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Commit 0f734e6e authored by Torsten Duwe's avatar Torsten Duwe Committed by Theodore Ts'o
Browse files

hwrng: add per-device entropy derating 



This patch introduces a derating factor to struct hwrng for
the random bits going into the kernel input pool, and a common
default derating for drivers which do not specify one.

Signed-off-by: default avatarTorsten Duwe <duwe@suse.de>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent be4000bc

drivers/char/hw_random/core.c

+10 −1
Original line number Diff line number Diff line
@@ -56,11 +56,15 @@ static LIST_HEAD(rng_list); 
static DEFINE_MUTEX(rng_mutex);

static int data_avail;

static u8 *rng_buffer, *rng_fillbuf;

static unsigned short current_quality = 700; /* an arbitrary 70% */

static unsigned short current_quality;

static unsigned short default_quality; /* = 0; default to "off" */



module_param(current_quality, ushort, 0644);

MODULE_PARM_DESC(current_quality,

		 "current hwrng entropy estimation per mill");

module_param(default_quality, ushort, 0644);

MODULE_PARM_DESC(default_quality,

		 "default entropy content of hwrng per mill");



static void start_khwrngd(void);
@@ -79,6 +83,11 @@ static inline int hwrng_init(struct hwrng *rng) 
			return err;

	}



	current_quality = rng->quality ? : default_quality;

	current_quality &= 1023;



	if (current_quality == 0 && hwrng_fill)

		kthread_stop(hwrng_fill);

	if (current_quality > 0 && !hwrng_fill)

		start_khwrngd();

include/linux/hw_random.h

+3 −0
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 
 * @read:		New API. drivers can fill up to max bytes of data

 *			into the buffer. The buffer is aligned for any type.

 * @priv:		Private data, for use by the RNG driver.

 * @quality:		Estimation of true entropy in RNG's bitstream

 *			(per mill).

 */

struct hwrng {

	const char *name;
@@ -38,6 +40,7 @@ struct hwrng { 
	int (*data_read)(struct hwrng *rng, u32 *data);

	int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);

	unsigned long priv;

	unsigned short quality;



	/* internal. */

	struct list_head list;