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Message-ID: <ZOoindMFj1UKqo+s@biznet-home.integral.gnuweeb.org>
Date: Sat, 26 Aug 2023 23:04:45 +0700
From: Ammar Faizi <ammarfaizi2@...weeb.org>
To: Zhangjin Wu <falcon@...ylab.org>
Cc: Willy Tarreau <w@....eu>,
Thomas Weißschuh <linux@...ssschuh.net>,
Nicholas Rosenberg <inori@...x.org>,
GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
Michael William Jonathan <moe@...weeb.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 0/1] Fix a stack misalign bug on _start
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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