src/common/compat/compat-poll.c

   1 /*
   2  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   3  * Copyright (C) 2019 Yannick Lamarre <ylamarre@efficios.com>
   4  *
   5  * SPDX-License-Identifier: GPL-2.0-only
   6  *
   7  */
   8
   9 #define _LGPL_SOURCE
  10 #include <assert.h>
  11 #include <stdlib.h>
  12 #include <sys/resource.h>
  13 #include <sys/time.h>
  14 #include <stdbool.h>
  15
  16 #include <common/defaults.h>
  17 #include <common/error.h>
  18 #include <common/macros.h>
  19 #include <common/utils.h>
  20
  21 #include "poll.h"
  22
  23
  24 /*
  25  * Maximum number of fd we can monitor.
  26  *
  27  * For poll(2), the max fds must not exceed RLIMIT_NOFILE given by
  28  * getrlimit(2).
  29  */
  30 static unsigned int poll_max_size;
  31
  32 /*
  33  * Resize the epoll events structure of the new size.
  34  *
  35  * Return 0 on success or else -1 with the current events pointer untouched.
  36  */
  37 static int resize_poll_event(struct compat_poll_event_array *array,
  38                 uint32_t new_size)
  39 {
  40         struct pollfd *ptr;
  41
  42         assert(array);
  43
  44         /* Refuse to resize the array more than the max size. */
  45         if (new_size > poll_max_size) {
  46                 goto error;
  47         }
  48
  49         ptr = realloc(array->events, new_size * sizeof(*ptr));
  50         if (ptr == NULL) {
  51                 PERROR("realloc epoll add");
  52                 goto error;
  53         }
  54         if (new_size > array->alloc_size) {
  55                 /* Zero newly allocated memory */
  56                 memset(ptr + array->alloc_size, 0,
  57                         (new_size - array->alloc_size) * sizeof(*ptr));
  58         }
  59         array->events = ptr;
  60         array->alloc_size = new_size;
  61
  62         return 0;
  63
  64 error:
  65         return -1;
  66 }
  67
  68 /*
  69  * Update events with the current events object.
  70  */
  71 static int update_current_events(struct lttng_poll_event *events)
  72 {
  73         int ret;
  74         struct compat_poll_event_array *current, *wait;
  75
  76         assert(events);
  77
  78         current = &events->current;
  79         wait = &events->wait;
  80
  81         wait->nb_fd = current->nb_fd;
  82         if (current->alloc_size != wait->alloc_size) {
  83                 ret = resize_poll_event(wait, current->alloc_size);
  84                 if (ret < 0) {
  85                         goto error;
  86                 }
  87         }
  88         memcpy(wait->events, current->events,
  89                         current->nb_fd * sizeof(*current->events));
  90
  91         /* Update is done. */
  92         events->need_update = 0;
  93
  94         return 0;
  95
  96 error:
  97         return -1;
  98 }
  99
 100 /*
 101  * Create pollfd data structure.
 102  */
 103 LTTNG_HIDDEN
 104 int compat_poll_create(struct lttng_poll_event *events, int size)
 105 {
 106         struct compat_poll_event_array *current, *wait;
 107
 108         if (events == NULL || size <= 0) {
 109                 ERR("Wrong arguments for poll create");
 110                 goto error;
 111         }
 112
 113         if (!poll_max_size) {
 114                 if (lttng_poll_set_max_size()) {
 115                         goto error;
 116                 }
 117         }
 118
 119         /* Don't bust the limit here */
 120         if (size > poll_max_size) {
 121                 size = poll_max_size;
 122         }
 123
 124         /* Reset everything before begining the allocation. */
 125         memset(events, 0, sizeof(struct lttng_poll_event));
 126
 127         current = &events->current;
 128         wait = &events->wait;
 129
 130         /* This *must* be freed by using lttng_poll_free() */
 131         wait->events = zmalloc(size * sizeof(struct pollfd));
 132         if (wait->events == NULL) {
 133                 PERROR("zmalloc struct pollfd");
 134                 goto error;
 135         }
 136
 137         wait->alloc_size = wait->init_size = size;
 138
 139         current->events = zmalloc(size * sizeof(struct pollfd));
 140         if (current->events == NULL) {
 141                 PERROR("zmalloc struct current pollfd");
 142                 goto error;
 143         }
 144
 145         current->alloc_size = current->init_size = size;
 146
 147         return 0;
 148
 149 error:
 150         return -1;
 151 }
 152
 153 /*
 154  * Add fd to pollfd data structure with requested events.
