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random: add_hwgenerator_randomness() for feeding entropy from devices

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This patch adds an interface to the random pool for feeding entropy
in-kernel.

Change-Id: Id9031d6b615877ea957ee2d2aba1f8150ec699b9
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Git-commit: c84dbf61a7
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
[sboyd@codeaurora.org: Bring in ENTROPY_BITS() define,
s/random_write_wakeup_bits/random_write_wakeup_thresh/, and pass
NULL to mix_pool_bytes last parameter]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Torsten Duwe 2014-06-14 23:38:36 -04:00 committed by followmsi
parent 00cffbf482
commit 65326fb405
2 changed files with 33 additions and 0 deletions
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31
drivers/char/random.c
View file

@ -250,6 +250,7 @@
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/percpu.h>
#include <linux/cryptohash.h>
#include <linux/fips.h>
@ -281,6 +282,16 @@
#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
/*
* To allow fractional bits to be tracked, the entropy_count field is
* denominated in units of 1/8th bits.
*
* 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
* credit_entropy_bits() needs to be 64 bits wide.
*/
#define ENTROPY_SHIFT 3
#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
/*
* The minimum number of bits of entropy before we wake up a read on
* /dev/random. Should be enough to do a significant reseed.
@ -1560,3 +1571,23 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
return 0;
return PAGE_ALIGN(get_random_int() % range + start);
}
/* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
*/
void add_hwgenerator_randomness(const char *buffer, size_t count,
size_t entropy)
{
struct entropy_store *poolp = &input_pool;
/* Suspend writing if we're above the trickle threshold.
* We'll be woken up again once below random_write_wakeup_thresh,
* or when the calling thread is about to terminate.
*/
wait_event_interruptible(random_write_wait, kthread_should_stop() ||
ENTROPY_BITS(poolp) <= random_write_wakeup_thresh);
mix_pool_bytes(poolp, buffer, count, NULL);
credit_entropy_bits(poolp, entropy);
}
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);

2
include/linux/hw_random.h
View file

@ -47,5 +47,7 @@ struct hwrng {
extern int hwrng_register(struct hwrng *rng);
/** Unregister a Hardware Random Number Generator driver. */
extern void hwrng_unregister(struct hwrng *rng);
/** Feed random bits into the pool. */
extern void add_hwgenerator_randomness(const char *buffer, size_t count, size_t entropy);
#endif /* LINUX_HWRANDOM_H_ */