Hi, On Fri, 31 May 2024, Joe Lawrence wrote: > On 5/31/24 07:23, Miroslav Benes wrote: > > 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. > > > > Yea, it's been a little while :) I don't have any newer version than > this one. I can rebase, apply all of the v1 suggestions, and see where > it stands. LMK if you can think of any specifics that could be added. I will walk through the patches first to see if there is something which can/should be changed given the development since then. > For example, CONFIG_KERNEL_IBT will be driving some changes soon, > whether it be klp-convert for source-based patches or vmlinux.o binary > comparison for kpatch-build. True. > I can push a v2 with a few changes, but IIRC, last time we reviewed > this, it kinda begged the question of how someone is creating the > livepatch in the first place. As long as we're fine holding that > thought for a while longer, this doc may still be useful by itself. If I remember correctly, the conclusion was that this doc was beneficial on its own. Miroslav
