//! 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 | |
} |