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Diffstat (limited to 'lib/utimens.c')
| -rw-r--r-- | lib/utimens.c | 542 |
1 files changed, 542 insertions, 0 deletions
diff --git a/lib/utimens.c b/lib/utimens.c new file mode 100644 index 0000000..ece9b07 --- /dev/null +++ b/lib/utimens.c @@ -0,0 +1,542 @@ +/* Set file access and modification times. + + Copyright (C) 2003-2016 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by the + Free Software Foundation; either version 3 of the License, or any + later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +/* derived from a function in touch.c */ + +#include <config.h> + +#define _GL_UTIMENS_INLINE _GL_EXTERN_INLINE +#include "utimens.h" + +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <sys/stat.h> +#include <sys/time.h> +#include <unistd.h> + +#include "stat-time.h" +#include "timespec.h" + +#if HAVE_UTIME_H +# include <utime.h> +#endif + +/* Some systems (even some that do have <utime.h>) don't declare this + structure anywhere. */ +#ifndef HAVE_STRUCT_UTIMBUF +struct utimbuf +{ + long actime; + long modtime; +}; +#endif + +/* Avoid recursion with rpl_futimens or rpl_utimensat. */ +#undef futimens +#undef utimensat + +/* Solaris 9 mistakenly succeeds when given a non-directory with a + trailing slash. Force the use of rpl_stat for a fix. */ +#ifndef REPLACE_FUNC_STAT_FILE +# define REPLACE_FUNC_STAT_FILE 0 +#endif + +#if HAVE_UTIMENSAT || HAVE_FUTIMENS +/* Cache variables for whether the utimensat syscall works; used to + avoid calling the syscall if we know it will just fail with ENOSYS, + and to avoid unnecessary work in massaging timestamps if the + syscall will work. Multiple variables are needed, to distinguish + between the following scenarios on Linux: + utimensat doesn't exist, or is in glibc but kernel 2.6.18 fails with ENOSYS + kernel 2.6.22 and earlier rejects AT_SYMLINK_NOFOLLOW + kernel 2.6.25 and earlier reject UTIME_NOW/UTIME_OMIT with non-zero tv_sec + kernel 2.6.32 used with xfs or ntfs-3g fail to honor UTIME_OMIT + utimensat completely works + For each cache variable: 0 = unknown, 1 = yes, -1 = no. */ +static int utimensat_works_really; +static int lutimensat_works_really; +#endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */ + +/* Validate the requested timestamps. Return 0 if the resulting + timespec can be used for utimensat (after possibly modifying it to + work around bugs in utimensat). Return a positive value if the + timespec needs further adjustment based on stat results: 1 if any + adjustment is needed for utimes, and 2 if any adjustment is needed + for Linux utimensat. Return -1, with errno set to EINVAL, if + timespec is out of range. */ +static int +validate_timespec (struct timespec timespec[2]) +{ + int result = 0; + int utime_omit_count = 0; + if ((timespec[0].tv_nsec != UTIME_NOW + && timespec[0].tv_nsec != UTIME_OMIT + && ! (0 <= timespec[0].tv_nsec + && timespec[0].tv_nsec < TIMESPEC_RESOLUTION)) + || (timespec[1].tv_nsec != UTIME_NOW + && timespec[1].tv_nsec != UTIME_OMIT + && ! (0 <= timespec[1].tv_nsec + && timespec[1].tv_nsec < TIMESPEC_RESOLUTION))) + { + errno = EINVAL; + return -1; + } + /* Work around Linux kernel 2.6.25 bug, where utimensat fails with + EINVAL if tv_sec is not 0 when using the flag values of tv_nsec. + Flag a Linux kernel 2.6.32 bug, where an mtime of UTIME_OMIT + fails to bump ctime. */ + if (timespec[0].tv_nsec == UTIME_NOW + || timespec[0].tv_nsec == UTIME_OMIT) + { + timespec[0].tv_sec = 0; + result = 1; + if (timespec[0].tv_nsec == UTIME_OMIT) + utime_omit_count++; + } + if (timespec[1].tv_nsec == UTIME_NOW + || timespec[1].tv_nsec == UTIME_OMIT) + { + timespec[1].tv_sec = 0; + result = 1; + if (timespec[1].tv_nsec == UTIME_OMIT) + utime_omit_count++; + } + return result + (utime_omit_count == 1); +} + +/* Normalize any UTIME_NOW or UTIME_OMIT values in *TS, using stat + buffer STATBUF to obtain the current timestamps of the file. If + both times are UTIME_NOW, set *TS to NULL (as this can avoid some + permissions