1 /* provide a replacement openat function
2 Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
17 /* written by Jim Meyering */
27 #include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
29 #include "openat-priv.h"
32 /* Replacement for Solaris' openat function.
33 <http://www.google.com/search?q=openat+site:docs.sun.com>
34 First, try to simulate it via open ("/proc/self/fd/FD/FILE").
35 Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
36 If either the save_cwd or the restore_cwd fails (relatively unlikely),
37 then give a diagnostic and exit nonzero.
38 Otherwise, upon failure, set errno and return -1, as openat does.
39 Upon successful completion, return a file descriptor. */
41 openat (int fd, char const *file, int flags, ...)
48 va_start (arg, flags);
50 /* If mode_t is narrower than int, use the promoted type (int),
51 not mode_t. Use sizeof to guess whether mode_t is narrower;
52 we don't know of any practical counterexamples. */
53 mode = (sizeof (mode_t) < sizeof (int)
55 : va_arg (arg, mode_t));
60 return openat_permissive (fd, file, flags, mode, NULL);
63 /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
64 nonnull, set *CWD_ERRNO to an errno value if unable to save
65 or restore the initial working directory. This is needed only
66 the first time remove.c's remove_dir opens a command-line
69 If a previous attempt to restore the current working directory
70 failed, then we must not even try to access a `.'-relative name.
71 It is the caller's responsibility not to call this function
75 openat_permissive (int fd, char const *file, int flags, mode_t mode,
78 struct saved_cwd saved_cwd;
83 if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
84 return open (file, flags, mode);
87 char buf[OPENAT_BUFFER_SIZE];
88 char *proc_file = openat_proc_name (buf, fd, file);
91 int open_result = open (proc_file, flags, mode);
92 int open_errno = errno;
95 /* If the syscall succeeds, or if it fails with an unexpected
96 errno value, then return right away. Otherwise, fall through
97 and resort to using save_cwd/restore_cwd. */
98 if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
106 save_ok = (save_cwd (&saved_cwd) == 0);
110 openat_save_fail (errno);
119 err = open (file, flags, mode);
121 if (save_ok && restore_cwd (&saved_cwd) != 0)
124 openat_restore_fail (errno);
129 free_cwd (&saved_cwd);
134 /* Return true if our openat implementation must resort to
135 using save_cwd and restore_cwd. */
137 openat_needs_fchdir (void)
139 bool needs_fchdir = true;
140 int fd = open ("/", O_RDONLY);
144 char buf[OPENAT_BUFFER_SIZE];
145 char *proc_file = openat_proc_name (buf, fd, ".");
148 needs_fchdir = false;
149 if (proc_file != buf)
160 /* Replacement for Solaris' function by the same name.
161 <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
162 First, try to simulate it via opendir ("/proc/self/fd/FD"). Failing
163 that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
164 If either the save_cwd or the restore_cwd fails (relatively unlikely),
165 then give a diagnostic and exit nonzero.
166 Otherwise, this function works just like Solaris' fdopendir.
169 Unlike the other fd-related functions here, this one
170 effectively consumes its FD parameter. The caller should not
171 close or otherwise manipulate FD if this function returns successfully. */
175 struct saved_cwd saved_cwd;
179 char buf[OPENAT_BUFFER_SIZE];
180 char *proc_file = openat_proc_name (buf, fd, ".");
183 dir = opendir (proc_file);
189 saved_errno = EOPNOTSUPP;
192 /* If the syscall fails with an expected errno value, resort to
193 save_cwd/restore_cwd. */
194 if (! dir && EXPECTED_ERRNO (saved_errno))
196 if (save_cwd (&saved_cwd) != 0)
197 openat_save_fail (errno);
199 if (fchdir (fd) != 0)
209 if (restore_cwd (&saved_cwd) != 0)
210 openat_restore_fail (errno);
213 free_cwd (&saved_cwd);
218 if (proc_file != buf)
226 /* Replacement for Solaris' function by the same name.
227 <http://www.google.com/search?q=fstatat+site:docs.sun.com>
228 First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
229 Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
230 If either the save_cwd or the restore_cwd fails (relatively unlikely),
231 then give a diagnostic and exit nonzero.
232 Otherwise, this function works just like Solaris' fstatat. */
234 #define AT_FUNC_NAME fstatat
235 #define AT_FUNC_F1 lstat
236 #define AT_FUNC_F2 stat
237 #define AT_FUNC_USE_F1_COND flag == AT_SYMLINK_NOFOLLOW
238 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
239 #define AT_FUNC_POST_FILE_ARGS , st
244 #undef AT_FUNC_USE_F1_COND
245 #undef AT_FUNC_POST_FILE_PARAM_DECLS
246 #undef AT_FUNC_POST_FILE_ARGS
248 /* Replacement for Solaris' function by the same name.
249 <http://www.google.com/search?q=unlinkat+site:docs.sun.com>
250 First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE").
251 Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
252 If either the save_cwd or the restore_cwd fails (relatively unlikely),
253 then give a diagnostic and exit nonzero.
254 Otherwise, this function works just like Solaris' unlinkat. */
256 #define AT_FUNC_NAME unlinkat
257 #define AT_FUNC_F1 rmdir
258 #define AT_FUNC_F2 unlink
259 #define AT_FUNC_USE_F1_COND flag == AT_REMOVEDIR
260 #define AT_FUNC_POST_FILE_PARAM_DECLS , int flag
261 #define AT_FUNC_POST_FILE_ARGS /* empty */
266 #undef AT_FUNC_USE_F1_COND
267 #undef AT_FUNC_POST_FILE_PARAM_DECLS
268 #undef AT_FUNC_POST_FILE_ARGS