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/types.h>
  26 #include <sys/stat.h>   /* For mode constants */
  27 #include <fcntl.h>      /* For O_* constants */
  28 #include <assert.h>
  29 #include <stdio.h>
  30 #include <signal.h>
  31 #include <dirent.h>
  32 #include <lttng/align.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 int create_posix_shm(void)
  88 {
  89         char tmp_name[NAME_MAX] = "/ust-shm-tmp-XXXXXX";
  90         int shmfd, ret;
  91
  92         /*
  93          * Allocate shm, and immediately unlink its shm oject, keeping
  94          * only the file descriptor as a reference to the object. If it
  95          * already exists (caused by short race window during which the
  96          * global object exists in a concurrent shm_open), simply retry.
  97          * We specifically do _not_ use the / at the beginning of the
  98          * pathname so that some OS implementations can keep it local to
  99          * the process (POSIX leaves this implementation-defined).
 100          */
 101         do {
 102                 /*
 103                  * Using mktemp filename with O_CREAT | O_EXCL open
 104                  * flags.
 105                  */
 106                 (void) mktemp(tmp_name);
 107                 if (tmp_name[0] == '\0') {
 108                         PERROR("mktemp");
 109                         goto error_shm_open;
 110                 }
 111                 shmfd = shm_open(tmp_name,
 112                                  O_CREAT | O_EXCL | O_RDWR, 0700);
 113         } while (shmfd < 0 && (errno == EEXIST || errno == EACCES));
 114         if (shmfd < 0) {
 115                 PERROR("shm_open");
 116                 goto error_shm_open;
 117         }
 118         ret = shm_unlink(tmp_name);
 119         if (ret < 0 && errno != ENOENT) {
 120                 PERROR("shm_unlink");
 121                 goto error_shm_release;
 122         }
 123         return shmfd;
 124
 125 error_shm_release:
 126         ret = close(shmfd);
 127         if (ret) {
 128                 PERROR("close");
 129                 assert(0);
 130         }
 131 error_shm_open:
 132         return -1;
 133 }
 134
 135 static
 136 int create_shared_file(const char *shm_path)
 137 {
 138         return open(shm_path, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 139 }
 140
 141 static
 142 struct shm_object *_shm_object_table_alloc_shm(struct shm_object_table *table,
 143                                            size_t memory_map_size,
 144                                            const char *shm_path)
 145 {
 146         int shmfd, waitfd[2], ret, i, sigblocked = 0;
 147         struct shm_object *obj;
 148         char *memory_map;
 149         sigset_t all_sigs, orig_sigs;
 150
 151         if (table->allocated_len >= table->size)
 152                 return NULL;
 153         obj = &table->objects[table->allocated_len];
 154
 155         /* wait_fd: create pipe */
 156         ret = pipe(waitfd);
 157         if (ret < 0) {
 158                 PERROR("pipe");
 159                 goto error_pipe;
 160         }
 161         for (i = 0; i < 2; i++) {
 162                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 163                 if (ret < 0) {
 164                         PERROR("fcntl");
 165                         goto error_fcntl;
 166                 }
 167         }
 168         /* The write end of the pipe needs to be non-blocking */
 169         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 170         if (ret < 0) {
 171                 PERROR("fcntl");
 172                 goto error_fcntl;
 173         }
 174         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 175
 176         /* shm_fd: create shm */
 177
 178         /*
 179          * Theoretically, we could leak a shm if the application crashes
 180          * between open and unlink. Disable signals on this thread for
 181          * increased safety against this scenario.
