xref: /linux/tools/lib/perf/mmap.c (revision 811f35ff59b6f99ae272d6f5b96bc9e974f88196) 
1 // SPDX-License-Identifier: GPL-2.0
2 #include <sys/mman.h>
3 #include <inttypes.h>
4 #include <asm/bug.h>
5 #include <errno.h>
6 #include <string.h>
7 #include <linux/ring_buffer.h>
8 #include <linux/perf_event.h>
9 #include <perf/mmap.h>
10 #include <perf/event.h>
11 #include <perf/evsel.h>
12 #include <internal/mmap.h>
13 #include <internal/lib.h>
14 #include <linux/kernel.h>
15 #include <linux/math64.h>
16 #include <linux/stringify.h>
17 #include "internal.h"
18 
19 void perf_mmap__init(struct perf_mmap *map, struct perf_mmap *prev,
20 		     bool overwrite, libperf_unmap_cb_t unmap_cb)
21 {
22 	map->fd = -1;
23 	map->overwrite = overwrite;
24 	map->unmap_cb  = unmap_cb;
25 	refcount_set(&map->refcnt, 0);
26 	if (prev)
27 		prev->next = map;
28 }
29 
30 size_t perf_mmap__mmap_len(struct perf_mmap *map)
31 {
32 	return map->mask + 1 + page_size;
33 }
34 
35 int perf_mmap__mmap(struct perf_mmap *map, struct perf_mmap_param *mp,
36 		    int fd, struct perf_cpu cpu)
37 {
38 	map->prev = 0;
39 	map->mask = mp->mask;
40 	map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
41 			 MAP_SHARED, fd, 0);
42 	if (map->base == MAP_FAILED) {
43 		map->base = NULL;
44 		return -1;
45 	}
46 
47 	map->fd  = fd;
48 	map->cpu = cpu;
49 	return 0;
50 }
51 
52 void perf_mmap__munmap(struct perf_mmap *map)
53 {
54 	if (map && map->base != NULL) {
55 		munmap(map->base, perf_mmap__mmap_len(map));
56 		map->base = NULL;
57 		map->fd = -1;
58 		refcount_set(&map->refcnt, 0);
59 	}
60 	if (map && map->unmap_cb)
61 		map->unmap_cb(map);
62 }
63 
64 void perf_mmap__get(struct perf_mmap *map)
65 {
66 	refcount_inc(&map->refcnt);
67 }
68 
69 void perf_mmap__put(struct perf_mmap *map)
70 {
71 	BUG_ON(map->base && refcount_read(&map->refcnt) == 0);
72 
73 	if (refcount_dec_and_test(&map->refcnt))
74 		perf_mmap__munmap(map);
75 }
76 
77 static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
78 {
79 	ring_buffer_write_tail(md->base, tail);
80 }
81 
82 u64 perf_mmap__read_head(struct perf_mmap *map)
83 {
84 	return ring_buffer_read_head(map->base);
85 }
86 
87 static bool perf_mmap__empty(struct perf_mmap *map)
88 {
89 	struct perf_event_mmap_page *pc = map->base;
90 
91 	return perf_mmap__read_head(map) == map->prev && !pc->aux_size;
92 }
93 
94 void perf_mmap__consume(struct perf_mmap *map)
95 {
96 	if (!map->overwrite) {
97 		u64 old = map->prev;
98 
99 		perf_mmap__write_tail(map, old);
100 	}
101 
102 	if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map))
103 		perf_mmap__put(map);
104 }
105 
106 static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
107 {
108 	struct perf_event_header *pheader;
109 	u64 evt_head = *start;
110 	int size = mask + 1;
111 
112 	pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);
113 	pheader = (struct perf_event_header *)(buf + (*start & mask));
114 	while (true) {
115 		if (evt_head - *start >= (unsigned int)size) {
116 			pr_debug("Finished reading overwrite ring buffer: rewind\n");
117 			if (evt_head - *start > (unsigned int)size)
118 				evt_head -= pheader->size;
119 			*end = evt_head;
120 			return 0;
121 		}
122 
123 		pheader = (struct perf_event_header *)(buf + (evt_head & mask));
124 
125 		if (pheader->size == 0) {
126 			pr_debug("Finished reading overwrite ring buffer: get start\n");
127 			*end = evt_head;
128 			return 0;
129 		}
130 
131 		evt_head += pheader->size;
132 		pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
133 	}
134 	WARN_ONCE(1, "Shouldn't get here\n");
135 	return -1;
136 }
137 
138 /*
139  * Report the start and end of the available data in ringbuffer
140  */
141 static int __perf_mmap__read_init(struct perf_mmap *md)
142 {
143 	u64 head = perf_mmap__read_head(md);
144 	u64 old = md->prev;
145 	unsigned char *data = md->base + page_size;
146 	unsigned long size;
147 
148 	md->start = md->overwrite ? head : old;
149 	md->end = md->overwrite ? old : head;
150 
151 	if ((md->end - md->start) < md->flush)
152 		return -EAGAIN;
153 
154 	size = md->end - md->start;
155 	if (size > (unsigned long)(md->mask) + 1) {
156 		if (!md->overwrite) {
157 			WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
158 
159 			md->prev = head;
160 			perf_mmap__consume(md);
161 			return -EAGAIN;
162 		}
163 
164 		/*
165 		 * Backward ring buffer is full. We still have a chance to read
166 		 * most of data from it.
