linux-kernel - Re: [PATCH v1 2/2] Mark functions with the _

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Message-ID: <1467245565.24287.115.camel@perches.com>
Date:	Wed, 29 Jun 2016 17:12:45 -0700
From:	Joe Perches <joe@...ches.com>
To:	Emese Revfy <re.emese@...il.com>
Cc:	kernel-hardening@...ts.openwall.com, pageexec@...email.hu,
	spender@...ecurity.net, mmarek@...e.com, keescook@...omium.org,
	linux-kernel@...r.kernel.org, yamada.masahiro@...ionext.com,
	linux-kbuild@...r.kernel.org, minipli@...linux.so,
	linux@...linux.org.uk, catalin.marinas@....com,
	linux@...musvillemoes.dk, david.brown@...aro.org,
	benh@...nel.crashing.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, jlayton@...chiereds.net, arnd@...db.de
Subject: Re: [PATCH v1 2/2] Mark functions with the __nocapture attribute

On Wed, 2016-06-29 at 20:42 +0200, Emese Revfy wrote:
> On Tue, 28 Jun 2016 14:00:57 -0700 Joe Perches <joe@...ches.com> wrote:
> > On Tue, 2016-06-28 at 22:40 +0200, Emese Revfy wrote:
> > > On Tue, 28 Jun 2016 09:43:31 -0700 Joe Perches <joe@...ches.com> wrote:
> > > > On Tue, 2016-06-28 at 13:36 +0200, Emese Revfy 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.
> > > > Perhaps this should be const <void>*
> > > For me function arguments are the values passed to a function call so
> > > the const char* type is good because this is the only one that the plugin handles
> > > (for now at least).
> > OK, but this function prototype specified takes a const void *
> > 
> > +extern void * memcpy(void *, const void *, __kernel_size_t) __nocapture(2);
> What matters for the plugin is the type of the passed arguments (which can be const char*
> in the current implementation), not that of the parameters.

And how does this work when the prototype requires the compiler to
implicit cast to const void * before calling the function?