linux-kernel - Re: [PATCH 00/15] Add support for clang LTO

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Date:   Thu, 9 Nov 2017 19:54:40 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Sami Tolvanen <samitolvanen@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        cdall@...aro.org, ard.biesheuvel@...aro.org
Subject: Re: [PATCH 00/15] Add support for clang LTO

On Sat, Nov 04, 2017 at 02:13:04AM +0000, Mark Rutland wrote:
> On Fri, Nov 03, 2017 at 12:56:47PM -0700, Sami Tolvanen wrote:
> > On Fri, Nov 03, 2017 at 07:26:35PM +0000, Mark Rutland wrote:
> > > I guess that in Google you haven't tested on a platform with EL2
> > > available?
> > 
> > Correct. I'll look into this and include a fix in v2. Does this work on a
> > clang build without LTO?
> 
> I saw this on v4.14-rc7, with patch 7 (-mno-implicit-float), but no other
> patches from this series (i.e. no LTO).


Add -fno-jump-tables to ccflags-y of arch/arm64/kvm/hyp/Makefile.
Without this option, clang generates a branch instruction (br x11)
to an absolute (EL1) virtual address.

-Takahiro AKASHI

> Thanks,
> Mark.