linux-kernel - Re: [PATCH 1/2] arm64: Implement arch_stack_walk

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Message-ID: <ox4c6flgu7mzkvyontbz2budummiu7e6icke7xl3msmuj2q2ii@xb5mvqcst2vg>
Date: Tue, 18 Mar 2025 16:00:32 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Song Liu <song@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-toolchains@...r.kernel.org, live-patching@...r.kernel.org, indu.bhagat@...cle.com, 
	puranjay@...nel.org, wnliu@...gle.com, irogers@...gle.com, joe.lawrence@...hat.com, 
	mark.rutland@....com, peterz@...radead.org, roman.gushchin@...ux.dev, 
	rostedt@...dmis.org, will@...nel.org, kernel-team@...a.com
Subject: Re: [PATCH 1/2] arm64: Implement arch_stack_walk_reliable

On Tue, Mar 18, 2025 at 01:14:40PM -0700, Song Liu wrote:
> >
> > See for example all the error conditions in the x86 version of
> > arch_stack_walk_reliable() and in arch/x86/kernel/unwind_frame.c.
> 
> I guess I missed this part:
> 
> diff --git i/arch/arm64/kernel/stacktrace.c w/arch/arm64/kernel/stacktrace.c
> index 69d0567a0c38..3bb8e3ea4c4b 100644
> --- i/arch/arm64/kernel/stacktrace.c
> +++ w/arch/arm64/kernel/stacktrace.c
> @@ -268,6 +268,8 @@ kunwind_next(struct kunwind_state *state)
>         case KUNWIND_SOURCE_TASK:
>         case KUNWIND_SOURCE_REGS_PC:
>                 err = kunwind_next_frame_record(state);
> +               if (err && err != -ENOENT)
> +                       state->common.unreliable = true;
>                 break;
>         default:
>                 err = -EINVAL;

I still see some issues:

  - do_kunwind() -> kunwind_recover_return_address() can fail

  - do_kunwind() -> consume_state() can fail

  - even in the -ENOENT case the unreliable bit has already been set
    right before the call to kunwind_next_frame_record_meta().

-- 
Josh