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++) {
union perf_event *event;
perf_mmap__read_catchup(&evlist->backward_mmap[i]);
while ((event = perf_mmap__read_backward(&evlist->backward_mmap[i])) != 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;
}
}
}
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, true);
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;
}