linux-kernel - [tip:perf/urgent] perf tools: Fix probing for PERF_FLAG_FD

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Message-ID: <tip-48536c9195ae8c2a00fd8f400bac72ab613feaab@git.kernel.org>
Date:	Sun, 1 Mar 2015 08:50:19 -0800
From:	tip-bot for Adrian Hunter <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, david.ahern@...cle.com,
	adrian.hunter@...el.com, hpa@...or.com, acme@...hat.com,
	linux-kernel@...r.kernel.org, dsahern@...il.com, mingo@...nel.org
Subject: [tip:perf/urgent] perf tools:
  Fix probing for PERF_FLAG_FD_CLOEXEC flag

Commit-ID:  48536c9195ae8c2a00fd8f400bac72ab613feaab
Gitweb:     http://git.kernel.org/tip/48536c9195ae8c2a00fd8f400bac72ab613feaab
Author:     Adrian Hunter <adrian.hunter@...el.com>
AuthorDate: Tue, 24 Feb 2015 13:20:59 +0200
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Wed, 25 Feb 2015 16:40:13 -0300

perf tools: Fix probing for PERF_FLAG_FD_CLOEXEC flag

Commit f6edb53c4993ffe92ce521fb449d1c146cea6ec2 converted the probe to
a CPU wide event first (pid == -1). For kernels that do not support
the PERF_FLAG_FD_CLOEXEC flag the probe fails with EINVAL. Since this
errno is not handled pid is not reset to 0 and the subsequent use of
pid = -1 as an argument brings in an additional failure path if
perf_event_paranoid > 0:

$ perf record -- sleep 1
perf_event_open(..., 0) failed unexpectedly with error 13 (Permission denied)
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.007 MB /tmp/perf.data (11 samples) ]

Also, ensure the fd of the confirmation check is closed and comment why
pid = -1 is used.

Needs to go to 3.18 stable tree as well.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Based-on-patch-by: David Ahern <david.ahern@...cle.com>
Acked-by: David Ahern <david.ahern@...cle.com>
Cc: David Ahern <dsahern@...il.com>
Link: http://lkml.kernel.org/r/54EC610C.8000403@intel.com
Cc: stable@...r.kernel.org  # v3.18+
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/cloexec.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 47b78b3..6da965b 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -25,6 +25,10 @@ static int perf_flag_probe(void)
 	if (cpu < 0)
 		cpu = 0;
 
+	/*
+	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
+	 * changes.
+	 */
 	while (1) {
 		/* check cloexec flag */
 		fd = sys_perf_event_open(&attr, pid, cpu, -1,
@@ -47,16 +51,24 @@ static int perf_flag_probe(void)
 		  err, strerror_r(err, sbuf, sizeof(sbuf)));
 
 	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
-	fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
+	while (1) {
+		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
+		if (fd < 0 && pid == -1 && errno == EACCES) {
+			pid = 0;
+			continue;
+		}
+		break;
+	}
 	err = errno;
 
+	if (fd >= 0)
+		close(fd);
+
 	if (WARN_ONCE(fd < 0 && err != EBUSY,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, strerror_r(err, sbuf, sizeof(sbuf))))
 		return -1;
 
-	close(fd);
-
 	return 0;
 }
 
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