linux-kernel - Re: [PATCH 0/3] livepatch: add shadow variable API

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Message-ID: <alpine.LSU.2.20.1706012202490.26873@cbobk.fhfr.pm>
Date:   Thu, 1 Jun 2017 22:05:21 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Joe Lawrence <joe.lawrence@...hat.com>
cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jessica Yu <jeyu@...hat.com>, Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH 0/3] livepatch: add shadow variable API

On Thu, 1 Jun 2017, Joe Lawrence wrote:

> This patchset is a simplified livepatch port of kpatch's "shadow"
> variable API [1].  The kpatch project has successfully employed such
> shadow variables to implement patches that have extended data structure
> elements.  This API provides livepatch a means of associating new,
> shadow data fields with existing data structures. 
> 
> See the first patch for the implementation, the second for further
> documentation (API, conccurency notes, use-case code snippets) and the
> third patch for an update to the sample livepatch module using shadow
> variables.

Thanks a lot for initiating this. 

The only issue I've spotted so far -- is there any reason, why the API 
completely ignores task_struct->patch_state, and always returns the 'new' 
value?

This basically offloads the responsibility for deciding between old/new to 
each and every caller, and that feels much more error prone compared to 
having this automatically done by klp_shadow_get().

Thanks,

-- 
Jiri Kosina
SUSE Labs