[PATCH] D30699: [ELF] - Stop producing broken output for R_386_GOT32X relocation.

[H.J. Lu via llvm-commits]

On Fri, Mar 31, 2017 at 8:01 AM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
>> [hjl at gnu-6 tmp]$ cat y.s
>> .text
>> .globl _start
>> _start:
>> cmp %eax, _start at GOT
>> [hjl at gnu-6 tmp]$ gcc -m32 -c y.s
>> [hjl at gnu-6 tmp]$ objdump -dwr y.o
>>
>> y.o:     file format elf32-i386
>>
>>
>> Disassembly of section .text:
>>
>> 00000000 <_start>:
>>    0: 39 05 00 00 00 00     cmp    %eax,0x0 2: R_386_GOT32 _start
>> [hjl at gnu-6 tmp]$ ld -m elf_i386 y.o
>> [hjl at gnu-6 tmp]$ objdump -dw a.out
>>
>> a.out:     file format elf32-i386
>>
>>
>> Disassembly of section .text:
>>
>> 08048094 <_start>:
>>  8048094: 39 05 fc 9f 04 08     cmp    %eax,0x8049ffc
>> [hjl at gnu-6 tmp]$
>>
>> In this case, R_386_GOT32 is computed as G + A, not G + A - GOT.
>
> OK, the current situation with gas and bfd ld is somewhat amusing. Given
>
> mov _start at GOT, %eax
> cmp _start at GOT, %eax
>
> assembled with an old gas we get two R_386_GOT32. After linking, the result is
>
>  8048094:       a1 fc ff ff ff          mov    0xfffffffc,%eax
>  8048099:       3b 05 fc 9f 04 08       cmp    0x8049ffc,%eax
>
> Would it be ok in your opinion then for an implementation to treat
> R_386_GOT32X as just a relaxable R_386_GOT32 but unlike bfd produce
> G+A for both the mov and cmp above?
>

It is OK.

-- 
H.J.