ld: Section corrupted with elf64-x86-64 input -> elf32-i386 output

[H.J. Lu]

On Sun, Sep 27, 2015 at 4:34 AM, Antoine Kaufmann <toni@famkaufmann.info> wrote:
> Hey,
>
> I ran into some weird behavior, most likely a bug, in in admittedly even
> weirder setting... So I figured I'd check here if I'm missing something and
> that's somehow the expected behavior, before I'd file a bug.
>
> Basically I'm linking elf64-x86-64 files together and outputting a elf32-i386
> executable (long story, involving a mix of 32 bit and 64 bit code running bare
> metal). Now I noticed that some of my string constants were getting corrupted
> during linking, truncated mostly. I've tried to reduce this to a minimal
> example to show what happens (tested with debian's 2.25.1 and a recent git
> version):
>
>> $ cat a.s
>> .section      .rodata.str1.1,"aMS",@progbits,1
>> .byte 0x0, 0x0, 0x2, 0x3, 0x0
>> .string       "ABCD"
>>
>> $ as -o a.o a.s
>> $ ld --oformat elf32-i386 -o b a.o
>> ld: warning: cannot find entry symbol _start; defaulting to 0000000000400054
>>
>> $ objdump -s -j .rodata.str1.1 a.o
>>
>> a.o:     file format elf64-x86-64
>>
>> Contents of section .rodata.str1.1:
>>  0000 00000203 00414243 4400               .....ABCD.
>> + objdump -s -j .rodata b
>>
>> b:     file format elf32-i386
>>
>> Contents of section .rodata:
>>  400054 00000203 00414243                    .....ABC
>
> Is there something I'm missing or is this a bug? If the latter, any suggestions
> on where I should start looking into the code?
>

Please open a binutils bug report with a testcase.  I will investigate it.

Thanks.

-- 
H.J.