[PATCH] i386: Don't allow GOTOFF relocation against IFUNC symbol for PIC

[H.J. Lu]

On Thu, Jul 21, 2022 at 10:40 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> We can't use the PLT entry as the function address for PIC since the PIC
> register may not be set up properly for indirect call.
>
> bfd/
>
>         PR ld/27998
>         * elf32-i386.c (elf_i386_relocate_section): Don't allow GOTOFF
>         relocation against IFUNC symbol in PIC.
>
> ld/
>
>         PR ld/27998
>         * testsuite/ld-i386/pr27998a.d: Replace -shared with -e bar.
>         * testsuite/ld-i386/pr27998b.d: Expect a linker error.
>         * testsuite/ld-ifunc/ifunc-2-i386-now.d: Updated.
>         * testsuite/ld-ifunc/ifunc-2-local-i386-now.d: Likewise.
>         * testsuite/ld-ifunc/ifunc-2-i386.s: Replace @GOTOFF with @GOT.
>         * testsuite/ld-ifunc/ifunc-2-local-i386.s: Likewise.
> ---
>  bfd/elf32-i386.c                               | 5 +++++
>  ld/testsuite/ld-i386/pr27998a.d                | 2 +-
>  ld/testsuite/ld-i386/pr27998b.d                | 6 +-----
>  ld/testsuite/ld-ifunc/ifunc-2-i386-now.d       | 2 +-
>  ld/testsuite/ld-ifunc/ifunc-2-i386.s           | 2 +-
>  ld/testsuite/ld-ifunc/ifunc-2-local-i386-now.d | 2 +-
>  ld/testsuite/ld-ifunc/ifunc-2-local-i386.s     | 2 +-
>  7 files changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
> index cfb0085b245..52b1db44546 100644
> --- a/bfd/elf32-i386.c
> +++ b/bfd/elf32-i386.c
> @@ -2460,6 +2460,11 @@ elf_i386_relocate_section (bfd *output_bfd,
>               goto do_relocation;
>
>             case R_386_GOTOFF:
> +             /* NB: We can't use the PLT entry as the function address
> +                for PIC since the PIC register may not be set up
> +                properly for indirect call. */
> +             if (bfd_link_pic (info))
> +               goto bad_ifunc_reloc;
>               relocation -= (gotplt->output_section->vma
>                              + gotplt->output_offset);
>               goto do_relocation;
> diff --git a/ld/testsuite/ld-i386/pr27998a.d b/ld/testsuite/ld-i386/pr27998a.d
> index ca3c9205fa6..a8019730ec1 100644
> --- a/ld/testsuite/ld-i386/pr27998a.d
> +++ b/ld/testsuite/ld-i386/pr27998a.d
> @@ -1,5 +1,5 @@
>  #as: --32
> -#ld: -shared -melf_i386
> +#ld: -e bar -melf_i386
>  #readelf: -r --wide
>
>  Relocation section '.rel.plt' at offset 0x[0-9a-f]+ contains 1 entry:
> diff --git a/ld/testsuite/ld-i386/pr27998b.d b/ld/testsuite/ld-i386/pr27998b.d
> index ca3c9205fa6..8f81edbe8df 100644
> --- a/ld/testsuite/ld-i386/pr27998b.d
> +++ b/ld/testsuite/ld-i386/pr27998b.d
> @@ -1,7 +1,3 @@
>  #as: --32
>  #ld: -shared -melf_i386
> -#readelf: -r --wide
> -
> -Relocation section '.rel.plt' at offset 0x[0-9a-f]+ contains 1 entry:
> - Offset     Info    Type                Sym. Value  Symbol's Name
> -[0-9a-f]+ +[0-9a-f]+ +R_386_IRELATIVE +
> +#error: relocation R_386_GOTOFF against STT_GNU_IFUNC symbol `foo' isn't supported
> diff --git a/ld/testsuite/ld-ifunc/ifunc-2-i386-now.d b/ld/testsuite/ld-ifunc/ifunc-2-i386-now.d
> index a5c56b5a8e3..8d9e8dc988f 100644
> --- a/ld/testsuite/ld-ifunc/ifunc-2-i386-now.d
> +++ b/ld/testsuite/ld-ifunc/ifunc-2-i386-now.d
> @@ -31,6 +31,6 @@ Disassembly of section .text:
>   +[a-f0-9]+:   5b                      pop    %ebx
>   +[a-f0-9]+:   81 c3 9e 10 00 00       add    \$0x109e,%ebx
>   +[a-f0-9]+:   e8 de ff ff ff          call   100 <\*ABS\*@plt>
> - +[a-f0-9]+:   8d 83 4c ef ff ff       lea    -0x10b4\(%ebx\),%eax
> + +[a-f0-9]+:   8b 83 0c 00 00 00       mov    0xc\(%ebx\),%eax
>   +[a-f0-9]+:   c3                      ret
>  #pass
> diff --git a/ld/testsuite/ld-ifunc/ifunc-2-i386.s b/ld/testsuite/ld-ifunc/ifunc-2-i386.s
> index e84d6b7b5cc..1acf6847e0b 100644
> --- a/ld/testsuite/ld-ifunc/ifunc-2-i386.s
> +++ b/ld/testsuite/ld-ifunc/ifunc-2-i386.s
> @@ -16,6 +16,6 @@ bar:
>         popl    %ebx
>         addl    $_GLOBAL_OFFSET_TABLE_+[.-.L6], %ebx
>         call    __GI_foo@PLT
> -       leal    __GI_foo@GOTOFF(%ebx), %eax
> +       movl    __GI_foo@GOT(%ebx), %eax
>         ret
>         .size   bar, .-bar
> diff --git a/ld/testsuite/ld-ifunc/ifunc-2-local-i386-now.d b/ld/testsuite/ld-ifunc/ifunc-2-local-i386-now.d
> index ff494decbdd..9da37e51db7 100644
> --- a/ld/testsuite/ld-ifunc/ifunc-2-local-i386-now.d
> +++ b/ld/testsuite/ld-ifunc/ifunc-2-local-i386-now.d
> @@ -31,6 +31,6 @@ Disassembly of section .text:
>   +[a-f0-9]+:   5b                      pop    %ebx
>   +[a-f0-9]+:   81 c3 9e 10 00 00       add    \$0x109e,%ebx
>   +[a-f0-9]+:   e8 de ff ff ff          call   f0 <\*ABS\*@plt>
> - +[a-f0-9]+:   8d 83 4c ef ff ff       lea    -0x10b4\(%ebx\),%eax
> + +[a-f0-9]+:   8b 83 0c 00 00 00       mov    0xc\(%ebx\),%eax
>   +[a-f0-9]+:   c3                      ret
>  #pass
> diff --git a/ld/testsuite/ld-ifunc/ifunc-2-local-i386.s b/ld/testsuite/ld-ifunc/ifunc-2-local-i386.s
> index a69e060ddc0..54e0e179551 100644
> --- a/ld/testsuite/ld-ifunc/ifunc-2-local-i386.s
> +++ b/ld/testsuite/ld-ifunc/ifunc-2-local-i386.s
> @@ -13,6 +13,6 @@ bar:
>         popl    %ebx
>         addl    $_GLOBAL_OFFSET_TABLE_+[.-.L6], %ebx
>         call    __GI_foo@PLT
> -       leal    __GI_foo@GOTOFF(%ebx), %eax
> +       movl    __GI_foo@GOT(%ebx), %eax
>         ret
>         .size   bar, .-bar
> --
> 2.36.1
>

I am backporting this to 2.38 and 2.39 branches.

-- 
H.J.