printing register values from exception handler...

You'll need to switch to each mode, and then write the registers to RAM somewhere.

To switch mode, write the mode to the CPSR register, e.g.

msr cpsr_c, #0xd1 // switches to FIQ mode

When you're in FIQ mode, write register r8-r14 somewhere, and then switch to other mode.

Check the ARM Architecture Reference Manual for all the modes, and register banks.

To retrieve registers of user mode, use a special instruction:

stmia r0, {r13-r14}^ // note the '^' at the end

After writing all the registers to RAM, switch back to SVC mode, and print all of them.

That means that your application should expect to never see those exceptions, which means that if you hit them, something's wrong with your code. Which means you should still be in the "I have a JTAG pod hooked up" stage of things. Why not just an infinite loop, and if you find yourself in one of them then you go spelunking to figure out how you got there?

Then in shipping code, any of those events should be cause for a watchdog reset.

Unless you don't/can't use JTAG for debugging.

Depends on the users. I've had code in alpha/beta stages where the exceptions were caught, and a memory map, including the register dump and stacks could be sent back to the developers as an e-mail attachment. It's very valuable for those 1-in-a-million bugs that are hard to reproduce in the lab.

Exceptions are priviledged modes. So you can switch between modes and the associated banked registers by writing to CPSR. Set it to the user mode at the very last.

Nope.

RTFM

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant