linux-kernel - Re: [PATCH v1 1/2] Add the initify gcc plugin

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Message-Id: <20160629210319.07dc960dc26fd109a636b1ff@gmail.com>
Date:	Wed, 29 Jun 2016 21:03:19 +0200
From:	Emese Revfy <re.emese@...il.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	kernel-hardening@...ts.openwall.com, pageexec@...email.hu,
	spender@...ecurity.net, mmarek@...e.com, keescook@...omium.org,
	linux-kernel@...r.kernel.org, yamada.masahiro@...ionext.com,
	linux-kbuild@...r.kernel.org, minipli@...linux.so,
	linux@...linux.org.uk, catalin.marinas@....com,
	david.brown@...aro.org, benh@...nel.crashing.org,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	jlayton@...chiereds.net, arnd@...db.de
Subject: Re: [PATCH v1 1/2] Add the initify gcc plugin

On Tue, 28 Jun 2016 23:05:56 +0200
Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> On Tue, Jun 28 2016, Emese Revfy <re.emese@...il.com> wrote:
> 
> > The kernel already has a mechanism to free up code and data memory that
> > is only used during kernel or module initialization.
> > This plugin will teach the compiler to find more such code and data that
> > can be freed after initialization.
> > It has two passes. The first one tries to find all functions that
> > can be become __init/__exit. The second one moves string constants
> > (local variables and function string arguments marked by
> > the nocapture attribute) only referenced in __init/__exit functions
> > to the __initconst/__exitconst sections.
> > It reduces memory usage. This plugin can be useful for embedded systems.
> 
> May I suggest, as a followup patch, a debug option/plugin parameter to
> put the strings in a section which will not be reaped after init, but
> just marked inaccessible, with graceful handling of bad accesses (print
> a big fat warning, make the page(s) readable, continue)?

I think even better would be to verify the whole init section.
Unfortunately, I won't implement it anytime soon because my project ends this week.

-- 
Emese