[PATCH v1 3/5] cpukit/microblaze: Add interrupt hooks

[Chris Johns]

On 18/2/22 7:12 am, Kinsey Moore wrote:
> On 2/17/2022 13:53, Chris Johns wrote:
>> On 16/2/22 7:38 am, Kinsey Moore wrote:
>>> Add hooks for manipulating system state before and after interrupts are
>>> run. These hooks serve primarily to allow the MicroBlaze libdebugger
>>> backend to prevent software breaks from occurring in interrupt context.
>> I am unsure what problem this is resolving?
> This is resolving an issue specific to libdebugger backends that use only
> software breaks without any additional architecture support. When entering
> interrupt context, breakpoints of all varieties must be disabled or libdebugger
> may be called into from interrupt context which libdebugger ignores as something
> that needs to be passed to the fatal error handler. Microblaze in particular has
> no way to set hardware breakpoints, watchpoints, or single-step operation from
> the CPU (even if they exist in some configurations) and no way to disable
> software breaks upon entry to interrupt context without hooks of this variety.

Why is this specific to software break points? A hardware break point in a
similar situation will trigger an exception.

>> Who is setting breaks points in interrupts?
> 
> Where I encountered issues was setting breaks in library functions that I was
> stepping through in non-interrupt context, particularly in memset(). ISR
> handlers can also call into this library code and libdebugger bails when
> application debugging intersects with ISR handler execution.

Interesting use case. Does this effect all archs? I think it does.

Chris