From owner-svn-src-all@freebsd.org Tue Mar 20 17:47:30 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 77C74F6088A; Tue, 20 Mar 2018 17:47:30 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 266D57EE1E; Tue, 20 Mar 2018 17:47:30 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 1D3ED1FF2A; Tue, 20 Mar 2018 17:47:30 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w2KHlTWh055853; Tue, 20 Mar 2018 17:47:29 GMT (envelope-from kib@FreeBSD.org) Received: (from kib@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w2KHlTQl055852; Tue, 20 Mar 2018 17:47:29 GMT (envelope-from kib@FreeBSD.org) Message-Id: <201803201747.w2KHlTQl055852@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: kib set sender to kib@FreeBSD.org using -f From: Konstantin Belousov Date: Tue, 20 Mar 2018 17:47:29 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r331253 - head/sys/amd64/amd64 X-SVN-Group: head X-SVN-Commit-Author: kib X-SVN-Commit-Paths: head/sys/amd64/amd64 X-SVN-Commit-Revision: 331253 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Mar 2018 17:47:30 -0000 Author: kib Date: Tue Mar 20 17:47:29 2018 New Revision: 331253 URL: https://svnweb.freebsd.org/changeset/base/331253 Log: Disable write protection around patching of XSAVE instruction in the context switch code. Some BIOSes give control to the OS with CR0.WP already set, making the kernel text read-only before cpu_startup(). Reported by: Peter Lei Reviewed by: jtl Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D14768 Modified: head/sys/amd64/amd64/fpu.c Modified: head/sys/amd64/amd64/fpu.c ============================================================================== --- head/sys/amd64/amd64/fpu.c Tue Mar 20 17:43:50 2018 (r331252) +++ head/sys/amd64/amd64/fpu.c Tue Mar 20 17:47:29 2018 (r331253) @@ -205,6 +205,7 @@ fpuinit_bsp1(void) { u_int cp[4]; uint64_t xsave_mask_user; + bool old_wp; if ((cpu_feature2 & CPUID2_XSAVE) != 0) { use_xsave = 1; @@ -233,8 +234,14 @@ fpuinit_bsp1(void) * Patch the XSAVE instruction in the cpu_switch code * to XSAVEOPT. We assume that XSAVE encoding used * REX byte, and set the bit 4 of the r/m byte. + * + * It seems that some BIOSes give control to the OS + * with CR0.WP already set, making the kernel text + * read-only before cpu_startup(). */ + old_wp = disable_wp(); ctx_switch_xsave[3] |= 0x10; + restore_wp(old_wp); } }