From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D876C433F5 for ; Thu, 2 Dec 2021 00:34:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354607AbhLBAhW (ORCPT ); Wed, 1 Dec 2021 19:37:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354479AbhLBAhN (ORCPT ); Wed, 1 Dec 2021 19:37:13 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07D13C06174A; Wed, 1 Dec 2021 16:33:52 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 55916CE1DC7; Thu, 2 Dec 2021 00:33:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76D5EC53FCF; Thu, 2 Dec 2021 00:33:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638405228; bh=5HUVxeq8HcizJpGoPFk7yffUPU/ibyovCpDh3FIdjs4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dU46npYrvQQCBefVbeLl7+zZ6YHB0fe/MJz+kwGCvBe5HmW/kRWFL1XC9S3IDjycF pt1CtenA7cNVtwYQKJ2hxxU0n23+oryS6tUVlCf14rBmnvgnXtJRA9yyNy7U7Q6U8D f+38hmva2f4wx6Uk+XQDbxZhsOd+uf1MbZYqu5nWZEVZIU53Y8GSkdvDlzrk1T/Epq CTrHLuNK/8Jxo4J/zEQZm9ugxsxSjup0YLJGDD42R8uSkN79xrx473Px/GhYgTANtK BFcVbP4SkndwvRbwoQuwasaXwbXNYJwGIYjOkAnJdj6aVp1fxl2qpI1gZ8kJXaxRj8 8q1VmqrGq+1kQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 3E02D5C1010; Wed, 1 Dec 2021 16:33:48 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Willy Tarreau , Ammar Faizi , stable@vger.kernel.org, "Paul E . McKenney" Subject: [PATCH rcu 3/6] tools/nolibc: fix incorrect truncation of exit code Date: Wed, 1 Dec 2021 16:33:43 -0800 Message-Id: <20211202003346.3129110-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20211202003322.GA3128775@paulmck-ThinkPad-P17-Gen-1> References: <20211202003322.GA3128775@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Willy Tarreau Ammar Faizi reported that our exit code handling is wrong. We truncate it to the lowest 8 bits but the syscall itself is expected to take a regular 32-bit signed integer, not an unsigned char. It's the kernel that later truncates it to the lowest 8 bits. The difference is visible in strace, where the program below used to show exit(255) instead of exit(-1): int main(void) { return -1; } This patch applies the fix to all archs. x86_64, i386, arm64, armv7 and mips were all tested and confirmed to work fine now. Risc-v was not tested but the change is trivial and exactly the same as for other archs. Reported-by: Ammar Faizi Cc: stable@vger.kernel.org Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney --- tools/include/nolibc/nolibc.h | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h index 7f300dc379e70..3e2c6f2ed587f 100644 --- a/tools/include/nolibc/nolibc.h +++ b/tools/include/nolibc/nolibc.h @@ -414,7 +414,7 @@ asm(".section .text\n" "xor %ebp, %ebp\n" // zero the stack frame "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned before call "call main\n" // main() returns the status code, we'll exit with it. - "movzb %al, %rdi\n" // retrieve exit code from 8 lower bits + "mov %eax, %edi\n" // retrieve exit code (32 bit) "mov $60, %rax\n" // NR_exit == 60 "syscall\n" // really exit "hlt\n" // ensure it does not return @@ -602,9 +602,9 @@ asm(".section .text\n" "push %ebx\n" // support both regparm and plain stack modes "push %eax\n" "call main\n" // main() returns the status code in %eax - "movzbl %al, %ebx\n" // retrieve exit code from lower 8 bits - "movl $1, %eax\n" // NR_exit == 1 - "int $0x80\n" // exit now + "mov %eax, %ebx\n" // retrieve exit code (32-bit int) + "movl $1, %eax\n" // NR_exit == 1 + "int $0x80\n" // exit now "hlt\n" // ensure it does not ""); @@ -788,7 +788,6 @@ asm(".section .text\n" "and %r3, %r1, $-8\n" // AAPCS : sp must be 8-byte aligned in the "mov %sp, %r3\n" // callee, an bl doesn't push (lr=pc) "bl main\n" // main() returns the status code, we'll exit with it. - "and %r0, %r0, $0xff\n" // limit exit code to 8 bits "movs r7, $1\n" // NR_exit == 1 "svc $0x00\n" ""); @@ -985,7 +984,6 @@ asm(".section .text\n" "add x2, x2, x1\n" // + argv "and sp, x1, -16\n" // sp must be 16-byte aligned in the callee "bl main\n" // main() returns the status code, we'll exit with it. - "and x0, x0, 0xff\n" // limit exit code to 8 bits "mov x8, 93\n" // NR_exit == 93 "svc #0\n" ""); @@ -1190,7 +1188,7 @@ asm(".section .text\n" "addiu $sp,$sp,-16\n" // the callee expects to save a0..a3 there! "jal main\n" // main() returns the status code, we'll exit with it. "nop\n" // delayed slot - "and $a0, $v0, 0xff\n" // limit exit code to 8 bits + "move $a0, $v0\n" // retrieve 32-bit exit code from v0 "li $v0, 4001\n" // NR_exit == 4001 "syscall\n" ".end __start\n" @@ -1388,7 +1386,6 @@ asm(".section .text\n" "add a2,a2,a1\n" // + argv "andi sp,a1,-16\n" // sp must be 16-byte aligned "call main\n" // main() returns the status code, we'll exit with it. - "andi a0, a0, 0xff\n" // limit exit code to 8 bits "li a7, 93\n" // NR_exit == 93 "ecall\n" ""); -- 2.31.1.189.g2e36527f23