libringbuffer/shm.c

   1 /*
   2  * libringbuffer/shm.c
   3  *
   4  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; only
   9  * version 2.1 of the License.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "shm.h"
  22 #include <unistd.h>
  23 #include <fcntl.h>
  24 #include <sys/mman.h>
  25 #include <sys/stat.h>   /* For mode constants */
  26 #include <fcntl.h>      /* For O_* constants */
  27 #include <assert.h>
  28 #include <stdio.h>
  29 #include <signal.h>
  30 #include <dirent.h>
  31 #include <lttng/align.h>
  32 #include <helper.h>
  33 #include <limits.h>
  34 #include <helper.h>
  35
  36 /*
  37  * Ensure we have the required amount of space available by writing 0
  38  * into the entire buffer. Not doing so can trigger SIGBUS when going
  39  * beyond the available shm space.
  40  */
  41 static
  42 int zero_file(int fd, size_t len)
  43 {
  44         ssize_t retlen;
  45         size_t written = 0;
  46         char *zeropage;
  47         long pagelen;
  48         int ret;
  49
  50         pagelen = sysconf(_SC_PAGESIZE);
  51         if (pagelen < 0)
  52                 return (int) pagelen;
  53         zeropage = calloc(pagelen, 1);
  54         if (!zeropage)
  55                 return -ENOMEM;
  56
  57         while (len > written) {
  58                 do {
  59                         retlen = write(fd, zeropage,
  60                                 min_t(size_t, pagelen, len - written));
  61                 } while (retlen == -1UL && errno == EINTR);
  62                 if (retlen < 0) {
  63                         ret = (int) retlen;
  64                         goto error;
  65                 }
  66                 written += retlen;
  67         }
  68         ret = 0;
  69 error:
  70         free(zeropage);
  71         return ret;
  72 }
  73
  74 struct shm_object_table *shm_object_table_create(size_t max_nb_obj)
  75 {
  76         struct shm_object_table *table;
  77
  78         table = zmalloc(sizeof(struct shm_object_table) +
  79                         max_nb_obj * sizeof(table->objects[0]));
  80         if (!table)
  81                 return NULL;
  82         table->size = max_nb_obj;
  83         return table;
  84 }
  85
  86 static
  87 struct shm_object *_shm_object_table_alloc_shm(struct shm_object_table *table,
  88                                            size_t memory_map_size)
  89 {
  90         int shmfd, waitfd[2], ret, i, sigblocked = 0;
  91         struct shm_object *obj;
  92         char *memory_map;
  93         char tmp_name[NAME_MAX] = "/ust-shm-tmp-XXXXXX";
  94         sigset_t all_sigs, orig_sigs;
  95
  96         if (table->allocated_len >= table->size)
  97                 return NULL;
  98         obj = &table->objects[table->allocated_len];
  99
 100         /* wait_fd: create pipe */
 101         ret = pipe(waitfd);
 102         if (ret < 0) {
 103                 PERROR("pipe");
 104                 goto error_pipe;
 105         }
 106         for (i = 0; i < 2; i++) {
 107                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 108                 if (ret < 0) {
 109                         PERROR("fcntl");
 110                         goto error_fcntl;
 111                 }
 112         }
 113         /* The write end of the pipe needs to be non-blocking */
 114         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 115         if (ret < 0) {
 116                 PERROR("fcntl");
 117                 goto error_fcntl;
 118         }
 119         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 120
 121         /* shm_fd: create shm */
 122
 123         /*
 124          * Theoretically, we could leak a shm if the application crashes
 125          * between open and unlink. Disable signals on this thread for
 126          * increased safety against this scenario.
 127          */
 128         sigfillset(&all_sigs);
 129         ret = pthread_sigmask(SIG_BLOCK, &all_sigs, &orig_sigs);
 130         if (ret == -1) {
 131                 PERROR("pthread_sigmask");
 132                 goto error_pthread_sigmask;
 133         }
 134         sigblocked = 1;
 135
 136         /*
 137          * Allocate shm, and immediately unlink its shm oject, keeping
 138          * only the file descriptor as a reference to the object. If it
 139          * already exists (caused by short race window during which the
 140          * global object exists in a concurrent shm_open), simply retry.
 141          * We specifically do _not_ use the / at the beginning of the
 142          * pathname so that some OS implementations can keep it local to
 143          * the process (POSIX leaves this implementation-defined).
 144          */
 145         do {
 146                 /*
 147                  * Using mktemp filename with O_CREAT | O_EXCL open
 148                  * flags.
