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path: root/drivers/firmware/efi/libstub/efi-stub-helper.c
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Diffstat (limited to 'drivers/firmware/efi/libstub/efi-stub-helper.c')
-rw-r--r--drivers/firmware/efi/libstub/efi-stub-helper.c722
1 files changed, 722 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
new file mode 100644
index 0000000000..bfa30625f5
--- /dev/null
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -0,0 +1,722 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helper functions used by the EFI stub on multiple
+ * architectures. This should be #included by the EFI stub
+ * implementation files.
+ *
+ * Copyright 2011 Intel Corporation; author Matt Fleming
+ */
+
+#include <linux/stdarg.h>
+
+#include <linux/efi.h>
+#include <linux/kernel.h>
+#include <asm/efi.h>
+#include <asm/setup.h>
+
+#include "efistub.h"
+
+bool efi_nochunk;
+bool efi_nokaslr = !IS_ENABLED(CONFIG_RANDOMIZE_BASE);
+bool efi_novamap;
+
+static bool efi_noinitrd;
+static bool efi_nosoftreserve;
+static bool efi_disable_pci_dma = IS_ENABLED(CONFIG_EFI_DISABLE_PCI_DMA);
+
+bool __pure __efi_soft_reserve_enabled(void)
+{
+ return !efi_nosoftreserve;
+}
+
+/**
+ * efi_parse_options() - Parse EFI command line options
+ * @cmdline: kernel command line
+ *
+ * Parse the ASCII string @cmdline for EFI options, denoted by the efi=
+ * option, e.g. efi=nochunk.
+ *
+ * It should be noted that efi= is parsed in two very different
+ * environments, first in the early boot environment of the EFI boot
+ * stub, and subsequently during the kernel boot.
+ *
+ * Return: status code
+ */
+efi_status_t efi_parse_options(char const *cmdline)
+{
+ size_t len;
+ efi_status_t status;
+ char *str, *buf;
+
+ if (!cmdline)
+ return EFI_SUCCESS;
+
+ len = strnlen(cmdline, COMMAND_LINE_SIZE - 1) + 1;
+ status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, len, (void **)&buf);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ memcpy(buf, cmdline, len - 1);
+ buf[len - 1] = '\0';
+ str = skip_spaces(buf);
+
+ while (*str) {
+ char *param, *val;
+
+ str = next_arg(str, &param, &val);
+ if (!val && !strcmp(param, "--"))
+ break;
+
+ if (!strcmp(param, "nokaslr")) {
+ efi_nokaslr = true;
+ } else if (!strcmp(param, "quiet")) {
+ efi_loglevel = CONSOLE_LOGLEVEL_QUIET;
+ } else if (!strcmp(param, "noinitrd")) {
+ efi_noinitrd = true;
+ } else if (IS_ENABLED(CONFIG_X86_64) && !strcmp(param, "no5lvl")) {
+ efi_no5lvl = true;
+ } else if (!strcmp(param, "efi") && val) {
+ efi_nochunk = parse_option_str(val, "nochunk");
+ efi_novamap |= parse_option_str(val, "novamap");
+
+ efi_nosoftreserve = IS_ENABLED(CONFIG_EFI_SOFT_RESERVE) &&
+ parse_option_str(val, "nosoftreserve");
+
+ if (parse_option_str(val, "disable_early_pci_dma"))
+ efi_disable_pci_dma = true;
+ if (parse_option_str(val, "no_disable_early_pci_dma"))
+ efi_disable_pci_dma = false;
+ if (parse_option_str(val, "debug"))
+ efi_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+ } else if (!strcmp(param, "video") &&
+ val && strstarts(val, "efifb:")) {
+ efi_parse_option_graphics(val + strlen("efifb:"));
+ }
+ }
+ efi_bs_call(free_pool, buf);
+ return EFI_SUCCESS;
+}
+
+/*
+ * The EFI_LOAD_OPTION descriptor has the following layout:
+ * u32 Attributes;
+ * u16 FilePathListLength;
+ * u16 Description[];
+ * efi_device_path_protocol_t FilePathList[];
+ * u8 OptionalData[];
+ *
+ * This function validates and unpacks the variable-size data fields.
