Re: [kernel-hardening] Re: [PATCH v2 2/3] Mark functions with the __nocapture attribute

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	Re: [kernel-hardening] Re: [PATCH v2 2/3] Mark functions with the __nocapture attribute
Date	2016-07-12 21:50 +0200
Message-ID	<rUbQR-Xn-7@gated-at.bofh.it> (permalink)
References	<rRlD3-3xx-7@gated-at.bofh.it> <rRlD3-3xx-15@gated-at.bofh.it> <rUbea-H3-13@gated-at.bofh.it> <rUbxv-Oh-9@gated-at.bofh.it>
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On Tue, Jul 12, 2016 at 3:23 PM, Daniel Micay <danielmicay@gmail.com> wrote:
> On Tue, 2016-07-12 at 15:08 -0400, Kees Cook wrote:
>> On Mon, Jul 4, 2016 at 7:42 PM, Emese Revfy <re.emese@gmail.com>
>> wrote:
>> >
>> > The nocapture gcc attribute can be on functions only.
>> > The attribute takes one or more unsigned integer constants as
>> > parameters
>> > that specify the function argument(s) of const char* type to
>> > initify.
>> > If the marked argument is a vararg then the plugin initifies
>> > all vararg arguments.
>>
>> Why is this called "nocapture"? Not captured by what? It seems like
>> it
>> means "initify this if possible". Am I misunderstanding its purpose?
>
> It means they don't escape via that function, i.e. they aren't stored
> anywhere to be used in any way after the call.

Ah, those arguments are confirmed to not be "captured" by that
function, leaving them available to be moved to .init. Got it, thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security

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Re: [PATCH v2 2/3] Mark functions with the __nocapture attribute Kees Cook <keescook@chromium.org> - 2016-07-12 21:10 +0200
  Re: [kernel-hardening] Re: [PATCH v2 2/3] Mark functions with the  __nocapture attribute Daniel Micay <danielmicay@gmail.com> - 2016-07-12 21:30 +0200
    Re: [kernel-hardening] Re: [PATCH v2 2/3] Mark functions with the  __nocapture attribute Kees Cook <keescook@chromium.org> - 2016-07-12 21:50 +0200

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