xref: /openbmc/linux/tools/perf/util/bpf_counter.c (revision 2cf1c348)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 /* Copyright (c) 2019 Facebook */
4 
5 #include <assert.h>
6 #include <limits.h>
7 #include <unistd.h>
8 #include <sys/file.h>
9 #include <sys/time.h>
10 #include <linux/err.h>
11 #include <linux/zalloc.h>
12 #include <api/fs/fs.h>
13 #include <perf/bpf_perf.h>
14 
15 #include "bpf_counter.h"
16 #include "bpf-utils.h"
17 #include "counts.h"
18 #include "debug.h"
19 #include "evsel.h"
20 #include "evlist.h"
21 #include "target.h"
22 #include "cgroup.h"
23 #include "cpumap.h"
24 #include "thread_map.h"
25 
26 #include "bpf_skel/bpf_prog_profiler.skel.h"
27 #include "bpf_skel/bperf_u.h"
28 #include "bpf_skel/bperf_leader.skel.h"
29 #include "bpf_skel/bperf_follower.skel.h"
30 
31 #define ATTR_MAP_SIZE 16
32 
33 static inline void *u64_to_ptr(__u64 ptr)
34 {
35 	return (void *)(unsigned long)ptr;
36 }
37 
38 static struct bpf_counter *bpf_counter_alloc(void)
39 {
40 	struct bpf_counter *counter;
41 
42 	counter = zalloc(sizeof(*counter));
43 	if (counter)
44 		INIT_LIST_HEAD(&counter->list);
45 	return counter;
46 }
47 
48 static int bpf_program_profiler__destroy(struct evsel *evsel)
49 {
50 	struct bpf_counter *counter, *tmp;
51 
52 	list_for_each_entry_safe(counter, tmp,
53 				 &evsel->bpf_counter_list, list) {
54 		list_del_init(&counter->list);
55 		bpf_prog_profiler_bpf__destroy(counter->skel);
56 		free(counter);
57 	}
58 	assert(list_empty(&evsel->bpf_counter_list));
59 
60 	return 0;
61 }
62 
63 static char *bpf_target_prog_name(int tgt_fd)
64 {
65 	struct bpf_func_info *func_info;
66 	struct perf_bpil *info_linear;
67 	const struct btf_type *t;
68 	struct btf *btf = NULL;
69 	char *name = NULL;
70 
71 	info_linear = get_bpf_prog_info_linear(tgt_fd, 1UL << PERF_BPIL_FUNC_INFO);
72 	if (IS_ERR_OR_NULL(info_linear)) {
73 		pr_debug("failed to get info_linear for prog FD %d\n", tgt_fd);
74 		return NULL;
75 	}
76 
77 	if (info_linear->info.btf_id == 0) {
78 		pr_debug("prog FD %d doesn't have valid btf\n", tgt_fd);
79 		goto out;
80 	}
81 
82 	btf = btf__load_from_kernel_by_id(info_linear->info.btf_id);
83 	if (libbpf_get_error(btf)) {
84 		pr_debug("failed to load btf for prog FD %d\n", tgt_fd);
85 		goto out;
86 	}
87 
88 	func_info = u64_to_ptr(info_linear->info.func_info);
89 	t = btf__type_by_id(btf, func_info[0].type_id);
90 	if (!t) {
91 		pr_debug("btf %d doesn't have type %d\n",
92 			 info_linear->info.btf_id, func_info[0].type_id);
93 		goto out;
94 	}
95 	name = strdup(btf__name_by_offset(btf, t->name_off));
96 out:
97 	btf__free(btf);
98 	free(info_linear);
99 	return name;
100 }
101 
102 static int bpf_program_profiler_load_one(struct evsel *evsel, u32 prog_id)
103 {
104 	struct bpf_prog_profiler_bpf *skel;
105 	struct bpf_counter *counter;
106 	struct bpf_program *prog;
107 	char *prog_name;
108 	int prog_fd;
109 	int err;
110 
111 	prog_fd = bpf_prog_get_fd_by_id(prog_id);
112 	if (prog_fd < 0) {
113 		pr_err("Failed to open fd for bpf prog %u\n", prog_id);
114 		return -1;
115 	}
116 	counter = bpf_counter_alloc();
117 	if (!counter) {
118 		close(prog_fd);
119 		return -1;
120 	}
121 
122 	skel = bpf_prog_profiler_bpf__open();
123 	if (!skel) {
124 		pr_err("Failed to open bpf skeleton\n");
125 		goto err_out;
126 	}
127 
128 	skel->rodata->num_cpu = evsel__nr_cpus(evsel);
