linux-kernel - Re: [PATCH v2 1/3] Add the initify gcc plugin

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Date:	Wed, 13 Jul 2016 22:48:49 +0200
From:	Emese Revfy <re.emese@...il.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	PaX Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Michal Marek <mmarek@...e.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	linux-kbuild <linux-kbuild@...r.kernel.org>, minipli@...linux.so,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	David Brown <david.brown@...aro.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Layton <jlayton@...chiereds.net>,
	Arnd Bergmann <arnd@...db.de>, Sam Ravnborg <sam@...nborg.org>,
	Karsten Keil <isdn@...ux-pingi.de>
Subject: Re: [PATCH v2 1/3] Add the initify gcc plugin

On Tue, 12 Jul 2016 15:45:56 -0400
Kees Cook <keescook@...omium.org> wrote:

> On Mon, Jul 4, 2016 at 7:40 PM, Emese Revfy <re.emese@...il.com> wrote:
> > If a function is called by __init and __exit functions as well then
> > the plugin moves it to the __exit section. This causes false positive
> > section mismatch errors/warnings that I don't know how to handle yet.
> 
> Should the mismatch checker be updated to recognize this case? Without
> the plugin, I assume these kinds of functions would only ever be
> marked for __exit? If so, should the plugin strip the __init marking
> and only add __exit?

I don't modify the existing attributes. I just add a new __init/__exit when
a function hasn't a section attribute yet.
There are three cases:
 * when the function is called only by __init functions then the plugin adds
   the __init attribute
 * when the function is called only by __exit functions then the plugin adds
   the __exit attribute
 * when the function is called by __init and __exit functions too then the
   plugin adds the __exit attribute.
The last case causes the false positive(?) message of the section mismatch.

-- 
Emese