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Subject[PATCH 03/15] perf tools: Add a function to test for kernel support for AUX area sampling
Date
Architectures are expected to know if AUX area sampling is supported by the
hardware. Add a function perf_can_aux_sample() which will determine whether
the kernel supports it.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/evlist.h | 1 +
tools/perf/util/record.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 31 insertions(+)

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 13051409fd22..3655b9ebb147 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -176,6 +176,7 @@ void perf_evlist__set_id_pos(struct evlist *evlist);
bool perf_can_sample_identifier(void);
bool perf_can_record_switch_events(void);
bool perf_can_record_cpu_wide(void);
+bool perf_can_aux_sample(void);
void perf_evlist__config(struct evlist *evlist, struct record_opts *opts,
struct callchain_param *callchain);
int record_opts__config(struct record_opts *opts);
diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 8579505c29a4..e2321edcdd8f 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -136,6 +136,36 @@ bool perf_can_record_cpu_wide(void)
return true;
}

+/*
+ * Architectures are expected to know if AUX area sampling is supported by the
+ * hardware. Here we check for kernel support.
+ */
+bool perf_can_aux_sample(void)
+{
+ struct perf_event_attr attr = {
+ .exclude_kernel = 1,
+ /*
+ * Non-zero value causes the kernel to calculate the effective
+ * attribute size up to that byte.
+ */
+ .aux_sample_size = 1,
+ };
+ int fd;
+
+ fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
+ /*
+ * If the kernel attribute is big enough to contain aux_sample_size
+ * then we assume that it is supported. We are relying on the kernel to
+ * validate the attribute size before anything else that could be wrong.
+ */
+ if (fd == -E2BIG)
+ return false;
+ if (fd >= 0)
+ close(fd);
+
+ return true;
+}
+
void perf_evlist__config(struct evlist *evlist, struct record_opts *opts,
struct callchain_param *callchain)
{
--
2.17.1
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