Re: boot/grub2: grub-core-build-fixes-for-i386 (grub-2.04 + binutils-2.35.2 + pseudo-op .code64)

[Daniel Kiper]

Hi,

Thank you for the report...

On Wed, May 05, 2021 at 12:44:07PM +0300, Mikhail B. WproxyM wrote:
> We are using binutils-2.35.2+ (later then 2.29.1), grub-2.04,
> cross-compiling on recent buildroot under i386/i686 and getting error:

May I ask you to try latest GRUB master git branch [1]? The GRUB 2.04
release is a few years old. We are going to release 2.06 soon.

> > lib/i386/relocator64.S:66: Error: unknown pseudo-op: `.code64'
>
> So, the working patch is attached. Please add it to grub2.

You can find a few comments below...

> From 270667540146f8ef9ea7a44258a71b3837a7af4a Mon Sep 17 00:00:00 2001
> From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
> Date: Sun, 21 Jun 2020 15:10:40 +0200
> Subject: [PATCH] grub-core: Build fixes for i386
>
> * grub-core/lib/i386/relocator64.S: Avoid x86_64 instructions on i386.

Please describe in the commit message why this patch is needed and how
the issue can be reproduced.

Please add your "Signed-off-by: ..." line at the end of commit message.
You can find good examples of commit messages in the GRUB git repository.

> ---
>  grub-core/lib/i386/relocator64.S | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/lib/i386/relocator64.S 
> b/grub-core/lib/i386/relocator64.S
> index 148f38adb..45fed9444 100644
> --- a/grub-core/lib/i386/relocator64.S
> +++ b/grub-core/lib/i386/relocator64.S
> @@ -63,7 +63,9 @@ VARIABLE(grub_relocator64_cr3)
>       movq    %rax, %cr3
>  #endif
>
> +#ifdef __x86_64__
>       .code64
> +#endif
>
>       /* mov imm64, %rax */
>       .byte   0x48
> @@ -71,7 +73,14 @@ VARIABLE(grub_relocator64_cr3)
>  VARIABLE(grub_relocator64_rsp)
>       .quad   0
>
> +#ifndef __x86_64__
> +     /* movq %rax, %rsp */
> +     .byte   0x48
> +     .byte   0x89
> +     .byte   0xc4
> +#else
>       movq    %rax, %rsp
> +#endif

I would do it other way around to increase readability...

#ifdef __x86_64__
     movq    %rax, %rsp
#else
     /* movq %rax, %rsp */
     .byte   0x48
     ...

>  #ifdef GRUB_MACHINE_EFI
>       jmp     LOCAL(skip_efi_stack_align)
> @@ -95,8 +104,15 @@ LOCAL(skip_efi_stack_align):
>  VARIABLE(grub_relocator64_rsi)
>       .quad   0
>
> +#ifndef      __x86_64__
> +     /* movq %rax, %rsi */
> +     .byte   0x48
> +     .byte   0x89
> +     .byte   0xc6
> +#else
>       movq    %rax, %rsi
> -
> +#endif

Ditto...

>       /* mov imm64, %rax */
>       .byte   0x48
>       .byte   0xb8
> @@ -128,6 +144,14 @@ VARIABLE(grub_relocator64_rdx)
>  #ifdef __APPLE__
>       .byte 0xff, 0x25
>       .quad 0
> +#elif !defined (__x86_64__)
> +     /* jmp *LOCAL(jump_addr) (%rip) */
> +     .byte 0xff
> +        .byte 0x25
> +     .byte 0
> +     .byte 0
> +     .byte 0
> +     .byte 0
>  #else
>       jmp *LOCAL(jump_addr) (%rip)
>  #endif

#if defined(__APPLE__) || !defined (__x86_64__)
     .byte 0xff, 0x25
     .quad 0
#else
     jmp *LOCAL(jump_addr) (%rip)
#endif

A patch should be prepared on top of latest GRUB master git branch [1].
And please use "git-send-email" to send the patch as Adrian said...

Daniel

[1] https://git.savannah.gnu.org/gitweb/?p=grub.git&view=view+git+repository