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 struct shm_object *_shm_object_table_alloc_shm(struct shm_object_table *table,
  88                                            size_t memory_map_size,
  89                                            int stream_fd)
  90 {
  91         int shmfd, waitfd[2], ret, i;
  92         struct shm_object *obj;
  93         char *memory_map;
  94
  95         if (stream_fd < 0)
  96                 return NULL;
  97         if (table->allocated_len >= table->size)
  98                 return NULL;
  99         obj = &table->objects[table->allocated_len];
 100
 101         /* wait_fd: create pipe */
 102         ret = pipe(waitfd);
 103         if (ret < 0) {
 104                 PERROR("pipe");
 105                 goto error_pipe;
 106         }
 107         for (i = 0; i < 2; i++) {
 108                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 109                 if (ret < 0) {
 110                         PERROR("fcntl");
 111                         goto error_fcntl;
 112                 }
 113         }
 114         /* The write end of the pipe needs to be non-blocking */
 115         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 116         if (ret < 0) {
 117                 PERROR("fcntl");
 118                 goto error_fcntl;
 119         }
 120         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 121
 122         /* create shm */
 123
 124         shmfd = stream_fd;
 125         ret = zero_file(shmfd, memory_map_size);
 126         if (ret) {
 127                 PERROR("zero_file");
 128                 goto error_zero_file;
 129         }
 130         ret = ftruncate(shmfd, memory_map_size);
 131         if (ret) {
 132                 PERROR("ftruncate");
 133                 goto error_ftruncate;
 134         }
 135         obj->shm_fd_ownership = 0;
 136         obj->shm_fd = shmfd;
 137
 138         /* memory_map: mmap */
 139         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 140                           MAP_SHARED, shmfd, 0);
 141         if (memory_map == MAP_FAILED) {
 142                 PERROR("mmap");
 143                 goto error_mmap;
 144         }
 145         obj->type = SHM_OBJECT_SHM;
 146         obj->memory_map = memory_map;
 147         obj->memory_map_size = memory_map_size;
 148         obj->allocated_len = 0;
 149         obj->index = table->allocated_len++;
 150
 151         return obj;
 152
 153 error_mmap:
 154 error_ftruncate:
 155 error_zero_file:
 156 error_fcntl:
 157         for (i = 0; i < 2; i++) {
 158                 ret = close(waitfd[i]);
 159                 if (ret) {
 160                         PERROR("close");
 161                         assert(0);
 162                 }
 163         }
 164 error_pipe:
 165         return NULL;
 166 }
 167
 168 static
 169 struct shm_object *_shm_object_table_alloc_mem(struct shm_object_table *table,
 170                                            size_t memory_map_size)
 171 {
 172         struct shm_object *obj;
 173         void *memory_map;
 174         int waitfd[2], i, ret;
 175
 176         if (table->allocated_len >= table->size)
 177                 return NULL;
 178         obj = &table->objects[table->allocated_len];
 179
 180         memory_map = zmalloc(memory_map_size);
 181         if (!memory_map)
 182                 goto alloc_error;
 183
 184         /* wait_fd: create pipe */
 185         ret = pipe(waitfd);
 186         if (ret < 0) {
 187                 PERROR("pipe");
 188                 goto error_pipe;
 189         }
 190         for (i = 0; i < 2; i++) {
 191                 ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC);
 192                 if (ret < 0) {
 193                         PERROR("fcntl");
 194                         goto error_fcntl;
 195                 }
 196         }
 197         /* The write end of the pipe needs to be non-blocking */
 198         ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK);
 199         if (ret < 0) {
 200                 PERROR("fcntl");
 201                 goto error_fcntl;
 202         }
 203         memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 204
 205         /* no shm_fd */
 206         obj->shm_fd = -1;
 207         obj->shm_fd_ownership = 0;
 208
 209         obj->type = SHM_OBJECT_MEM;
 210         obj->memory_map = memory_map;
 211         obj->memory_map_size = memory_map_size;
 212         obj->allocated_len = 0;
 213         obj->index = table->allocated_len++;
 214
 215         return obj;
 216
 217 error_fcntl:
 218         for (i = 0; i < 2; i++) {
 219                 ret = close(waitfd[i]);
 220                 if (ret) {
 221                         PERROR("close");
 222                         assert(0);
 223                 }
 224         }
 225 error_pipe:
 226         free(memory_map);
 227 alloc_error:
 228         return NULL;
 229 }
 230
 231 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
 232                         size_t memory_map_size,
 233                         enum shm_object_type type,
 234                         int stream_fd)
 235 {
 236         switch (type) {
 237         case SHM_OBJECT_SHM:
 238                 return _shm_object_table_alloc_shm(table, memory_map_size,
 239                                 stream_fd);
 240         case SHM_OBJECT_MEM:
 241                 return _shm_object_table_alloc_mem(table, memory_map_size);
 242         default:
 243                 assert(0);
 244         }
 245         return NULL;
 246 }
 247
 248 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
 249                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
 250                         size_t memory_map_size)
 251 {
 252         struct shm_object *obj;
 253         char *memory_map;
 254         int ret;
 255
 256         if (table->allocated_len >= table->size)
 257                 return NULL;
 258         /* streams _must_ be received in sequential order, else fail. */
 259         if (stream_nr + 1 != table->allocated_len)
 260                 return NULL;
 261
 262         obj = &table->objects[table->allocated_len];
 263
 264         /* wait_fd: set write end of the pipe. */
 265         obj->wait_fd[0] = -1;   /* read end is unset */
 266         obj->wait_fd[1] = wakeup_fd;
 267         obj->shm_fd = shm_fd;
 268         obj->shm_fd_ownership = 1;
 269
 270         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 271         if (ret < 0) {
 272                 PERROR("fcntl");
 273                 goto error_fcntl;
 274         }
 275         /* The write end of the pipe needs to be non-blocking */
 276         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 277         if (ret < 0) {
 278                 PERROR("fcntl");
 279                 goto error_fcntl;
 280         }
 281
 282         /* memory_map: mmap */
 283         memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
 284                           MAP_SHARED, shm_fd, 0);
 285         if (memory_map == MAP_FAILED) {
 286                 PERROR("mmap");
 287                 goto error_mmap;
 288         }
 289         obj->type = SHM_OBJECT_SHM;
 290         obj->memory_map = memory_map;
 291         obj->memory_map_size = memory_map_size;
 292         obj->allocated_len = memory_map_size;
 293         obj->index = table->allocated_len++;
 294
 295         return obj;
 296
 297 error_fcntl:
 298 error_mmap:
 299         return NULL;
 300 }
 301
 302 /*
 303  * Passing ownership of mem to object.
