perf_api_probe.c

  1/* SPDX-License-Identifier: GPL-2.0 */
  2
  3#include "perf-sys.h"
  4#include "util/cloexec.h"
  5#include "util/evlist.h"
  6#include "util/evsel.h"
  7#include "util/parse-events.h"
  8#include "util/perf_api_probe.h"
  9#include <perf/cpumap.h>
 10#include <errno.h>
 11
 12typedef void (*setup_probe_fn_t)(struct evsel *evsel);
 13
 14static int perf_do_probe_api(setup_probe_fn_t fn, struct perf_cpu cpu, const char *str)
 15{
 16	struct evlist *evlist;
 17	struct evsel *evsel;
 18	unsigned long flags = perf_event_open_cloexec_flag();
 19	int err = -EAGAIN, fd;
 20	static pid_t pid = -1;
 21
 22	evlist = evlist__new();
 23	if (!evlist)
 24		return -ENOMEM;
 25
 26	if (parse_event(evlist, str))
 27		goto out_delete;
 28
 29	evsel = evlist__first(evlist);
 30
 31	while (1) {
 32		fd = sys_perf_event_open(&evsel->core.attr, pid, cpu.cpu, -1, flags);
 33		if (fd < 0) {
 34			if (pid == -1 && errno == EACCES) {
 35				pid = 0;
 36				continue;
 37			}
 38			goto out_delete;
 39		}
 40		break;
 41	}
 42	close(fd);
 43
 44	fn(evsel);
 45
 46	fd = sys_perf_event_open(&evsel->core.attr, pid, cpu.cpu, -1, flags);
 47	if (fd < 0) {
 48		if (errno == EINVAL)
 49			err = -EINVAL;
 50		goto out_delete;
 51	}
 52	close(fd);
 53	err = 0;
 54
 55out_delete:
 56	evlist__delete(evlist);
 57	return err;
 58}
 59
 60static bool perf_probe_api(setup_probe_fn_t fn)
 61{
 62	struct perf_pmu *pmu;
 63	struct perf_cpu_map *cpus;
 64	struct perf_cpu cpu;
 65	int ret = 0;
 66
 67	cpus = perf_cpu_map__new_online_cpus();
 68	if (!cpus)
 69		return false;
 70	cpu = perf_cpu_map__cpu(cpus, 0);
 71	perf_cpu_map__put(cpus);
 72
 73	ret = perf_do_probe_api(fn, cpu, "software/cpu-clock/u");
 74	if (!ret)
 75		return true;
 76
 77	pmu = perf_pmus__scan_core(/*pmu=*/NULL);
 78	if (pmu) {
 79		const char *try[] = {"cycles", "instructions", NULL};
 80		char buf[256];
 81		int i = 0;
 82
 83		while (ret == -EAGAIN && try[i]) {
 84			snprintf(buf, sizeof(buf), "%s/%s/u", pmu->name, try[i++]);
 85			ret = perf_do_probe_api(fn, cpu, buf);
 86			if (!ret)
 87				return true;
 88		}
 89	}
 90	return false;
 91}
 92
 93static void perf_probe_sample_identifier(struct evsel *evsel)
 94{
 95	evsel->core.attr.sample_type |= PERF_SAMPLE_IDENTIFIER;
 96}
 97
 98static void perf_probe_comm_exec(struct evsel *evsel)
 99{
100	evsel->core.attr.comm_exec = 1;
101}
102
103static void perf_probe_context_switch(struct evsel *evsel)
104{
105	evsel->core.attr.context_switch = 1;
106}
107
108static void perf_probe_text_poke(struct evsel *evsel)
109{
110	evsel->core.attr.text_poke = 1;
111}
112
113static void perf_probe_build_id(struct evsel *evsel)
114{
115	evsel->core.attr.build_id = 1;
116}
117
118static void perf_probe_cgroup(struct evsel *evsel)
119{
120	evsel->core.attr.cgroup = 1;
121}
122
123bool perf_can_sample_identifier(void)
124{
125	return perf_probe_api(perf_probe_sample_identifier);
126}
127
128bool perf_can_comm_exec(void)
129{
130	return perf_probe_api(perf_probe_comm_exec);
131}
132
133bool perf_can_record_switch_events(void)
134{
135	return perf_probe_api(perf_probe_context_switch);
136}
137
138bool perf_can_record_text_poke_events(void)
139{
140	return perf_probe_api(perf_probe_text_poke);
141}
142
143bool perf_can_record_cpu_wide(void)
144{
145	struct perf_event_attr attr = {
146		.type = PERF_TYPE_SOFTWARE,
147		.config = PERF_COUNT_SW_CPU_CLOCK,
148		.exclude_kernel = 1,
149	};
150	struct perf_cpu_map *cpus;
151	struct perf_cpu cpu;
152	int fd;
153
154	cpus = perf_cpu_map__new_online_cpus();
155	if (!cpus)
156		return false;
157
158	cpu = perf_cpu_map__cpu(cpus, 0);
159	perf_cpu_map__put(cpus);
160
161	fd = sys_perf_event_open(&attr, -1, cpu.cpu, -1, 0);
162	if (fd < 0)
163		return false;
164	close(fd);
165
166	return true;
167}
168
169/*
170 * Architectures are expected to know if AUX area sampling is supported by the
171 * hardware. Here we check for kernel support.
172 */
173bool perf_can_aux_sample(void)
174{
175	struct perf_event_attr attr = {
176		.size = sizeof(struct perf_event_attr),
177		.exclude_kernel = 1,
178		/*
179		 * Non-zero value causes the kernel to calculate the effective
180		 * attribute size up to that byte.
181		 */
182		.aux_sample_size = 1,
183	};
184	int fd;
185
186	fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
187	/*
188	 * If the kernel attribute is big enough to contain aux_sample_size
189	 * then we assume that it is supported. We are relying on the kernel to
190	 * validate the attribute size before anything else that could be wrong.
191	 */
192	if (fd < 0 && errno == E2BIG)
193		return false;
194	if (fd >= 0)
195		close(fd);
196
197	return true;
198}
199
200bool perf_can_record_build_id(void)
201{
202	return perf_probe_api(perf_probe_build_id);
203}
204
205bool perf_can_record_cgroup(void)
206{
207	return perf_probe_api(perf_probe_cgroup);
208}