record.c

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// SPDX-License-Identifier: GPL-2.0
#include "evlist.h"
#include "evsel.h"
#include "cpumap.h"
#include "parse-events.h"
#include <errno.h>
#include <api/fs/fs.h>
#include <subcmd/parse-options.h>
#include "util.h"
#include "cloexec.h"

typedef void (*setup_probe_fn_t)(struct perf_evsel *evsel);

static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)
{
    struct perf_evlist *evlist;
    struct perf_evsel *evsel;
    unsigned long flags = perf_event_open_cloexec_flag();
    int err = -EAGAIN, fd;
    static pid_t pid = -1;

    evlist = perf_evlist__new();
    if (!evlist)
        return -ENOMEM;

    if (parse_events(evlist, str, NULL))
        goto out_delete;

    evsel = perf_evlist__first(evlist);

    while (1) {
        fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1, flags);
        if (fd < 0) {
            if (pid == -1 && errno == EACCES) {
                pid = 0;
                continue;
            }
            goto out_delete;
        }
        break;
    }
    close(fd);

    fn(evsel);

    fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1, flags);
    if (fd < 0) {
        if (errno == EINVAL)
            err = -EINVAL;
        goto out_delete;
    }
    close(fd);
    err = 0;

out_delete:
    perf_evlist__delete(evlist);
    return err;
}

static bool perf_probe_api(setup_probe_fn_t fn)
{
    const char *try[] = {"cycles:u", "instructions:u", "cpu-clock:u", NULL};
    struct cpu_map *cpus;
    int cpu, ret, i = 0;

    cpus = cpu_map__new(NULL);
    if (!cpus)
        return false;
    cpu = cpus->map[0];
    cpu_map__put(cpus);

    do {
        ret = perf_do_probe_api(fn, cpu, try[i++]);
        if (!ret)
            return true;
    } while (ret == -EAGAIN && try[i]);

    return false;
}

static void perf_probe_sample_identifier(struct perf_evsel *evsel)
{
    evsel->attr.sample_type |= PERF_SAMPLE_IDENTIFIER;
}

static void perf_probe_comm_exec(struct perf_evsel *evsel)
{
    evsel->attr.comm_exec = 1;
}

static void perf_probe_context_switch(struct perf_evsel *evsel)
{
    evsel->attr.context_switch = 1;
}

bool perf_can_sample_identifier(void)
{
    return perf_probe_api(perf_probe_sample_identifier);
}

static bool perf_can_comm_exec(void)
{
    return perf_probe_api(perf_probe_comm_exec);
}

bool perf_can_record_switch_events(void)
{
    return perf_probe_api(perf_probe_context_switch);
}

bool perf_can_record_cpu_wide(void)
{
    struct perf_event_attr attr = {
        .type = PERF_TYPE_SOFTWARE,
        .config = PERF_COUNT_SW_CPU_CLOCK,
        .exclude_kernel = 1,
    };
    struct cpu_map *cpus;
    int cpu, fd;

    cpus = cpu_map__new(NULL);
    if (!cpus)
        return false;
    cpu = cpus->map[0];
    cpu_map__put(cpus);

    fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
    if (fd < 0)
        return false;
    close(fd);

    return true;
}

void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts,
             struct callchain_param *callchain)
{
    struct perf_evsel *evsel;
    bool use_sample_identifier = false;
    bool use_comm_exec;
    bool sample_id = opts->sample_id;

    /*
     * Set the evsel leader links before we configure attributes,
     * since some might depend on this info.
     */
    if (opts->group)
        perf_evlist__set_leader(evlist);

    if (evlist->cpus->map[0] < 0)
        opts->no_inherit = true;

    use_comm_exec = perf_can_comm_exec();

    evlist__for_each_entry(evlist, evsel) {
        perf_evsel__config(evsel, opts, callchain);
        if (evsel->tracking && use_comm_exec)
            evsel->attr.comm_exec = 1;
    }

    if (opts->full_auxtrace) {
        /*
         * Need to be able to synthesize and parse selected events with
         * arbitrary sample types, which requires always being able to
         * match the id.
         */
        use_sample_identifier = perf_can_sample_identifier();
        sample_id = true;
    } else if (evlist->nr_entries > 1) {
        struct perf_evsel *first = perf_evlist__first(evlist);

