From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753180AbaHLPG0 (ORCPT ); Tue, 12 Aug 2014 11:06:26 -0400 Received: from mga11.intel.com ([192.55.52.93]:50663 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752687AbaHLPGZ (ORCPT ); Tue, 12 Aug 2014 11:06:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,849,1400050800"; d="scan'208";a="575603130" From: Adrian Hunter To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Jiri Olsa , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: [PATCH 4/4] perf tools: Prefer to use a cpu-wide event for probing CLOEXEC Date: Tue, 12 Aug 2014 18:04:31 +0300 Message-Id: <1407855871-15024-5-git-send-email-adrian.hunter@intel.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1407855871-15024-1-git-send-email-adrian.hunter@intel.com> References: <1407855871-15024-1-git-send-email-adrian.hunter@intel.com> Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When doing a system-wide trace with Intel PT, the jump label set up as a result of probing CLOEXEC gets reset while the trace is running. That causes an Intel PT decoding error because the object code (obtained from /proc/kcore) does not match the running code at that point. While we can't expect there never to be jump label changes, we can avoid cases that the perf tool itself creates. The problem is avoided by first trying a cpu-wide event (pid = -1) for probing the PERF_FLAG_FD_CLOEXEC flag and falling back to an event for the current process (pid = 0). Signed-off-by: Adrian Hunter --- tools/perf/util/cloexec.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c index 000047c..4945aa5 100644 --- a/tools/perf/util/cloexec.c +++ b/tools/perf/util/cloexec.c @@ -1,3 +1,4 @@ +#include #include "util.h" #include "../perf.h" #include "cloexec.h" @@ -15,10 +16,23 @@ static int perf_flag_probe(void) }; int fd; int err; + int cpu; + pid_t pid = -1; - /* check cloexec flag */ - fd = sys_perf_event_open(&attr, 0, -1, -1, - PERF_FLAG_FD_CLOEXEC); + cpu = sched_getcpu(); + if (cpu < 0) + cpu = 0; + + while (1) { + /* check cloexec flag */ + fd = sys_perf_event_open(&attr, pid, cpu, -1, + PERF_FLAG_FD_CLOEXEC); + if (fd < 0 && pid == -1 && errno == EACCES) { + pid = 0; + continue; + } + break; + } err = errno; if (fd >= 0) { @@ -31,7 +45,7 @@ static int perf_flag_probe(void) err, strerror(err)); /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */ - fd = sys_perf_event_open(&attr, 0, -1, -1, 0); + fd = sys_perf_event_open(&attr, pid, cpu, -1, 0); err = errno; if (WARN_ONCE(fd < 0 && err != EBUSY, -- 1.8.3.2