linux-kernel - Re: [RFC PATCH v3 1/4] arm64: Introduce stack trace reliability checks in the unwinder

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Message-ID: <20210504215248.oi3zay3memgqri33@treble>
Date:   Tue, 4 May 2021 16:52:48 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     madvenka@...ux.microsoft.com
Cc:     broonie@...nel.org, mark.rutland@....com, 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 v3 1/4] arm64: Introduce stack trace reliability
 checks in the unwinder

On Mon, May 03, 2021 at 12:36:12PM -0500, madvenka@...ux.microsoft.com wrote:
> @@ -44,6 +44,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>  	unsigned long fp = frame->fp;
>  	struct stack_info info;
>  
> +	frame->reliable = true;
> +

Why set 'reliable' to true on every invocation of unwind_frame()?
Shouldn't it be remembered across frames?

Also, it looks like there are several error scenarios where it returns
-EINVAL but doesn't set 'reliable' to false.

-- 
Josh