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

Kees Cook
2016-07-12T19:46:00Z

On Mon, Jul 4, 2016 at 7:40 PM, Emese Revfy <re.emese@gmail.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.
>
> 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?

> The instrumentation pass of the latent_entropy plugin must run after
> the initify plugin to increase coverage.
>
> Signed-off-by: Emese Revfy <re.emese@gmail.com>

Thanks for sending this! I'll get it added to my tree for some 0day
build testing, and then get it into my -next tree.

-Kees

--
Kees Cook
Chrome OS & Brillo Security