 304  */
 305 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
 306                         void *mem, size_t memory_map_size, int wakeup_fd)
 307 {
 308         struct shm_object *obj;
 309         int ret;
 310
 311         if (table->allocated_len >= table->size)
 312                 return NULL;
 313         obj = &table->objects[table->allocated_len];
 314
 315         obj->wait_fd[0] = -1;   /* read end is unset */
 316         obj->wait_fd[1] = wakeup_fd;
 317         obj->shm_fd = -1;
 318         obj->shm_fd_ownership = 0;
 319
 320         ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
 321         if (ret < 0) {
 322                 PERROR("fcntl");
 323                 goto error_fcntl;
 324         }
 325         /* The write end of the pipe needs to be non-blocking */
 326         ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 327         if (ret < 0) {
 328                 PERROR("fcntl");
 329                 goto error_fcntl;
 330         }
 331
 332         obj->type = SHM_OBJECT_MEM;
 333         obj->memory_map = mem;
 334         obj->memory_map_size = memory_map_size;
 335         obj->allocated_len = memory_map_size;
 336         obj->index = table->allocated_len++;
 337
 338         return obj;
 339
 340 error_fcntl:
 341         return NULL;
 342 }
 343
 344 static
 345 void shmp_object_destroy(struct shm_object *obj)
 346 {
 347         switch (obj->type) {
 348         case SHM_OBJECT_SHM:
 349         {
 350                 int ret, i;
 351
 352                 ret = munmap(obj->memory_map, obj->memory_map_size);
 353                 if (ret) {
 354                         PERROR("umnmap");
 355                         assert(0);
 356                 }
 357                 if (obj->shm_fd_ownership) {
 358                         ret = close(obj->shm_fd);
 359                         if (ret) {
 360                                 PERROR("close");
 361                                 assert(0);
 362                         }
 363                 }
 364                 for (i = 0; i < 2; i++) {
 365                         if (obj->wait_fd[i] < 0)
 366                                 continue;
 367                         ret = close(obj->wait_fd[i]);
 368                         if (ret) {
 369                                 PERROR("close");
 370                                 assert(0);
 371                         }
 372                 }
 373                 break;
 374         }
 375         case SHM_OBJECT_MEM:
 376         {
 377                 int ret, i;
 378
 379                 for (i = 0; i < 2; i++) {
 380                         if (obj->wait_fd[i] < 0)
 381                                 continue;
 382                         ret = close(obj->wait_fd[i]);
 383                         if (ret) {
 384                                 PERROR("close");
 385                                 assert(0);
 386                         }
 387                 }
 388                 free(obj->memory_map);
 389                 break;
 390         }
 391         default:
 392                 assert(0);
 393         }
 394 }
 395
 396 void shm_object_table_destroy(struct shm_object_table *table)
 397 {
 398         int i;
 399
 400         for (i = 0; i < table->allocated_len; i++)
 401                 shmp_object_destroy(&table->objects[i]);
 402         free(table);
 403 }
 404
 405 /*
 406  * zalloc_shm - allocate memory within a shm object.
 407  *
 408  * Shared memory is already zeroed by shmget.
 409  * *NOT* multithread-safe (should be protected by mutex).
 410  * Returns a -1, -1 tuple on error.
 411  */
 412 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len)
 413 {
 414         struct shm_ref ref;
 415         struct shm_ref shm_ref_error = { -1, -1 };
 416
 417         if (obj->memory_map_size - obj->allocated_len < len)
 418                 return shm_ref_error;
 419         ref.index = obj->index;
 420         ref.offset =  obj->allocated_len;
 421         obj->allocated_len += len;
 422         return ref;
 423 }
 424
 425 void align_shm(struct shm_object *obj, size_t align)
 426 {
 427         size_t offset_len = offset_align(obj->allocated_len, align);
 428         obj->allocated_len += offset_len;
 429 }