+ */
+static
+bool efi_load_option_unpack(efi_load_option_unpacked_t *dest,
+ const efi_load_option_t *src, size_t size)
+{
+ const void *pos;
+ u16 c;
+ efi_device_path_protocol_t header;
+ const efi_char16_t *description;
+ const efi_device_path_protocol_t *file_path_list;
+
+ if (size < offsetof(efi_load_option_t, variable_data))
+ return false;
+ pos = src->variable_data;
+ size -= offsetof(efi_load_option_t, variable_data);
+
+ if ((src->attributes & ~EFI_LOAD_OPTION_MASK) != 0)
+ return false;
+
+ /* Scan description. */
+ description = pos;
+ do {
+ if (size < sizeof(c))
+ return false;
+ c = *(const u16 *)pos;
+ pos += sizeof(c);
+ size -= sizeof(c);
+ } while (c != L'\0');
+
+ /* Scan file_path_list. */
+ file_path_list = pos;
+ do {
+ if (size < sizeof(header))
+ return false;
+ header = *(const efi_device_path_protocol_t *)pos;
+ if (header.length < sizeof(header))
+ return false;
+ if (size < header.length)
+ return false;
+ pos += header.length;
+ size -= header.length;
+ } while ((header.type != EFI_DEV_END_PATH && header.type != EFI_DEV_END_PATH2) ||
+ (header.sub_type != EFI_DEV_END_ENTIRE));
+ if (pos != (const void *)file_path_list + src->file_path_list_length)
+ return false;
+
+ dest->attributes = src->attributes;
+ dest->file_path_list_length = src->file_path_list_length;
+ dest->description = description;
+ dest->file_path_list = file_path_list;
+ dest->optional_data_size = size;
+ dest->optional_data = size ? pos : NULL;
+
+ return true;
+}
+
+/*
+ * At least some versions of Dell firmware pass the entire contents of the
+ * Boot#### variable, i.e. the EFI_LOAD_OPTION descriptor, rather than just the
+ * OptionalData field.
+ *
+ * Detect this case and extract OptionalData.
+ */
+void efi_apply_loadoptions_quirk(const void **load_options, u32 *load_options_size)
+{
+ const efi_load_option_t *load_option = *load_options;
+ efi_load_option_unpacked_t load_option_unpacked;
+
+ if (!IS_ENABLED(CONFIG_X86))
+ return;
+ if (!load_option)
+ return;
+ if (*load_options_size < sizeof(*load_option))
+ return;
+ if ((load_option->attributes & ~EFI_LOAD_OPTION_BOOT_MASK) != 0)
+ return;
+
+ if (!efi_load_option_unpack(&load_option_unpacked, load_option, *load_options_size))
+ return;
+
+ efi_warn_once(FW_BUG "LoadOptions is an EFI_LOAD_OPTION descriptor\n");
+ efi_warn_once(FW_BUG "Using OptionalData as a workaround\n");
+
+ *load_options = load_option_unpacked.optional_data;
+ *load_options_size = load_option_unpacked.optional_data_size;
+}
+
+enum efistub_event {
+ EFISTUB_EVT_INITRD,
+ EFISTUB_EVT_LOAD_OPTIONS,
+ EFISTUB_EVT_COUNT,
+};
+
+#define STR_WITH_SIZE(s) sizeof(s), s
+
+static const struct {
+ u32 pcr_index;
+ u32 event_id;
+ u32 event_data_len;
+ u8 event_data[52];
+} events[] = {
+ [EFISTUB_EVT_INITRD] = {
+ 9,
+ INITRD_EVENT_TAG_ID,
+ STR_WITH_SIZE("Linux initrd")
+ },
+ [EFISTUB_EVT_LOAD_OPTIONS] = {
+ 9,
+ LOAD_OPTIONS_EVENT_TAG_ID,
+ STR_WITH_SIZE("LOADED_IMAGE::LoadOptions")
+ },
+};
+
+static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
+ unsigned long load_size,
+ enum efistub_event event)
+{
+ efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
+ efi_tcg2_protocol_t *tcg2 = NULL;
+ efi_status_t status;
+
+ efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);
+ if (tcg2) {
+ struct efi_measured_event {
+ efi_tcg2_event_t event_data;
+ efi_tcg2_tagged_event_t tagged_event;
+ u8 tagged_event_data[];
+ } *evt;
+ int size = sizeof(*evt) + events[event].event_data_len;
+
+ status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size,
+ (void **)&evt);
+ if (status != EFI_SUCCESS)
+ goto fail;
+
+ evt->event_data = (struct efi_tcg2_event){
+ .event_size = size,
+ .event_header.header_size = sizeof(evt->event_data.event_header),
+ .event_header.header_version = EFI_TCG2_EVENT_HEADER_VERSION,
+ .event_header.pcr_index = events[event].pcr_index,
+ .event_header.event_type = EV_EVENT_TAG,
+ };
+
+ evt->tagged_event = (struct efi_tcg2_tagged_event){
+ .tagged_event_id = events[event].event_id,
+ .tagged_event_data_size = events[event].event_data_len,
+ };
+
+ memcpy(evt->tagged_event_data, events[event].event_data,
+ events[event].event_data_len);
+
+ status = efi_call_proto(tcg2, hash_log_extend_event, 0,
+ load_addr, load_size, &evt->event_data);
+ efi_bs_call(free_pool, evt);
+
+ if (status != EFI_SUCCESS)
+ goto fail;
+ return EFI_SUCCESS;
+ }
+
+ return EFI_UNSUPPORTED;
+fail:
+ efi_warn("Failed to measure data for event %d: 0x%lx\n", event, status);
+ return status;
+}
+
+/*
+ * Convert the unicode UEFI command line to ASCII to pass to kernel.
