linux-kernel - Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

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Message-ID: <20250218184059.iysrvtaoah6e4bu4@jpoimboe>
Date: Tue, 18 Feb 2025 10:40:59 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Song Liu <song@...nel.org>
Cc: Puranjay Mohan <puranjay@...nel.org>, Weinan Liu <wnliu@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Indu Bhagat <indu.bhagat@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>, roman.gushchin@...ux.dev,
	Will Deacon <will@...nel.org>, Ian Rogers <irogers@...gle.com>,
	linux-toolchains@...r.kernel.org, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org, joe.lawrence@...hat.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

On Tue, Feb 18, 2025 at 10:20:10AM -0800, Song Liu wrote:
> Hi Josh,
> 
> On Mon, Feb 17, 2025 at 10:37 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> >
> > On Mon, Feb 17, 2025 at 08:38:22PM -0800, Song Liu wrote:
> > > On Fri, Feb 14, 2025 at 3:23 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> > > > Poking around the arm64 module code, arch/arm64/kernel/module-plts.c
> > > > is looking at all the relocations in order to set up the PLT.  That also
> > > > needs to be done for klp relas, or are your patches already doing that?
> > >
> > > I don't think either version (this set and my RFC) added logic for PLT.
> > > There is some rela logic on the kpatch-build side. But I am not sure
> > > whether it is sufficient.
> >
> > The klp relas looked ok.  I didn't see any signs of kpatch-build doing
> > anything wrong.  AFAICT the problem is that module-plts.c creates PLT
> > entries for regular relas but not klp relas.
> 
> In my tests (with printk) module-plts.c processes the .
> klp.rela.vmlinux..text.copy_process section just like any other .rela.*
> sections. Do we need special handling of the klp.rela.* sections?

Ok, I see how it works now:

klp_write_section_relocs()
	apply_relocate_add()
		module_emit_plt_entry()
  
If that code is working correctly then I'm fresh out of ideas...

-- 
Josh