michaelh/zephyr
1
0
Fork 0
Code Releases Activity

subsys: random: xoroshiro128: Use SYS_INIT hook to initialize properly

Browse source 
Not only removes a branch during normal operation, but also ensures
that, by initializing at the PRE_KERNEL_2 stage, and granting
privileges to all threads to the semaphore, this code will work in
early boot situations and in user mode.

This assumes that entropy drivers will all initialize during
PRE_KERNEL_1 stage.  All in-tree drivers do that.

Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
This commit is contained in:
Leandro Pereira 2018-05-22 15:10:14 -07:00 • committed by Andrew Boie
commit fcc56e315f
1 changed files with 21 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

38
subsys/random/rand32_xoroshiro128.c
View file

@ -37,11 +37,12 @@
* output to fill s.
*/
#include <init.h>
#include <device.h>
#include <entropy.h>
#include <kernel.h>
static u64_t state[2];
static bool initialized;
K_SEM_DEFINE(state_sem, 1, 1);
@ -50,21 +51,20 @@ static inline u64_t rotl(const u64_t x, int k)
return (x << k) | (x >> (64 - k));
}
static bool xoroshiro128_initialize(void)
static int xoroshiro128_initialize(struct device *dev)
{
struct device *dev = device_get_binding(CONFIG_ENTROPY_NAME);
dev = device_get_binding(CONFIG_ENTROPY_NAME);
if (!dev) {
return false;
return -EINVAL;
}
if (entropy_get_entropy(dev, (uint8_t *)&state, sizeof(state)) < 0) {
return false;
return -EINVAL;
}
initialized = true;
k_object_access_all_grant(&state_sem);
return true;
return 0;
}
static u32_t xoroshiro128_next(void)
@ -84,22 +84,24 @@ u32_t sys_rand32_get(void)
{
u32_t ret;
k_sem_take(&state_sem, K_FOREVER);
if (unlikely(!initialized)) {
if (!xoroshiro128_initialize()) {
/* This should not happen, but beats returning 0
* when the PRNG couldn't be initialized.
if (k_sem_take(&state_sem, K_FOREVER) < 0) {
/* FIXME: with all threads having access to this semaphore,
* it's possible that they can corrupt state_sem in a way
* that k_sem_take will fail. This can be abused to
* generate numbers without using the xoroshiro128+ RNG.
*/
ret = k_cycle_get_32();
goto out;
}
return k_cycle_get_32();
}
ret = xoroshiro128_next();
out:
k_sem_give(&state_sem);
return ret;
}
/* In-tree entropy drivers will initialize in PRE_KERNEL_1; ensure that they're
* initialized properly before initializing ourselves.
*/
SYS_INIT(xoroshiro128_initialize, PRE_KERNEL_2,
CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);