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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 49A7EC433ED for ; Wed, 14 Apr 2021 08:39:11 +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 A47DE6023B for ; Wed, 14 Apr 2021 08:39:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A47DE6023B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37960 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lWb3F-00075J-K1 for qemu-devel@archiver.kernel.org; Wed, 14 Apr 2021 04:39:09 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56400) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWb2e-0006du-5B for qemu-devel@nongnu.org; Wed, 14 Apr 2021 04:38:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32426) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWb2b-0007sq-AS for qemu-devel@nongnu.org; Wed, 14 Apr 2021 04:38:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618389507; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yNJfulfk7xHSXhTp76n1+I9DIQ25YH4OUu8727qQjbc=; b=BXWYZGE+Dek4HiAcp5cVaqU7AJCu58CDytDsPt27Tc1tDq/JaOLBKeCT1MaUtH2xdEkfnv u70cbIVS5Loof4wJFKQu9a3l+O4qV3JHNizG+L5tC8j8CHjHSkl7pl1aLf1yk13ZjPhyIQ j3Mz3T0vR4NsBhJVJUpAqfbASq3xjm0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-195-zB2bzFKrPfKPgNvKGHsyNw-1; Wed, 14 Apr 2021 04:38:22 -0400 X-MC-Unique: zB2bzFKrPfKPgNvKGHsyNw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1796383DD28; Wed, 14 Apr 2021 08:38:21 +0000 (UTC) Received: from gondolin (ovpn-113-114.ams2.redhat.com [10.36.113.114]) by smtp.corp.redhat.com (Postfix) with ESMTP id C34C45D9D0; Wed, 14 Apr 2021 08:38:15 +0000 (UTC) Date: Wed, 14 Apr 2021 10:38:13 +0200 From: Cornelia Huck To: Ilya Leoshkevich Subject: Re: [PATCH v2] target/s390x: Fix translation exception on illegal instruction Message-ID: <20210414103813.2595508b.cohuck@redhat.com> In-Reply-To: <20210413165257.21426-1-iii@linux.ibm.com> References: <20210413165257.21426-1-iii@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: Thomas Huth , David Hildenbrand , Richard Henderson , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 13 Apr 2021 18:52:57 +0200 Ilya Leoshkevich wrote: > Hitting an uretprobe in a s390x TCG guest causes a SIGSEGV. What > happens is: > > * uretprobe maps a userspace page containing an invalid instruction. > * uretprobe replaces the target function's return address with the > address of that page. > * When tb_gen_code() is called on that page, tb->size ends up being 0 > (because the page starts with the invalid instruction), which causes > virt_page2 to point to the previous page. > * The previous page is not mapped, so this causes a spurious > translation exception. > > The bug is that tb->size must never be 0: even if there is an illegal > instruction, the instruction bytes that have been looked at must count > towards tb->size. So adjust s390x's translate_one() to act this way > for both illegal instructions and instructions that are known to > generate exceptions. > > Also add an assertion to tb_gen_code() in order to detect such > situations in future. > > Signed-off-by: Ilya Leoshkevich > --- > > v1: https://lists.nongnu.org/archive/html/qemu-devel/2021-04/msg02037.html > v1 -> v2: Fix target/s390x instead of trying to tolerate tb->size == 0 > in tb_gen_code(). > > accel/tcg/translate-all.c | 1 + > target/s390x/translate.c | 16 +++++++++++----- > 2 files changed, 12 insertions(+), 5 deletions(-) I assume this bug is not usually hit during normal usage, right? It's probably not release critical, so I'll line it up for 6.1 instead.