linux-kernel - Re: [PATCH RFC 0/1] get_abi.pl: add support for ABI valitation in runtime

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Date:   Thu, 24 Jun 2021 16:08:09 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc:     Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH RFC 0/1] get_abi.pl: add support for ABI valitation in
 runtime

On Fri, Jun 18, 2021 at 01:28:36PM +0200, Mauro Carvalho Chehab wrote:
> Hi Greg,
> 
> I was talking today with Jonathan Cameron today about how to ensure that
> the ABI is not missing something.
> 
> While it would be doable to validate the ABI by searching __ATTR and similar
> macros around the driver, this would probably be very complex and would
> take a while to parse.
> 
> Yet, there's one way that should be quick and easier to implement:
> 
> Read the symbols from the current system in runtime, and check if
> everything is declared under Documentation/ABI.

Nice!

> As you know, scripts/get_abi.pl has already a search command, that would
> allow seeking for a symbol inside the ABI. Using a logic similar to that,
> but checking for all symbols under /sys is not hard to implemenent.
> That's what patch 1 does.
> 
> Right now, the results aren't exaustive (I opted this way for the RFC
> version, as otherwise there will be too many symbols that won't match
> the regexes generated from the What:  fields).
> 
> It basically reports results where the sysfs nodename matches one or
> more What, but doesn't match the regex.
> 
> This implementation runs very quick on my desktop: it takes less than
> 2 seconds to run. So, it sounds a good start to help identifying what's
> missing.
> 
> One of the problems with the ABI definitions is how to define wildcards
> there. Different ABI declarations use different notations. For this first
> RFC version, it all the above as wildcards[1]:
> 
> 	<foo>
> 	{foo}
> 	[foo]
> 	/.../
> 	*
> 
> and convert them into:
> 
> 	.*
> 
> [1] perhaps the better would be to just use regex on What:, as this would
>     avoid extra heuristics at get_abi.pl, but this is somewhat OOT from
>     this patch.
> 
> One of the first results is that some /sys symbols that are present
> on *lots* of sysfs nodes, but they aren't properly defined at ABI:
> 
> 	 /sys/.*/(initstate|bind|unbind)
> 
> (there are definitions, but those aren't covering all occurrences)

We should fix that up.

> Another problem it caught is that slab definitions are like:
> 	 /sys/kernel/slab/cache/alloc_calls
> 
> Instead of using a wildcard, like:
> 	/sys/kernel/slab/*/alloc_calls
> or:
> 	/sys/kernel/slab/<cache>/alloc_calls
> 
> So, they don't  match the actual symbols found at the system.

Then we should also fix those up.

> What do you think?

I like this, thanks for doing this.  We should fix up the text files to
match what we have in a format that we can actually test for things.
That will be very helpful to run on some devices so that I can go yell
at driver developers :)

thanks,

greg k-h