129 
130 	bpf_map__set_max_entries(skel->maps.events, evsel__nr_cpus(evsel));
131 	bpf_map__set_max_entries(skel->maps.fentry_readings, 1);
132 	bpf_map__set_max_entries(skel->maps.accum_readings, 1);
133 
134 	prog_name = bpf_target_prog_name(prog_fd);
135 	if (!prog_name) {
136 		pr_err("Failed to get program name for bpf prog %u. Does it have BTF?\n", prog_id);
137 		goto err_out;
138 	}
139 
140 	bpf_object__for_each_program(prog, skel->obj) {
141 		err = bpf_program__set_attach_target(prog, prog_fd, prog_name);
142 		if (err) {
143 			pr_err("bpf_program__set_attach_target failed.\n"
144 			       "Does bpf prog %u have BTF?\n", prog_id);
145 			goto err_out;
146 		}
147 	}
148 	set_max_rlimit();
149 	err = bpf_prog_profiler_bpf__load(skel);
150 	if (err) {
151 		pr_err("bpf_prog_profiler_bpf__load failed\n");
152 		goto err_out;
153 	}
154 
155 	assert(skel != NULL);
156 	counter->skel = skel;
157 	list_add(&counter->list, &evsel->bpf_counter_list);
158 	close(prog_fd);
159 	return 0;
160 err_out:
161 	bpf_prog_profiler_bpf__destroy(skel);
162 	free(counter);
163 	close(prog_fd);
164 	return -1;
165 }
166 
167 static int bpf_program_profiler__load(struct evsel *evsel, struct target *target)
168 {
169 	char *bpf_str, *bpf_str_, *tok, *saveptr = NULL, *p;
170 	u32 prog_id;
171 	int ret;
172 
173 	bpf_str_ = bpf_str = strdup(target->bpf_str);
174 	if (!bpf_str)
175 		return -1;
176 
177 	while ((tok = strtok_r(bpf_str, ",", &saveptr)) != NULL) {
178 		prog_id = strtoul(tok, &p, 10);
179 		if (prog_id == 0 || prog_id == UINT_MAX ||
180 		    (*p != '\0' && *p != ',')) {
181 			pr_err("Failed to parse bpf prog ids %s\n",
182 			       target->bpf_str);
183 			return -1;
184 		}
185 
186 		ret = bpf_program_profiler_load_one(evsel, prog_id);
187 		if (ret) {
188 			bpf_program_profiler__destroy(evsel);
189 			free(bpf_str_);
190 			return -1;
191 		}
192 		bpf_str = NULL;
193 	}
194 	free(bpf_str_);
195 	return 0;
196 }
197 
198 static int bpf_program_profiler__enable(struct evsel *evsel)
199 {
200 	struct bpf_counter *counter;
201 	int ret;
202 
203 	list_for_each_entry(counter, &evsel->bpf_counter_list, list) {
204 		assert(counter->skel != NULL);
205 		ret = bpf_prog_profiler_bpf__attach(counter->skel);
206 		if (ret) {
207 			bpf_program_profiler__destroy(evsel);
208 			return ret;
209 		}
210 	}
211 	return 0;
212 }
213 
214 static int bpf_program_profiler__disable(struct evsel *evsel)
215 {
216 	struct bpf_counter *counter;
217 
218 	list_for_each_entry(counter, &evsel->bpf_counter_list, list) {
219 		assert(counter->skel != NULL);
220 		bpf_prog_profiler_bpf__detach(counter->skel);
221 	}
222 	return 0;
223 }
224 
225 static int bpf_program_profiler__read(struct evsel *evsel)
226 {
227 	// perf_cpu_map uses /sys/devices/system/cpu/online
228 	int num_cpu = evsel__nr_cpus(evsel);
229 	// BPF_MAP_TYPE_PERCPU_ARRAY uses /sys/devices/system/cpu/possible
230 	// Sometimes possible > online, like on a Ryzen 3900X that has 24
231 	// threads but its possible showed 0-31 -acme
232 	int num_cpu_bpf = libbpf_num_possible_cpus();
233 	struct bpf_perf_event_value values[num_cpu_bpf];
234 	struct bpf_counter *counter;
235 	int reading_map_fd;
236 	__u32 key = 0;
237 	int err, cpu;
238 
239 	if (list_empty(&evsel->bpf_counter_list))
240 		return -EAGAIN;
241 
