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hwrng: add per-device entropy derating

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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: Torsten Duwe <duwe@suse.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Torsten Duwe 2014-06-14 23:48:41 -04:00 committed by Theodore Ts'o
parent be4000bc46
commit 0f734e6e76
2 changed files with 13 additions and 1 deletions
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11
drivers/char/hw_random/core.c
View File

@ -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();

3
include/linux/hw_random.h
View File

@ -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;