[src/trunk]: src/sys/kern fix and cleanup for tvtohz():

[drochner <drochner%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8cc5f61a066e
branches:  trunk
changeset: 761415:8cc5f61a066e
user:      drochner <drochner%NetBSD.org@localhost>
date:      Wed Jan 26 19:15:13 2011 +0000

description:
fix and cleanup for tvtohz():
-assume (KASSERT) that the timeval given is normalized, and remove
 some partial fixup which I don't see what it is good for
 (I'm ready to back that out if someone tells a reason)
-catch overflows due to conversion of time_t (from tv_sec) to
 integer -- this function doesn't do 64-bit arithmetics (which makes
 sense because relative times which don't fit into 32 bits can be
 considered nonsense here), and before a huge tv_sec could lead to
 a zero hz result, violating the caller's assumptions (in particular
 trigger a diagnostic panic in abstimeout2timo())

diffstat:

 sys/kern/subr_time.c |  17 ++++++++++-------
 1 files changed, 10 insertions(+), 7 deletions(-)

diffs (39 lines):

diff -r eb93b9772819 -r 8cc5f61a066e sys/kern/subr_time.c
--- a/sys/kern/subr_time.c      Wed Jan 26 19:07:42 2011 +0000
+++ b/sys/kern/subr_time.c      Wed Jan 26 19:15:13 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_time.c,v 1.7 2010/04/26 16:26:11 rmind Exp $      */
+/*     $NetBSD: subr_time.c,v 1.8 2011/01/26 19:15:13 drochner Exp $   */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.7 2010/04/26 16:26:11 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.8 2011/01/26 19:15:13 drochner Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -89,12 +89,15 @@
        sec = tv->tv_sec;
        usec = tv->tv_usec;
 
-       if (usec < 0) {
-               sec--;
-               usec += 1000000;
-       }
+       KASSERT(usec >= 0 && usec < 1000000);
 
-       if (sec < 0 || (sec == 0 && usec <= 0)) {
+       /* catch overflows in conversion time_t->int */
+       if (tv->tv_sec > INT_MAX)
+               return INT_MAX;
+       if (tv->tv_sec < 0)
+               return 0;
+
+       if (sec < 0 || (sec == 0 && usec == 0)) {
                /*
                 * Would expire now or in the past.  Return 0 ticks.
                 * This is different from the legacy tvhzto() interface,