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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 021A7C2D0DB for ; Tue, 28 Jan 2020 17:27:41 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C9CAC214AF for ; Tue, 28 Jan 2020 17:27:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C9CAC214AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=vivier.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34354 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iwUeJ-0002gJ-V8 for qemu-devel@archiver.kernel.org; Tue, 28 Jan 2020 12:27:39 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47240) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iwUdS-0002Ee-5c for qemu-devel@nongnu.org; Tue, 28 Jan 2020 12:26:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iwUdQ-0002Bz-Ru for qemu-devel@nongnu.org; Tue, 28 Jan 2020 12:26:45 -0500 Received: from mout.kundenserver.de ([212.227.126.131]:56757) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iwUdQ-00029d-JG for qemu-devel@nongnu.org; Tue, 28 Jan 2020 12:26:44 -0500 Received: from [192.168.100.1] ([78.238.229.36]) by mrelayeu.kundenserver.de (mreue011 [213.165.67.103]) with ESMTPSA (Nemesis) id 1M2w4S-1izmQP1gA0-003JNk; Tue, 28 Jan 2020 18:26:41 +0100 Subject: Re: [PATCH v2 0/5] linux-user: Implement x86_64 vsyscalls To: Richard Henderson , qemu-devel@nongnu.org References: <20200116194341.402-1-richard.henderson@linaro.org> From: Laurent Vivier Autocrypt: addr=laurent@vivier.eu; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200116194341.402-1-richard.henderson@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: fr Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:t/b5eXp4GIQwIa5yzCCWxzj7LRHxJVveo1vOhA2ZJk2UlZtO/x8 w+fB4FkgENiv6y/BJx4oT5IkqWx8vj291b+DVJW1z5hYaPGtk4pnt6IV4LMhY22gIcc6++z EQOFV2xVycyarSANMoOIULYmnaAyLZIaOLE7dozgogW5rF7wLwanxzgXJvm8fzaTCd3Xlxk 2Yyr1OYtFg+f8B0Ca9I6w== X-UI-Out-Filterresults: notjunk:1;V03:K0:ldJtppqNArs=:h95uLyA1vAV+B24tJPljJw +n9lTIz7NDTksqQ2JLwlEAoD6e71LqfiWSlEfc3AaPl5YRFMYQg4EYFK/eLO+7q9FsBTA6iPl amvK+DecfxPewFOcvQEdkJu3221lqyNJDU8o2NY5HzW9Xm9Qrx3nGvjoGRSI5EWLgcKWT6+lM p/gPH17K9caMd6YZgEFLFaPE65qE06N3aBDp3iKQbVpFW83tsXj+pZVD8B980TmmgIfVDEO5d d7iGEqU9UUaBJkLILZqjcZuk4lz6u0G8QI7d0VP2LqT1rtv+7eIUKR3sWvk9z2TIicXyt9C/3 2kMxzI3b+zqiHRcrYINYT/N7DroikW11N9WTXSFzr+lP/RDn8Wk3iik8Xba5e81ATmPnixfE+ ZiYABer6lMsQGOO0ao3NyrzTYSuahQA9zArx/Lvw9pOT04Q0jQoWR2lVLGNeRbEGM1a0jJ27G pqHxOyO55bCtxD9BXw/ojzxLhu8xLmDNDrrqn96pfuaDLQiTIhhpMBL1+QRAvhOXFe+DnLReI NqJc9SiO9smpXQj9Ft3V5JyXR1jOZeMjqGHlXkXRhlkTkUfY1D3DykjEieBlmZn0dICTYtisZ /fEJ7Xp4FkZ+34NCLRAEopwrTzabdWbSwOys+nv18UEtdItzRve6hd4iwTaGfjkKmpcD+h48a Xo5dwgW6RsVod4TQ5ic2vGtOMRC3CtUlEX50g2VZcnQ4klvWXM+4mkolpqqUuwDYtPbd/KSPX iisGMR5dQCLqUeE8wkQ1tJQXAZG8CkajGvhfHK5E2avMVtsjhciTed32o81RbXSzTcHMaPqxq HVh116WVlOxoVxrTQJqn176dekvl8ihL9rFJ20nJ3ErRDPFvIRBdI9NTes4ej+QL08UWOee X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 212.227.126.131 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alex.bennee@linaro.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Le 16/01/2020 à 20:43, Richard Henderson a écrit : > Changes since v2: > > * Add /proc/self/maps line > > I'm not sure this is really necessary. The linux kernel > self-test checks for it, and modifies the set of tests that > it runs based on it. But otherwise I think it's unused. > > * Fix errors in base gettimeofday syscall > > This is also checked by test_vsyscall, as noticed by AJB. > Hi Richard, do you plan to send a v3? Thanks, Laurent > r~ > > > Original blurb: > > The x86_64 abi has a legacy vsyscall page. The kernel folk > have been trying to deprecate this since at least v3.1, but > > (1) We don't implement the vdso that replaces vsyscalls, > (2) As of v5.5, the vsyscall page is still enabled by default. > > This lack is affecting Peter's linux-user testing. > > The dependency is not obvious because Peter is running the tests > on x86_64, so the host is providing a vsyscall page to qemu. > > Because of how user-only memory operations are handled, with no > validation of guest vs host pages, so long as qemu chooses to > run with guest_base == 0, the guest may Just So Happen to read > the host's vsyscall page. > > Complicating this, new OS releases may use a kernel configured > with CONFIG_LEGACY_VSYSCALL_XONLY=y, which means the the vsyscall > page cannot be read, only executed. Which means that the guest > then cannot read the host vsyscall page during translation and > will SIGSEGV. > > Exactly which of these many variables is affecting Peter's testing > with Ubuntu 18.04 of my TCG merge, I'm not exactly sure. I suspect > that it is the change to drop the textseg_addr adjustment to user-only > static binaries. IIRC bionic does not support -static-pie, which is > the preferred replacement. This could mean that the host and guest > binaries overlap, which leads to guest_base != 0. > > I vaguely remember someone (Paolo?) implementing something like > this many years ago, but clearly it never got merged. > > In any case, this emulation has been missing for too long. > > > Richard Henderson (5): > target/i386: Renumber EXCP_SYSCALL > linux-user/i386: Split out gen_signal > linux-user/i386: Emulate x86_64 vsyscalls > linux-user: Add x86_64 vsyscall page to /proc/self/maps > linux-user: Flush out implementation of gettimeofday > > target/i386/cpu.h | 6 +- > linux-user/i386/cpu_loop.c | 198 ++++++++++++++++++++++++++----------- > linux-user/syscall.c | 36 ++++++- > target/i386/translate.c | 16 ++- > 4 files changed, 190 insertions(+), 66 deletions(-) >