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

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Message-ID: <511D074B.7040608@siemens.com>
Date:	Thu, 14 Feb 2013 16:48:27 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Tom Tromey <tromey@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jason Wessel <jason.wessel@...driver.com>,
	"kgdb-bugreport@...ts.sourceforge.net" 
	<kgdb-bugreport@...ts.sourceforge.net>,
	Andi Kleen <andi@...stfloor.org>,
	Ben Widawsky <ben@...dawsk.net>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v5 05/20] scripts/gdb: Add lx-symbols command

On 2013-02-14 16:40, Tom Tromey wrote:
>>>>>> "Jan" == Jan Kiszka <jan.kiszka@...mens.com> 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.

OK.

Jan

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Corporate Competence Center Embedded Linux
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