Re: [PATCH v5 05/20] scripts/gdb: Add lx-symbols command

From: Jan Kiszka
Date: Thu Feb 14 2013 - 10:49:10 EST

On 2013-02-14 16:40, Tom Tromey wrote:
>>>>>> "Jan" == Jan Kiszka <jan.kiszka@xxxxxxxxxxx> writes:
> Jan> In addition, the command installs a silent breakpoint in the load_module
> Jan> function at the point where the module was loaded but not yet
> Jan> initialized. The breakpoint handler will try to load symbols from the
> Jan> module files found during lx-symbols execution. This way, breakpoints
> Jan> can be set to module initialization functions, and there is usually no
> Jan> need to explicitly call lx-symbols after (re-)loading a module.
> It is a nice approach, but I wonder whether the kernel's gdb stub could
> use the existing qXfer:libraries remote protocol packet. And, if not,
> could we extend gdb to make it work.

That would help kgdb, but not QEMU or hardware debuggers. They have no
"Linux awareness" built in.

> Jan> + def _find_breakpoint_location(self):
> Jan> + breakpoint_match = "^[0-9]*[\t]*err = parse_args\(.*"
> Jan> +
> Jan> + src = gdb.execute("list kernel/module.c:load_module",
> Jan> + to_string = True)
> Whatever works -- but I think there are better ways.
> The simplest is introducing a function that is called at the right spot
> with the right arguments. It doesn't need to do anything, just be a
> name where you can put a breakpoint.

Yes, I have this on my todo list. I already have a local config here
where the current heuristic broke - once again. We likely just need to
enforce un-inlining of do_init_module.

> Jan> + import symbols
> I think it's better to put everything into its own package, e.g. 'import
> linux.symbols', to try to avoid conflicts with other python modules that
> may get loaded.



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