arm64/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.

---
 grub-core/loader/arm64/linux.c | 3 ---
 1 file changed, 3 deletions(-)

index ef3e9f9444ca..4c92e48ac91c 100644
@@ -51,9 +51,6 @@ static grub_addr_t initrd_end;
 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"));

2.35.1

Daniel