1 files changed, 404 insertions, 0 deletions
diff --git a/shared/os-compatibility.c b/shared/os-compatibility.c
new file mode 100644
index 0000000..3638887
--- /dev/null
+++ b/shared/os-compatibility.c
@@ -0,0 +1,404 @@
+/* SPDX-License-Identifier: MIT
+ * 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 <sys/types.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/epoll.h>
+#include <string.h>
+#include <stdlib.h>
+
+#ifdef HAVE_MEMFD_CREATE
+#include <sys/mman.h>
+#endif
+
+#include "os-compatibility.h"
+
+#define READONLY_SEALS (F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE)
+
+int
+os_fd_set_cloexec(int fd)
+{
+	long flags;
+
+	if (fd == -1)
+		return -1;
+
+	flags = fcntl(fd, F_GETFD);
+	if (flags == -1)
+		return -1;
+
+	if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
+		return -1;
+
+	return 0;
+}
+
+static int
+set_cloexec_or_close(int fd)
+{
+	if (os_fd_set_cloexec(fd) != 0) {
+		close(fd);
+		return -1;
+	}
+	return fd;
+}
+
+int
+os_socketpair_cloexec(int domain, int type, int protocol, int *sv)
+{
+	int ret;
+
+#ifdef SOCK_CLOEXEC
+	ret = socketpair(domain, type | SOCK_CLOEXEC, protocol, sv);
+	if (ret == 0 || errno != EINVAL)
+		return ret;
+#endif
+
+	ret = socketpair(domain, type, protocol, sv);
+	if (ret < 0)
+		return ret;
+
+	sv[0] = set_cloexec_or_close(sv[0]);
+	sv[1] = set_cloexec_or_close(sv[1]);
+
+	if (sv[0] != -1 && sv[1] != -1)
+		return 0;
+
+	close(sv[0]);
+	close(sv[1]);
+	return -1;
+}
+
+int
+os_epoll_create_cloexec(void)
+{
+	int fd;
+
+#ifdef EPOLL_CLOEXEC
+	fd = epoll_create1(EPOLL_CLOEXEC);
+	if (fd >= 0)
+		return fd;
+	if (errno != EINVAL)
+		return -1;
+#endif
+
+	fd = epoll_create(1);
+	return set_cloexec_or_close(fd);
+}
+
+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[] = "/weston-shared-XXXXXX";
+	const char *path;
+	char *name;
+	int fd;
+	int ret;
+
+#ifdef HAVE_MEMFD_CREATE
+	fd = memfd_create("weston-shared", 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);
+	} 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
+	do {
+		ret = posix_fallocate(fd, 0, size);
+	} while (ret == EINTR);
+	if (ret != 0) {
+		close(fd);
+		errno = ret;
+		return -1;
+	}
+#else
+	do {
+		ret = ftruncate(fd, size);
+	} while (ret < 0 && errno == EINTR);
+	if (ret < 0) {
+		close(fd);
+		return -1;
+	}
+#endif
+
+	return fd;
+}
+
+#ifndef HAVE_STRCHRNUL
+char *
+strchrnul(const char *s, int c)
+{
+	while (*s && *s != c)
+		s++;
+	return (char *)s;
+}
+#endif
+
+struct ro_anonymous_file {
+	int fd;
+	size_t size;
+};
+
+/** Create a new anonymous read-only file of the given size and the given data
+ *
+ * \param size The size of \p data.
+ * \param data The data of the file with the size \p size.
+ * \return A new \c ro_anonymous_file, or NULL on failure.
+ *
+ * The intended use-case is for sending mid-sized data from the compositor
+ * to clients.
+ * If the function fails errno is set.
+ */
+struct ro_anonymous_file *
+os_ro_anonymous_file_create(size_t size,
+			    const char *data)
+{
+	struct ro_anonymous_file *file;
+	void *map;
+
+	file = calloc(1, sizeof *file);
+	if (!file) {
+		errno = ENOMEM;
+		return NULL;
+	}
+
+	file->size = size;
+	file->fd = os_create_anonymous_file(size);
+	if (file->fd == -1)
+		goto err_free;
+
+	map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, file->fd, 0);
+	if (map == MAP_FAILED)
+		goto err_close;
+
+	memcpy(map, data, size);
+
+	munmap(map, size);
+
+#ifdef HAVE_MEMFD_CREATE
+	/* try to put seals on the file to make it read-only so that we can
+	 * return the fd later directly when support_shared is not set.