+ * Size of memory allocated return in *cmd_line_len.
+ * Returns NULL on error.
+ */
+char *efi_convert_cmdline(efi_loaded_image_t *image, int *cmd_line_len)
+{
+ const efi_char16_t *options = efi_table_attr(image, load_options);
+ u32 options_size = efi_table_attr(image, load_options_size);
+ int options_bytes = 0, safe_options_bytes = 0; /* UTF-8 bytes */
+ unsigned long cmdline_addr = 0;
+ const efi_char16_t *s2;
+ bool in_quote = false;
+ efi_status_t status;
+ u32 options_chars;
+
+ if (options_size > 0)
+ efi_measure_tagged_event((unsigned long)options, options_size,
+ EFISTUB_EVT_LOAD_OPTIONS);
+
+ efi_apply_loadoptions_quirk((const void **)&options, &options_size);
+ options_chars = options_size / sizeof(efi_char16_t);
+
+ if (options) {
+ s2 = options;
+ while (options_bytes < COMMAND_LINE_SIZE && options_chars--) {
+ efi_char16_t c = *s2++;
+
+ if (c < 0x80) {
+ if (c == L'\0' || c == L'\n')
+ break;
+ if (c == L'"')
+ in_quote = !in_quote;
+ else if (!in_quote && isspace((char)c))
+ safe_options_bytes = options_bytes;
+
+ options_bytes++;
+ continue;
+ }
+
+ /*
+ * Get the number of UTF-8 bytes corresponding to a
+ * UTF-16 character.
+ * The first part handles everything in the BMP.
+ */
+ options_bytes += 2 + (c >= 0x800);
+ /*
+ * Add one more byte for valid surrogate pairs. Invalid
+ * surrogates will be replaced with 0xfffd and take up
+ * only 3 bytes.
+ */
+ if ((c & 0xfc00) == 0xd800) {
+ /*
+ * If the very last word is a high surrogate,
+ * we must ignore it since we can't access the
+ * low surrogate.
+ */
+ if (!options_chars) {
+ options_bytes -= 3;
+ } else if ((*s2 & 0xfc00) == 0xdc00) {
+ options_bytes++;
+ options_chars--;
+ s2++;
+ }
+ }
+ }
+ if (options_bytes >= COMMAND_LINE_SIZE) {
+ options_bytes = safe_options_bytes;
+ efi_err("Command line is too long: truncated to %d bytes\n",
+ options_bytes);
+ }
+ }
+
+ options_bytes++; /* NUL termination */
+
+ status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, options_bytes,
+ (void **)&cmdline_addr);
+ if (status != EFI_SUCCESS)
+ return NULL;
+
+ snprintf((char *)cmdline_addr, options_bytes, "%.*ls",
+ options_bytes - 1, options);
+
+ *cmd_line_len = options_bytes;
+ return (char *)cmdline_addr;
+}
+
+/**
+ * efi_exit_boot_services() - Exit boot services
+ * @handle: handle of the exiting image
+ * @priv: argument to be passed to @priv_func
+ * @priv_func: function to process the memory map before exiting boot services
+ *
+ * Handle calling ExitBootServices according to the requirements set out by the
+ * spec. Obtains the current memory map, and returns that info after calling
+ * ExitBootServices. The client must specify a function to perform any
+ * processing of the memory map data prior to ExitBootServices. A client
+ * specific structure may be passed to the function via priv. The client
+ * function may be called multiple times.
