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 18 size_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 */ 24 static 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 * legacy interface for mmap read. 68 * Don't use it. Use perf_mmap__read_event(). 69 */ 70 union perf_event *perf_mmap__read_forward(struct perf_mmap *map) 71 { 72 u64 head; 73 74 /* 75 * Check if event was unmapped due to a POLLHUP/POLLERR. 76 */ 77 if (!refcount_read(&map->refcnt)) 78 return NULL; 79 80 head = perf_mmap__read_head(map); 81 82 return perf_mmap__read(map, &map->prev, head); 83 } 84 85 /* 86 * Read event from ring buffer one by one. 87 * Return one event for each call. 88 * 89 * Usage: 90 * perf_mmap__read_init() 91 * while(event = perf_mmap__read_event()) { 92 * //process the event 93 * perf_mmap__consume() 94 * } 95 * perf_mmap__read_done() 96 */ 97 union perf_event *perf_mmap__read_event(struct perf_mmap *map, 98 bool overwrite, 99 u64 *startp, u64 end) 100 { 101 union perf_event *event; 102 103 /* 104 * Check if event was unmapped due to a POLLHUP/POLLERR. 105 */ 106 if (!refcount_read(&map->refcnt)) 107 return NULL; 108 109 if (startp == NULL) 110 return NULL; 111 112 /* non-overwirte doesn't pause the ringbuffer */ 113 if (!overwrite) 114 end = perf_mmap__read_head(map); 115 116 event = perf_mmap__read(map, startp, end); 117 118 if (!overwrite) 119 map->prev = *startp; 120 121 return event; 122 } 123 124 static bool perf_mmap__empty(struct perf_mmap *map) 125 { 126 return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base; 127 } 128 129 void perf_mmap__get(struct perf_mmap *map) 130 { 131 refcount_inc(&map->refcnt); 132 } 133 134 void perf_mmap__put(struct perf_mmap *map) 135 { 136 BUG_ON(map->base && refcount_read(&map->refcnt) == 0); 137 138 if (refcount_dec_and_test(&map->refcnt)) 139 perf_mmap__munmap(map); 140 } 141 142 void perf_mmap__consume(struct perf_mmap *map, bool overwrite) 143 { 144 if (!overwrite) { 145 u64 old = map->prev; 146 147 perf_mmap__write_tail(map, old); 148 } 149 150 if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map)) 151 perf_mmap__put(map); 152 } 153 154 int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused, 155 struct auxtrace_mmap_params *mp __maybe_unused, 156 void *userpg __maybe_unused, 157 int fd __maybe_unused) 158 { 159 return 0; 160 } 161 162 void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused) 163 { 164 } 165 166 void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused, 167 off_t auxtrace_offset __maybe_unused, 168 unsigned int auxtrace_pages __maybe_unused, 169 bool auxtrace_overwrite __maybe_unused) 170 { 171 } 172 173 void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused, 174 struct perf_evlist *evlist __maybe_unused, 175 int idx __maybe_unused, 176 bool per_cpu __maybe_unused) 177 { 178 } 179 180 void perf_mmap__munmap(struct perf_mmap *map) 181 { 182 if (map->base != NULL) { 183 munmap(map->base, perf_mmap__mmap_len(map)); 184 map->base = NULL; 185 map->fd = -1; 186 refcount_set(&map->refcnt, 0); 187 } 188 auxtrace_mmap__munmap(&map->auxtrace_mmap); 189 } 190 191 int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd) 192 { 193 /* 194 * The last one will be done at perf_evlist__mmap_consume(), so that we 195 * make sure we don't prevent tools from consuming every last event in 196 * the ring buffer. 197 * 198 * I.e. we can get the POLLHUP meaning that the fd doesn't exist 199 * anymore, but the last events for it are still in the ring buffer, 200 * waiting to be consumed. 201 * 202 * Tools can chose to ignore this at their own discretion, but the 203 * evlist layer can't just drop it when filtering events in 204 * perf_evlist__filter_pollfd(). 