242 	for (cpu = 0; cpu < num_cpu; cpu++) {
243 		perf_counts(evsel->counts, cpu, 0)->val = 0;
244 		perf_counts(evsel->counts, cpu, 0)->ena = 0;
245 		perf_counts(evsel->counts, cpu, 0)->run = 0;
246 	}
247 	list_for_each_entry(counter, &evsel->bpf_counter_list, list) {
248 		struct bpf_prog_profiler_bpf *skel = counter->skel;
249 
250 		assert(skel != NULL);
251 		reading_map_fd = bpf_map__fd(skel->maps.accum_readings);
252 
253 		err = bpf_map_lookup_elem(reading_map_fd, &key, values);
254 		if (err) {
255 			pr_err("failed to read value\n");
256 			return err;
257 		}
258 
259 		for (cpu = 0; cpu < num_cpu; cpu++) {
260 			perf_counts(evsel->counts, cpu, 0)->val += values[cpu].counter;
261 			perf_counts(evsel->counts, cpu, 0)->ena += values[cpu].enabled;
262 			perf_counts(evsel->counts, cpu, 0)->run += values[cpu].running;
263 		}
264 	}
265 	return 0;
266 }
267 
268 static int bpf_program_profiler__install_pe(struct evsel *evsel, int cpu_map_idx,
269 					    int fd)
270 {
271 	struct bpf_prog_profiler_bpf *skel;
272 	struct bpf_counter *counter;
273 	int ret;
274 
275 	list_for_each_entry(counter, &evsel->bpf_counter_list, list) {
276 		skel = counter->skel;
277 		assert(skel != NULL);
278 
279 		ret = bpf_map_update_elem(bpf_map__fd(skel->maps.events),
280 					  &cpu_map_idx, &fd, BPF_ANY);
281 		if (ret)
282 			return ret;
283 	}
284 	return 0;
285 }
286 
287 struct bpf_counter_ops bpf_program_profiler_ops = {
288 	.load       = bpf_program_profiler__load,
289 	.enable	    = bpf_program_profiler__enable,
290 	.disable    = bpf_program_profiler__disable,
291 	.read       = bpf_program_profiler__read,
292 	.destroy    = bpf_program_profiler__destroy,
293 	.install_pe = bpf_program_profiler__install_pe,
294 };
295 
296 static bool bperf_attr_map_compatible(int attr_map_fd)
297 {
298 	struct bpf_map_info map_info = {0};
299 	__u32 map_info_len = sizeof(map_info);
300 	int err;
301 
302 	err = bpf_obj_get_info_by_fd(attr_map_fd, &map_info, &map_info_len);
303 
304 	if (err)
305 		return false;
306 	return (map_info.key_size == sizeof(struct perf_event_attr)) &&
307 		(map_info.value_size == sizeof(struct perf_event_attr_map_entry));
308 }
309 
310 int __weak
311 bpf_map_create(enum bpf_map_type map_type,
312 	       const char *map_name __maybe_unused,
313 	       __u32 key_size,
314 	       __u32 value_size,
315 	       __u32 max_entries,
316 	       const struct bpf_map_create_opts *opts __maybe_unused)
317 {
318 #pragma GCC diagnostic push
319 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
320 	return bpf_create_map(map_type, key_size, value_size, max_entries, 0);
321 #pragma GCC diagnostic pop
322 }
323 
324 static int bperf_lock_attr_map(struct target *target)
325 {
326 	char path[PATH_MAX];
327 	int map_fd, err;
328 
329 	if (target->attr_map) {
330 		scnprintf(path, PATH_MAX, "%s", target->attr_map);
331 	} else {
332 		scnprintf(path, PATH_MAX, "%s/fs/bpf/%s", sysfs__mountpoint(),
333 			  BPF_PERF_DEFAULT_ATTR_MAP_PATH);
334 	}
335 
336 	if (access(path, F_OK)) {
337 		map_fd = bpf_map_create(BPF_MAP_TYPE_HASH, NULL,
338 					sizeof(struct perf_event_attr),
339 					sizeof(struct perf_event_attr_map_entry),
340 					ATTR_MAP_SIZE, NULL);
341 		if (map_fd < 0)
342 			return -1;
343 
344 		err = bpf_obj_pin(map_fd, path);
345 		if (err) {
346 			/* someone pinned the map in parallel? */