 149                  */
 150                 (void) mktemp(tmp_name);
 151                 if (tmp_name[0] == '\0') {
 152                         PERROR("mktemp");
 153                         goto error_shm_open;
 154                 }
 155                 shmfd = shm_open(tmp_name,
 156                                  O_CREAT | O_EXCL | O_RDWR, 0700);
 157         } while (shmfd < 0 && (errno == EEXIST || errno == EACCES));
 158         if (shmfd < 0) {
 159                 PERROR("shm_open");
 160                 goto error_shm_open;
 161         }
 162         ret = shm_unlink(tmp_name);
 163         if (ret < 0 && errno != ENOENT) {
 164                 PERROR("shm_unlink");
 165                 goto error_shm_release;
 166         }
 167         sigblocked = 0;
 168         ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
 169         if (ret == -1) {
 170                 PERROR("pthread_sigmask");
 171                 goto error_sigmask_release;
 172         }
 173         ret = zero_file(shmfd, memory_map_size);
 174         if (ret) {
 175                 PERROR("zero_file");
 176                 goto error_zero_file;
 177         }
 178         ret = ftruncate(shmfd, memory_map_size);
 179         if (ret) {
 180                 PERROR("ftruncate");
 181                 goto error_ftruncate;
 182         }
 183         obj->shm_fd = shmfd;
 184
 185         /* memory_map: mmap */
 186         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 187                           MAP_SHARED, shmfd, 0);
 188         if (memory_map == MAP_FAILED) {
 189                 PERROR("mmap");
 190                 goto error_mmap;
 191         }
 192         obj->type = SHM_OBJECT_SHM;
 193         obj->memory_map = memory_map;
 194         obj->memory_map_size = memory_map_size;
 195         obj->allocated_len = 0;
 196         obj->index = table->allocated_len++;
 197
 198         return obj;
 199
 200 error_mmap:
 201 error_ftruncate:
 202 error_shm_release:
 203 error_zero_file:
 204 error_sigmask_release:
 205         ret = close(shmfd);
 206         if (ret) {
 207                 PERROR("close");
 208                 assert(0);
 209         }
 210 error_shm_open:
 211         if (sigblocked) {
 212                 ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
 213                 if (ret == -1) {
 214                         PERROR("pthread_sigmask");
 215                 }
 216         }
 217 error_pthread_sigmask:
 218 error_fcntl:
 219         for (i = 0; i < 2; i++) {
 220                 ret = close(waitfd[i]);
 221                 if (ret) {
 222                         PERROR("close");
 223                         assert(0);
 224                 }
 225         }
 226 error_pipe:
 227         return NULL;
 228 }
 229
 230 static
 231 struct shm_object *_shm_object_table_alloc_mem(struct shm_object_table *table,
 232                                            size_t memory_map_size)
 233 {
 234         struct shm_object *obj;
 235         void *memory_map;
 236         int waitfd[2], i, ret;
 237
 238         if (table->allocated_len >= table->size)
 239                 return NULL;
 240         obj = &table->objects[table->allocated_len];
 241
 242         memory_map = zmalloc(memory_map_size);
 243         if (!memory_map)
 244                 goto alloc_error;
 245
 246         /* wait_fd: create pipe */
 247         ret = pipe(waitfd);
 248         if (ret < 0) {
 249                 PERROR("pipe");
 250                 goto error_pipe;
 251         }
 252         for (i = 0; i < 2; i++) {
 253                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 254                 if (ret < 0) {
 255                         PERROR("fcntl");
 256                         goto error_fcntl;
 257                 }
 258         }
 259         /* The write end of the pipe needs to be non-blocking */
 260         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 261         if (ret < 0) {
 262                 PERROR("fcntl");
 263                 goto error_fcntl;
 264         }
 265         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 266
 267         /* no shm_fd */
 268         obj->shm_fd = -1;
 269
 270         obj->type = SHM_OBJECT_MEM;
 271         obj->memory_map = memory_map;
 272         obj->memory_map_size = memory_map_size;
 273         obj->allocated_len = 0;
 274         obj->index = table->allocated_len++;
 275
 276         return obj;
 277
 278 error_fcntl:
 279         for (i = 0; i < 2; i++) {
 280                 ret = close(waitfd[i]);
 281                 if (ret) {
 282                         PERROR("close");
 283                         assert(0);
 284                 }
 285         }
 286 error_pipe:
 287         free(memory_map);
 288 alloc_error:
 289         return NULL;
 290 }
 291
 292 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
 293                         size_t memory_map_size,
 294                         enum shm_object_type type)
 295 {
 296         switch (type) {
 297         case SHM_OBJECT_SHM:
 298                 return _shm_object_table_alloc_shm(table, memory_map_size);
 299         case SHM_OBJECT_MEM:
 300                 return _shm_object_table_alloc_mem(table, memory_map_size);
 301         default:
 302                 assert(0);
 303         }
 304         return NULL;
 305 }
 306
 307 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
 308                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
 309                         size_t memory_map_size)
 310 {
 311         struct shm_object *obj;
 312         char *memory_map;
 313         int ret;
 314
 315         if (table->allocated_len >= table->size)
 316                 return NULL;
 317         /* streams _must_ be received in sequential order, else fail. */
 318         if (stream_nr + 1 != table->allocated_len)
 319                 return NULL;
 320
 321         obj = &table->objects[table->allocated_len];
 322
 323         /* wait_fd: set write end of the pipe. */
 324         obj->wait_fd[0] = -1;   /* read end is unset */
 325         obj->wait_fd[1] = wakeup_fd;
 326         obj->shm_fd = shm_fd;
 327
 328         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 329         if (ret < 0) {
 330                 PERROR("fcntl");
 331                 goto error_fcntl;
 332         }
 333         /* The write end of the pipe needs to be non-blocking */
 334         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 335         if (ret < 0) {
 336                 PERROR("fcntl");
 337                 goto error_fcntl;
 338         }
 339
 340         /* memory_map: mmap */
 341         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 342                           MAP_SHARED, shm_fd, 0);
 343         if (memory_map == MAP_FAILED) {
 344                 PERROR("mmap");
 345                 goto error_mmap;
 346         }
 347         obj->type = SHM_OBJECT_SHM;
 348         obj->memory_map = memory_map;
 349         obj->memory_map_size = memory_map_size;
 350         obj->allocated_len = memory_map_size;
 351         obj->index = table->allocated_len++;
 352
 353         return obj;
 354
 355 error_fcntl:
 356 error_mmap:
 357         return NULL;
 358 }
 359
 360 /*
 361  * Passing ownership of mem to object.