205 */ 206 refcount_set(&map->refcnt, 2); 207 map->prev = 0; 208 map->mask = mp->mask; 209 map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot, 210 MAP_SHARED, fd, 0); 211 if (map->base == MAP_FAILED) { 212 pr_debug2("failed to mmap perf event ring buffer, error %d\n", 213 errno); 214 map->base = NULL; 215 return -1; 216 } 217 map->fd = fd; 218 219 if (auxtrace_mmap__mmap(&map->auxtrace_mmap, 220 &mp->auxtrace_mp, map->base, fd)) 221 return -1; 222 223 return 0; 224 } 225 226 static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end) 227 { 228 struct perf_event_header *pheader; 229 u64 evt_head = head; 230 int size = mask + 1; 231 232 pr_debug2("overwrite_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head); 233 pheader = (struct perf_event_header *)(buf + (head & mask)); 234 *start = head; 235 while (true) { 236 if (evt_head - head >= (unsigned int)size) { 237 pr_debug("Finished reading overwrite ring buffer: rewind\n"); 238 if (evt_head - head > (unsigned int)size) 239 evt_head -= pheader->size; 240 *end = evt_head; 241 return 0; 242 } 243 244 pheader = (struct perf_event_header *)(buf + (evt_head & mask)); 245 246 if (pheader->size == 0) { 247 pr_debug("Finished reading overwrite ring buffer: get start\n"); 248 *end = evt_head; 249 return 0; 250 } 251 252 evt_head += pheader->size; 253 pr_debug3("move evt_head: %"PRIx64"\n", evt_head); 254 } 255 WARN_ONCE(1, "Shouldn't get here\n"); 256 return -1; 257 } 258 259 /* 260 * Report the start and end of the available data in ringbuffer 261 */ 262 int perf_mmap__read_init(struct perf_mmap *md, bool overwrite, 263 u64 *startp, u64 *endp) 264 { 265 u64 head = perf_mmap__read_head(md); 266 u64 old = md->prev; 267 unsigned char *data = md->base + page_size; 268 unsigned long size; 269 270 *startp = overwrite ? head : old; 271 *endp = overwrite ? old : head; 272 273 if (*startp == *endp) 274 return -EAGAIN; 275 276 size = *endp - *startp; 277 if (size > (unsigned long)(md->mask) + 1) { 278 if (!overwrite) { 279 WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n"); 280 281 md->prev = head; 282 perf_mmap__consume(md, overwrite); 283 return -EAGAIN; 284 } 285 286 /* 287 * Backward ring buffer is full. We still have a chance to read 288 * most of data from it. 289 */ 290 if (overwrite_rb_find_range(data, md->mask, head, startp, endp)) 291 return -EINVAL; 292 } 293 294 return 0; 295 } 296 297 int perf_mmap__push(struct perf_mmap *md, bool overwrite, 298 void *to, int push(void *to, void *buf, size_t size)) 299 { 300 u64 head = perf_mmap__read_head(md); 301 u64 end, start; 302 unsigned char *data = md->base + page_size; 303 unsigned long size; 304 void *buf; 305 int rc = 0; 306 307 rc = perf_mmap__read_init(md, overwrite, &start, &end); 308 if (rc < 0) 309 return (rc == -EAGAIN) ? 0 : -1; 310 311 size = end - start; 312 313 if ((start & md->mask) + size != (end & md->mask)) { 314 buf = &data[start & md->mask]; 315 size = md->mask + 1 - (start & md->mask); 316 start += size; 317 318 if (push(to, buf, size) < 0) { 319 rc = -1; 320 goto out; 321 } 322 } 323 324 buf = &data[start & md->mask]; 325 size = end - start; 326 start += size; 327 328 if (push(to, buf, size) < 0) { 329 rc = -1; 330 goto out; 331 } 332 333 md->prev = head; 334 perf_mmap__consume(md, overwrite); 335 out: 336 return rc; 337 } 338 339 /* 340 * Mandatory for overwrite mode 341 * The direction of overwrite mode is backward. 342 * The last perf_mmap__read() will set tail to map->prev. 343 * Need to correct the map->prev to head which is the end of next read. 344 */ 345 void perf_mmap__read_done(struct perf_mmap *map) 346 { 347 map->prev = perf_mmap__read_head(map); 348 } 349