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[tip:x86/asm] x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY

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Commit-ID:  4aabd140f9cbe0361401a1368bac74df1010abf5
Gitweb:     http://git.kernel.org/tip/4aabd140f9cbe0361401a1368bac74df1010abf5
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Mon, 5 Oct 2015 17:48:21 -0700
Committer:  Ingo Molnar <mingo@kernel.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@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/ce383fa9e129286ce6da6e00b53acd4c9fb5d06a.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.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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[PATCH v2 33/36] x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY Andy Lutomirski <luto@kernel.org> - 2015-10-06 03:00 +0200
  [tip:x86/asm] x86/entry:   Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2015-10-09 15:20 +0200

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