linux-kernel - Re: [RFC 00/31] objtool, livepatch: Livepatch module generation

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Message-ID: <20240904043034.jwy4v2y4wkinjqe4@treble>
Date: Tue, 3 Sep 2024 21:30:34 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Song Liu <song@...nel.org>
Cc: live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, Miroslav Benes <mbenes@...e.cz>,
	Petr Mladek <pmladek@...e.com>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>
Subject: Re: [RFC 00/31] objtool, livepatch: Livepatch module generation

On Tue, Sep 03, 2024 at 10:32:00AM -0700, Song Liu wrote:
> Hi Josh,
> 
> Thanks for the patchset! We really need this work so that we can undo our
> hack for LTO enabled kernels.
> 
> On Mon, Sep 2, 2024 at 9:00 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> >
> > Hi,
> >
> > Here's a new way to build livepatch modules called klp-build.
> >
> > I started working on it when I realized that objtool already does 99% of
> > the work needed for detecting function changes.
> >
> > This is similar in concept to kpatch-build, but the implementation is
> > much cleaner.
> >
> > Personally I still have reservations about the "source-based" approach
> > (klp-convert and friends), including the fragility and performance
> > concerns of -flive-patching.  I would submit that klp-build might be
> > considered the "official" way to make livepatch modules.
> >
> > Please try it out and let me know what you think.  Based on v6.10.
> >
> > Also avaiable at:
> >
> >   git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git klp-build-rfc
> 
> I tried to compile the code in this branch with gcc-12 and llvm-18. Some
> of these errors are easy to fix (attached below). But some are trickier, for
> example:
> 
> with gcc-12:
>   ...
>   BTFIDS  vmlinux
>   NM      System.map
>   SORTTAB vmlinux
> incomplete ORC unwind tables in file: vmlinux
> Failed to sort kernel tables

Thanks for trying it!  If you share your config(s) I can look into it.

I haven't tried clang yet, but will soon.

-- 
Josh