+	 * os_ro_anonymous_file_get_fd can handle the fd even if it is not
+	 * sealed read-only and will instead create a new anonymous file on
+	 * each invocation.
+	 */
+	fcntl(file->fd, F_ADD_SEALS, READONLY_SEALS);
+#endif
+
+	return file;
+
+err_close:
+	close(file->fd);
+err_free:
+	free(file);
+	return NULL;
+}
+
+/** Destroy an anonymous read-only file
+ *
+ * \param file The file to destroy.
+ */
+void
+os_ro_anonymous_file_destroy(struct ro_anonymous_file *file)
+{
+	close(file->fd);
+	free(file);
+}
+
+/** Get the size of an anonymous read-only file
+ *
+ * \param file The file to get the size of.
+ * \return The size of the file.
+ */
+size_t
+os_ro_anonymous_file_size(struct ro_anonymous_file *file)
+{
+	return file->size;
+}
+
+/** Returns a file descriptor for the given file, ready to be send to a client.
+ *
+ * \param file The file for which to get a file descriptor.
+ * \param mapmode Describes the ways in which the returned file descriptor can
+ * be used with mmap.
+ * \return A file descriptor for the given file that can be send to a client
+ * or -1 on failure.
+ *
+ * The returned file descriptor must not be shared between multiple clients.
+ * When \p mapmode is RO_ANONYMOUS_FILE_MAPMODE_PRIVATE the file descriptor is
+ * only guaranteed to be mmapable with \c MAP_PRIVATE, when \p mapmode is
+ * RO_ANONYMOUS_FILE_MAPMODE_SHARED the file descriptor can be mmaped with
+ * either MAP_PRIVATE or MAP_SHARED.
+ * When you're done with the fd you must call \c os_ro_anonymous_file_put_fd
+ * instead of calling \c close.
+ * If the function fails errno is set.
+ */
+int
+os_ro_anonymous_file_get_fd(struct ro_anonymous_file *file,
+			    enum ro_anonymous_file_mapmode mapmode)
+{
+	void *src, *dst;
+	int seals, fd;
+
+	seals = fcntl(file->fd, F_GET_SEALS);
+
+	/* file was sealed for read-only and we don't have to support MAP_SHARED
+	 * so we can simply pass the memfd fd
+	 */
+	if (seals != -1 && mapmode == RO_ANONYMOUS_FILE_MAPMODE_PRIVATE &&
+	    (seals & READONLY_SEALS) == READONLY_SEALS)
+		return file->fd;
+
+	/* for all other cases we create a new anonymous file that can be mapped
+	 * with MAP_SHARED and copy the contents to it and return that instead
+	 */
+	fd = os_create_anonymous_file(file->size);
+	if (fd == -1)
+		return fd;
+
+	src = mmap(NULL, file->size, PROT_READ, MAP_PRIVATE, file->fd, 0);
+	if (src == MAP_FAILED) {
+		close(fd);
+		return -1;
+	}
+
+	dst = mmap(NULL, file->size, PROT_WRITE, MAP_SHARED, fd, 0);
+	if (dst == MAP_FAILED) {
+		close(fd);
+		munmap(src, file->size);
+		return -1;
+	}
+
+	memcpy(dst, src, file->size);
+	munmap(src, file->size);
+	munmap(dst, file->size);
+
+	return fd;
+}
+
+/** Release a file descriptor returned by \c os_ro_anonymous_file_get_fd
+ *
+ * \param fd A file descriptor returned by \c os_ro_anonymous_file_get_fd.
+ * \return 0 on success, or -1 on failure.
+ *
+ * This function must be called for every file descriptor created with
+ * \c os_ro_anonymous_file_get_fd to not leake any resources.
+ * If the function fails errno is set.
+ */
+int
+os_ro_anonymous_file_put_fd(int fd)
+{
+	int seals = fcntl(fd, F_GET_SEALS);
+	if (seals == -1 && errno != EINVAL)
+		return -1;
+
+	/* If the fd cannot be sealed seals is -1 at this point
+	 * or the file can be sealed but has not been sealed for writing.
+	 * In both cases we created a new anonymous file that we have to
+	 * close.
+	 */
+	if (seals == -1 || !(seals & F_SEAL_WRITE))
+		close(fd);
+
+	return 0;
+}