linux-kernel - Re: [PATCH v4 51/63] objtool/klp: Introduce klp diff subcommand for diffing object files

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Message-ID: <xwbop4e2f3pcyjk22v5r6aufy2dvlwhgaxthfis6iw3mra7e53@x4r6b3qwomp4>
Date: Thu, 9 Oct 2025 16:19:05 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Petr Mladek <pmladek@...e.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Miroslav Benes <mbenes@...e.cz>, Joe Lawrence <joe.lawrence@...hat.com>, 
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>, laokz <laokz@...mail.com>, 
	Jiri Kosina <jikos@...nel.org>, Marcos Paulo de Souza <mpdesouza@...e.com>, 
	Weinan Liu <wnliu@...gle.com>, Fazla Mehrab <a.mehrab@...edance.com>, 
	Chen Zhongjin <chenzhongjin@...wei.com>, Puranjay Mohan <puranjay@...nel.org>, 
	Dylan Hatch <dylanbhatch@...gle.com>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 51/63] objtool/klp: Introduce klp diff subcommand for
 diffing object files

On Thu, Oct 09, 2025 at 02:29:43PM +0200, Petr Mladek wrote:
> Sounds reasonable and I am fine with it. I have one more question
> before I give my ack ;-)
> 
> I wonder about the patchset which better integrate callbacks with shadow
> variables and state API, see
> https://lore.kernel.org/r/20250115082431.5550-1-pmladek@suse.com
> 
> I think that it should not be that big problem to update it on top
> of this patchset. It would require:
> 
>    + moving declarations from livepatch.h to livepatch_external.h
>    + updating the macros in livepatch_helpers.h
>    + update callback-related code in create_klp_sections()
> 
> Or do you expect bigger problems, please?

Yeah, that should be pretty straightforward.  I can help with that.

Right now there's not even a way to create a klp_state.  (not sure if
anybody's actually using that feature today?)

For your patch set we can add a macro to livepatch_helpers.h for adding
a state (and its callbacks).  And then corresponding code in
create_klp_sections() as you mentioned, and a small change to
scripts/livepatch/init.c to set the klp_patch.states pointer.

-- 
Josh