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/src/lib/libc/net/res_random.c b/src/lib/libc/net/res_random.c
index 763e420bb8..b7036815c9 100644
--- a/src/lib/libc/net/res_random.c
+++ b/src/lib/libc/net/res_random.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: res_random.c,v 1.24 2016/04/05 04:29:21 guenther Exp $ */
+/* $OpenBSD: res_random.c,v 1.25 2020/07/06 13:33:06 pirofti Exp $ */
 
 /*
  * Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
@@ -219,7 +219,7 @@ res_initid(void)
         if (ru_prf != NULL)
                 arc4random_buf(ru_prf, sizeof(*ru_prf));
 
-        clock_gettime(CLOCK_MONOTONIC, &ts);
+        WRAP(clock_gettime)(CLOCK_MONOTONIC, &ts);
         ru_reseed = ts.tv_sec + RU_OUT;
         ru_msb = ru_msb == 0x8000 ? 0 : 0x8000; 
 }
@@ -232,7 +232,7 @@ __res_randomid(void)
         u_int r;
         static void *randomid_mutex;
 
-        clock_gettime(CLOCK_MONOTONIC, &ts);
+        WRAP(clock_gettime)(CLOCK_MONOTONIC, &ts);
         pid = getpid();
 
         _MUTEX_LOCK(&randomid_mutex);