Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

From: Peter Zijlstra
Date: Wed Oct 16 2019 - 03:50:05 EST

On Tue, Oct 15, 2019 at 06:27:05PM -0400, Steven Rostedt wrote:

> (7) Seventh session, titled "klp-convert and livepatch relocations", was led
> by Joe Lawrence.
> Joe started the session with problem statement: accessing non exported / static
> symbols from inside the patch module. One possible workardound is manually via
> kallsyms. Second workaround is klp-convert, which actually creates proper
> relocations inside the livepatch module from the symbol database during the
> final .ko link.
> Currently module loader looks for special livepatch relocations and resolves
> those during runtime; kernel support for these relocations have so far been
> added for x86 only. Special livepatch relocations are supported and processed
> also on other architectures. Special quirks/sections are not yet supported.
> Plus klp-convert would still be needed even with late module patching update.
> vmlinux or modules could have ambiguous static symbols.
> It turns out that the features / bugs below have to be resolved before we
> can claim the klp-convert support for relocation complete:
> - handle all the corner cases (jump labels, static keys, ...) properly and
> have a good regression tests in place

I suppose all the patches in this series-of-series here will make life
harder for KLP, static_call() and 2 byte jumps etc..

> - one day we might (or might not) add support for out-of-tree modules which
> need klp-convert
> - BFD bug 24456 (multiple relocations to the same .text section)