backward-ring-buffer.c

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// SPDX-License-Identifier: GPL-2.0
/*
 * Test backward bit in event attribute, read ring buffer from end to
 * beginning
 */

#include <perf.h>
#include <evlist.h>
#include <sys/prctl.h>
#include "tests.h"
#include "debug.h"
#include <errno.h>

#define NR_ITERS 111

static void testcase(void)
{
    int i;

    for (i = 0; i < NR_ITERS; i++) {
        char proc_name[10];

        snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);
        prctl(PR_SET_NAME, proc_name);
    }
}

static int count_samples(struct perf_evlist *evlist, int *sample_count,
             int *comm_count)
{
    int i;

    for (i = 0; i < evlist->nr_mmaps; i++) {
        struct perf_mmap *map = &evlist->overwrite_mmap[i];
        union perf_event *event;

        perf_mmap__read_init(map);
        while ((event = perf_mmap__read_event(map)) != NULL) {
            const u32 type = event->header.type;

            switch (type) {
            case PERF_RECORD_SAMPLE:
                (*sample_count)++;
                break;
            case PERF_RECORD_COMM:
                (*comm_count)++;
                break;
            default:
                pr_err("Unexpected record of type %d\n", type);
                return TEST_FAIL;
            }
        }
        perf_mmap__read_done(map);
    }
    return TEST_OK;
}

static int do_test(struct perf_evlist *evlist, int mmap_pages,
           int *sample_count, int *comm_count)
{
    int err;
    char sbuf[STRERR_BUFSIZE];

    err = perf_evlist__mmap(evlist, mmap_pages);
    if (err < 0) {
        pr_debug("perf_evlist__mmap: %s\n",
             str_error_r(errno, sbuf, sizeof(sbuf)));
        return TEST_FAIL;
    }

    perf_evlist__enable(evlist);
    testcase();
    perf_evlist__disable(evlist);

    err = count_samples(evlist, sample_count, comm_count);
    perf_evlist__munmap(evlist);
    return err;
}


int test__backward_ring_buffer(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    int ret = TEST_SKIP, err, sample_count = 0, comm_count = 0;
    char pid[16], sbuf[STRERR_BUFSIZE];
    struct perf_evlist *evlist;
    struct perf_evsel *evsel __maybe_unused;
    struct parse_events_error parse_error;
    struct record_opts opts = {
        .target = {
            .uid = UINT_MAX,
            .uses_mmap = true,
        },
        .freq         = 0,
        .mmap_pages   = 256,
        .default_interval = 1,
    };

    snprintf(pid, sizeof(pid), "%d", getpid());
    pid[sizeof(pid) - 1] = '\0';
    opts.target.tid = opts.target.pid = pid;

    evlist = perf_evlist__new();
    if (!evlist) {
        pr_debug("Not enough memory to create evlist\n");
        return TEST_FAIL;
    }

    err = perf_evlist__create_maps(evlist, &opts.target);
    if (err < 0) {
        pr_debug("Not enough memory to create thread/cpu maps\n");
        goto out_delete_evlist;
    }

    bzero(&parse_error, sizeof(parse_error));
    /*
     * Set backward bit, ring buffer should be writing from end. Record
     * it in aux evlist
     */
    err = parse_events(evlist, "syscalls:sys_enter_prctl/overwrite/", &parse_error);
    if (err) {
        pr_debug("Failed to parse tracepoint event, try use root\n");
        ret = TEST_SKIP;
        goto out_delete_evlist;
    }

    perf_evlist__config(evlist, &opts, NULL);

    err = perf_evlist__open(evlist);
    if (err < 0) {
        pr_debug("perf_evlist__open: %s\n",
             str_error_r(errno, sbuf, sizeof(sbuf)));
        goto out_delete_evlist;
    }

    ret = TEST_FAIL;
    err = do_test(evlist, opts.mmap_pages, &sample_count,
              &comm_count);
    if (err != TEST_OK)
        goto out_delete_evlist;

    if ((sample_count != NR_ITERS) || (comm_count != NR_ITERS)) {
        pr_err("Unexpected counter: sample_count=%d, comm_count=%d\n",
               sample_count, comm_count);
        goto out_delete_evlist;
    }

    err = do_test(evlist, 1, &sample_count, &comm_count);
    if (err != TEST_OK)
        goto out_delete_evlist;

    ret = TEST_OK;
out_delete_evlist:
    perf_evlist__delete(evlist);
    return ret;
}