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Make xorshift128 re-entrant so that we do do have to suffer the overhad of serialization controls.

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This commit is contained in:
Gregory Nutt
2016-08-21 07:47:53 -06:00
parent 757023a909
commit 60b70f7dbb
4 changed files with 91 additions and 143 deletions
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drivers/dev_urandom.c
+34 -30
View File
@@ -67,21 +67,19 @@
#endif
#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
# define PRNG() xorshift128()
# define PRNG() do_xorshift128()
#else /* CONFIG_DEV_URANDOM_CONGRUENTIAL */
# define PRNG() congruential()
# define PRNG() do_congruential()
#endif
/****************************************************************************
* Private Types
****************************************************************************/
struct xorshift128_state_s
union xorshift128_state_u
{
uint32_t x;
uint32_t y;
uint32_t z;
uint32_t w;
struct xorshift128_state_s state;
uint8_t u[16];
};
/****************************************************************************
@@ -119,16 +117,31 @@ static const struct file_operations g_urand_fops =
#endif
};
#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
static union xorshift128_state_u g_prng;
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: congruential
* Name: do_xorshift128
****************************************************************************/
#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
static inline uint32_t do_xorshift128(void)
{
return xorshift128(&g_prng.state);
}
#endif
/****************************************************************************
* Name: do_congruential
****************************************************************************/
#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
static uint32_t congruential(void)
static inline uint32_t do_congruential(void)
{
/* REVISIT: We could probably generate a 32-bit value with a single
* call to nrand().
@@ -211,26 +224,14 @@ static ssize_t devurand_write(FAR struct file *filep, FAR const char *buffer,
#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
unsigned int seed = 0;
if (len < sizeof(unsigned int))
{
return -ERANGE;
}
memcpy(&seed, buffer, sizeof(unsigned int));
len = min(len, sizeof(unsigned int));
memcpy(&seed, buffer, len);
srand(seed);
return sizeof(unsigned int);
return len;
#else
struct xorshift128_state_s seed;
if (len < sizeof(struct xorshift128_state_s))
{
return -ERANGE;
}
memcpy(&seed, buffer, sizeof(struct xorshift128_state_s));
xorshift128_seed(seed.w, seed.x, seed.y, seed.z);
return sizeof(struct xorshift128_state_s);
len = min(len, sizeof(g_prng.u));
memcpy(&g_prng.u, buffer, len);
return len;
#endif
}
@@ -269,12 +270,15 @@ static int devurand_poll(FAR struct file *filep, FAR struct pollfd *fds,
void devurandom_register(void)
{
/* Seed the PRNG */
#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
srand(10197);
#else
/* Seed the PRNG */
xorshift128_seed(97, 101, 97 << 17, 101 << 25);
g_prng.state.w = 97;
g_prng.state.x = 101;
g_prng.state.y = g_prng.state.w << 17;
g_prng.state.z = g_prng.state.x << 25;
#endif
(void)register_driver("/dev/urandom", &g_urand_fops, 0666, NULL);
include/nuttx/lib/xorshift128.h
+31 -19
View File
@@ -46,6 +46,28 @@
#include <nuttx/config.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Default XorShift128 state initializer */
#define XORSHIFT128_INITIALIZER { 97, 101, 97 << 17, 101 << 25 }
/****************************************************************************
* Public Types
****************************************************************************/
/* Provides the state of the XorShift128 PRNG */
struct xorshift128_state_s
{
uint32_t x;
uint32_t y;
uint32_t z;
uint32_t w;
};
/****************************************************************************
* Public Function Prototypes
****************************************************************************/
@@ -58,37 +80,27 @@ extern "C"
#define EXTERN extern
#endif
/****************************************************************************
* Name: xorshift128_seed
*
* Description:
* Seed the XorShift128 PRNG
*
* Input Parameters:
* w, x, y, z: Values for XorShift128 generation state.
*
* Returned Value:
* No
*
****************************************************************************/
void xorshift128_seed(uint32_t w, uint32_t x, uint32_t y, uint32_t z);
/****************************************************************************
* Name: xorshift128
*
* Description:
* Generate one 32-bit pseudo-random number
* Generate one 32-bit pseudo-random number.
*
* NOTE: Because the PRNG state is passed as a parameter, this function is
* fully re-entrant and may be called from an interrupt handler.
*
* The downside to this is that users of the PRNG might not get as much
* entropy as if it were a common state structure.
*
* Input Parameters:
* None
* state - The current XorShift128 state.
