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.