+ *
+ * Return: status code
+ */
+efi_status_t efi_exit_boot_services(void *handle, void *priv,
+ efi_exit_boot_map_processing priv_func)
+{
+ struct efi_boot_memmap *map;
+ efi_status_t status;
+
+ if (efi_disable_pci_dma)
+ efi_pci_disable_bridge_busmaster();
+
+ status = efi_get_memory_map(&map, true);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = priv_func(map, priv);
+ if (status != EFI_SUCCESS) {
+ efi_bs_call(free_pool, map);
+ return status;
+ }
+
+ status = efi_bs_call(exit_boot_services, handle, map->map_key);
+
+ if (status == EFI_INVALID_PARAMETER) {
+ /*
+ * The memory map changed between efi_get_memory_map() and
+ * exit_boot_services(). Per the UEFI Spec v2.6, Section 6.4:
+ * EFI_BOOT_SERVICES.ExitBootServices we need to get the
+ * updated map, and try again. The spec implies one retry
+ * should be sufficent, which is confirmed against the EDK2
+ * implementation. Per the spec, we can only invoke
+ * get_memory_map() and exit_boot_services() - we cannot alloc
+ * so efi_get_memory_map() cannot be used, and we must reuse
+ * the buffer. For all practical purposes, the headroom in the
+ * buffer should account for any changes in the map so the call
+ * to get_memory_map() is expected to succeed here.
+ */
+ map->map_size = map->buff_size;
+ status = efi_bs_call(get_memory_map,
+ &map->map_size,
+ &map->map,
+ &map->map_key,
+ &map->desc_size,
+ &map->desc_ver);
+
+ /* exit_boot_services() was called, thus cannot free */
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = priv_func(map, priv);
+ /* exit_boot_services() was called, thus cannot free */
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = efi_bs_call(exit_boot_services, handle, map->map_key);
+ }
+
+ return status;
+}
+
+/**
+ * get_efi_config_table() - retrieve UEFI configuration table
+ * @guid: GUID of the configuration table to be retrieved
+ * Return: pointer to the configuration table or NULL
+ */
+void *get_efi_config_table(efi_guid_t guid)
+{
+ unsigned long tables = efi_table_attr(efi_system_table, tables);
+ int nr_tables = efi_table_attr(efi_system_table, nr_tables);
+ int i;
+
+ for (i = 0; i < nr_tables; i++) {
+ efi_config_table_t *t = (void *)tables;
+
+ if (efi_guidcmp(t->guid, guid) == 0)
+ return efi_table_attr(t, table);
+
+ tables += efi_is_native() ? sizeof(efi_config_table_t)
+ : sizeof(efi_config_table_32_t);
+ }
+ return NULL;
+}
+
+/*
+ * The LINUX_EFI_INITRD_MEDIA_GUID vendor media device path below provides a way
+ * for the firmware or bootloader to expose the initrd data directly to the stub
+ * via the trivial LoadFile2 protocol, which is defined in the UEFI spec, and is
+ * very easy to implement. It is a simple Linux initrd specific conduit between
+ * kernel and firmware, allowing us to put the EFI stub (being part of the
+ * kernel) in charge of where and when to load the initrd, while leaving it up
+ * to the firmware to decide whether it needs to expose its filesystem hierarchy
+ * via EFI protocols.
