When using Arm Cortex-M Security Extensions (CMSE), Secure stack
contents can be leaked to Non-secure state via floating-point registers
when a Secure to Non-secure function call is made that returns a
floating-point value and when this is the first use of floating-point
since entering Secure state. This allows an attacker to read a limited
quantity of Secure stack contents with an impact on confidentiality.
This issue is specific to code generated using LLVM-based compilers.