Commit 48536c91 authored Feb 24, 2015 by Adrian Hunter Committed by Arnaldo Carvalho de Melo Feb 25, 2015

perf tools: Fix probing for PERF_FLAG_FD_CLOEXEC flag



Commit f6edb53c 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@intel.com>
Based-on-patch-by: David Ahern <david.ahern@oracle.com>
Acked-by: David Ahern <david.ahern@oracle.com>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/54EC610C.8000403@intel.com


Cc: stable@vger.kernel.org  # v3.18+
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 95a09cfa

tools/perf/util/cloexec.c

+15 −3

Original line number	Diff line number	Diff line
		@@ -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 */
		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;
		}