linux-kernel - Re: Adding module support for __ro_after

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Message-ID: <87fuss6x3f.fsf@rustcorp.com.au>
Date:	Sun, 05 Jun 2016 14:39:08 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Kees Cook <keescook@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Laura Abbott <labbott@...oraproject.org>,
	Jessica Yu <jeyu@...hat.com>
Subject: Re: Adding module support for __ro_after_init

Kees Cook <keescook@...gle.com> writes:
> Hi Rusty,
>
> I'd love to get your thoughts on the best way to support
> __ro_after_init markings for modules. Are the r/o markings done after
> module __init runs? If so, this should make things easy, and then we
> just need to move .data..ro_after_init into .rodata at link time. If
> not, then we'd need to explicitly make this section read-only after
> _init.

As you might expect, the sections are made read-only before anything
runs.  We'll need to do the latter, which means it needs to be
page-aligned.  (Well we could put it in the same page as .rodata, and
just not protect that fully until after init).

Jessica might have more thoughts...
Rusty.