linux-kernel - [PATCH] arm64: lse: fix LSE atomics with LLVM's integrated assembler

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Message-Id: <20191007201452.208067-1-samitolvanen@google.com>
Date:   Mon,  7 Oct 2019 13:14:52 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Andrew Murray <andrew.murray@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH] arm64: lse: fix LSE atomics with LLVM's integrated assembler

Unlike gcc, clang considers each inline assembly block to be independent
and therefore, when using the integrated assembler for inline assembly,
any preambles that enable features must be repeated in each block.

Instead of changing all inline assembly blocks that use LSE, this change
adds -march=armv8-a+lse to KBUILD_CFLAGS, which works with both clang
and gcc.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 arch/arm64/Makefile          | 2 ++
 arch/arm64/include/asm/lse.h | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 84a3d502c5a5..7a7c0cb8ed60 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -36,6 +36,8 @@ lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
 ifeq ($(CONFIG_ARM64_LSE_ATOMICS), y)
   ifeq ($(lseinstr),)
 $(warning LSE atomics not supported by binutils)
+  else
+KBUILD_CFLAGS	+= -march=armv8-a+lse
   endif
 endif
 
diff --git a/arch/arm64/include/asm/lse.h b/arch/arm64/include/asm/lse.h
index 80b388278149..8603a9881529 100644
--- a/arch/arm64/include/asm/lse.h
+++ b/arch/arm64/include/asm/lse.h
@@ -14,8 +14,6 @@
 #include <asm/atomic_lse.h>
 #include <asm/cpucaps.h>
 
-__asm__(".arch_extension	lse");
-
 extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];
 extern struct static_key_false arm64_const_caps_ready;
 
-- 
2.23.0.581.g78d2f28ef7-goog