location. The user is still required to declare at compile-time +the limits of these allocations ; the library will deny any mapping request that +does not fit within this pre-allocated pool of memory. + + +Library APIs +------------ + +The external APIs exposed by this library are declared and documented in the +``xlat_tables_v2.h`` header file. This should be the reference point for +getting information about the usage of the different APIs this library +provides. This section just provides some extra details and clarifications. + +Although the ``mmap_region`` structure is a publicly visible type, it is not +recommended to populate these structures by hand. Instead, wherever APIs expect +function arguments of type ``mmap_region_t``, these should be constructed using +the ``MAP_REGION*()`` family of helper macros. This is to limit the risk of +compatibility breaks, should the ``mmap_region`` structure type evolve in the +future. + +The ``MAP_REGION()`` and ``MAP_REGION_FLAT()`` macros do not allow specifying a +mapping granularity, which leaves the library implementation free to choose +it. However, in cases where a specific granularity is required, the +``MAP_REGION2()`` macro might be used instead. Using ``MAP_REGION_FLAT()`` only +to define regions for the MPU library is strongly recommended. + +As explained earlier in this document, when the dynamic mapping feature is +disabled, there is no notion of dynamic regions. Conceptually, there are only +static regions. For this reason (and to retain backward compatibility with the +version 1 of the library), the APIs that map static regions do not embed the +word *static* in their functions names (for example ``mmap_add_region()``), in +contrast with the dynamic regions APIs (for example +``mmap_add_dynamic_region()``). + +Although the definition of static and dynamic regions is not based on the state +of the MMU, the two are still related in some way. Static regions can only be +added before ``init_xlat_tables()`` is called and ``init_xlat_tables()`` must be +called while the MMU is still off. As a result, static regions cannot be added +once the MMU has been enabled. Dynamic regions can be added with the MMU on or +off. In practice, the usual call flow would look like this: + +#. The MMU is initially off. + +#. Add some static regions, add some dynamic regions. + +#. Initialize translation tables based on the list of mmap regions (using one of + the ``init_xlat_tables*()`` APIs). + +#. At this point, it is no longer possible to add static regions. Dynamic + regions can still be added or removed. + +#. Enable the MMU. + +#. Dynamic regions can continue to be added or removed. + +Because static regions are added early on at boot time and are all in the +control of the platform initialization code, the ``mmap_add*()`` family of APIs +are not expected to fail. They do not return any error code. + +Nonetheless, these APIs will check upfront whether the region can be +successfully added before updating the translation context structure. If the +library detects that there is insufficient memory to meet the request, or that +the new region will overlap another one in an invalid way, or if any other +unexpected error is encountered, they will print an error message on the UART. +Additionally, when asserts are enabled (typically in debug builds), an assertion +will be triggered. Otherwise, the function call will just return straight away, +without adding the offending memory region. + + +Library limitations +------------------- + +Dynamic regions are not allowed to overlap each other. Static regions are +allowed to overlap as long as one of them is fully contained inside the other +one. This is allowed for backwards compatibility with the previous behaviour in +the version 1 of the library. + + +Implementation details +---------------------- + +Code structure +~~~~~~~~~~~~~~ + +The library is divided into 4 modules: + +- **Core module** + + Provides the main functionality of the library, such as the initialization of + translation tables contexts and mapping/unmapping memory regions. This module + provides functions such as ``mmap_add_region_ctx`` that let the caller specify + the translation tables context affected by them. + + See ``xlat_tables_core.c``. + +- **Active context module** + + Instantiates the context that is used by the current BL image and provides + helpers to manipulate it, abstracting it from the rest of the code. + This module provides functions such as ``mmap_add_region``, that directly + affect the BL image using them. + + See ``xlat_tables_context.c``. + +- **Utilities module** + + Provides additional functionality like debug print of the current state of the + translation tables and helpers to query memory attributes and to modify them. + + See ``xlat_tables_utils.c``. + +- **Architectural module** + + Provides functions that are dependent on the current execution state + (AArch32/AArch64), such as the functions used for TLB invalidation, setup the + MMU, or calculate the Physical Address Space size. They do not need a + translation context to work on. + + See ``aarch32/xlat_tables_arch.c`` and ``aarch64/xlat_tables_arch.c``. + +From mmap regions to translation tables +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A translation context contains a list of ``mmap_region_t``, which holds the +information of all the regions that are mapped at any given time. Whenever there +is a request to map (resp. unmap) a memory region, it is added to (resp. removed +from) the ``mmap_region_t`` list. + +The mmap regions list is a conceptual way to represent the memory layout. At +some point, the library has to convert this information into actual translation +tables to program into the MMU. + +Before the ``init_xlat_tables()`` API is called, the library only acts on the +mmap regions list. Adding a static or dynamic region at this point through one +of the ``mmap_add*()`` APIs does not affect the translation tables in any way, +they only get registered in the internal mmap region list. It is only when the +user calls the ``init_xlat_tables()`` that the translation tables are populated +in memory based on the list of mmap regions registered so far. This is an +optimization that allows creation of the initial set of translation tables in +one go, rather than having to edit them every time while the MMU is disabled. + +After the ``init_xlat_tables()`` API has been called, only dynamic regions can +be added. Changes to the translation tables (as well as the mmap regions list) +will take effect immediately. + +The memory mapping algorithm +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The mapping function is implemented as a recursive algorithm. It is however +bound by the level of depth of the translation tables (the Armv8-A architecture +allows up to 4 lookup levels). + +By default [#granularity]_, the algorithm will attempt to minimize the +number of translation tables created to satisfy the user's request. It will +favour mapping a region using the biggest possible blocks, only creating a +sub-table if it is strictly necessary. This is to reduce the memory footprint of +the firmware. + +The most common reason for needing a sub-table is when a specific mapping +requires a finer granularity. Misaligned regions also require a finer +granularity than what the user may had originally expected, using a lot more +memory than expected. The reason is that all levels of translation are +restricted to address translations of the same granularity as the size of the +blocks of that level. For example, for a 4 KiB page size, a level 2 block entry +can only translate up to a granularity of 2 MiB. If the Physical Address is not +aligned to 2 MiB then additional level 3 tables are also needed. + +Note that not every translation level allows any type of descriptor. Depending +on the page size, levels 0 and 1 of translation may only allow table +descriptors. If a block entry could be able to describe a translation, but that +level does not allow block descriptors, a table descriptor will have to be used +instead, as well as additional tables at the next level. + +|Alignment Example| + +The mmap regions are sorted in a way that simplifies the code that maps +them. Even though this ordering is only strictly needed for overlapping static +regions, it must also be applied for dynamic regions to maintain a consistent +order of all regions at all times. As each new region is mapped, existing +entries in the translation tables are checked to ensure consistency. Please +refer to the comments in the source code of the core module for more details +about the sorting algorithm in use. + +This mapping algorithm does not apply to the MPU library, since the MPU hardware +directly maps regions by "base" and "limit" (bottom and top) addresses. + +TLB maintenance operations +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The library takes care of performing TLB maintenance operations when required. +For example, when the user requests removing a dynamic region, the library +invalidates all TLB entries associated to that region to ensure that these +changes are visible to subsequent execution, including speculative execution, +that uses the changed translation table entries. + +A counter-example is the initialization of translation tables. In this case, +explicit TLB maintenance is not required. The Armv8-A architecture guarantees +that all TLBs are disabled from reset and their contents have no effect on +address translation at reset [#tlb-reset-ref]_. Therefore, the TLBs invalidation +is deferred to the ``enable_mmu*()`` family of functions, just before the MMU is +turned on. + +Regarding enabling and disabling memory management, for the MPU library, to +reduce confusion, calls to enable or disable the MPU use ``mpu`` in their names +in place of ``mmu``. For example, the ``enable_mmu_el2()`` call is changed to +``enable_mpu_el2()``. + +TLB invalidation is not required when adding dynamic regions either. Dynamic +regions are not allowed to overlap existing memory region. Therefore, if the +dynamic mapping request is deemed legitimate, it automatically concerns memory +that was not mapped in this translation regime and the library will have +initialized its corresponding translation table entry to an invalid +descriptor. Given that the TLBs are not architecturally permitted to hold any +invalid translation table entry [#tlb-no-invalid-entry]_, this means that this +mapping cannot be cached in the TLBs. + +.. rubric:: Footnotes + +.. [#granularity] That is, when mmap regions do not enforce their mapping + granularity. + +.. [#tlb-reset-ref] See section D4.9 ``Translation Lookaside Buffers (TLBs)``, + subsection ``TLB behavior at reset`` in Armv8-A, rev C.a. + +.. [#tlb-no-invalid-entry] See section D4.10.1 ``General TLB maintenance + requirements`` in Armv8-A, rev C.a. + +-------------- + +*Copyright (c) 2017-2021, Arm Limited and Contributors. All rights reserved.* + +.. |Alignment Example| image:: ../resources/diagrams/xlat_align.png |