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1/*
2 * Copyright (C) 2011-2017, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
3 *
4 * Parts came from evlist.c builtin-{top,stat,record}.c, see those files for further
5 * copyright notes.
6 *
7 * Released under the GPL v2. (and only v2, not any later version)
8 */
9
10#include <sys/mman.h>
11#include <inttypes.h>
12#include <asm/bug.h>
13#include "debug.h"
14#include "event.h"
15#include "mmap.h"
16#include "util.h" /* page_size */
17
18size_t perf_mmap__mmap_len(struct perf_mmap *map)
19{
20 return map->mask + 1 + page_size;
21}
22
23/* When check_messup is true, 'end' must points to a good entry */
24static union perf_event *perf_mmap__read(struct perf_mmap *map,
25 u64 *startp, u64 end)
26{
27 unsigned char *data = map->base + page_size;
28 union perf_event *event = NULL;
29 int diff = end - *startp;
30
31 if (diff >= (int)sizeof(event->header)) {
32 size_t size;
33
34 event = (union perf_event *)&data[*startp & map->mask];
35 size = event->header.size;
36
37 if (size < sizeof(event->header) || diff < (int)size)
38 return NULL;
39
40 /*
41 * Event straddles the mmap boundary -- header should always
42 * be inside due to u64 alignment of output.
43 */
44 if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
45 unsigned int offset = *startp;
46 unsigned int len = min(sizeof(*event), size), cpy;
47 void *dst = map->event_copy;
48
49 do {
50 cpy = min(map->mask + 1 - (offset & map->mask), len);
51 memcpy(dst, &data[offset & map->mask], cpy);
52 offset += cpy;
53 dst += cpy;
54 len -= cpy;
55 } while (len);
56
57 event = (union perf_event *)map->event_copy;
58 }
59
60 *startp += size;
61 }
62
63 return event;
64}
65
66/*
67 * Read event from ring buffer one by one.
68 * Return one event for each call.
69 *
70 * Usage:
71 * perf_mmap__read_init()
72 * while(event = perf_mmap__read_event()) {
73 * //process the event
74 * perf_mmap__consume()
75 * }
76 * perf_mmap__read_done()
77 */
78union perf_event *perf_mmap__read_event(struct perf_mmap *map)
79{
80 union perf_event *event;
81
82 /*
83 * Check if event was unmapped due to a POLLHUP/POLLERR.
84 */
85 if (!refcount_read(&map->refcnt))
86 return NULL;
87
88 /* non-overwirte doesn't pause the ringbuffer */
89 if (!map->overwrite)
90 map->end = perf_mmap__read_head(map);
91
92 event = perf_mmap__read(map, &map->start, map->end);
93
94 if (!map->overwrite)
95 map->prev = map->start;
96
97 return event;
98}
99
100static bool perf_mmap__empty(struct perf_mmap *map)
101{
102 return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base;
103}
104
105void perf_mmap__get(struct perf_mmap *map)
106{
107 refcount_inc(&map->refcnt);
108}
109
110void perf_mmap__put(struct perf_mmap *map)
111{
112 BUG_ON(map->base && refcount_read(&map->refcnt) == 0);
113
114 if (refcount_dec_and_test(&map->refcnt))
115 perf_mmap__munmap(map);
116}
117
118void perf_mmap__consume(struct perf_mmap *map)
119{
120 if (!map->overwrite) {
121 u64 old = map->prev;
122
123 perf_mmap__write_tail(map, old);
124 }
125
126 if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map))
127 perf_mmap__put(map);
128}
129
130int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused,
131 struct auxtrace_mmap_params *mp __maybe_unused,
132 void *userpg __maybe_unused,
133 int fd __maybe_unused)
134{
135 return 0;
136}
137
138void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused)
139{
140}
141
142void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused,
143 off_t auxtrace_offset __maybe_unused,
144 unsigned int auxtrace_pages __maybe_unused,
145 bool auxtrace_overwrite __maybe_unused)
146{
147}
148
149void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused,
150 struct perf_evlist *evlist __maybe_unused,
151 int idx __maybe_unused,
152 bool per_cpu __maybe_unused)
153{
154}
155
156void perf_mmap__munmap(struct perf_mmap *map)
157{
158 if (map->base != NULL) {
159 munmap(map->base, perf_mmap__mmap_len(map));
160 map->base = NULL;
161 map->fd = -1;
162 refcount_set(&map->refcnt, 0);
163 }
164 auxtrace_mmap__munmap(&map->auxtrace_mmap);
165}
166
167int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
168{
169 /*
170 * The last one will be done at perf_mmap__consume(), so that we
171 * make sure we don't prevent tools from consuming every last event in
172 * the ring buffer.
