[TF-A] Stack Protector for platforms not implementing plat_get_stack_protector_canary

Hi all,

I recently encountered a build issue with the imx8m platform. Buildroot will set the SSP (Stack Smashing Protection) option to on by default in the next release. This option also turns on the ENABLE_STACK_PROTECTOR in the ATF. But since the plat_get_stack_protector_canary() function is not implemented for the imx8m for example, the build fails for this platform. My question now is: could you implement a generic function like it is implemented for some platforms that don't have a real RNG? Or is there a concern here?

I must admit that I have no experience with ATF other than building and deploying it.

Thanks