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Message-ID: <CAGXu5jLMsdeQ6XwBm-+kT0OkQtm78SQJRPFWueZ=wSUPeadwsw@mail.gmail.com>
Date: Wed, 29 Jun 2016 07:50:25 -0700
From: Kees Cook <keescook@...omium.org>
To: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Emese Revfy <re.emese@...il.com>,
"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>, 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>, jlayton@...chiereds.net,
Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v1 1/2] Add the initify gcc plugin
On Tue, Jun 28, 2016 at 2:05 PM, 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)?
Is there a clean way to do this that isn't arch-specific?
-Kees
--
Kees Cook
Chrome OS & Brillo Security
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