aboutsummaryrefslogtreecommitdiff
path: root/tools/lib/perf/mmap.c
blob: 79d5ed6c38cc524243ae77f918e213a20b3d6340 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
// SPDX-License-Identifier: GPL-2.0
#include <sys/mman.h>
#include <inttypes.h>
#include <asm/bug.h>
#include <errno.h>
#include <string.h>
#include <linux/ring_buffer.h>
#include <linux/perf_event.h>
#include <perf/mmap.h>
#include <perf/event.h>
#include <internal/mmap.h>
#include <internal/lib.h>
#include <linux/kernel.h>
#include "internal.h"

void perf_mmap__init(struct perf_mmap *map, struct perf_mmap *prev,
		     bool overwrite, libperf_unmap_cb_t unmap_cb)
{
	map->fd = -1;
	map->overwrite = overwrite;
	map->unmap_cb  = unmap_cb;
	refcount_set(&map->refcnt, 0);
	if (prev)
		prev->next = map;
}

size_t perf_mmap__mmap_len(struct perf_mmap *map)
{
	return map->mask + 1 + page_size;
}

int perf_mmap__mmap(struct perf_mmap *map, struct perf_mmap_param *mp,
		    int fd, int cpu)
{
	map->prev = 0;
	map->mask = mp->mask;
	map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
			 MAP_SHARED, fd, 0);
	if (map->base == MAP_FAILED) {
		map->base = NULL;
		return -1;
	}

	map->fd  = fd;
	map->cpu = cpu;
	return 0;
}

void perf_mmap__munmap(struct perf_mmap *map)
{
	if (map && map->base != NULL) {
		munmap(map->base, perf_mmap__mmap_len(map));
		map->base = NULL;
		map->fd = -1;
		refcount_set(&map->refcnt, 0);
	}
	if (map && map->unmap_cb)
		map->unmap_cb(map);
}

void perf_mmap__get(struct perf_mmap *map)
{
	refcount_inc(&map->refcnt);
}

void perf_mmap__put(struct perf_mmap *map)
{
	BUG_ON(map->base && refcount_read(&map->refcnt) == 0);

	if (refcount_dec_and_test(&map->refcnt))
		perf_mmap__munmap(map);
}

static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
{
	ring_buffer_write_tail(md->base, tail);
}

u64 perf_mmap__read_head(struct perf_mmap *map)
{
	return ring_buffer_read_head(map->base);
}

static bool perf_mmap__empty(struct perf_mmap *map)
{
	struct perf_event_mmap_page *pc = map->base;

	return perf_mmap__read_head(map) == map->prev && !pc->aux_size;
}

void perf_mmap__consume(struct perf_mmap *map)
{
	if (!map->overwrite) {
		u64 old = map->prev;

		perf_mmap__write_tail(map, old);
	}

	if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map))
		perf_mmap__put(map);
}

static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
{
	struct perf_event_header *pheader;
	u64 evt_head = *start;
	int size = mask + 1;

	pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);
	pheader = (struct perf_event_header *)(buf + (*start & mask));
	while (true) {
		if (evt_head - *start >= (unsigned int)size) {
			pr_debug("Finished reading overwrite ring buffer: rewind\n");
			if (evt_head - *start > (unsigned int)size)
				evt_head -= pheader->size;
			*end = evt_head;
			return 0;
		}

		pheader = (struct perf_event_header *)(buf + (evt_head & mask));

		if (pheader->size == 0) {
			pr_debug("Finished reading overwrite ring buffer: get start\n");
			*end = evt_head;
			return 0;
		}

		evt_head += pheader->size;
		pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
	}
	WARN_ONCE(1, "Shouldn't get here\n");
	return -1;
}

/*
 * Report the start and end of the available data in ringbuffer
 */
static int __perf_mmap__read_init(struct perf_mmap *md)
{
	u64 head = perf_mmap__read_head(md);
	u64 old = md->prev;
	unsigned char *data = md->base + page_size;
	unsigned long size;

	md->start = md->overwrite ? head : old;
	md->end = md->overwrite ? old : head;

	if ((md->end - md->start) < md->flush)
		return -EAGAIN;

	size = md->end - md->start;
	if (size > (unsigned long)(md->mask) + 1) {
		if (!md->overwrite) {
			WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");

			md->prev = head;
			perf_mmap__consume(md);
			return -EAGAIN;
		}

		/*
		 * Backward ring buffer is full. We still have a chance to read
		 * most of data from it.
		 */
		if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))
			return -EINVAL;
	}

	return 0;
}

int perf_mmap__read_init(struct perf_mmap *map)
{
	/*
	 * Check if event was unmapped due to a POLLHUP/POLLERR.
	 */
	if (!refcount_read(&map->refcnt))
		return -ENOENT;

	return __perf_mmap__read_init(map);
}

/*
 * Mandatory for overwrite mode
 * The direction of overwrite mode is backward.
 * The last perf_mmap__read() will set tail to map->core.prev.
 * Need to correct the map->core.prev to head which is the end of next read.
 */
void perf_mmap__read_done(struct perf_mmap *map)
{
	/*
	 * Check if event was unmapped due to a POLLHUP/POLLERR.
	 */
	if (!refcount_read(&map->refcnt))
		return;

	map->prev = perf_mmap__read_head(map);
}

/* When check_messup is true, 'end' must points to a good entry */
static union perf_event *perf_mmap__read(struct perf_mmap *map,
					 u64 *startp, u64 end)
{
	unsigned char *data = map->base + page_size;
	union perf_event *event = NULL;
	int diff = end - *startp;

	if (diff >= (int)sizeof(event->header)) {
		size_t size;

		event = (union perf_event *)&data[*startp & map->mask];
		size = event->header.size;

		if (size < sizeof(event->header) || diff < (int)size)
			return NULL;

		/*
		 * Event straddles the mmap boundary -- header should always
		 * be inside due to u64 alignment of output.
		 */
		if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
			unsigned int offset = *startp;
			unsigned int len = min(sizeof(*event), size), cpy;
			void *dst = map->event_copy;

			do {
				cpy = min(map->mask + 1 - (offset & map->mask), len);
				memcpy(dst, &data[offset & map->mask], cpy);
				offset += cpy;
				dst += cpy;
				len -= cpy;
			} while (len);

			event = (union perf_event *)map->event_copy;
		}

		*startp += size;
	}

	return event;
}

/*
 * Read event from ring buffer one by one.
 * Return one event for each call.
 *
 * Usage:
 * perf_mmap__read_init()
 * while(event = perf_mmap__read_event()) {
 *	//process the event
 *	perf_mmap__consume()
 * }
 * perf_mmap__read_done()
 */
union perf_event *perf_mmap__read_event(struct perf_mmap *map)
{
	union perf_event *event;

	/*
	 * Check if event was unmapped due to a POLLHUP/POLLERR.
	 */
	if (!refcount_read(&map->refcnt))
		return NULL;

	/* non-overwirte doesn't pause the ringbuffer */
	if (!map->overwrite)
		map->end = perf_mmap__read_head(map);

	event = perf_mmap__read(map, &map->start, map->end);

	if (!map->overwrite)
		map->prev = map->start;

	return event;
}