efi/zboot: arm64: Grab code size from ELF symbol in payload

Instead of relying on a dodgy dd hack to copy the image code size from
the uncompressed image's PE header to the end of the compressed image,
let's grab the code size from the symbol that is injected into the ELF
object by the Kbuild rules that generate the compressed payload.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>

1 files changed, 4 insertions, 11 deletions

diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
index 63ece4800900..e5d7fa1f1d8f 100644
--- a/drivers/firmware/efi/libstub/zboot.c
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -50,8 +50,7 @@ static unsigned long alloc_preferred_address(unsigned long alloc_size)
 }
 
 void __weak efi_cache_sync_image(unsigned long image_base,
-				 unsigned long alloc_size,
-				 unsigned long code_size)
+				 unsigned long alloc_size)
 {
 	// Provided by the arch to perform the cache maintenance necessary for
 	// executable code loaded into memory to be safe for execution.
@@ -66,7 +65,7 @@ asmlinkage efi_status_t __efiapi
 efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
 {
 	unsigned long compressed_size = _gzdata_end - _gzdata_start;
-	unsigned long image_base, alloc_size, code_size;
+	unsigned long image_base, alloc_size;
 	efi_loaded_image_t *image;
 	efi_status_t status;
 	char *cmdline_ptr;
@@ -91,13 +90,9 @@ efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
 	efi_info("Decompressing Linux Kernel...\n");
 
 	// SizeOfImage from the compressee's PE/COFF header
-	alloc_size = round_up(get_unaligned_le32(_gzdata_end - 12),
+	alloc_size = round_up(get_unaligned_le32(_gzdata_end - 4),
 			      EFI_ALLOC_ALIGN);
 
-	// SizeOfHeaders and SizeOfCode from the compressee's PE/COFF header
-	code_size = get_unaligned_le32(_gzdata_end - 4) +
-		    get_unaligned_le32(_gzdata_end - 8);
-
 	 // If the architecture has a preferred address for the image,
 	 // try that first.
 	image_base = alloc_preferred_address(alloc_size);
@@ -140,9 +135,7 @@ efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
 		goto free_image;
 	}
 
-	efi_cache_sync_image(image_base, alloc_size, code_size);
-
-	efi_remap_image(image_base, alloc_size, code_size);
+	efi_cache_sync_image(image_base, alloc_size);
 
 	status = efi_stub_common(handle, image, image_base, cmdline_ptr);