From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <ammarfaizi2@gnuweeb.org>
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org
X-Spam-Level: 
X-Spam-Status: No, score=-1.2 required=5.0 tests=ALL_TRUSTED,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,URIBL_BLOCKED,
	URIBL_DBL_BLOCKED_OPENDNS autolearn=ham autolearn_force=no
	version=3.4.6
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org;
	s=default; t=1693206174;
	bh=1QKeRL2qNKewtmd0ztI2zUA2IGpHuOWAmwt4y/GeKtE=;
	h=From:To:Cc:Subject:Date;
	b=c3sNXkEns99pUlXQ03MPGHxrF+JhgQCbwfN1t7hZB9+rrKVItgOhsObp1pLWq7OUN
	 9IFrnFJLVLP0u95aYhVCHMSJC47cvGSq/sRpLu+7smacTbI735WAyc1ytpHsaX5PYc
	 rzpcSzamFXtQbpSqx9ZHDa8MwYpaEDMPD0MVhW9mNMhsqptgnzfSUsKgm2FbsoiGzr
	 vgM9h45WdSSzg2jv8mssZn0cr2xrhZybhVJWXKA4RTKM8ffTul3Uf+PPFHcK9PpUdY
	 2WFuL+e7puJvPqQU3DBjlnr7Wg29ZfZwYJZR1tx6vggIqareSOiKrK4BOTI0LRfTKr
	 6esS2mbqf15KQ==
Received: from localhost.localdomain (unknown [182.253.126.208])
	by gnuweeb.org (Postfix) with ESMTPSA id 4E42D24B1F3;
	Mon, 28 Aug 2023 14:02:49 +0700 (WIB)
From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
To: Willy Tarreau <w@1wt.eu>,
	=?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= <linux@weissschuh.net>
Cc: Ammar Faizi <ammarfaizi2@gnuweeb.org>,
	Zhangjin Wu <falcon@tinylab.org>,
	Nicholas Rosenberg <inori@vnlx.org>,
	Michael William Jonathan <moe@gnuweeb.org>,
	GNU/Weeb Mailing List <gwml@vger.gnuweeb.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 0/1] Fix a stack misalign bug on _start
Date: Mon, 28 Aug 2023 14:02:39 +0700
Message-Id: <20230828070240.1691921-1-ammarfaizi2@gnuweeb.org>
X-Mailer: git-send-email 2.34.1
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
List-Id: <gwml.vger.gnuweeb.org>

Hi Willy,

This is a v2 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 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 <ammarfaizi2@gnuweeb.org>
---

Ammar Faizi (1):
  tools/nolibc: i386: Fix a stack misalign bug on _start

 tools/include/nolibc/arch-i386.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)


base-commit: 6269320850097903b30be8f07a5c61d9f7592393
-- 
Ammar Faizi