Expose Frame Type and Stop Reason in python Unwinder API
Andrew Wock
ajwock@gmail.com
Thu Aug 22 02:28:47 GMT 2024
Hello,
Recently I wrote a kernel trapframe unwinder using the python API, and
I was able to successfully extract the registers from the trapframe.
However, sometimes gdb would throw the "previous frame inner to this
frame" error on me. This is because unwinding a trapframe sometimes
results in unwinding to a different stack.
The way this is fixed in the internal unwinder API is that there are
special frame types such as SIGTRAMP_FRAME which don't get checked for
that error.
Additionally, some trapframes unwind into userspace. In those cases
I'd like to be able to stop the backtrace by setting a stop reason.
More broadly this would be useful for any case where a user wants to
stop the stacktrace at a certain point for whatever their use case is.
I'm interested in moving forward and writing a patch for this.
One implementation detail I noticed that complicates this
implementation is that all python unwinders are internally modeled as
a single C unwinder in py-unwind.c:974. I believe that in order to
support a frame type feature, each unwinder will need to be modeled as
an independent C unwinder.
I am proposing this here to get community feedback on whether this
feature should be supported.
Thanks,
Andrew Wock
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