| /* Save and restore the working directory, possibly using a child process. | |
| Copyright (C) 2006-2007, 2009-2026 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/>. */ | |
| /* Written by Paul Eggert. */ | |
| #define SAVEWD_INLINE _GL_EXTERN_INLINE | |
| #include <config.h> | |
| #include "savewd.h" | |
| #include <errno.h> | |
| #include <fcntl.h> | |
| #include <signal.h> | |
| #include <stdlib.h> | |
| #include <sys/types.h> | |
| #include <sys/wait.h> | |
| #include <unistd.h> | |
| #include "assure.h" | |
| #include "attribute.h" | |
| #include "filename.h" | |
| #if GNULIB_FCNTL_SAFER | |
| # include "fcntl--.h" | |
| #endif | |
| #if defined _WIN32 && !defined __CYGWIN__ | |
| # define fork() (assure (false), -1) | |
| #endif | |
| /* Save the working directory into *WD, if it hasn't been saved | |
| already. Return true if a child has been forked to do the real | |
| work. */ | |
| static bool | |
| savewd_save (struct savewd *wd) | |
| { | |
| switch (wd->state) | |
| { | |
| case INITIAL_STATE: | |
| /* Save the working directory, or prepare to fall back if possible. */ | |
| { | |
| int fd = open (".", O_SEARCH); | |
| if (0 <= fd) | |
| { | |
| wd->state = FD_STATE; | |
| wd->val.fd = fd; | |
| break; | |
| } | |
| /* There is no point to forking on native MS-Windows which lacks 'fork'. | |
| Although there is also no point on systems that support O_SEARCH, | |
| macOS 12.6 APFS open (".", O_SEARCH) incorrectly fails if "." is | |
| mode 311, so do not attempt to optimize for O_SEARCH != O_RDONLY. */ | |
| # if defined _WIN32 && !defined __CYGWIN__ | |
| bool try_fork = false; | |
| # else | |
| bool try_fork = errno == EACCES || errno == ESTALE; | |
| # endif | |
| if (!try_fork) | |
| { | |
| wd->state = ERROR_STATE; | |
| wd->val.errnum = errno; | |
| break; | |
| } | |
| } | |
| wd->state = FORKING_STATE; | |
| wd->val.child = -1; | |
| FALLTHROUGH; | |
| case FORKING_STATE: | |
| if (wd->val.child < 0) | |
| { | |
| /* "Save" the initial working directory by forking a new | |
| subprocess that will attempt all the work from the chdir | |
| until the next savewd_restore. */ | |
| wd->val.child = fork (); | |
| if (wd->val.child != 0) | |
| { | |
| if (0 < wd->val.child) | |
| return true; | |
| wd->state = ERROR_STATE; | |
| wd->val.errnum = errno; | |
| } | |
| } | |
| break; | |
| case FD_STATE: | |
| case FD_POST_CHDIR_STATE: | |
| case ERROR_STATE: | |
| case FINAL_STATE: | |
| break; | |
| default: | |
| assure (false); | |
| } | |
| return false; | |
| } | |
| int | |
| savewd_chdir (struct savewd *wd, char const *dir, int options, | |
| int open_result[2]) | |
| { | |
| int fd = -1; | |
| int result = 0; | |
| /* Open the directory if requested, or if avoiding a race condition | |
| is requested and possible. */ | |
| if (open_result | |
| || (options & (HAVE_WORKING_O_NOFOLLOW ? SAVEWD_CHDIR_NOFOLLOW : 0))) | |
| { | |
| fd = open (dir, | |
| (O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK | |
| | (options & SAVEWD_CHDIR_NOFOLLOW ? O_NOFOLLOW : 0))); | |
| if (open_result) | |
| { | |
| open_result[0] = fd; | |
| open_result[1] = errno; | |
| } | |
| if (fd < 0 && errno != EACCES) | |
| result = -1; | |
| } | |
| if (result == 0 && ! (0 <= fd && options & SAVEWD_CHDIR_SKIP_READABLE)) | |
| { | |
| if (savewd_save (wd)) | |
| { | |
| open_result = NULL; | |
| result = -2; | |
| } | |
| else | |
| { | |
| result = (fd < 0 ? chdir (dir) : fchdir (fd)); | |
| if (result == 0) | |
| switch (wd->state) | |
| { | |
| case FD_STATE: | |
| wd->state = FD_POST_CHDIR_STATE; | |
| break; | |
| case ERROR_STATE: | |
| case FD_POST_CHDIR_STATE: | |
| case FINAL_STATE: | |
| break; | |
| case FORKING_STATE: | |
| assure (wd->val.child == 0); | |
| break; | |
