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drivers/entropy: stm32: fix inter-core race condition

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On STM32WB and dual-core STM32H7 MCUs, the RNG peripheral is shared
between the cores and its access is protected by a hardware semaphore.
Locking was not performed in the current entropy driver, leading to a
race condition when multiple cores concurrently used the RNG. This
commit implements the necessary logic for locking the HSEM during entropy
generation on multi-core STM32 MCUs. It also reconfigures the RNG in case
the configuration was changed by the other core, as this can happen e.g
on STM32WB MCUs.

Signed-off-by: Thomas Altenbach <taltenbach@witekio.com>
This commit is contained in:
Thomas Altenbach 2022-04-16 03:48:23 +02:00 • committed by Maureen Helm
commit cc51031445
2 changed files with 210 additions and 80 deletions
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258
drivers/entropy/entropy_stm32.c
View file

@ -83,6 +83,8 @@ struct entropy_stm32_rng_dev_data {
const struct device *clock;
struct k_sem sem_lock;
struct k_sem sem_sync;
struct k_work filling_work;
bool filling_pools;
RNG_POOL_DEFINE(isr, CONFIG_ENTROPY_STM32_ISR_POOL_SIZE);
RNG_POOL_DEFINE(thr, CONFIG_ENTROPY_STM32_THR_POOL_SIZE);
@ -97,6 +99,42 @@ static struct entropy_stm32_rng_dev_data entropy_stm32_rng_data = {
.rng = (RNG_TypeDef *)DT_INST_REG_ADDR(0),
};
static void configure_rng(void)
{
RNG_TypeDef *rng = entropy_stm32_rng_data.rng;
#if DT_INST_NODE_HAS_PROP(0, health_test_config)
#if DT_INST_NODE_HAS_PROP(0, health_test_magic)
/* Write Magic number before writing configuration
* Not all stm32 series have a Magic number
*/
LL_RNG_SetHealthConfig(rng, DT_INST_PROP(0, health_test_magic));
#endif
/* Write RNG HTCR configuration */
LL_RNG_SetHealthConfig(rng, DT_INST_PROP(0, health_test_config));
#endif
LL_RNG_Enable(rng);
LL_RNG_EnableIT(rng);
}
static void acquire_rng(void)
{
#if defined(CONFIG_SOC_SERIES_STM32WBX) || defined(CONFIG_STM32H7_DUAL_CORE)
/* Lock the RNG to prevent concurrent access */
z_stm32_hsem_lock(CFG_HW_RNG_SEMID, HSEM_LOCK_WAIT_FOREVER);
/* RNG configuration could have been changed by the other core */
configure_rng();
#endif /* CONFIG_SOC_SERIES_STM32WBX || CONFIG_STM32H7_DUAL_CORE */
}
static void release_rng(void)
{
#if defined(CONFIG_SOC_SERIES_STM32WBX) || defined(CONFIG_STM32H7_DUAL_CORE)
z_stm32_hsem_unlock(CFG_HW_RNG_SEMID);
#endif /* CONFIG_SOC_SERIES_STM32WBX || CONFIG_STM32H7_DUAL_CORE */
}
static int entropy_stm32_got_error(RNG_TypeDef *rng)
{
__ASSERT_NO_MSG(rng != NULL);
@ -191,6 +229,108 @@ out:
return retval;
}
static uint16_t generate_from_isr(uint8_t *buf, uint16_t len)
{
uint16_t remaining_len = len;
__ASSERT_NO_MSG(!irq_is_enabled(IRQN));
#if defined(CONFIG_SOC_SERIES_STM32WBX) || defined(CONFIG_STM32H7_DUAL_CORE)
__ASSERT_NO_MSG(z_stm32_hsem_is_owned(CFG_HW_RNG_SEMID));
#endif /* CONFIG_SOC_SERIES_STM32WBX || CONFIG_STM32H7_DUAL_CORE */
/* do not proceed if a Seed error occurred */
if (LL_RNG_IsActiveFlag_SECS(entropy_stm32_rng_data.rng) ||
LL_RNG_IsActiveFlag_SEIS(entropy_stm32_rng_data.rng)) {
(void)random_byte_get(); /* this will recover the error */
return 0; /* return cnt is null : no random data available */
}
/* Clear NVIC pending bit. This ensures that a subsequent
* RNG event will set the Cortex-M single-bit event register
* to 1 (the bit is set when NVIC pending IRQ status is
* changed from 0 to 1)
*/
NVIC_ClearPendingIRQ(IRQN);
do {
int byte;
while (LL_RNG_IsActiveFlag_DRDY(
entropy_stm32_rng_data.rng) != 1) {
/*
* To guarantee waking up from the event, the
* SEV-On-Pend feature must be enabled (enabled
* during ARCH initialization).
