/* * 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(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;}