 362  */
 363 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
 364                         void *mem, size_t memory_map_size, int wakeup_fd)
 365 {
 366         struct shm_object *obj;
 367         int ret;
 368
 369         if (table->allocated_len >= table->size)
 370                 return NULL;
 371         obj = &table->objects[table->allocated_len];
 372
 373         obj->wait_fd[0] = -1;   /* read end is unset */
 374         obj->wait_fd[1] = wakeup_fd;
 375         obj->shm_fd = -1;
 376
 377         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 378         if (ret < 0) {
 379                 PERROR("fcntl");
 380                 goto error_fcntl;
 381         }
 382         /* The write end of the pipe needs to be non-blocking */
 383         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 384         if (ret < 0) {
 385                 PERROR("fcntl");
 386                 goto error_fcntl;
 387         }
 388
 389         obj->type = SHM_OBJECT_MEM;
 390         obj->memory_map = mem;
 391         obj->memory_map_size = memory_map_size;
 392         obj->allocated_len = memory_map_size;
 393         obj->index = table->allocated_len++;
 394
 395         return obj;
 396
 397 error_fcntl:
 398         return NULL;
 399 }
 400
 401 static
 402 void shmp_object_destroy(struct shm_object *obj)
 403 {
 404         switch (obj->type) {
 405         case SHM_OBJECT_SHM:
 406         {
 407                 int ret, i;
 408
 409                 ret = munmap(obj->memory_map, obj->memory_map_size);
 410                 if (ret) {
 411                         PERROR("umnmap");
 412                         assert(0);
 413                 }
 414                 ret = close(obj->shm_fd);
 415                 if (ret) {
 416                         PERROR("close");
 417                         assert(0);
 418                 }
 419                 for (i = 0; i < 2; i++) {
 420                         if (obj->wait_fd[i] < 0)
 421                                 continue;
 422                         ret = close(obj->wait_fd[i]);
 423                         if (ret) {
 424                                 PERROR("close");
 425                                 assert(0);
 426                         }
 427                 }
 428                 break;
 429         }
 430         case SHM_OBJECT_MEM:
 431         {
 432                 int ret, i;
 433
 434                 for (i = 0; i < 2; i++) {
 435                         if (obj->wait_fd[i] < 0)
 436                                 continue;
 437                         ret = close(obj->wait_fd[i]);
 438                         if (ret) {
 439                                 PERROR("close");
 440                                 assert(0);
 441                         }
 442                 }
 443                 free(obj->memory_map);
 444                 break;
 445         }
 446         default:
 447                 assert(0);
 448         }
 449 }
 450
 451 void shm_object_table_destroy(struct shm_object_table *table)
 452 {
 453         int i;
 454
 455         for (i = 0; i < table->allocated_len; i++)
 456                 shmp_object_destroy(&table->objects[i]);
 457         free(table);
 458 }
 459
 460 /*
 461  * zalloc_shm - allocate memory within a shm object.
 462  *
 463  * Shared memory is already zeroed by shmget.
 464  * *NOT* multithread-safe (should be protected by mutex).
 465  * Returns a -1, -1 tuple on error.
 466  */
 467 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len)
 468 {
 469         struct shm_ref ref;
 470         struct shm_ref shm_ref_error = { -1, -1 };
 471
 472         if (obj->memory_map_size - obj->allocated_len < len)
 473                 return shm_ref_error;
 474         ref.index = obj->index;
 475         ref.offset =  obj->allocated_len;
 476         obj->allocated_len += len;
 477         return ref;
 478 }
 479
 480 void align_shm(struct shm_object *obj, size_t align)
 481 {
 482         size_t offset_len = offset_align(obj->allocated_len, align);
 483         obj->allocated_len += offset_len;
 484 }