*
* DSB is recommended by spec before WFE (to
* guarantee completion of memory transactions)
*/
__DSB();
__WFE();
__SEV();
__WFE();
}
byte = random_byte_get();
NVIC_ClearPendingIRQ(IRQN);
if (byte < 0) {
continue;
}
buf[--remaining_len] = byte;
} while (remaining_len);
return len;
}
static int start_pool_filling(bool wait)
{
unsigned int key;
bool already_filling;
key = irq_lock();
#if defined(CONFIG_SOC_SERIES_STM32WBX) || defined(CONFIG_STM32H7_DUAL_CORE)
/* In non-blocking mode, return immediately if the RNG is not available */
if (!wait && z_stm32_hsem_try_lock(CFG_HW_RNG_SEMID) != 0) {
irq_unlock(key);
return -EAGAIN;
}
#else
ARG_UNUSED(wait);
#endif /* CONFIG_SOC_SERIES_STM32WBX || CONFIG_STM32H7_DUAL_CORE */
already_filling = entropy_stm32_rng_data.filling_pools;
entropy_stm32_rng_data.filling_pools = true;
irq_unlock(key);
if (unlikely(already_filling)) {
return 0;
}
/* Prevent the clocks to be stopped during the duration the rng pool is
* being populated. The ISR will release the constraint again when the
* rng pool is filled.
*/
pm_policy_state_lock_get(PM_STATE_SUSPEND_TO_IDLE, PM_ALL_SUBSTATES);
acquire_rng();
irq_enable(IRQN);
return 0;
}
static void pool_filling_work_handler(struct k_work *work)
{
if (start_pool_filling(false) != 0) {
/* RNG could not be acquired, try again */
k_work_submit(work);
}
}
#pragma GCC push_options
#if defined(CONFIG_BT_CTLR_FAST_ENC)
#pragma GCC optimize ("Ofast")
@ -244,10 +384,17 @@ static uint16_t rng_pool_get(struct rng_pool *rngp, uint8_t *buf, uint16_t len)
len = dst - buf;
available = available - len;
if ((available <= rngp->threshold)
&& !LL_RNG_IsEnabledIT(entropy_stm32_rng_data.rng)) {
pm_policy_state_lock_get(PM_STATE_SUSPEND_TO_IDLE, PM_ALL_SUBSTATES);
LL_RNG_EnableIT(entropy_stm32_rng_data.rng);
if (available <= rngp->threshold) {
/*
* Avoid starting pool filling from ISR as it might require
* blocking if RNG is not available and a race condition could
* also occur if this ISR has interrupted the RNG ISR.
*/
if (k_is_in_isr()) {
k_work_submit(&entropy_stm32_rng_data.filling_work);
} else {
start_pool_filling(true);
}
}
return len;
@ -299,8 +446,10 @@ static void stm32_rng_isr(const void *arg)
(struct rng_pool *)(entropy_stm32_rng_data.thr),
byte);
if (ret < 0) {
LL_RNG_DisableIT(entropy_stm32_rng_data.rng);
irq_disable(IRQN);
release_rng();
pm_policy_state_lock_put(PM_STATE_SUSPEND_TO_IDLE, PM_ALL_SUBSTATES);
entropy_stm32_rng_data.filling_pools = false;
}
k_sem_give(&entropy_stm32_rng_data.sem_sync);
@ -321,14 +470,14 @@ static int entropy_stm32_rng_get_entropy(const struct device *dev,
bytes = rng_pool_get(
(struct rng_pool *)(entropy_stm32_rng_data.thr),
buf, len);
k_sem_give(&entropy_stm32_rng_data.sem_lock);
if (bytes == 0U) {
/* Pool is empty: Sleep until next interrupt. */
k_sem_take(&entropy_stm32_rng_data.sem_sync, K_FOREVER);
continue;
}
k_sem_give(&entropy_stm32_rng_data.sem_lock);
len -= bytes;
buf += bytes;
}
@ -337,9 +486,9 @@ static int entropy_stm32_rng_get_entropy(const struct device *dev,
}
static int entropy_stm32_rng_get_entropy_isr(const struct device *dev,
uint8_t *buf,
uint16_t len,
uint32_t flags)
uint8_t *buf,
uint16_t len,
uint32_t flags)
{
uint16_t cnt = len;