 182          */
 183         sigfillset(&all_sigs);
 184         ret = pthread_sigmask(SIG_BLOCK, &all_sigs, &orig_sigs);
 185         if (ret == -1) {
 186                 PERROR("pthread_sigmask");
 187                 goto error_pthread_sigmask;
 188         }
 189         sigblocked = 1;
 190
 191
 192         if (!shm_path) {
 193                 obj->shm_path[0] = '\0';
 194                 shmfd = create_posix_shm();
 195         } else {
 196                 strncpy(obj->shm_path, shm_path,
 197                         sizeof(obj->shm_path));
 198                 obj->shm_path[sizeof(obj->shm_path) - 1] = '\0';
 199
 200                 /* Path should already exist, but could fail. */
 201                 shmfd = create_shared_file(shm_path);
 202         }
 203         if (shmfd < 0)
 204                 goto error_shm_open;
 205
 206         sigblocked = 0;
 207         ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
 208         if (ret == -1) {
 209                 PERROR("pthread_sigmask");
 210                 goto error_sigmask_release;
 211         }
 212         ret = zero_file(shmfd, memory_map_size);
 213         if (ret) {
 214                 PERROR("zero_file");
 215                 goto error_zero_file;
 216         }
 217         ret = ftruncate(shmfd, memory_map_size);
 218         if (ret) {
 219                 PERROR("ftruncate");
 220                 goto error_ftruncate;
 221         }
 222         obj->shm_fd = shmfd;
 223
 224         /* memory_map: mmap */
 225         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 226                           MAP_SHARED, shmfd, 0);
 227         if (memory_map == MAP_FAILED) {
 228                 PERROR("mmap");
 229                 goto error_mmap;
 230         }
 231         obj->type = SHM_OBJECT_SHM;
 232         obj->memory_map = memory_map;
 233         obj->memory_map_size = memory_map_size;
 234         obj->allocated_len = 0;
 235         obj->index = table->allocated_len++;
 236
 237         return obj;
 238
 239 error_mmap:
 240 error_ftruncate:
 241 error_zero_file:
 242 error_sigmask_release:
 243         ret = close(shmfd);
 244         if (ret) {
 245                 PERROR("close");
 246                 assert(0);
 247         }
 248         if (shm_path) {
 249                 ret = unlink(shm_path);
 250                 if (ret) {
 251                         PERROR("ret");
 252                 }
 253         }
 254 error_shm_open:
 255         if (sigblocked) {
 256                 ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
 257                 if (ret == -1) {
 258                         PERROR("pthread_sigmask");
 259                 }
 260         }
 261 error_pthread_sigmask:
 262 error_fcntl:
 263         for (i = 0; i < 2; i++) {
 264                 ret = close(waitfd[i]);
 265                 if (ret) {
 266                         PERROR("close");
 267                         assert(0);
 268                 }
 269         }
 270 error_pipe:
 271         return NULL;
 272 }
 273
 274 static
 275 struct shm_object *_shm_object_table_alloc_mem(struct shm_object_table *table,
 276                                            size_t memory_map_size)
 277 {
 278         struct shm_object *obj;
 279         void *memory_map;
 280         int waitfd[2], i, ret;
 281
 282         if (table->allocated_len >= table->size)
 283                 return NULL;
 284         obj = &table->objects[table->allocated_len];
 285
 286         memory_map = zmalloc(memory_map_size);
 287         if (!memory_map)
 288                 goto alloc_error;
 289
 290         /* wait_fd: create pipe */
 291         ret = pipe(waitfd);
 292         if (ret < 0) {
 293                 PERROR("pipe");
 294                 goto error_pipe;
 295         }
 296         for (i = 0; i < 2; i++) {
 297                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 298                 if (ret < 0) {
 299                         PERROR("fcntl");
 300                         goto error_fcntl;
 301                 }
 302         }
 303         /* The write end of the pipe needs to be non-blocking */
 304         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 305         if (ret < 0) {
 306                 PERROR("fcntl");
 307                 goto error_fcntl;
 308         }
 309         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 310
 311         /* no shm_fd */
 312         obj->shm_fd = -1;
 313
 314         obj->type = SHM_OBJECT_MEM;
 315         obj->memory_map = memory_map;
 316         obj->memory_map_size = memory_map_size;
 317         obj->allocated_len = 0;
 318         obj->index = table->allocated_len++;
 319
 320         return obj;
 321
 322 error_fcntl:
 323         for (i = 0; i < 2; i++) {
 324                 ret = close(waitfd[i]);
 325                 if (ret) {
 326                         PERROR("close");
 327                         assert(0);
 328                 }
 329         }
 330 error_pipe:
 331         free(memory_map);
 332 alloc_error:
 333         return NULL;
 334 }
 335
 336 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
 337                         size_t memory_map_size,
 338                         enum shm_object_type type,
 339                         const char *shm_path)
 340 {
 341         switch (type) {
 342         case SHM_OBJECT_SHM:
 343                 return _shm_object_table_alloc_shm(table, memory_map_size,
 344                                 shm_path);
 345         case SHM_OBJECT_MEM:
 346                 return _shm_object_table_alloc_mem(table, memory_map_size);
 347         default:
 348                 assert(0);
 349         }
 350         return NULL;
 351 }
 352
 353 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
 354                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
 355                         size_t memory_map_size)
 356 {
 357         struct shm_object *obj;
 358         char *memory_map;
 359         int ret;
 360
 361         if (table->allocated_len >= table->size)
 362                 return NULL;
 363         /* streams _must_ be received in sequential order, else fail. */
 364         if (stream_nr + 1 != table->allocated_len)
 365                 return NULL;
 366
 367         obj = &table->objects[table->allocated_len];
 368
 369         /* wait_fd: set write end of the pipe. */
 370         obj->wait_fd[0] = -1;   /* read end is unset */
 371         obj->wait_fd[1] = wakeup_fd;
 372         obj->shm_fd = shm_fd;
 373
 374         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 375         if (ret < 0) {
 376                 PERROR("fcntl");
 377                 goto error_fcntl;
 378         }
 379         /* The write end of the pipe needs to be non-blocking */
 380         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 381         if (ret < 0) {
 382                 PERROR("fcntl");
 383                 goto error_fcntl;
 384         }
 385
 386         /* memory_map: mmap */
 387         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 388                           MAP_SHARED, shm_fd, 0);
 389         if (memory_map == MAP_FAILED) {
 390                 PERROR("mmap");
 391                 goto error_mmap;
 392         }
 393         obj->type = SHM_OBJECT_SHM;
 394         obj->memory_map = memory_map;
 395         obj->memory_map_size = memory_map_size;
 396         obj->allocated_len = memory_map_size;
 397         obj->index = table->allocated_len++;
 398
 399         return obj;
 400
 401 error_fcntl:
 402 error_mmap:
 403         return NULL;
 404 }
 405
 406 /*
 407  * Passing ownership of mem to object.
