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//! 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
}
|
