linux-kernel - Re: [PATCH 07/15] arm64: use -mno-implicit-float instead of -mgeneral-regs-only

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Date:   Fri, 3 Nov 2017 18:52:22 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, Greg Hackmann <ghackmann@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 07/15] arm64: use -mno-implicit-float instead of
 -mgeneral-regs-only

On Fri, Nov 03, 2017 at 06:31:56PM +0000, Mark Rutland wrote:
> On Fri, Nov 03, 2017 at 10:11:52AM -0700, Sami Tolvanen wrote:
> > From: Greg Hackmann <ghackmann@...gle.com>
> > 
> > LLVM bug 30792 causes clang's AArch64 backend to crash compiling
> > arch/arm64/crypto/aes-ce-cipher.c.  Replacing -mgeneral-regs-only with
> > -mno-implicit-float is the suggested workaround.
> > 
> > Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
> > Cc: Matthias Kaehlcke <mka@...omium.org>
> > Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> 
> Just to check, what happens if you pass both to clang?

Apparently not. However, we can do:

-KBUILD_CFLAGS  += -mgeneral-regs-only $(lseinstr) $(brokengasinst)
+KBUILD_CFLAGS  += $(lseinstr) $(brokengasinst)
+# Clang workaround for https://bugs.llvm.org/show_bug.cgi?id=30792
+KBUILD_CFLAGS  += $(call cc-option, -mno-implicit-float, -mgeneral-regs-only)

Thanks,
Mark.