347 			close(map_fd);
348 			map_fd = bpf_obj_get(path);
349 			if (map_fd < 0)
350 				return -1;
351 		}
352 	} else {
353 		map_fd = bpf_obj_get(path);
354 		if (map_fd < 0)
355 			return -1;
356 	}
357 
358 	if (!bperf_attr_map_compatible(map_fd)) {
359 		close(map_fd);
360 		return -1;
361 
362 	}
363 	err = flock(map_fd, LOCK_EX);
364 	if (err) {
365 		close(map_fd);
366 		return -1;
367 	}
368 	return map_fd;
369 }
370 
371 static int bperf_check_target(struct evsel *evsel,
372 			      struct target *target,
373 			      enum bperf_filter_type *filter_type,
374 			      __u32 *filter_entry_cnt)
375 {
376 	if (evsel->core.leader->nr_members > 1) {
377 		pr_err("bpf managed perf events do not yet support groups.\n");
378 		return -1;
379 	}
380 
381 	/* determine filter type based on target */
382 	if (target->system_wide) {
383 		*filter_type = BPERF_FILTER_GLOBAL;
384 		*filter_entry_cnt = 1;
385 	} else if (target->cpu_list) {
386 		*filter_type = BPERF_FILTER_CPU;
387 		*filter_entry_cnt = perf_cpu_map__nr(evsel__cpus(evsel));
388 	} else if (target->tid) {
389 		*filter_type = BPERF_FILTER_PID;
390 		*filter_entry_cnt = perf_thread_map__nr(evsel->core.threads);
391 	} else if (target->pid || evsel->evlist->workload.pid != -1) {
392 		*filter_type = BPERF_FILTER_TGID;
393 		*filter_entry_cnt = perf_thread_map__nr(evsel->core.threads);
394 	} else {
395 		pr_err("bpf managed perf events do not yet support these targets.\n");
396 		return -1;
397 	}
398 
399 	return 0;
400 }
401 
402 static	struct perf_cpu_map *all_cpu_map;
403 
404 static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
405 				       struct perf_event_attr_map_entry *entry)
406 {
407 	struct bperf_leader_bpf *skel = bperf_leader_bpf__open();
408 	int link_fd, diff_map_fd, err;
409 	struct bpf_link *link = NULL;
410 
411 	if (!skel) {
412 		pr_err("Failed to open leader skeleton\n");
413 		return -1;
414 	}
415 
416 	bpf_map__set_max_entries(skel->maps.events, libbpf_num_possible_cpus());
417 	err = bperf_leader_bpf__load(skel);
418 	if (err) {
419 		pr_err("Failed to load leader skeleton\n");
420 		goto out;
421 	}
422 
423 	link = bpf_program__attach(skel->progs.on_switch);
424 	if (IS_ERR(link)) {
425 		pr_err("Failed to attach leader program\n");
426 		err = PTR_ERR(link);
427 		goto out;
428 	}
429 
430 	link_fd = bpf_link__fd(link);
431 	diff_map_fd = bpf_map__fd(skel->maps.diff_readings);
432 	entry->link_id = bpf_link_get_id(link_fd);
433 	entry->diff_map_id = bpf_map_get_id(diff_map_fd);
434 	err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, entry, BPF_ANY);
435 	assert(err == 0);
436 
437 	evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry->link_id);
438 	assert(evsel->bperf_leader_link_fd >= 0);
439 
440 	/*
441 	 * save leader_skel for install_pe, which is called within
442 	 * following evsel__open_per_cpu call
443 	 */
444 	evsel->leader_skel = skel;
445 	evsel__open_per_cpu(evsel, all_cpu_map, -1);
446 
447 out:
448 	bperf_leader_bpf__destroy(skel);
449 	bpf_link__destroy(link);
450 	return err;
451 }
452 
453 static int bperf__load(struct evsel *evsel, struct target *target)
454 {
455 	struct perf_event_attr_map_entry entry = {0xffffffff, 0xffffffff};
456 	int attr_map_fd, diff_map_fd = -1, err;
457 	enum bperf_filter_type filter_type;
458 	__u32 filter_entry_cnt, i;
459 
