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