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@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>

1 files changed, 15 insertions, 3 deletions

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 47b78b3f0325..6da965bdbc2c 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;
 }