167 		 */
168 		if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))
169 			return -EINVAL;
170 	}
171 
172 	return 0;
173 }
174 
175 int perf_mmap__read_init(struct perf_mmap *map)
176 {
177 	/*
178 	 * Check if event was unmapped due to a POLLHUP/POLLERR.
179 	 */
180 	if (!refcount_read(&map->refcnt))
181 		return -ENOENT;
182 
183 	return __perf_mmap__read_init(map);
184 }
185 
186 /*
187  * Mandatory for overwrite mode
188  * The direction of overwrite mode is backward.
189  * The last perf_mmap__read() will set tail to map->core.prev.
190  * Need to correct the map->core.prev to head which is the end of next read.
191  */
192 void perf_mmap__read_done(struct perf_mmap *map)
193 {
194 	/*
195 	 * Check if event was unmapped due to a POLLHUP/POLLERR.
196 	 */
197 	if (!refcount_read(&map->refcnt))
198 		return;
199 
200 	map->prev = perf_mmap__read_head(map);
201 }
202 
203 /* When check_messup is true, 'end' must points to a good entry */
204 static union perf_event *perf_mmap__read(struct perf_mmap *map,
205 					 u64 *startp, u64 end)
206 {
207 	unsigned char *data = map->base + page_size;
208 	union perf_event *event = NULL;
209 	int diff = end - *startp;
210 
211 	if (diff >= (int)sizeof(event->header)) {
212 		size_t size;
213 
214 		event = (union perf_event *)&data[*startp & map->mask];
215 		size = event->header.size;
216 
217 		if (size < sizeof(event->header) || diff < (int)size)
218 			return NULL;
219 
220 		/*
221 		 * Event straddles the mmap boundary -- header should always
222 		 * be inside due to u64 alignment of output.
223 		 */
224 		if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
225 			unsigned int offset = *startp;
226 			unsigned int len = min(sizeof(*event), size), cpy;
227 			void *dst = map->event_copy;
228 
229 			do {
230 				cpy = min(map->mask + 1 - (offset & map->mask), len);
231 				memcpy(dst, &data[offset & map->mask], cpy);
232 				offset += cpy;
233 				dst += cpy;
234 				len -= cpy;
235 			} while (len);
236 
237 			event = (union perf_event *)map->event_copy;
238 		}
239 
240 		*startp += size;
241 	}
242 
243 	return event;
244 }
245 
246 /*
247  * Read event from ring buffer one by one.
248  * Return one event for each call.
249  *
250  * Usage:
251  * perf_mmap__read_init()
252  * while(event = perf_mmap__read_event()) {
253  *	//process the event
254  *	perf_mmap__consume()
255  * }
256  * perf_mmap__read_done()
257  */
258 union perf_event *perf_mmap__read_event(struct perf_mmap *map)
259 {
260 	union perf_event *event;
261 
262 	/*
263 	 * Check if event was unmapped due to a POLLHUP/POLLERR.
264 	 */
265 	if (!refcount_read(&map->refcnt))
266 		return NULL;
267 
268 	/* non-overwirte doesn't pause the ringbuffer */
269 	if (!map->overwrite)
270 		map->end = perf_mmap__read_head(map);
271 
272 	event = perf_mmap__read(map, &map->start, map->end);
273 
274 	if (!map->overwrite)
275 		map->prev = map->start;
276 
277 	return event;
278 }
279 
280 #if defined(__i386__) || defined(__x86_64__)
281 static u64 read_perf_counter(unsigned int counter)
282 {
283 	unsigned int low, high;
284 
285 	asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));
286 
287 	return low | ((u64)high) << 32;
288 }
289 
290 static u64 read_timestamp(void)
291 {
292 	unsigned int low, high;
293 
294 	asm volatile("rdtsc" : "=a" (low), "=d" (high));
295 
296 	return low | ((u64)high) << 32;
297 }
298 #elif defined(__aarch64__)
299 #define read_sysreg(r) ({						\
300 	u64 __val;							\
301 	asm volatile("mrs %0, " __stringify(r) : "=r" (__val));		\
302 	__val;								\
303 })
304 
305 static u64 read_pmccntr(void)
306 {
307 	return read_sysreg(pmccntr_el0);
308 }
309 
310 #define PMEVCNTR_READ(idx)					\
