[src/trunk]: src/sys/kern Centralize bookkeeping of rnd_initial_entropy.

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

details:   https://anonhg.NetBSD.org/src/rev/794084fdc818
branches:  trunk
changeset: 807584:794084fdc818
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Apr 14 14:11:51 2015 +0000

description:
Centralize bookkeeping of rnd_initial_entropy.

It is not adjusted everywhere it should be, although the only places
it perhaps formally ought to be are places with questionable entropy
estimates in the first place.

diffstat:

 sys/kern/kern_rndq.c |  53 ++++++++++++++++++++++++++-------------------------
 1 files changed, 27 insertions(+), 26 deletions(-)

diffs (102 lines):

diff -r e5732449f0a9 -r 794084fdc818 sys/kern/kern_rndq.c
--- a/sys/kern/kern_rndq.c      Tue Apr 14 14:08:36 2015 +0000
+++ b/sys/kern/kern_rndq.c      Tue Apr 14 14:11:51 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_rndq.c,v 1.60 2015/04/14 13:57:35 riastradh Exp $ */
+/*     $NetBSD: kern_rndq.c,v 1.61 2015/04/14 14:11:51 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 1.60 2015/04/14 13:57:35 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.61 2015/04/14 14:11:51 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -290,25 +290,6 @@
 rnd_wakeup_readers(void)
 {
 
-       /*
-        * XXX This bookkeeping shouldn't be here -- this is not where
-        * the rnd_initial_entropy state change actually happens.
-        */
-       mutex_spin_enter(&rnd_global.lock);
-       const size_t entropy_count = rndpool_get_entropy_count(&rnd_global.pool);
-       if (entropy_count < RND_ENTROPY_THRESHOLD * 8) {
-               mutex_spin_exit(&rnd_global.lock);
-               return;
-       } else {
-#ifdef RND_VERBOSE
-               if (__predict_false(!rnd_initial_entropy))
-                       rnd_printf_verbose("rnd: have initial entropy (%zu)\n",
-                           entropy_count);
-#endif
-               rnd_initial_entropy = 1;
-       }
-       mutex_spin_exit(&rnd_global.lock);
-
        rndsinks_distribute();
 }
 
@@ -483,6 +464,27 @@
 #endif
 
 /*
+ * Entropy was just added to the pool.  If we crossed the threshold for
+ * the first time, set rnd_initial_entropy = 1.
+ */
+static void
+rnd_entropy_added(void)
+{
+       uint32_t pool_entropy;
+
+       KASSERT(mutex_owned(&rnd_global.lock));
+
+       if (__predict_true(rnd_initial_entropy))
+               return;
+       pool_entropy = rndpool_get_entropy_count(&rnd_global.pool);
+       if (pool_entropy > RND_ENTROPY_THRESHOLD * NBBY) {
+               rnd_printf_verbose("rnd: have initial entropy (%zu)\n",
+                   pool_entropy);
+               rnd_initial_entropy = 1;
+       }
+}
+
+/*
  * initialize the global random pool for our use.
  * rnd_init() must be called very early on in the boot process, so
  * the pool is ready for other devices to attach as sources.
@@ -566,11 +568,8 @@
                rndpool_add_data(&rnd_global.pool, boot_rsp->data,
                    sizeof(boot_rsp->data),
                    MIN(boot_rsp->entropy, RND_POOLBITS / 2));
-               if (rndpool_get_entropy_count(&rnd_global.pool) >
-                   RND_ENTROPY_THRESHOLD * 8) {
-                       rnd_initial_entropy = 1;
-               }
-                mutex_spin_exit(&rnd_global.lock);
+               rnd_entropy_added();
+               mutex_spin_exit(&rnd_global.lock);
                rnd_printf("rnd: seeded with %d bits\n",
                    MIN(boot_rsp->entropy, RND_POOLBITS / 2));
                memset(boot_rsp, 0, sizeof(*boot_rsp));
@@ -1095,6 +1094,7 @@
 skip:          SIMPLEQ_INSERT_TAIL(&df_samples, sample, next);
        }
        rndpool_set_entropy_count(&rnd_global.pool, pool_entropy);
+       rnd_entropy_added();
        mutex_spin_exit(&rnd_global.lock);
 
        /*
@@ -1607,6 +1607,7 @@
                        mutex_spin_enter(&rnd_global.lock);
                        rndpool_add_data(&rnd_global.pool, rnddata->data,
                                         rnddata->len, estimate);
+                       rnd_entropy_added();
                        mutex_spin_exit(&rnd_global.lock);
 
                        rnd_wakeup_readers();