 408  */
 409 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
 410                         void *mem, size_t memory_map_size, int wakeup_fd)
 411 {
 412         struct shm_object *obj;
 413         int ret;
 414
 415         if (table->allocated_len >= table->size)
 416                 return NULL;
 417         obj = &table->objects[table->allocated_len];
 418
 419         obj->wait_fd[0] = -1;   /* read end is unset */
 420         obj->wait_fd[1] = wakeup_fd;
 421         obj->shm_fd = -1;
 422
 423         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 424         if (ret < 0) {
 425                 PERROR("fcntl");
 426                 goto error_fcntl;
 427         }
 428         /* The write end of the pipe needs to be non-blocking */
 429         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 430         if (ret < 0) {
 431                 PERROR("fcntl");
 432                 goto error_fcntl;
 433         }
 434
 435         obj->type = SHM_OBJECT_MEM;
 436         obj->memory_map = mem;
 437         obj->memory_map_size = memory_map_size;
 438         obj->allocated_len = memory_map_size;
 439         obj->index = table->allocated_len++;
 440
 441         return obj;
 442
 443 error_fcntl:
 444         return NULL;
 445 }
 446
 447 static
 448 void shmp_object_destroy(struct shm_object *obj)
 449 {
 450         switch (obj->type) {
 451         case SHM_OBJECT_SHM:
 452         {
 453                 int ret, i;
 454
 455                 ret = munmap(obj->memory_map, obj->memory_map_size);
 456                 if (ret) {
 457                         PERROR("umnmap");
 458                         assert(0);
 459                 }
 460                 ret = close(obj->shm_fd);
 461                 if (ret) {
 462                         PERROR("close");
 463                         assert(0);
 464                 }
 465                 if (obj->shm_path[0]) {
 466                         ret = unlink(obj->shm_path);
 467                         if (ret) {
 468                                 PERROR("ret");
 469                         }
 470                 }
 471                 for (i = 0; i < 2; i++) {
 472                         if (obj->wait_fd[i] < 0)
 473                                 continue;
 474                         ret = close(obj->wait_fd[i]);
 475                         if (ret) {
 476                                 PERROR("close");
 477                                 assert(0);
 478                         }
 479                 }
 480                 break;
 481         }
 482         case SHM_OBJECT_MEM:
 483         {
 484                 int ret, i;
 485
 486                 for (i = 0; i < 2; i++) {
 487                         if (obj->wait_fd[i] < 0)
 488                                 continue;
 489                         ret = close(obj->wait_fd[i]);
 490                         if (ret) {
 491                                 PERROR("close");
 492                                 assert(0);
 493                         }
 494                 }
 495                 free(obj->memory_map);
 496                 break;
 497         }
 498         default:
 499                 assert(0);
 500         }
 501 }
 502
 503 void shm_object_table_destroy(struct shm_object_table *table)
 504 {
 505         int i;
 506
 507         for (i = 0; i < table->allocated_len; i++)
 508                 shmp_object_destroy(&table->objects[i]);
 509         free(table);
 510 }
 511
 512 /*
 513  * zalloc_shm - allocate memory within a shm object.
 514  *
 515  * Shared memory is already zeroed by shmget.
 516  * *NOT* multithread-safe (should be protected by mutex).
 517  * Returns a -1, -1 tuple on error.
 518  */
 519 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len)
 520 {
 521         struct shm_ref ref;
 522         struct shm_ref shm_ref_error = { -1, -1 };
 523
 524         if (obj->memory_map_size - obj->allocated_len < len)
 525                 return shm_ref_error;
 526         ref.index = obj->index;
 527         ref.offset =  obj->allocated_len;
 528         obj->allocated_len += len;
 529         return ref;
 530 }
 531
 532 void align_shm(struct shm_object *obj, size_t align)
 533 {
 534         size_t offset_len = offset_align(obj->allocated_len, align);
 535         obj->allocated_len += offset_len;
 536 }