1 files changed, 151 insertions, 0 deletions
diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
new file mode 100644
index 000000000000..d9ba991a9a30
--- /dev/null
+++ b/tools/perf/tests/backward-ring-buffer.c
@@ -0,0 +1,151 @@
+/*
+ * 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"
+
+#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_evlist__mmap_read_catchup(evlist, i);
+		while ((event = perf_evlist__mmap_read_backward(evlist, 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",
+			 strerror_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(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("No ehough 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));
+	err = parse_events(evlist, "syscalls:sys_enter_prctl", &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);
+
+	/* Set backward bit, ring buffer should be writing from end */
+	evlist__for_each(evlist, evsel)
+		evsel->attr.write_backward = 1;
+
+	err = perf_evlist__open(evlist);
+	if (err < 0) {
+		pr_debug("perf_evlist__open: %s\n",
+			 strerror_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;
+}