From d683bed5c76c54e6bc5c26eef2f8d7136a3c75c4 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Thu, 11 Aug 2022 16:51:57 +0200
Subject: [PATCH] loader/arm64/efi/linux: Remove magic number header field
 check

The "ARM\x64" magic number in the file header identifies an image as one
that implements the bare metal boot protocol, allowing the loader to
simply move the file to a suitably aligned address in memory, with
sufficient headroom for the trailing .bss segment (the required memory
size is described in the header as well).

Note of this matters for GRUB, as it only supports EFI boot. EFI does
not care about this magic number, and nor should GRUB: this prevents us
from booting other PE linux images, such as the generic EFI zboot
decompressor, which is a pure PE/COFF image, and does not implement the
bare metal boot protocol.

So drop the magic number check.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/loader/arm64/efi/linux.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/grub-core/loader/arm64/efi/linux.c b/grub-core/loader/arm64/efi/linux.c
index 33df0e1fd..a9f5e05e4 100644
--- a/grub-core/loader/arm64/efi/linux.c
+++ b/grub-core/loader/arm64/efi/linux.c
@@ -57,9 +57,6 @@ static grub_addr_t initrd_end;
 static grub_err_t
 grub_arch_efi_linux_check_image (struct linux_arch_kernel_header * lh)
 {
-  if (lh->magic != GRUB_LINUX_ARMXX_MAGIC_SIGNATURE)
-    return grub_error(GRUB_ERR_BAD_OS, "invalid magic number");
-
   if ((lh->code0 & 0xffff) != GRUB_PE32_MAGIC)
     return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
 		       N_("plain image kernel not supported - rebuild with CONFIG_(U)EFI_STUB enabled"));
-- 
2.43.0