1 /* Set the access and modification time of a file relative to directory fd.
2 Copyright (C) 2009-2023 Free Software Foundation, Inc.
3
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.
8
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.
13
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 /* written by Eric Blake */
18
19 #include <config.h>
20
21 /* Specification. */
22 #include <sys/stat.h>
23
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <sys/stat.h>
29
30 #include "stat-time.h"
31 #include "timespec.h"
32 #include "utimens.h"
33
34 #if HAVE_NEARLY_WORKING_UTIMENSAT
35
36 /* Use the original utimensat(), but correct the trailing slash handling. */
37 int
38 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
39 int flag)
40 # undef utimensat
41 {
42 size_t len = strlen (file);
43 if (len && file[len - 1] == '/')
44 {
45 struct stat st;
46 if (fstatat (fd, file, &st, flag & AT_SYMLINK_NOFOLLOW) < 0)
47 return -1;
48 if (!S_ISDIR (st.st_mode))
49 {
50 errno = ENOTDIR;
51 return -1;
52 }
53 }
54
55 return utimensat (fd, file, times, flag);
56 }
57
58 #else
59
60 # if HAVE_UTIMENSAT
61
62 /* If we have a native utimensat, but are compiling this file, then
63 utimensat was defined to rpl_utimensat by our replacement
64 sys/stat.h. We assume the native version might fail with ENOSYS,
65 or succeed without properly affecting ctime (as is the case when
66 using newer glibc but older Linux kernel). In this scenario,
67 rpl_utimensat checks whether the native version is usable, and
68 local_utimensat provides the fallback manipulation. */
69
70 static int local_utimensat (int, char const *, struct timespec const[2], int);
71 # define AT_FUNC_NAME local_utimensat
72
73 /* Like utimensat, but work around native bugs. */
74
75 int
76 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
77 int flag)
78 # undef utimensat
79 {
80 # if defined __linux__ || defined __sun
81 struct timespec ts[2];
82 # endif
83
84 /* See comments in utimens.c for details. */
85 static int utimensat_works_really; /* 0 = unknown, 1 = yes, -1 = no. */
86 if (0 <= utimensat_works_really)
87 {
88 int result;
89 # if defined __linux__ || defined __sun
90 struct stat st;
91 /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
92 systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
93 but work if both times are either explicitly specified or
94 UTIME_NOW. Work around it with a preparatory [l]stat prior
95 to calling utimensat; fortunately, there is not much timing
96 impact due to the extra syscall even on file systems where
97 UTIME_OMIT would have worked.
98
99 The same bug occurs in Solaris 11.1 (Apr 2013).
100
101 FIXME: Simplify this in 2024, when these file system bugs are
102 no longer common on Gnulib target platforms. */
103 if (times && (times[0].tv_nsec == UTIME_OMIT
104 || times[1].tv_nsec == UTIME_OMIT))
105 {
106 if (fstatat (fd, file, &st, flag))
107 return -1;
108 if (times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
109 return 0;
110 if (times[0].tv_nsec == UTIME_OMIT)
111 ts[0] = get_stat_atime (&st);
112 else
113 ts[0] = times[0];
114 if (times[1].tv_nsec == UTIME_OMIT)
115 ts[1] = get_stat_mtime (&st);
116 else
117 ts[1] = times[1];
118 times = ts;
119 }
120 # ifdef __hppa__
121 /* Linux kernel 2.6.22.19 on hppa does not reject invalid tv_nsec
