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  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _LGPL_SOURCE
  20 #include <assert.h>
  21 #include <stdlib.h>
  22 #include <sys/resource.h>
  23 #include <sys/time.h>
  24 #include <stdbool.h>
  25
  26 #include <common/defaults.h>
  27 #include <common/error.h>
  28 #include <common/macros.h>
  29 #include <common/utils.h>
  30
  31 #include "poll.h"
  32
  33
  34 /*
  35  * Maximum number of fd we can monitor.
  36  *
  37  * For poll(2), the max fds must not exceed RLIMIT_NOFILE given by
  38  * getrlimit(2).
  39  */
  40 static unsigned int poll_max_size;
  41
  42 /*
  43  * Resize the epoll events structure of the new size.
  44  *
  45  * Return 0 on success or else -1 with the current events pointer untouched.
  46  */
  47 static int resize_poll_event(struct compat_poll_event_array *array,
  48                 uint32_t new_size)
  49 {
  50         struct pollfd *ptr;
  51
  52         assert(array);
  53
  54         /* Refuse to resize the array more than the max size. */
  55         if (new_size > poll_max_size) {
  56                 goto error;
  57         }
  58
  59         ptr = realloc(array->events, new_size * sizeof(*ptr));
  60         if (ptr == NULL) {
  61                 PERROR("realloc epoll add");
  62                 goto error;
  63         }
  64         if (new_size > array->alloc_size) {
  65                 /* Zero newly allocated memory */
  66                 memset(ptr + array->alloc_size, 0,
  67                         (new_size - array->alloc_size) * sizeof(*ptr));
  68         }
  69         array->events = ptr;
  70         array->alloc_size = new_size;
  71
  72         return 0;
  73
  74 error:
  75         return -1;
  76 }
  77
  78 /*
  79  * Update events with the current events object.
  80  */
  81 static int update_current_events(struct lttng_poll_event *events)
  82 {
  83         int ret;
  84         struct compat_poll_event_array *current, *wait;
  85
  86         assert(events);
  87
  88         current = &events->current;
  89         wait = &events->wait;
  90
  91         wait->nb_fd = current->nb_fd;
  92         if (current->alloc_size != wait->alloc_size) {
  93                 ret = resize_poll_event(wait, current->alloc_size);
  94                 if (ret < 0) {
  95                         goto error;
  96                 }
  97         }
  98         memcpy(wait->events, current->events,
  99                         current->nb_fd * sizeof(*current->events));
 100
 101         /* Update is done. */
 102         events->need_update = 0;
 103
 104         return 0;
 105
 106 error:
 107         return -1;
 108 }
 109
 110 /*
 111  * Create pollfd data structure.
 112  */
 113 LTTNG_HIDDEN
 114 int compat_poll_create(struct lttng_poll_event *events, int size)
 115 {
 116         struct compat_poll_event_array *current, *wait;
 117
 118         if (events == NULL || size <= 0) {
 119                 ERR("Wrong arguments for poll create");
 120                 goto error;
 121         }
 122
 123         if (!poll_max_size) {
 124                 if (lttng_poll_set_max_size()) {
 125                         goto error;
 126                 }
 127         }
 128
 129         /* Don't bust the limit here */
 130         if (size > poll_max_size) {
 131                 size = poll_max_size;
 132         }
 133
 134         /* Reset everything before begining the allocation. */
 135         memset(events, 0, sizeof(struct lttng_poll_event));
 136
 137         current = &events->current;
 138         wait = &events->wait;
 139
 140         /* This *must* be freed by using lttng_poll_free() */
 141         wait->events = zmalloc(size * sizeof(struct pollfd));
 142         if (wait->events == NULL) {
 143                 PERROR("zmalloc struct pollfd");
 144                 goto error;
 145         }
 146
 147         wait->alloc_size = wait->init_size = size;
 148
 149         current->events = zmalloc(size * sizeof(struct pollfd));
 150         if (current->events == NULL) {
 151                 PERROR("zmalloc struct current pollfd");
 152                 goto error;
 153         }
 154
 155         current->alloc_size = current->init_size = size;
 156
 157         return 0;
 158
 159 error:
 160         return -1;
 161 }
 162
 163 /*
 164  * Add fd to pollfd data structure with requested events.
