Move key_slot_mutex to threading.h

Make this a global mutex so that we don't have to init and free it.
Also rename the mutex to follow the convention

Signed-off-by: Ryan Everett <ryan.everett@arm.com>

include/mbedtls/threading.h

@@ -100,6 +100,20 @@ extern mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex;
 extern mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex;
 #endif /* MBEDTLS_HAVE_TIME_DATE && !MBEDTLS_PLATFORM_GMTIME_R_ALT */
 
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+/*
+ * A mutex used to make the PSA subsystem thread safe.
+ *
+ * key_slot_mutex protects the registered_readers and
+ * state variable for all key slots in &global_data.key_slots.
+ *
+ * This mutex must be held when any read from or write to a state or
+ * registered_readers field is performed, i.e. when calling functions:
+ * psa_key_slot_state_transition(), psa_register_read(), psa_unregister_read(),
+ * psa_key_slot_has_readers() and psa_wipe_key_slot(). */
+extern mbedtls_threading_mutex_t mbedtls_threading_key_slot_mutex;
+#endif
+
 #endif /* MBEDTLS_THREADING_C */
 
 #ifdef __cplusplus

library/psa_crypto_slot_management.c

@@ -30,20 +30,6 @@
 typedef struct {
     psa_key_slot_t key_slots[MBEDTLS_PSA_KEY_SLOT_COUNT];
     uint8_t key_slots_initialized;
-
-#if defined(MBEDTLS_THREADING_C)
-    /*
-     * A mutex used to make the PSA subsystem thread safe.
-     *
-     * key_slot_mutex protects key_slots[i].registered_readers and
-     * key_slots[i].state for all valid i.
-     *
-     * This mutex must be held when any read from or write to a state or
-     * registered_readers field is performed, i.e. when calling functions:
-     * psa_key_slot_state_transition, psa_register_read, psa_unregister_read,
-     * psa_key_slot_has_readers and psa_wipe_key_slot. */
-    mbedtls_threading_mutex_t MBEDTLS_PRIVATE(key_slot_mutex);
-#endif
 } psa_global_data_t;
 
 static psa_global_data_t global_data;
@@ -147,14 +133,7 @@ static psa_status_t psa_get_and_lock_key_slot_in_memory(
 
 psa_status_t psa_initialize_key_slots(void)
 {
-#if defined(MBEDTLS_THREADING_C)
-    /* Initialize the global key slot mutex. */
-    if (!global_data.key_slots_initialized) {
-        mbedtls_mutex_init(&global_data.key_slot_mutex);
-    }
-#endif
-
-    /* Program startup and psa_wipe_all_key_slots() both
+    /* Nothing to do: program startup and psa_wipe_all_key_slots() both
      * guarantee that the key slots are initialized to all-zero, which
      * means that all the key slots are in a valid, empty state. */
     global_data.key_slots_initialized = 1;
@@ -171,14 +150,6 @@ void psa_wipe_all_key_slots(void)
         slot->state = PSA_SLOT_PENDING_DELETION;
         (void) psa_wipe_key_slot(slot);
     }
-
-#if defined(MBEDTLS_THREADING_C)
-    /* Free the global key slot mutex. */
-    if (global_data.key_slots_initialized) {
-        mbedtls_mutex_free(&global_data.key_slot_mutex);
-    }
-#endif
-
     global_data.key_slots_initialized = 0;
 }
 

library/psa_crypto_slot_management.h

@@ -85,10 +85,6 @@ psa_status_t psa_get_and_lock_key_slot(mbedtls_svc_key_id_t key,
                                        psa_key_slot_t **p_slot);
 
 /** Initialize the key slot structures.
- * If multi-threading is enabled then initialize the key slot mutex.
- * This function is not thread-safe,
- * if called by competing threads the key slot mutex may be initialized
- * more than once.
  *
  * \retval #PSA_SUCCESS
  *         Currently this function always succeeds.
@@ -96,10 +92,6 @@ psa_status_t psa_get_and_lock_key_slot(mbedtls_svc_key_id_t key,
 psa_status_t psa_initialize_key_slots(void);
 
 /** Delete all data from key slots in memory.
- * If multi-threading is enabled then free the key slot mutex.
- * This function is not thread-safe,
- * if called by competing threads the key slot mutex may be freed
- * more than once.
  *
  * This does not affect persistent storage. */
 void psa_wipe_all_key_slots(void);
@@ -186,7 +178,7 @@ static inline psa_status_t psa_register_read(psa_key_slot_t *slot)
  * This function decrements the key slot registered reader counter by one.
  * If the state of the slot is PSA_SLOT_PENDING_DELETION,
  * and there is only one registered reader (the caller),
- * this function will call psa_wipe_slot().
+ * this function will call psa_wipe_key_slot().
  * If multi-threading is enabled, the caller must hold the
  * global key slot mutex.
  *

library/threading.c

@@ -148,6 +148,9 @@ void mbedtls_threading_set_alt(void (*mutex_init)(mbedtls_threading_mutex_t *),
 #if defined(THREADING_USE_GMTIME)
     mbedtls_mutex_init(&mbedtls_threading_gmtime_mutex);
 #endif
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+    mbedtls_mutext_init(&mbedtls_threading_key_slot_mutex);
+#endif
 }
 
 /*
@@ -161,6 +164,9 @@ void mbedtls_threading_free_alt(void)
 #if defined(THREADING_USE_GMTIME)
     mbedtls_mutex_free(&mbedtls_threading_gmtime_mutex);
 #endif
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+    mbedtls_mutex_free(&mbedtls_threading_key_slot_mutex);
+#endif
 }
 #endif /* MBEDTLS_THREADING_ALT */
 
@@ -176,5 +182,8 @@ mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex MUTEX_INIT;
 #if defined(THREADING_USE_GMTIME)
 mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex MUTEX_INIT;
 #endif
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+mbedtls_threading_mutex_t mbedtls_threading_key_slot_mutex MUTEX_INIT;
+#endif
 
 #endif /* MBEDTLS_THREADING_C */