librt/shm.c

   1 /* Copyright (C) 2009 Bernhard Reutner-Fischer <uclibc@uclibc.org>
   2  *
   3  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
   4  */
   5
   6 #include <features.h>
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9 #include <sys/mman.h>
  10 #include <fcntl.h>
  11 #include <unistd.h>
  12 #include <stdlib.h>
  13 #include <stdio.h>
  14 #include <errno.h>
  15
  16 #ifndef _PATH_SHM
  17 #define _PATH_SHM "/dev/shm/"
  18 #endif
  19
  20 #ifndef NAME_MAX
  21 #define NAME_MAX 255
  22 #endif
  23
  24 /* Get name of dummy shm operation handle.
  25  * Returns a malloc'ed buffer containing the OS specific path
  26  * to the shm filename or NULL upon failure.
  27  */
  28 static __attribute_noinline__ char* get_shm_name(const char *name) __nonnull((1));
  29 static char* get_shm_name(const char *name)
  30 {
  31         char *path;
  32         int i;
  33
  34         /* Skip leading slashes */
  35         while (*name == '/')
  36                 ++name;
  37 #ifdef __USE_GNU
  38         i = asprintf(&path, _PATH_SHM "%s", name);
  39         if (i < 0)
  40                 return NULL;
  41 #else
  42         path = malloc(NAME_MAX);
  43         if (path == NULL)
  44                 return NULL;
  45         i = snprintf(path, NAME_MAX, _PATH_SHM "%s", name);
  46         if (i < 0) {
  47                 free(path);
  48                 return NULL;
  49         } else if (i >= NAME_MAX) {
  50                 free(path);
  51                 __set_errno(ENAMETOOLONG);
  52                 return NULL;
  53         }
  54 #endif
  55         return path;
  56 }
  57
  58 int shm_open(const char *name, int oflag, mode_t mode)
  59 {
  60         int fd;
  61         char *shm_name = get_shm_name(name);
  62
  63         /* Stripped multiple '/' from start; may have set errno properly */
  64         if (shm_name == NULL)
  65                 return -1;
  66         /* The FD_CLOEXEC file descriptor flag associated with the new
  67          * file descriptor is set.  */
  68 #ifdef O_CLOEXEC
  69          /* Just open it with CLOEXEC set, for brevity */
  70         fd = open(shm_name, oflag | O_CLOEXEC, mode);
  71 #else
  72         fd = open(shm_name, oflag, mode);
  73         if (fd >= 0) {
  74                 fcntl(fd, F_SETFD, FD_CLOEXEC);
  75                 /* thus far, {G,S}ETFD only has this single flag,
  76                  * and setting it never fails.
  77                  *int fdflags = fcntl(fd, F_GETFD);
  78                  *if (fdflags >= 0)
  79                  *      fdflags = fcntl(fd, F_SETFD, fdflags | FD_CLOEXEC);
  80                  *if (fdflags < 0) {
  81                  *      close(fd);
  82                  *      fd = -1;
  83                  *}
  84                  */
  85         }
  86 #endif
  87         free(shm_name); /* doesn't affect errno */
  88         return fd;
  89 }
  90
  91 int shm_unlink(const char *name)
  92 {
  93         char *shm_name = get_shm_name(name);
  94         int ret;
  95
  96         /* Stripped multiple '/' from start; may have set errno properly */
  97         if (shm_name == NULL)
  98                 return -1;
  99         ret = unlink(shm_name);
 100         free(shm_name); /* doesn't affect errno */
 101         return ret;
 102 }