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detect: Support run-time detection of FEAT_LSE on aarch64 OpenBSD
This also supports run-time detection of FEAT_LSE on aarch64 FreeBSD without "std" feature. This also adds preliminary support for run-time detection of FEAT_LSE2 and FEAT_LSE128. This is currently only used in tests but will be used in the library in the future.
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@@ -61,6 +61,7 @@ metavar | |
| mfence | ||
| mgba | ||
| miscompilation | ||
| mmfr | ||
| moreutils | ||
| mstatus | ||
| nand | ||
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| // Run-time feature detection on aarch64. | ||
| // | ||
| // As of nightly-2023-01-23, is_aarch64_feature_detected doesn't support run-time detection of FEAT_LSE on OpenBSD. | ||
| // https://github.com/rust-lang/stdarch/blob/a0c30f3e3c75adcd6ee7efc94014ebcead61c507/crates/std_detect/src/detect/mod.rs | ||
| // https://github.com/rust-lang/stdarch/pull/1374 | ||
| // | ||
| // Refs: | ||
| // - https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers?lang=en | ||
| // - https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt | ||
| // - https://github.com/rust-lang/stdarch/blob/a0c30f3e3c75adcd6ee7efc94014ebcead61c507/crates/std_detect/src/detect/os/aarch64.rs | ||
| // | ||
| // Supported platforms: | ||
| // - Linux 4.11+ | ||
| // https://github.com/torvalds/linux/commit/77c97b4ee21290f5f083173d957843b615abbff2 | ||
| // - FreeBSD 12.0+ | ||
| // https://github.com/freebsd/freebsd-src/commit/398810619cb32abf349f8de23f29510b2ee0839b | ||
| // - OpenBSD 7.1+ (through sysctl) | ||
| // https://github.com/openbsd/src/commit/d335af936b9d7dd9cf655cae1ce19560c45de6c8 | ||
| // | ||
| // For now, this module is only used on FreeBSD and OpenBSD, because on Linux | ||
| // this approach requires a higher kernel version than Rust supports, and also | ||
| // does not work with qemu-user as of QEMU 7.2. | ||
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| #![cfg_attr( | ||
| any( | ||
| portable_atomic_no_aarch64_target_feature, | ||
| portable_atomic_no_outline_atomics, | ||
| any(target_feature = "lse", portable_atomic_target_feature = "lse") | ||
| ), | ||
| allow(dead_code) | ||
| )] | ||
|
|
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| include!("common.rs"); | ||
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| struct AA64Reg { | ||
| aa64isar0: u64, | ||
| #[cfg(test)] | ||
| aa64mmfr2: u64, | ||
| } | ||
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| #[inline] | ||
| fn _detect(info: &mut CpuInfo) { | ||
| let AA64Reg { | ||
| aa64isar0, | ||
| #[cfg(test)] | ||
| aa64mmfr2, | ||
| } = imp::aa64reg(); | ||
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| // ID_AA64ISAR0_EL1, Instruction Set Attribute Register 0 | ||
| // https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/ID-AA64ISAR0-EL1--AArch64-Instruction-Set-Attribute-Register-0?lang=en | ||
| let atomic = extract(aa64isar0, 23, 20); | ||
| if atomic >= 2 { | ||
| info.set(CpuInfo::HAS_LSE); | ||
| #[cfg(test)] | ||
| { | ||
| if atomic >= 3 { | ||
| info.set(CpuInfo::HAS_LSE128); | ||
| } | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| { | ||
| // ID_AA64MMFR2_EL1, AArch64 Memory Model Feature Register 2 | ||
| // https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/ID-AA64MMFR2-EL1--AArch64-Memory-Model-Feature-Register-2?lang=en | ||
| if extract(aa64mmfr2, 35, 32) >= 1 { | ||
| info.set(CpuInfo::HAS_LSE2); | ||
| } | ||
| } | ||
| } | ||
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| #[inline] | ||
| fn extract(x: u64, high: usize, low: usize) -> u64 { | ||
| (x >> low) & ((1 << (high - low + 1)) - 1) | ||
| } | ||
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| #[cfg(not(target_os = "openbsd"))] | ||
| mod imp { | ||
| #[cfg(not(portable_atomic_no_asm))] | ||
| use core::arch::asm; | ||
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| use super::AA64Reg; | ||
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| #[inline] | ||
| pub(super) fn aa64reg() -> AA64Reg { | ||
| // SAFETY: This is safe on FreeBSD 12.0+. FreeBSD 11 was EoL on 2021-09-30. | ||
| // Note that stdarch has been doing the same thing since before FreeBSD 11 was EoL. | ||
| // https://github.com/rust-lang/stdarch/pull/611 | ||
| unsafe { | ||
| let aa64isar0: u64; | ||
| asm!( | ||
| "mrs {}, ID_AA64ISAR0_EL1", | ||
| out(reg) aa64isar0, | ||
| options(pure, nomem, nostack, preserves_flags) | ||
| ); | ||
| #[cfg(test)] | ||
| let aa64mmfr2: u64; | ||
| #[cfg(test)] | ||
| { | ||
| asm!( | ||
| "mrs {}, ID_AA64MMFR2_EL1", | ||
| out(reg) aa64mmfr2, | ||
