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random: use the arch-specific rng in xfer_secondary_pool

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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@vger.kernel.org
This commit is contained in:
Theodore Ts'o 2012-07-05 10:21:01 -04:00
parent 7bf2357524
commit e6d4947b12
1 changed files with 16 additions and 9 deletions
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25
drivers/char/random.c
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@ -254,6 +254,7 @@
#include <linux/cryptohash.h>
#include <linux/fips.h>
#include <linux/ptrace.h>
#include <linux/kmemcheck.h>
#ifdef CONFIG_GENERIC_HARDIRQS
# include <linux/irq.h>
@ -702,11 +703,7 @@ 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), NULL);
@ -838,7 +835,11 @@ 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];
union {
__u32 tmp[OUTPUT_POOL_WORDS];
long hwrand[4];
} u;
int i;
if (r->pull && r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo->POOLBITS) {
@ -849,17 +850,23 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
/* pull at least as many as BYTES as wakeup BITS */
bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
/* but never more than the buffer size */
bytes = min_t(int, bytes, sizeof(tmp));
bytes = min_t(int, bytes, sizeof(u.tmp));
DEBUG_ENT("going to reseed %s with %d bits "
"(%d of %d requested)\n",
r->name, bytes * 8, nbytes * 8, r->entropy_count);
bytes = extract_entropy(r->pull, tmp, bytes,
bytes = extract_entropy(r->pull, u.tmp, bytes,
random_read_wakeup_thresh / 8, rsvd);
mix_pool_bytes(r, tmp, bytes, NULL);
mix_pool_bytes(r, u.tmp, bytes, NULL);
credit_entropy_bits(r, bytes*8);
}
kmemcheck_mark_initialized(&u.hwrand, sizeof(u.hwrand));
for (i = 0; i < 4; i++)
if (arch_get_random_long(&u.hwrand[i]))
break;
if (i)
mix_pool_bytes(r, &u.hwrand, sizeof(u.hwrand), 0);
}
/*