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, 3 insertions, 3 deletions

diff --git a/lib/libc/gen/auth_subr.c b/lib/libc/gen/auth_subr.c
index 1286a96fe40..11c6416a274 100644
--- a/lib/libc/gen/auth_subr.c
+++ b/lib/libc/gen/auth_subr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: auth_subr.c,v 1.54 2019/12/04 06:25:45 deraadt Exp $	*/
+/*	$OpenBSD: auth_subr.c,v 1.55 2020/07/06 13:33:06 pirofti Exp $	*/
 
 /*
  * Copyright (c) 2000-2002,2004 Todd C. Miller <millert@openbsd.org>
@@ -752,7 +752,7 @@ auth_check_expire(auth_session_t *as)
 
 	if (as->pwd && (quad_t)as->pwd->pw_expire != 0) {
 		if (as->now.tv_sec == 0)
-			gettimeofday(&as->now, NULL);
+			WRAP(gettimeofday)(&as->now, NULL);
 		if ((quad_t)as->now.tv_sec >= (quad_t)as->pwd->pw_expire) {
 			as->state &= ~AUTH_ALLOW;
 			as->state |= AUTH_EXPIRED;
@@ -779,7 +779,7 @@ auth_check_change(auth_session_t *as)
 
 	if (as->pwd && (quad_t)as->pwd->pw_change) {
 		if (as->now.tv_sec == 0)
-			gettimeofday(&as->now, NULL);
+			WRAP(gettimeofday)(&as->now, NULL);
 		if (as->now.tv_sec >= (quad_t)as->pwd->pw_change) {
 			as->state &= ~AUTH_ALLOW;
 			as->state |= AUTH_PWEXPIRED;