 165  */
 166 LTTNG_HIDDEN
 167 int compat_poll_add(struct lttng_poll_event *events, int fd,
 168                 uint32_t req_events)
 169 {
 170         int new_size, ret, i;
 171         struct compat_poll_event_array *current;
 172
 173         if (events == NULL || events->current.events == NULL || fd < 0) {
 174                 ERR("Bad compat poll add arguments");
 175                 goto error;
 176         }
 177
 178         current = &events->current;
 179
 180         /* Check if fd we are trying to add is already there. */
 181         for (i = 0; i < current->nb_fd; i++) {
 182                 if (current->events[i].fd == fd) {
 183                         errno = EEXIST;
 184                         goto error;
 185                 }
 186         }
 187
 188         /* Resize array if needed. */
 189         new_size = 1U << utils_get_count_order_u32(current->nb_fd + 1);
 190         if (new_size != current->alloc_size && new_size >= current->init_size) {
 191                 ret = resize_poll_event(current, new_size);
 192                 if (ret < 0) {
 193                         goto error;
 194                 }
 195         }
 196
 197         current->events[current->nb_fd].fd = fd;
 198         current->events[current->nb_fd].events = req_events;
 199         current->nb_fd++;
 200         events->need_update = 1;
 201
 202         DBG("fd %d of %d added to pollfd", fd, current->nb_fd);
 203
 204         return 0;
 205
 206 error:
 207         return -1;
 208 }
 209
 210 /*
 211  * Modify an fd's events..
 212  */
 213 LTTNG_HIDDEN
 214 int compat_poll_mod(struct lttng_poll_event *events, int fd,
 215                 uint32_t req_events)
 216 {
 217         int i;
 218         struct compat_poll_event_array *current;
 219
 220         if (events == NULL || events->current.nb_fd == 0 ||
 221                         events->current.events == NULL || fd < 0) {
 222                 ERR("Bad compat poll mod arguments");
 223                 goto error;
 224         }
 225
 226         current = &events->current;
 227
 228         for (i = 0; i < current->nb_fd; i++) {
 229                 if (current->events[i].fd == fd) {
 230                         current->events[i].events = req_events;
 231                         events->need_update = 1;
 232                         break;
 233                 }
 234         }
 235
 236         /*
 237          * The epoll flavor doesn't flag modifying a non-included FD as an
 238          * error.
 239          */
 240
 241         return 0;
 242
 243 error:
 244         return -1;
 245 }
 246
 247 /*
 248  * Remove a fd from the pollfd structure.
 249  */
 250 LTTNG_HIDDEN
 251 int compat_poll_del(struct lttng_poll_event *events, int fd)
 252 {
 253         int i, count = 0, ret;
 254         uint32_t new_size;
 255         struct compat_poll_event_array *current;
 256
 257         if (events == NULL || events->current.nb_fd == 0 ||
 258                         events->current.events == NULL || fd < 0) {
 259                 goto error;
 260         }
 261
 262         /* Ease our life a bit. */
 263         current = &events->current;
 264
 265         for (i = 0; i < current->nb_fd; i++) {
 266                 /* Don't put back the fd we want to delete */
 267                 if (current->events[i].fd != fd) {
 268                         current->events[count].fd = current->events[i].fd;
 269                         current->events[count].events = current->events[i].events;
 270                         count++;
 271                 }
 272         }
 273
 274         /* The fd was not in our set, return no error as with epoll. */
 275         if (current->nb_fd == count) {
 276                 goto end;
 277         }
 278
 279         /* No fd duplicate should be ever added into array. */
 280         assert(current->nb_fd - 1 == count);
 281         current->nb_fd = count;
 282
 283         /* Resize array if needed. */
 284         new_size = 1U << utils_get_count_order_u32(current->nb_fd);
 285         if (new_size != current->alloc_size && new_size >= current->init_size
 286                         && current->nb_fd != 0) {
 287                 ret = resize_poll_event(current, new_size);
 288                 if (ret < 0) {
 289                         goto error;
 290                 }
 291         }
 292
 293         events->need_update = 1;
 294
 295 end:
 296         return 0;
 297
 298 error:
 299         return -1;
 300 }
 301
 302 /*
 303  * Wait on poll() with timeout. Blocking call.
