From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=-5.1 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 Authentication-Results: gnuweeb.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: gnuweeb.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=u7EapoPG; dkim-atps=neutral Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=srs0=mts8=f2=paulmck-thinkpad-p17-gen-1.home=paulmck@kernel.org; receiver= Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gnuweeb.org (Postfix) with ESMTPS id BBF562492FA for ; Fri, 13 Oct 2023 02:32:36 +0700 (WIB) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id E68D861F40; Thu, 12 Oct 2023 19:32:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F03BC433C8; Thu, 12 Oct 2023 19:32:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697139155; bh=d8ayu7kl8vqNo7NKawNbDKeJKZ0xNLEf2Mmx5D5tlHA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u7EapoPG2ZvLutGfmEetupl7EiQpZfP69OEEGMailIC9EGAyMrT7kFssMCox0ZsS1 sJeYDQZGWF9GcId/l5GG7os0U6Z7ltz3h4Jum/C/frTSsxC+OQBIpxFALPrlMvWKeX EuYPNgezzcBYDKLgvBDC0UnUw5ixb2X0YST6d4ZpF5B/75zoDPFgI9YB/NCt1bBO5x cLsWPFgpqcaoNKbWp9kYHgWALyBIjb/8d5GkFV21/sJ4c8YkMETK9mEBY15XCkMNm8 75iJAv7iNSn95fAix87U9E1Uu2D17FpUlfdz86uC/o/pb4qHVQQBYIZw13ObqQvIap W7ZhD0X/ee/kA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 3D0E7CE096F; Thu, 12 Oct 2023 12:32:35 -0700 (PDT) From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: gwml@vger.gnuweeb.org, kernel-team@meta.com, w@lwt.eu, Ammar Faizi , Zhangjin Wu , Nicholas Rosenberg , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Alviro Iskandar Setiawan , Willy Tarreau Subject: [PATCH nolibc 01/19] tools/nolibc: i386: Fix a stack misalign bug on _start Date: Thu, 12 Oct 2023 12:32:15 -0700 Message-Id: <20231012193233.207857-1-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-Id: From: Ammar Faizi 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). The 'and $-16, %esp' aligns the %esp at a multiple of 16. Then 'push %eax' will subtract the %esp by 4; thus, it breaks the 16-byte alignment. Make sure the %esp is correctly aligned after the push by subtracting 12 before the push. Extra: Add 'add $12, %esp' before the 'and $-16, %esp' to avoid over-estimating for particular cases as suggested by Willy. A test program to validate the %esp alignment on _start can be found at: https://lore.kernel.org/lkml/ZOoindMFj1UKqo+s@biznet-home.integral.gnuweeb.org Cc: Zhangjin Wu Fixes: 2ab446336b17aad362c6decee29b4efd83a01979 ("tools/nolibc: i386: shrink _start with _start_c") Reported-by: Nicholas Rosenberg Acked-by: Thomas Weißschuh Signed-off-by: Ammar Faizi Reviewed-by: Alviro Iskandar Setiawan Signed-off-by: Willy Tarreau Signed-off-by: Thomas Weißschuh --- tools/include/nolibc/arch-i386.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h index 64415b9fac77..28c26a00a762 100644 --- a/tools/include/nolibc/arch-i386.h +++ b/tools/include/nolibc/arch-i386.h @@ -167,7 +167,9 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_ __asm__ volatile ( "xor %ebp, %ebp\n" /* zero the stack frame */ "mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */ - "and $-16, %esp\n" /* last pushed argument must be 16-byte aligned */ + "add $12, %esp\n" /* avoid over-estimating after the 'and' & 'sub' below */ + "and $-16, %esp\n" /* the %esp must be 16-byte aligned on 'call' */ + "sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */ "push %eax\n" /* push arg1 on stack to support plain stack modes too */ "call _start_c\n" /* transfer to c runtime */ "hlt\n" /* ensure it does not return */ -- 2.40.1