linux-kernel - Re: [PATCH net-next 3/8] lib: packing: add pack_fields() and unpack

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Message-ID: <38f27382-3c6d-4677-9d59-4d08104f1131@intel.com>
Date: Thu, 24 Oct 2024 09:38:48 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Vladimir Oltean <vladimir.oltean@....com>
CC: Vladimir Oltean <olteanv@...il.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/8] lib: packing: add pack_fields() and
 unpack_fields()



On 10/24/2024 6:49 AM, Vladimir Oltean wrote:
> I just want to say that I don't have any alternative proposals, nor will I
> explore your sparse suggestion. I don't know enough about sparse to judge
> whether something as 'custom' as the packing API is in scope for its
> check_call_instruction() infrastructure, how well will that solution
> deal with internal kernel API changes down the line, and I don't have
> the time to learn enough to prototype something to find the maintainers'
> answer to these questions, either. I strongly prefer to have the static
> checks inside the kernel, together with the packing() API itself, so it
> can be more easily altered.
> 
> Obviously you're still free to wait for more opinions and suggestions,
> or to experiment with the sparse idea yourself.
> 

I also have some thought about trying to catch this in a coccinelle
script. That has the trade-off that its only caught by running the
spatch/coccinelle scripts, but it would completely eliminate the need to
modify Kbuild at all.

I'm going to try and experiment with that direction and see if its feasible.

> Honestly, my opinion is that if we can avoid messing too much with the
> top-level Kbuild file, this pretty much enters "no one really cares"
> territory, as long as the code is generated only for the pack_fields()
> users. This is, in fact, one of the reasons why the patch I attached
> earlier compiles and runs the code-gen only when PACKING_CHECK_FIELDS
> is defined.

If I can't make that work today, I'll send a v2 with the
PACKING_CHECK_FIELDS and the other cleanups applied.