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authorArd Biesheuvel <ardb@kernel.org>2023-01-30 13:11:53 +0100
committerArd Biesheuvel <ardb@kernel.org>2023-02-03 16:39:22 +0100
commitace013a543067ed33cf593144b18c6dbeb517cee (patch)
treee8ac02270bc42999f408249ffe7f748f730473ff
parent79729f26b074a5d2722c27fa76cc45ef721e65cd (diff)
downloadlinux-ace013a543067ed33cf593144b18c6dbeb517cee.tar.gz
efi: zboot: Use EFI protocol to remap code/data with the right attributes
Use the recently introduced EFI_MEMORY_ATTRIBUTES_PROTOCOL in the zboot implementation to set the right attributes for the code and data sections of the decompressed image, i.e., EFI_MEMORY_RO for code and EFI_MEMORY_XP for data. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
-rw-r--r--drivers/firmware/efi/libstub/efi-stub-helper.c67
-rw-r--r--drivers/firmware/efi/libstub/efistub.h3
-rw-r--r--drivers/firmware/efi/libstub/zboot.c2
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: