From owner-svn-src-all@freebsd.org Sat Oct 20 17:00:19 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 CAE0EFEC93A; Sat, 20 Oct 2018 17:00:19 +0000 (UTC) (envelope-from mjg@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 811B17B886; Sat, 20 Oct 2018 17:00:19 +0000 (UTC) (envelope-from mjg@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 7C02520BE9; Sat, 20 Oct 2018 17:00:19 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w9KH0JNi092434; Sat, 20 Oct 2018 17:00:19 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w9KH0JeG092433; Sat, 20 Oct 2018 17:00:19 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <201810201700.w9KH0JeG092433@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Sat, 20 Oct 2018 17:00:19 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r339449 - head/sys/amd64/include X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/amd64/include X-SVN-Commit-Revision: 339449 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: 2.1.29 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: Sat, 20 Oct 2018 17:00:20 -0000 Author: mjg Date: Sat Oct 20 17:00:18 2018 New Revision: 339449 URL: https://svnweb.freebsd.org/changeset/base/339449 Log: amd64: relax constraints in curthread and curpcb This makes the compiler less likely to reload the content from %gs. The 'P' modifier drops all synteax prefixes and 'n' constraint treats input as a known at compilation time immediate integer. Example reloading victim was spinlock_enter. Stolen from: OpenBSD Reported by: jtl Reviewed by: kib Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D17615 Modified: head/sys/amd64/include/pcpu.h Modified: head/sys/amd64/include/pcpu.h ============================================================================== --- head/sys/amd64/include/pcpu.h Sat Oct 20 16:59:43 2018 (r339448) +++ head/sys/amd64/include/pcpu.h Sat Oct 20 17:00:18 2018 (r339449) @@ -227,8 +227,7 @@ __curthread(void) { struct thread *td; - __asm("movq %%gs:%1,%0" : "=r" (td) - : "m" (*(char *)OFFSETOF_CURTHREAD)); + __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (OFFSETOF_CURTHREAD)); return (td); } #ifdef __clang__ @@ -242,7 +241,7 @@ __curpcb(void) { struct pcb *pcb; - __asm("movq %%gs:%1,%0" : "=r" (pcb) : "m" (*(char *)OFFSETOF_CURPCB)); + __asm("movq %%gs:%P1,%0" : "=r" (pcb) : "n" (OFFSETOF_CURPCB)); return (pcb); } #define curpcb (__curpcb())