From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753390AbbDBM12 (ORCPT ); Thu, 2 Apr 2015 08:27:28 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60513 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751272AbbDBM1X (ORCPT ); Thu, 2 Apr 2015 08:27:23 -0400 Date: Thu, 2 Apr 2015 05:26:45 -0700 From: tip-bot for Denys Vlasenko Message-ID: Cc: dvlasenk@redhat.com, luto@amacapital.net, rostedt@goodmis.org, keescook@chromium.org, fweisbec@gmail.com, ast@plumgrid.com, tglx@linutronix.de, hpa@zytor.com, mingo@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, oleg@redhat.com, torvalds@linux-foundation.org, wad@chromium.org Reply-To: mingo@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, hpa@zytor.com, tglx@linutronix.de, fweisbec@gmail.com, ast@plumgrid.com, torvalds@linux-foundation.org, wad@chromium.org, oleg@redhat.com, luto@amacapital.net, rostedt@goodmis.org, dvlasenk@redhat.com, keescook@chromium.org In-Reply-To: <1427821211-25099-9-git-send-email-dvlasenk@redhat.com> References: <1427821211-25099-9-git-send-email-dvlasenk@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/asm/entry/64: Use local label to skip around sycall dispatch Git-Commit-ID: a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 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: a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 Gitweb: http://git.kernel.org/tip/a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 Author: Denys Vlasenko AuthorDate: Tue, 31 Mar 2015 19:00:11 +0200 Committer: Ingo Molnar CommitDate: Wed, 1 Apr 2015 13:17:39 +0200 x86/asm/entry/64: Use local label to skip around sycall dispatch Logically, we just want to jump around the following instruction and its prologue/epilogue: call *sys_call_table(,%rax,8) if the syscall number is too big - we do not specifically target the "int_ret_from_sys_call" label. Use a local, numerical label for this jump, for more clarity. This also makes the code smaller: -ffffffff8187756b: 0f 87 0f 00 00 00 ja ffffffff81877580 +ffffffff8187756b: 77 0f ja ffffffff8187757c because jumps to global labels are never translated to short jump instructions by GAS. Signed-off-by: Denys Vlasenko 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/1427821211-25099-9-git-send-email-dvlasenk@redhat.com [ Improved the changelog. ] Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bad285d..03c52e2 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -331,10 +331,11 @@ tracesys_phase2: andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif - ja int_ret_from_sys_call /* RAX(%rsp) is already set */ + ja 1f /* return -ENOSYS (already in pt_regs->ax) */ movq %r10,%rcx /* fixup for C */ call *sys_call_table(,%rax,8) movq %rax,RAX(%rsp) +1: /* Use IRET because user could have changed pt_regs->foo */ /*