gettimeofday, settimeofday(2): limit timezone support

For gettimeofday(2), always copy out an empty timezone struct.  For
settimeofday(2), still copyin(9) the struct but ignore the contents.

In gettimeofday(2)'s case we have not changed the original BSD semantics:
the kernel only tracks UTC time without an offset for DST, so a zeroed
timezone struct is the correct thing to return to the caller.

Future work could move these out into libc as stubs for clock_gettime and
clock_settime(2).  But, definitely a "later" thing, given that we are in
beta.

Update the manpage to de-emphasize the timezone parameters for these
syscalls.

Discussed with tedu@, deraadt@, millert@, kettenis@, yasuoka@, jca@, and
guenther@.  Tested by job@.  Ports input from jca@ and sthen@.  Manpage
input from jca@.

ok jca@ deraadt@

1 files changed, 31 insertions, 31 deletions

diff --git a/lib/libc/sys/gettimeofday.2 b/lib/libc/sys/gettimeofday.2
index 3f32e7b6fbf..d12078671bc 100644
--- a/lib/libc/sys/gettimeofday.2
+++ b/lib/libc/sys/gettimeofday.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: gettimeofday.2,v 1.30 2019/01/18 05:03:42 cheloha Exp $
+.\"	$OpenBSD: gettimeofday.2,v 1.31 2019/09/04 14:27:55 cheloha Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)gettimeofday.2	8.2 (Berkeley) 5/26/95
 .\"
-.Dd $Mdocdate: January 18 2019 $
+.Dd $Mdocdate: September 4 2019 $
 .Dt GETTIMEOFDAY 2
 .Os
 .Sh NAME
@@ -43,15 +43,9 @@
 .Ft int
 .Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp"
 .Sh DESCRIPTION
-.Bf -symbolic
-Note: timezone is no longer used; this information is kept outside
-the kernel.
-.Ef
-.Pp
-The system's notion of the current Greenwich time and the current time
-zone is obtained with the
+The system's notion of the current Greenwich time is obtained with the
 .Fn gettimeofday
-call, and set with the
+call and set with the
 .Fn settimeofday
 call.
 The time is expressed in seconds and microseconds
@@ -61,18 +55,12 @@ may be updated continuously or in
 .Dq ticks .
 If
 .Fa tp
-or
-.Fa tzp
 is
 .Dv NULL ,
-the associated time
-information will not be returned or set.
-.Pp
-The structures pointed to by
+the time will not be returned or set.
+The structure pointed to by
 .Fa tp
-and
-.Fa tzp
-are defined in
+is defined in
 .In sys/time.h
 as:
 .Bd -literal
@@ -80,22 +68,34 @@ struct timeval {
 	time_t		tv_sec;		/* seconds since Jan. 1, 1970 */
 	suseconds_t	tv_usec;	/* and microseconds */
 };
-
-struct timezone {
-	int	tz_minuteswest; /* of Greenwich */
-	int	tz_dsttime;	/* type of dst correction to apply */
-};
 .Ed
 .Pp
 The
-.Fa timezone
-structure indicates the local time zone
-(measured in minutes of time westward from Greenwich),
-and a flag that, if nonzero, indicates that
-Daylight Saving time applies locally during
-the appropriate part of the year.
+.Fa tzp
+parameter is historical and timezone information is no longer
+tracked by the system.
+All code should pass
+.Dv NULL
+for
+.Fa tzp .
+For
+.Fn gettimeofday ,
+if
+.Fa tzp
+is
+.Pf non- Dv NULL
+an empty
+.Dv timezone
+structure will be returned.
+For
+.Fn settimeofday ,
+if
+.Fa tzp
+is
+.Pf non- Dv NULL
+its contents are ignored.
 .Pp
-Only the superuser may set the time of day or time zone.
+Only the superuser may set the time of day.
 If the system securelevel is greater than 1 (see
 .Xr init 8 ) ,
 the time may only be advanced.