From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id ACA0A7D927 for ; Thu, 11 Oct 2018 15:22:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728872AbeJKWtX (ORCPT ); Thu, 11 Oct 2018 18:49:23 -0400 Received: from mga18.intel.com ([134.134.136.126]:64714 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728528AbeJKWtW (ORCPT ); Thu, 11 Oct 2018 18:49:22 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Oct 2018 08:21:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,368,1534834800"; d="scan'208";a="77271624" Received: from 2b52.sc.intel.com ([143.183.136.147]) by fmsmga007.fm.intel.com with ESMTP; 11 Oct 2018 08:21:44 -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 , 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 Cc: Yu-cheng Yu Subject: [PATCH v5 03/11] x86/cet/ibt: Add IBT legacy code bitmap allocation function Date: Thu, 11 Oct 2018 08:16:46 -0700 Message-Id: <20181011151654.27221-4-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181011151654.27221-1-yu-cheng.yu@intel.com> References: <20181011151654.27221-1-yu-cheng.yu@intel.com> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Indirect branch tracking provides an optional legacy code bitmap that indicates locations of non-IBT compatible code. When set, each bit in the bitmap represents a page in the linear address is legacy code. We allocate the bitmap only when the application requests it. Most applications do not need the bitmap. Signed-off-by: Yu-cheng Yu --- arch/x86/kernel/cet.c | 47 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c index 40c4c08e5e31..77ae4eaa9dea 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -21,6 +21,7 @@ #include #include #include +#include static int set_shstk_ptr(unsigned long addr) { @@ -327,3 +328,49 @@ void cet_disable_ibt(void) wrmsrl(MSR_IA32_U_CET, r); current->thread.cet.ibt_enabled = 0; } + +int cet_setup_ibt_bitmap(void) +{ + u64 r; + unsigned long bitmap; + unsigned long size; + + if (!cpu_feature_enabled(X86_FEATURE_IBT)) + return -EOPNOTSUPP; + + if (!current->thread.cet.ibt_bitmap_addr) { + /* + * Calculate size and put in thread header. + * may_expand_vm() needs this information. + */ + size = in_compat_syscall() ? task_size_32bit() : task_size_64bit(1); + size = size / PAGE_SIZE / BITS_PER_BYTE; + current->thread.cet.ibt_bitmap_size = size; + bitmap = do_mmap_locked(0, size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, + VM_DONTDUMP); + + if ((bitmap >= TASK_SIZE) || (bitmap < size)) { + current->thread.cet.ibt_bitmap_size = 0; + return -ENOMEM; + } + + current->thread.cet.ibt_bitmap_addr = bitmap; + + /* + * Lower bits of MSR_IA32_CET_LEG_IW_EN are for IBT + * settings. Clear lower bits even bitmap is already + * page-aligned. + */ + bitmap &= PAGE_MASK; + + /* + * Turn on IBT legacy bitmap. + */ + rdmsrl(MSR_IA32_U_CET, r); + r |= (MSR_IA32_CET_LEG_IW_EN | bitmap); + wrmsrl(MSR_IA32_U_CET, r); + } + + return 0; +} -- 2.17.1