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 start, u64 end, u64 *prev) 26 { 27 unsigned char *data = map->base + page_size; 28 union perf_event *event = NULL; 29 int diff = end - start; 30 31 if (diff >= (int)sizeof(event->header)) { 32 size_t size; 33 34 event = (union perf_event *)&data[start & map->mask]; 35 size = event->header.size; 36 37 if (size < sizeof(event->header) || diff < (int)size) { 38 event = NULL; 39 goto broken_event; 40 } 41 42 /* 43 * Event straddles the mmap boundary -- header should always 44 * be inside due to u64 alignment of output. 45 */ 46 if ((start & map->mask) + size != ((start + size) & map->mask)) { 47 unsigned int offset = start; 48 unsigned int len = min(sizeof(*event), size), cpy; 49 void *dst = map->event_copy; 50 51 do { 52 cpy = min(map->mask + 1 - (offset & map->mask), len); 53 memcpy(dst, &data[offset & map->mask], cpy); 54 offset += cpy; 55 dst += cpy; 56 len -= cpy; 57 } while (len); 58 59 event = (union perf_event *)map->event_copy; 60 } 61 62 start += size; 63 } 64 65 broken_event: 66 if (prev) 67 *prev = start; 68 69 return event; 70 } 71 72 union perf_event *perf_mmap__read_forward(struct perf_mmap *map) 73 { 74 u64 head; 75 u64 old = map->prev; 76 77 /* 78 * Check if event was unmapped due to a POLLHUP/POLLERR. 79 */ 80 if (!refcount_read(&map->refcnt)) 81 return NULL; 82 83 head = perf_mmap__read_head(map); 84 85 return perf_mmap__read(map, old, head, &map->prev); 86 } 87 88 union perf_event *perf_mmap__read_backward(struct perf_mmap *map) 89 { 90 u64 head, end; 91 u64 start = map->prev; 92 93 /* 94 * Check if event was unmapped due to a POLLHUP/POLLERR. 95 */ 96 if (!refcount_read(&map->refcnt)) 97 return NULL; 98 99 head = perf_mmap__read_head(map); 100 if (!head) 101 return NULL; 102 103 /* 104 * 'head' pointer starts from 0. Kernel minus sizeof(record) form 105 * it each time when kernel writes to it, so in fact 'head' is 106 * negative. 'end' pointer is made manually by adding the size of 107 * the ring buffer to 'head' pointer, means the validate data can 108 * read is the whole ring buffer. If 'end' is positive, the ring 109 * buffer has not fully filled, so we must adjust 'end' to 0. 110 * 111 * However, since both 'head' and 'end' is unsigned, we can't 112 * simply compare 'end' against 0. Here we compare '-head' and 113 * the size of the ring buffer, where -head is the number of bytes 114 * kernel write to the ring buffer. 115 */ 116 if (-head < (u64)(map->mask + 1)) 117 end = 0; 118 else 119 end = head + map->mask + 1; 120 121 return perf_mmap__read(map, start, end, &map->prev); 122 } 123 124 void perf_mmap__read_catchup(struct perf_mmap *map) 125 { 126 u64 head; 127 128 if (!refcount_read(&map->refcnt)) 129 return; 130 131 head = perf_mmap__read_head(map); 132 map->prev = head; 133 } 134 135 static bool perf_mmap__empty(struct perf_mmap *map) 136 { 137 return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base; 138 } 139 140 void perf_mmap__get(struct perf_mmap *map) 141 { 142 refcount_inc(&map->refcnt); 143 } 144 145 void perf_mmap__put(struct perf_mmap *map) 146 { 147 BUG_ON(map->base && refcount_read(&map->refcnt) == 0); 148 149 if (refcount_dec_and_test(&map->refcnt)) 150 perf_mmap__munmap(map); 151 } 152 153 void perf_mmap__consume(struct perf_mmap *map, bool overwrite) 154 { 155 if (!overwrite) { 156 u64 old = map->prev; 157 158 perf_mmap__write_tail(map, old); 159 } 160 161 if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map)) 162 perf_mmap__put(map); 163 } 164 165 int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused, 166 struct auxtrace_mmap_params *mp __maybe_unused, 167 void *userpg __maybe_unused, 168 int fd __maybe_unused) 169 { 170 return 0; 171 } 172 173 void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused) 174 { 175 } 176 177 void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused, 178 off_t auxtrace_offset __maybe_unused, 179 unsigned int auxtrace_pages __maybe_unused, 