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 10:50:08 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH 07/15] arm64: use -mno-implicit-float instead of -mgeneral-regs-only

I think this bug was fixed upstream in LLVM.  Do we still want to take
this workaround?

On Fri, Nov 3, 2017 at 10:11 AM, Sami Tolvanen <samitolvanen@...gle.com> 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>
> ---
>  arch/arm64/Makefile | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 939b310913cf..eb6f3c9ec6cb 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -45,7 +45,13 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable)
>    endif
>  endif
>
> -KBUILD_CFLAGS  += -mgeneral-regs-only $(lseinstr) $(brokengasinst)
> +ifeq ($(cc-name),clang)
> +# This is a workaround for https://bugs.llvm.org/show_bug.cgi?id=30792.
> +KBUILD_CFLAGS  += -mno-implicit-float
> +else
> +KBUILD_CFLAGS  += -mgeneral-regs-only
> +endif
> +KBUILD_CFLAGS  += $(lseinstr) $(brokengasinst)
>  KBUILD_CFLAGS  += -fno-asynchronous-unwind-tables
>  KBUILD_CFLAGS  += $(call cc-option, -mpc-relative-literal-loads)
>  KBUILD_AFLAGS  += $(lseinstr) $(brokengasinst)
> --
> 2.15.0.403.gc27cc4dac6-goog
>



-- 
Thanks,
~Nick Desaulniers