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    Subject[PATCH AUTOSEL 4.20 099/304] arm64: io: Ensure value passed to __iormb() is held in a 64-bit register
    Date
    From: Will Deacon <will.deacon@arm.com>

    [ Upstream commit 1b57ec8c75279b873639eb44a215479236f93481 ]

    As of commit 6460d3201471 ("arm64: io: Ensure calls to delay routines
    are ordered against prior readX()"), MMIO reads smaller than 64 bits
    fail to compile under clang because we end up mixing 32-bit and 64-bit
    register operands for the same data processing instruction:

    ./include/asm-generic/io.h:695:9: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
    return readb(addr);
    ^
    ./arch/arm64/include/asm/io.h:147:58: note: expanded from macro 'readb'
    ^
    ./include/asm-generic/io.h:695:9: note: use constraint modifier "w"
    ./arch/arm64/include/asm/io.h:147:50: note: expanded from macro 'readb'
    ^
    ./arch/arm64/include/asm/io.h:118:24: note: expanded from macro '__iormb'
    asm volatile("eor %0, %1, %1\n" \
    ^

    Fix the build by casting the macro argument to 'unsigned long' when used
    as an input to the inline asm.

    Reported-by: Nick Desaulniers <nick.desaulniers@gmail.com>
    Reported-by: Nathan Chancellor <natechancellor@gmail.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm64/include/asm/io.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
    index d42d00d8d5b6..ee723835c1f4 100644
    --- a/arch/arm64/include/asm/io.h
    +++ b/arch/arm64/include/asm/io.h
    @@ -117,7 +117,8 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
    */ \
    asm volatile("eor %0, %1, %1\n" \
    "cbnz %0, ." \
    - : "=r" (tmp) : "r" (v) : "memory"); \
    + : "=r" (tmp) : "r" ((unsigned long)(v)) \
    + : "memory"); \
    })

    #define __iowmb() wmb()
    --
    2.19.1
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