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

Kees Cook
2016-07-12T22:39:05Z

On Tue, Jul 12, 2016 at 6:08 PM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> On Tue, Jul 12, 2016 at 03:45:56PM -0400, Kees Cook wrote:
>> On Mon, Jul 4, 2016 at 7:40 PM, Emese Revfy <re.emese@gmail.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?
>
> That sounds like a problem for architectures that still discard the
> __exit section at link time to reduce the size of the linked kernel
> image - though, obviously, if using the plugin results in a smaller
> kernel image _with_ the exit sections, then there's a net benefit
> size-wise.

Ah right, __exit is dropped for non-modular builds. So, for "both
__init and __exit" it sounds like the behavior depends on the build:

- if modular: remove __init marking (since we need it after init)
- if non-modular: remove __exit marking (since we'll never call exit)

Is this something the build itself (rather than the plugin) could
notice and fix up? Hmmm

-Kees

--
Kees Cook
Chrome OS & Brillo Security