Need some help with xtensa processor

Ben Greear
2016-08-17T00:02:12Z

Hello!

I'm working on a closed source (not my decision) project that uses
an xtensa cpu. I have no jtag access to this board, but I can pass
messages, including grabbing 'logs' and stack traces on crash, and so forth.

Currently, I have narrowed down a bug to a wild write on a structure of
method pointers. Next time code tries to execute one of these methods,
it crashes spectacularly.

So, I wanted to tell the processor to set a watchpoint on this address, and
then assert or otherwise give me an ability to grab the program counter, stack,
etc, when something writes on the memory.

I think I know how to set the BREAKA, BREAKC registers, but I must be missing something
related perhaps to setting up a proper exception vector handler for this? Whatever
the cause, I can scribble on memory after setting the watchpoint and nothing useful
happens.

So, I'd appreciate pointers if someone has some ideas. And, if someone wants to
work on this for pay, please contact me off-list.