This reverts commit 5f29445103 - but only partially.
cmain.S for IAR is still required to keep mbed SDK boot process as it was. This
startup file for IAR is active for non-rtos projects.
Fixes#4330
* Updated docs
* Re-factored vMPU drivers
* Non-backwards-compatible API change: uvisor_ctx is now called
__uvisor_ctx and requires the user to explicitly cast it to their own
private context structure.
This only affects applications with uVisor enabled.
* Use "public box" instead of main box for box 0.
Add data and instruction synchronization barriers to prevent
interrupts from occurring after NVIC_DisableIRQ is called. This
is a backport of changes made in CMSIS_5.
The current version of cmsis shipping with mbed does not provide the __IOM and friends macros that became standard with CMSIS 4.2+. Patching these into CMSIS to allow vendors to continue updating their support libraries, awaiting a full CMSIS update in mbed (which is past due now).