From: Ben Gras <ben@minix3.org>
Date: Sun, 5 May 2013 23:52:34 +0000 (+0000)
Subject: kernel, random: adaptive entropy gathering
X-Git-Tag: v3.3.0~993
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/zlib_tech.html?a=commitdiff_plain;h=717425320fdbeac66e46b7248c0c452f184d621e;p=minix.git

kernel, random: adaptive entropy gathering

kernel: stop gathering timestamps once the bin is full per interrupt

random: once seeded, retrieve new entropy at a lower rate

Change-Id: I4ce6081d39274728d82c6889686d1650cfd5fc2e
---

diff --git a/drivers/random/main.c b/drivers/random/main.c
index f2a65db8c..18ed36d34 100644
--- a/drivers/random/main.c
+++ b/drivers/random/main.c
@@ -273,6 +273,7 @@ static void r_random(message *UNUSED(m_ptr))
   static struct k_randomness_bin krandom_bin;
   u32_t hi, lo;
   rand_t r;
+  int nextperiod = random_isseeded() ? KRANDOM_PERIOD*500 : KRANDOM_PERIOD;
 
   bin = (bin+1) % RANDOM_SOURCES;
 
@@ -285,7 +286,7 @@ static void r_random(message *UNUSED(m_ptr))
   random_update(RND_TIMING, &r, 1);
 
   /* Schedule new alarm for next m_random call. */
-  if (OK != (s=sys_setalarm(KRANDOM_PERIOD, 0)))
+  if (OK != (s=sys_setalarm(nextperiod, 0)))
   	printf("RANDOM: sys_setalarm failed: %d\n", s);
 }
 
diff --git a/lib/libsys/arch/i386/get_randomness.c b/lib/libsys/arch/i386/get_randomness.c
index 720f67472..0a7f9e9d5 100644
--- a/lib/libsys/arch/i386/get_randomness.c
+++ b/lib/libsys/arch/i386/get_randomness.c
@@ -22,6 +22,7 @@ int source;
   unsigned long tsc_high, tsc_low;
  
   source %= RANDOM_SOURCES;
+  if (rand->bin[source].r_size >= RANDOM_ELEMENTS) return;
   r_next= rand->bin[source].r_next;  
   read_tsc((u32_t *) &tsc_high, (u32_t *) &tsc_low);
   rand->bin[source].r_buf[r_next] = tsc_low;