linux-kernel - Re: [PATCH v10 0/5] Kernel parameter parser cleanup/enhancement

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Date:   Tue, 5 Jun 2018 19:25:48 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Corbet <corbet@....net>, Arnd Bergmann <arnd@...db.de>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Aaron Wu <Aaron.Wu@...log.com>,
        Tony Luck <tony.luck@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Steven Rostedt," <rostedt@...dmis.org>,
        Laura Abbott <lauraa@...eaurora.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Baoquan He <bhe@...hat.com>,
        Ilya Matveychikov <matvejchikov@...il.com>,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 0/5] Kernel parameter parser cleanup/enhancement

On Tue, 5 Jun 2018 20:05:50 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Tue, Jun 5, 2018 at 7:43 PM, Michal Suchanek <msuchanek@...e.de>
> wrote:
> > Hello,
> >
> > due to work on the fadump_extra_args I looked at the kernel
> > parameter parser and found its grammar rather curious.
> >
> > It supports double quotes but not any other quoting characters so
> > double quotes cannot be quoted. What's more, the quotes can be
> > anywhere in the parameter name or value and are interpteted but are
> > removed only from start and end of the parameter value.
> >
> > These are the patches not specific to fadump which somewhat
> > straighten the qouting grammar to make it on par with common shell
> > interpreters.  
> 
> I didn't notice any use of string_unescape_*() functionality. So, your
> patch is kinda very specific to some narrow subset of escaping and
> unescaping stuff.

It does what it says. It cannot use string_unescape because it needs to
determine the boundaries of quoted strings.

> Thus, it's still not on par with shell, right?

It does not interpret special character sequences other than quoting.

The feature would not be hard to add but I do not see the need.

Unfortunately, the existing string_unescape is totally not fitting to
be integrated into the parser for the purpose.

Thanks

Michal

> 
> >
> > Specifically double and single quotes can be used for quoting as
> > well as backslashes with the usual shell semantic. All quoting
> > characters are removed while the parameters are parsed.
> >