LXR linux/tools/perf/util/perf_api

   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
 101bool perf_can_sample_identifier(void)
 102{
 103        return perf_probe_api(perf_probe_sample_identifier);
 104}
 105
 106bool perf_can_comm_exec(void)
 107{
 108        return perf_probe_api(perf_probe_comm_exec);
 109}
 110
 111bool perf_can_record_switch_events(void)
 112{
 113        return perf_probe_api(perf_probe_context_switch);
 114}
 115
 116bool perf_can_record_text_poke_events(void)
 117{
 118        return perf_probe_api(perf_probe_text_poke);
 119}
 120
 121bool perf_can_record_cpu_wide(void)
 122{
 123        struct perf_event_attr attr = {
 124                .type = PERF_TYPE_SOFTWARE,
 125                .config = PERF_COUNT_SW_CPU_CLOCK,
 126                .exclude_kernel = 1,
 127        };
 128        struct perf_cpu_map *cpus;
 129        int cpu, fd;
 130
 131        cpus = perf_cpu_map__new(NULL);
 132        if (!cpus)
 133                return false;
 134        cpu = cpus->map[0];
 135        perf_cpu_map__put(cpus);
 136
 137        fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
 138        if (fd < 0)
 139                return false;
 140        close(fd);
 141
 142        return true;
 143}
 144
 145/*
 146 * Architectures are expected to know if AUX area sampling is supported by the
 147 * hardware. Here we check for kernel support.
 148 */
 149bool perf_can_aux_sample(void)
 150{
 151        struct perf_event_attr attr = {
 152                .size = sizeof(struct perf_event_attr),
 153                .exclude_kernel = 1,
 154                /*
 155                 * Non-zero value causes the kernel to calculate the effective
 156                 * attribute size up to that byte.
 157                 */
 158                .aux_sample_size = 1,
 159        };
 160        int fd;
 161
 162        fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
 163        /*
 164         * If the kernel attribute is big enough to contain aux_sample_size
 165         * then we assume that it is supported. We are relying on the kernel to
 166         * validate the attribute size before anything else that could be wrong.
 167         */
 168        if (fd < 0 && errno == E2BIG)
 169                return false;
 170        if (fd >= 0)
 171                close(fd);
 172
 173        return true;
 174}
 175