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...
jirka
