[src/trunk]: src/sys/dev Simplify /dev/random without reference to entropy_de...

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

details:   https://anonhg.NetBSD.org/src/rev/57f357245f7b
branches:  trunk
changeset: 932477:57f357245f7b
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Fri May 08 15:53:26 2020 +0000

description:
Simplify /dev/random without reference to entropy_depletion.

diffstat:

 sys/dev/random.c |  22 +++++++++-------------
 1 files changed, 9 insertions(+), 13 deletions(-)

diffs (52 lines):

diff -r 1dda4368b382 -r 57f357245f7b sys/dev/random.c
--- a/sys/dev/random.c  Fri May 08 14:56:49 2020 +0000
+++ b/sys/dev/random.c  Fri May 08 15:53:26 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: random.c,v 1.3 2020/05/07 19:05:51 riastradh Exp $     */
+/*     $NetBSD: random.c,v 1.4 2020/05/08 15:53:26 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -47,7 +47,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: random.c,v 1.3 2020/05/07 19:05:51 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: random.c,v 1.4 2020/05/08 15:53:26 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -275,11 +275,10 @@
                n = MIN(n, RANDOM_BUFSIZE);
 
                /*
-                * If we're `depleting' and this is /dev/random, clamp
-                * to the smaller of the entropy capacity or the seed.
+                * Clamp /dev/random output to the entropy capacity and
+                * seed size.  Programs can't rely on long reads.
                 */
-               if (__predict_false(atomic_load_relaxed(&entropy_depletion)) &&
-                   minor(dev) == RND_DEV_RANDOM) {
+               if (minor(dev) == RND_DEV_RANDOM) {
                        n = MIN(n, ENTROPY_CAPACITY);
                        n = MIN(n, sizeof seed);
                        /*
@@ -343,14 +342,11 @@
                        break;
 
                /*
-                * If we're `depleting' and this is /dev/random, stop
-                * here, return what we have, and force the next read
-                * to reseed.  Could grab more from the pool if
-                * possible without blocking, but that's more
-                * work.
+                * If this is /dev/random, stop here, return what we
+                * have, and force the next read to reseed.  Programs
+                * can't rely on /dev/random for long reads.
                 */
-               if (__predict_false(atomic_load_relaxed(&entropy_depletion)) &&
-                   minor(dev) == RND_DEV_RANDOM) {
+               if (minor(dev) == RND_DEV_RANDOM) {
                        error = 0;
                        break;
                }