| case INITIAL_STATE: default: | |
| assure (false); | |
| } | |
| } | |
| } | |
| if (0 <= fd && ! open_result) | |
| { | |
| int saved_errno = errno; | |
| close (fd); | |
| errno = saved_errno; | |
| } | |
| return result; | |
| } | |
| int | |
| savewd_restore (struct savewd *wd, int status) | |
| { | |
| switch (wd->state) | |
| { | |
| case INITIAL_STATE: | |
| case FD_STATE: | |
| /* The working directory is the desired directory, so there's no | |
| work to do. */ | |
| break; | |
| case FD_POST_CHDIR_STATE: | |
| /* Restore the working directory using fchdir. */ | |
| if (fchdir (wd->val.fd) == 0) | |
| { | |
| wd->state = FD_STATE; | |
| break; | |
| } | |
| else | |
| { | |
| int chdir_errno = errno; | |
| close (wd->val.fd); | |
| wd->state = ERROR_STATE; | |
| wd->val.errnum = chdir_errno; | |
| } | |
| FALLTHROUGH; | |
| case ERROR_STATE: | |
| /* Report an error if asked to restore the working directory. */ | |
| errno = wd->val.errnum; | |
| return -1; | |
| case FORKING_STATE: | |
| /* "Restore" the working directory by waiting for the subprocess | |
| to finish. */ | |
| { | |
| pid_t child = wd->val.child; | |
| if (child == 0) | |
| _exit (status); | |
| if (0 < child) | |
| { | |
| int child_status; | |
| while (waitpid (child, &child_status, 0) < 0) | |
| assure (errno == EINTR); | |
| wd->val.child = -1; | |
| if (! WIFEXITED (child_status)) | |
| raise (WTERMSIG (child_status)); | |
| return WEXITSTATUS (child_status); | |
| } | |
| } | |
| break; | |
| case FINAL_STATE: default: | |
| assure (false); | |
| } | |
| return 0; | |
| } | |
| void | |
| savewd_finish (struct savewd *wd) | |
| { | |
| switch (wd->state) | |
| { | |
| case ERROR_STATE: | |
| break; | |
| case FD_STATE: | |
| case FD_POST_CHDIR_STATE: | |
| close (wd->val.fd); | |
| FALLTHROUGH; | |
| case INITIAL_STATE: | |
| wd->val.errnum = 0; | |
| break; | |
| case FORKING_STATE: | |
| assure (wd->val.child < 0); | |
| wd->val.errnum = 0; | |
| break; | |
| case FINAL_STATE: default: | |
| assure (false); | |
| } | |
| wd->state = FINAL_STATE; | |
| } | |
| /* Return true if the actual work is currently being done by a | |
| subprocess. | |
| A true return means that the caller and the subprocess should | |
| resynchronize later with savewd_restore, using only their own | |
| memory to decide when to resynchronize; they should not consult the | |
| file system to decide, because that might lead to race conditions. | |
| This is why savewd_chdir is broken out into another function; | |
| savewd_chdir's callers _can_ inspect the file system to decide | |
| whether to call savewd_chdir. */ | |
| static bool | |
| savewd_delegating (struct savewd const *wd) | |
| { | |
| return wd->state == FORKING_STATE && 0 < wd->val.child; | |
| } | |
| int | |
| savewd_process_files (int n_files, char **file, | |
| int (*act) (char *, struct savewd *, void *), | |
| void *options) | |
| { | |
| int i = 0; | |
| int last_relative; | |
| int exit_status = EXIT_SUCCESS; | |
| struct savewd wd; | |
| savewd_init (&wd); | |
| for (last_relative = n_files - 1; 0 <= last_relative; last_relative--) | |
| if (! IS_ABSOLUTE_FILE_NAME (file[last_relative])) | |
| break; | |
| for (; i < last_relative; i++) | |
| { | |
| if (! savewd_delegating (&wd)) | |
| { | |
| int s = act (file[i], &wd, options); | |
| if (exit_status < s) | |
| exit_status = s; | |
| } | |
| if (! IS_ABSOLUTE_FILE_NAME (file[i + 1])) | |
| { | |
| int r = savewd_restore (&wd, exit_status); | |
| if (exit_status < r) | |
| exit_status = r; | |
| } | |
| } | |
| savewd_finish (&wd); | |
| for (; i < n_files; i++) | |
| { | |
| int s = act (file[i], &wd, options); | |
| if (exit_status < s) | |
| exit_status = s; | |
| } | |
| return exit_status; | |
| } |