linux-kernel - [PATCH] arm64: io: specify asm operand width for _

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Message-Id: <20181129041912.5918-1-nick.desaulniers@gmail.com>
Date:   Wed, 28 Nov 2018 20:19:10 -0800
From:   Nick Desaulniers <nick.desaulniers@...il.com>
To:     will.deacon@....com
Cc:     natechancellor@...il.com,
        Nick Desaulniers <nick.desaulniers@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jens Axboe <axboe@...nel.dk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: io: specify asm operand width for __iormb()

Fixes the warning produced from Clang:
./include/asm-generic/io.h:711:9: warning: value size does not match
register size specified by the constraint and modifier
[-Wasm-operand-widths]
        return readl(addr);
               ^
./arch/arm64/include/asm/io.h:149:58: note: expanded from macro 'readl'
                                                          ^
./include/asm-generic/io.h:711:9: note: use constraint modifier "w"
./arch/arm64/include/asm/io.h:149:50: note: expanded from macro 'readl'
                                                  ^
./arch/arm64/include/asm/io.h:118:25: note: expanded from macro '__iormb'
        asm volatile("eor       %w0, %1, %1\n" \
                                     ^
Though we disable Clang's integrated assembler with -no-integrated-as,
it still tries to do some validation of assembler constraints.

While __iormb() is type agnostic to operand widths for argument v, its
lone use is to zero'd out via eor (exclusive or).

Fixes commit 6460d3201471 ("arm64: io: Ensure calls to delay routines
are ordered against prior readX()")
Link: https://github.com/ClangBuiltLinux/continuous-integration/issues/78
Suggested-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
---
Side note: is it not correct to cite SHAs from linux-next in "Fixes
commit ..." lines? I guess we can drop it.

Link to regression build:
https://travis-ci.com/ClangBuiltLinux/continuous-integration/builds/92799938

Link to build w/ this patch:
https://travis-ci.com/ClangBuiltLinux/continuous-integration/builds/92935901


 arch/arm64/include/asm/io.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index d42d00d8d5b6..dbdebf81162b 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -115,7 +115,7 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
 	 * later instructions. This ensures that a subsequent call to	\
 	 * udelay() will be ordered due to the ISB in get_cycles().	\
 	 */								\
-	asm volatile("eor	%0, %1, %1\n"				\
+	asm volatile("eor	%0, %x1, %x1\n"				\
 		     "cbnz	%0, ."					\
 		     : "=r" (tmp) : "r" (v) : "memory");		\
 })
-- 
2.17.1