[PATCH 08/19] y2038: introduce struct __kernel_timespec

[Arnd Bergmann <arnd at arndb dot de>]

A lot of system calls pass a 'struct timespec' from or to user space,
and we want to change that type to be based on a 64-bit time_t by
default.

This introduces a new type struct __kernel_timespec, which has the
format we want to use eventually, but also has an override so all
architectures that do not define CONFIG_COMPAT_TIME yet still get the
old behavior.
Once all architectures set this, we can remove that override.

This also introduces a get_timespec64/put_timespec64 set of functions
that convert between a __kernel_timespec in user space and a timespec64
in kernel space.

The current behavior of get_timespec64 explicitly zeroes the upper half
of the tv_nsec member, to allow user space to define its own 'struct
timespec' with some padding in it. Whether this is a good or bad idea
is open for discussion.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 include/linux/time64.h    | 17 +++++++++++------
 include/uapi/linux/time.h | 17 +++++++++++++++++
 kernel/time/time.c        | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/include/linux/time64.h b/include/linux/time64.h
index a3831478d9cf..880ebe4b4ba4 100644
--- a/include/linux/time64.h
+++ b/include/linux/time64.h
@@ -1,14 +1,12 @@
 #ifndef _LINUX_TIME64_H
 #define _LINUX_TIME64_H
 
-#include <uapi/linux/time.h>
-
 typedef __s64 time64_t;
 
-/*
- * This wants to go into uapi/linux/time.h once we agreed about the
- * userspace interfaces.
- */
+#ifndef CONFIG_COMPAT_TIME
+# define __kernel_timespec timespec
+#endif
+
 #if __BITS_PER_LONG == 64
 # define timespec64 timespec
 #else
@@ -18,6 +16,8 @@ struct timespec64 {
 };
 #endif
 
+#include <uapi/linux/time.h>
+
 /* Parameters used to convert the timespec values: */
 #define MSEC_PER_SEC	1000L
 #define USEC_PER_MSEC	1000L
@@ -187,4 +187,9 @@ static __always_inline void timespec64_add_ns(struct timespec64 *a, u64 ns)
 
 #endif
 
+extern int get_timespec64(struct timespec64 *ts,
+			  const struct __kernel_timespec __user *uts);
+extern int put_timespec64(const struct timespec64 *ts,
+			  struct __kernel_timespec __user *uts);
+
 #endif /* _LINUX_TIME64_H */
diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h
index e75e1b6ff27f..72d894df3013 100644
--- a/include/uapi/linux/time.h
+++ b/include/uapi/linux/time.h
@@ -66,4 +66,21 @@ struct itimerval {
  */
 #define TIMER_ABSTIME			0x01
 
+/* types based on 64-bit time_t */
+#ifndef __kernel_timespec
+typedef __s64 __kernel_time64_t;
+
+struct __kernel_timespec {
+	__kernel_time64_t	tv_sec;
+	__s64			tv_nsec;
+};
+#endif
+
+#ifndef __kernel_itimerspec
+struct __kernel_itimerspec {
+	struct __kernel_timespec it_interval;
+	struct __kernel_timespec it_value;
+};
+#endif
+
 #endif /* _UAPI_LINUX_TIME_H */
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 2c85b7724af4..845af1db66fa 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -30,6 +30,7 @@
 #include <linux/export.h>
 #include <linux/timex.h>
 #include <linux/capability.h>
+#include <linux/compat.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/errno.h>
 #include <linux/syscalls.h>
@@ -37,6 +38,7 @@
 #include <linux/fs.h>
 #include <linux/math64.h>
 #include <linux/ptrace.h>
+#include <linux/time64.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -783,3 +785,33 @@ struct timespec timespec_add_safe(const struct timespec lhs,
 
 	return res;
 }
+
+int get_timespec64(struct timespec64 *ts,
+		   const struct __kernel_timespec __user *uts)
+{
+	struct __kernel_timespec kts;
+	int ret;
+
+	ret = copy_from_user(&kts, uts, sizeof(kts));
+	if (ret)
+		return -EFAULT;
+
+	ts->tv_sec = kts.tv_sec;
+	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
+		kts.tv_nsec &= 0xfffffffful;
+	ts->tv_nsec = kts.tv_nsec;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_timespec64);
+
+int put_timespec64(const struct timespec64 *ts,
+		   struct __kernel_timespec __user *uts)
+{
+	struct __kernel_timespec kts = {
+		.tv_sec = ts->tv_sec,
+		.tv_nsec = ts->tv_nsec
+	};
+	return copy_to_user(uts, &kts, sizeof(kts)) ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(put_timespec64);
-- 
2.1.0.rc2