From nobody Fri May 3 14:25:21 2024 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=suse.com ARC-Seal: i=1; a=rsa-sha256; t=1611678689; cv=none; d=zohomail.com; s=zohoarc; b=BwHujGLqUTxXAjNJAWt/p9A6CBMMIbg3PUSHSM8QZ0FXoCwLYJr1zZ38XkaLOyod0s2d1YwbREjpXw3X2Twf1DSZ7iKmYxpqV3jcgBtHi/O94GUqoQwxMFOfZ/o7+IvbwAUQyjj0kYDNclYP2QPlgBfsRdqFHPulrIkEjUFXb+w= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1611678689; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:To; bh=glkROfFJIVPSt4bFvVUxxsyDy6gtPVilRE3ZV2UKq8U=; b=FiV3wnSQD0dLM7fhPV5vWxOIsmUpWZ6MfLtym+M9psieLWUCs3An95MJ4DLdAdvyQgI8w2xYQ9ui3qh78oOK8bQWA36OtqM2zTH28HWlAJ4e8KM9Q/LlekcB3BupjAw/RxXoqTJOkv0T8ZRE3TSyg48f6K0IzjuLuseZgrFeilY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) header.from= Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1611678689684356.52435180284226; Tue, 26 Jan 2021 08:31:29 -0800 (PST) Received: from list by lists.xenproject.org with outflank-mailman.75286.135507 (Exim 4.92) (envelope-from ) id 1l4RFD-0005OD-Dc; Tue, 26 Jan 2021 16:31:07 +0000 Received: by outflank-mailman (output) from mailman id 75286.135507; Tue, 26 Jan 2021 16:31:07 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l4RFD-0005O6-9f; Tue, 26 Jan 2021 16:31:07 +0000 Received: by outflank-mailman (input) for mailman id 75286; Tue, 26 Jan 2021 16:31:06 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l4RFC-0005O1-4r for xen-devel@lists.xenproject.org; Tue, 26 Jan 2021 16:31:06 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 7afe156b-443b-4a4e-aaf7-218be25d5f7b; Tue, 26 Jan 2021 16:31:05 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7459FB71F; Tue, 26 Jan 2021 16:31:04 +0000 (UTC) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 7afe156b-443b-4a4e-aaf7-218be25d5f7b X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611678664; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=glkROfFJIVPSt4bFvVUxxsyDy6gtPVilRE3ZV2UKq8U=; b=l49GIzjuOMZndfRKLO/hD79+E8Kr6EGdUVQJT+TNVv1/9GxeTI0kiS0T5WnJsc77ZS2RDG mg2HTUmoQjhPFSsQT/N+eU/mmWoasFqy986lYoteYTQex9yvE3oZPhnnIPTQk5rP7Xsi+r S7Q2EI28q0XGEoQpA33xTNldaRm9ZMs= To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= From: Jan Beulich Subject: [PATCH] x86/PV: use 64-bit subtract to adjust guest RIP upon missing SYSCALL callbacks Message-ID: <29c38fa2-8337-0566-2053-ddcaf88ed01d@suse.com> Date: Tue, 26 Jan 2021 17:31:05 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) Content-Type: text/plain; charset="utf-8" When discussing the shrunk down version of the commit in question it was said (in reply to my conditional choosing of the width): "However, the 32bit case isn't actually interesting here. A guest can't execute a SYSCALL instruction on/across the 4G->0 boundary because the M2P is mapped NX up to the 4G boundary, so we can never reach this point with %eip < 2. Therefore, the 64bit-only form is the appropriate one to use, which solves any question of cleverness, or potential decode stalls it causes." Fixes: ca6fcf4321b3 ("x86/pv: Inject #UD for missing SYSCALL callbacks") Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -42,7 +42,7 @@ ENTRY(switch_to_kernel) UNLIKELY_START(z, syscall_no_callback) /* TB_eip =3D=3D 0 =3D> #UD */ mov VCPU_trap_ctxt(%rbx), %rdi movl $X86_EXC_UD, UREGS_entry_vector(%rsp) - subl $2, UREGS_rip(%rsp) + subq $2, UREGS_rip(%rsp) mov X86_EXC_UD * TRAPINFO_sizeof + TRAPINFO_eip(%rdi), %rax testb $4, X86_EXC_UD * TRAPINFO_sizeof + TRAPINFO_flags(%rdi) setnz %cl