From: Mark Brown Date: Mon, 7 Mar 2022 18:08:59 +0000 (+0000) Subject: arm64: cpufeature: Warn if we attempt to read a zero width field X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f2c281204b47309534f26dc63cee2a130c2b497b;p=linux.git arm64: cpufeature: Warn if we attempt to read a zero width field Add a WARN_ON_ONCE() when extracting a field if no width is specified. This should never happen outside of development since it will be triggered with or without the feature so long as the relevant ID register is present. If the warning triggers hope that the field was the standard 4 bits wide and soldier on. Suggested-by: Marc Zyngier Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20220307180900.3045812-1-broonie@kernel.org Signed-off-by: Will Deacon --- diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 2728abd9cae4b..2b407fbccdfb3 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -577,6 +577,8 @@ static inline u64 arm64_ftr_reg_user_value(const struct arm64_ftr_reg *reg) static inline int __attribute_const__ cpuid_feature_extract_field_width(u64 features, int field, int width, bool sign) { + if (WARN_ON_ONCE(!width)) + width = 4; return (sign) ? cpuid_feature_extract_signed_field_width(features, field, width) : cpuid_feature_extract_unsigned_field_width(features, field, width);