diff options
Diffstat (limited to 'lib/fchdir.c')
| -rw-r--r-- | lib/fchdir.c | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/lib/fchdir.c b/lib/fchdir.c new file mode 100644 index 0000000..e3ec2fc --- /dev/null +++ b/lib/fchdir.c @@ -0,0 +1,279 @@ +/* fchdir replacement. + Copyright (C) 2006, 2007 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 2, 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, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#include <config.h> + +/* Specification. */ +#include <unistd.h> + +#include <errno.h> +#include <fcntl.h> +#include <stdarg.h> +#include <stdlib.h> +#include <string.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <dirent.h> + +#include "canonicalize.h" +#include "dirfd.h" + +/* This replacement assumes that a directory is not renamed while opened + through a file descriptor. */ + +/* Array of file descriptors opened. If it points to a directory, it stores + info about this directory; otherwise it stores an errno value of ENOTDIR. */ +typedef struct +{ + char *name; /* Absolute name of the directory, or NULL. */ + int saved_errno; /* If name == NULL: The error code describing the failure + reason. */ +} 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. */ +static void +ensure_dirs_slot (size_t fd) +{ + if (fd >= dirs_allocated) + { + size_t new_allocated; + dir_info_t *new_dirs; + size_t i; + + 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 (dir_info_t)) + : (dir_info_t *) malloc (new_allocated * sizeof (dir_info_t))); + if (new_dirs != NULL) + { + for (i = dirs_allocated; i < new_allocated; i++) + { + new_dirs[i].name = NULL; + new_dirs[i].saved_errno = ENOTDIR; + } + dirs = new_dirs; + dirs_allocated = new_allocated; + } + } +} + +/* Override open() and close(), to keep track of the open file descriptors. */ + +int +close (int fd) +#undef close +{ + int retval = close (fd); + + if (retval >= 0 && fd >= 0 && fd < dirs_allocated) + { + if (dirs[fd].name != NULL) + free (dirs[fd].name); + dirs[fd].name = NULL; + dirs[fd].saved_errno = ENOTDIR; + } + return retval; +} + +int +open (const char *filename, int flags, ...) +#undef open +{ + mode_t mode; + int fd; + struct stat statbuf; + + mode = 0; + if (flags & O_CREAT) + { + va_list arg; + va_start (arg, flags); + + /* If mode_t is narrower than int, use the promoted type (int), + not mode_t. Use sizeof to guess whether mode_t is narrower; + we don't know of any practical counterexamples. */ + mode = (sizeof (mode_t) < sizeof (int) + ? va_arg (arg, int) + : va_arg (arg, mode_t)); + + va_end (arg); + } + fd = open (filename, flags, mode); + if (fd >= 0) + { + ensure_dirs_slot (fd); + if (fd < dirs_allocated + && fstat (fd, &statbuf) >= 0 && S_ISDIR (statbuf.st_mode)) + { + dirs[fd].name = canonicalize_file_name (filename); + if (dirs[fd].name == NULL) + dirs[fd].saved_errno = errno; + } + } + return fd; +} + +/* Override opendir() and closedir(), to keep track of the open file + descriptors. Needed because there is a function dirfd(). */ + +int +closedir (DIR *dp) +#undef closedir +{ + int fd = dirfd (dp); + int retval = closedir (dp); + + if (retval >= 0 && fd >= 0 && fd < dirs_allocated) + { + if (dirs[fd].name != NULL) + free (dirs[fd].name); + dirs[fd].name = NULL; + dirs[fd].saved_errno = ENOTDIR; + } + return retval; +} + +DIR * +opendir (const char *filename) +#undef opendir +{ + DIR *dp; + + dp = opendir (filename); + if (dp != NULL) + { + int fd = dirfd (dp); + if (fd >= 0) + { + ensure_dirs_slot (fd); + if (fd < dirs_allocated) + { + dirs[fd].name = canonicalize_file_name (filename); + if (dirs[fd].name == NULL) + dirs[fd].saved_errno = errno; + } + } + } + return dp; +} + +/* Override dup() and dup2(), to keep track of open file descriptors. */ + +int +dup (int oldfd) +#undef dup +{ + int newfd = dup (oldfd); + + if (oldfd >= 0 && newfd >= 0) + { + ensure_dirs_slot (newfd); + if (newfd < dirs_allocated) + { + if (oldfd < dirs_allocated) + { + if (dirs[oldfd].name != NULL) + { + dirs[newfd].name = strdup (dirs[oldfd].name); + if (dirs[newfd].name == NULL) + dirs[newfd].saved_errno = ENOMEM; + } + else + { + dirs[newfd].name = NULL; + dirs[newfd].saved_errno = dirs[oldfd].saved_errno; + } + } + else + { + dirs[newfd].name = NULL; + dirs[newfd].saved_errno = ENOMEM; + } + } + } + return newfd; +} + +int +dup2 (int oldfd, int newfd) +#undef dup2 +{ + int retval = dup2 (oldfd, newfd); + + if (retval >= 0 && oldfd >= 0 && newfd >= 0 && newfd != oldfd) + { + ensure_dirs_slot (newfd); + if (newfd < dirs_allocated) + { + if (oldfd < dirs_allocated) + { + if (dirs[oldfd].name != NULL) + { + dirs[newfd].name = strdup (dirs[oldfd].name); + if (dirs[newfd].name == NULL) + dirs[newfd].saved_errno = ENOMEM; + } + else + { + dirs[newfd].name = NULL; + dirs[newfd].saved_errno = dirs[oldfd].saved_errno; + } + } + else + { + dirs[newfd].name = NULL; + dirs[newfd].saved_errno = ENOMEM; + } + } + } + return retval; +} + +/* Implement fchdir() in terms of chdir(). */ + +int +fchdir (int fd) +{ + if (fd >= 0) + { + if (fd < dirs_allocated) + { + if (dirs[fd].name != NULL) + return chdir (dirs[fd].name); + else + { + errno = dirs[fd].saved_errno; + return -1; + } + } + else + { + errno = ENOMEM; + return -1; + } + } + else + { + errno = EBADF; + return -1; + } +} |