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authorkib <kib@FreeBSD.org>2012-06-22 07:06:40 +0000
committerkib <kib@FreeBSD.org>2012-06-22 07:06:40 +0000
commit7b36a081088572ce45af9b675b5992adc971506d (patch)
tree37498e393ce83d19f36a986f13f5aa2c5d5095e6 /sys/x86
parent860e30dae9add1199b159f743b020e0d9c533c5f (diff)
downloadFreeBSD-src-7b36a081088572ce45af9b675b5992adc971506d.zip
FreeBSD-src-7b36a081088572ce45af9b675b5992adc971506d.tar.gz
Implement mechanism to export some kernel timekeeping data to
usermode, using shared page. The structures and functions have vdso prefix, to indicate the intended location of the code in some future. The versioned per-algorithm data is exported in the format of struct vdso_timehands, which mostly repeats the content of in-kernel struct timehands. Usermode reading of the structure can be lockless. Compatibility export for 32bit processes on 64bit host is also provided. Kernel also provides usermode with indication about currently used timecounter, so that libc can fall back to syscall if configured timecounter is unknown to usermode code. The shared data updates are initiated both from the tc_windup(), where a fast task is queued to do the update, and from sysctl handlers which change timecounter. A manual override switch kern.timecounter.fast_gettime allows to turn off the mechanism. Only x86 architectures export the real algorithm data, and there, only for tsc timecounter. HPET counters page could be exported as well, but I prefer to not further glue the kernel and libc ABI there until proper vdso-based solution is developed. Minimal stubs neccessary for non-x86 architectures to still compile are provided. Discussed with: bde Reviewed by: jhb Tested by: flo MFC after: 1 month
Diffstat (limited to 'sys/x86')
-rw-r--r--sys/x86/include/vdso.h42
-rw-r--r--sys/x86/x86/tsc.c22
2 files changed, 64 insertions, 0 deletions
diff --git a/sys/x86/include/vdso.h b/sys/x86/include/vdso.h
new file mode 100644
index 0000000..1171420
--- /dev/null
+++ b/sys/x86/include/vdso.h
@@ -0,0 +1,42 @@
+/*-
+ * Copyright 2012 Konstantin Belousov <kib@FreeBSD.ORG>.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _X86_VDSO_H
+#define _X86_VDSO_H
+
+#define VDSO_TIMEHANDS_MD \
+ uint32_t th_x86_shift; \
+ uint32_t th_res[7];
+
+#ifdef _KERNEL
+#ifdef COMPAT_FREEBSD32
+
+#define VDSO_TIMEHANDS_MD32 VDSO_TIMEHANDS_MD
+
+#endif
+#endif
+#endif
diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
index 4d1618f..085c339 100644
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
@@ -27,6 +27,7 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
+#include "opt_compat.h"
#include "opt_clock.h"
#include <sys/param.h>
@@ -41,6 +42,7 @@ __FBSDID("$FreeBSD$");
#include <sys/kernel.h>
#include <sys/power.h>
#include <sys/smp.h>
+#include <sys/vdso.h>
#include <machine/clock.h>
#include <machine/cputypes.h>
#include <machine/md_var.h>
@@ -604,3 +606,23 @@ tsc_get_timecount_low(struct timecounter *tc)
: "=a" (rv) : "c" ((int)(intptr_t)tc->tc_priv) : "edx");
return (rv);
}
+
+uint32_t
+cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th)
+{
+
+ vdso_th->th_x86_shift = (int)(intptr_t)timecounter->tc_priv;
+ bzero(vdso_th->th_res, sizeof(vdso_th->th_res));
+ return (timecounter == &tsc_timecounter);
+}
+
+#ifdef COMPAT_FREEBSD32
+uint32_t
+cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
+{
+
+ vdso_th32->th_x86_shift = (int)(intptr_t)timecounter->tc_priv;
+ bzero(vdso_th32->th_res, sizeof(vdso_th32->th_res));
+ return (timecounter == &tsc_timecounter);
+}
+#endif
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