460 	if (bperf_check_target(evsel, target, &filter_type, &filter_entry_cnt))
461 		return -1;
462 
463 	if (!all_cpu_map) {
464 		all_cpu_map = perf_cpu_map__new(NULL);
465 		if (!all_cpu_map)
466 			return -1;
467 	}
468 
469 	evsel->bperf_leader_prog_fd = -1;
470 	evsel->bperf_leader_link_fd = -1;
471 
472 	/*
473 	 * Step 1: hold a fd on the leader program and the bpf_link, if
474 	 * the program is not already gone, reload the program.
475 	 * Use flock() to ensure exclusive access to the perf_event_attr
476 	 * map.
477 	 */
478 	attr_map_fd = bperf_lock_attr_map(target);
479 	if (attr_map_fd < 0) {
480 		pr_err("Failed to lock perf_event_attr map\n");
481 		return -1;
482 	}
483 
484 	err = bpf_map_lookup_elem(attr_map_fd, &evsel->core.attr, &entry);
485 	if (err) {
486 		err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, &entry, BPF_ANY);
487 		if (err)
488 			goto out;
489 	}
490 
491 	evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry.link_id);
492 	if (evsel->bperf_leader_link_fd < 0 &&
493 	    bperf_reload_leader_program(evsel, attr_map_fd, &entry)) {
494 		err = -1;
495 		goto out;
496 	}
497 	/*
498 	 * The bpf_link holds reference to the leader program, and the
499 	 * leader program holds reference to the maps. Therefore, if
500 	 * link_id is valid, diff_map_id should also be valid.
501 	 */
502 	evsel->bperf_leader_prog_fd = bpf_prog_get_fd_by_id(
503 		bpf_link_get_prog_id(evsel->bperf_leader_link_fd));
504 	assert(evsel->bperf_leader_prog_fd >= 0);
505 
506 	diff_map_fd = bpf_map_get_fd_by_id(entry.diff_map_id);
507 	assert(diff_map_fd >= 0);
508 
509 	/*
510 	 * bperf uses BPF_PROG_TEST_RUN to get accurate reading. Check
511 	 * whether the kernel support it
512 	 */
513 	err = bperf_trigger_reading(evsel->bperf_leader_prog_fd, 0);
514 	if (err) {
515 		pr_err("The kernel does not support test_run for raw_tp BPF programs.\n"
516 		       "Therefore, --use-bpf might show inaccurate readings\n");
517 		goto out;
518 	}
519 
520 	/* Step 2: load the follower skeleton */
521 	evsel->follower_skel = bperf_follower_bpf__open();
522 	if (!evsel->follower_skel) {
523 		err = -1;
524 		pr_err("Failed to open follower skeleton\n");
525 		goto out;
526 	}
527 
528 	/* attach fexit program to the leader program */
529 	bpf_program__set_attach_target(evsel->follower_skel->progs.fexit_XXX,
530 				       evsel->bperf_leader_prog_fd, "on_switch");
531 
532 	/* connect to leader diff_reading map */
533 	bpf_map__reuse_fd(evsel->follower_skel->maps.diff_readings, diff_map_fd);
534 
535 	/* set up reading map */
536 	bpf_map__set_max_entries(evsel->follower_skel->maps.accum_readings,
537 				 filter_entry_cnt);
538 	/* set up follower filter based on target */
539 	bpf_map__set_max_entries(evsel->follower_skel->maps.filter,
540 				 filter_entry_cnt);
541 	err = bperf_follower_bpf__load(evsel->follower_skel);
542 	if (err) {
543 		pr_err("Failed to load follower skeleton\n");
544 		bperf_follower_bpf__destroy(evsel->follower_skel);
545 		evsel->follower_skel = NULL;
546 		goto out;
547 	}
548 
549 	for (i = 0; i < filter_entry_cnt; i++) {
550 		int filter_map_fd;
551 		__u32 key;
552 
553 		if (filter_type == BPERF_FILTER_PID ||
554 		    filter_type == BPERF_FILTER_TGID)
555 			key = evsel->core.threads->map[i].pid;
556 		else if (filter_type == BPERF_FILTER_CPU)
557 			key = evsel->core.cpus->map[i].cpu;
