From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932610AbbBZWmD (ORCPT ); Thu, 26 Feb 2015 17:42:03 -0500 Received: from mail-pd0-f178.google.com ([209.85.192.178]:36907 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932542AbbBZWlh (ORCPT ); Thu, 26 Feb 2015 17:41:37 -0500 From: Andy Lutomirski To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Borislav Petkov , Oleg Nesterov , Denys Vlasenko , Linus Torvalds , Steven Rostedt , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook Subject: [PATCH 15/16] x86: entry.S: simplify optimistic SYSRET Date: Thu, 26 Feb 2015 14:40:38 -0800 Message-Id: <1aef69b346a6db0d99cdfb0f5ba83e8c985e27d7.1424989793.git.luto@amacapital.net> X-Mailer: git-send-email 2.1.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Denys Vlasenko Avoid redundant load of %r11 (it is already loaded a few instructions before). Do not needlessly increment %rsp - we are going to return to userspace via SYSRET, this insn doesn't use stack for return. Changes since v1: added a comment Signed-off-by: Denys Vlasenko CC: Linus Torvalds CC: Steven Rostedt CC: Ingo Molnar CC: Borislav Petkov CC: "H. Peter Anvin" CC: Andy Lutomirski CC: Oleg Nesterov CC: Frederic Weisbecker CC: Alexei Starovoitov CC: Will Drewry CC: Kees Cook CC: x86@kernel.org CC: linux-kernel@vger.kernel.org Message-Id: <1424824222-10856-1-git-send-email-dvlasenk@redhat.com> Signed-off-by: Andy Lutomirski --- arch/x86/include/asm/calling.h | 3 +++ arch/x86/kernel/entry_64.S | 6 +++--- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/calling.h b/arch/x86/include/asm/calling.h index 337423590b08..f1a962ff7ddf 100644 --- a/arch/x86/include/asm/calling.h +++ b/arch/x86/include/asm/calling.h @@ -176,6 +176,9 @@ For 32-bit we have the following conventions - kernel is built with .macro RESTORE_C_REGS_EXCEPT_RCX RESTORE_C_REGS_HELPER 1,0,1,1,1 .endm + .macro RESTORE_C_REGS_EXCEPT_R11 + RESTORE_C_REGS_HELPER 1,1,0,1,1 + .endm .macro RESTORE_RSI_RDI RESTORE_C_REGS_HELPER 0,0,0,0,0 .endm diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 6fcf5d1e36c9..4670fcdb5150 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -757,9 +757,9 @@ retint_swapgs: /* return to user-space */ */ irq_return_via_sysret: CFI_REMEMBER_STATE - RESTORE_C_REGS - REMOVE_PT_GPREGS_FROM_STACK 8 - movq (RSP-RIP)(%rsp),%rsp + /* r11 is already restored (see code above) */ + RESTORE_C_REGS_EXCEPT_R11 + movq RSP(%rsp),%rsp USERGS_SYSRET64 CFI_RESTORE_STATE -- 2.1.0