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 #include <stdio.h>
  37 #include <stdlib.h>
  38
  39 #ifdef __FreeBSD__
  40 #include <sys/mman.h>
  41 #elif defined(HAVE_MEMFD_CREATE)
  42 #include <sys/syscall.h>
  43 #include <linux/memfd.h>
  44 #else
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #endif
  48
  49 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE) || defined(HAVE_MKOSTEMP))
  50 static int
  51 set_cloexec_or_close(int fd)
  52 {
  53    long flags;
  54
  55    if (fd == -1)
  56       return -1;
  57
  58    flags = fcntl(fd, F_GETFD);
  59    if (flags == -1)
  60       goto err;
  61
  62    if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
  63       goto err;
  64
  65    return fd;
  66
  67 err:
  68    close(fd);
  69    return -1;
  70 }
  71 #endif
  72
  73 #if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE))
  74 static int
  75 create_tmpfile_cloexec(char *tmpname)
  76 {
  77    int fd;
  78
  79 #ifdef HAVE_MKOSTEMP
  80    fd = mkostemp(tmpname, O_CLOEXEC);
  81 #else
  82    fd = mkstemp(tmpname);
  83 #endif
  84
  85    if (fd < 0) {
  86       return fd;
  87    }
  88
  89 #ifndef HAVE_MKOSTEMP
  90    fd = set_cloexec_or_close(fd);
  91 #endif
  92
  93    unlink(tmpname);
  94    return fd;
  95 }
  96 #endif
  97
  98 /*
  99  * Create a new, unique, anonymous file of the given size, and
 100  * return the file descriptor for it. The file descriptor is set
 101  * CLOEXEC. The file is immediately suitable for mmap()'ing
 102  * the given size at offset zero.
 103  *
 104  * An optional name for debugging can be provided as the second argument.
 105  *
 106  * The file should not have a permanent backing store like a disk,
 107  * but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
 108  *
 109  * If memfd or SHM_ANON is supported, the filesystem is not touched at all.
 110  * Otherwise, the file name is deleted from the file system.
 111  *
 112  * The file is suitable for buffer sharing between processes by
 113  * transmitting the file descriptor over Unix sockets using the
 114  * SCM_RIGHTS methods.
 115  */
 116 int
 117 os_create_anonymous_file(off_t size, const char *debug_name)
 118 {
 119    int fd, ret;
 120 #ifdef __FreeBSD__
 121    (void*)debug_name;
 122    fd = shm_open(SHM_ANON, O_CREAT | O_RDWR | O_CLOEXEC, 0600);
 123 #elif defined(HAVE_MEMFD_CREATE)
 124    if (!debug_name)
 125       debug_name = "mesa-shared";
 126    fd = syscall(SYS_memfd_create, debug_name, MFD_CLOEXEC);
 127 #else
 128    const char *path;
 129    char *name;
 130
 131    path = getenv("XDG_RUNTIME_DIR");
 132    if (!path) {
 133       errno = ENOENT;
 134       return -1;
 135    }
 136
 137    if (debug_name)
 138       asprintf(&name, "%s/mesa-shared-%s-XXXXXX", path, debug_name);
 139    else
 140       asprintf(&name, "%s/mesa-shared-XXXXXX", path);
 141    if (!name)
 142       return -1;
 143
 144    fd = create_tmpfile_cloexec(name);
 145
 146    free(name);
 147 #endif
 148
 149    if (fd < 0)
 150       return -1;
 151
 152    ret = ftruncate(fd, size);
 153    if (ret < 0) {
 154       close(fd);
 155       return -1;
 156    }
 157
 158    return fd;
 159 }
 160 #endif