linux-kernel - Re: [RFC PATCH 7/7] objtool: Make unwind_hints available for all architectures

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Date:   Wed, 10 Jun 2020 15:20:03 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Julien Thierry <jthierry@...hat.com>
cc:     linux-kernel@...r.kernel.org, jpoimboe@...hat.com,
        peterz@...radead.org, raphael.gault@....com
Subject: Re: [RFC PATCH 7/7] objtool: Make unwind_hints available for all
 architectures

Hi Julien,

On Mon, 8 Jun 2020, Julien Thierry wrote:

> Unwind hints are useful to give some information about the call frame
> or stack states in non-standard code.
> 
> Despite unwind hints being used in arch-independent code, the
> unwind_hint structure type itself is define in x86 kernel headers.
> 
> This is because what an unwind hint will describe is very architecture
> specific, both regarding the state and the affected registers.
> 
> To get to share this concept, expose the unwind_hint structure across
> architecutres. However, the hint types remain defined by the
> architecture code. Objtool then needs it's arch specific code to
> "decode" the unwind hint into a cfi_state.

I think it would be nice to split the patch. Something like.

1. current include/linux/frame.h mixes assembly and non-assembly 
definitions, so introduce ASSEMBLY ifdef first seems like a good idea to 
me.

2. move the relevant definitions to frame.h and add the file to 
sync-check

3. the rest of the patch

Would it make sense?

Otherwise, it looks good to me.

Miroslav