Clarify which unregister operation needs to be used
Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 43b597c..07edd0a 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -909,8 +909,13 @@
* into a key slot if not already done.
*
* On success, the returned key slot has been registered for reading.
- * It is the responsibility of the caller to call psa_unregister_read(slot)
- * when they have finished reading the contents of the slot.
+ * It is the responsibility of the caller to then unregister
+ * once they have finished reading the contents of the slot.
+ * The caller unregisters by calling psa_unregister_read() or
+ * psa_unregister_read_under_mutex(). psa_unregister_read() must be called
+ * if and only if the caller already holds the global key slot mutex
+ * (when mutexes are enabled). psa_unregister_read_under_mutex() encapsulates
+ * the unregister with mutex lock and unlock operations.
*/
static psa_status_t psa_get_and_lock_key_slot_with_policy(
mbedtls_svc_key_id_t key,
@@ -970,8 +975,13 @@
* for a cryptographic operation.
*
* On success, the returned key slot has been registered for reading.
- * It is the responsibility of the caller to call psa_unregister_read(slot)
- * when they have finished reading the contents of the slot.
+ * It is the responsibility of the caller to then unregister
+ * once they have finished reading the contents of the slot.
+ * The caller unregisters by calling psa_unregister_read() or
+ * psa_unregister_read_under_mutex(). psa_unregister_read() must be called
+ * if and only if the caller already holds the global key slot mutex
+ * (when mutexes are enabled). psa_unregister_read_under_mutex() encapsulates
+ * psa_unregister_read() with mutex lock and unlock operations.
*/
static psa_status_t psa_get_and_lock_transparent_key_slot_with_policy(
mbedtls_svc_key_id_t key,
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index dc376d7..0d7322c 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -89,7 +89,9 @@
* A function must call psa_register_read(slot) before reading the current
* contents of the slot for an operation.
* They then must call psa_unregister_read(slot) once they have finished
- * reading the current contents of the slot.
+ * reading the current contents of the slot. If the key slot mutex is not
+ * held (when mutexes are enabled), this call must be done via a call to
+ * psa_unregister_read_under_mutex(slot).
* A function must call psa_key_slot_has_readers(slot) to check if
* the slot is in use for reading.
*