C compiler

[Claudio L.]

(09-14-2015 05:45 AM)cyrille de brébisson Wrote:  Hello,

> If they allowed native programming, they could use the MMU to block our code from altering any areas they want.

This is assuming that the OS does support/use the MMU, or can be modified to do so.

Cyrille

The OS does not need to be modified unless it already implements MMU protection.
If the OS does not use the MMU it's better, you can do what hpgcc3 does:
* Save all hardware registers
* Take control of the CPU exceptions, enable the MMU to create your own isolated environment
* Run the native user program in a separate address space
* Unwind the mess, shut down the MMU, restore system exception handlers
* Restore all hardware registers and return like nothing happened.

This way you could create a secure wrapper for people to run native code in a completely sandboxed environment. This could include a virtual stack where the code could take arguments from and return results (the Prime's data and code don't need to be visible from within this environment). The wrapper would be in charge of copying the arguments and results from/back to Prime memory.
Providing an environment like described above, some useful software could be written for the Prime (I'm willing to port newRPL to such environment). You could of course disallow its use during exam mode.