[src/trunk]: src/sys/kern Simplify logic to disable HWRNGs that fail rngtest.

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

details:   https://anonhg.NetBSD.org/src/rev/f91d65a10744
branches:  trunk
changeset: 807386:f91d65a10744
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Apr 08 03:00:31 2015 +0000

description:
Simplify logic to disable HWRNGs that fail rngtest.

- Mark them RND_FLAG_NO_COLLECT.
- Skip samples from sources marked RND_FLAG_NO_COLLECT.
- Don't ever call rnd_detach_source in softint context.
- Remove bogus use of cpu_softintr_p.

The call to rnd_detach_source in softint can't possibly have ever
worked: if the owner of the source ever tried to detach it by calling
rnd_detach_source again, it would LIST_REMOVE a removed element,
which is broken.

diffstat:

 sys/kern/kern_rndq.c |  54 +++++++++++++++++++++------------------------------
 1 files changed, 22 insertions(+), 32 deletions(-)

diffs (110 lines):

diff -r 7fe4aacb1314 -r f91d65a10744 sys/kern/kern_rndq.c
--- a/sys/kern/kern_rndq.c      Wed Apr 08 02:52:25 2015 +0000
+++ b/sys/kern/kern_rndq.c      Wed Apr 08 03:00:31 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_rndq.c,v 1.35 2015/04/08 02:52:25 riastradh Exp $ */
+/*     $NetBSD: kern_rndq.c,v 1.36 2015/04/08 03:00:31 riastradh Exp $ */
 
 /*-
  * Copyright (c) 1997-2013 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.35 2015/04/08 02:52:25 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.36 2015/04/08 03:00:31 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -55,7 +55,6 @@
 #include <sys/kauth.h>
 #include <sys/once.h>
 #include <sys/rngtest.h>
-#include <sys/cpu.h>   /* XXX temporary, see rnd_detach_source */
 
 #include <dev/rnd_private.h>
 
@@ -752,15 +751,13 @@
        }
        mutex_spin_exit(&rnd_samples.lock);
 
-       if (!cpu_softintr_p()) {        /* XXX XXX very temporary "fix" */
-               if (source->state) {
-                       rnd_sample_free(source->state);
-                       source->state = NULL;
-               }
+       if (source->state) {
+               rnd_sample_free(source->state);
+               source->state = NULL;
+       }
 
-               if (source->test) {
-                       kmem_free(source->test, sizeof(rngtest_t));
-               }
+       if (source->test) {
+               kmem_free(source->test, sizeof(rngtest_t));
        }
 
        rnd_printf_verbose("rnd: %s detached as an entropy source\n",
@@ -1087,19 +1084,25 @@
                last_source = source;
 
                /*
+                * If the source has been disabled, ignore samples from
+                * it.
+                */
+               if (source->flags & RND_FLAG_NO_COLLECT)
+                       goto skip;
+
+               /*
                 * Hardware generators are great but sometimes they
                 * have...hardware issues.  Don't use any data from
                 * them unless it passes some tests.
                 */
                if (source->type == RND_TYPE_RNG) {
                        if (__predict_false(rnd_hwrng_test(sample))) {
-                               /*
-                                * Detach the bad source.  See below.
-                                */
-                               badsource = source;
-                               rnd_printf("rnd: detaching source \"%s\".",
-                                      badsource->name);
-                               break;
+                               mutex_spin_enter(&rndpool_mtx);
+                               source->flags |= RND_FLAG_NO_COLLECT;
+                               mutex_spin_exit(&rndpool_mtx);
+                               rnd_printf("rnd: disabling source \"%s\".",
+                                   badsource->name);
+                               goto skip;
                        }
                }
 
@@ -1118,7 +1121,7 @@
 
                pool_entropy += entropy;
                source->total += sample->entropy;
-               SIMPLEQ_INSERT_TAIL(&df_samples, sample, next);
+skip:          SIMPLEQ_INSERT_TAIL(&df_samples, sample, next);
        }
        rndpool_set_entropy_count(&rnd_pool, pool_entropy);
        if (pool_entropy > RND_ENTROPY_THRESHOLD * 8) {
@@ -1132,19 +1135,6 @@
        mutex_spin_exit(&rndpool_mtx);
 
        /* Now we hold no locks: clean up. */
-       if (__predict_false(badsource)) {
-               /*
-                * The detach routine frees any samples we have not
-                * dequeued ourselves.  For sanity's sake, we simply
-                * free (without using) all dequeued samples from the
-                * point at which we detected a problem onwards.
-                */
-               rnd_detach_source(badsource);
-               while ((sample = SIMPLEQ_FIRST(&dq_samples))) {
-                       SIMPLEQ_REMOVE_HEAD(&dq_samples, next);
-                       rnd_sample_free(sample);
-               }
-       }
        while ((sample = SIMPLEQ_FIRST(&df_samples))) {
                SIMPLEQ_REMOVE_HEAD(&df_samples, next);
                rnd_sample_free(sample);