From: Ammar Faizi <[email protected]>
To: "Willy Tarreau" <[email protected]>, "Thomas Weißschuh" <[email protected]>
Cc: Ammar Faizi <[email protected]>,
Zhangjin Wu <[email protected]>,
Nicholas Rosenberg <[email protected]>,
Michael William Jonathan <[email protected]>,
GNU/Weeb Mailing List <[email protected]>,
Linux Kernel Mailing List <[email protected]>
Subject: [PATCH v3 0/1] Fix a stack misalign bug on _start
Date: Wed, 30 Aug 2023 08:02:22 +0700 [thread overview]
Message-ID: <[email protected]> (raw)
Hi Willy,
This is a v3 revision.
The ABI mandates that the %esp register must be a multiple of 16 when
executing a 'call' instruction.
Commit 2ab446336b17 ("tools/nolibc: i386: shrink _start with _start_c")
simplified the _start function, but it didn't take care of the %esp
alignment, causing SIGSEGV on SSE and AVX programs that use aligned move
instruction (e.g., movdqa, movaps, and vmovdqa).
$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 ()
Ensure the %esp is a multiple of 16 when executing the call instruction.
Changes since v2:
- Avoid over-estimating the stack size (per Willy).
- Add the link to a test program to validate the alignment (per Zhangjin).
Changes since v1:
- Change 'sub $12, %esp' to 'sub $(16 - 4), %esp' (per Zhangjin).
- Fix the reference format (per Thomas).
- Explain more about the logic behind the fix (per Thomas).
- Append an Acked-by tag from Thomas.
Signed-off-by: Ammar Faizi <[email protected]>
---
Ammar Faizi (1):
tools/nolibc: i386: Fix a stack misalign bug on _start
tools/include/nolibc/arch-i386.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
base-commit: 6269320850097903b30be8f07a5c61d9f7592393
--
Ammar Faizi
next reply other threads:[~2023-08-30 1:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 1:02 Ammar Faizi [this message]
2023-08-30 1:02 ` [PATCH v3 1/1] tools/nolibc: i386: Fix a stack misalign bug on _start Ammar Faizi
2023-08-30 3:45 ` [PATCH v3 0/1] " Willy Tarreau
2023-08-30 4:07 ` Alviro Iskandar Setiawan
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