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Date: Thu, 8 Feb 2018 19:03:57 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>,
        kbuild test robot <fengguang.wu@intel.com>,
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        the arch/x86 maintainers <x86@kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [linus:master] BUILD REGRESSION
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On Thu, Feb 08, 2018 at 09:27:56AM -0800, Linus Torvalds wrote:
> On Thu, Feb 8, 2018 at 1:13 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > _The_ problem is that new binutils cannot sanely decode any function
> > that has a WARN in (this very much includes perf annotate):
> 
> Ugh.
> 
> Is there any reason why we don't just use UD2 and avoid this whole issue?

That's what I initially had, but then Arjan told me that a number of
emulators fatally terminate on UD2 since they assume it to be BUG. Which
is when we all went looking at UD1/UD0.

But yes, for our purposes UD2 is perfectly fine too, it will just mess
up the people doing bringup and the like.