src/pulsecore/shm.c

   1 /***
   2     This file is part of PulseAudio.
   3
   4     Copyright 2006 Lennart Poettering
   5     Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
   6
   7     PulseAudio is free software; you can redistribute it and/or modify
   8     it under the terms of the GNU Lesser General Public License as
   9     published by the Free Software Foundation; either version 2.1 of the
  10     License, or (at your option) any later version.
  11
  12     PulseAudio is distributed in the hope that it will be useful, but
  13     WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15     Lesser General Public License for more details.
  16
  17     You should have received a copy of the GNU Lesser General Public
  18     License along with PulseAudio; if not, write to the Free Software
  19     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  20     USA.
  21 ***/
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 #include <stdlib.h>
  28 #include <unistd.h>
  29 #include <fcntl.h>
  30 #include <stdio.h>
  31 #include <errno.h>
  32 #include <string.h>
  33 #include <sys/stat.h>
  34 #include <sys/types.h>
  35 #include <dirent.h>
  36 #include <signal.h>
  37
  38 #ifdef HAVE_SYS_MMAN_H
  39 #include <sys/mman.h>
  40 #endif
  41
  42 /* This is deprecated on glibc but is still used by FreeBSD */
  43 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
  44 # define MAP_ANONYMOUS MAP_ANON
  45 #endif
  46
  47 #include <pulse/xmalloc.h>
  48 #include <pulse/gccmacro.h>
  49
  50 #include <pulsecore/core-error.h>
  51 #include <pulsecore/log.h>
  52 #include <pulsecore/random.h>
  53 #include <pulsecore/core-util.h>
  54 #include <pulsecore/macro.h>
  55 #include <pulsecore/atomic.h>
  56
  57 #include "shm.h"
  58
  59 #if defined(__linux__) && !defined(MADV_REMOVE)
  60 #define MADV_REMOVE 9
  61 #endif
  62
  63 /* 1 GiB at max */
  64 #define MAX_SHM_SIZE (PA_ALIGN(1024*1024*1024))
  65
  66 #ifdef __linux__
  67 /* On Linux we know that the shared memory blocks are files in
  68  * /dev/shm. We can use that information to list all blocks and
  69  * cleanup unused ones */
  70 #define SHM_PATH "/dev/shm/"
  71 #else
  72 #undef SHM_PATH
  73 #endif
  74
  75 #define SHM_MARKER ((int) 0xbeefcafe)
  76
  77 /* We now put this SHM marker at the end of each segment. It's
  78  * optional, to not require a reboot when upgrading, though. Note that
  79  * on multiarch systems 32bit and 64bit processes might access this
  80  * region simultaneously. The header fields need to be independant
  81  * from the process' word with */
  82 struct shm_marker {
  83     pa_atomic_t marker; /* 0xbeefcafe */
  84     pa_atomic_t pid;
  85     uint64_t _reserved1;
  86     uint64_t _reserved2;
  87     uint64_t _reserved3;
  88     uint64_t _reserved4;
  89 } PA_GCC_PACKED;
  90
  91 #define SHM_MARKER_SIZE PA_ALIGN(sizeof(struct shm_marker))
  92
  93 static char *segment_name(char *fn, size_t l, unsigned id) {
  94     pa_snprintf(fn, l, "/pulse-shm-%u", id);
  95     return fn;
  96 }
  97
  98 int pa_shm_create_rw(pa_shm *m, size_t size, pa_bool_t shared, mode_t mode) {
  99     char fn[32];
 100     int fd = -1;
 101
 102     pa_assert(m);
 103     pa_assert(size > 0);
 104     pa_assert(size <= MAX_SHM_SIZE);
 105     pa_assert(mode >= 0600);
 106
 107     /* Each time we create a new SHM area, let's first drop all stale
 108      * ones */
 109     pa_shm_cleanup();
 110
 111     /* Round up to make it page aligned */
 112     size = PA_PAGE_ALIGN(size);
 113
 114     if (!shared) {
 115         m->id = 0;
 116         m->size = size;
 117
 118 #ifdef MAP_ANONYMOUS
 119         if ((m->ptr = mmap(NULL, m->size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, (off_t) 0)) == MAP_FAILED) {
 120             pa_log("mmap() failed: %s", pa_cstrerror(errno));
 121             goto fail;
