1 /* provide a replacement openat function
2 Copyright (C) 2004-2009 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 /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
51 creates crashing code when 'mode_t' is smaller than 'int'. */
52 mode = va_arg (arg, PROMOTED_MODE_T);
57 return openat_permissive (fd, file, flags, mode, NULL);
60 /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
61 nonnull, set *CWD_ERRNO to an errno value if unable to save
62 or restore the initial working directory. This is needed only
63 the first time remove.c's remove_dir opens a command-line
66 If a previous attempt to restore the current working directory
67 failed, then we must not even try to access a `.'-relative name.
68 It is the caller's responsibility not to call this function
72 openat_permissive (int fd, char const *file, int flags, mode_t mode,
75 struct saved_cwd saved_cwd;
80 if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
81 return open (file, flags, mode);
84 char buf[OPENAT_BUFFER_SIZE];
85 char *proc_file = openat_proc_name (buf, fd, file);
88 int open_result = open (proc_file, flags, mode);
89 int open_errno = errno;
92 /* If the syscall succeeds, or if it fails with an unexpected
93 errno value, then return right away. Otherwise, fall through
94 and resort to using save_cwd/restore_cwd. */
95 if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
103 save_ok = (save_cwd (&saved_cwd) == 0);
107 openat_save_fail (errno);
116 err = open (file, flags, mode);
118 if (save_ok && restore_cwd (&saved_cwd) != 0)
121 openat_restore_fail (errno);
126 free_cwd (&saved_cwd);
131 /* Return true if our openat implementation must resort to
132 using save_cwd and restore_cwd. */
134 openat_needs_fchdir (void)
136 bool needs_fchdir = true;
137 int fd = open ("/", O_RDONLY);
141 char buf[OPENAT_BUFFER_SIZE];
142 char *proc_file = openat_proc_name (buf, fd, ".");
145 needs_fchdir = false;
146 if (proc_file != buf)
157 /* Replacement for Solaris' function by the same name.
158 <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
159 First, try to simulate it via opendir ("/proc/self/fd/FD"). Failing
160 that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
161 If either the save_cwd or the restore_cwd fails (relatively unlikely),
162 then give a diagnostic and exit nonzero.
163 Otherwise, this function works just like Solaris' fdopendir.
166 Unlike the other fd-related functions here, this one
167 effectively consumes its FD parameter. The caller should not
168 close or otherwise manipulate FD if this function returns successfully. */
172 struct saved_cwd saved_cwd;
176 char buf[OPENAT_BUFFER_SIZE];
177 char *proc_file = openat_proc_name (buf, fd, ".");
180 dir = opendir (proc_file);
186 saved_errno = EOPNOTSUPP;
189 /* If the syscall fails with an expected errno value, resort to
190 save_cwd/restore_cwd. */
191 if (! dir && EXPECTED_ERRNO (saved_errno))
193 if (save_cwd (&saved_cwd) != 0)
194 openat_save_fail (errno);
196 if (fchdir (fd) != 0)
206 if (restore_cwd (&saved_cwd) != 0)
207 openat_restore_fail (errno);
210 free_cwd (&saved_cwd);
215 if (proc_file != buf)
223 /* Replacement for Solaris' function by the same name.
224 <http://www.google.com/search?q=fstatat+site:docs.sun.com>
225 First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
226 Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
227 If either the save_cwd or the restore_cwd fails (relatively unlikely),
228 then give a diagnostic and exit nonzero.
229 Otherwise, this function works just like Solaris' fstatat. */
231 #define AT_FUNC_NAME fstatat
232 #define AT_FUNC_F1 lstat
233 #define AT_FUNC_F2 stat
234 #define AT_FUNC_USE_F1_COND flag == AT_SYMLINK_NOFOLLOW
235 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
236 #define AT_FUNC_POST_FILE_ARGS , st
241 #undef AT_FUNC_USE_F1_COND
242 #undef AT_FUNC_POST_FILE_PARAM_DECLS
243 #undef AT_FUNC_POST_FILE_ARGS
245 /* Replacement for Solaris' function by the same name.
246 <http://www.google.com/search?q=unlinkat+site:docs.sun.com>
247 First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE").
248 Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
249 If either the save_cwd or the restore_cwd fails (relatively unlikely),
250 then give a diagnostic and exit nonzero.
251 Otherwise, this function works just like Solaris' unlinkat. */
253 #define AT_FUNC_NAME unlinkat
254 #define AT_FUNC_F1 rmdir
255 #define AT_FUNC_F2 unlink
256 #define AT_FUNC_USE_F1_COND flag == AT_REMOVEDIR
257 #define AT_FUNC_POST_FILE_PARAM_DECLS , int flag
258 #define AT_FUNC_POST_FILE_ARGS /* empty */
263 #undef AT_FUNC_USE_F1_COND
264 #undef AT_FUNC_POST_FILE_PARAM_DECLS
265 #undef AT_FUNC_POST_FILE_ARGS