diff options
| -rw-r--r-- | drivers/firmware/efi/libstub/efi-stub-helper.c | 67 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/efistub.h | 3 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/zboot.c | 2 |
3 files changed, 72 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c index f5a4bdacac64..1e0203d74691 100644 --- a/drivers/firmware/efi/libstub/efi-stub-helper.c +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c @@ -651,3 +651,70 @@ efi_status_t efi_wait_for_key(unsigned long usec, efi_input_key_t *key) 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"); + } +} diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h index 5388c7a9eb16..6bd3bb86d967 100644 --- a/drivers/firmware/efi/libstub/efistub.h +++ b/drivers/firmware/efi/libstub/efistub.h @@ -1096,4 +1096,7 @@ struct efi_smbios_type1_record { const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize); +void efi_remap_image(unsigned long image_base, unsigned alloc_size, + unsigned long code_size); + #endif diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c index 66be5fdc6b58..ba234e062a1a 100644 --- a/drivers/firmware/efi/libstub/zboot.c +++ b/drivers/firmware/efi/libstub/zboot.c @@ -137,6 +137,8 @@ efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab) efi_cache_sync_image(image_base, alloc_size, code_size); + efi_remap_image(image_base, alloc_size, code_size); + status = efi_stub_common(handle, image, image_base, cmdline_ptr); free_image: |