[PATCH v2 06/16] perf pmu: Probe privilege exclusion modifiers

[Ian Rogers <irogers@google.com>]

Extend perf_pmu__probe() with test_exclude_flag() to probe whether
exclude_user, exclude_kernel, exclude_hv, exclude_idle, exclude_host,
and exclude_guest are accepted by perf_event_open() on the PMU, storing
the results in struct perf_pmu::probed.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/pmu.c | 73 +++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/pmu.h | 12 +++++++
 2 files changed, 85 insertions(+)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 322d90695c4b..ab4265154990 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -3125,6 +3125,65 @@ static bool try_open_attr_variants(struct perf_event_attr *attr,
 	return false;
 }
 
+enum probe_exclude_flag {
+	PROBE_EXCLUDE_USER,
+	PROBE_EXCLUDE_KERNEL,
+	PROBE_EXCLUDE_HV,
+	PROBE_EXCLUDE_IDLE,
+	PROBE_EXCLUDE_HOST,
+	PROBE_EXCLUDE_GUEST,
+};
+
+/* Test whether @which privilege exclusion modifier is accepted by perf_event_open(). */
+static bool test_exclude_flag(const struct perf_event_attr *base_attr,
+			      pid_t pid, int cpu, unsigned long flags,
+			      enum probe_exclude_flag which)
+{
+	struct perf_event_attr attr = *base_attr;
+	int fd;
+
+	switch (which) {
+	case PROBE_EXCLUDE_USER:
+		attr.exclude_user = 1;
+		break;
+	case PROBE_EXCLUDE_KERNEL:
+		attr.exclude_kernel = 1;
+		attr.exclude_user = 0;
+		break;
+	case PROBE_EXCLUDE_HV:
+		attr.exclude_hv = 1;
+		break;
+	case PROBE_EXCLUDE_IDLE:
+		attr.exclude_idle = 1;
+		break;
+	case PROBE_EXCLUDE_HOST:
+		attr.exclude_host = 1;
+		attr.exclude_guest = 0;
+		break;
+	case PROBE_EXCLUDE_GUEST:
+		attr.exclude_guest = 1;
+		attr.exclude_host = 0;
+		break;
+	default:
+		return false;
+	}
+
+	fd = sys_perf_event_open(&attr, pid, cpu, -1, flags);
+	if (fd >= 0) {
+		close(fd);
+		return true;
+	}
+	if (which == PROBE_EXCLUDE_USER && attr.exclude_kernel == 1) {
+		attr.exclude_kernel = 0;
+		fd = sys_perf_event_open(&attr, pid, cpu, -1, flags);
+		if (fd >= 0) {
+			close(fd);
+			return true;
+		}
+	}
+	return false;
+}
+
 /*
  * Probe which enum perf_event_sample_format flags are supported by @pmu,
  * testing a common bulk mask first before probing individual flags.
@@ -3535,6 +3594,20 @@ static void __perf_pmu__probe(struct perf_pmu *pmu, int pmu_cpu)
 		}
 	}
 
+	/* 4. Privilege / exclusion modifiers */
+	pmu->probed.exclude_user =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_USER);
+	pmu->probed.exclude_kernel =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_KERNEL);
+	pmu->probed.exclude_hv =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_HV);
+	pmu->probed.exclude_idle =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_IDLE);
+	pmu->probed.exclude_host =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_HOST);
+	pmu->probed.exclude_guest =
+		test_exclude_flag(&base_attr, pid, cpu, flags, PROBE_EXCLUDE_GUEST);
+
 	if (keepalive_fd >= 0)
 		close(keepalive_fd);
 	pmu->probed.checked = true;
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index fea65e314547..a7d794d67bf2 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -234,6 +234,18 @@ struct perf_pmu {
 		bool can_data_src;
 		/** @probed.can_weight: Supports PERF_SAMPLE_WEIGHT. */
 		bool can_weight;
+		/** @probed.exclude_user: Supports perf_event_attr::exclude_user. */
+		bool exclude_user;
+		/** @probed.exclude_kernel: Supports perf_event_attr::exclude_kernel. */
+		bool exclude_kernel;
+		/** @probed.exclude_hv: Supports perf_event_attr::exclude_hv. */
+		bool exclude_hv;
+		/** @probed.exclude_idle: Supports perf_event_attr::exclude_idle. */
+		bool exclude_idle;
+		/** @probed.exclude_host: Supports perf_event_attr::exclude_host. */
+		bool exclude_host;
+		/** @probed.exclude_guest: Supports perf_event_attr::exclude_guest. */
+		bool exclude_guest;
 		/** @probed.probe_event: Name of the event used to probe the PMU. */
 		char *probe_event;
 		/** @probed.open_err: errno if open_supported is false. */
-- 
2.56.1.703.gf848ed807c-goog