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hwcrypto sha: Allow SHA contexts to be shared between tasks

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Previously, hardware SHA engine "locks" were mutex semaphores. This meant that the task which
started a particular SHA session (in hardware) needed to finalise that session, or an invalid
FreeRTOS state was created.

Replace with binary semaphore which can be shared between tasks.

Includes a unit test, but unit test doesn't crash even without this fix
(some other unknown condition is required).
This commit is contained in:
Angus Gratton 2018-12-21 15:37:57 +11:00 committed by Angus Gratton
parent 8c1d9e70b5
commit 36b65c8498
2 changed files with 123 additions and 46 deletions
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125
components/esp32/hwcrypto/sha.c
View file

@ -31,6 +31,9 @@
#include <byteswap.h>
#include <assert.h>
#include "freertos/FreeRTOS.h"
#include "freertos/semphr.h"
#include "hwcrypto/sha.h"
#include "rom/ets_sys.h"
#include "soc/dport_reg.h"
@ -57,21 +60,26 @@ inline static uint32_t SHA_CONTINUE_REG(esp_sha_type sha_type) {
*/
static _lock_t memory_block_lock;
typedef struct {
_lock_t lock;
bool in_use;
} sha_engine_state;
/* Pointer to state of each concurrent SHA engine.
/* Binary semaphore managing the state of each concurrent SHA engine.
Available = noone is using this SHA engine
Taken = a SHA session is running on this SHA engine
Indexes:
0 = SHA1
1 = SHA2_256
2 = SHA2_384 or SHA2_512
*/
static sha_engine_state engine_states[3];
static SemaphoreHandle_t engine_states[3];
/* Index into the sha_engine_state array */
static uint8_t engines_in_use;
/* Lock for engines_in_use counter
*/
static _lock_t engines_in_use_lock;
/* Index into the engine_states array */
inline static size_t sha_engine_index(esp_sha_type type) {
switch(type) {
case SHA1:
@ -123,74 +131,89 @@ void esp_sha_unlock_memory_block(void)
_lock_release(&memory_block_lock);
}
/* Lock to hold when changing SHA engine state,
allows checking of sha_engines_all_idle()
*/
static _lock_t state_change_lock;
static SemaphoreHandle_t sha_get_engine_state(esp_sha_type sha_type)
{
unsigned idx = sha_engine_index(sha_type);
volatile SemaphoreHandle_t *engine = &engine_states[idx];
SemaphoreHandle_t result = *engine;
inline static bool sha_engines_all_idle() {
return !engine_states[0].in_use
&& !engine_states[1].in_use
&& !engine_states[2].in_use;
if (result == NULL) {
// Create a new semaphore for 'in use' flag
SemaphoreHandle_t new_engine = xSemaphoreCreateBinary();
assert(new_engine != NULL);
xSemaphoreGive(new_engine); // start available
// try to atomically set the previously NULL *engine to new_engine
uint32_t set_engine = (uint32_t)new_engine;
uxPortCompareSet((volatile uint32_t *)engine, 0, &set_engine);
if (set_engine != 0) { // we lost a race setting *engine
vSemaphoreDelete(new_engine);
}
result = *engine;
}
return result;
}
static void esp_sha_lock_engine_inner(sha_engine_state *engine);
static bool esp_sha_lock_engine_common(esp_sha_type sha_type, TickType_t ticks_to_wait);
bool esp_sha_try_lock_engine(esp_sha_type sha_type)
{
sha_engine_state *engine = &engine_states[sha_engine_index(sha_type)];
if(_lock_try_acquire(&engine->lock) != 0) {
/* This SHA engine is already in use */
return false;
} else {
esp_sha_lock_engine_inner(engine);
return true;
}
return esp_sha_lock_engine_common(sha_type, 0);
}
void esp_sha_lock_engine(esp_sha_type sha_type)
{
sha_engine_state *engine = &engine_states[sha_engine_index(sha_type)];
_lock_acquire(&engine->lock);
esp_sha_lock_engine_inner(engine);
esp_sha_lock_engine_common(sha_type, portMAX_DELAY);
}
static void esp_sha_lock_engine_inner(sha_engine_state *engine)
static bool esp_sha_lock_engine_common(esp_sha_type sha_type, TickType_t ticks_to_wait)
{
_lock_acquire(&state_change_lock);
SemaphoreHandle_t engine_state = sha_get_engine_state(sha_type);
BaseType_t result = xSemaphoreTake(engine_state, ticks_to_wait);
if (sha_engines_all_idle()) {
/* Enable SHA hardware */
if (result == pdFALSE) {
// failed to take semaphore
return false;
}
_lock_acquire(&engines_in_use_lock);
if (engines_in_use == 0) {
/* Just locked first engine,
so enable SHA hardware */
periph_module_enable(PERIPH_SHA_MODULE);
DPORT_STALL_OTHER_CPU_START();
ets_sha_enable();
DPORT_STALL_OTHER_CPU_END();
}
assert( !engine->in_use && "in_use flag should be cleared" );
engine->in_use = true;
engines_in_use++;
assert(engines_in_use <= 3);
_lock_release(&state_change_lock);
_lock_release(&engines_in_use_lock);
return true;
}
void esp_sha_unlock_engine(esp_sha_type sha_type)
{
sha_engine_state *engine = &engine_states[sha_engine_index(sha_type)];
SemaphoreHandle_t *engine_state = sha_get_engine_state(sha_type);
_lock_acquire(&state_change_lock);
_lock_acquire(&engines_in_use_lock);
assert( engine->in_use && "in_use flag should be set" );
engine->in_use = false;
engines_in_use--;
if (sha_engines_all_idle()) {
/* Disable SHA hardware */
if (engines_in_use == 0) {
/* About to release last engine, so
disable SHA hardware */
periph_module_disable(PERIPH_SHA_MODULE);
}
_lock_release(&state_change_lock);
_lock_release(&engines_in_use_lock);
_lock_release(&engine->lock);
xSemaphoreGive(engine_state);
}
void esp_sha_wait_idle(void)
@ -207,8 +230,13 @@ void esp_sha_wait_idle(void)
void esp_sha_read_digest_state(esp_sha_type sha_type, void *digest_state)
{
sha_engine_state *engine = &engine_states[sha_engine_index(sha_type)];
assert(engine->in_use && "SHA engine should be locked" );
#ifndef NDEBUG
{
SemaphoreHandle_t *engine_state = sha_get_engine_state(sha_type);
assert(uxSemaphoreGetCount(engine_state) == 0 &&
"SHA engine should be locked" );
}
#endif
esp_sha_lock_memory_block();
@ -234,8 +262,13 @@ void esp_sha_read_digest_state(esp_sha_type sha_type, void *digest_state)
void esp_sha_block(esp_sha_type sha_type, const void *data_block, bool is_first_block)
{
sha_engine_state *engine = &engine_states[sha_engine_index(sha_type)];
assert(engine->in_use && "SHA engine should be locked" );
#ifndef NDEBUG
{
SemaphoreHandle_t *engine_state = sha_get_engine_state(sha_type);
assert(uxSemaphoreGetCount(engine_state) == 0 &&
"SHA engine should be locked" );
}
#endif
esp_sha_lock_memory_block();

