lkml.org 
[lkml]   [2012]   [Jul]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 06/10] random: use the arch-specific rng in xfer_secondary_pool
Date
If the CPU supports a hardware random number generator, use it in
xfer_secondary_pool(), where it will significantly improve things and
where we can afford it.

Also, remove the use of the arch-specific rng in
add_timer_randomness(), since the call is significantly slower than
get_cycles(), and we're much better off using it in
xfer_secondary_pool() anyway.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
---
drivers/char/random.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 59ddcce..7f95f91 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -695,8 +695,8 @@ static struct timer_rand_state input_timer_state;
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
struct {
+ cycles_t cycles;
long jiffies;
- unsigned cycles;
unsigned num;
} sample;
long delta, delta2, delta3;
@@ -708,11 +708,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
goto out;

sample.jiffies = jiffies;
-
- /* Use arch random value, fall back to cycles */
- if (!arch_get_random_int(&sample.cycles))
- sample.cycles = get_cycles();
-
+ sample.cycles = get_cycles();
sample.num = num;
mix_pool_bytes(&input_pool, &sample, sizeof(sample));

@@ -831,7 +827,8 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
*/
static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
- __u32 tmp[OUTPUT_POOL_WORDS];
+ __u32 tmp[OUTPUT_POOL_WORDS];
+ int i, hwrand[4];

if (r->pull && r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo->POOLBITS) {
@@ -853,6 +850,11 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
mix_pool_bytes(r, tmp, bytes);
credit_entropy_bits(r, bytes*8, 0);
}
+ for (i = 0; i < 4; i++)
+ if (arch_get_random_int(&hwrand[i]))
+ break;
+ if (i)
+ mix_pool_bytes(r, &hwrand, sizeof(hwrand));
}

/*
--
1.7.11.1.108.gb129051


\
 
 \ /
  Last update: 2012-07-05 21:01    [W:0.157 / U:5.308 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site