efi: libstub: use EFI_LOADER_CODE region when moving the kernel in memory

The EFI spec is not very clear about which permissions are being given
when allocating pages of a certain type. However, it is quite obvious
that EFI_LOADER_CODE is more likely to permit execution than
EFI_LOADER_DATA, which becomes relevant once we permit booting the
kernel proper with the firmware's 1:1 mapping still active.

Ostensibly, recent systems such as the Surface Pro X grant executable
permissions to EFI_LOADER_CODE regions but not EFI_LOADER_DATA regions.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/alignedmem.c

@@ -22,7 +22,8 @@
  * Return:	status code
  */
 efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
-					unsigned long max, unsigned long align)
+					unsigned long max, unsigned long align,
+					int memory_type)
 {
 	efi_physical_addr_t alloc_addr;
 	efi_status_t status;
@@ -36,7 +37,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
 	slack = align / EFI_PAGE_SIZE - 1;
 
 	status = efi_bs_call(allocate_pages, EFI_ALLOCATE_MAX_ADDRESS,
-			     EFI_LOADER_DATA, size / EFI_PAGE_SIZE + slack,
+			     memory_type, size / EFI_PAGE_SIZE + slack,
 			     &alloc_addr);
 	if (status != EFI_SUCCESS)
 		return status;

drivers/firmware/efi/libstub/arm64-stub.c

@@ -102,7 +102,8 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 		 * locate the kernel at a randomized offset in physical memory.
 		 */
 		status = efi_random_alloc(*reserve_size, min_kimg_align,
-					  reserve_addr, phys_seed);
+					  reserve_addr, phys_seed,
+					  EFI_LOADER_CODE);
 		if (status != EFI_SUCCESS)
 			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
 	} else {
@@ -123,7 +124,8 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 		}
 
 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
-						    ULONG_MAX, min_kimg_align);
+						    ULONG_MAX, min_kimg_align,
+						    EFI_LOADER_CODE);
 
 		if (status != EFI_SUCCESS) {
 			efi_err("Failed to relocate kernel\n");

drivers/firmware/efi/libstub/efistub.h

@@ -880,7 +880,8 @@ void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
 efi_status_t efi_get_random_bytes(unsigned long size, u8 *out);
 
 efi_status_t efi_random_alloc(unsigned long size, unsigned long align,
-			      unsigned long *addr, unsigned long random_seed);
+			      unsigned long *addr, unsigned long random_seed,
+			      int memory_type);
 
 efi_status_t check_platform_features(void);
 
@@ -905,7 +906,8 @@ efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
 				unsigned long max);
 
 efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
-					unsigned long max, unsigned long align);
+					unsigned long max, unsigned long align,
+					int memory_type);
 
 efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
 				 unsigned long *addr, unsigned long min);

drivers/firmware/efi/libstub/mem.c

@@ -91,7 +91,8 @@ efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
 
 	if (EFI_ALLOC_ALIGN > EFI_PAGE_SIZE)
 		return efi_allocate_pages_aligned(size, addr, max,
-						  EFI_ALLOC_ALIGN);
+						  EFI_ALLOC_ALIGN,
+						  EFI_LOADER_DATA);
 
 	alloc_addr = ALIGN_DOWN(max + 1, EFI_ALLOC_ALIGN) - 1;
 	status = efi_bs_call(allocate_pages, EFI_ALLOCATE_MAX_ADDRESS,

drivers/firmware/efi/libstub/randomalloc.c

@@ -53,7 +53,8 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
 efi_status_t efi_random_alloc(unsigned long size,
 			      unsigned long align,
 			      unsigned long *addr,
-			      unsigned long random_seed)
+			      unsigned long random_seed,
+			      int memory_type)
 {
 	unsigned long total_slots = 0, target_slot;
 	unsigned long total_mirrored_slots = 0;
@@ -118,7 +119,7 @@ efi_status_t efi_random_alloc(unsigned long size,
 		pages = size / EFI_PAGE_SIZE;
 
 		status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
-				     EFI_LOADER_DATA, pages, &target);
+				     memory_type, pages, &target);
 		if (status == EFI_SUCCESS)
 			*addr = target;
 		break;