linux-kernel - Re: [RFC PATCH v4 1/2] arm64: Introduce stack trace reliability checks in the unwinder

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Date:   Fri, 21 May 2021 17:11:17 +0100
From:   Mark Brown <broonie@...nel.org>
To:     madvenka@...ux.microsoft.com
Cc:     mark.rutland@....com, jpoimboe@...hat.com, ardb@...nel.org,
        jthierry@...hat.com, catalin.marinas@....com, will@...nel.org,
        jmorris@...ei.org, pasha.tatashin@...een.com,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v4 1/2] arm64: Introduce stack trace reliability
 checks in the unwinder

On Sat, May 15, 2021 at 11:00:17PM -0500, madvenka@...ux.microsoft.com wrote:

> Other reliability checks will be added in the future.

...

> +	frame->reliable = true;
> +

All these checks are good checks but as you say there's more stuff that
we need to add (like your patch 2 here) so I'm slightly nervous about
actually setting the reliable flag here without even a comment.  Equally
well there's no actual use of this until arch_stack_walk_reliable() gets
implemented so it's not like it's causing any problems and it gives us
the structure to start building up the rest of the checks.

The other thing I guess is the question of if we want to bother flagging
frames as unrelaible when we return an error; I don't see an issue with
it and it may turn out to make it easier to do something in the future
so I'm fine with that.

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