Add support for timeconting in userland.

This diff exposes parts of clock_gettime(2) and gettimeofday(2) to
userland via libc eliberating processes from the need for a context
switch everytime they want to count the passage of time.

If a timecounter clock can be exposed to userland than it needs to set
its tc_user member to a non-zero value. Tested with one or multiple
counters per architecture.

The timing data is shared through a pointer found in the new ELF
auxiliary vector AUX_openbsd_timekeep containing timehands information
that is frequently updated by the kernel.

Timing differences between the last kernel update and the current time
are adjusted in userland by the tc_get_timecount() function inside the
MD usertc.c file.

This permits a much more responsive environment, quite visible in
browsers, office programs and gaming (apparently one is are able to fly
in Minecraft now).

Tested by robert@, sthen@, naddy@, kmos@, phessler@, and many others!

OK from at least kettenis@, cheloha@, naddy@, sthen@

1 files changed, 4 insertions, 2 deletions

diff --git a/sys/arch/sgi/xbow/xheart.c b/sys/arch/sgi/xbow/xheart.c
index 56b29915c70..be5a244a5ae 100644
--- a/sys/arch/sgi/xbow/xheart.c
+++ b/sys/arch/sgi/xbow/xheart.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xheart.c,v 1.32 2018/02/24 11:42:31 visa Exp $	*/
+/*	$OpenBSD: xheart.c,v 1.33 2020/07/06 13:33:08 pirofti Exp $	*/
 
 /*
  * Copyright (c) 2008 Miodrag Vallat.
@@ -83,7 +83,9 @@ struct timecounter xheart_timecounter = {
 	.tc_counter_mask = 0xffffffff,	/* truncate 52-bit counter to 32-bit */
 	.tc_frequency = 12500000,
 	.tc_name = "heart",
-	.tc_quality = 100
+	.tc_quality = 100,
+	.tc_priv = NULL,
+	.tc_user = 0,
 };
 
 extern uint32_t ip30_lights_frob(uint32_t, struct trapframe *);