From 3db15a3f80f193826e144b1944727a65c13340fe Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sat, 25 Jul 2015 18:23:10 +0200
Subject: kern: add boot-time clock, use it for time stamps

The kernel keeps track of task and thread creation times by saving a
time stamp.  Previously, the real-time clock was used for this.  When
the real-time clock is changed, however, the reference frame for the
time stamps is lost.  This surfaced in Hurd systems reporting
spuriously long uptimes.

Fix this by creating a boot-time clock and use it as reference frame
for the time stamps.

* kern/mach_clock.c (clock_boottime_offset): Create clock by keeping
track of the offset from the real-time.
(clock_boottime_update): New function.
(record_time_stamp): Use the boot-time clock for time stamps.
(read_time_stamp): New function to convert it back to real-time.
(host_set_time): Call `clock_boottime_update'.
* kern/mach_clock.h (record_time_stamp): Amend comment.
(read_time_stamp): New declaration.
* kern/task.c (task_info): Use `read_time_stamp'.
* kern/thread.c (thread_info): Likewise.
---
 kern/task.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'kern/task.c')

diff --git a/kern/task.c b/kern/task.c
index b384347..9a3d848 100644
--- a/kern/task.c
+++ b/kern/task.c
@@ -783,7 +783,8 @@ kern_return_t task_info(
 				= task->total_system_time.seconds;
 		basic_info->system_time.microseconds
 				= task->total_system_time.microseconds;
-		basic_info->creation_time = task->creation_time;
+		read_time_stamp(&task->creation_time,
+				&basic_info->creation_time);
 		task_unlock(task);
 
 		if (*task_info_count > TASK_BASIC_INFO_COUNT)
-- 
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