Re: [PATCH 0/2] livepatch: Add compiler optimization disclaimer/docs

[Miroslav Benes]

Hi,

On Tue, 21 Jul 2020, Joe Lawrence wrote:

> In light of [PATCH] Revert "kbuild: use -flive-patching when
> CONFIG_LIVEPATCH is enabled" [1], we should add some loud disclaimers
> and explanation of the impact compiler optimizations have on
> livepatching.
> 
> The first commit provides detailed explanations and examples.  The list
> was taken mostly from Miroslav's LPC talk a few years back.  This is a
> bit rough, so corrections and additional suggestions welcome.  Expanding
> upon the source-based patching approach would be helpful, too.
> 
> The second commit adds a small README.rst file in the livepatch samples
> directory pointing the reader to the doc introduced in the first commit.
> 
> I didn't touch the livepatch kselftests yet as I'm still unsure about
> how to best account for IPA here.  We could add the same README.rst
> disclaimer here, too, but perhaps we have a chance to do something more.
> Possibilities range from checking for renamed functions as part of their
> build, or the selftest scripts, or even adding something to the kernel
> API.  I think we'll have a better idea after reviewing the compiler
> considerations doc.

thanks to Marcos for resurrecting this.

Joe, do you have an updated version by any chance? Some things have 
changed since July 2020 so it calls for a new review. If there was an 
improved version, it would be easier. If not, no problem at all.

Miroslav