[PATCH 1/5] arm64: cpufeature: Add helpers for extracting unsigned values

Suzuki K. Poulose
2015-11-18T17:09:19Z

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