+ */
+static const struct {
+ struct efi_vendor_dev_path vendor;
+ struct efi_generic_dev_path end;
+} __packed initrd_dev_path = {
+ {
+ {
+ EFI_DEV_MEDIA,
+ EFI_DEV_MEDIA_VENDOR,
+ sizeof(struct efi_vendor_dev_path),
+ },
+ LINUX_EFI_INITRD_MEDIA_GUID
+ }, {
+ EFI_DEV_END_PATH,
+ EFI_DEV_END_ENTIRE,
+ sizeof(struct efi_generic_dev_path)
+ }
+};
+
+/**
+ * efi_load_initrd_dev_path() - load the initrd from the Linux initrd device path
+ * @initrd: pointer of struct to store the address where the initrd was loaded
+ * and the size of the loaded initrd
+ * @max: upper limit for the initrd memory allocation
+ *
+ * Return:
+ * * %EFI_SUCCESS if the initrd was loaded successfully, in which
+ * case @load_addr and @load_size are assigned accordingly
+ * * %EFI_NOT_FOUND if no LoadFile2 protocol exists on the initrd device path
+ * * %EFI_OUT_OF_RESOURCES if memory allocation failed
+ * * %EFI_LOAD_ERROR in all other cases
+ */
+static
+efi_status_t efi_load_initrd_dev_path(struct linux_efi_initrd *initrd,
+ unsigned long max)
+{
+ efi_guid_t lf2_proto_guid = EFI_LOAD_FILE2_PROTOCOL_GUID;
+ efi_device_path_protocol_t *dp;
+ efi_load_file2_protocol_t *lf2;
+ efi_handle_t handle;
+ efi_status_t status;
+
+ dp = (efi_device_path_protocol_t *)&initrd_dev_path;
+ status = efi_bs_call(locate_device_path, &lf2_proto_guid, &dp, &handle);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = efi_bs_call(handle_protocol, handle, &lf2_proto_guid,
+ (void **)&lf2);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ initrd->size = 0;
+ status = efi_call_proto(lf2, load_file, dp, false, &initrd->size, NULL);
+ if (status != EFI_BUFFER_TOO_SMALL)
+ return EFI_LOAD_ERROR;
+
+ status = efi_allocate_pages(initrd->size, &initrd->base, max);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = efi_call_proto(lf2, load_file, dp, false, &initrd->size,
+ (void *)initrd->base);
+ if (status != EFI_SUCCESS) {
+ efi_free(initrd->size, initrd->base);
+ return EFI_LOAD_ERROR;
+ }
+ return EFI_SUCCESS;
+}
+
+static
+efi_status_t efi_load_initrd_cmdline(efi_loaded_image_t *image,
+ struct linux_efi_initrd *initrd,
+ unsigned long soft_limit,
+ unsigned long hard_limit)
+{
+ if (image == NULL)
+ return EFI_UNSUPPORTED;
+
+ return handle_cmdline_files(image, L"initrd=", sizeof(L"initrd=") - 2,
+ soft_limit, hard_limit,
+ &initrd->base, &initrd->size);
+}
+
+/**
+ * efi_load_initrd() - Load initial RAM disk
+ * @image: EFI loaded image protocol
+ * @soft_limit: preferred address for loading the initrd
+ * @hard_limit: upper limit address for loading the initrd
+ *
+ * Return: status code
+ */
+efi_status_t efi_load_initrd(efi_loaded_image_t *image,
+ unsigned long soft_limit,
+ unsigned long hard_limit,
+ const struct linux_efi_initrd **out)
+{
+ efi_guid_t tbl_guid = LINUX_EFI_INITRD_MEDIA_GUID;
+ efi_status_t status = EFI_SUCCESS;
+ struct linux_efi_initrd initrd, *tbl;
+
+ if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD) || efi_noinitrd)
+ return EFI_SUCCESS;
+
+ status = efi_load_initrd_dev_path(&initrd, hard_limit);
+ if (status == EFI_SUCCESS) {
+ efi_info("Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path\n");
+ if (initrd.size > 0 &&
+ efi_measure_tagged_event(initrd.base, initrd.size,
+ EFISTUB_EVT_INITRD) == EFI_SUCCESS)
+ efi_info("Measured initrd data into PCR 9\n");
+ } else if (status == EFI_NOT_FOUND) {
+ status = efi_load_initrd_cmdline(image, &initrd, soft_limit,
+ hard_limit);
+ /* command line loader disabled or no initrd= passed? */
+ if (status == EFI_UNSUPPORTED || status == EFI_NOT_READY)
+ return EFI_SUCCESS;
+ if (status == EFI_SUCCESS)
+ efi_info("Loaded initrd from command line option\n");
+ }
+ if (status != EFI_SUCCESS)
+ goto failed;
+
+ status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, sizeof(initrd),
+ (void **)&tbl);
+ if (status != EFI_SUCCESS)
+ goto free_initrd;
+
+ *tbl = initrd;
+ status = efi_bs_call(install_configuration_table, &tbl_guid, tbl);
+ if (status != EFI_SUCCESS)
+ goto free_tbl;
+
+ if (out)
+ *out = tbl;
+ return EFI_SUCCESS;
+
+free_tbl:
+ efi_bs_call(free_pool, tbl);
+free_initrd:
+ efi_free(initrd.size, initrd.base);
+failed:
+ efi_err("Failed to load initrd: 0x%lx\n", status);
+ return status;
+}
+
+/**
+ * efi_wait_for_key() - Wait for key stroke
+ * @usec: number of microseconds to wait for key stroke
+ * @key: key entered
+ *
+ * Wait for up to @usec microseconds for a key stroke.