| options(pure, nomem, nostack, preserves_flags) | ||
| ); | ||
| } | ||
| AA64Reg { | ||
| aa64isar0, | ||
| #[cfg(test)] | ||
| aa64mmfr2, | ||
| } | ||
| } | ||
| } | ||
| } | ||
| // OpenBSD doesn't trap the mrs instruction, but exposes the system registers through sysctl. | ||
| // https://github.com/openbsd/src/commit/d335af936b9d7dd9cf655cae1ce19560c45de6c8 | ||
| // https://github.com/golang/go/commit/cd54ef1f61945459486e9eea2f016d99ef1da925 | ||
| #[cfg(target_os = "openbsd")] | ||
| mod imp { | ||
| use core::{mem::MaybeUninit, ptr}; | ||
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| use super::AA64Reg; | ||
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| // core::ffi::c_* (except c_void) requires Rust 1.64 | ||
| #[allow(non_camel_case_types)] | ||
| mod ffi { | ||
| pub(crate) use core::ffi::c_void; | ||
| // c_{,u}int is {i,u}32 on non-16-bit architectures | ||
| // https://github.com/rust-lang/rust/blob/1.67.0/library/core/src/ffi/mod.rs#L159-L173 | ||
| pub(crate) type c_int = i32; | ||
| pub(crate) type c_uint = u32; | ||
| // c_size_t is usize | ||
| // https://github.com/rust-lang/rust/blob/1.67.0/library/core/src/ffi/mod.rs#L83-L88 | ||
| pub(crate) type c_size_t = usize; | ||
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| extern "C" { | ||
| // https://man.openbsd.org/sysctl.2 | ||
| // https://github.com/rust-lang/libc/blob/0.2.139/src/unix/bsd/netbsdlike/openbsd/mod.rs#L1817-L1824 | ||
| pub(crate) fn sysctl( | ||
| name: *const c_int, | ||
| name_len: c_uint, | ||
| old_p: *mut c_void, | ||
| old_len_p: *mut c_size_t, | ||
| new_p: *mut c_void, | ||
| new_len: c_size_t, | ||
| ) -> c_int; | ||
| } | ||
|
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| // Defined in sys/sysctl.h. | ||
| // https://github.com/openbsd/src/blob/72ccc03bd11da614f31f7ff76e3f6fce99bc1c79/sys/sys/sysctl.h#L82 | ||
| pub(crate) const CTL_MACHDEP: c_int = 7; | ||
| // Defined in machine/cpu.h. | ||
| // https://github.com/openbsd/src/blob/72ccc03bd11da614f31f7ff76e3f6fce99bc1c79/sys/arch/arm64/include/cpu.h#L25-L40 | ||
| pub(crate) const CPU_ID_AA64ISAR0: c_int = 2; | ||
| #[cfg(test)] | ||
| pub(crate) const CPU_ID_AA64MMFR2: c_int = 7; | ||
| } | ||
|
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| // ID_AA64ISAR0_EL1 and ID_AA64ISAR1_EL1 are supported on OpenBSD 7.1+. | ||
| // https://github.com/openbsd/src/commit/d335af936b9d7dd9cf655cae1ce19560c45de6c8 | ||
| // Others are supported on OpenBSD 7.3+. | ||
| // https://github.com/openbsd/src/commit/c7654cd65262d532212f65123ee3905ba200365c | ||
| // sysctl returns an unsupported error if operation is not supported, | ||
| // so we can safely use this function on older versions of OpenBSD. | ||
| #[inline] | ||
| pub(super) fn aa64reg() -> AA64Reg { | ||
| let aa64isar0 = sysctl64(&[ffi::CTL_MACHDEP, ffi::CPU_ID_AA64ISAR0]).unwrap_or(0); | ||
| #[cfg(test)] | ||
| let aa64mmfr2 = sysctl64(&[ffi::CTL_MACHDEP, ffi::CPU_ID_AA64MMFR2]).unwrap_or(0); | ||
| AA64Reg { | ||
| aa64isar0, | ||
| #[cfg(test)] | ||
| aa64mmfr2, | ||
| } | ||
| } | ||
|
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| #[inline] | ||
| fn sysctl64(mib: &[ffi::c_int]) -> Option<u64> { | ||
| const OUT_LEN: ffi::c_size_t = core::mem::size_of::<u64>() as ffi::c_size_t; | ||
| let mut out = MaybeUninit::<u64>::uninit(); | ||
| let mut out_len = OUT_LEN; | ||
| #[allow(clippy::undocumented_unsafe_blocks)] // TODO | ||
| #[allow(clippy::cast_possible_truncation)] | ||
| let res = unsafe { | ||
| ffi::sysctl( | ||
| mib.as_ptr(), | ||
| mib.len() as ffi::c_uint, | ||
| out.as_mut_ptr() as *mut ffi::c_void, | ||
| &mut out_len, | ||
| ptr::null_mut(), | ||
| 0, | ||
| ) | ||
| }; | ||
| if res == -1 || out_len != OUT_LEN { | ||
| return None; | ||
| } | ||
| // SAFETY: we've checked that sysctl was successful and `out` was filled. | ||
| Some(unsafe { out.assume_init() }) | ||
| } | ||
| } | ||
|
|
||
| #[allow(clippy::undocumented_unsafe_blocks)] | ||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
|
|
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| #[test] | ||
| fn test_aa64reg() { | ||
| let AA64Reg { aa64isar0, aa64mmfr2 } = imp::aa64reg(); | ||
| std::eprintln!("aa64isar0={}", aa64isar0); | ||
| std::eprintln!("aa64mmfr2={}", aa64mmfr2); | ||
| if detect().test(CpuInfo::HAS_LSE) { | ||
| let atomic = extract(aa64isar0, 23, 20); | ||
| if detect().test(CpuInfo::HAS_LSE128) { | ||
| assert_eq!(atomic, 3); | ||
| } else { | ||
| assert_eq!(atomic, 2); | ||
| } | ||
| } | ||
| if detect().test(CpuInfo::HAS_LSE2) { | ||
| assert_eq!(extract(aa64mmfr2, 35, 32), 1); | ||
| } | ||
| } | ||
| } |
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