From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753932AbbCaMjR (ORCPT ); Tue, 31 Mar 2015 08:39:17 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57331 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753794AbbCaMi7 (ORCPT ); Tue, 31 Mar 2015 08:38:59 -0400 Date: Tue, 31 Mar 2015 05:38:29 -0700 From: tip-bot for Denys Vlasenko Message-ID: Cc: oleg@redhat.com, mingo@kernel.org, hpa@zytor.com, rostedt@goodmis.org, torvalds@linux-foundation.org, luto@kernel.org, bp@alien8.de, luto@amacapital.net, dvlasenk@redhat.com, tglx@linutronix.de, keescook@chromium.org, ast@plumgrid.com, wad@chromium.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org Reply-To: rostedt@goodmis.org, oleg@redhat.com, mingo@kernel.org, hpa@zytor.com, bp@alien8.de, luto@amacapital.net, torvalds@linux-foundation.org, luto@kernel.org, wad@chromium.org, fweisbec@gmail.com, ast@plumgrid.com, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, keescook@chromium.org, tglx@linutronix.de In-Reply-To: <63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org> References: <63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS to %ss Git-Commit-ID: e7d6eefaaa443130079d73cd05039d90b3db7a4a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: e7d6eefaaa443130079d73cd05039d90b3db7a4a Gitweb: http://git.kernel.org/tip/e7d6eefaaa443130079d73cd05039d90b3db7a4a Author: Denys Vlasenko AuthorDate: Fri, 27 Mar 2015 11:48:17 -0700 Committer: Ingo Molnar CommitDate: Tue, 31 Mar 2015 10:45:15 +0200 x86/vdso32/syscall.S: Do not load __USER32_DS to %ss This vDSO code only gets used by 64-bit kernels, not 32-bit ones. On 64-bit kernels, the data segment is the same for 32-bit and 64-bit userspace, and the SYSRET instruction loads %ss with its selector. So there's no need to repeat it by hand. Segment loads are somewhat expensive: tens of cycles. Signed-off-by: Denys Vlasenko [ Removed unnecessary comment. ] Signed-off-by: Andy Lutomirski Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/vdso/vdso32/syscall.S | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/vdso/vdso32/syscall.S b/arch/x86/vdso/vdso32/syscall.S index 5415b56..6b286bb 100644 --- a/arch/x86/vdso/vdso32/syscall.S +++ b/arch/x86/vdso/vdso32/syscall.S @@ -19,8 +19,6 @@ __kernel_vsyscall: .Lpush_ebp: movl %ecx, %ebp syscall - movl $__USER32_DS, %ecx - movl %ecx, %ss movl %ebp, %ecx popl %ebp .Lpop_ebp: