1. For SHA AC, use atomic flag to manage its ownership.
(1) Nuvoton SHA AC doesn't support SHA context save & restore, so S/W
SHA fallback has been supported before. To make non-blocking 'acquire'
semantics clearer, introduce 'try_acquire' to substitute for 'acquire'.
(2) No biting CPU due to mechanism above.
(3) No deadlock due to mechanism above.
2. For AES/DES/ECC AC, change to mutex to manage their ownership.
(1) Change crypto-misc.c to crypto-misc.cpp to utilize C++ SingletonPtr
which guarantees thread-safe mutex construct-on-first-use.
(2) With change to crypto-misc.cpp, add 'extern "C"' modifier to CRYPTO_IRQHandler()
to avoid name mangling in C++.
(3) No priority inversion because mutex has osMutexPrioInherit attribute
bit set.
(4) No deadlock because these AC are all locked for a short sequence
of operations rather than the whole lifetime of mbedtls context.
(5) For double mbedtls_internal_ecp_init() issue, it has been fixed in upper
mbedtls layer. So no need to change ecc init/free flow.
Have the HW accelearation drivers return the platform module
errors about feature unsupported, and hw acceleration failure,
because the moduel specific errors will be removed.
Take SHA1 for example, without the fix, SHA H/W is not stopped in either case:
(1) ctx->total == 0 in mbedtls_sha1_hw_finish()
(2) mbedtls_sha1_hw_finish() is not called by upper layer
For example, even though MBEDTLS_SHA512_C is disabled (via #undef MBEDTLS_SHA512_C),
mbedtls_sha512_context is still necessary due to referenced in sha512.h.
Currently, trng_api.c is located in targets/ and AES/DES/SHA alter. are located in mbedtls/.
They have shared crypto code.
If they could locate at same location e.g. mbedtls/, the shared crypto code placement would be more reasonable.
Add counter to track crypto init among crypto sub-modules. It includes:
1. Enable crypto clock
2. Enable crypto interrupt
As counter gets zero, crypto clock is disabled to save power.