linux-kernel - [PATCH 3/6] signal x86: Merge EFLAGS bit clearing into single statement

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Date:	Sun, 10 Mar 2013 19:41:08 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Jiri Olsa <jolsa@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Stephane Eranian <eranian@...gle.com>
Subject: [PATCH 3/6] signal x86: Merge EFLAGS bit clearing into single statement

Merging EFLAGS bit clearing into a single statement, to
ensure EFLAGS bits being cleared in single instruction.

Signed-off-by: Jiri Olsa <jolsa@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Cc: Stephane Eranian <eranian@...gle.com>
---
 arch/x86/kernel/signal.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index cb12fc9..cf91358 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -662,21 +662,17 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 	if (!failed) {
 		/*
 		 * Clear the direction flag as per the ABI for function entry.
-		 */
-		regs->flags &= ~X86_EFLAGS_DF;
-		/*
+		 *
 		 * Clear RF when entering the signal handler, because
 		 * it might disable possible debug exception from the
 		 * signal handler.
-		 */
-		regs->flags &= ~X86_EFLAGS_RF;
-		/*
+		 *
 		 * Clear TF when entering the signal handler, but
 		 * notify any tracer that was single-stepping it.
 		 * The tracer may want to single-step inside the
 		 * handler too.
 		 */
-		regs->flags &= ~X86_EFLAGS_TF;
+		regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 	}
 	signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
 }
-- 
1.7.11.7

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