| /* fchdir replacement. |
| Copyright (C) 2006-2021 Free Software Foundation, Inc. |
| |
| This program is free software: you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
| |
| #include <config.h> |
| |
| /* Specification. */ |
| #include <unistd.h> |
| |
| #include <dirent.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <stdbool.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| |
| #include "assure.h" |
| #include "filename.h" |
| #include "filenamecat.h" |
| |
| #ifndef REPLACE_OPEN_DIRECTORY |
| # define REPLACE_OPEN_DIRECTORY 0 |
| #endif |
| |
| /* This replacement assumes that a directory is not renamed while opened |
| through a file descriptor. |
| |
| FIXME: On mingw, this would be possible to enforce if we were to |
| also open a HANDLE to each directory currently visited by a file |
| descriptor, since mingw refuses to rename any in-use file system |
| object. */ |
| |
| /* Array of file descriptors opened. If REPLACE_OPEN_DIRECTORY or if it points |
| to a directory, it stores info about this directory. */ |
| typedef struct |
| { |
| char *name; /* Absolute name of the directory, or NULL. */ |
| /* FIXME - add a DIR* member to make dirfd possible on mingw? */ |
| } dir_info_t; |
| static dir_info_t *dirs; |
| static size_t dirs_allocated; |
| |
| /* Try to ensure dirs has enough room for a slot at index fd; free any |
| contents already in that slot. Return false and set errno to |
| ENOMEM on allocation failure. */ |
| static bool |
| ensure_dirs_slot (size_t fd) |
| { |
| if (fd < dirs_allocated) |
| free (dirs[fd].name); |
| else |
| { |
| size_t new_allocated; |
| dir_info_t *new_dirs; |
| |
| new_allocated = 2 * dirs_allocated + 1; |
| if (new_allocated <= fd) |
| new_allocated = fd + 1; |
| new_dirs = |
| (dirs != NULL |
| ? (dir_info_t *) realloc (dirs, new_allocated * sizeof *dirs) |
| : (dir_info_t *) malloc (new_allocated * sizeof *dirs)); |
| if (new_dirs == NULL) |
| return false; |
| memset (new_dirs + dirs_allocated, 0, |
| (new_allocated - dirs_allocated) * sizeof *dirs); |
| dirs = new_dirs; |
| dirs_allocated = new_allocated; |
| } |
| return true; |
| } |
| |
| /* Return an absolute name of DIR in malloc'd storage. |
| Upon failure, return NULL with errno set. */ |
| static char * |
| get_name (char const *dir) |
| { |
| char *cwd; |
| char *result; |
| int saved_errno; |
| |
| if (IS_ABSOLUTE_FILE_NAME (dir)) |
| return strdup (dir); |
| |
| /* We often encounter "."; treat it as a special case. */ |
| cwd = getcwd (NULL, 0); |
| if (!cwd || (dir[0] == '.' && dir[1] == '\0')) |
| return cwd; |
| |
| result = mfile_name_concat (cwd, dir, NULL); |
| saved_errno = errno; |
| free (cwd); |
| errno = saved_errno; |
| return result; |
| } |
| |
| /* Hook into the gnulib replacements for open() and close() to keep track |
| of the open file descriptors. */ |
| |
| /* Close FD, cleaning up any fd to name mapping if fd was visiting a |
| directory. */ |
| void |
| _gl_unregister_fd (int fd) |
| { |
| if (fd >= 0 && fd < dirs_allocated) |
| { |
| free (dirs[fd].name); |
| dirs[fd].name = NULL; |
| } |
| } |
| |
| /* Mark FD as visiting FILENAME. FD must be non-negative, and refer |
| to an open file descriptor. If REPLACE_OPEN_DIRECTORY is non-zero, |
| this should only be called if FD is visiting a directory. Close FD |
| and return -1 with errno set if there is insufficient memory to track |
| the directory name; otherwise return FD. */ |
| int |
| _gl_register_fd (int fd, const char *filename) |
| { |
| struct stat statbuf; |
| |
| assure (0 <= fd); |
| if (REPLACE_OPEN_DIRECTORY |
| || (fstat (fd, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))) |
| { |
| if (!ensure_dirs_slot (fd) |
| || (dirs[fd].name = get_name (filename)) == NULL) |
| { |
| int saved_errno = errno; |
| close (fd); |
| errno = saved_errno; |
| return -1; |
| } |
| } |
| return fd; |
| } |
| |
| /* Mark NEWFD as a duplicate of OLDFD; useful from dup, dup2, dup3, |
| and fcntl. Both arguments must be valid and distinct file |
| descriptors. Close NEWFD and return -1 if OLDFD is tracking a |
| directory, but there is insufficient memory to track the same |
| directory in NEWFD; otherwise return NEWFD. */ |
| int |
| _gl_register_dup (int oldfd, int newfd) |
| { |
| assure (0 <= oldfd && 0 <= newfd && oldfd != newfd); |
| if (oldfd < dirs_allocated && dirs[oldfd].name) |
| { |
| /* Duplicated a directory; must ensure newfd is allocated. */ |
| if (!ensure_dirs_slot (newfd) |
| || (dirs[newfd].name = strdup (dirs[oldfd].name)) == NULL) |
| { |
| int saved_errno = errno; |
| close (newfd); |
| errno = saved_errno; |
| newfd = -1; |
| } |
| } |
| else if (newfd < dirs_allocated) |
| { |
| /* Duplicated a non-directory; ensure newfd is cleared. */ |
| free (dirs[newfd].name); |
| dirs[newfd].name = NULL; |
| } |
| return newfd; |
| } |
| |
| /* If FD is currently visiting a directory, then return the name of |
| that directory. Otherwise, return NULL and set errno. */ |
| const char * |
| _gl_directory_name (int fd) |
| { |
| if (0 <= fd && fd < dirs_allocated && dirs[fd].name != NULL) |
| return dirs[fd].name; |
| /* At this point, fd is either invalid, or open but not a directory. |
| If dup2 fails, errno is correctly EBADF. */ |
| if (0 <= fd) |
| { |
| if (dup2 (fd, fd) == fd) |
| errno = ENOTDIR; |
| } |
| else |
| errno = EBADF; |
| return NULL; |
| } |
| |
| |
| /* Implement fchdir() in terms of chdir(). */ |
| |
| int |
| fchdir (int fd) |
| { |
| const char *name = _gl_directory_name (fd); |
| return name ? chdir (name) : -1; |
| } |