From patchwork Wed Mar 8 15:39:10 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Cooper X-Patchwork-Id: 9611461 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 490466046A for ; Wed, 8 Mar 2017 15:41:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 20384285F2 for ; Wed, 8 Mar 2017 15:41:29 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 14FB0285F5; Wed, 8 Mar 2017 15:41:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 751F2285F2 for ; Wed, 8 Mar 2017 15:41:28 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cldgL-00020c-Bn; Wed, 08 Mar 2017 15:39:17 +0000 Received: from mail6.bemta6.messagelabs.com ([193.109.254.103]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cldgJ-00020O-DG for xen-devel@lists.xen.org; Wed, 08 Mar 2017 15:39:15 +0000 Received: from [193.109.254.147] by server-4.bemta-6.messagelabs.com id A0/C7-25093-2A520C85; Wed, 08 Mar 2017 15:39:14 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrDLMWRWlGSWpSXmKPExsXitHRDpO4i1QM RBs/Oi1ss+biYxYHR4+ju30wBjFGsmXlJ+RUJrBk3NqxkLbjLU9H7ew5TA+MSzi5GTg4JAX+J s5u2sYPYbAL6ErtffGICsUUE1CVOd1xk7WLk4GAW8JM49MAXJCwsYCvxdP5zNhCbRUBF4ufRt YwgNq+Ap8SaK0+YIUbKSZw//hPMFhJQk7jWf4kdokZQ4uTMJywgNrOAhMTBFy+YJzByz0KSmo UktYCRaRWjRnFqUVlqka6RuV5SUWZ6RkluYmaOrqGBmV5uanFxYnpqTmJSsV5yfu4mRmAoMAD BDsbFawMPMUpyMCmJ8l67sz9CiC8pP6UyI7E4I76oNCe1+BCjDAeHkgSvv8qBCCHBotT01Iq0 zBxgUMKkJTh4lER4Z4GkeYsLEnOLM9MhUqcYFaXEeXlAEgIgiYzSPLg2WCRcYpSVEuZlBDpEi KcgtSg3swRV/hWjOAejkjBvDMgUnsy8Erjpr4AWMwEt1nbdC7K4JBEhJdXAuN1qX7ytaXOH0c cTNV2nxJ1rbaVT/9eGdZS3Pl8euaozmWfO1JvTvfg2q7YyvBZu/NWygK0x719AajSHptE3hq8 bdf+z/tvsmHfk4PbEPpajm65P+H1PV8x5gpCHy5a106erXPVZ2rnk/OuS444TwhqX5B2bkGXv ujE++/62CX0eTee2nZvyVomlOCPRUIu5qDgRAOphWw9/AgAA X-Env-Sender: prvs=23316ac9c=Andrew.Cooper3@citrix.com X-Msg-Ref: server-14.tower-27.messagelabs.com!1488987552!78314407!1 X-Originating-IP: [66.165.176.89] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni44OSA9PiAyMDMwMDc=\n, received_headers: No Received headers X-StarScan-Received: X-StarScan-Version: 9.2.3; banners=-,-,- X-VirusChecked: Checked Received: (qmail 1799 invoked from network); 8 Mar 2017 15:39:14 -0000 Received: from smtp.citrix.com (HELO SMTP.CITRIX.COM) (66.165.176.89) by server-14.tower-27.messagelabs.com with RC4-SHA encrypted SMTP; 8 Mar 2017 15:39:14 -0000 X-IronPort-AV: E=Sophos;i="5.36,264,1486425600"; d="scan'208";a="412369010" From: Andrew Cooper To: Xen-devel Date: Wed, 8 Mar 2017 15:39:10 +0000 Message-ID: <1488987550-21843-1-git-send-email-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.1.4 MIME-Version: 1.0 Cc: Andrew Cooper , Jan Beulich Subject: [Xen-devel] [PATCH] x86/emul: Poision the stubs with debug traps X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP ...rather than leaving fragments of old instructions in place. This reduces the chances of something going further-wrong (as the debug trap will be cause and terminate the guest) in a cascade-failure where we end up executing the instruction fragments. Before: (XEN) d2v0 exception 6 (ec=0000) in emulation stub (line 6239) (XEN) d2v0 stub: c4 e1 44 77 c3 80 d0 82 ff ff ff d1 90 ec 90 After: (XEN) d3v0 exception 6 (ec=0000) in emulation stub (line 6239) (XEN) d3v0 stub: c4 e1 44 77 c3 cc cc cc cc cc cc cc cc cc cc Signed-off-by: Andrew Cooper --- CC: Jan Beulich Semi-RFC: I really don't like (ab)use of memset, but can't think of a cleaner way of doing this. --- xen/arch/x86/x86_emulate.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/x86_emulate.c b/xen/arch/x86/x86_emulate.c index 51df340..cc334ca 100644 --- a/xen/arch/x86/x86_emulate.c +++ b/xen/arch/x86/x86_emulate.c @@ -30,8 +30,8 @@ BUILD_BUG_ON(STUB_BUF_SIZE / 2 < MAX_INST_LEN + 1); \ ASSERT(!(stb).ptr); \ (stb).addr = this_cpu(stubs.addr) + STUB_BUF_SIZE / 2; \ - ((stb).ptr = map_domain_page(_mfn(this_cpu(stubs.mfn)))) + \ - ((stb).addr & ~PAGE_MASK); \ + memset(((stb).ptr = map_domain_page(_mfn(this_cpu(stubs.mfn)))) + \ + ((stb).addr & ~PAGE_MASK), 0xcc, STUB_BUF_SIZE / 2); \ }) #define put_stub(stb) ({ \ if ( (stb).ptr ) \