558 		else
559 			break;
560 
561 		filter_map_fd = bpf_map__fd(evsel->follower_skel->maps.filter);
562 		bpf_map_update_elem(filter_map_fd, &key, &i, BPF_ANY);
563 	}
564 
565 	evsel->follower_skel->bss->type = filter_type;
566 
567 	err = bperf_follower_bpf__attach(evsel->follower_skel);
568 
569 out:
570 	if (err && evsel->bperf_leader_link_fd >= 0)
571 		close(evsel->bperf_leader_link_fd);
572 	if (err && evsel->bperf_leader_prog_fd >= 0)
573 		close(evsel->bperf_leader_prog_fd);
574 	if (diff_map_fd >= 0)
575 		close(diff_map_fd);
576 
577 	flock(attr_map_fd, LOCK_UN);
578 	close(attr_map_fd);
579 
580 	return err;
581 }
582 
583 static int bperf__install_pe(struct evsel *evsel, int cpu_map_idx, int fd)
584 {
585 	struct bperf_leader_bpf *skel = evsel->leader_skel;
586 
587 	return bpf_map_update_elem(bpf_map__fd(skel->maps.events),
588 				   &cpu_map_idx, &fd, BPF_ANY);
589 }
590 
591 /*
592  * trigger the leader prog on each cpu, so the accum_reading map could get
593  * the latest readings.
594  */
595 static int bperf_sync_counters(struct evsel *evsel)
596 {
597 	int num_cpu, i, cpu;
598 
599 	num_cpu = all_cpu_map->nr;
600 	for (i = 0; i < num_cpu; i++) {
601 		cpu = all_cpu_map->map[i].cpu;
602 		bperf_trigger_reading(evsel->bperf_leader_prog_fd, cpu);
603 	}
604 	return 0;
605 }
606 
607 static int bperf__enable(struct evsel *evsel)
608 {
609 	evsel->follower_skel->bss->enabled = 1;
610 	return 0;
611 }
612 
613 static int bperf__disable(struct evsel *evsel)
614 {
615 	evsel->follower_skel->bss->enabled = 0;
616 	return 0;
617 }
618 
619 static int bperf__read(struct evsel *evsel)
620 {
621 	struct bperf_follower_bpf *skel = evsel->follower_skel;
622 	__u32 num_cpu_bpf = cpu__max_cpu().cpu;
623 	struct bpf_perf_event_value values[num_cpu_bpf];
624 	int reading_map_fd, err = 0;
625 	__u32 i;
626 	int j;
627 
628 	bperf_sync_counters(evsel);
629 	reading_map_fd = bpf_map__fd(skel->maps.accum_readings);
630 
631 	for (i = 0; i < bpf_map__max_entries(skel->maps.accum_readings); i++) {
632 		struct perf_cpu entry;
633 		__u32 cpu;
634 
635 		err = bpf_map_lookup_elem(reading_map_fd, &i, values);
636 		if (err)
637 			goto out;
638 		switch (evsel->follower_skel->bss->type) {
639 		case BPERF_FILTER_GLOBAL:
640 			assert(i == 0);
641 
642 			perf_cpu_map__for_each_cpu(entry, j, all_cpu_map) {
643 				cpu = entry.cpu;
644 				perf_counts(evsel->counts, cpu, 0)->val = values[cpu].counter;
645 				perf_counts(evsel->counts, cpu, 0)->ena = values[cpu].enabled;
646 				perf_counts(evsel->counts, cpu, 0)->run = values[cpu].running;
647 			}
648 			break;
649 		case BPERF_FILTER_CPU:
650 			cpu = evsel->core.cpus->map[i].cpu;
651 			perf_counts(evsel->counts, i, 0)->val = values[cpu].counter;
652 			perf_counts(evsel->counts, i, 0)->ena = values[cpu].enabled;
653 			perf_counts(evsel->counts, i, 0)->run = values[cpu].running;
654 			break;
655 		case BPERF_FILTER_PID:
656 		case BPERF_FILTER_TGID:
657 			perf_counts(evsel->counts, 0, i)->val = 0;
658 			perf_counts(evsel->counts, 0, i)->ena = 0;
659 			perf_counts(evsel->counts, 0, i)->run = 0;
660 
661 			for (cpu = 0; cpu < num_cpu_bpf; cpu++) {
662 				perf_counts(evsel->counts, 0, i)->val += values[cpu].counter;
663 				perf_counts(evsel->counts, 0, i)->ena += values[cpu].enabled;
664 				perf_counts(evsel->counts, 0, i)->run += values[cpu].running;
