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Subject[PATCH 3/4] perf tools: Fix probing the kernel API with cpu-wide events
Date
Fall back to probing with the current pid if cpu-wide
probing fails. This primarily affects the setting of
comm_exec flag when the user is un-privileged and
/proc/sys/kernel/perf_event_paranoid > 0. The change
to comm_exec can be observed by using -vv with
perf record and a kernel that supports comm_exec.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/record.c | 36 +++++++++++++++++++++++++++---------
1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 68ad2d0..cf69325 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -14,6 +14,7 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)
struct perf_evsel *evsel;
unsigned long flags = perf_event_open_cloexec_flag();
int err = -EAGAIN, fd;
+ static pid_t pid = -1;

evlist = perf_evlist__new();
if (!evlist)
@@ -24,14 +25,22 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)

evsel = perf_evlist__first(evlist);

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
- if (fd < 0)
- goto out_delete;
+ while (1) {
+ fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1, flags);
+ if (fd < 0) {
+ if (pid == -1 && errno == EACCES) {
+ pid = 0;
+ continue;
+ }
+ goto out_delete;
+ }
+ break;
+ }
close(fd);

fn(evsel);

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
+ fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1, flags);
if (fd < 0) {
if (errno == EINVAL)
err = -EINVAL;
@@ -201,6 +210,7 @@ bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str)
struct perf_evsel *evsel;
int err, fd, cpu;
bool ret = false;
+ pid_t pid = -1;

temp_evlist = perf_evlist__new();
if (!temp_evlist)
@@ -221,12 +231,20 @@ bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str)
cpu = evlist->cpus->map[0];
}

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1,
- perf_event_open_cloexec_flag());
- if (fd >= 0) {
- close(fd);
- ret = true;
+ while (1) {
+ fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1,
+ perf_event_open_cloexec_flag());
+ if (fd < 0) {
+ if (pid == -1 && errno == EACCES) {
+ pid = 0;
+ continue;
+ }
+ goto out_delete;
+ }
+ break;
}
+ close(fd);
+ ret = true;

out_delete:
perf_evlist__delete(temp_evlist);
--
1.8.3.2


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