Re: [PATCH v5] MIPS: Reject branch absolute relocs for PIC for linking

[YunQiang Su <syq@gcc.gnu.org>]

YunQiang Su <syq@gcc.gnu.org> 于2024年2月8日周四 01:31写道：
>
> The asm code like:
>         b       (8)
> will emit absolute relocs like:
>         R_MIPS_PC16     *ABS*
>
> If they are included into PIC shared objects or PIE executables,
> the branch target will be like 0x12340000, which will make the
> programs crash.

@Maciej ping.

> ---
>  bfd/elfxx-mips.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/bfd/elfxx-mips.c b/bfd/elfxx-mips.c
> index 69dd71419ff..9542250dec4 100644
> --- a/bfd/elfxx-mips.c
> +++ b/bfd/elfxx-mips.c
> @@ -9258,6 +9258,15 @@ _bfd_mips_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
>                    (h) ? h->root.root.string : "a local symbol");
>               break;
>             default:
> +             if (branch_reloc_p (r_type) && r_symndx == STN_UNDEF)
> +               {
> +                 howto = MIPS_ELF_RTYPE_TO_HOWTO (abfd, r_type, NEWABI_P (abfd));
> +                 info->callbacks->einfo
> +                   /* xgettext:c-format */
> +                   (_("%X%H: relocation %s against `*ABS*' cannot be used"
> +                      " when making a PIC/PIE object\n"),
> +                    abfd, sec, rel->r_offset, howto->name);
> +               }
>               break;
>             }
>         }
> --
> 2.39.2
>