xref: /linux/tools/perf/util/perf_api_probe.c (revision 06d07429858317ded2db7986113a9e0129cd599b)
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 
12 typedef void (*setup_probe_fn_t)(struct evsel *evsel);
13 
perf_do_probe_api(setup_probe_fn_t fn,struct perf_cpu cpu,const char * str)14 static 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 
55 out_delete:
56 	evlist__delete(evlist);
57 	return err;
58 }
59 
perf_probe_api(setup_probe_fn_t fn)60 static bool perf_probe_api(setup_probe_fn_t fn)
61 {
62 	const char *try[] = {"cycles:u", "instructions:u", "cpu-clock:u", NULL};
63 	struct perf_cpu_map *cpus;
64 	struct perf_cpu cpu;
65 	int ret, i = 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 	do {
74 		ret = perf_do_probe_api(fn, cpu, try[i++]);
75 		if (!ret)
76 			return true;
77 	} while (ret == -EAGAIN && try[i]);
78 
79 	return false;
80 }
81 
perf_probe_sample_identifier(struct evsel * evsel)82 static void perf_probe_sample_identifier(struct evsel *evsel)
83 {
84 	evsel->core.attr.sample_type |= PERF_SAMPLE_IDENTIFIER;
85 }
86 
perf_probe_comm_exec(struct evsel * evsel)87 static void perf_probe_comm_exec(struct evsel *evsel)
88 {
89 	evsel->core.attr.comm_exec = 1;
90 }
91 
perf_probe_context_switch(struct evsel * evsel)92 static void perf_probe_context_switch(struct evsel *evsel)
93 {
94 	evsel->core.attr.context_switch = 1;
95 }
96 
perf_probe_text_poke(struct evsel * evsel)97 static void perf_probe_text_poke(struct evsel *evsel)
98 {
99 	evsel->core.attr.text_poke = 1;
100 }
101 
perf_probe_build_id(struct evsel * evsel)102 static void perf_probe_build_id(struct evsel *evsel)
103 {
104 	evsel->core.attr.build_id = 1;
105 }
106 
perf_probe_cgroup(struct evsel * evsel)107 static void perf_probe_cgroup(struct evsel *evsel)
108 {
109 	evsel->core.attr.cgroup = 1;
110 }
111 
perf_can_sample_identifier(void)112 bool perf_can_sample_identifier(void)
113 {
114 	return perf_probe_api(perf_probe_sample_identifier);
115 }
116 
perf_can_comm_exec(void)117 bool perf_can_comm_exec(void)
118 {
119 	return perf_probe_api(perf_probe_comm_exec);
120 }
121 
perf_can_record_switch_events(void)122 bool perf_can_record_switch_events(void)
123 {
124 	return perf_probe_api(perf_probe_context_switch);
125 }
126 
perf_can_record_text_poke_events(void)127 bool perf_can_record_text_poke_events(void)
128 {
129 	return perf_probe_api(perf_probe_text_poke);
130 }
131 
perf_can_record_cpu_wide(void)132 bool perf_can_record_cpu_wide(void)
133 {
134 	struct perf_event_attr attr = {
135 		.type = PERF_TYPE_SOFTWARE,
136 		.config = PERF_COUNT_SW_CPU_CLOCK,
137 		.exclude_kernel = 1,
138 	};
139 	struct perf_cpu_map *cpus;
140 	struct perf_cpu cpu;
141 	int fd;
142 
143 	cpus = perf_cpu_map__new_online_cpus();
144 	if (!cpus)
145 		return false;
146 
147 	cpu = perf_cpu_map__cpu(cpus, 0);
148 	perf_cpu_map__put(cpus);
149 
150 	fd = sys_perf_event_open(&attr, -1, cpu.cpu, -1, 0);
151 	if (fd < 0)
152 		return false;
153 	close(fd);
154 
155 	return true;
156 }
157 
158 /*
159  * Architectures are expected to know if AUX area sampling is supported by the
160  * hardware. Here we check for kernel support.
161  */
perf_can_aux_sample(void)162 bool perf_can_aux_sample(void)
163 {
164 	struct perf_event_attr attr = {
165 		.size = sizeof(struct perf_event_attr),
166 		.exclude_kernel = 1,
167 		/*
168 		 * Non-zero value causes the kernel to calculate the effective
169 		 * attribute size up to that byte.
170 		 */
171 		.aux_sample_size = 1,
172 	};
173 	int fd;
174 
175 	fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
176 	/*
177 	 * If the kernel attribute is big enough to contain aux_sample_size
178 	 * then we assume that it is supported. We are relying on the kernel to
179 	 * validate the attribute size before anything else that could be wrong.
180 	 */
181 	if (fd < 0 && errno == E2BIG)
182 		return false;
183 	if (fd >= 0)
184 		close(fd);
185 
186 	return true;
187 }
188 
perf_can_record_build_id(void)189 bool perf_can_record_build_id(void)
190 {
191 	return perf_probe_api(perf_probe_build_id);
192 }
193 
perf_can_record_cgroup(void)194 bool perf_can_record_cgroup(void)
195 {
196 	return perf_probe_api(perf_probe_cgroup);
197 }
198