        evlist__for_each_entry(evlist, evsel) {
            if (evsel->attr.sample_type == first->attr.sample_type)
                continue;
            use_sample_identifier = perf_can_sample_identifier();
            break;
        }
        sample_id = true;
    }

    if (sample_id) {
        evlist__for_each_entry(evlist, evsel)
            perf_evsel__set_sample_id(evsel, use_sample_identifier);
    }

    perf_evlist__set_id_pos(evlist);
}

static int get_max_rate(unsigned int *rate)
{
    return sysctl__read_int("kernel/perf_event_max_sample_rate", (int *)rate);
}

static int record_opts__config_freq(struct record_opts *opts)
{
    bool user_freq = opts->user_freq != UINT_MAX;
    unsigned int max_rate;

    if (opts->user_interval != ULLONG_MAX)
        opts->default_interval = opts->user_interval;
    if (user_freq)
        opts->freq = opts->user_freq;

    /*
     * User specified count overrides default frequency.
     */
    if (opts->default_interval)
        opts->freq = 0;
    else if (opts->freq) {
        opts->default_interval = opts->freq;
    } else {
        pr_err("frequency and count are zero, aborting\n");
        return -1;
    }

    if (get_max_rate(&max_rate))
        return 0;

    /*
     * User specified frequency is over current maximum.
     */
    if (user_freq && (max_rate < opts->freq)) {
        if (opts->strict_freq) {
            pr_err("error: Maximum frequency rate (%'u Hz) exceeded.\n"
                   "       Please use -F freq option with a lower value or consider\n"
                   "       tweaking /proc/sys/kernel/perf_event_max_sample_rate.\n",
                   max_rate);
            return -1;
        } else {
            pr_warning("warning: Maximum frequency rate (%'u Hz) exceeded, throttling from %'u Hz to %'u Hz.\n"
                   "         The limit can be raised via /proc/sys/kernel/perf_event_max_sample_rate.\n"
                   "         The kernel will lower it when perf's interrupts take too long.\n"
                   "         Use --strict-freq to disable this throttling, refusing to record.\n",
                   max_rate, opts->freq, max_rate);

            opts->freq = max_rate;
        }
    }

    /*
     * Default frequency is over current maximum.
     */
    if (max_rate < opts->freq) {
        pr_warning("Lowering default frequency rate to %u.\n"
               "Please consider tweaking "
               "/proc/sys/kernel/perf_event_max_sample_rate.\n",
               max_rate);
        opts->freq = max_rate;
    }

    return 0;
}

int record_opts__config(struct record_opts *opts)
{
    return record_opts__config_freq(opts);
}

bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str)
{
    struct perf_evlist *temp_evlist;
    struct perf_evsel *evsel;
    int err, fd, cpu;
    bool ret = false;
    pid_t pid = -1;

    temp_evlist = perf_evlist__new();
    if (!temp_evlist)
        return false;

    err = parse_events(temp_evlist, str, NULL);
    if (err)
        goto out_delete;

    evsel = perf_evlist__last(temp_evlist);

    if (!evlist || cpu_map__empty(evlist->cpus)) {
        struct cpu_map *cpus = cpu_map__new(NULL);

        cpu =  cpus ? cpus->map[0] : 0;
        cpu_map__put(cpus);
    } else {
        cpu = evlist->cpus->map[0];
    }

    while (1) {
        fd = sys_perf_event_open(&evsel->attr, pid, cpu, -1,
                     perf_event_open_cloexec_flag());
        if (fd < 0) {
            if (pid == -1 && errno == EACCES) {
                pid = 0;
                continue;
            }
            goto out_delete;
        }
        break;
    }
    close(fd);
    ret = true;

out_delete:
    perf_evlist__delete(temp_evlist);
    return ret;
}

int record__parse_freq(const struct option *opt, const char *str, int unset __maybe_unused)
{
    unsigned int freq;
    struct record_opts *opts = opt->value;

    if (!str)
        return -EINVAL;

    if (strcasecmp(str, "max") == 0) {
        if (get_max_rate(&freq)) {
            pr_err("couldn't read /proc/sys/kernel/perf_event_max_sample_rate\n");
            return -1;
        }
        pr_info("info: Using a maximum frequency rate of %'d Hz\n", freq);
    } else {
        freq = atoi(str);
    }

    opts->user_freq = freq;
    return 0;
}