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=-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=1693357360; bh=K/VHveZ7OtIcrGkkd/zHQRJC+BT4E8xTNNy3oVBaQgw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oxruvBn7tPDzRVVRKRx5oR15fc8TyYjrhC0MGx/E4HNA/2n97dhLtmuZpzAYcKz8x 74wrb/g8B0xhH5lxjTbB3lOoPue4Y74QJByVRz1aU6hdrHE5MYr5+rV4atOirziV+x sh9AC4pvK99OHyme8BnN7sMPkJq3D/eLeZT8hQSyUvzH9EVGru48W1UCKaO2l5KhWH eK56DzEnAyEfQgeIIvZmGhL2VAoZi59V+/NSCkmfVldyqHWFt1bQXya9ZkBSimdQ95 lhug/QubAZPign0vFN9JYwKpmvX/jVrZ9SzfjwLbMGnb/zYV5vrtdH8elvIDpQfJ6u E1V9X25HKFJhA== Received: from localhost.localdomain (unknown [182.253.126.208]) by gnuweeb.org (Postfix) with ESMTPSA id 19BC624B29A; Wed, 30 Aug 2023 08:02:36 +0700 (WIB) From: Ammar Faizi To: Willy Tarreau , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Cc: Ammar Faizi , Zhangjin Wu , Nicholas Rosenberg , Michael William Jonathan , GNU/Weeb Mailing List , Linux Kernel Mailing List Subject: [PATCH v3 1/1] tools/nolibc: i386: Fix a stack misalign bug on _start Date: Wed, 30 Aug 2023 08:02:23 +0700 Message-Id: <20230830010223.1875339-2-ammarfaizi2@gnuweeb.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230830010223.1875339-1-ammarfaizi2@gnuweeb.org> References: <20230830010223.1875339-1-ammarfaizi2@gnuweeb.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-Id: 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 --- 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 64415b9fac77f996..28c26a00a7625f55 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 */ -- Ammar Faizi