issues). If both times are UTIME_OMIT, return true + (nothing further beyond the prior collection of STATBUF is + necessary); otherwise return false. */ +static bool +update_timespec (struct stat const *statbuf, struct timespec *ts[2]) +{ + struct timespec *timespec = *ts; + if (timespec[0].tv_nsec == UTIME_OMIT + && timespec[1].tv_nsec == UTIME_OMIT) + return true; + if (timespec[0].tv_nsec == UTIME_NOW + && timespec[1].tv_nsec == UTIME_NOW) + { + *ts = NULL; + return false; + } + + if (timespec[0].tv_nsec == UTIME_OMIT) + timespec[0] = get_stat_atime (statbuf); + else if (timespec[0].tv_nsec == UTIME_NOW) + gettime (×pec[0]); + + if (timespec[1].tv_nsec == UTIME_OMIT) + timespec[1] = get_stat_mtime (statbuf); + else if (timespec[1].tv_nsec == UTIME_NOW) + gettime (×pec[1]); + + return false; +} + +/* Set the access and modification time stamps of FD (a.k.a. FILE) to be + TIMESPEC[0] and TIMESPEC[1], respectively. + FD must be either negative -- in which case it is ignored -- + or a file descriptor that is open on FILE. + If FD is nonnegative, then FILE can be NULL, which means + use just futimes (or equivalent) instead of utimes (or equivalent), + and fail if on an old system without futimes (or equivalent). + If TIMESPEC is null, set the time stamps to the current time. + Return 0 on success, -1 (setting errno) on failure. */ + +int +fdutimens (int fd, char const *file, struct timespec const timespec[2]) +{ + struct timespec adjusted_timespec[2]; + struct timespec *ts = timespec ? adjusted_timespec : NULL; + int adjustment_needed = 0; + struct stat st; + + if (ts) + { + adjusted_timespec[0] = timespec[0]; + adjusted_timespec[1] = timespec[1]; + adjustment_needed = validate_timespec (ts); + } + if (adjustment_needed < 0) + return -1; + + /* Require that at least one of FD or FILE are potentially valid, to avoid + a Linux bug where futimens (AT_FDCWD, NULL) changes "." rather + than failing. */ + if (fd < 0 && !file) + { + errno = EBADF; + return -1; + } + + /* Some Linux-based NFS clients are buggy, and mishandle time stamps + of files in NFS file systems in some cases. We have no + configure-time test for this, but please see + <http://bugs.gentoo.org/show_bug.cgi?id=132673> for references to + some of the problems with Linux 2.6.16. If this affects you, + compile with -DHAVE_BUGGY_NFS_TIME_STAMPS; this is reported to + help in some cases, albeit at a cost in performance. But you + really should upgrade your kernel to a fixed version, since the + problem affects many applications. */ + +#if HAVE_BUGGY_NFS_TIME_STAMPS + if (fd < 0) + sync (); + else + fsync (fd); +#endif + + /* POSIX 2008 added two interfaces to set file timestamps with + nanosecond resolution; newer Linux implements both functions via + a single syscall. We provide a fallback for ENOSYS (for example, + compiling against Linux 2.6.25 kernel headers and glibc 2.7, but + running on Linux 2.6.18 kernel). */ +#if HAVE_UTIMENSAT || HAVE_FUTIMENS + if (0 <= utimensat_works_really) + { + int result; +# if __linux__ || __sun + /* As recently as Linux kernel 2.6.32 (Dec 2009), several file + systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT, + but work if both times are either explicitly specified or + UTIME_NOW. Work around it with a preparatory [f]stat prior + to calling futimens/utimensat; fortunately, there is not much + timing impact due to the extra syscall even on file systems + where UTIME_OMIT would have worked. + + The same bug occurs in Solaris 11.1 (Apr 2013). + + FIXME: Simplify this for Linux in 2016 and for Solaris in + 2024, when file system bugs are no longer common. */ + if (adjustment_needed == 2) + { + if (fd < 0 ? stat (file, &st) : fstat (fd, &st)) + return -1; + if (ts[0].tv_nsec == UTIME_OMIT) + ts[0] = get_stat_atime (&st); + else if (ts[1].tv_nsec == UTIME_OMIT) + ts[1] = get_stat_mtime (&st); + /* Note that st is good, in case utimensat gives ENOSYS. */ + adjustment_needed++; + } +# endif +# if HAVE_UTIMENSAT + if (fd < 0) + { + result = utimensat (AT_FDCWD, file, ts, 