[v4,3/3] y2038: linux: Provide __clock_settime64 implementation
Commit Message
This patch provides new __clock_settime64 explicit 64 bit function for
setting the time. Moreover, a 32 bit version - __clock_settime - has been
refactored to internally use __clock_settime64.
The __clock_settime is now supposed to be used on systems still supporting
32 bit time (__TIMESIZE != 64) - hence the necessary checks and conversion
to 64 bit struct timespec.
After this change it is intrinsically Y2038 safe.
The new clock_settime64 syscall available from Linux
5.1+ has been used, when applicable, on systems supporting ILP32 data
model.
The __ASSUME_TIME64_SYSCALLS flag indicates if the Linux kernel supports
64 bit version of clock_settime (i.e. clock_settime64).
For systems with __TIMESIZE != 64 as well as ones not supporting this call
(returning -ENOSYS) the fall back code, which supports 32 bit kernel
syscalls ABI (hence the check for __SYSCALL_WORDSIZE to exclude 'x32'), is
executed.
When working on 32 bit systems without Y2038 time support the clock_settime
returns error when one wants to set time with wrong (overflowed) tv_sec
value. Moreover, the correctness of tv_nsec is checked.
In this patch the internal padding (tv_pad) of struct __timespec64 is
left untouched (on 32 bit systems) as Linux kernel ignores upper 32 bits
of tv_nsec.
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_settime64):
Add __clock_settime alias according to __TIMESIZE define
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime):
Refactor this function to be used only on 32 bit machines as a wrapper
on __clock_settime64.
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64): Add
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64):
Use clock_settime64 kernel syscall (available from 5.1-rc1+ Linux) by
32 bit Y2038 safe systems
---
Changes for v4:
- __ASSUME_TIME64_SYSCALLS for fall back path
- Use __SYSCALL_WORDSIZE to exclude 'x32' from execution path (so it will
use x86_64 syscall
- Rewrite the commit message
Changes for v3:
- Rename __ASSUME_64BIT_TIME to __ASSUME_TIME64_SYSCALLS
- Refactor in-code comment (add information regarding Linux kernel ignorance
of padding
- Do not use __TIMESIZE to select main execution path (for Y2038 systems
__TIMESIZE would be changed from 32 to 64 bits at some point to indicate
full Y2038 support
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_settime when clock_settime64
is not available
- Do not copy *tp to timespec - this seems like an overkill as in clock_settime()
the 32 bit struct timespec is copied to internal 64 bit struct __timespec64
---
include/time.h | 8 +++++++
sysdeps/unix/sysv/linux/clock_settime.c | 38 ++++++++++++++++++++++++++++++---
2 files changed, 43 insertions(+), 3 deletions(-)
Comments
20.05.2019 в 12:27:23 +0200 Lukasz Majewski написал:
> /* Set CLOCK to value TP. */
> int
> -__clock_settime (clockid_t clock_id, const struct timespec *tp)
> +__clock_settime64 (clockid_t clock_id, const struct __timespec64 *tp)
> {
> /* Make sure the time cvalue is OK. */
> if (tp->tv_nsec < 0 || tp->tv_nsec >= 1000000000)
> @@ -32,6 +30,40 @@ __clock_settime (clockid_t clock_id, const struct timespec *tp)
> return -1;
> }
>
> +#if __WORDSIZE == 32
> +# ifdef __NR_clock_settime64
> + int ret = INLINE_SYSCALL_CALL (clock_settime64, clock_id, tp);
> +# ifdef __ASSUME_TIME64_SYSCALLS
> + return ret;
> +# else
> + if (ret == 0 || errno != ENOSYS)
> + return ret;
> +# endif
> +# endif
> + /* Fall back to syscall supporting 32bit struct timespec. */
> +# if (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE != 64)
> + struct timespec ts32;
> + valid_timespec64_to_timespec (tp, &ts32);
> + return INLINE_SYSCALL_CALL (clock_settime, clock_id, &ts32);
> +# endif
> +#endif
> return INLINE_SYSCALL_CALL (clock_settime, clock_id, tp);
> }
This still uses __NR_clock_settime even if __ASSUME_TIME64_SYSCALLS is
defined. This won't even compile on newer 32-bit architectures where
__NR_clock_settime is not defined. valid_timespec64_to_timespec
won't exist in these cases too.
And in_time_t_range check is missing for the fallback case.
> weak_alias (__clock_settime, clock_settime)
> +
> +#if __TIMESIZE != 64
> +int
> +__clock_settime (clockid_t clock_id, const struct timespec *tp)
> +{
> + struct __timespec64 ts64;
> +
> + if (! in_time_t_range (tp->tv_sec))
> + {
> + __set_errno (EOVERFLOW);
> + return -1;
> + }
What is this if (false) { … } statement doing here?
> +
> + valid_timespec_to_timespec64 (tp, &ts64);
> + return __clock_settime64 (clock_id, &ts64);
> +}
> +#endif
Hi Stepan,
First of all - thank you for your reply.
