[src/trunk]: src/sys/kern Update comment to reflect third-party software's us...

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

details:   https://anonhg.NetBSD.org/src/rev/1b10dc148530
branches:  trunk
changeset: 846460:1b10dc148530
user:      nia <nia%NetBSD.org@localhost>
date:      Sun Nov 17 12:32:31 2019 +0000

description:
Update comment to reflect third-party software's usage of KERN_ARND.

Changing it as the comment suggests would be a very terrible idea due to
the common usage of this variable.

Returning only 32 or 64 bits also seems to be the purpose of KERN_URND,
so that functionality is already present.

diffstat:

 sys/kern/subr_cprng.c |  9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diffs (30 lines):

diff -r 2b4e903a6aee -r 1b10dc148530 sys/kern/subr_cprng.c
--- a/sys/kern/subr_cprng.c     Sun Nov 17 11:46:38 2019 +0000
+++ b/sys/kern/subr_cprng.c     Sun Nov 17 12:32:31 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_cprng.c,v 1.31 2019/09/02 20:09:30 riastradh Exp $ */
+/*     $NetBSD: subr_cprng.c,v 1.32 2019/11/17 12:32:31 nia Exp $ */
 
 /*-
  * Copyright (c) 2011-2013 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.31 2019/09/02 20:09:30 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.32 2019/11/17 12:32:31 nia Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -581,8 +581,9 @@
  * requested.  Evidently this was used to key RC4 in userspace.
  *
  * In NetBSD, the libc stack-smash-protection code reads 64 bytes
- * from here at every program startup.  So though it would be nice
- * to make this node return only 32 or 64 bits, we can't.  Too bad!
+ * from here at every program startup.  Third-party software also often
+ * uses this to obtain a key for CSPRNG, reading 32 bytes or more, while
+ * avoiding the need to open /dev/urandom.
  */
 static int
 sysctl_kern_arnd(SYSCTLFN_ARGS)