 155  */
 156 LTTNG_HIDDEN
 157 int compat_poll_add(struct lttng_poll_event *events, int fd,
 158                 uint32_t req_events)
 159 {
 160         int new_size, ret, i;
 161         struct compat_poll_event_array *current;
 162
 163         if (events == NULL || events->current.events == NULL || fd < 0) {
 164                 ERR("Bad compat poll add arguments");
 165                 goto error;
 166         }
 167
 168         current = &events->current;
 169
 170         /* Check if fd we are trying to add is already there. */
 171         for (i = 0; i < current->nb_fd; i++) {
 172                 if (current->events[i].fd == fd) {
 173                         errno = EEXIST;
 174                         goto error;
 175                 }
 176         }
 177
 178         /* Resize array if needed. */
 179         new_size = 1U << utils_get_count_order_u32(current->nb_fd + 1);
 180         if (new_size != current->alloc_size && new_size >= current->init_size) {
 181                 ret = resize_poll_event(current, new_size);
 182                 if (ret < 0) {
 183                         goto error;
 184                 }
 185         }
 186
 187         current->events[current->nb_fd].fd = fd;
 188         current->events[current->nb_fd].events = req_events;
 189         current->nb_fd++;
 190         events->need_update = 1;
 191
 192         DBG("fd %d of %d added to pollfd", fd, current->nb_fd);
 193
 194         return 0;
 195
 196 error:
 197         return -1;
 198 }
 199
 200 /*
 201  * Modify an fd's events..
 202  */
 203 LTTNG_HIDDEN
 204 int compat_poll_mod(struct lttng_poll_event *events, int fd,
 205                 uint32_t req_events)
 206 {
 207         int i;
 208         struct compat_poll_event_array *current;
 209
 210         if (events == NULL || events->current.nb_fd == 0 ||
 211                         events->current.events == NULL || fd < 0) {
 212                 ERR("Bad compat poll mod arguments");
 213                 goto error;
 214         }
 215
 216         current = &events->current;
 217
 218         for (i = 0; i < current->nb_fd; i++) {
 219                 if (current->events[i].fd == fd) {
 220                         current->events[i].events = req_events;
 221                         events->need_update = 1;
 222                         break;
 223                 }
 224         }
 225
 226         /*
 227          * The epoll flavor doesn't flag modifying a non-included FD as an
 228          * error.
 229          */
 230
 231         return 0;
 232
 233 error:
 234         return -1;
 235 }
 236
 237 /*
 238  * Remove a fd from the pollfd structure.
 239  */
 240 LTTNG_HIDDEN
 241 int compat_poll_del(struct lttng_poll_event *events, int fd)
 242 {
 243         int i, count = 0, ret;
 244         uint32_t new_size;
 245         struct compat_poll_event_array *current;
 246
 247         if (events == NULL || events->current.nb_fd == 0 ||
 248                         events->current.events == NULL || fd < 0) {
 249                 goto error;
 250         }
 251
 252         /* Ease our life a bit. */
 253         current = &events->current;
 254
 255         for (i = 0; i < current->nb_fd; i++) {
 256                 /* Don't put back the fd we want to delete */
 257                 if (current->events[i].fd != fd) {
 258                         current->events[count].fd = current->events[i].fd;
 259                         current->events[count].events = current->events[i].events;
 260                         count++;
 261                 }
 262         }
 263
 264         /* The fd was not in our set, return no error as with epoll. */
 265         if (current->nb_fd == count) {
 266                 goto end;
 267         }
 268
 269         /* No fd duplicate should be ever added into array. */
 270         assert(current->nb_fd - 1 == count);
 271         current->nb_fd = count;
 272
 273         /* Resize array if needed. */
 274         new_size = 1U << utils_get_count_order_u32(current->nb_fd);
 275         if (new_size != current->alloc_size && new_size >= current->init_size
 276                         && current->nb_fd != 0) {
 277                 ret = resize_poll_event(current, new_size);
 278                 if (ret < 0) {
 279                         goto error;
 280                 }
 281         }
 282
 283         events->need_update = 1;
 284
 285 end:
 286         return 0;
 287
 288 error:
 289         return -1;
 290 }
 291
 292 /*
 293  * Wait on poll() with timeout. Blocking call.
