Since Mbed TLS is a cross-platform library, we don't deal directly with TrustZone-M.
However, if I have understood correctly, I think your usecase is solved by the Trusted Firmware M (TF-M) project[1], which is an implementation of secure firmware that provides cryptography services via non-secure-callable APIs.
TF-M uses Mbed TLS internally and implements the PSA Certified Cryptography API[2]. The Crypto Service Integration Guide[3] in the documentation should be a good starting point for what you are trying to do.
Hi Mbed TLS,
I am looking for some suggestions about make some (or all) Mbed TLS APIs non-secure callable APIs on armv8m.
The background is that I am going to have a secure firmware that provides encryption services by building part (or whole) of Mbed TLS into that firmware and make those original mbedtls_x APIs non-secure callable, so the existing non-secure firmware could link
those non-secure callable APIs and use them.
Some of my thoughts:
(1) The easiest way to do it I can think of is just add the attribute "cmse_nonsecure_call" to those APIs' declaration (or use a macro to wrap the attribute for conditional build to not impact others don't want it), but I do not think this modification could
be accepted by upstream 🙂.
(2) So my another thought is duplicate all header files and put them under another folder, assuming it is my-include folder, then I can do whatever I want to my-include folder, but there is also a problem I can think of: a merge/compare burden between include
and my-include folder after I have updated Mbed TLS.
I really appreciate other suggestions!
