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Subject[PATCH 7/12] random pt3: Reseed pointer in pool struct
Date
Put pointer to reseed pool in pool struct and automatically pull
entropy from it if it is set. This lets us remove the
EXTRACT_SECONDARY flag.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rnd/drivers/char/random.c
===================================================================
--- rnd.orig/drivers/char/random.c 2005-01-18 10:39:34.550137752 -0800
+++ rnd/drivers/char/random.c 2005-01-18 10:39:47.360504569 -0800
@@ -406,12 +406,14 @@
*
**********************************************************************/

+struct entropy_store;
struct entropy_store {
/* mostly-read data: */
struct poolinfo *poolinfo;
__u32 *pool;
const char *name;
int limit;
+ struct entropy_store *pull;

/* read-write data: */
spinlock_t lock ____cacheline_aligned_in_smp;
@@ -436,6 +438,7 @@
.poolinfo = &poolinfo_table[1],
.name = "blocking",
.limit = 1,
+ .pull = &input_pool,
.lock = SPIN_LOCK_UNLOCKED,
.pool = blocking_pool_data
};
@@ -443,6 +446,7 @@
static struct entropy_store nonblocking_pool = {
.poolinfo = &poolinfo_table[1],
.name = "nonblocking",
+ .pull = &input_pool,
.lock = SPIN_LOCK_UNLOCKED,
.pool = nonblocking_pool_data
};
@@ -1180,7 +1184,6 @@
*********************************************************************/

#define EXTRACT_ENTROPY_USER 1
-#define EXTRACT_ENTROPY_SECONDARY 2
#define TMP_BUF_SIZE (HASH_BUFFER_SIZE + HASH_EXTRA_SIZE)
#define SEC_XFER_SIZE (TMP_BUF_SIZE*4)

@@ -1195,7 +1198,7 @@
static inline void xfer_secondary_pool(struct entropy_store *r,
size_t nbytes, __u32 *tmp)
{
- if (r->entropy_count < nbytes * 8 &&
+ if (r->pull && r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo->POOLBITS) {
int bytes = max_t(int, random_read_wakeup_thresh / 8,
min_t(int, nbytes, TMP_BUF_SIZE));
@@ -1205,7 +1208,7 @@
"(%d of %d requested)\n",
r->name, bytes * 8, nbytes * 8, r->entropy_count);

- bytes=extract_entropy(&input_pool, tmp, bytes,
+ bytes=extract_entropy(r->pull, tmp, bytes,
random_read_wakeup_thresh / 8, rsvd, 0);
add_entropy_words(r, tmp, bytes);
credit_entropy_store(r, bytes*8);
@@ -1219,10 +1222,6 @@
* number of bytes that are actually obtained. If the EXTRACT_ENTROPY_USER
* flag is given, then the buf pointer is assumed to be in user space.
*
- * If the EXTRACT_ENTROPY_SECONDARY flag is given, then we are actually
- * extracting entropy from the secondary pool, and can refill from the
- * primary pool if needed.
- *
* The min parameter specifies the minimum amount we can pull before
* failing to avoid races that defeat catastrophic reseeding while the
* reserved parameter indicates how much entropy we must leave in the
@@ -1242,8 +1241,7 @@
if (r->entropy_count > r->poolinfo->POOLBITS)
r->entropy_count = r->poolinfo->POOLBITS;

- if (flags & EXTRACT_ENTROPY_SECONDARY)
- xfer_secondary_pool(r, nbytes, tmp);
+ xfer_secondary_pool(r, nbytes, tmp);

/* Hold lock while accounting */
spin_lock_irqsave(&r->lock, cpuflags);
@@ -1358,8 +1356,7 @@
*/
void get_random_bytes(void *buf, int nbytes)
{
- extract_entropy(&nonblocking_pool, (char *) buf, nbytes, 0, 0,
- EXTRACT_ENTROPY_SECONDARY);
+ extract_entropy(&nonblocking_pool, (char *) buf, nbytes, 0, 0, 0);
}

EXPORT_SYMBOL(get_random_bytes);
@@ -1449,8 +1446,7 @@
DEBUG_ENT("reading %d bits\n", n*8);

n = extract_entropy(&blocking_pool, buf, n, 0, 0,
- EXTRACT_ENTROPY_USER |
- EXTRACT_ENTROPY_SECONDARY);
+ EXTRACT_ENTROPY_USER);

DEBUG_ENT("read got %d bits (%d still needed)\n",
n*8, (nbytes-n)*8);
-
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