Use a singleton Mutex in platforms_alt functions, to be shared
with the trng function, to save RAM. Rename `platform_alt.c`
to `platform_alt.cpp` as the mutex is in a `singletonPtr`
template class.
Like all HAL APIs, the calls in trng_api.h are not expected to
be thread-safe.
All current accesses to the TRNG HAL are currently via
`mbedtls_hardware_poll`. Mbed TLS does not currently serialise these
calls itself, as `MBEDTLS_THREADING_C` is not enabled. But even if
Mbed TLS's own accesses were serialised, there are other direct
users of `mbedtls_hardware_poll` such as randLIB, that need to use
direct calls due to lack of API to extract entropy from Mbed TLS.
As such it makes sense to treat `mbedtls_hardware_poll` as a de facto
public Mbed OS API, akin to the C++ veneers on top of the HAL, and add a
PlatformMutex there so that it is safe for multithreaded use.
Rename the generic name `ctx` of `mbedtls_platform_context`
in `platform_alt.c` to a specific name `plat_ctx`, to avoid conflicts
when used as external in crypto modules.
The DEVICE_FOO macros are always defined (either 0 or 1).
This patch replaces any instances of a define check on a DEVICE_FOO
macro with value test instead.
Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
1. Move the `mbedtls_platform_context` to be platform code, in `features/mbedtls/platfrom/`.
2. Add static refernce counter, to setup and teardown the platform code only once.
3. Adjust Cryptocell porting accordingly.
Ron Eldor
Kevin Bracey
Alastair D'Silva
Martin Kojtal