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[PATCH v4 3/3] y2038: linux: Provide __clock_settime64 implementation
- From: Lukasz Majewski <lukma at denx dot de>
- To: libc-alpha at sourceware dot org
- Cc: Stepan Golosunov <stepan at golosunov dot pp dot ru>, Arnd Bergmann <arnd at arndb dot de>, Paul Eggert <eggert at cs dot ucla dot edu>, Joseph Myers <joseph at codesourcery dot com>, Lukasz Majewski <lukma at denx dot de>
- Date: Mon, 20 May 2019 12:27:23 +0200
- Subject: [PATCH v4 3/3] y2038: linux: Provide __clock_settime64 implementation
- References: <20190414220841.20243-1-lukma@denx.de> <20190520102723.5380-1-lukma@denx.de>
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(-)
diff --git a/include/time.h b/include/time.h
index 6ca4911235..88413d8031 100644
--- a/include/time.h
+++ b/include/time.h
@@ -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.
diff --git a/sysdeps/unix/sysv/linux/clock_settime.c b/sysdeps/unix/sysv/linux/clock_settime.c
index d837e3019c..19559d1e76 100644
--- a/sysdeps/unix/sysv/linux/clock_settime.c
+++ b/sysdeps/unix/sysv/linux/clock_settime.c
@@ -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
--
2.11.0