0); +# ifdef __linux__ + /* Work around a kernel bug: + http://bugzilla.redhat.com/442352 + http://bugzilla.redhat.com/449910 + It appears that utimensat can mistakenly return 280 rather + than -1 upon ENOSYS failure. + FIXME: remove in 2010 or whenever the offending kernels + are no longer in common use. */ + if (0 < result) + errno = ENOSYS; +# endif /* __linux__ */ + if (result == 0 || errno != ENOSYS) + { + utimensat_works_really = 1; + return result; + } + } +# endif /* HAVE_UTIMENSAT */ +# if HAVE_FUTIMENS + if (0 <= fd) + { + result = futimens (fd, ts); +# ifdef __linux__ + /* Work around the same bug as above. */ + if (0 < result) + errno = ENOSYS; +# endif /* __linux__ */ + if (result == 0 || errno != ENOSYS) + { + utimensat_works_really = 1; + return result; + } + } +# endif /* HAVE_FUTIMENS */ + } + utimensat_works_really = -1; + lutimensat_works_really = -1; +#endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */ + + /* The platform lacks an interface to set file timestamps with + nanosecond resolution, so do the best we can, discarding any + fractional part of the timestamp. */ + + if (adjustment_needed || (REPLACE_FUNC_STAT_FILE && fd < 0)) + { + if (adjustment_needed != 3 + && (fd < 0 ? stat (file, &st) : fstat (fd, &st))) + return -1; + if (ts && update_timespec (&st, &ts)) + return 0; + } + + { +#if HAVE_FUTIMESAT || HAVE_WORKING_UTIMES + struct timeval timeval[2]; + struct timeval *t; + if (ts) + { + timeval[0].tv_sec = ts[0].tv_sec; + timeval[0].tv_usec = ts[0].tv_nsec / 1000; + timeval[1].tv_sec = ts[1].tv_sec; + timeval[1].tv_usec = ts[1].tv_nsec / 1000; + t = timeval; + } + else + t = NULL; + + if (fd < 0) + { +# if HAVE_FUTIMESAT + return futimesat (AT_FDCWD, file, t); +# endif + } + else + { + /* If futimesat or futimes fails here, don't try to speed things + up by returning right away. glibc can incorrectly fail with + errno == ENOENT if /proc isn't mounted. Also, Mandrake 10.0 + in high security mode doesn't allow ordinary users to read + /proc/self, so glibc incorrectly fails with errno == EACCES. + If errno == EIO, EPERM, or EROFS, it's probably safe to fail + right away, but these cases are rare enough that they're not + worth optimizing, and who knows what other messed-up systems + are out there? So play it safe and fall back on the code + below. */ + +# if (HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG) || HAVE_FUTIMES +# if HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG +# undef futimes +# define futimes(fd, t) futimesat (fd, NULL, t) +# endif + if (futimes (fd, t) == 0) + { +# if __linux__ && __GLIBC__ + /* Work around a longstanding glibc bug, still present as + of 2010-12-27. On older Linux kernels that lack both + utimensat and utimes, glibc's futimes rounds instead of + truncating when falling back on utime. The same bug + occurs in futimesat with a null 2nd arg. */ + if (t) + { + bool abig = 500000 <= t[0].tv_usec; + bool mbig = 500000 <= t[1].tv_usec; + if ((abig | mbig) && fstat (fd, &st) == 0) + { + /* If these two subtractions overflow, they'll + track the overflows inside the buggy glibc. */ + time_t adiff = st.st_atime - t[0].tv_sec; + time_t mdiff = st.st_mtime - t[1].tv_sec; + + struct timeval *tt = NULL; + struct timeval truncated_timeval[2]; + truncated_timeval[0] = t[0]; + truncated_timeval[1] = t[1]; + if (abig && adiff == 1 && get_stat_atime_ns (&st) == 0) + { + tt = truncated_timeval; + tt[0].tv_usec = 0; + } + if (mbig && mdiff == 1 && get_stat_mtime_ns (&st) == 0) + { + tt = truncated_timeval; + tt[1].tv_usec = 0; + } + if (tt) + futimes (fd, tt); + } + } +# endif + + return 0; + } +# endif + } +#endif /* HAVE_FUTIMESAT || HAVE_WORKING_UTIMES */ + + if (!file) + { +#if ! ((HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG) \ + || (HAVE_WORKING_UTIMES && HAVE_FUTIMES)) + errno = ENOSYS; +#endif + return -1; + } + +#if HAVE_WORKING_UTIMES + return utimes (file, t); +#else + { + struct utimbuf utimbuf; + struct utimbuf *ut; + if (ts) + { + utimbuf.actime = ts[0].tv_sec; + utimbuf.modtime = ts[1].tv_sec; + ut = &utimbuf; + } + else + ut = NULL; + + return utime (file, ut); + } +#endif /* !HAVE_WORKING_UTIMES */ + } +} + +/* Set the access and modification time stamps of FILE to be + TIMESPEC[0] and TIMESPEC[1], respectively. */ +int +utimens (char const *file, struct timespec const timespec[2]) +{ + return fdutimens (-1, file, timespec); +} + +/* Set the access and modification time stamps of FILE to be + TIMESPEC[0] and TIMESPEC[1], respectively, without dereferencing + symlinks. Fail with ENOSYS if the platform does not support + changing symlink timestamps, but FILE was a symlink. */ +int +lutimens (char const *file, struct timespec const timespec[2]) +{ + struct timespec adjusted_timespec[2]; + struct timespec *ts = timespec ? adjusted_timespec : NULL; + int adjustment_needed = 0; + struct stat st; + + if (ts) + { + adjusted_timespec[0] = timespec[0]; + adjusted_timespec[1] = timespec[1]; + adjustment_needed = validate_timespec (ts); + } + if (adjustment_needed < 0) + return -1; + + /* The Linux kernel did not support symlink timestamps until + utimensat, in version 2.6.22, so we don't need to mimic + fdutimens' worry about buggy NFS clients. But we do have to + worry about bogus return values. */ + +#if HAVE_UTIMENSAT + if (0 <= lutimensat_works_really) + { + int result; +# if __linux__ || __sun + /* As recently as Linux kernel 2.6.32 (Dec 2009), several file + systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT, + but work if both times are either explicitly specified or + UTIME_NOW. Work around it with a preparatory lstat prior to + calling utimensat; fortunately, there is not much timing + impact due to the extra syscall even on file systems where + UTIME_OMIT would have worked. + + The same bug occurs in Solaris 11.1 (Apr 2013). + + FIXME: Simplify this for Linux in 2016 and for Solaris in + 2024, when file system bugs are no longer common. */ + if (adjustment_needed == 2) + { + if (lstat (file, &st)) + return -1; + if (ts[0].tv_nsec == UTIME_OMIT) + ts[0] = get_stat_atime (&st); + else if (ts[1].tv_nsec == UTIME_OMIT) + ts[1] = get_stat_mtime (&st); + /* Note that st is good, in case utimensat gives ENOSYS. */ + adjustment_needed++; + } +# endif + result = utimensat (AT_FDCWD, file, ts, AT_SYMLINK_NOFOLLOW); +# ifdef __linux__ + /* Work around a kernel bug: + http://bugzilla.redhat.com/442352 + http://bugzilla.redhat.com/449910 + It appears that utimensat can mistakenly return 280 rather + than -1 upon ENOSYS failure. + FIXME: remove in 2010 or whenever the offending kernels + are no longer in common use. */ + if (0 < result) + errno = ENOSYS; +# endif + if (result == 0 || errno != ENOSYS) + { + utimensat_works_really = 1; + lutimensat_works_really = 1; + return result; + } + } + lutimensat_works_really = -1; +#endif /* HAVE_UTIMENSAT */ + + /* The platform lacks an interface to set file timestamps with + nanosecond resolution, so do the best we can, discarding any + fractional part of the timestamp. */ + + if (adjustment_needed || REPLACE_FUNC_STAT_FILE) + { + if (adjustment_needed != 3 && lstat (file, &st)) + return -1; + if (ts && update_timespec (&st, &ts)) + return 0; + } + + /* On Linux, lutimes is a thin wrapper around utimensat, so there is + no point trying lutimes if utimensat failed with ENOSYS. */ +#if HAVE_LUTIMES && !HAVE_UTIMENSAT + { + struct timeval timeval[2]; + struct timeval *t; + int result; + if (ts) + { + timeval[0].tv_sec = ts[0].tv_sec; + timeval[0].tv_usec = ts[0].tv_nsec / 1000; + timeval[1].tv_sec = ts[1].tv_sec; + timeval[1].tv_usec = ts[1].tv_nsec / 1000; + t = timeval; + } + else + t = NULL; + + result = lutimes (file, t); + if (result == 0 || errno != ENOSYS) + return result; + } +#endif /* HAVE_LUTIMES && !HAVE_UTIMENSAT */ + + /* Out of luck for symlinks, but we still handle regular files. */ + if (!(adjustment_needed || REPLACE_FUNC_STAT_FILE) && lstat (file, &st)) + return -1; + if (!S_ISLNK (st.st_mode)) + return fdutimens (-1, file, ts); + errno = ENOSYS; + return -1; +} |