netdev - Re: [PATCH 0/9] get_abi.pl: Check for missing symbols at the ABI specs

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Date:   Thu, 9 Sep 2021 15:51:00 +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>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        Tony Luck <tony.luck@...el.com>, Yonghong Song <yhs@...com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 0/9] get_abi.pl: Check for missing symbols at the ABI
 specs

On Wed, Sep 08, 2021 at 04:58:47PM +0200, Mauro Carvalho Chehab wrote:
> Hi Greg,
> 
> Sometime ago, I discussed with Jonathan Cameron about providing 
> a way check that the ABI documentation is incomplete.
> 
> 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.
> 
> So, I ended by implementing a new feature at scripts/get_abi.pl
> which does a check on the sysfs contents of a running system:
> it reads everything under /sys and reads the entire ABI from
> Documentation/ABI. It then warns for symbols that weren't found,
> optionally showing possible candidates that might be misdefined.
> 
> I opted to place it on 3 patches:
> 
> The first patch adds the basic logic. It runs really quicky (up to 2
> seconds), but it doesn't use sysfs softlinks.
> 
> Patch 2 adds support for also parsing softlinks. It slows the logic,
> with now takes ~40 seconds to run on my desktop (and ~23
> seconds on a HiKey970 ARM board). There are space there for
> performance improvements, by using a more sophisticated
> algorithm, at the expense of making the code harder to
> understand. I ended opting to use a simple implementation
> for now, as ~40 seconds sounds acceptable on my eyes.
> 
> Patch 3 adds an optional parameter to allow filtering the results
> using a regex given by the user.
> 
> One of the problems with the current ABI definitions is that several
> symbols define wildcards, on non-standard ways. The more commonly
> wildcards used there are:
> 
> 	<foo>
> 	{foo}
> 	[foo]
> 	X
> 	Y
> 	Z
> 	/.../
> 
> The script converts the above wildcards into (somewhat relaxed)
> regexes.
> 
> There's one place using  "(some description)". This one is harder to
> parse, as parenthesis are used by the parsing regexes. As this happens
> only on one file, patch 4 addresses such case.
> 
> Patch 5 to 9 fix some other ABI troubles I identified.
> 
> In long term, perhaps the better would be to just use regex on What:
> fields, as this would avoid extra heuristics at get_abi.pl, but this is
> OOT from this patch, and would mean a large number of changes.

This is cool stuff, thanks for doing this!

I'll look at it more once 5.15-rc1 is out, thanks.

greg k-h