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 #else
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #endif
  46
  47 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE) || defined(HAVE_MKOSTEMP))
  48 static int
  49 set_cloexec_or_close(int fd)
  50 {
  51    long flags;
  52
  53    if (fd == -1)
  54       return -1;
  55
  56    flags = fcntl(fd, F_GETFD);
  57    if (flags == -1)
  58       goto err;
  59
  60    if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
  61       goto err;
  62
  63    return fd;
  64
  65 err:
  66    close(fd);
  67    return -1;
  68 }
  69 #endif
  70
  71 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE))
  72 static int
  73 create_tmpfile_cloexec(char *tmpname)
  74 {
  75    int fd;
  76
  77 #ifdef HAVE_MKOSTEMP
  78    fd = mkostemp(tmpname, O_CLOEXEC);
  79 #else
  80    fd = mkstemp(tmpname);
  81 #endif
  82
  83    if (fd < 0) {
  84       return fd;
  85    }
  86
  87 #ifndef HAVE_MKOSTEMP
  88    fd = set_cloexec_or_close(fd);
  89 #endif
  90
  91    unlink(tmpname);
  92    return fd;
  93 }
  94 #endif
  95
  96 /*
  97  * Create a new, unique, anonymous file of the given size, and
  98  * return the file descriptor for it. The file descriptor is set
  99  * CLOEXEC. The file is immediately suitable for mmap()'ing
 100  * the given size at offset zero.
 101  *
 102  * An optional name for debugging can be provided as the second argument.
 103  *
 104  * The file should not have a permanent backing store like a disk,
 105  * but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
 106  *
 107  * If memfd or SHM_ANON is supported, the filesystem is not touched at all.
 108  * Otherwise, the file name is deleted from the file system.
 109  *
 110  * The file is suitable for buffer sharing between processes by
 111  * transmitting the file descriptor over Unix sockets using the
 112  * SCM_RIGHTS methods.
 113  */
 114 int
 115 os_create_anonymous_file(off_t size, const char *debug_name)
 116 {
 117    int fd, ret;
 118 #ifdef __FreeBSD__
 119    (void*)debug_name;
 120    fd = shm_open(SHM_ANON, O_CREAT | O_RDWR | O_CLOEXEC, 0600);
 121 #elif defined(HAVE_MEMFD_CREATE)
 122    if (!debug_name)
 123       debug_name = "mesa-shared";
 124    fd = syscall(SYS_memfd_create, debug_name, MFD_CLOEXEC);
 125 #else
 126    const char *path;
 127    char *name;
 128
 129    path = getenv("XDG_RUNTIME_DIR");
 130    if (!path) {
 131       errno = ENOENT;
 132       return -1;
 133    }
 134
 135    if (debug_name)
 136       asprintf(&name, "%s/mesa-shared-%s-XXXXXX", path, debug_name);
 137    else
 138       asprintf(&name, "%s/mesa-shared-XXXXXX", path);
 139    if (!name)
 140       return -1;
 141
 142    fd = create_tmpfile_cloexec(name);
 143
 144    free(name);
 145 #endif
 146
 147    if (fd < 0)
 148       return -1;
 149
 150    ret = ftruncate(fd, size);
 151    if (ret < 0) {
 152       close(fd);
 153       return -1;
 154    }
 155
 156    return fd;
 157 }
 158 #endif