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Microoptimizations when MBEDTLS_PSA_KEY_STORE_DYNAMIC is disabled

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Compensate some of the code size increase from implementing dynamic key slots.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2024-06-10 15:41:38 +02:00
parent e8199f574c
commit a81282ce30
1 changed files with 17 additions and 10 deletions
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27
library/psa_crypto_slot_management.c
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@ -424,16 +424,24 @@ void psa_wipe_all_key_slots(void)
#endif /* MBEDTLS_PSA_KEY_STORE_DYNAMIC */
for (size_t slot_idx = 0; slot_idx < key_slice_length(slice_idx); slot_idx++) {
psa_key_slot_t *slot = get_key_slot(slice_idx, slot_idx);
#if defined(MBEDTLS_PSA_KEY_STORE_DYNAMIC)
/* When MBEDTLS_PSA_KEY_STORE_DYNAMIC is disabled, calling
* psa_wipe_key_slot() on an unused slot is useless, but it
* happens to work (because we flip the state to PENDING_DELETION).
*
* When MBEDTLS_PSA_KEY_STORE_DYNAMIC is enabled,
* psa_wipe_key_slot() needs to have a valid slice_index
* field, but that value might not be correct in a
* free slot, so we must not call it.
*
* Bypass the call to psa_wipe_key_slot() if the slot is empty,
* but only if MBEDTLS_PSA_KEY_STORE_DYNAMIC is enabled, to save
* a few bytes of code size otherwise.
*/
if (slot->state == PSA_SLOT_EMPTY) {
/* Don't call psa_wipe_key_slot() on an already-empty slot.
* It rejects that case anyway, though we bypass it by setting
* the slot state to PENDING_DELETION.
* Also, when MBEDTLS_PSA_KEY_STORE_DYNAMIC is enabled,
* psa_wipe_key_slot() needs to have a valid slice_index
* field, but that value might not be correct in a
* free slot. */
continue;
}
#endif
slot->var.occupied.registered_readers = 1;
slot->state = PSA_SLOT_PENDING_DELETION;
(void) psa_wipe_key_slot(slot);
@ -560,12 +568,11 @@ psa_status_t psa_reserve_free_key_slot(psa_key_id_t *volatile_key_id,
goto error;
}
if (volatile_key_id != NULL) {
*volatile_key_id = 0;
#if defined(MBEDTLS_PSA_KEY_STORE_DYNAMIC)
if (volatile_key_id != NULL) {
return psa_allocate_volatile_key_slot(volatile_key_id, p_slot);
#endif /* MBEDTLS_PSA_KEY_STORE_DYNAMIC */
}
#endif /* MBEDTLS_PSA_KEY_STORE_DYNAMIC */
/* With a dynamic key store, allocate an entry in the cache slice,
* applicable only to non-volatile keys that get cached in RAM.