Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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, int 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_events(evlist, str, NULL))
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, -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, -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 const char *try[] = {"cycles:u", "instructions:u", "cpu-clock:u", NULL};
63 struct perf_cpu_map *cpus;
64 int cpu, ret, i = 0;
65
66 cpus = perf_cpu_map__new(NULL);
67 if (!cpus)
68 return false;
69 cpu = cpus->map[0];
70 perf_cpu_map__put(cpus);
71
72 do {
73 ret = perf_do_probe_api(fn, cpu, try[i++]);
74 if (!ret)
75 return true;
76 } while (ret == -EAGAIN && try[i]);
77
78 return false;
79}
80
81static void perf_probe_sample_identifier(struct evsel *evsel)
82{
83 evsel->core.attr.sample_type |= PERF_SAMPLE_IDENTIFIER;
84}
85
86static void perf_probe_comm_exec(struct evsel *evsel)
87{
88 evsel->core.attr.comm_exec = 1;
89}
90
91static void perf_probe_context_switch(struct evsel *evsel)
92{
93 evsel->core.attr.context_switch = 1;
94}
95
96static void perf_probe_text_poke(struct evsel *evsel)
97{
98 evsel->core.attr.text_poke = 1;
99}
100
101static void perf_probe_build_id(struct evsel *evsel)
102{
103 evsel->core.attr.build_id = 1;
104}
105
106bool perf_can_sample_identifier(void)
107{
108 return perf_probe_api(perf_probe_sample_identifier);
109}
110
111bool perf_can_comm_exec(void)
112{
113 return perf_probe_api(perf_probe_comm_exec);
114}
115
116bool perf_can_record_switch_events(void)
117{
118 return perf_probe_api(perf_probe_context_switch);
119}
120
121bool perf_can_record_text_poke_events(void)
122{
123 return perf_probe_api(perf_probe_text_poke);
124}
125
126bool perf_can_record_cpu_wide(void)
127{
128 struct perf_event_attr attr = {
129 .type = PERF_TYPE_SOFTWARE,
130 .config = PERF_COUNT_SW_CPU_CLOCK,
131 .exclude_kernel = 1,
132 };
133 struct perf_cpu_map *cpus;
134 int cpu, fd;
135
136 cpus = perf_cpu_map__new(NULL);
137 if (!cpus)
138 return false;
139 cpu = cpus->map[0];
140 perf_cpu_map__put(cpus);
141
142 fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
143 if (fd < 0)
144 return false;
145 close(fd);
146
147 return true;
148}
149
150/*
151 * Architectures are expected to know if AUX area sampling is supported by the
152 * hardware. Here we check for kernel support.
153 */
154bool perf_can_aux_sample(void)
155{
156 struct perf_event_attr attr = {
157 .size = sizeof(struct perf_event_attr),
158 .exclude_kernel = 1,
159 /*
160 * Non-zero value causes the kernel to calculate the effective
161 * attribute size up to that byte.
162 */
163 .aux_sample_size = 1,
164 };
165 int fd;
166
167 fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
168 /*
169 * If the kernel attribute is big enough to contain aux_sample_size
170 * then we assume that it is supported. We are relying on the kernel to
171 * validate the attribute size before anything else that could be wrong.
172 */
173 if (fd < 0 && errno == E2BIG)
174 return false;
175 if (fd >= 0)
176 close(fd);
177
178 return true;
179}
180
181bool perf_can_record_build_id(void)
182{
183 return perf_probe_api(perf_probe_build_id);
184}