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hwcrypto sha: Use spinlocks instead of semaphores for small state changes

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Significant performance improvement and smaller RAM footprint.
This commit is contained in:
Angus Gratton 2018-12-21 16:16:16 +11:00 committed by Angus Gratton
parent 24fab0b7a9
commit 94ed7b8298
2 changed files with 20 additions and 11 deletions
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27
components/esp32/hwcrypto/sha.c
View file

@ -27,7 +27,6 @@
#include <string.h> #include <string.h>
#include <stdio.h> #include <stdio.h>
#include <sys/lock.h>
#include <byteswap.h> #include <byteswap.h>
#include <assert.h> #include <assert.h>
@ -56,9 +55,9 @@ inline static uint32_t SHA_CONTINUE_REG(esp_sha_type sha_type) {
return SHA_1_CONTINUE_REG + sha_type * 0x10; return SHA_1_CONTINUE_REG + sha_type * 0x10;
} }
/* Single lock for SHA engine memory block /* Single spinlock for SHA engine memory block
*/ */
static _lock_t memory_block_lock; static portMUX_TYPE memory_block_lock = portMUX_INITIALIZER_UNLOCKED;
/* Binary semaphore managing the state of each concurrent SHA engine. /* Binary semaphore managing the state of each concurrent SHA engine.
@ -75,9 +74,9 @@ static SemaphoreHandle_t engine_states[3];
static uint8_t engines_in_use; static uint8_t engines_in_use;
/* Lock for engines_in_use counter /* Spinlock for engines_in_use counter
*/ */
static _lock_t engines_in_use_lock; static portMUX_TYPE engines_in_use_lock = portMUX_INITIALIZER_UNLOCKED;
/* Index into the engine_states array */ /* Index into the engine_states array */
inline static size_t sha_engine_index(esp_sha_type type) { inline static size_t sha_engine_index(esp_sha_type type) {
@ -123,12 +122,12 @@ inline static size_t block_length(esp_sha_type type) {
void esp_sha_lock_memory_block(void) void esp_sha_lock_memory_block(void)
{ {
_lock_acquire(&memory_block_lock); portENTER_CRITICAL(&memory_block_lock);
} }
void esp_sha_unlock_memory_block(void) void esp_sha_unlock_memory_block(void)
{ {
_lock_release(&memory_block_lock); portEXIT_CRITICAL(&memory_block_lock);
} }
static SemaphoreHandle_t sha_get_engine_state(esp_sha_type sha_type) static SemaphoreHandle_t sha_get_engine_state(esp_sha_type sha_type)
@ -177,7 +176,7 @@ static bool esp_sha_lock_engine_common(esp_sha_type sha_type, TickType_t ticks_t
return false; return false;
} }
_lock_acquire(&engines_in_use_lock); portENTER_CRITICAL(&engines_in_use_lock);
if (engines_in_use == 0) { if (engines_in_use == 0) {
/* Just locked first engine, /* Just locked first engine,
@ -191,7 +190,7 @@ static bool esp_sha_lock_engine_common(esp_sha_type sha_type, TickType_t ticks_t
engines_in_use++; engines_in_use++;
assert(engines_in_use <= 3); assert(engines_in_use <= 3);
_lock_release(&engines_in_use_lock); portEXIT_CRITICAL(&engines_in_use_lock);
return true; return true;
} }
@ -201,7 +200,7 @@ void esp_sha_unlock_engine(esp_sha_type sha_type)
{ {
SemaphoreHandle_t *engine_state = sha_get_engine_state(sha_type); SemaphoreHandle_t *engine_state = sha_get_engine_state(sha_type);
_lock_acquire(&engines_in_use_lock); portENTER_CRITICAL(&engines_in_use_lock);
engines_in_use--; engines_in_use--;
@ -211,7 +210,7 @@ void esp_sha_unlock_engine(esp_sha_type sha_type)
periph_module_disable(PERIPH_SHA_MODULE); periph_module_disable(PERIPH_SHA_MODULE);
} }
_lock_release(&engines_in_use_lock); portEXIT_CRITICAL(&engines_in_use_lock);
xSemaphoreGive(engine_state); xSemaphoreGive(engine_state);
} }
@ -238,6 +237,9 @@ void esp_sha_read_digest_state(esp_sha_type sha_type, void *digest_state)
} }
#endif #endif
// preemptively do this before entering the critical section, then re-check once in it
esp_sha_wait_idle();
esp_sha_lock_memory_block(); esp_sha_lock_memory_block();
esp_sha_wait_idle(); esp_sha_wait_idle();
@ -270,6 +272,9 @@ void esp_sha_block(esp_sha_type sha_type, const void *data_block, bool is_first_
} }
#endif #endif
// preemptively do this before entering the critical section, then re-check once in it
esp_sha_wait_idle();
esp_sha_lock_memory_block(); esp_sha_lock_memory_block();
esp_sha_wait_idle(); esp_sha_wait_idle();

4
components/esp32/include/hwcrypto/sha.h
View file

@ -166,6 +166,8 @@ void esp_sha_unlock_engine(esp_sha_type sha_type);
* while it is in use by the SHA engine. Caller should use esp_sha_wait_idle() * while it is in use by the SHA engine. Caller should use esp_sha_wait_idle()
* to ensure the SHA engine is not reading from the memory block in hardware. * to ensure the SHA engine is not reading from the memory block in hardware.
* *
* @note This function enters a critical section. Do not block while holding this lock.
*
* @note You do not need to lock the memory block before calling esp_sha_block() or esp_sha_read_digest_state(), these functions handle memory block locking internally. * @note You do not need to lock the memory block before calling esp_sha_block() or esp_sha_read_digest_state(), these functions handle memory block locking internally.
* *
* Call esp_sha_unlock_memory_block() when done. * Call esp_sha_unlock_memory_block() when done.
@ -177,6 +179,8 @@ void esp_sha_lock_memory_block(void);
* *
* Caller should have already locked a SHA engine before calling this function. * Caller should have already locked a SHA engine before calling this function.
* *
* This function releases the critical section entered by esp_sha_lock_memory_block().
*
* Call following esp_sha_lock_memory_block(). * Call following esp_sha_lock_memory_block().
*/ */
void esp_sha_unlock_memory_block(void); void esp_sha_unlock_memory_block(void);