[PATCH v1 1/3] cpukit: Add signal mapping support

[Sebastian Huber]

On 20/04/2021 08:30, Chris Johns wrote:
> On 20/4/21 3:54 pm, Sebastian Huber wrote:
>> On 20/04/2021 07:30, Chris Johns wrote:
>>
>>> We need a way for libdebugger or any other piece of software to capture and
>>> cascade the call. If this can be done on aarch64 then I am happy.
>> The fatal error extensions execute in a user controllable order. You can for
>> example register a libdebugger handler which deals with break point exceptions
>> before the signal mapping handler is called.
>>
>> Synchronous exceptions should end up in an RTEMS_FATAL_SOURCE_EXCEPTION fatal
>> error. The fatal code is a pointer to rtems_exception_frame
>> (CPU_Exception_frame). In this data structure should be the complete state of
>> the interrupted context (which could be also an interrupt handler). If you want
>> to resume execution of the interrupted context, then we need an API for this
>> (setters/getters and some sort of a longjmp()).
> I do not think the fatal error handler support is suitable for a debugger, the
> frame maybe on the wrong stack. It was more complicated to implement than this
> and the reality of what is needed on the ARM required lots more. The fatal error
> handler handles fatal errors however surviving a data abort and then continuing
> in the correct CPU context/space and stack is much harder to do ....
>
> https://git.rtems.org/rtems/tree/cpukit/libdebugger/rtems-debugger-arm.c#n1454
>
> That code has to work with all data and states saved.
Yes, this code is the "some sort of a longjump()". The code mentioned 
above doesn't seem to be necessarily libdebugger-specific.

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