Re: [PATCH v3 2/3] kgdb: Add NOKPROBE labels on the trap handler functions

[Doug Anderson]

Hi,

On Mon, Sep 14, 2020 at 6:02 AM Daniel Thompson
<daniel.thompson@xxxxxxxxxx> wrote:
>
> Currently kgdb honours the kprobe blocklist but doesn't place its own
> trap handling code on the list. Add labels to discourage attempting to
> use kgdb to debug itself.
>
> Not every functions that executes from the trap handler needs to be
> marked up: relatively early in the trap handler execution (just after
> we bring the other CPUs to a halt) all breakpoints are replaced with
> the original opcodes. This patch marks up code in the debug_core that
> executes between trap entry and the breakpoints being deactivated
> and, also, code that executes between breakpoint activation and trap
> exit.

Other functions that seem to be missing from a quick skim:
* kgdb_io_ready()
* kgdb_roundup_cpus()
* kgdb_call_nmi_hook()

I'm not confident in my ability to spot every code path, though, so
I'm not sure at what point we stop looking.  I only spent a few
minutes and, if important, I could dig more.  Did you have any chance
to see if there was any way to have a magic linker script just add
this to everything under "kernel/debug" or something like that where
we just use a heavier hammer to whack a whole bunch?

In general any extra annotation here is better than no annotation, I
suppose.  ...so if you just want to commit what you have (maybe with
the above 3 extra functions) then I suppose it'd be fine.

-Doug


-Doug