665 			}
666 			break;
667 		default:
668 			break;
669 		}
670 	}
671 out:
672 	return err;
673 }
674 
675 static int bperf__destroy(struct evsel *evsel)
676 {
677 	bperf_follower_bpf__destroy(evsel->follower_skel);
678 	close(evsel->bperf_leader_prog_fd);
679 	close(evsel->bperf_leader_link_fd);
680 	return 0;
681 }
682 
683 /*
684  * bperf: share hardware PMCs with BPF
685  *
686  * perf uses performance monitoring counters (PMC) to monitor system
687  * performance. The PMCs are limited hardware resources. For example,
688  * Intel CPUs have 3x fixed PMCs and 4x programmable PMCs per cpu.
689  *
690  * Modern data center systems use these PMCs in many different ways:
691  * system level monitoring, (maybe nested) container level monitoring, per
692  * process monitoring, profiling (in sample mode), etc. In some cases,
693  * there are more active perf_events than available hardware PMCs. To allow
694  * all perf_events to have a chance to run, it is necessary to do expensive
695  * time multiplexing of events.
696  *
697  * On the other hand, many monitoring tools count the common metrics
698  * (cycles, instructions). It is a waste to have multiple tools create
699  * multiple perf_events of "cycles" and occupy multiple PMCs.
700  *
701  * bperf tries to reduce such wastes by allowing multiple perf_events of
702  * "cycles" or "instructions" (at different scopes) to share PMUs. Instead
703  * of having each perf-stat session to read its own perf_events, bperf uses
704  * BPF programs to read the perf_events and aggregate readings to BPF maps.
705  * Then, the perf-stat session(s) reads the values from these BPF maps.
706  *
707  *                                ||
708  *       shared progs and maps <- || -> per session progs and maps
709  *                                ||
710  *   ---------------              ||
711  *   | perf_events |              ||
712  *   ---------------       fexit  ||      -----------------
713  *          |             --------||----> | follower prog |
714  *       --------------- /        || ---  -----------------
715  * cs -> | leader prog |/         ||/        |         |
716  *   --> ---------------         /||  --------------  ------------------
717  *  /       |         |         / ||  | filter map |  | accum_readings |
718  * /  ------------  ------------  ||  --------------  ------------------
719  * |  | prev map |  | diff map |  ||                        |
720  * |  ------------  ------------  ||                        |
721  *  \                             ||                        |
722  * = \ ==================================================== | ============
723  *    \                                                    /   user space
724  *     \                                                  /
725  *      \                                                /
726  *    BPF_PROG_TEST_RUN                    BPF_MAP_LOOKUP_ELEM
727  *        \                                            /
728  *         \                                          /
729  *          \------  perf-stat ----------------------/
730  *
731  * The figure above shows the architecture of bperf. Note that the figure
732  * is divided into 3 regions: shared progs and maps (top left), per session
733  * progs and maps (top right), and user space (bottom).