44
components/mbedtls/test/test_mbedtls_sha.c
View file

@ -255,3 +255,47 @@ TEST_CASE("mbedtls SHA256 clone", "[mbedtls]")
TEST_ASSERT_EQUAL(0, mbedtls_sha256_finish_ret(&clone, sha256));
TEST_ASSERT_EQUAL_MEMORY_MESSAGE(sha256_thousand_as, sha256, 32, "SHA256 cloned calculation");
}
typedef struct {
mbedtls_sha256_context ctx;
uint8_t result[32];
int ret;
bool done;
} finalise_sha_param_t;
static void tskFinaliseSha(void *v_param)
{
finalise_sha_param_t *param = (finalise_sha_param_t *)v_param;
for (int i = 0; i < 5; i++) {
TEST_ASSERT_EQUAL(0, mbedtls_sha256_update_ret(&param->ctx, one_hundred_as, 100));
}
param->ret = mbedtls_sha256_finish_ret(&param->ctx, param->result);
param->done = true;
vTaskDelete(NULL);
}
TEST_CASE("mbedtls SHA session passed between tasks" , "[mbedtls]")
{
finalise_sha_param_t param = { 0 };
mbedtls_sha256_init(&param.ctx);
TEST_ASSERT_EQUAL(0, mbedtls_sha256_starts_ret(&param.ctx, false));
for (int i = 0; i < 5; i++) {
TEST_ASSERT_EQUAL(0, mbedtls_sha256_update_ret(&param.ctx, one_hundred_as, 100));
}
// pass the SHA context off to a different task
//
// note: at the moment this doesn't crash even if a mutex semaphore is used as the
// engine lock, but it can crash...
xTaskCreate(tskFinaliseSha, "SHAFinalise", SHA_TASK_STACK_SIZE, &param, 3, NULL);
while (!param.done) {
vTaskDelay(1);
}
TEST_ASSERT_EQUAL(0, param.ret);
TEST_ASSERT_EQUAL_MEMORY_MESSAGE(sha256_thousand_as, param.result, 32, "SHA256 result from other task");
}