[PATCH v5 15/24] posix-timers: Implement y2038 safe clock_getres64() callback

[Baolin Wang]

The clock_getres() callback in struct k_clock is not year 2038 safe on
32bit systems.

To address this implement a new callback clock_getres64() which uses
struct timespec64 along with a default implementation which is a
wrapper for the existing clock_getres() callback. The default callback
is installed at registration time for all posix clocks which are not
yet converted to clock_getres64() and will be removed once this is
completed.

Use the new callback in __clock_getres().

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
---
 include/linux/posix-timers.h |    1 +
 kernel/time/posix-timers.c   |   31 ++++++++++++++++++++++++-------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index be2123d..35786c5 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -98,6 +98,7 @@ struct k_itimer {
 
 struct k_clock {
 	int (*clock_getres) (const clockid_t which_clock, struct timespec *tp);
+	int (*clock_getres64) (const clockid_t which_clock, struct timespec64 *tp);
 	int (*clock_set) (const clockid_t which_clock,
 			  const struct timespec *tp);
 	int (*clock_set64) (const clockid_t which_clock,
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index a5207f0..0b0663a 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -603,6 +603,20 @@ static int default_clock_get64(const clockid_t which_clock,
 	return ret;
 }
 
+static int default_clock_getres64(const clockid_t which_clock,
+				  struct timespec64 *tp64)
+{
+	struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec tp;
+	int ret;
+
+	ret = kc->clock_getres(which_clock, &tp);
+	if (!ret)
+		*tp64 = timespec_to_timespec64(tp);
+
+	return 0;
+}
+
 void posix_timers_register_clock(const clockid_t clock_id,
 				 struct k_clock *new_clock)
 {
@@ -617,8 +631,8 @@ void posix_timers_register_clock(const clockid_t clock_id,
 		       clock_id);
 		return;
 	}
-	if (!new_clock->clock_getres) {
-		printk(KERN_WARNING "POSIX clock id %d lacks clock_getres()\n",
+	if (!new_clock->clock_getres && !new_clock->clock_getres64) {
+		printk(KERN_WARNING "POSIX clock id %d lacks clock_getres() and clock_getres64()\n",
 		       clock_id);
 		return;
 	}
@@ -631,6 +645,8 @@ void posix_timers_register_clock(const clockid_t clock_id,
 		new_clock->clock_set64 = default_clock_set64;
 	if (new_clock->clock_get && !new_clock->clock_get64)
 		new_clock->clock_get64 = default_clock_get64;
+	if (new_clock->clock_getres && !new_clock->clock_getres64)
+		new_clock->clock_getres64 = default_clock_getres64;
 
 	posix_clocks[clock_id] = *new_clock;
 }
@@ -678,7 +694,8 @@ static struct k_clock *clockid_to_kclock(const clockid_t id)
 		return (id & CLOCKFD_MASK) == CLOCKFD ?
 			&clock_posix_dynamic : &clock_posix_cpu;
 
-	if (id >= MAX_CLOCKS || !posix_clocks[id].clock_getres)
+	if (id >= MAX_CLOCKS || (!posix_clocks[id].clock_getres
+	    && !posix_clocks[id].clock_getres64))
 		return NULL;
 	return &posix_clocks[id];
 }
@@ -1187,25 +1204,25 @@ SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
 	return err;
 }
 
-static int __clock_getres(clockid_t which_clock, struct timespec *ts)
+static int __clock_getres(clockid_t which_clock, struct timespec64 *ts)
 {
 	struct k_clock *kc = clockid_to_kclock(which_clock);
 
 	if (!kc)
 		return -EINVAL;
 
-	return kc->clock_getres(which_clock, ts);
+	return kc->clock_getres64(which_clock, ts);
 }
 
 SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
 		struct timespec __user *, tp)
 {
-	struct timespec rtn_tp;
+	struct timespec64 rtn_tp;
 	int error;
 
 	error = __clock_getres(which_clock, &rtn_tp);
 
-	if (!error && tp && copy_to_user(tp, &rtn_tp, sizeof (rtn_tp)))
+	if (!error && tp && put_timespec(&rtn_tp, tp))
 		error = -EFAULT;
 
 	return error;
-- 
1.7.9.5

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