On 7/21/20 7:04 PM, Josh Poimboeuf wrote:
On Tue, Jul 21, 2020 at 12:14:06PM -0400, Joe Lawrence wrote:
Compiler optimizations can have serious implications on livepatching.
Create a document that outlines common optimization patterns and safe
ways to livepatch them.
Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
There's a lot of good info here, but I wonder if it should be
reorganized a bit and instead called "how to create a livepatch module",
because that's really the point of it all.
That would be nice. Would you consider a stand-alone
compiler-optimizations doc an incremental step towards that end? Note
that the other files (callbacks, shadow-vars, system-state) in their
current form might be as confusing to the newbie.
I'm thinking a newcomer reading this might be lost. It's not
necessarily clear that there are currently two completely different
approaches to creating a livepatch module, each with their own quirks
and benefits/drawbacks. There is one mention of a "source-based
livepatch author" but no explanation of what that means.
Yes, the initial draft was light on source-based patching since I only
really tinker with it for samples/kselftests. The doc was the result of
an experienced livepatch developer and Sunday afternoon w/the compiler.
I'm sure it reads as such. :)
Maybe it could begin with an overview of the two approaches, and then
delve more into the details of each approach, and then delve even more
into the gory details about compiler optimizations.
Up until now, the livepatch documentation has danced around the
particular creation method and only described the API in abstract. If a
compiler considerations doc needs to have that complete context then I'd
suggest we reorganize the entire lot as a prerequisite.
Also the kpatch-build section can reference the patch author guide which
we have on github.
Good point. I think there are a few kpatch-specific implications
(sibling call changes maybe) to consider.
-- Joe