 122         }
 123 #elif defined(HAVE_POSIX_MEMALIGN)
 124         {
 125             int r;
 126
 127             if ((r = posix_memalign(&m->ptr, PA_PAGE_SIZE, size)) < 0) {
 128                 pa_log("posix_memalign() failed: %s", pa_cstrerror(r));
 129                 goto fail;
 130             }
 131         }
 132 #else
 133         m->ptr = pa_xmalloc(m->size);
 134 #endif
 135
 136         m->do_unlink = FALSE;
 137
 138     } else {
 139 #ifdef HAVE_SHM_OPEN
 140         struct shm_marker *marker;
 141
 142         pa_random(&m->id, sizeof(m->id));
 143         segment_name(fn, sizeof(fn), m->id);
 144
 145         if ((fd = shm_open(fn, O_RDWR|O_CREAT|O_EXCL, mode & 0444)) < 0) {
 146             pa_log("shm_open() failed: %s", pa_cstrerror(errno));
 147             goto fail;
 148         }
 149
 150         m->size = size + SHM_MARKER_SIZE;
 151
 152         if (ftruncate(fd, (off_t) m->size) < 0) {
 153             pa_log("ftruncate() failed: %s", pa_cstrerror(errno));
 154             goto fail;
 155         }
 156
 157         if ((m->ptr = mmap(NULL, PA_PAGE_ALIGN(m->size), PROT_READ|PROT_WRITE, MAP_SHARED, fd, (off_t) 0)) == MAP_FAILED) {
 158             pa_log("mmap() failed: %s", pa_cstrerror(errno));
 159             goto fail;
 160         }
 161
 162         /* We store our PID at the end of the shm block, so that we
 163          * can check for dead shm segments later */
 164         marker = (struct shm_marker*) ((uint8_t*) m->ptr + m->size - SHM_MARKER_SIZE);
 165         pa_atomic_store(&marker->pid, (int) getpid());
 166         pa_atomic_store(&marker->marker, SHM_MARKER);
 167
 168         pa_assert_se(pa_close(fd) == 0);
 169         m->do_unlink = TRUE;
 170 #else
 171         return -1;
 172 #endif
 173     }
 174
 175     m->shared = shared;
 176
 177     return 0;
 178
 179 fail:
 180
 181 #ifdef HAVE_SHM_OPEN
 182     if (fd >= 0) {
 183         shm_unlink(fn);
 184         pa_close(fd);
 185     }
 186 #endif
 187
 188     return -1;
 189 }
 190
 191 void pa_shm_free(pa_shm *m) {
 192     pa_assert(m);
 193     pa_assert(m->ptr);
 194     pa_assert(m->size > 0);
 195
 196 #ifdef MAP_FAILED
 197     pa_assert(m->ptr != MAP_FAILED);
 198 #endif
 199
 200     if (!m->shared) {
 201 #ifdef MAP_ANONYMOUS
 202         if (munmap(m->ptr, m->size) < 0)
 203             pa_log("munmap() failed: %s", pa_cstrerror(errno));
 204 #elif defined(HAVE_POSIX_MEMALIGN)
 205         free(m->ptr);
 206 #else
 207         pa_xfree(m->ptr);
 208 #endif
 209     } else {
 210 #ifdef HAVE_SHM_OPEN
 211         if (munmap(m->ptr, PA_PAGE_ALIGN(m->size)) < 0)
 212             pa_log("munmap() failed: %s", pa_cstrerror(errno));
 213
 214         if (m->do_unlink) {
 215             char fn[32];
 216
 217             segment_name(fn, sizeof(fn), m->id);
 218
 219             if (shm_unlink(fn) < 0)
 220                 pa_log(" shm_unlink(%s) failed: %s", fn, pa_cstrerror(errno));
 221         }
 222 #else
 223         /* We shouldn't be here without shm support */
 224         pa_assert_not_reached();
 225 #endif
 226     }
 227
 228     pa_zero(*m);
 229 }
 230
 231 void pa_shm_punch(pa_shm *m, size_t offset, size_t size) {
 232     void *ptr;
 233     size_t o;
 234
 235     pa_assert(m);
 236     pa_assert(m->ptr);
 237     pa_assert(m->size > 0);
 238     pa_assert(offset+size <= m->size);
 239
 240 #ifdef MAP_FAILED
 241     pa_assert(m->ptr != MAP_FAILED);
 242 #endif
 243
 244     /* You're welcome to implement this as NOOP on systems that don't
 245      * support it */
 246
 247     /* Align the pointer up to multiples of the page size */
 248     ptr = (uint8_t*) m->ptr + offset;
 249     o = (size_t) ((uint8_t*) ptr - (uint8_t*) PA_PAGE_ALIGN_PTR(ptr));
 250
 251     if (o > 0) {
 252         size_t delta = PA_PAGE_SIZE - o;
 253         ptr = (uint8_t*) ptr + delta;
 254         size -= delta;
 255     }