 294  */
 295 LTTNG_HIDDEN
 296 int compat_poll_wait(struct lttng_poll_event *events, int timeout,
 297                 bool interruptible)
 298 {
 299         int ret, active_fd_count;
 300         int idle_pfd_index = 0;
 301         size_t i;
 302
 303         if (events == NULL || events->current.events == NULL) {
 304                 ERR("poll wait arguments error");
 305                 goto error;
 306         }
 307
 308         if (events->current.nb_fd == 0) {
 309                 /* Return an invalid error to be consistent with epoll. */
 310                 errno = EINVAL;
 311                 events->wait.nb_fd = 0;
 312                 goto error;
 313         }
 314
 315         if (events->need_update) {
 316                 ret = update_current_events(events);
 317                 if (ret < 0) {
 318                         errno = ENOMEM;
 319                         goto error;
 320                 }
 321         }
 322
 323         do {
 324                 ret = poll(events->wait.events, events->wait.nb_fd, timeout);
 325         } while (!interruptible && ret == -1 && errno == EINTR);
 326         if (ret < 0) {
 327                 if (errno != EINTR) {
 328                         PERROR("poll wait");
 329                 }
 330                 goto error;
 331         }
 332
 333         active_fd_count = ret;
 334
 335         /*
 336          * Swap all active pollfd structs to the beginning of the
 337          * array to emulate compat-epoll behaviour. This algorithm takes
 338          * advantage of poll's returned value and the burst nature of active
 339          * events on the file descriptors. The while loop guarantees that
 340          * idle_pfd will always point to an idle fd.
 341          */
 342         if (active_fd_count == events->wait.nb_fd) {
 343                 goto end;
 344         }
 345         while (idle_pfd_index < active_fd_count &&
 346                         events->wait.events[idle_pfd_index].revents != 0) {
 347                 idle_pfd_index++;
 348         }
 349
 350         for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
 351                         i++) {
 352                 struct pollfd swap_pfd;
 353                 struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
 354                 struct pollfd *current_pfd = &events->wait.events[i];
 355
 356                 if (idle_pfd->revents != 0) {
 357                         swap_pfd = *current_pfd;
 358                         *current_pfd = *idle_pfd;
 359                         *idle_pfd = swap_pfd;
 360                         idle_pfd_index++;
 361                 }
 362         }
 363
 364 end:
 365         return ret;
 366
 367 error:
 368         return -1;
 369 }
 370
 371 /*
 372  * Setup poll set maximum size.
 373  */
 374 LTTNG_HIDDEN
 375 int compat_poll_set_max_size(void)
 376 {
 377         int ret, retval = 0;
 378         struct rlimit lim;
 379
 380         ret = getrlimit(RLIMIT_NOFILE, &lim);
 381         if (ret < 0) {
 382                 PERROR("getrlimit poll RLIMIT_NOFILE");
 383                 retval = -1;
 384                 goto end;
 385         }
 386
 387         poll_max_size = lim.rlim_cur;
 388 end:
 389         if (poll_max_size == 0) {
 390                 poll_max_size = DEFAULT_POLL_SIZE;
 391         }
 392         DBG("poll set max size set to %u", poll_max_size);
 393         return retval;
 394 }