diff options
Diffstat (limited to 'gdk/wayland/cursor/os-compatibility.c')
-rw-r--r-- | gdk/wayland/cursor/os-compatibility.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/gdk/wayland/cursor/os-compatibility.c b/gdk/wayland/cursor/os-compatibility.c new file mode 100644 index 0000000000..3818a6170e --- /dev/null +++ b/gdk/wayland/cursor/os-compatibility.c @@ -0,0 +1,172 @@ +/* + * Copyright © 2012 Collabora, Ltd. + * + * Permission is hereby granted, free of charge, to any person obtaining + * a copy of this software and associated documentation files (the + * "Software"), to deal in the Software without restriction, including + * without limitation the rights to use, copy, modify, merge, publish, + * distribute, sublicense, and/or sell copies of the Software, and to + * permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice (including the + * next paragraph) shall be included in all copies or substantial + * portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#include "config.h" + +#include <sys/types.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#include <string.h> +#include <stdlib.h> + +#ifdef HAVE_MEMFD_CREATE +#include <sys/mman.h> +#endif + +#include "os-compatibility.h" + +#ifndef HAVE_MKOSTEMP +static int +set_cloexec_or_close(int fd) +{ + long flags; + + if (fd == -1) + return -1; + + flags = fcntl(fd, F_GETFD); + if (flags == -1) + goto err; + + if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) + goto err; + + return fd; + +err: + close(fd); + return -1; +} +#endif + +static int +create_tmpfile_cloexec(char *tmpname) +{ + int fd; + +#ifdef HAVE_MKOSTEMP + fd = mkostemp(tmpname, O_CLOEXEC); + if (fd >= 0) + unlink(tmpname); +#else + fd = mkstemp(tmpname); + if (fd >= 0) { + fd = set_cloexec_or_close(fd); + unlink(tmpname); + } +#endif + + return fd; +} + +/* + * Create a new, unique, anonymous file of the given size, and + * return the file descriptor for it. The file descriptor is set + * CLOEXEC. The file is immediately suitable for mmap()'ing + * the given size at offset zero. + * + * The file should not have a permanent backing store like a disk, + * but may have if XDG_RUNTIME_DIR is not properly implemented in OS. + * + * The file name is deleted from the file system. + * + * The file is suitable for buffer sharing between processes by + * transmitting the file descriptor over Unix sockets using the + * SCM_RIGHTS methods. + * + * If the C library implements posix_fallocate(), it is used to + * guarantee that disk space is available for the file at the + * given size. If disk space is insufficient, errno is set to ENOSPC. + * If posix_fallocate() is not supported, program may receive + * SIGBUS on accessing mmap()'ed file contents instead. + * + * If the C library implements memfd_create(), it is used to create the + * file purely in memory, without any backing file name on the file + * system, and then sealing off the possibility of shrinking it. This + * can then be checked before accessing mmap()'ed file contents, to + * make sure SIGBUS can't happen. It also avoids requiring + * XDG_RUNTIME_DIR. + */ +int +os_create_anonymous_file(off_t size) +{ + static const char template[] = "/wayland-cursor-shared-XXXXXX"; + const char *path; + char *name; + int fd; + int ret; + +#ifdef HAVE_MEMFD_CREATE + fd = memfd_create("wayland-cursor", MFD_CLOEXEC | MFD_ALLOW_SEALING); + if (fd >= 0) { + /* We can add this seal before calling posix_fallocate(), as + * the file is currently zero-sized anyway. + * + * There is also no need to check for the return value, we + * couldn't do anything with it anyway. + */ + fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_SEAL); + } else +#endif + { + path = getenv("XDG_RUNTIME_DIR"); + if (!path) { + errno = ENOENT; + return -1; + } + + name = malloc(strlen(path) + sizeof(template)); + if (!name) + return -1; + + strcpy(name, path); + strcat(name, template); + + fd = create_tmpfile_cloexec(name); + + free(name); + + if (fd < 0) + return -1; + } + +#ifdef HAVE_POSIX_FALLOCATE + ret = posix_fallocate(fd, 0, size); + if (ret != 0) { + close(fd); + errno = ret; + return -1; + } +#else + ret = ftruncate(fd, size); + if (ret < 0) { + close(fd); + return -1; + } +#endif + + return fd; +} |