linux-kernel - [tip:x86/asm] perf/x86/64: Do report user_regs-> cx while we are in syscall, in get_regs

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Message-ID: <tip-5df71b396b2d1fdd9d9f5a33e2eda5dc27c5632d@git.kernel.org>
Date:	Sun, 12 Apr 2015 10:26:20 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	paulus@...ba.org, tglx@...utronix.de, acme@...nel.org,
	hpa@...or.com, linux-kernel@...r.kernel.org, dvlasenk@...hat.com,
	a.p.zijlstra@...llo.nl, jolsa@...hat.com, mingo@...nel.org
Subject: [tip:x86/asm] perf/x86/64: Do report user_regs->
 cx while we are in syscall, in get_regs_user()

Commit-ID:  5df71b396b2d1fdd9d9f5a33e2eda5dc27c5632d
Gitweb:     http://git.kernel.org/tip/5df71b396b2d1fdd9d9f5a33e2eda5dc27c5632d
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Fri, 10 Apr 2015 15:06:57 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 11 Apr 2015 13:08:53 +0200

perf/x86/64: Do report user_regs->cx while we are in syscall, in get_regs_user()

Yes, it is true that cx contains return address.
It's not clear why we trash it.
Stop doing that.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1428671219-29341-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/perf_regs.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index 7ab198a..a8d4e48 100644
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -177,8 +177,6 @@ void perf_get_regs_user(struct perf_regs *regs_user,
 		 * than just blindly copying user_regs.
 		 */
 		regs_user->abi = PERF_SAMPLE_REGS_ABI_64;
-		/* usually contains return address (same as ->ip) */
-		regs_user_copy->cx = -1;
 	} else {
 		/* We're probably in an interrupt or exception. */
 		regs_user->abi = user_64bit_mode(user_regs) ?
--
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