From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755593AbbCaRBt (ORCPT ); Tue, 31 Mar 2015 13:01:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59730 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755549AbbCaRBg (ORCPT ); Tue, 31 Mar 2015 13:01:36 -0400 From: Denys Vlasenko To: Ingo Molnar Cc: Denys Vlasenko , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 9/9] x86/asm/entry/64: use local label to skip around sycall dispatch Date: Tue, 31 Mar 2015 19:00:11 +0200 Message-Id: <1427821211-25099-9-git-send-email-dvlasenk@redhat.com> In-Reply-To: <1427821211-25099-1-git-send-email-dvlasenk@redhat.com> References: <1427821211-25099-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Logically, we just want to jump around the "call *sys_call_table(,%rax,8)" if syscall number is too big, we do not specifically target "int_ret_from_sys_call" label. Use a local numeric label for this jump. This also makes code smaller because jumps to global labels are never translated to short jump insns by as. 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 --- 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 f49f973..e498542 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 */ /* -- 1.8.1.4