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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT 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 61BFCC63699 for ; Mon, 16 Nov 2020 14:47:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F37E22409 for ; Mon, 16 Nov 2020 14:47:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="M5uBvang" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730423AbgKPOqw (ORCPT ); Mon, 16 Nov 2020 09:46:52 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:55562 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730412AbgKPOqu (ORCPT ); Mon, 16 Nov 2020 09:46:50 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AGEjaEf034272; Mon, 16 Nov 2020 14:46:29 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2020-01-29; bh=9YYO7nmDyOzMKDU/wzV07C/qil2glDwx4yeF2k9SnjQ=; b=M5uBvang34/8Gu1eUwJiTgEL1nqFcM0XshfyafK1RoZhFL6t8SL/suz6KOIZRgLEfalY YzyLOOQTOzHcTtmrG3kooWoXyLbUKb0482lU4MLb8MvubMs80KqUBh0VHLxZAM+Drfrl dbAgf/PuA1iIoK6ZidcDK7BFYwN+Chu2E5anJ+RGVLPr952yewcn53ZnSocWqEozfLwT sS5VRAUN+iCKrtoEeK3Yt1d0N8weUTTgpEN1FQS/pyh8QEiw25YlYbOQXUIJRDvB2mUh o6xBF7GrkH2wxbur/iBKPBQC93DpO+yZ+WxQHxtNXE/wWjSyzHT5reybaDdhwoXfv352 2Q== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2120.oracle.com with ESMTP id 34t7vmward-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 16 Nov 2020 14:46:29 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AGEjDNF164495; Mon, 16 Nov 2020 14:46:28 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 34umcww38t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 16 Nov 2020 14:46:28 +0000 Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 0AGEkPi1005628; Mon, 16 Nov 2020 14:46:25 GMT Received: from localhost.localdomain (/92.157.91.83) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 16 Nov 2020 06:46:25 -0800 From: Alexandre Chartre To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, jroedel@suse.de Cc: konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com, rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com, kuzuno@gmail.com, alexandre.chartre@oracle.com Subject: [RFC][PATCH v2 07/21] x86/entry: Fill ESPFIX stack using C code Date: Mon, 16 Nov 2020 15:47:43 +0100 Message-Id: <20201116144757.1920077-8-alexandre.chartre@oracle.com> X-Mailer: git-send-email 2.18.4 In-Reply-To: <20201116144757.1920077-1-alexandre.chartre@oracle.com> References: <20201116144757.1920077-1-alexandre.chartre@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9806 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011160090 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9806 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 malwarescore=0 bulkscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 mlxscore=0 priorityscore=1501 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011160090 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ESPFIX stack is filled using assembly code. Move this code to a C function so that it is easier to read and modify. Signed-off-by: Alexandre Chartre --- arch/x86/entry/entry_64.S | 62 ++++++++++++++++++------------------- arch/x86/kernel/espfix_64.c | 41 ++++++++++++++++++++++++ 2 files changed, 72 insertions(+), 31 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 73e9cd47dc83..6e0b5b010e0b 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -684,8 +684,10 @@ native_irq_return_ldt: * long (see ESPFIX_STACK_SIZE). espfix_waddr points to the bottom * of the ESPFIX stack. * - * We clobber RAX and RDI in this code. We stash RDI on the - * normal stack and RAX on the ESPFIX stack. + * We call into C code to fill