*
* Returned Value:
* The generated pseudo-random number
*
****************************************************************************/
uint32_t xorshift128(void);
uint32_t xorshift128(FAR struct xorshift128_state_s *state);
#undef EXTERN
#ifdef __cplusplus
libc/misc/lib_xorshift128.c
+20 -92
View File
@@ -43,10 +43,11 @@
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <sched.h>
#include <assert.h>
#include <nuttx/irq.h>
#include <nuttx/lib/xorshift128.h>
/****************************************************************************
* Private Types
@@ -56,119 +57,46 @@
# define CONFIG_CPULOAD_ONESHOT_ENTROPY 0
#endif
/****************************************************************************
* Private Types
****************************************************************************/
struct xorshift128_state_s
{
uint32_t x;
uint32_t y;
uint32_t z;
uint32_t w;
};
/****************************************************************************
* Private Data
****************************************************************************/
static struct xorshift128_state_s g_prng;
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: xorshift128_seed
*
* Description:
* Seed the XorShift128 PRNG
*
* Input Parameters:
* w, x, y, z: Values for XorShift128 generation state.
*
* Returned Value:
* No
*
****************************************************************************/
void xorshift128_seed(uint32_t w, uint32_t x, uint32_t y, uint32_t z)
{
/* With CONFIG_CPULOAD_ONESHOT_ENTROPY > 0, this PRNG could be called from
* the interrupt handling state (currently is not).
*/
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
irqstate_t flags;
flags = enter_critical_section();
#else
sched_lock();
#endif
/* Seed the PRNG */
g_prng.w = w;
g_prng.x = x;
g_prng.y = y;
g_prng.z = z;
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
leave_critical_section(flags);
#else
sched_unlock();
#endif
}
/****************************************************************************
* Name: xorshift128
*
* Description:
* Generate one 32-bit pseudo-random number
* Generate one 32-bit pseudo-random number.
*
* NOTE: Because the PRNG state is passed as a parameter, this function is
* fully re-entrant and may be called from an interrupt handler.
*
* The downside to this is that users of the PRNG might not get as much
* entropy as if it were a common state structure.
*
* Input Parameters:
* None
* state - The current XorShift128 state.
*
* Returned Value:
* The generated pseudo-random number
*
****************************************************************************/
uint32_t xorshift128(void)
uint32_t xorshift128(FAR struct xorshift128_state_s *state)
{
uint32_t ret;
uint32_t t;
/* With CONFIG_CPULOAD_ONESHOT_ENTROPY > 0, this PRNG will be called from
* the interrupt handling state.
*/
DEBUGASSERT(state != NULL);
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
irqstate_t flags;
flags = enter_critical_section();
#else
sched_lock();
#endif
t = g_prng.x;
t = state->x;
t ^= t << 11;
t ^= t >> 8;
g_prng.x = g_prng.y;
g_prng.y = g_prng.z;
g_prng.z = g_prng.w;
state->x = state->y;
state->y = state->z;
state->z = state->w;
g_prng.w ^= g_prng.w >> 19;
g_prng.w ^= t;
state->w ^= state->w >> 19;
state->w ^= t;
ret = g_prng.w;
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
leave_critical_section(flags);
#else
sched_unlock();
#endif
return ret;
return state->w;
}
sched/sched/sched_cpuload_oneshot.c
+6 -2
View File
@@ -91,6 +91,7 @@ struct sched_oneshot_s
{
FAR struct oneshot_lowerhalf_s *oneshot;
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
struct xorshift128_state_s prng;
int32_t maxdelay;
int32_t error;
#endif
@@ -153,7 +154,7 @@ static void sched_oneshot_start(void)
/* Add the random value in the range 0..(CPULOAD_ONESHOT_ENTRY - 1) */
entropy = xorshift128();
entropy = xorshift128(&g_sched_oneshot.prng);
usecs += (int32_t)(entropy & CPULOAD_ONESHOT_ENTROPY_MASK);
DEBUGASSERT(usecs > 0); /* Check for overflow to negative or zero */
@@ -272,7 +273,10 @@ void sched_oneshot_extclk(FAR struct oneshot_lowerhalf_s *lower)
/* Seed the PRNG */
xorshift128_seed(97, 101, 97 << 17, 101 << 25);
g_sched_oneshot.prng.w = 97;
g_sched_oneshot.prng.x = 101;
g_sched_oneshot.prng.y = g_sched_oneshot.prng.w << 17;
g_sched_oneshot.prng.z = g_sched_oneshot.prng.x << 25;
#endif
/* Then start the oneshot */