src/util/anon_file.c

   1 /*
   2  * Copyright © 2012 Collabora, Ltd.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the
  13  * next paragraph) shall be included in all copies or substantial
  14  * portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  19  * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  20  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  21  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  */
  25
  26 /*
  27  * Based on weston shared/os-compatibility.c
  28  */
  29
  30 #ifndef WIN32
  31 #include "anon_file.h"
  32
  33 #include <unistd.h>
  34 #include <fcntl.h>
  35 #include <errno.h>
  36
  37 #ifdef __FreeBSD__
  38 #include <sys/mman.h>
  39 #elif defined(HAVE_MEMFD_CREATE)
  40 #include <sys/syscall.h>
  41 #include <linux/memfd.h>
  42 #endif
  43
  44 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE) || defined(HAVE_MKOSTEMP))
  45 static int
  46 set_cloexec_or_close(int fd)
  47 {
  48    long flags;
  49
  50    if (fd == -1)
  51       return -1;
  52
  53    flags = fcntl(fd, F_GETFD);
  54    if (flags == -1)
  55       goto err;
  56
  57    if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
  58       goto err;
  59
  60    return fd;
  61
  62 err:
  63    close(fd);
  64    return -1;
  65 }
  66 #endif
  67
  68 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE))
  69 static int
  70 create_tmpfile_cloexec(char *tmpname)
  71 {
  72    int fd;
  73
  74 #ifdef HAVE_MKOSTEMP
  75    fd = mkostemp(tmpname, O_CLOEXEC);
  76 #else
  77    fd = mkstemp(tmpname);
  78 #endif
  79
  80    if (fd < 0) {
  81       return fd;
  82    }
  83
  84 #ifndef HAVE_MKOSTEMP
  85    fd = set_cloexec_or_close(fd);
  86 #endif
  87
  88    unlink(tmpname);
  89    return fd;
  90 }
  91 #endif
  92
  93 /*
  94  * Create a new, unique, anonymous file of the given size, and
  95  * return the file descriptor for it. The file descriptor is set
  96  * CLOEXEC. The file is immediately suitable for mmap()'ing
  97  * the given size at offset zero.
  98  *
  99  * An optional name for debugging can be provided as the second argument.
 100  *
 101  * The file should not have a permanent backing store like a disk,
 102  * but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
 103  *
 104  * If memfd or SHM_ANON is supported, the filesystem is not touched at all.
 105  * Otherwise, the file name is deleted from the file system.
 106  *
 107  * The file is suitable for buffer sharing between processes by
 108  * transmitting the file descriptor over Unix sockets using the
 109  * SCM_RIGHTS methods.
 110  */
 111 int
 112 os_create_anonymous_file(off_t size, char *debug_name)
 113 {
 114    int fd, ret;
 115 #ifdef __FreeBSD__
 116    (void*)debug_name;
 117    fd = shm_open(SHM_ANON, O_CREAT | O_RDWR | O_CLOEXEC, 0600);
 118 #elif defined(HAVE_MEMFD_CREATE)
 119    if (!debug_name)
 120       debug_name = "mesa-shared";
 121    fd = syscall(SYS_memfd_create, debug_name, MFD_CLOEXEC);
 122 #else
 123    const char *path;
 124    char *name;
 125
 126    path = getenv("XDG_RUNTIME_DIR");
 127    if (!path) {
 128       errno = ENOENT;
 129       return -1;
 130    }
 131
 132    if (debug_name)
 133       asprintf(&name, "%s/mesa-shared-%s-XXXXXX", path, debug_name);
 134    else
 135       asprintf(&name, "%s/mesa-shared-XXXXXX", path);
 136    if (!name)
 137       return -1;
 138
 139    fd = create_tmpfile_cloexec(name);
 140
 141    free(name);
 142 #endif
 143
 144    if (fd < 0)
 145       return -1;
 146
 147    ret = ftruncate(fd, size);
 148    if (ret < 0) {
 149       close(fd);
 150       return -1;
 151    }
 152
 153    return fd;
 154 }
 155 #endif