linux-kernel - [PATCH 3/3] arm64: use -mno-implicit-float instead of -mgeneral-regs-only

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Message-Id: <20171129000011.55235-4-samitolvanen@google.com>
Date:   Tue, 28 Nov 2017 16:00:11 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Alex Matveev <alxmtvv@...il.com>, Andi Kleen <ak@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Matthias Kaehlcke <mka@...omium.org>
Cc:     Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 3/3] arm64: use -mno-implicit-float instead of -mgeneral-regs-only

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>
[added clang-ifversion to enable the workaround only for clang <6.0]
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 arch/arm64/Makefile | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b35788c909f1..d2efb5a0212f 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -49,7 +49,10 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable)
   endif
 endif
 
-KBUILD_CFLAGS	+= -mgeneral-regs-only $(lseinstr) $(brokengasinst)
+# This is a workaround for https://bugs.llvm.org/show_bug.cgi?id=30792.
+KBUILD_CFLAGS	+= $(call clang-ifversion, -lt, 0600, -mno-implicit-float, -mgeneral-regs-only)
+
+KBUILD_CFLAGS	+= $(lseinstr) $(brokengasinst)
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS	+= $(call cc-option, -mpc-relative-literal-loads)
 KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst)
-- 
2.15.0.417.g466bffb3ac-goog