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[PATCH 1/2] y2038: linux: Provide __utimensat64 implementation


This patch provides new __utimensat64 explicit 64 bit function for
setting access and modification time of a file. Moreover, a 32 bit version -
__utimensat has been refactored to internally use __utimensat64.

The __utimensat is now supposed to be used on systems still supporting
32 bit time (__TIMESIZE != 64) - hence the necessary conversions to 64 bit
struct __timespec64.
When pointer to struct __timespec64 is NULL - the file access and modification
time is set to the current one and no conversions from struct timespec to
__timespec64 are performed.

The new utimensat_time64 syscall available from Linux 5.1+ has been used,
when applicable.
The new helper function - __utimensat64_helper - has been introduced to
facilitate code re-usage on function providing futimens syscall handling.
It also checks if passed nanoseconds are in the valid range as well as if one of
two special values - UTIME_NOW and UTIME_OMIT were not passed.
Moreover, when utimensat syscall on systems supporting 32 bit time ABI is used,
the check is performed if passed data fits into 32 bit time_t range.

Build tests:
- The code has been tested on x86_64/x86 (native compilation):
make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8"

- The glibc has been build tested (make PARALLELMFLAGS="-j8") for
x86 (i386), x86_64-x32, and armv7

Run-time tests:
- Run specific tests on ARM/x86 32bit systems (qemu):
https://github.com/lmajewski/meta-y2038 and run tests:
https://github.com/lmajewski/y2038-tests/commits/master

- Use of cross-test-ssh.sh for ARM (armv7):
make PARALLELMFLAGS="-j8" test-wrapper='./cross-test-ssh.sh root@192.168.7.2' xcheck

Linux kernel, headers and minimal kernel version for glibc build test
matrix:
- Linux v5.1 (with utimensat_time64) and glibc build with v5.1 as
minimal kernel version (--enable-kernel="5.1.0")
The __ASSUME_TIME64_SYSCALLS flag defined.

- Linux v5.1 and default minimal kernel version
The __ASSUME_TIME64_SYSCALLS not defined, but kernel supports utimensat_time64
syscall.

- Linux v4.19 (no utimensat_time64 support) with default minimal kernel
version for contemporary glibc
This kernel doesn't support utimensat_time64 syscall, so the fallback
to utimensat is tested.

The above tests were performed with Y2038 redirection applied as well as
without (so the __TIMESIZE != 64 execution path is checked as well).

No regressions were observed.
---
 include/time.h                      | 12 +++++
 sysdeps/unix/sysv/linux/utimensat.c | 76 +++++++++++++++++++++++++++--
 2 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/include/time.h b/include/time.h
index de660f7f57..432489ae29 100644
--- a/include/time.h
+++ b/include/time.h
@@ -141,6 +141,18 @@ extern int __clock_getres64 (clockid_t clock_id,
 libc_hidden_proto (__clock_getres64);
 #endif
 
+#if __TIMESIZE == 64
+# define __utimensat64 __utimensat
+#else
+extern int __utimensat64 (int fd, const char *file,
+                          const struct __timespec64 tsp[2], int flags);
+libc_hidden_proto (__utimensat64);
+#endif
+
+extern int __utimensat64_helper (int fd, const char *file,
+                                 const struct __timespec64 tsp[2], int flags);
+libc_hidden_proto (__utimensat64_helper);
+
 /* Compute the `struct tm' representation of T,
    offset OFFSET seconds east of UTC,
    and store year, yday, mon, mday, wday, hour, min, sec into *TP.
diff --git a/sysdeps/unix/sysv/linux/utimensat.c b/sysdeps/unix/sysv/linux/utimensat.c
index 3bffa7d22a..d4b9679d99 100644
--- a/sysdeps/unix/sysv/linux/utimensat.c
+++ b/sysdeps/unix/sysv/linux/utimensat.c
@@ -19,18 +19,86 @@
 #include <errno.h>
 #include <sys/stat.h>
 #include <sysdep.h>
+#include <time.h>
+#include <kernel-features.h>
 
+/* Helper function defined for easy reusage of the code which calls utimensat
+   and utimensat_time64 syscall.  */
+int
+__utimensat64_helper (int fd, const char *file,
+                      const struct __timespec64 tsp64[2], int flags)
+{
+  if (tsp64 && (! valid_nanoseconds(tsp64[0].tv_nsec)
+                || ! valid_nanoseconds(tsp64[1].tv_nsec)))
+    {
+      if (tsp64[0].tv_nsec != UTIME_NOW && tsp64[0].tv_nsec != UTIME_OMIT
+          && tsp64[1].tv_nsec != UTIME_NOW && tsp64[1].tv_nsec != UTIME_OMIT)
+        {
+          __set_errno (EINVAL);
+          return -1;
+        }
+    }
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+# ifndef __NR_utimensat_time64
+#  define __NR_utimensat_time64 __NR_utimensat
+# endif
+  return INLINE_SYSCALL (utimensat_time64, 4, fd, file, &tsp64[0], flags);
+#else
+# ifdef __NR_utimensat_time64
+  int ret = INLINE_SYSCALL (utimensat_time64, 4, fd, file, &tsp64[0], flags);
+  if (ret == 0 || errno != ENOSYS)
+    return ret;
+# endif
+  if (tsp64
+      && (! in_time_t_range (tsp64[0].tv_sec)
+          || ! in_time_t_range (tsp64[1].tv_sec)))
+    {
+      __set_errno (EOVERFLOW);
+      return -1;
+    }
+
+  struct timespec tsp32[2];
+  if (tsp64)
+    {
+      tsp32[0] = valid_timespec64_to_timespec (tsp64[0]);
+      tsp32[1] = valid_timespec64_to_timespec (tsp64[1]);
+    }
+
+  return INLINE_SYSCALL (utimensat, 4, fd, file, tsp64 ? &tsp32[0] : NULL,
+                         flags);
+#endif
+
+}
+libc_hidden_def (__utimensat64_helper)
 
 /* Change the access time of FILE to TSP[0] and
    the modification time of FILE to TSP[1].
 
    Starting with 2.6.22 the Linux kernel has the utimensat syscall.  */
 int
-utimensat (int fd, const char *file, const struct timespec tsp[2],
-	   int flags)
+__utimensat64 (int fd, const char *file, const struct __timespec64 tsp64[2],
+               int flags)
 {
   if (file == NULL)
     return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
-  /* Avoid implicit array coercion in syscall macros.  */
-  return INLINE_SYSCALL (utimensat, 4, fd, file, &tsp[0], flags);
+
+  return __utimensat64_helper (fd, file, &tsp64[0], flags);
+}
+
+#if __TIMESIZE != 64
+int
+__utimensat (int fd, const char *file, const struct timespec tsp[2],
+             int flags)
+{
+  struct __timespec64 tsp64[2];
+  if (tsp)
+    {
+      tsp64[0] = valid_timespec_to_timespec64 (tsp[0]);
+      tsp64[1] = valid_timespec_to_timespec64 (tsp[1]);
+    }
+
+  return __utimensat64 (fd, file, tsp ? &tsp64[0] : NULL, flags);
 }
+#endif
+weak_alias (__utimensat, utimensat)
-- 
2.20.1


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