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

From: Kees Cook
Date: Tue Jul 12 2016 - 16:06:03 EST

On Tue, Jul 12, 2016 at 4:07 PM, Emese Revfy <re.emese@xxxxxxxxx> wrote:
> On Tue, 12 Jul 2016 15:45:56 -0400
> Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Mon, Jul 4, 2016 at 7:40 PM, Emese Revfy <re.emese@xxxxxxxxx> wrote:
>> 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.
> I'll send a new patch set soon. I'm working on some fixes and
> I would like to implement the handling of return uses to increase the coverage
> (which decreases because of the bug fixes :) ).
> So please hold off with testing until the next patch.

Okay, cool. I'll just do some simple tests with what I have so I can
feel like I understand its intended use, etc. :)

One change I made was to add this comment in compiler-gcc.h for people
that become curious about __nocapture and go looking for its
definition (please feel free to adjust for accuracy, etc):

* The initify gcc-plugin attempts to identify const arguments that are only
* used during init (see __init), so they can be moved to the .init.rodata
* section. If an argument is passed to a non-init function, it must
* normally be assumed that such an argument has been captured by that
* function and may be used in the future when .init has been unmapped from
* memory. In order to identify functions that are confirmed to not capture
* their arguments, the __nocapture() attribute is used so that initify can
* better identify candidate variables.
# define __nocapture(...) __attribute__((nocapture(__VA_ARGS__)))


Kees Cook
Chrome OS & Brillo Security