| //! Run-time feature detection for RISC-V on Linux. |
| |
| use super::auxvec; |
| use crate::detect::{bit, cache, Feature}; |
| |
| /// Read list of supported features from the auxiliary vector. |
| pub(crate) fn detect_features() -> cache::Initializer { |
| let mut value = cache::Initializer::default(); |
| let enable_feature = |value: &mut cache::Initializer, feature, enable| { |
| if enable { |
| value.set(feature as u32); |
| } |
| }; |
| let enable_features = |value: &mut cache::Initializer, feature_slice: &[Feature], enable| { |
| if enable { |
| for feature in feature_slice { |
| value.set(*feature as u32); |
| } |
| } |
| }; |
| |
| // The values are part of the platform-specific [asm/hwcap.h][hwcap] |
| // |
| // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/riscv/include/asm/hwcap.h |
| let auxv = auxvec::auxv().expect("read auxvec"); // should not fail on RISC-V platform |
| enable_feature( |
| &mut value, |
| Feature::a, |
| bit::test(auxv.hwcap, (b'a' - b'a').into()), |
| ); |
| enable_feature( |
| &mut value, |
| Feature::c, |
| bit::test(auxv.hwcap, (b'c' - b'a').into()), |
| ); |
| enable_features( |
| &mut value, |
| &[Feature::d, Feature::f, Feature::zicsr], |
| bit::test(auxv.hwcap, (b'd' - b'a').into()), |
| ); |
| enable_features( |
| &mut value, |
| &[Feature::f, Feature::zicsr], |
| bit::test(auxv.hwcap, (b'f' - b'a').into()), |
| ); |
| let has_i = bit::test(auxv.hwcap, (b'i' - b'a').into()); |
| // If future RV128I is supported, implement with `enable_feature` here |
| #[cfg(target_pointer_width = "64")] |
| enable_feature(&mut value, Feature::rv64i, has_i); |
| #[cfg(target_pointer_width = "32")] |
| enable_feature(&mut value, Feature::rv32i, has_i); |
| #[cfg(target_pointer_width = "32")] |
| enable_feature( |
| &mut value, |
| Feature::rv32e, |
| bit::test(auxv.hwcap, (b'e' - b'a').into()), |
| ); |
| enable_feature( |
| &mut value, |
| Feature::h, |
| bit::test(auxv.hwcap, (b'h' - b'a').into()), |
| ); |
| enable_feature( |
| &mut value, |
| Feature::m, |
| bit::test(auxv.hwcap, (b'm' - b'a').into()), |
| ); |
| // FIXME: Auxvec does not show supervisor feature support, but this mode may be useful |
| // to detect when Rust is used to write Linux kernel modules. |
| // These should be more than Auxvec way to detect supervisor features. |
| |
| value |
| } |