From 638f863dbbc8da16834ee0acc6ac10754f79c486 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 23 Feb 2017 16:03:17 +0000 Subject: [PATCH] arm64/cpufeature: check correct field width when updating sys_val When we're updating a register's sys_val, we use arm64_ftr_value() to find the new field value. We use cpuid_feature_extract_field() to find the new value, but this implicitly assumes a 4-bit field, so we may extract more bits than we mean to for fields like CTR_EL0.L1ip. This affects update_cpu_ftr_reg(), where we may extract erroneous values for ftr_cur and ftr_new. Depending on the additional bits extracted in either case, we may erroneously detect that the value is mismatched, and we'll try to compute a new safe value. Dependent on these extra bits and feature type, arm64_ftr_safe_value() may pessimistically select the always-safe value, or may erroneously choose either the extracted cur or new value as the safe option. The extra bits will subsequently be masked out in arm64_ftr_set_value(), so we may choose a higher value, yet write back a lower one. Fix this by passing the width down explicitly in arm64_ftr_value(), so we always extract the correct amount. Signed-off-by: Mark Rutland Reviewed-by: Suzuki K Poulose Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon --- arch/arm64/include/asm/cpufeature.h | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 4ce82ed3e7c3..05310ad8c5ab 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -184,16 +184,22 @@ static inline u64 arm64_ftr_reg_user_value(const struct arm64_ftr_reg *reg) } static inline int __attribute_const__ -cpuid_feature_extract_field(u64 features, int field, bool sign) +cpuid_feature_extract_field_width(u64 features, int field, int width, bool sign) { return (sign) ? - cpuid_feature_extract_signed_field(features, field) : - cpuid_feature_extract_unsigned_field(features, field); + cpuid_feature_extract_signed_field_width(features, field, width) : + cpuid_feature_extract_unsigned_field_width(features, field, width); +} + +static inline int __attribute_const__ +cpuid_feature_extract_field(u64 features, int field, bool sign) +{ + return cpuid_feature_extract_field_width(features, field, 4, sign); } static inline s64 arm64_ftr_value(const struct arm64_ftr_bits *ftrp, u64 val) { - return (s64)cpuid_feature_extract_field(val, ftrp->shift, ftrp->sign); + return (s64)cpuid_feature_extract_field_width(val, ftrp->shift, ftrp->width, ftrp->sign); } static inline bool id_aa64mmfr0_mixed_endian_el0(u64 mmfr0) -- 2.20.1