+ *
+ * Return: status code, EFI_SUCCESS if key received
+ */
+efi_status_t efi_wait_for_key(unsigned long usec, efi_input_key_t *key)
+{
+ efi_event_t events[2], timer;
+ unsigned long index;
+ efi_simple_text_input_protocol_t *con_in;
+ efi_status_t status;
+
+ con_in = efi_table_attr(efi_system_table, con_in);
+ if (!con_in)
+ return EFI_UNSUPPORTED;
+ efi_set_event_at(events, 0, efi_table_attr(con_in, wait_for_key));
+
+ status = efi_bs_call(create_event, EFI_EVT_TIMER, 0, NULL, NULL, &timer);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = efi_bs_call(set_timer, timer, EfiTimerRelative,
+ EFI_100NSEC_PER_USEC * usec);
+ if (status != EFI_SUCCESS)
+ return status;
+ efi_set_event_at(events, 1, timer);
+
+ status = efi_bs_call(wait_for_event, 2, events, &index);
+ if (status == EFI_SUCCESS) {
+ if (index == 0)
+ status = efi_call_proto(con_in, read_keystroke, key);
+ else
+ status = EFI_TIMEOUT;
+ }
+
+ efi_bs_call(close_event, timer);
+
+ return status;
+}
+
+/**
+ * efi_remap_image - Remap a loaded image with the appropriate permissions
+ * for code and data
+ *
+ * @image_base: the base of the image in memory
+ * @alloc_size: the size of the area in memory occupied by the image
+ * @code_size: the size of the leading part of the image containing code
+ * and read-only data
+ *
+ * efi_remap_image() uses the EFI memory attribute protocol to remap the code
+ * region of the loaded image read-only/executable, and the remainder
+ * read-write/non-executable. The code region is assumed to start at the base
+ * of the image, and will therefore cover the PE/COFF header as well.
+ */
+void efi_remap_image(unsigned long image_base, unsigned alloc_size,
+ unsigned long code_size)
+{
+ efi_guid_t guid = EFI_MEMORY_ATTRIBUTE_PROTOCOL_GUID;
+ efi_memory_attribute_protocol_t *memattr;
+ efi_status_t status;
+ u64 attr;
+
+ /*
+ * If the firmware implements the EFI_MEMORY_ATTRIBUTE_PROTOCOL, let's
+ * invoke it to remap the text/rodata region of the decompressed image
+ * as read-only and the data/bss region as non-executable.
+ */
+ status = efi_bs_call(locate_protocol, &guid, NULL, (void **)&memattr);
+ if (status != EFI_SUCCESS)
+ return;
+
+ // Get the current attributes for the entire region
+ status = memattr->get_memory_attributes(memattr, image_base,
+ alloc_size, &attr);
+ if (status != EFI_SUCCESS) {
+ efi_warn("Failed to retrieve memory attributes for image region: 0x%lx\n",
+ status);
+ return;
+ }
+
+ // Mark the code region as read-only
+ status = memattr->set_memory_attributes(memattr, image_base, code_size,
+ EFI_MEMORY_RO);
+ if (status != EFI_SUCCESS) {
+ efi_warn("Failed to remap code region read-only\n");
+ return;
+ }
+
+ // If the entire region was already mapped as non-exec, clear the
+ // attribute from the code region. Otherwise, set it on the data
+ // region.
+ if (attr & EFI_MEMORY_XP) {
+ status = memattr->clear_memory_attributes(memattr, image_base,
+ code_size,
+ EFI_MEMORY_XP);
+ if (status != EFI_SUCCESS)
+ efi_warn("Failed to remap code region executable\n");
+ } else {
+ status = memattr->set_memory_attributes(memattr,
+ image_base + code_size,
+ alloc_size - code_size,
+ EFI_MEMORY_XP);
+ if (status != EFI_SUCCESS)
+ efi_warn("Failed to remap data region non-executable\n");
+ }
+}