 304  */
 305 LTTNG_HIDDEN
 306 int compat_poll_wait(struct lttng_poll_event *events, int timeout,
 307                 bool interruptible)
 308 {
 309         int ret, active_fd_count;
 310         int idle_pfd_index = 0;
 311         size_t i;
 312
 313         if (events == NULL || events->current.events == NULL) {
 314                 ERR("poll wait arguments error");
 315                 goto error;
 316         }
 317
 318         if (events->current.nb_fd == 0) {
 319                 /* Return an invalid error to be consistent with epoll. */
 320                 errno = EINVAL;
 321                 events->wait.nb_fd = 0;
 322                 goto error;
 323         }
 324
 325         if (events->need_update) {
 326                 ret = update_current_events(events);
 327                 if (ret < 0) {
 328                         errno = ENOMEM;
 329                         goto error;
 330                 }
 331         }
 332
 333         do {
 334                 ret = poll(events->wait.events, events->wait.nb_fd, timeout);
 335         } while (!interruptible && ret == -1 && errno == EINTR);
 336         if (ret < 0) {
 337                 if (errno != EINTR) {
 338                         PERROR("poll wait");
 339                 }
 340                 goto error;
 341         }
 342
 343         active_fd_count = ret;
 344
 345         /*
 346          * Swap all active pollfd structs to the beginning of the
 347          * array to emulate compat-epoll behaviour. This algorithm takes
 348          * advantage of poll's returned value and the burst nature of active
 349          * events on the file descriptors. The while loop guarantees that
 350          * idle_pfd will always point to an idle fd.
 351          */
 352         if (active_fd_count == events->wait.nb_fd) {
 353                 goto end;
 354         }
 355         while (idle_pfd_index < active_fd_count &&
 356                         events->wait.events[idle_pfd_index].revents != 0) {
 357                 idle_pfd_index++;
 358         }
 359
 360         for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
 361                         i++) {
 362                 struct pollfd swap_pfd;
 363                 struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
 364                 struct pollfd *current_pfd = &events->wait.events[i];
 365
 366                 if (idle_pfd->revents != 0) {
 367                         swap_pfd = *current_pfd;
 368                         *current_pfd = *idle_pfd;
 369                         *idle_pfd = swap_pfd;
 370                         idle_pfd_index++;
 371                 }
 372         }
 373
 374 end:
 375         return ret;
 376
 377 error:
 378         return -1;
 379 }
 380
 381 /*
 382  * Setup poll set maximum size.
 383  */
 384 LTTNG_HIDDEN
 385 int compat_poll_set_max_size(void)
 386 {
 387         int ret, retval = 0;
 388         struct rlimit lim;
 389
 390         ret = getrlimit(RLIMIT_NOFILE, &lim);
 391         if (ret < 0) {
 392                 PERROR("getrlimit poll RLIMIT_NOFILE");
 393                 retval = -1;
 394                 goto end;
 395         }
 396
 397         poll_max_size = lim.rlim_cur;
 398 end:
 399         if (poll_max_size == 0) {
 400                 poll_max_size = DEFAULT_POLL_SIZE;
 401         }
 402         DBG("poll set max size set to %u", poll_max_size);
 403         return retval;
 404 }