From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id B30AA7DCEA for ; Thu, 6 Jun 2019 20:16:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727702AbfFFUQR (ORCPT ); Thu, 6 Jun 2019 16:16:17 -0400 Received: from mga17.intel.com ([192.55.52.151]:47825 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729410AbfFFUPf (ORCPT ); Thu, 6 Jun 2019 16:15:35 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Jun 2019 13:15:34 -0700 X-ExtLoop1: 1 Received: from yyu32-desk1.sc.intel.com ([143.183.136.147]) by orsmga002.jf.intel.com with ESMTP; 06 Jun 2019 13:15:33 -0700 From: Yu-cheng Yu To: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Cc: Yu-cheng Yu Subject: [PATCH v7 20/27] x86/cet/shstk: Introduce WRUSS instruction Date: Thu, 6 Jun 2019 13:06:39 -0700 Message-Id: <20190606200646.3951-21-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190606200646.3951-1-yu-cheng.yu@intel.com> References: <20190606200646.3951-1-yu-cheng.yu@intel.com> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org WRUSS is a new kernel-mode instruction but writes directly to user shadow stack memory. This is used to construct a return address on the shadow stack for the signal handler. This instruction can fault if the user shadow stack is invalid shadow stack memory. In that case, the kernel does a fixup. Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/special_insns.h | 32 ++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 0a3c4cab39db..99530ab0a077 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -250,6 +250,38 @@ static inline void clwb(volatile void *__p) : [pax] "a" (p)); } +#ifdef CONFIG_X86_INTEL_CET +#if defined(CONFIG_IA32_EMULATION) || defined(CONFIG_X86_X32) +static inline int write_user_shstk_32(unsigned long addr, unsigned int val) +{ + asm_volatile_goto("1: wrussd %1, (%0)\n" + _ASM_EXTABLE(1b, %l[fail]) + :: "r" (addr), "r" (val) + :: fail); + return 0; +fail: + return -EPERM; +} +#else +static inline int write_user_shstk_32(unsigned long addr, unsigned int val) +{ + WARN_ONCE(1, "%s used but not supported.\n", __func__); + return -EFAULT; +} +#endif + +static inline int write_user_shstk_64(unsigned long addr, unsigned long val) +{ + asm_volatile_goto("1: wrussq %1, (%0)\n" + _ASM_EXTABLE(1b, %l[fail]) + :: "r" (addr), "r" (val) + :: fail); + return 0; +fail: + return -EPERM; +} +#endif /* CONFIG_X86_INTEL_CET */ + #define nop() asm volatile ("nop") -- 2.17.1