[v2,5/7] y2038: linux: Provide __clock_getres64 implementation
Commit Message
This patch provides new __clock_getres64 explicit 64 bit function for
getting the resolution (precision) of specified clock ID. Moreover, a
32 bit version - __clock_getres has been refactored to internally use
__clock_getres64.
The __clock_getres is now supposed to be used on 32 bit systems -
hence the necessary checks and conversion to 64 bit type. After this
change it is intrinsically Y2038 safe.
The new 64 bit syscall (clock_getres_time64) available from Linux
5.1+ has been used when applicable on 32 bit systems.
The __ASSUME_64BIT_TIME flag indicates if the Linux kernel provides 64 bit
version of clock_getres (i.e. clock_getres_time64). If defined - return
value is returned unconditionally. If not - the 32 bit version of this
syscall is executed instead.
When working on 32 bit systems without Y2038 time support the
clock_getres returns error when received tv_sec is wrong (i.e. overflowed).
Moreover, the correctness of tv_nsec is checked.
The execution path on 64 bit systems has not been changed or affected
in any way.
Tests:
- The code has been tested with x86_64/x86 (native compilation):
make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8"
- 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
on kernels with and without 64 bit time support.
No regressions were observed.
* include/time.h (__clock_getres64):
Add __clock_getres alias according to __TIMESIZE define
* sysdeps/unix/sysv/linux/clock_getres.c (__clock_getres):
Refactor this function to be used only on 32 bit machines as a
wrapper on __clock_getres64.
* sysdeps/unix/sysv/linux/clock_getres.c (__clock_getres64): Add
* sysdeps/unix/sysv/linux/clock_getres.c (__clock_getres64):
Use clock_getres_time64 kernel syscall (available from 5.1-rc1+
Linux) by 32 bit Y2038 safe systems
---
Changes for v2:
- Add support for __ASSUME_64BIT_TIME flag when Linux kernel provides
syscalls supporting 64 bit time on 32 bit systems
- Provide fallback to 32 bit version of clock_getres when
clock_getres_time64 is not available
---
include/time.h | 8 +++++++
sysdeps/unix/sysv/linux/clock_getres.c | 39 +++++++++++++++++++++++++++++++++-
2 files changed, 46 insertions(+), 1 deletion(-)
@@ -140,6 +140,14 @@ extern int __clock_settime64 (clockid_t clock_id,
libc_hidden_proto (__clock_settime64)
#endif
+#if __TIMESIZE == 64
+# define __clock_getres64 __clock_getres
+#else
+extern int __clock_getres64 (clockid_t clock_id,
+ struct __timespec64 *tp);
+libc_hidden_proto (__clock_getres64);
+#endif
+
/* 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.
@@ -28,8 +28,45 @@
/* Get resolution of clock. */
int
-__clock_getres (clockid_t clock_id, struct timespec *res)
+__clock_getres64 (clockid_t clock_id, struct __timespec64 *res)
{
+#if defined (__TIMESIZE) && __TIMESIZE != 64
+# ifdef __NR_clock_getres_time64
+ int ret = INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
+# ifdef __ASSUME_64BIT_TIME
+ return ret;
+# else
+ if (ret == 0 || errno != ENOSYS)
+ /* Preserve non-error/non-ENOSYS return values. */
+ return ret;
+# endif
+# endif
+ struct timespec ts32;
+ int retval = INLINE_VSYSCALL (clock_getres, 2, clock_id, &ts32);
+ if (! retval)
+ valid_timespec_to_timespec64(&ts32, res);
+
+ return retval;
+#else
return INLINE_VSYSCALL (clock_getres, 2, clock_id, res);
+#endif
}
weak_alias (__clock_getres, clock_getres)
+
+#if __TIMESIZE != 64
+int
+__clock_getres (clockid_t clock_id, struct timespec *res)
+{
+ struct __timespec64 ts64;
+ int retval;
+
+ retval = __clock_getres64 (clock_id, &ts64);
+ if (! retval && res && ! timespec64_to_timespec (&ts64, res))
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+
+ return retval;
+}
+#endif