173 *
174 * I.e. we can get the POLLHUP meaning that the fd doesn't exist
175 * anymore, but the last events for it are still in the ring buffer,
176 * waiting to be consumed.
177 *
178 * Tools can chose to ignore this at their own discretion, but the
179 * evlist layer can't just drop it when filtering events in
180 * perf_evlist__filter_pollfd().
181 */
182 refcount_set(&map->refcnt, 2);
183 map->prev = 0;
184 map->mask = mp->mask;
185 map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
186 MAP_SHARED, fd, 0);
187 if (map->base == MAP_FAILED) {
188 pr_debug2("failed to mmap perf event ring buffer, error %d\n",
189 errno);
190 map->base = NULL;
191 return -1;
192 }
193 map->fd = fd;
194
195 if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
196 &mp->auxtrace_mp, map->base, fd))
197 return -1;
198
199 return 0;
200}
201
202static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
203{
204 struct perf_event_header *pheader;
205 u64 evt_head = *start;
206 int size = mask + 1;
207
208 pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);
209 pheader = (struct perf_event_header *)(buf + (*start & mask));
210 while (true) {
211 if (evt_head - *start >= (unsigned int)size) {
212 pr_debug("Finished reading overwrite ring buffer: rewind\n");
213 if (evt_head - *start > (unsigned int)size)
214 evt_head -= pheader->size;
215 *end = evt_head;
216 return 0;
217 }
218
219 pheader = (struct perf_event_header *)(buf + (evt_head & mask));
220
221 if (pheader->size == 0) {
222 pr_debug("Finished reading overwrite ring buffer: get start\n");
223 *end = evt_head;
224 return 0;
225 }
226
227 evt_head += pheader->size;
228 pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
229 }
230 WARN_ONCE(1, "Shouldn't get here\n");
231 return -1;
232}
233
234/*
235 * Report the start and end of the available data in ringbuffer
236 */
237static int __perf_mmap__read_init(struct perf_mmap *md)
238{
239 u64 head = perf_mmap__read_head(md);
240 u64 old = md->prev;
241 unsigned char *data = md->base + page_size;
242 unsigned long size;
243
244 md->start = md->overwrite ? head : old;
245 md->end = md->overwrite ? old : head;
246
247 if (md->start == md->end)
248 return -EAGAIN;
249
250 size = md->end - md->start;
251 if (size > (unsigned long)(md->mask) + 1) {
252 if (!md->overwrite) {
253 WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
254
255 md->prev = head;
256 perf_mmap__consume(md);
257 return -EAGAIN;
258 }
259
260 /*
261 * Backward ring buffer is full. We still have a chance to read
262 * most of data from it.
263 */
264 if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))
265 return -EINVAL;
266 }
267
268 return 0;
269}
270
271int perf_mmap__read_init(struct perf_mmap *map)
272{
273 /*
274 * Check if event was unmapped due to a POLLHUP/POLLERR.
275 */
276 if (!refcount_read(&map->refcnt))
277 return -ENOENT;
278
279 return __perf_mmap__read_init(map);
280}
281
282int perf_mmap__push(struct perf_mmap *md, void *to,
283 int push(void *to, void *buf, size_t size))
284{
285 u64 head = perf_mmap__read_head(md);
286 unsigned char *data = md->base + page_size;
287 unsigned long size;
288 void *buf;
289 int rc = 0;
290
291 rc = perf_mmap__read_init(md);
292 if (rc < 0)
293 return (rc == -EAGAIN) ? 0 : -1;
294
295 size = md->end - md->start;
296
297 if ((md->start & md->mask) + size != (md->end & md->mask)) {
298 buf = &data[md->start & md->mask];
299 size = md->mask + 1 - (md->start & md->mask);
300 md->start += size;
301
302 if (push(to, buf, size) < 0) {
303 rc = -1;
304 goto out;
305 }
306 }
307
308 buf = &data[md->start & md->mask];
309 size = md->end - md->start;
310 md->start += size;
311
312 if (push(to, buf, size) < 0) {
313 rc = -1;
314 goto out;
315 }
316
317 md->prev = head;
318 perf_mmap__consume(md);
319out:
320 return rc;
321}
322
323/*
324 * Mandatory for overwrite mode
325 * The direction of overwrite mode is backward.
326 * The last perf_mmap__read() will set tail to map->prev.
327 * Need to correct the map->prev to head which is the end of next read.
328 */
329void perf_mmap__read_done(struct perf_mmap *map)
330{
331 /*
332 * Check if event was unmapped due to a POLLHUP/POLLERR.
333 */
334 if (!refcount_read(&map->refcnt))
335 return;
336
337 map->prev = perf_mmap__read_head(map);
338}