/*
   * 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 <sys/socket.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <errno.h>
  #include <sys/epoll.h>
  #include <string.h>
  #include <stdlib.h>
  #include <libweston/zalloc.h>
  #include <sys/mman.h>
  
  #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 = zalloc(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   fd;
  
  #ifdef HAVE_MEMFD_CREATE
  	int 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;
  	}
  #endif
  
  	/* 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)
  {
  #ifdef HAVE_MEMFD_CREATE
  	int seals = fcntl(fd, F_GET_SEALS);
  	if ((seals == -1) && (errno != EINVAL))
  	{
  		return -1;
  	}
  
  	/* The only case in which we do NOT have to close the file is when the file
  	 * was sealed for read-only
  	 */
  	if ((seals != -1) && ((seals & READONLY_SEALS) == READONLY_SEALS))
  	{
  		return 0;
  	}
  #endif
  
  	close(fd);
  	return 0;
  }