Issues seen with Grub2 and MULTIBOOT_HEADER_TAG_EFI_BS tag

[Gopakumar Thekkedath]

I have a multiboot2 compliant toy kernel for x86 architecture that I was
booting using Grub 2.04 (built with EFI support),   once I added the
MULTIBOOT_HEADER_TAG_EFI_BS tag as part of my kernel's Multiboot2 header,
the kernel does not boot any more. Now when I try to launch the kernel
using Grub, nothing much happens, the screen remains blank but it appears
that the system is not hung as CapsLock is functional. I have confirmed
that the control is not reaching my kernel.


Below is how the tag is in my code

efi_boot_srvc_tag_start:

.word   MULTIBOOT_HEADER_TAG_EFI_BS.word   0.long
efi_boot_srvc_tag_end - efi_boot_srvc_tag_start

efi_boot_srvc_tag_end:

And to add, I tried by making the tag optional using
MULTIBOOT_HEADER_TAG_OPTIONAL, but the behavior is the same.

When I did some debugging of Grub, it appears that control is reaching the
routine grub_relocator64_efi_boot, and eventually invokes ((void (*)
(void)) relst) ();

I am not sure where the control is going after this.

Any suggestions would be of great help.

Regards,
Gopa