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    Subject[PATCH 1/5] arm64: cpufeature: Add helpers for extracting unsigned values
    Date
    The cpuid_feature_extract_field() extracts the feature value
    as a signed integer. This could be problematic for features
    whose values are unsigned. e.g, ID_AA64DFR0_EL1:BRPs. Add
    an unsigned variant for the unsigned fields.

    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Reported-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
    ---
    arch/arm64/include/asm/cpufeature.h | 12 ++++++++++++
    1 file changed, 12 insertions(+)

    diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
    index 11d5bb0f..7a16102 100644
    --- a/arch/arm64/include/asm/cpufeature.h
    +++ b/arch/arm64/include/asm/cpufeature.h
    @@ -123,6 +123,18 @@ cpuid_feature_extract_field(u64 features, int field)
    return cpuid_feature_extract_field_width(features, field, 4);
    }

    +static inline unsigned int __attribute_const__
    +cpuid_feature_extract_unsigned_field_width(u64 features, int field, int width)
    +{
    + return (u64)(features << (64 - width - field)) >> (64 - width);
    +}
    +
    +static inline unsigned int __attribute_const__
    +cpuid_feature_extract_unsigned_field(u64 features, int field)
    +{
    + return cpuid_feature_extract_unsigned_field_width(features, field, 4);
    +}
    +
    static inline u64 arm64_ftr_mask(struct arm64_ftr_bits *ftrp)
    {
    return (u64)GENMASK(ftrp->shift + ftrp->width - 1, ftrp->shift);
    --
    1.7.9.5


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