On Tue, Feb 24, 2009 at 3:53 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
> On Mon, Feb 23, 2009 at 11:46 PM, Jiri Olsa <olsaj...@gmail.com> wrote:
>> On Mon, Feb 23, 2009 at 7:48 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>> On Mon, Feb 23, 2009 at 10:39 AM, Jiri Olsa <olsaj...@gmail.com> wrote:
>>>> On Mon, Feb 23, 2009 at 7:35 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>>>> On Mon, Feb 23, 2009 at 10:05 AM, Jiri Olsa <olsaj...@gmail.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> my shared library crashes with movaps instruction using not aligned
>>>>>> memory.
>>>>>>
>>>>>> Since the shared library function is being called from dynamic linker,
>>>>>> which
>>>>>> basically prepares the memory location, I'm not sure whoose side issues
>>>>>> this is.
>>>>>>
>>>>>> I have following function in C:
>>>>>>
>>>>>> typedef float La_x86_64_xmm __attribute__ ((__vector_size__ (16)));
>>>>>>
>>>>>> typedef struct La_x86_64_retval
>>>>>> {
>>>>>> uint64_t lrv_rax;
>>>>>> uint64_t lrv_rdx;
>>>>>> La_x86_64_xmm lrv_xmm0;
>>>>>> La_x86_64_xmm lrv_xmm1;
>>>>>> long double lrv_st0;
>>>>>> long double lrv_st1;
>>>>>> } La_x86_64_retval;
>>>>>>
>>>>>> unsigned int la_x86_64_gnu_pltexit (Elf64_Sym *__sym,
>>>>>> unsigned int __ndx, uintptr_t *__refcook, uintptr_t
>>>>>> *__defcook,
>>>>>> const La_x86_64_regs *__inregs, La_x86_64_retval
>>>>>> *__outregs, const char *symname)
>>>>>> {
>>>>>> La_x86_64_xmm b __attribute__ ((aligned(16)));
>>>>>> b = __outregs->lrv_xmm0;
>>>>>> return 0;
>>>>>> }
>>>>>>
>>>>>> this will endup in following assembly:
>>>>>>
>>>>>> 00000000000007d7 <la_x86_64_gnu_pltexit>:
>>>>>> 7d7: 55 push %rbp
>>>>>> 7d8: 48 89 e5 mov %rsp,%rbp
>>>>>> 7db: 48 89 7d e8 mov %rdi,-0x18(%rbp)
>>>>>> 7df: 89 75 e4 mov %esi,-0x1c(%rbp)
>>>>>> 7e2: 48 89 55 d8 mov %rdx,-0x28(%rbp)
>>>>>> 7e6: 48 89 4d d0 mov %rcx,-0x30(%rbp)
>>>>>> 7ea: 4c 89 45 c8 mov %r8,-0x38(%rbp)
>>>>>> 7ee: 4c 89 4d c0 mov %r9,-0x40(%rbp)
>>>>>> 7f2: 48 8b 45 c0 mov -0x40(%rbp),%rax
>>>>>> 7f6: 0f 28 40 10 movaps 0x10(%rax),%xmm0
>>>>>> 7fa: 0f 29 45 f0 movaps %xmm0,-0x10(%rbp)
>>>>>> 7fe: b8 00 00 00 00 mov $0x0,%eax
>>>>>> 803: c9 leaveq
>>>>>> 804: c3 retq
>>>>>>
>>>>>>
>>>>>> Looks like xmm0 register is being used to transfer the data. However
>>>>>> the structure's alignment is not 16, so it will crash.
>>>>>>
>>>>>
>>>>> Where exactly is it crashed? Which the structure isn't aligned at 16byte?
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> H.J.
>>>>>
>>>>
>>>>
>>>> sry, it crashes on this one
>>>>
>>>> 7f6: 0f 28 40 10 movaps 0x10(%rax),%xmm0
>>>>
>>>> This structure/argument is not aligned at 16
>>>> La_x86_64_retval *__outreg
>>>>
>>>> the '__outregs->lrv_xmm0' is at 16th byte of the structure...
>>>>
>>>
>>> Why isn't __outregs aligned at 16byte? According to x86-64 psABI,
>>> La_x86_64_retval should be aligned at 16byte.
>>>
>>>
>>>
>>> --
>>> H.J.
>>>
>>
>> thanks,
>>
>> then the issue is in the glibc dynamic linker _dl_runtime_profile function
>> (sysdeps/x86_64/dl-trampoline.S). Looks like it should ensure
>> the outregs parameter is aligned to 16.
>>
>> resending to the glibc mailing lists
>>
>> the gdb session showing not aligned outregs parameter of the
>> _dl_call_pltexit func:
>>
>> ...
>> (gdb) b _dl_call_pltexit
>> Function "_dl_call_pltexit" not defined.
>> Make breakpoint pending on future shared library load? (y or [n]) y
>> Breakpoint 1 (_dl_call_pltexit) pending.
>> (gdb) r
>> Starting program: /opt/crash
>> symbol __libc_start_main
>> symbol printf
>>
>> Breakpoint 1, _dl_call_pltexit (l=0x7ffff7ffd000, reloc_offset=0,
>> inregs=0x7fffffffe418, outregs=0x7fffffffe3c8) at dl-runtime.c:408
>> 408 {
>> (gdb)
>>
>>
>> I'm using the latest glibc git code
>> (commit a839a1d3f4fbc0d75acd0dc4cad10cf6141e4963)
>>
>> let me know if you need more info..
>>
>
> Please open a glibc bug with a complete testcase so that
> people can reproduce it.
>
> --
> H.J.
>
created bug 9893
http://sources.redhat.com/bugzilla/show_bug.cgi?id=9893
let me know if I can help with smth,
jirka
