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Date: Thu, 9 Feb 2017 11:27:03 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Kees Cook <keescook@...omium.org>
Cc: Mark Rutland <mark.rutland@....com>,
	"Reshetova, Elena" <elena.reshetova@...el.com>,
	Greg KH <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Will Deacon <will.deacon@....com>,
	David Windsor <dwindsor@...il.com>,
	Hans Liljestrand <ishkamiel@...il.com>,
	David Howells <dhowells@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: Re: [PATCH 4/4] refcount: Report failures
 through CHECK_DATA_CORRUPTION

On Wed, Feb 08, 2017 at 01:20:26PM -0800, Kees Cook wrote:

> Ooooh, that is intense. And the trampolines (EX_REG_HANDLERs) are all
> just there to catch whatever register gcc decides to stuff the value
> into? *cover face* Sure, okay. :)

Right, they shouldn't be big functions, but barring whole program LTO
there's just no knowing which are unused.

> I wonder how many existing WARN callsites could be repurposed to use this?

At the very least all WARN/BUG instances with trivial @format argument
that are inlined I think. For example, things like:

static inline some_function()
{
	/* ... */
	WARN(cond, "blah blah blah\n");
	/* ... */
}

where the format has no arguments. Here we can out-of-line the printk()
stuff, which, as is the purpose here, shrinks the size of the inline.

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