diff options
Diffstat (limited to 'src/boot/efi/linux.c')
| -rw-r--r-- | src/boot/efi/linux.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/src/boot/efi/linux.c b/src/boot/efi/linux.c new file mode 100644 index 0000000..48801f9 --- /dev/null +++ b/src/boot/efi/linux.c @@ -0,0 +1,155 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +/* + * Generic Linux boot protocol using the EFI/PE entry point of the kernel. Passes + * initrd with the LINUX_INITRD_MEDIA_GUID DevicePath and cmdline with + * EFI LoadedImageProtocol. + * + * This method works for Linux 5.8 and newer on ARM/Aarch64, x86/x68_64 and RISC-V. + */ + +#include <efi.h> +#include <efilib.h> + +#include "initrd.h" +#include "linux.h" +#include "pe.h" +#include "secure-boot.h" +#include "util.h" + +#define STUB_PAYLOAD_GUID \ + { 0x55c5d1f8, 0x04cd, 0x46b5, { 0x8a, 0x20, 0xe5, 0x6c, 0xbb, 0x30, 0x52, 0xd0 } } + +typedef struct { + const void *addr; + size_t len; + const EFI_DEVICE_PATH *device_path; +} ValidationContext; + +static bool validate_payload( + const void *ctx, const EFI_DEVICE_PATH *device_path, const void *file_buffer, size_t file_size) { + + const ValidationContext *payload = ASSERT_PTR(ctx); + + if (device_path != payload->device_path) + return false; + + /* Security arch (1) protocol does not provide a file buffer. Instead we are supposed to fetch the payload + * ourselves, which is not needed as we already have everything in memory and the device paths match. */ + if (file_buffer && (file_buffer != payload->addr || file_size != payload->len)) + return false; + + return true; +} + +static EFI_STATUS load_image(EFI_HANDLE parent, const void *source, size_t len, EFI_HANDLE *ret_image) { + assert(parent); + assert(source); + assert(ret_image); + + /* We could pass a NULL device path, but it's nicer to provide something and it allows us to identify + * the loaded image from within the security hooks. */ + struct { + VENDOR_DEVICE_PATH payload; + EFI_DEVICE_PATH end; + } _packed_ payload_device_path = { + .payload = { + .Header = { + .Type = MEDIA_DEVICE_PATH, + .SubType = MEDIA_VENDOR_DP, + .Length = { sizeof(payload_device_path.payload), 0 }, + }, + .Guid = STUB_PAYLOAD_GUID, + }, + .end = { + .Type = END_DEVICE_PATH_TYPE, + .SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE, + .Length = { sizeof(payload_device_path.end), 0 }, + }, + }; + + /* We want to support unsigned kernel images as payload, which is safe to do under secure boot + * because it is embedded in this stub loader (and since it is already running it must be trusted). */ + install_security_override( + validate_payload, + &(ValidationContext) { + .addr = source, + .len = len, + .device_path = &payload_device_path.payload.Header, + }); + + EFI_STATUS ret = BS->LoadImage( + /*BootPolicy=*/false, + parent, + &payload_device_path.payload.Header, + (void *) source, + len, + ret_image); + + uninstall_security_override(); + + return ret; +} + +EFI_STATUS linux_exec( + EFI_HANDLE parent, + const char16_t *cmdline, + const void *linux_buffer, + size_t linux_length, + const void *initrd_buffer, + size_t initrd_length) { + + uint32_t compat_address; + EFI_STATUS err; + + assert(parent); + assert(linux_buffer && linux_length > 0); + assert(initrd_buffer || initrd_length == 0); + + err = pe_kernel_info(linux_buffer, &compat_address); +#if defined(__i386__) || defined(__x86_64__) + if (err == EFI_UNSUPPORTED) + /* Kernel is too old to support LINUX_INITRD_MEDIA_GUID, try the deprecated EFI handover + * protocol. */ + return linux_exec_efi_handover( + parent, + cmdline, + linux_buffer, + linux_length, + initrd_buffer, + initrd_length); +#endif + if (err != EFI_SUCCESS) + return log_error_status_stall(err, u"Bad kernel image: %r", err); + + _cleanup_(unload_imagep) EFI_HANDLE kernel_image = NULL; + err = load_image(parent, linux_buffer, linux_length, &kernel_image); + if (err != EFI_SUCCESS) + return log_error_status_stall(err, u"Error loading kernel image: %r", err); + + EFI_LOADED_IMAGE_PROTOCOL *loaded_image; + err = BS->HandleProtocol(kernel_image, &LoadedImageProtocol, (void **) &loaded_image); + if (err != EFI_SUCCESS) + return log_error_status_stall(err, u"Error getting kernel loaded image protocol: %r", err); + + if (cmdline) { + loaded_image->LoadOptions = (void *) cmdline; + loaded_image->LoadOptionsSize = strsize16(loaded_image->LoadOptions); + } + + _cleanup_(cleanup_initrd) EFI_HANDLE initrd_handle = NULL; + err = initrd_register(initrd_buffer, initrd_length, &initrd_handle); + if (err != EFI_SUCCESS) + return log_error_status_stall(err, u"Error registering initrd: %r", err); + + err = BS->StartImage(kernel_image, NULL, NULL); + + /* Try calling the kernel compat entry point if one exists. */ + if (err == EFI_UNSUPPORTED && compat_address > 0) { + EFI_IMAGE_ENTRY_POINT compat_entry = + (EFI_IMAGE_ENTRY_POINT) ((uint8_t *) loaded_image->ImageBase + compat_address); + err = compat_entry(kernel_image, ST); + } + + return log_error_status_stall(err, u"Error starting kernel image: %r", err); +} |