1 /* provide a replacement openat function
2 Copyright (C) 2004, 2005, 2006, 2007 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 2, or (at your option)
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, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 /* written by Jim Meyering */
27 #include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
30 #include "openat-priv.h"
33 /* Replacement for Solaris' openat function.
34 <http://www.google.com/search?q=openat+site:docs.sun.com>
35 First, try to simulate it via open ("/proc/self/fd/FD/FILE").
36 Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
37 If either the save_cwd or the restore_cwd fails (relatively unlikely),
38 then give a diagnostic and exit nonzero.
39 Otherwise, upon failure, set errno and return -1, as openat does.
40 Upon successful completion, return a file descriptor. */
42 openat (int fd, char const *file, int flags, ...)
49 va_start (arg, flags);
51 /* If mode_t is narrower than int, use the promoted type (int),
52 not mode_t. Use sizeof to guess whether mode_t is narrower;
53 we don't know of any practical counterexamples. */
54 mode = (sizeof (mode_t) < sizeof (int)
56 : va_arg (arg, mode_t));
61 return openat_permissive (fd, file, flags, mode, NULL);
64 /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
65 nonnull, set *CWD_ERRNO to an errno value if unable to save
66 or restore the initial working directory. This is needed only
67 the first time remove.c's remove_dir opens a command-line
70 If a previous attempt to restore the current working directory
71 failed, then we must not even try to access a `.'-relative name.
72 It is the caller's responsibility not to call this function
76 openat_permissive (int fd, char const *file, int flags, mode_t mode,
79 struct saved_cwd saved_cwd;
84 if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
85 return open (file, flags, mode);
88 char buf[OPENAT_BUFFER_SIZE];
89 char *proc_file = openat_proc_name (buf, fd, file);
92 int open_result = open (proc_file, flags, mode);
93 int open_errno = errno;
96 /* If the syscall succeeds, or if it fails with an unexpected
97 errno value, then return right away. Otherwise, fall through
98 and resort to using save_cwd/restore_cwd. */
99 if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
107 save_ok = (save_cwd (&saved_cwd) == 0);
111 openat_save_fail (errno);
120 err = open (file, flags, mode);
122 if (save_ok && restore_cwd (&saved_cwd) != 0)
125 openat_restore_fail (errno);
130 free_cwd (&saved_cwd);
135 /* Return true if our openat implementation must resort to
136 using save_cwd and restore_cwd. */
138 openat_needs_fchdir (void)
140 bool needs_fchdir = true;
141 int fd = open ("/", O_RDONLY);
145 char buf[OPENAT_BUFFER_SIZE];
146 char *proc_file = openat_proc_name (buf, fd, ".");
149 needs_fchdir = false;
150 if (proc_file != buf)
161 /* Replacement for Solaris' function by the same name.
162 <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
163 First, try to simulate it via opendir ("/proc/self/fd/FD"). Failing
164 that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
165 If either the save_cwd or the restore_cwd fails (relatively unlikely),
166 then give a diagnostic and exit nonzero.
167 Otherwise, this function works just like Solaris' fdopendir.
170 Unlike the other fd-related functions here, this one
171 effectively consumes its FD parameter. The caller should not
172 close or otherwise manipulate FD if this function returns successfully. */
176 struct saved_cwd saved_cwd;
180 char buf[OPENAT_BUFFER_SIZE];
181 char *proc_file = openat_proc_name (buf, fd, ".");
184 dir = opendir (proc_file);
190 saved_errno = EOPNOTSUPP;
193 /* If the syscall fails with an expected errno value, resort to
194 save_cwd/restore_cwd. */
195 if (! dir && EXPECTED_ERRNO (saved_errno))
197 if (save_cwd (&saved_cwd) != 0)
198 openat_save_fail (errno);
200 if (fchdir (fd) != 0)
210 if (restore_cwd (&saved_cwd) != 0)
211 openat_restore_fail (errno);
214 free_cwd (&saved_cwd);
219 if (proc_file != buf)
227 /* Replacement for Solaris' function by the same name.
228 <http://www.google.com/search?q=fstatat+site:docs.sun.com>
229 First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
230 Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
231 If either the save_cwd or the restore_cwd fails (relatively unlikely),
232 then give a diagnostic and exit nonzero.
233 Otherwise, this function works just like Solaris' fstatat. */
235 #define AT_FUNC_NAME fstatat
236 #define AT_FUNC_F1 lstat
237 #define AT_FUNC_F2 stat
238 #define AT_FUNC_USE_F1_COND flag == AT_SYMLINK_NOFOLLOW
239 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
240 #define AT_FUNC_POST_FILE_ARGS , st
245 #undef AT_FUNC_USE_F1_COND
246 #undef AT_FUNC_POST_FILE_PARAM_DECLS
247 #undef AT_FUNC_POST_FILE_ARGS
249 /* Replacement for Solaris' function by the same name.
250 <http://www.google.com/search?q=unlinkat+site:docs.sun.com>
251 First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE").
252 Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
253 If either the save_cwd or the restore_cwd fails (relatively unlikely),
254 then give a diagnostic and exit nonzero.
255 Otherwise, this function works just like Solaris' unlinkat. */
257 #define AT_FUNC_NAME unlinkat
258 #define AT_FUNC_F1 rmdir
259 #define AT_FUNC_F2 unlink
260 #define AT_FUNC_USE_F1_COND flag == AT_REMOVEDIR
261 #define AT_FUNC_POST_FILE_PARAM_DECLS , int flag
262 #define AT_FUNC_POST_FILE_ARGS /* empty */
267 #undef AT_FUNC_USE_F1_COND
268 #undef AT_FUNC_POST_FILE_PARAM_DECLS
269 #undef AT_FUNC_POST_FILE_ARGS