timecounting: add getbinruntime(), getnsecruntime()

The networking people want a fast, monotonic clock that only advances
while the system is not suspended.  The runtime clock satisfies most
of these requirements, so introduce getnsecruntime() to provide a fast
means for reading it.

Based on patches from jca@ and claudio@.

ok yasuoka@

2 files changed, 29 insertions, 2 deletions

diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index e8cc25b02d6..16cf1fa70b7 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_tc.c,v 1.80 2022/12/05 23:18:37 deraadt Exp $ */
+/*	$OpenBSD: kern_tc.c,v 1.81 2022/12/13 17:30:36 cheloha Exp $ */
 
 /*
  * Copyright (c) 2000 Poul-Henning Kamp <phk@FreeBSD.org>
@@ -295,6 +295,30 @@ nanoruntime(struct timespec *ts)
 }
 
 void
+getbinruntime(struct bintime *bt)
+{
+	struct timehands *th;
+	u_int gen;
+
+	do {
+		th = timehands;
+		gen = th->th_generation;
+		membar_consumer();
+		bintimesub(&th->th_offset, &th->th_naptime, bt);
+		membar_consumer();
+	} while (gen == 0 || gen != th->th_generation);
+}
+
+uint64_t
+getnsecruntime(void)
+{
+	struct bintime bt;
+
+	getbinruntime(&bt);
+	return BINTIME_TO_NSEC(&bt);
+}
+
+void
 bintime(struct bintime *bt)
 {
 	struct timehands *th;
diff --git a/sys/sys/time.h b/sys/sys/time.h
index d4736c97cb6..20bfba4cbb8 100644
--- a/sys/sys/time.h
+++ b/sys/sys/time.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: time.h,v 1.62 2022/07/23 22:58:51 cheloha Exp $	*/
+/*	$OpenBSD: time.h,v 1.63 2022/12/13 17:30:36 cheloha Exp $	*/
 /*	$NetBSD: time.h,v 1.18 1996/04/23 10:29:33 mycroft Exp $	*/
 
 /*
@@ -318,6 +318,9 @@ void	nanoboottime(struct timespec *);
 void	binruntime(struct bintime *);
 void	nanoruntime(struct timespec *);
 
+void getbinruntime(struct bintime *);
+uint64_t getnsecruntime(void);
+
 time_t	gettime(void);
 time_t	getuptime(void);