Messages in this thread | | | Date | Sat, 26 Aug 2023 23:04:45 +0700 | From | Ammar Faizi <> | Subject | Re: [PATCH v1 0/1] Fix a stack misalign bug on _start |
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On Sat, Aug 26, 2023 at 11:20:24PM +0800, Zhangjin Wu wrote: > > $eax : 0x56559000 → 0x00003f90 > > $ebx : 0x56559000 → 0x00003f90 > > $ecx : 0x1 > > $edx : 0xf7fcaaa0 → endbr32 > > $esp : 0xffffcdbc → 0x00000001 > > $ebp : 0x0 > > $esi : 0xffffce7c → 0xffffd096 > > $edi : 0x56556060 → <_start+0> xor %ebp, %ebp > > $eip : 0x56556489 → <sse_pq_add+25> movaps %xmm0, 0x30(%esp) > > > > <sse_pq_add+11> pop %eax > > <sse_pq_add+12> add $0x2b85, %eax > > <sse_pq_add+18> movups -0x1fd0(%eax), %xmm0 > > → <sse_pq_add+25> movaps %xmm0, 0x30(%esp) <== trapping instruction > > <sse_pq_add+30> movups -0x1fe0(%eax), %xmm1 > > <sse_pq_add+37> movaps %xmm1, 0x20(%esp) > > <sse_pq_add+42> movups -0x1ff0(%eax), %xmm2 > > <sse_pq_add+49> movaps %xmm2, 0x10(%esp) > > <sse_pq_add+54> movups -0x2000(%eax), %xmm3 > > > > [#0] Id 1, Name: "test", stopped 0x56556489 in sse_pq_add (), reason: SIGSEGV > > > > (gdb) bt > > #0 0x56556489 in sse_pq_add () > > #1 0x5655608e in main () > > > > Since we have a new 'startup' test group, do you have a short function > to trigger this error?
Here is a simple program to test the stack alignment.
#include "tools/include/nolibc/nolibc.h"
__asm__ ( "main:\n" /* * When the call main is executed, the * %esp is 16 bytes aligned. * * Then, on function entry (%esp mod 16) == 12 * because the call instruction pushes 4 bytes * onto the stack. * * subl $12, %esp will make (%esp mod 16) == 0 * again. */ "subl $12, %esp\n"
/* * These move instructions will crash if %esp is * not a multiple of 16. */ "movdqa (%esp), %xmm0\n" "movdqa %xmm0, (%esp)\n" "movaps (%esp), %xmm0\n" "movaps %xmm0, (%esp)\n"
"addl $12, %esp\n" "xorl %eax, %eax\n" "ret\n" );
> Perhaps it is time for us to add a new 'stack alignment' test case for > all of the architectures.
I don't know the alignment rules for other architectures (I only work on x86 and x86-64). While waiting for the maintainers' comment, I'll leave the test case decision to you. Feel free to take the above code.
Extra: It's also fine if you take my patch with the 'sub $(16 - 4), %esp' change and batch it together in your next series.
-- Ammar Faizi
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