> 20.05.2019 в 12:27:23 +0200 Lukasz Majewski написал:
> > /* Set CLOCK to value TP. */
> > int
> > -__clock_settime (clockid_t clock_id, const struct timespec *tp)
> > +__clock_settime64 (clockid_t clock_id, const struct __timespec64
> > *tp) {
> > /* Make sure the time cvalue is OK. */
> > if (tp->tv_nsec < 0 || tp->tv_nsec >= 1000000000)
> > @@ -32,6 +30,40 @@ __clock_settime (clockid_t clock_id, const
> > struct timespec *tp) return -1;
> > }
> >
> > +#if __WORDSIZE == 32
> > +# ifdef __NR_clock_settime64
> > + int ret = INLINE_SYSCALL_CALL (clock_settime64, clock_id, tp);
> > +# ifdef __ASSUME_TIME64_SYSCALLS
> > + return ret;
> > +# else
> > + if (ret == 0 || errno != ENOSYS)
> > + return ret;
> > +# endif
> > +# endif
> > + /* Fall back to syscall supporting 32bit struct timespec. */
> > +# if (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE != 64)
> > + struct timespec ts32;
> > + valid_timespec64_to_timespec (tp, &ts32);
> > + return INLINE_SYSCALL_CALL (clock_settime, clock_id, &ts32);
> > +# endif
> > +#endif
> > return INLINE_SYSCALL_CALL (clock_settime, clock_id, tp);
^^^^^ - [1]
> > }
>
> This still uses __NR_clock_settime even if __ASSUME_TIME64_SYSCALLS is
> defined. This won't even compile on newer 32-bit architectures where
> __NR_clock_settime is not defined. valid_timespec64_to_timespec
> won't exist in these cases too.
Ach... I see your point. The issue would be when we switch to
__TIMESIZE == 64 for 32 bit systems. For that reason the "conversion
functions" from patch [2] shall be compiled always (no matter if we
have __TIMESIZE == 64 or == 32).
And some explanation - the
if (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE != 64) is to
prevent running the fallback on 'x32' - it shall execute on [1]
execution path.
>
> And in_time_t_range check is missing for the fallback case.
Yes - I shall move the in_time_t_range() check from __clock_settime to
the fallback.
Last but not least - the [1] shall be executed only when __WORDSIZE !=
64 - the #else is missing
>
> > weak_alias (__clock_settime, clock_settime)
> > +
> > +#if __TIMESIZE != 64
> > +int
> > +__clock_settime (clockid_t clock_id, const struct timespec *tp)
> > +{
> > + struct __timespec64 ts64;
> > +
> > + if (! in_time_t_range (tp->tv_sec))
> > + {
> > + __set_errno (EOVERFLOW);
> > + return -1;
> > + }
>
> What is this if (false) { … } statement doing here?
Ok, the __clock_settime would receive as an argument the timespec with
32 bit tv_nsec, and tv_sec - hence this check shall be moved from there
to the fallback of __clock_settime64.
Considering the above changes - the code starts to look too much
convoluted. Hence, I would opt for the approach presented in the
__ASSUME_TIME64_SYSCALLS patch reply.
>
> > +
> > + valid_timespec_to_timespec64 (tp, &ts64);
> > + return __clock_settime64 (clock_id, &ts64);
> > +}
> > +#endif
Note:
[2] - [PATCH v4 2/3] y2038: Provide conversion helpers for struct
__timespec64
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
@@ -127,6 +127,14 @@ extern __time64_t __timegm64 (struct tm *__tp) __THROW;
libc_hidden_proto (__timegm64)
#endif
+#if __TIMESIZE == 64
+# define __clock_settime64 __clock_settime
+#else
+extern int __clock_settime64 (clockid_t clock_id,
+ const struct __timespec64 *tp);
+libc_hidden_proto (__clock_settime64)
+#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.
@@ -19,11 +19,9 @@
#include <sysdep.h>
#include <time.h>
-#include "kernel-posix-cpu-timers.h"
-
/* Set CLOCK to value TP. */
int
-__clock_settime (clockid_t clock_id, const struct timespec *tp)
+__clock_settime64 (clockid_t clock_id, const struct __timespec64 *tp)
{
/* Make sure the time cvalue is OK. */
if (tp->tv_nsec < 0 || tp->tv_nsec >= 1000000000)
@@ -32,6 +30,40 @@ __clock_settime (clockid_t clock_id, const struct timespec *tp)
return -1;
}
+#if __WORDSIZE == 32
+# ifdef __NR_clock_settime64
+ int ret = INLINE_SYSCALL_CALL (clock_settime64, clock_id, tp);
+# ifdef __ASSUME_TIME64_SYSCALLS
+ return ret;
+# else
+ if (ret == 0 || errno != ENOSYS)
+ return ret;
+# endif
+# endif
+ /* Fall back to syscall supporting 32bit struct timespec. */
+# if (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE != 64)
+ struct timespec ts32;
+ valid_timespec64_to_timespec (tp, &ts32);
+ return INLINE_SYSCALL_CALL (clock_settime, clock_id, &ts32);
+# endif
+#endif
return INLINE_SYSCALL_CALL (clock_settime, clock_id, tp);
}
weak_alias (__clock_settime, clock_settime)
+
+#if __TIMESIZE != 64
+int
+__clock_settime (clockid_t clock_id, const struct timespec *tp)
+{
+ struct __timespec64 ts64;
+
+ if (! in_time_t_range (tp->tv_sec))
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+
+ valid_timespec_to_timespec64 (tp, &ts64);
+ return __clock_settime64 (clock_id, &ts64);
+}
+#endif