Re: [RFC PATCH 0/9] livepatch: consistency model

From: Josh Poimboeuf
Date: Tue Mar 10 2015 - 12:23:56 EST

On Mon, Feb 09, 2015 at 11:31:12AM -0600, Josh Poimboeuf wrote:
> This patch set implements a livepatch consistency model, targeted for 3.21.
> Now that we have a solid livepatch code base, this is the biggest remaining
> missing piece.
> This code stems from the design proposal made by Vojtech [1] in November. It
> makes live patching safer in general. Specifically, it allows you to apply
> patches which change function prototypes. It also lays the groundwork for
> future code changes which will enable data and data semantic changes.
> It's basically a hybrid of kpatch and kGraft, combining kpatch's backtrace
> checking with kGraft's per-task consistency. When patching, tasks are
> carefully transitioned from the old universe to the new universe. A task can
> only be switched to the new universe if it's not using a function that is to be
> patched or unpatched. After all tasks have moved to the new universe, the
> patching process is complete.

Just an update on the status of this RFC. Thanks to everybody for all
the useful comments. I plan to incorporate the resulting changes in an
eventual v2 of this patch set.

But, as Peter and Ingo have pointed out, stack traces are indeed
unreliable. I have some ideas about how to improve them, coming soon in
another RFC, which will be a prerequisite for this patch set.

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