1 /* Set the access and modification time of a file relative to directory fd.
2 Copyright (C) 2009-2018 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 #include <sys/stat.h>
22
23 #include <errno.h>
24 #include <fcntl.h>
25
26 #include "stat-time.h"
27 #include "timespec.h"
28 #include "utimens.h"
29
30 #if HAVE_UTIMENSAT
31
32 # undef utimensat
33
34 /* If we have a native utimensat, but are compiling this file, then
35 utimensat was defined to rpl_utimensat by our replacement
36 sys/stat.h. We assume the native version might fail with ENOSYS,
37 or succeed without properly affecting ctime (as is the case when
38 using newer glibc but older Linux kernel). In this scenario,
39 rpl_utimensat checks whether the native version is usable, and
40 local_utimensat provides the fallback manipulation. */
41
42 static int local_utimensat (int, char const *, struct timespec const[2], int);
43 # define AT_FUNC_NAME local_utimensat
44
45 /* Like utimensat, but work around native bugs. */
46
47 int
rpl_utimensat(int fd,char const * file,struct timespec const times[2],int flag)48 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
49 int flag)
50 {
51 # if defined __linux__ || defined __sun
52 struct timespec ts[2];
53 # endif
54
55 /* See comments in utimens.c for details. */
56 static int utimensat_works_really; /* 0 = unknown, 1 = yes, -1 = no. */
57 if (0 <= utimensat_works_really)
58 {
59 int result;
60 # if defined __linux__ || defined __sun
61 struct stat st;
62 /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
63 systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
64 but work if both times are either explicitly specified or
65 UTIME_NOW. Work around it with a preparatory [l]stat prior
66 to calling utimensat; fortunately, there is not much timing
67 impact due to the extra syscall even on file systems where
68 UTIME_OMIT would have worked.
69
70 The same bug occurs in Solaris 11.1 (Apr 2013).
71
72 FIXME: Simplify this in 2024, when these file system bugs are
73 no longer common on Gnulib target platforms. */
74 if (times && (times[0].tv_nsec == UTIME_OMIT
75 || times[1].tv_nsec == UTIME_OMIT))
76 {
77 if (fstatat (fd, file, &st, flag))
78 return -1;
79 if (times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
80 return 0;
81 if (times[0].tv_nsec == UTIME_OMIT)
82 ts[0] = get_stat_atime (&st);
83 else
84 ts[0] = times[0];
85 if (times[1].tv_nsec == UTIME_OMIT)
86 ts[1] = get_stat_mtime (&st);
87 else
88 ts[1] = times[1];
89 times = ts;
90 }
91 # ifdef __hppa__
92 /* Linux kernel 2.6.22.19 on hppa does not reject invalid tv_nsec
93 values. */
94 else if (times
95 && ((times[0].tv_nsec != UTIME_NOW
96 && ! (0 <= times[0].tv_nsec
97 && times[0].tv_nsec < TIMESPEC_RESOLUTION))
98 || (times[1].tv_nsec != UTIME_NOW
99 && ! (0 <= times[1].tv_nsec
100 && times[1].tv_nsec < TIMESPEC_RESOLUTION))))
101 {
102 errno = EINVAL;
103 return -1;
104 }
105 # endif
106 # endif
107 result = utimensat (fd, file, times, flag);
108 /* Linux kernel 2.6.25 has a bug where it returns EINVAL for
109 UTIME_NOW or UTIME_OMIT with non-zero tv_sec, which
110 local_utimensat works around. Meanwhile, EINVAL for a bad
111 flag is indeterminate whether the native utimensat works, but
112 local_utimensat will also reject it. */
113 if (result == -1 && errno == EINVAL && (flag & ~AT_SYMLINK_NOFOLLOW))
114 return result;
115 if (result == 0 || (errno != ENOSYS && errno != EINVAL))
116 {
117 utimensat_works_really = 1;
118 return result;
119 }
120 }
121 /* No point in trying openat/futimens, since on Linux, futimens is
122 implemented with the same syscall as utimensat. Only avoid the
123 native utimensat due to an ENOSYS failure; an EINVAL error was
124 data-dependent, and the next caller may pass valid data. */
125 if (0 <= utimensat_works_really && errno == ENOSYS)
126 utimensat_works_really = -1;
127 return local_utimensat (fd, file, times, flag);
128 }
129
130 #else /* !HAVE_UTIMENSAT */
131
132 # define AT_FUNC_NAME utimensat
133
134 #endif /* !HAVE_UTIMENSAT */
135
136 /* Set the access and modification timestamps of FILE to be
137 TIMESPEC[0] and TIMESPEC[1], respectively; relative to directory
138 FD. If flag is AT_SYMLINK_NOFOLLOW, change the times of a symlink,
139 or fail with ENOSYS if not possible. If TIMESPEC is null, set the
140 timestamps to the current time. If possible, do it without
141 changing the working directory. Otherwise, resort to using
142 save_cwd/fchdir, then utimens/restore_cwd. If either the save_cwd
143 or the restore_cwd fails, then give a diagnostic and exit nonzero.
144 Return 0 on success, -1 (setting errno) on failure. */
145
146 /* AT_FUNC_NAME is now utimensat or local_utimensat. */
147 #define AT_FUNC_F1 lutimens
148 #define AT_FUNC_F2 utimens
149 #define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
150 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct timespec const ts[2], int flag
151 #define AT_FUNC_POST_FILE_ARGS , ts
152 #include "at-func.c"
153 #undef AT_FUNC_NAME
154 #undef AT_FUNC_F1
155 #undef AT_FUNC_F2
156 #undef AT_FUNC_USE_F1_COND
157 #undef AT_FUNC_POST_FILE_PARAM_DECLS
158 #undef AT_FUNC_POST_FILE_ARGS
159