tools/perf/util/mmap.c

   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  * 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  */
  78 union 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
 100 static bool perf_mmap__empty(struct perf_mmap *map)
 101 {
 102         return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base;
 103 }
 104
 105 void perf_mmap__get(struct perf_mmap *map)
 106 {
 107         refcount_inc(&map->refcnt);
 108 }
 109
 110 void 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
 118 void 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
 130 int __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
 138 void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused)
 139 {
 140 }
 141
 142 void __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
 149 void __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
 156 void 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
 167 int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int cpu)
 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         map->cpu = cpu;
 195
 196         if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
 197                                 &mp->auxtrace_mp, map->base, fd))
 198                 return -1;
 199
 200         return 0;
 201 }
 202
 203 static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
 204 {
 205         struct perf_event_header *pheader;
 206         u64 evt_head = *start;
 207         int size = mask + 1;
 208
 209         pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);
 210         pheader = (struct perf_event_header *)(buf + (*start & mask));
 211         while (true) {
 212                 if (evt_head - *start >= (unsigned int)size) {
 213                         pr_debug("Finished reading overwrite ring buffer: rewind\n");
 214                         if (evt_head - *start > (unsigned int)size)
 215                                 evt_head -= pheader->size;
 216                         *end = evt_head;
 217                         return 0;
 218                 }
 219
 220                 pheader = (struct perf_event_header *)(buf + (evt_head & mask));
 221
 222                 if (pheader->size == 0) {
 223                         pr_debug("Finished reading overwrite ring buffer: get start\n");
 224                         *end = evt_head;
 225                         return 0;
 226                 }
 227
 228                 evt_head += pheader->size;
 229                 pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
 230         }
 231         WARN_ONCE(1, "Shouldn't get here\n");
 232         return -1;
 233 }
 234
 235 /*
 236  * Report the start and end of the available data in ringbuffer
 237  */
 238 static int __perf_mmap__read_init(struct perf_mmap *md)
 239 {
 240         u64 head = perf_mmap__read_head(md);
 241         u64 old = md->prev;
 242         unsigned char *data = md->base + page_size;
 243         unsigned long size;
 244
 245         md->start = md->overwrite ? head : old;
 246         md->end = md->overwrite ? old : head;
 247
 248         if (md->start == md->end)
 249                 return -EAGAIN;
 250
 251         size = md->end - md->start;
 252         if (size > (unsigned long)(md->mask) + 1) {
 253                 if (!md->overwrite) {
 254                         WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
 255
 256                         md->prev = head;
 257                         perf_mmap__consume(md);
 258                         return -EAGAIN;
 259                 }
 260
 261                 /*
 262                  * Backward ring buffer is full. We still have a chance to read
 263                  * most of data from it.
 264                  */
 265                 if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))
 266                         return -EINVAL;
 267         }
 268
 269         return 0;
 270 }
 271
 272 int perf_mmap__read_init(struct perf_mmap *map)
 273 {
 274         /*
 275          * Check if event was unmapped due to a POLLHUP/POLLERR.
 276          */
 277         if (!refcount_read(&map->refcnt))
 278                 return -ENOENT;
 279
 280         return __perf_mmap__read_init(map);
 281 }
 282
 283 int perf_mmap__push(struct perf_mmap *md, void *to,
 284                     int push(void *to, void *buf, size_t size))
 285 {
 286         u64 head = perf_mmap__read_head(md);
 287         unsigned char *data = md->base + page_size;
 288         unsigned long size;
 289         void *buf;
 290         int rc = 0;
 291
 292         rc = perf_mmap__read_init(md);
 293         if (rc < 0)
 294                 return (rc == -EAGAIN) ? 0 : -1;
 295
 296         size = md->end - md->start;
 297
 298         if ((md->start & md->mask) + size != (md->end & md->mask)) {
 299                 buf = &data[md->start & md->mask];
 300                 size = md->mask + 1 - (md->start & md->mask);
 301                 md->start += size;
 302
 303                 if (push(to, buf, size) < 0) {
 304                         rc = -1;
 305                         goto out;
 306                 }
 307         }
 308
 309         buf = &data[md->start & md->mask];
 310         size = md->end - md->start;
 311         md->start += size;
 312
 313         if (push(to, buf, size) < 0) {
 314                 rc = -1;
 315                 goto out;
 316         }
 317
 318         md->prev = head;
 319         perf_mmap__consume(md);
 320 out:
 321         return rc;
 322 }
 323
 324 /*
 325  * Mandatory for overwrite mode
 326  * The direction of overwrite mode is backward.
 327  * The last perf_mmap__read() will set tail to map->prev.
 328  * Need to correct the map->prev to head which is the end of next read.
 329  */
 330 void perf_mmap__read_done(struct perf_mmap *map)
 331 {
 332         /*
 333          * Check if event was unmapped due to a POLLHUP/POLLERR.
 334          */
 335         if (!refcount_read(&map->refcnt))
 336                 return;
 337
 338         map->prev = perf_mmap__read_head(map);
 339 }