734  *
735  * The leader prog is triggered on each context switch (cs). The leader
736  * prog reads perf_events and stores the difference (current_reading -
737  * previous_reading) to the diff map. For the same metric, e.g. "cycles",
738  * multiple perf-stat sessions share the same leader prog.
739  *
740  * Each perf-stat session creates a follower prog as fexit program to the
741  * leader prog. It is possible to attach up to BPF_MAX_TRAMP_PROGS (38)
742  * follower progs to the same leader prog. The follower prog checks current
743  * task and processor ID to decide whether to add the value from the diff
744  * map to its accumulated reading map (accum_readings).
745  *
746  * Finally, perf-stat user space reads the value from accum_reading map.
747  *
748  * Besides context switch, it is also necessary to trigger the leader prog
749  * before perf-stat reads the value. Otherwise, the accum_reading map may
750  * not have the latest reading from the perf_events. This is achieved by
751  * triggering the event via sys_bpf(BPF_PROG_TEST_RUN) to each CPU.
752  *
753  * Comment before the definition of struct perf_event_attr_map_entry
754  * describes how different sessions of perf-stat share information about
755  * the leader prog.
756  */
757 
758 struct bpf_counter_ops bperf_ops = {
759 	.load       = bperf__load,
760 	.enable     = bperf__enable,
761 	.disable    = bperf__disable,
762 	.read       = bperf__read,
763 	.install_pe = bperf__install_pe,
764 	.destroy    = bperf__destroy,
765 };
766 
767 extern struct bpf_counter_ops bperf_cgrp_ops;
768 
769 static inline bool bpf_counter_skip(struct evsel *evsel)
770 {
771 	return list_empty(&evsel->bpf_counter_list) &&
772 		evsel->follower_skel == NULL;
773 }
774 
775 int bpf_counter__install_pe(struct evsel *evsel, int cpu_map_idx, int fd)
776 {
777 	if (bpf_counter_skip(evsel))
778 		return 0;
779 	return evsel->bpf_counter_ops->install_pe(evsel, cpu_map_idx, fd);
780 }
781 
782 int bpf_counter__load(struct evsel *evsel, struct target *target)
783 {
784 	if (target->bpf_str)
785 		evsel->bpf_counter_ops = &bpf_program_profiler_ops;
786 	else if (cgrp_event_expanded && target->use_bpf)
787 		evsel->bpf_counter_ops = &bperf_cgrp_ops;
788 	else if (target->use_bpf || evsel->bpf_counter ||
789 		 evsel__match_bpf_counter_events(evsel->name))
790 		evsel->bpf_counter_ops = &bperf_ops;
791 
792 	if (evsel->bpf_counter_ops)
793 		return evsel->bpf_counter_ops->load(evsel, target);
794 	return 0;
795 }
796 
797 int bpf_counter__enable(struct evsel *evsel)
798 {
799 	if (bpf_counter_skip(evsel))
800 		return 0;
801 	return evsel->bpf_counter_ops->enable(evsel);
802 }
803 
804 int bpf_counter__disable(struct evsel *evsel)
805 {
806 	if (bpf_counter_skip(evsel))
807 		return 0;
808 	return evsel->bpf_counter_ops->disable(evsel);
809 }
810 
811 int bpf_counter__read(struct evsel *evsel)
812 {
813 	if (bpf_counter_skip(evsel))
814 		return -EAGAIN;
815 	return evsel->bpf_counter_ops->read(evsel);
816 }
817 
818 void bpf_counter__destroy(struct evsel *evsel)
819 {
820 	if (bpf_counter_skip(evsel))
821 		return;
822 	evsel->bpf_counter_ops->destroy(evsel);
823 	evsel->bpf_counter_ops = NULL;
824 }
825