From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>
Subject: Re: [PATCH 00/33] Compile-time stack metadata validation
Date: Mon, 15 Feb 2016 21:02:01 +0100
Message-ID: <20160215200201.GN3696@two.firstfloor.org>
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Cc: Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
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	Anil S Keshavamurthy <anil.s.keshavamurthy-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Herbert Xu <herbert-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>,
	Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
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	Bernd Petrovitsch <bernd-JY8rjfDgnXcb9sJ47jD7nuTv7YV0F9Eg@public.gmane.org>,
	linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Pedro Alves <palves-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
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> > There are two ways to fix the warnings:
> >
> > 1. get rid of the thunks and call the C functions directly; or
> 
> No. Not until gcc learns about per-function callibg conventions (so that it can
> be marked as not clobbering registers).

It does already for static functions in 5.x (with -fipa-ra).
And with LTO it can be used even somewhat globally.

Even older version supported it, for only for x86->SSE on 32bit, which
is useless for the kernel. But the new IPA-RA propagates which registers
are clobbered.

That said it will probably be a long time until we can drop support for
older compilers.  So for now the manual method is still needed.

-Andi

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