180 bool auxtrace_overwrite __maybe_unused) 181 { 182 } 183 184 void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused, 185 struct perf_evlist *evlist __maybe_unused, 186 int idx __maybe_unused, 187 bool per_cpu __maybe_unused) 188 { 189 } 190 191 void perf_mmap__munmap(struct perf_mmap *map) 192 { 193 if (map->base != NULL) { 194 munmap(map->base, perf_mmap__mmap_len(map)); 195 map->base = NULL; 196 map->fd = -1; 197 refcount_set(&map->refcnt, 0); 198 } 199 auxtrace_mmap__munmap(&map->auxtrace_mmap); 200 } 201 202 int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd) 203 { 204 /* 205 * The last one will be done at perf_evlist__mmap_consume(), so that we 206 * make sure we don't prevent tools from consuming every last event in 207 * the ring buffer. 208 * 209 * I.e. we can get the POLLHUP meaning that the fd doesn't exist 210 * anymore, but the last events for it are still in the ring buffer, 211 * waiting to be consumed. 212 * 213 * Tools can chose to ignore this at their own discretion, but the 214 * evlist layer can't just drop it when filtering events in 215 * perf_evlist__filter_pollfd(). 216 */ 217 refcount_set(&map->refcnt, 2); 218 map->prev = 0; 219 map->mask = mp->mask; 220 map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot, 221 MAP_SHARED, fd, 0); 222 if (map->base == MAP_FAILED) { 223 pr_debug2("failed to mmap perf event ring buffer, error %d\n", 224 errno); 225 map->base = NULL; 226 return -1; 227 } 228 map->fd = fd; 229 230 if (auxtrace_mmap__mmap(&map->auxtrace_mmap, 231 &mp->auxtrace_mp, map->base, fd)) 232 return -1; 233 234 return 0; 235 } 236 237 static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end) 238 { 239 struct perf_event_header *pheader; 240 u64 evt_head = head; 241 int size = mask + 1; 242 243 pr_debug2("overwrite_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head); 244 pheader = (struct perf_event_header *)(buf + (head & mask)); 245 *start = head; 246 while (true) { 247 if (evt_head - head >= (unsigned int)size) { 248 pr_debug("Finished reading overwrite ring buffer: rewind\n"); 249 if (evt_head - head > (unsigned int)size) 250 evt_head -= pheader->size; 251 *end = evt_head; 252 return 0; 253 } 254 255 pheader = (struct perf_event_header *)(buf + (evt_head & mask)); 256 257 if (pheader->size == 0) { 258 pr_debug("Finished reading overwrite ring buffer: get start\n"); 259 *end = evt_head; 260 return 0; 261 } 262 263 evt_head += pheader->size; 264 pr_debug3("move evt_head: %"PRIx64"\n", evt_head); 265 } 266 WARN_ONCE(1, "Shouldn't get here\n"); 267 return -1; 268 } 269 270 int perf_mmap__push(struct perf_mmap *md, bool overwrite, 271 void *to, int push(void *to, void *buf, size_t size)) 272 { 273 u64 head = perf_mmap__read_head(md); 274 u64 old = md->prev; 275 u64 end = head, start = old; 276 unsigned char *data = md->base + page_size; 277 unsigned long size; 278 void *buf; 279 int rc = 0; 280 281 start = overwrite ? head : old; 282 end = overwrite ? old : head; 283 284 if (start == end) 285 return 0; 286 287 size = end - start; 288 if (size > (unsigned long)(md->mask) + 1) { 289 if (!overwrite) { 290 WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n"); 291 292 md->prev = head; 293 perf_mmap__consume(md, overwrite); 294 return 0; 295 } 296 297 /* 298 * Backward ring buffer is full. We still have a chance to read 299 * most of data from it. 300 */ 301 if (overwrite_rb_find_range(data, md->mask, head, &start, &end)) 302 return -1; 303 } 304 305 if ((start & md->mask) + size != (end & md->mask)) { 306 buf = &data[start & md->mask]; 307 size = md->mask + 1 - (start & md->mask); 308 start += size; 309 310 if (push(to, buf, size) < 0) { 311 rc = -1; 312 goto out; 313 } 314 } 315 316 buf = &data[start & md->mask]; 317 size = end - start; 318 start += size; 319 320 if (push(to, buf, size) < 0) { 321 rc = -1; 322 goto out; 323 } 324 325 md->prev = head; 326 perf_mmap__consume(md, overwrite); 327 out: 328 return rc; 329 } 330