1 /* provide a replacement openat function
2 Copyright (C) 2004-2011 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 */
19 /* If the user's config.h happens to include <fcntl.h>, let it include only
20 the system's <fcntl.h> here, so that orig_openat doesn't recurse to
22 #define __need_system_fcntl_h
25 /* Get the original definition of open. It might be defined as a macro. */
27 #include <sys/types.h>
28 #undef __need_system_fcntl_h
32 orig_openat (int fd, char const *filename, int flags, mode_t mode)
34 return openat (fd, filename, flags, mode);
38 /* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
39 this include because of the preliminary #include <fcntl.h> above. */
49 #include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
50 #include "openat-priv.h"
55 /* Like openat, but work around Solaris 9 bugs with trailing slash. */
57 rpl_openat (int dfd, char const *filename, int flags, ...)
66 va_start (arg, flags);
68 /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
69 creates crashing code when 'mode_t' is smaller than 'int'. */
70 mode = va_arg (arg, PROMOTED_MODE_T);
75 # if OPEN_TRAILING_SLASH_BUG
76 /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
77 is specified, then fail.
78 Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
80 "A pathname that contains at least one non-slash character and that
81 ends with one or more trailing slashes shall be resolved as if a
82 single dot character ( '.' ) were appended to the pathname."
84 "The special filename dot shall refer to the directory specified by
86 If the named file already exists as a directory, then
87 - if O_CREAT is specified, open() must fail because of the semantics
89 - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
90 <http://www.opengroup.org/susv3/functions/open.html> says that it
91 fails with errno = EISDIR in this case.
92 If the named file does not exist or does not name a directory, then
93 - if O_CREAT is specified, open() must fail since open() cannot create
95 - if O_WRONLY or O_RDWR is specified, open() must fail because the
96 file does not contain a '.' directory. */
97 if (flags & (O_CREAT | O_WRONLY | O_RDWR))
99 size_t len = strlen (filename);
100 if (len > 0 && filename[len - 1] == '/')
108 fd = orig_openat (dfd, filename, flags, mode);
110 # if OPEN_TRAILING_SLASH_BUG
111 /* If the filename ends in a slash and fd does not refer to a directory,
113 Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
115 "A pathname that contains at least one non-slash character and that
116 ends with one or more trailing slashes shall be resolved as if a
117 single dot character ( '.' ) were appended to the pathname."
119 "The special filename dot shall refer to the directory specified by
121 If the named file without the slash is not a directory, open() must fail
125 /* We know len is positive, since open did not fail with ENOENT. */
126 size_t len = strlen (filename);
127 if (filename[len - 1] == '/')
131 if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
144 #else /* !HAVE_OPENAT */
146 /* Replacement for Solaris' openat function.
147 <http://www.google.com/search?q=openat+site:docs.sun.com>
148 First, try to simulate it via open ("/proc/self/fd/FD/FILE").
149 Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
150 If either the save_cwd or the restore_cwd fails (relatively unlikely),
151 then give a diagnostic and exit nonzero.
152 Otherwise, upon failure, set errno and return -1, as openat does.
153 Upon successful completion, return a file descriptor. */
155 openat (int fd, char const *file, int flags, ...)
162 va_start (arg, flags);
164 /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
165 creates crashing code when 'mode_t' is smaller than 'int'. */
166 mode = va_arg (arg, PROMOTED_MODE_T);
171 return openat_permissive (fd, file, flags, mode, NULL);
174 /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
175 nonnull, set *CWD_ERRNO to an errno value if unable to save
176 or restore the initial working directory. This is needed only
177 the first time remove.c's remove_dir opens a command-line
180 If a previous attempt to restore the current working directory
181 failed, then we must not even try to access a `.'-relative name.
182 It is the caller's responsibility not to call this function
186 openat_permissive (int fd, char const *file, int flags, mode_t mode,
189 struct saved_cwd saved_cwd;
194 if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
195 return open (file, flags, mode);
198 char buf[OPENAT_BUFFER_SIZE];
199 char *proc_file = openat_proc_name (buf, fd, file);
202 int open_result = open (proc_file, flags, mode);
203 int open_errno = errno;
204 if (proc_file != buf)
206 /* If the syscall succeeds, or if it fails with an unexpected
207 errno value, then return right away. Otherwise, fall through
208 and resort to using save_cwd/restore_cwd. */
209 if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
217 save_ok = (save_cwd (&saved_cwd) == 0);
221 openat_save_fail (errno);
224 if (0 <= fd && fd == saved_cwd.desc)
226 /* If saving the working directory collides with the user's
227 requested fd, then the user's fd must have been closed to
229 free_cwd (&saved_cwd);
239 err = open (file, flags, mode);
241 if (save_ok && restore_cwd (&saved_cwd) != 0)
245 /* Don't write a message to just-created fd 2. */
247 if (err == STDERR_FILENO)
249 openat_restore_fail (saved_errno);
255 free_cwd (&saved_cwd);
260 /* Return true if our openat implementation must resort to
261 using save_cwd and restore_cwd. */
263 openat_needs_fchdir (void)
265 bool needs_fchdir = true;
266 int fd = open ("/", O_SEARCH);
270 char buf[OPENAT_BUFFER_SIZE];
271 char *proc_file = openat_proc_name (buf, fd, ".");
274 needs_fchdir = false;
275 if (proc_file != buf)
284 #endif /* !HAVE_OPENAT */