From patchwork Tue Sep 25 20:51:28 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 974739 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=vivier.eu Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 42KYJG2Rmpz9s8F for ; Wed, 26 Sep 2018 06:55:58 +1000 (AEST) Received: from localhost ([::1]:55231 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g4uN9-0002Hu-VE for incoming@patchwork.ozlabs.org; Tue, 25 Sep 2018 16:55:55 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53982) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g4uJu-0000C0-DQ for qemu-devel@nongnu.org; Tue, 25 Sep 2018 16:52:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g4uJq-0002WA-Km for qemu-devel@nongnu.org; Tue, 25 Sep 2018 16:52:34 -0400 Received: from mout.kundenserver.de ([212.227.126.131]:37051) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1g4uJq-0002VT-BD for qemu-devel@nongnu.org; Tue, 25 Sep 2018 16:52:30 -0400 Received: from localhost.localdomain ([78.238.229.36]) by mrelayeu.kundenserver.de (mreue009 [212.227.15.167]) with ESMTPSA (Nemesis) id 1MKsaz-1gLjfj0Pev-00LFL3; Tue, 25 Sep 2018 22:51:54 +0200 From: Laurent Vivier To: qemu-devel@nongnu.org Date: Tue, 25 Sep 2018 22:51:28 +0200 Message-Id: <20180925205129.25261-5-laurent@vivier.eu> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180925205129.25261-1-laurent@vivier.eu> References: <20180925205129.25261-1-laurent@vivier.eu> MIME-Version: 1.0 X-Provags-ID: V03:K1:9MGHT2GmUE15XMlbdJ2j7kQnWuxDmTu8hItxYkoQqrgkHHM64kQ A5uPO/+St52huehOXIvt/Uvoex6tsb+fh+HDa2GJj03D61X0zFjoTdpJOoUgTDfnX/cswJJ zMC32IVr8ZtL0XiVLwDHSNQwmPnReIQMjtoy/8TA3utE+Unji0qi9AMK4CViNRStk5FoJij d1STj3ZbADhpKmzUi3e+g== X-UI-Out-Filterresults: notjunk:1; V01:K0:uSt/lc53pkA=:M0MfvEgpetJNien6pUmLxp CscSnJJq9UcwxnkCKQhANk6ej5pPwYqx5n3kUuFcBp+5SKnemrZVTYDIDMbyMUClXGH5xS81N lzOF9fk8+Y629Rmgct9I97mMjTHvCsZeIt420p7wfDUoNLNLQ3buOn69erpxrqTDeGY20E6ig f0Ocn446NVyAEiucT8ZzZiprBgBkVJbGnZzn53b2PQhXd0FyF/f8vmlHpSNya2Pf62XSQQeAb r2N53Ybny7ur5onv7BJi60TNhKuJ/NUP8Huet9b6Z5e0jDmzGIAR2/WMzqwtyGu54wjEpI7cl ub3a74TzvDiGDnjoG2aVeYHsyRtEIl/ZrCzwgiMXmzMpGmSpTJKbNxn1vjSR63yhWbeLWTxOg gvAXZJKWhQKFi5+Y5j5HmekHYs5oL+FdExP3bqVBYNkoG6wAtkTXCBNTlWui8gOt173BrumS9 Ht5LM6vyGlid9dv+tlqpNEvF0fwRbnGbxeklzB6zuPMXncyJbJJ7LqR3ET8ATdHkGeWJfkZpI AdHfdwZ0smyXSFGWuniItbwCmQNi+LIhZZ8Pa17faF5ePhK34uZrefvIorW24v6RO7CMtWNKy bnU/C714dJKGXjXxNa9Qzk6ifzzeqGiugHR5Ir3dAW/PYZT5WaNBo6m6XV9OoXGw2ipG8Brcw PQdi0Csg/qhLg4/7Bs3BFAORZlyx6FL0n4CEb86KpW7uyx9P8dETjf57X/A6yztT3UXQEme0v 5gU+Jv7ATisqQlVj X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 212.227.126.131 Subject: [Qemu-devel] [PULL v2 4/5] linux-user: write(fd, NULL, 0) parity with linux's treatment of same X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tony Garnock-Jones , Riku Voipio , Laurent Vivier , Tony Garnock-Jones Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Tony Garnock-Jones Bring linux-user write(2) handling into line with linux for the case of a 0-byte write with a NULL buffer. Based on a patch originally written by Zhuowei Zhang. Addresses https://bugs.launchpad.net/qemu/+bug/1716292. >From Zhuowei Zhang's patch (https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg08073.html): Linux returns success for the special case of calling write with a zero-length NULL buffer: compiling and running int main() { ssize_t ret = write(STDOUT_FILENO, NULL, 0); fprintf(stderr, "write returned %ld\n", ret); return 0; } gives "write returned 0" when run directly, but "write returned -1" in QEMU. This commit checks for this situation and returns success if found. Subsequent discussion raised the following questions (and my answers): - Q. Should TARGET_NR_read pass through to safe_read in this situation too? A. I'm wary of changing unrelated code to the specific problem I'm addressing. TARGET_NR_read is already consistent with Linux for this case. - Q. Do pread64/pwrite64 need to be changed similarly? A. Experiment suggests not: both linux and linux-user yield -1 for NULL 0-length reads/writes. Signed-off-by: Tony Garnock-Jones Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Laurent Vivier Message-Id: <20180908182205.GB409@mornington.dcs.gla.ac.uk> Signed-off-by: Laurent Vivier --- linux-user/syscall.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 58fb967499..019af632df 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -6772,6 +6772,9 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1, } return ret; case TARGET_NR_write: + if (arg2 == 0 && arg3 == 0) { + return get_errno(safe_write(arg1, 0, 0)); + } if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1))) return -TARGET_EFAULT; if (fd_trans_target_to_host_data(arg1)) {