@ -355,60 +504,23 @@ static int entropy_stm32_rng_get_entropy_isr(const struct device *dev,
if (len) {
unsigned int key;
int irq_enabled;
bool rng_already_acquired;
key = irq_lock();
irq_enabled = irq_is_enabled(IRQN);
irq_disable(IRQN);
irq_unlock(key);
/* do not proceed if a Seed error occurred */
if (LL_RNG_IsActiveFlag_SECS(entropy_stm32_rng_data.rng) ||
LL_RNG_IsActiveFlag_SEIS(entropy_stm32_rng_data.rng)) {
rng_already_acquired = z_stm32_hsem_is_owned(CFG_HW_RNG_SEMID);
acquire_rng();
(void)random_byte_get(); /* this will recover the error */
/* restore irq as we enter */
if (irq_enabled) {
irq_enable(IRQN);
}
return 0; /* return cnt is null : no random data available */
cnt = generate_from_isr(buf, len);
/* Restore the state of the RNG lock and IRQ */
if (!rng_already_acquired) {
release_rng();
}
/* Clear NVIC pending bit. This ensures that a subsequent
* RNG event will set the Cortex-M single-bit event register
* to 1 (the bit is set when NVIC pending IRQ status is
* changed from 0 to 1)
*/
NVIC_ClearPendingIRQ(IRQN);
do {
int byte;
while (LL_RNG_IsActiveFlag_DRDY(
entropy_stm32_rng_data.rng) != 1) {
/*
* To guarantee waking up from the event, the
* SEV-On-Pend feature must be enabled (enabled
* during ARCH initialization).
*
* DSB is recommended by spec before WFE (to
* guarantee completion of memory transactions)
*/
__DSB();
__WFE();
__SEV();
__WFE();
}
byte = random_byte_get();
NVIC_ClearPendingIRQ(IRQN);
if (byte < 0) {
continue;
}
buf[--len] = byte;
} while (len);
if (irq_enabled) {
irq_enable(IRQN);
}
@ -496,36 +608,14 @@ static int entropy_stm32_rng_init(const struct device *dev)
(clock_control_subsys_t *)&dev_cfg->pclken);
__ASSERT_NO_MSG(res == 0);
#if DT_INST_NODE_HAS_PROP(0, health_test_config)
#if DT_INST_NODE_HAS_PROP(0, health_test_magic)
/* Write Magic number before writing configuration
* Not all stm32 series have a Magic number
*/
LL_RNG_SetHealthConfig(dev_data->rng, DT_INST_PROP(0, health_test_magic));
#endif
/* Write RNG HTCR configuration */
LL_RNG_SetHealthConfig(dev_data->rng, DT_INST_PROP(0, health_test_config));
#endif
/* Prevent the clocks to be stopped during the duration the
* rng pool is being populated. The ISR will release the constraint again
* when the rng pool is filled.
*/
pm_policy_state_lock_get(PM_STATE_SUSPEND_TO_IDLE, PM_ALL_SUBSTATES);
LL_RNG_EnableIT(dev_data->rng);
LL_RNG_Enable(dev_data->rng);
/* Locking semaphore initialized to 1 (unlocked) */
k_sem_init(&dev_data->sem_lock, 1, 1);
/* Synching semaphore */
k_sem_init(&dev_data->sem_sync, 0, 1);
k_work_init(&dev_data->filling_work, pool_filling_work_handler);
rng_pool_init((struct rng_pool *)(dev_data->thr),
CONFIG_ENTROPY_STM32_THR_POOL_SIZE,
CONFIG_ENTROPY_STM32_THR_THRESHOLD);
@ -534,7 +624,15 @@ static int entropy_stm32_rng_init(const struct device *dev)
CONFIG_ENTROPY_STM32_ISR_THRESHOLD);
IRQ_CONNECT(IRQN, IRQ_PRIO, stm32_rng_isr, &entropy_stm32_rng_data, 0);
irq_enable(IRQN);
#if !defined(CONFIG_SOC_SERIES_STM32WBX) && !defined(CONFIG_STM32H7_DUAL_CORE)
/* For multi-core MCUs, RNG configuration is automatically performed
* after acquiring the RNG in start_pool_filling()
*/
configure_rng();
#endif /* !CONFIG_SOC_SERIES_STM32WBX && !CONFIG_STM32H7_DUAL_CORE */
start_pool_filling(true);
return 0;
}