the ESPFIX stack. We stash registers + * that the C function can clobber on the normal stack. The user RAX + * is stashed first so that it is adjacent to the iret frame which + * will be copied to the ESPFIX stack. * * The ESPFIX stack layout we set up looks like this: * @@ -699,39 +701,37 @@ native_irq_return_ldt: * --- bottom of ESPFIX stack --- */ - pushq %rdi /* Stash user RDI */ - SWAPGS /* to kernel GS */ - SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi /* to kernel CR3 */ - - movq PER_CPU_VAR(espfix_waddr), %rdi - movq %rax, (0*8)(%rdi) /* user RAX */ - movq (1*8)(%rsp), %rax /* user RIP */ - movq %rax, (1*8)(%rdi) - movq (2*8)(%rsp), %rax /* user CS */ - movq %rax, (2*8)(%rdi) - movq (3*8)(%rsp), %rax /* user RFLAGS */ - movq %rax, (3*8)(%rdi) - movq (5*8)(%rsp), %rax /* user SS */ - movq %rax, (5*8)(%rdi) - movq (4*8)(%rsp), %rax /* user RSP */ - movq %rax, (4*8)(%rdi) - /* Now RAX == RSP. */ - - andl $0xffff0000, %eax /* RAX = (RSP & 0xffff0000) */ + /* save registers */ + pushq %rax + pushq %rdi + pushq %rsi + pushq %rdx + pushq %rcx + pushq %r8 + pushq %r9 + pushq %r10 + pushq %r11 /* - * espfix_stack[31:16] == 0. The page tables are set up such that - * (espfix_stack | (X & 0xffff0000)) points to a read-only alias of - * espfix_waddr for any X. That is, there are 65536 RO aliases of - * the same page. Set up RSP so that RSP[31:16] contains the - * respective 16 bits of the /userspace/ RSP and RSP nonetheless - * still points to an RO alias of the ESPFIX stack. + * fill_espfix_stack will copy the iret+rax frame to the ESPFIX + * stack and return with RAX containing a pointer to the ESPFIX + * stack. */ - orq PER_CPU_VAR(espfix_stack), %rax + leaq 8*8(%rsp), %rdi /* points to the iret+rax frame */ + call fill_espfix_stack - SWITCH_TO_USER_CR3_STACK scratch_reg=%rdi - SWAPGS /* to user GS */ - popq %rdi /* Restore user RDI */ + /* + * RAX contains a pointer to the ESPFIX, so restore registers but + * RAX. RAX will be restored from the ESPFIX stack. + */ + popq %r11 + popq %r10 + popq %r9 + popq %r8 + popq %rcx + popq %rdx + popq %rsi + popq %rdi movq %rax, %rsp UNWIND_HINT_IRET_REGS offset=8 diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index 4fe7af58cfe1..ff4b5160b39c 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -33,6 +33,7 @@ #include #include #include +#include /* * Note: we only need 6*8 = 48 bytes for the espfix stack, but round @@ -205,3 +206,43 @@ void init_espfix_ap(int cpu) per_cpu(espfix_waddr, cpu) = (unsigned long)stack_page + (addr & ~PAGE_MASK); } + +/* + * iret frame with an additional user_rax register. + */ +struct iret_rax_frame { + unsigned long user_rax; + unsigned long rip; + unsigned long cs; + unsigned long rflags; + unsigned long rsp; + unsigned long ss; +}; + +noinstr unsigned long fill_espfix_stack(struct iret_rax_frame *frame) +{ + struct iret_rax_frame *espfix_frame; + unsigned long rsp; + + native_swapgs(); + user_pagetable_exit(); + + espfix_frame = (struct iret_rax_frame *)this_cpu_read(espfix_waddr); + *espfix_frame = *frame; + + /* + * espfix_stack[31:16] == 0. The page tables are set up such that + * (espfix_stack | (X & 0xffff0000)) points to a read-only alias of + * espfix_waddr for any X. That is, there are 65536 RO aliases of + * the same page. Set up RSP so that RSP[31:16] contains the + * respective 16 bits of the /userspace/ RSP and RSP nonetheless + * still points to an RO alias of the ESPFIX stack. + */ + rsp = ((unsigned long)espfix_frame) & 0xffff0000; + rsp |= this_cpu_read(espfix_stack); + + user_pagetable_enter(); + native_swapgs(); + + return rsp; +} -- 2.18.4