311 	static u64 read_pmevcntr_##idx(void) {			\
312 		return read_sysreg(pmevcntr##idx##_el0);	\
313 	}
314 
315 PMEVCNTR_READ(0);
316 PMEVCNTR_READ(1);
317 PMEVCNTR_READ(2);
318 PMEVCNTR_READ(3);
319 PMEVCNTR_READ(4);
320 PMEVCNTR_READ(5);
321 PMEVCNTR_READ(6);
322 PMEVCNTR_READ(7);
323 PMEVCNTR_READ(8);
324 PMEVCNTR_READ(9);
325 PMEVCNTR_READ(10);
326 PMEVCNTR_READ(11);
327 PMEVCNTR_READ(12);
328 PMEVCNTR_READ(13);
329 PMEVCNTR_READ(14);
330 PMEVCNTR_READ(15);
331 PMEVCNTR_READ(16);
332 PMEVCNTR_READ(17);
333 PMEVCNTR_READ(18);
334 PMEVCNTR_READ(19);
335 PMEVCNTR_READ(20);
336 PMEVCNTR_READ(21);
337 PMEVCNTR_READ(22);
338 PMEVCNTR_READ(23);
339 PMEVCNTR_READ(24);
340 PMEVCNTR_READ(25);
341 PMEVCNTR_READ(26);
342 PMEVCNTR_READ(27);
343 PMEVCNTR_READ(28);
344 PMEVCNTR_READ(29);
345 PMEVCNTR_READ(30);
346 
347 /*
348  * Read a value direct from PMEVCNTR<idx>
349  */
350 static u64 read_perf_counter(unsigned int counter)
351 {
352 	static u64 (* const read_f[])(void) = {
353 		read_pmevcntr_0,
354 		read_pmevcntr_1,
355 		read_pmevcntr_2,
356 		read_pmevcntr_3,
357 		read_pmevcntr_4,
358 		read_pmevcntr_5,
359 		read_pmevcntr_6,
360 		read_pmevcntr_7,
361 		read_pmevcntr_8,
362 		read_pmevcntr_9,
363 		read_pmevcntr_10,
364 		read_pmevcntr_11,
365 		read_pmevcntr_13,
366 		read_pmevcntr_12,
367 		read_pmevcntr_14,
368 		read_pmevcntr_15,
369 		read_pmevcntr_16,
370 		read_pmevcntr_17,
371 		read_pmevcntr_18,
372 		read_pmevcntr_19,
373 		read_pmevcntr_20,
374 		read_pmevcntr_21,
375 		read_pmevcntr_22,
376 		read_pmevcntr_23,
377 		read_pmevcntr_24,
378 		read_pmevcntr_25,
379 		read_pmevcntr_26,
380 		read_pmevcntr_27,
381 		read_pmevcntr_28,
382 		read_pmevcntr_29,
383 		read_pmevcntr_30,
384 		read_pmccntr
385 	};
386 
387 	if (counter < ARRAY_SIZE(read_f))
388 		return (read_f[counter])();
389 
390 	return 0;
391 }
392 
393 static u64 read_timestamp(void) { return read_sysreg(cntvct_el0); }
394 
395 #else
396 static u64 read_perf_counter(unsigned int counter __maybe_unused) { return 0; }
397 static u64 read_timestamp(void) { return 0; }
398 #endif
399 
400 int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count)
401 {
402 	struct perf_event_mmap_page *pc = map->base;
403 	u32 seq, idx, time_mult = 0, time_shift = 0;
404 	u64 cnt, cyc = 0, time_offset = 0, time_cycles = 0, time_mask = ~0ULL;
405 
406 	if (!pc || !pc->cap_user_rdpmc)
407 		return -1;
408 
409 	do {
410 		seq = READ_ONCE(pc->lock);
411 		barrier();
412 
413 		count->ena = READ_ONCE(pc->time_enabled);
414 		count->run = READ_ONCE(pc->time_running);
415 
416 		if (pc->cap_user_time && count->ena != count->run) {
417 			cyc = read_timestamp();
418 			time_mult = READ_ONCE(pc->time_mult);
419 			time_shift = READ_ONCE(pc->time_shift);
420 			time_offset = READ_ONCE(pc->time_offset);
421 
422 			if (pc->cap_user_time_short) {
423 				time_cycles = READ_ONCE(pc->time_cycles);
424 				time_mask = READ_ONCE(pc->time_mask);
425 			}
426 		}
427 
428 		idx = READ_ONCE(pc->index);
429 		cnt = READ_ONCE(pc->offset);
430 		if (pc->cap_user_rdpmc && idx) {
431 			s64 evcnt = read_perf_counter(idx - 1);
432 			u16 width = READ_ONCE(pc->pmc_width);
433 
434 			evcnt <<= 64 - width;
435 			evcnt >>= 64 - width;
436 			cnt += evcnt;
437 		} else
438 			return -1;
439 
440 		barrier();
441 	} while (READ_ONCE(pc->lock) != seq);
442 
443 	if (count->ena != count->run) {
444 		u64 delta;
445 
446 		/* Adjust for cap_usr_time_short, a nop if not */
447 		cyc = time_cycles + ((cyc - time_cycles) & time_mask);
448 
449 		delta = time_offset + mul_u64_u32_shr(cyc, time_mult, time_shift);
450 
451 		count->ena += delta;
452 		if (idx)
453 			count->run += delta;
454 	}
455 
456 	count->val = cnt;
457 
458 	return 0;
459 }
460