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@

4 files changed, 140 insertions, 0 deletions

diff --git a/regress/lib/libc/timekeep/Makefile b/regress/lib/libc/timekeep/Makefile
new file mode 100644
index 00000000000..ed7dc60379d
--- /dev/null
+++ b/regress/lib/libc/timekeep/Makefile
@@ -0,0 +1,5 @@
+#	$OpenBSD: Makefile,v 1.1 2020/07/06 13:33:06 pirofti Exp $
+
+PROGS=	test_clock_gettime test_time_skew test_gettimeofday
+
+.include <bsd.regress.mk>
diff --git a/regress/lib/libc/timekeep/test_clock_gettime.c b/regress/lib/libc/timekeep/test_clock_gettime.c
new file mode 100644
index 00000000000..cc1d8e36e39
--- /dev/null
+++ b/regress/lib/libc/timekeep/test_clock_gettime.c
@@ -0,0 +1,43 @@
+/*	$OpenBSD: test_clock_gettime.c,v 1.1 2020/07/06 13:33:06 pirofti Exp $ */
+/*
+ * Copyright (c) 2020 Paul Irofti <paul@irofti.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <time.h>
+
+#define ASSERT_EQ(a, b) assert((a) == (b))
+
+void
+check()
+{
+	struct timespec tp = {0};
+
+	ASSERT_EQ(0, clock_gettime(CLOCK_REALTIME, &tp));
+	ASSERT_EQ(0, clock_gettime(CLOCK_MONOTONIC, &tp));
+	ASSERT_EQ(0, clock_gettime(CLOCK_BOOTTIME, &tp));
+	ASSERT_EQ(0, clock_gettime(CLOCK_UPTIME, &tp));
+
+
+	ASSERT_EQ(0, clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &tp));
+	ASSERT_EQ(0, clock_gettime(CLOCK_THREAD_CPUTIME_ID, &tp));
+
+}
+
+int main()
+{
+	check();
+	return 0;
+}
diff --git a/regress/lib/libc/timekeep/test_gettimeofday.c b/regress/lib/libc/timekeep/test_gettimeofday.c
new file mode 100644
index 00000000000..914058505dd
--- /dev/null
+++ b/regress/lib/libc/timekeep/test_gettimeofday.c
@@ -0,0 +1,37 @@
+/*	$OpenBSD: test_gettimeofday.c,v 1.1 2020/07/06 13:33:06 pirofti Exp $ */
+/*
+ * Copyright (c) 2020 Paul Irofti <paul@irofti.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <sys/time.h>
+
+#define ASSERT_EQ(a, b) assert((a) == (b))
+
+void
+check()
+{
+	struct timeval tv = {0};
+	struct timezone tzp;
+
+	ASSERT_EQ(0, gettimeofday(&tv, NULL));
+	ASSERT_EQ(0, gettimeofday(&tv, &tzp));
+}
+
+int main()
+{
+	check();
+	return 0;
+}
diff --git a/regress/lib/libc/timekeep/test_time_skew.c b/regress/lib/libc/timekeep/test_time_skew.c
new file mode 100644
index 00000000000..7871795f06b
--- /dev/null
+++ b/regress/lib/libc/timekeep/test_time_skew.c
@@ -0,0 +1,55 @@
+/*	$OpenBSD: test_time_skew.c,v 1.1 2020/07/06 13:33:06 pirofti Exp $ */
+/*
+ * Copyright (c) 2020 Paul Irofti <paul@irofti.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/time.h>
+
+#include <assert.h>
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define ASSERT_EQ(a, b) assert((a) == (b))
+#define ASSERT_NE(a, b) assert((a) != (b))
+
+void
+check()
+{
+         struct timespec tp1, tp2, tout;
+
+         tout.tv_sec = 0;
+         tout.tv_nsec = 100000;
+
+         ASSERT_EQ(0, clock_gettime(CLOCK_MONOTONIC, &tp1));
+
+         nanosleep(&tout, NULL);
+
+         ASSERT_EQ(0, clock_gettime(CLOCK_MONOTONIC, &tp2));
+
+         /* tp1 should never be larger than tp2 */
+         ASSERT_NE(1, timespeccmp(&tp1, &tp2, >));
+}
+
+int
+main(void)
+{
+	int i;
+
+	for (i = 0; i < 1000; i++)
+		check();
+
+	return 0;
+}