linux-kernel - [tip:x86/asm] x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG

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Date:	Fri, 9 Oct 2015 06:15:04 -0700
From:	tip-bot for Andy Lutomirski <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	luto@...capital.net, peterz@...radead.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, dvlasenk@...hat.com,
	luto@...nel.org, bp@...en8.de, tglx@...utronix.de,
	torvalds@...ux-foundation.org, mingo@...nel.org, brgerst@...il.com
Subject: [tip:x86/asm] x86/entry:
  Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY

Commit-ID:  4aabd140f9cbe0361401a1368bac74df1010abf5
Gitweb:     http://git.kernel.org/tip/4aabd140f9cbe0361401a1368bac74df1010abf5
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Mon, 5 Oct 2015 17:48:21 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 9 Oct 2015 09:41:12 +0200

x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY

This shaves a few cycles off the slow paths.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Link: http://lkml.kernel.org/r/ce383fa9e129286ce6da6e00b53acd4c9fb5d06a.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 08a945d..778ca70 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -71,7 +71,8 @@ unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
 	unsigned long ret = 0;
 	u32 work;
 
-	BUG_ON(regs != task_pt_regs(current));
+	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
+		BUG_ON(regs != task_pt_regs(current));
 
 	work = ACCESS_ONCE(current_thread_info()->flags) &
 		_TIF_WORK_SYSCALL_ENTRY;
@@ -160,7 +161,8 @@ long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
 	u32 work = ACCESS_ONCE(current_thread_info()->flags) &
 		_TIF_WORK_SYSCALL_ENTRY;
 
-	BUG_ON(regs != task_pt_regs(current));
+	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
+		BUG_ON(regs != task_pt_regs(current));
 
 	/*
 	 * If we stepped into a sysenter/syscall insn, it trapped in
--
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