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

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Message-ID: <CAPhsuW6vDYjiy1_tOhy--ULC8UWtpu4E_nd8uY8qg98eLuygQw@mail.gmail.com>
Date: Fri, 14 Feb 2025 10:10:29 -0800
From: Song Liu <song@...nel.org>
To: Puranjay Mohan <puranjay@...nel.org>
Cc: Indu Bhagat <indu.bhagat@...cle.com>, Weinan Liu <wnliu@...gle.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	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

Hi Puranjay,

Thanks for running the tests.

On Fri, Feb 14, 2025 at 12:56 AM Puranjay Mohan <puranjay@...nel.org> wrote:
[...]
> >
> > I am really curious whether you have the same problem in your
> > setup.
>
> Hi Song,
>
> I did this test and found the same issue as you (gdb assembly broken),
> but I can see this issue even without the inlining. I think GDB tried to
> load the debuginfo and that is somehow broken therefore it fails to
> disassemblt properly.

Yes, this matches my observations: gcc-11 generates the .ko that
confuses gdb.

I tested with two versions of gdb (10.2 and 14.2), both have the
problem. OTOH, lldb is able to disassemble copy_process from a
gcc-compiled .ko file properly.

> But even with inlining, I couldn't see the warning about the refcount
> with my setup.

This also matches my observations. gcc-11 compiled livepatch
works fine.

Thanks,
Song