122 values. */
123 else if (times
124 && ((times[0].tv_nsec != UTIME_NOW
125 && ! (0 <= times[0].tv_nsec
126 && times[0].tv_nsec < TIMESPEC_HZ))
127 || (times[1].tv_nsec != UTIME_NOW
128 && ! (0 <= times[1].tv_nsec
129 && times[1].tv_nsec < TIMESPEC_HZ))))
130 {
131 errno = EINVAL;
132 return -1;
133 }
134 # endif
135 # endif
136 # if defined __APPLE__ && defined __MACH__
137 /* macOS 10.13 does not reject invalid tv_nsec values either. */
138 if (times
139 && ((times[0].tv_nsec != UTIME_OMIT
140 && times[0].tv_nsec != UTIME_NOW
141 && ! (0 <= times[0].tv_nsec
142 && times[0].tv_nsec < TIMESPEC_HZ))
143 || (times[1].tv_nsec != UTIME_OMIT
144 && times[1].tv_nsec != UTIME_NOW
145 && ! (0 <= times[1].tv_nsec
146 && times[1].tv_nsec < TIMESPEC_HZ))))
147 {
148 errno = EINVAL;
149 return -1;
150 }
151 size_t len = strlen (file);
152 if (len > 0 && file[len - 1] == '/')
153 {
154 struct stat statbuf;
155 if (fstatat (fd, file, &statbuf, 0) < 0)
156 return -1;
157 if (!S_ISDIR (statbuf.st_mode))
158 {
159 errno = ENOTDIR;
160 return -1;
161 }
162 }
163 # endif
164 result = utimensat (fd, file, times, flag);
165 /* Linux kernel 2.6.25 has a bug where it returns EINVAL for
166 UTIME_NOW or UTIME_OMIT with non-zero tv_sec, which
167 local_utimensat works around. Meanwhile, EINVAL for a bad
168 flag is indeterminate whether the native utimensat works, but
169 local_utimensat will also reject it. */
170 if (result == -1 && errno == EINVAL && (flag & ~AT_SYMLINK_NOFOLLOW))
171 return result;
172 if (result == 0 || (errno != ENOSYS && errno != EINVAL))
173 {
174 utimensat_works_really = 1;
175 return result;
176 }
177 }
178 /* No point in trying openat/futimens, since on Linux, futimens is
179 implemented with the same syscall as utimensat. Only avoid the
180 native utimensat due to an ENOSYS failure; an EINVAL error was
181 data-dependent, and the next caller may pass valid data. */
182 if (0 <= utimensat_works_really && errno == ENOSYS)
183 utimensat_works_really = -1;
184 return local_utimensat (fd, file, times, flag);
185 }
186
187 # else /* !HAVE_UTIMENSAT */
188
189 # define AT_FUNC_NAME utimensat
190
191 # endif /* !HAVE_UTIMENSAT */
192
193 /* Set the access and modification timestamps of FILE to be
194 TIMESPEC[0] and TIMESPEC[1], respectively; relative to directory
195 FD. If flag is AT_SYMLINK_NOFOLLOW, change the times of a symlink,
196 or fail with ENOSYS if not possible. If TIMESPEC is null, set the
197 timestamps to the current time. If possible, do it without
198 changing the working directory. Otherwise, resort to using
199 save_cwd/fchdir, then utimens/restore_cwd. If either the save_cwd
200 or the restore_cwd fails, then give a diagnostic and exit nonzero.
201 Return 0 on success, -1 (setting errno) on failure. */
202
203 /* AT_FUNC_NAME is now utimensat or local_utimensat. */
204 # define AT_FUNC_F1 lutimens
205 # define AT_FUNC_F2 utimens
206 # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
207 # define AT_FUNC_POST_FILE_PARAM_DECLS , struct timespec const ts[2], int flag
208 # define AT_FUNC_POST_FILE_ARGS , ts
209 # include "at-func.c"
210 # undef AT_FUNC_NAME
211 # undef AT_FUNC_F1
212 # undef AT_FUNC_F2
213 # undef AT_FUNC_USE_F1_COND
214 # undef AT_FUNC_POST_FILE_PARAM_DECLS
215 # undef AT_FUNC_POST_FILE_ARGS
216
217 #endif /* !HAVE_NEARLY_WORKING_UTIMENSAT */