 256
 257     /* Align the size down to multiples of page size */
 258     size = (size / PA_PAGE_SIZE) * PA_PAGE_SIZE;
 259
 260 #ifdef MADV_REMOVE
 261     if (madvise(ptr, size, MADV_REMOVE) >= 0)
 262         return;
 263 #endif
 264
 265 #ifdef MADV_FREE
 266     if (madvise(ptr, size, MADV_FREE) >= 0)
 267         return;
 268 #endif
 269
 270 #ifdef MADV_DONTNEED
 271     madvise(ptr, size, MADV_DONTNEED);
 272 #elif defined(POSIX_MADV_DONTNEED)
 273     posix_madvise(ptr, size, POSIX_MADV_DONTNEED);
 274 #endif
 275 }
 276
 277 #ifdef HAVE_SHM_OPEN
 278
 279 int pa_shm_attach_ro(pa_shm *m, unsigned id) {
 280     char fn[32];
 281     int fd = -1;
 282     struct stat st;
 283
 284     pa_assert(m);
 285
 286     segment_name(fn, sizeof(fn), m->id = id);
 287
 288     if ((fd = shm_open(fn, O_RDONLY, 0)) < 0) {
 289         if (errno != EACCES)
 290             pa_log("shm_open() failed: %s", pa_cstrerror(errno));
 291         goto fail;
 292     }
 293
 294     if (fstat(fd, &st) < 0) {
 295         pa_log("fstat() failed: %s", pa_cstrerror(errno));
 296         goto fail;
 297     }
 298
 299     if (st.st_size <= 0 ||
 300         st.st_size > (off_t) (MAX_SHM_SIZE+SHM_MARKER_SIZE) ||
 301         PA_ALIGN((size_t) st.st_size) != (size_t) st.st_size) {
 302         pa_log("Invalid shared memory segment size");
 303         goto fail;
 304     }
 305
 306     m->size = (size_t) st.st_size;
 307
 308     if ((m->ptr = mmap(NULL, PA_PAGE_ALIGN(m->size), PROT_READ, MAP_SHARED, fd, (off_t) 0)) == MAP_FAILED) {
 309         pa_log("mmap() failed: %s", pa_cstrerror(errno));
 310         goto fail;
 311     }
 312
 313     m->do_unlink = FALSE;
 314     m->shared = TRUE;
 315
 316     pa_assert_se(pa_close(fd) == 0);
 317
 318     return 0;
 319
 320 fail:
 321     if (fd >= 0)
 322         pa_close(fd);
 323
 324     return -1;
 325 }
 326
 327 #else /* HAVE_SHM_OPEN */
 328
 329 int pa_shm_attach_ro(pa_shm *m, unsigned id) {
 330     return -1;
 331 }
 332
 333 #endif /* HAVE_SHM_OPEN */
 334
 335 int pa_shm_cleanup(void) {
 336
 337 #ifdef HAVE_SHM_OPEN
 338 #ifdef SHM_PATH
 339     DIR *d;
 340     struct dirent *de;
 341
 342     if (!(d = opendir(SHM_PATH))) {
 343         pa_log_warn("Failed to read "SHM_PATH": %s", pa_cstrerror(errno));
 344         return -1;
 345     }
 346
 347     while ((de = readdir(d))) {
 348         pa_shm seg;
 349         unsigned id;
 350         pid_t pid;
 351         char fn[128];
 352         struct shm_marker *m;
 353
 354         if (strncmp(de->d_name, "pulse-shm-", 10))
 355             continue;
 356
 357         if (pa_atou(de->d_name + 10, &id) < 0)
 358             continue;
 359
 360         if (pa_shm_attach_ro(&seg, id) < 0)
 361             continue;
 362
 363         if (seg.size < SHM_MARKER_SIZE) {
 364             pa_shm_free(&seg);
 365             continue;
 366         }
 367
 368         m = (struct shm_marker*) ((uint8_t*) seg.ptr + seg.size - SHM_MARKER_SIZE);
 369
 370         if (pa_atomic_load(&m->marker) != SHM_MARKER) {
 371             pa_shm_free(&seg);
 372             continue;
 373         }
 374
 375         if (!(pid = (pid_t) pa_atomic_load(&m->pid))) {
 376             pa_shm_free(&seg);
 377             continue;
 378         }
 379
 380         if (kill(pid, 0) == 0 || errno != ESRCH) {
 381             pa_shm_free(&seg);
 382             continue;
 383         }
 384
 385         pa_shm_free(&seg);
 386
 387         /* Ok, the owner of this shms segment is dead, so, let's remove the segment */
 388         segment_name(fn, sizeof(fn), id);
 389
 390         if (shm_unlink(fn) < 0 && errno != EACCES && errno != ENOENT)
 391             pa_log_warn("Failed to remove SHM segment %s: %s\n", fn, pa_cstrerror(errno));
 392     }
 393
 394     closedir(d);
 395 #endif /* SHM_PATH */
 396 #endif /* HAVE_SHM_OPEN */
 397
 398     return 0;
 399 }