oaknut: feature_detect: Support NetBSD

include/oaknut/feature_detection/feature_detection.hpp

@@ -15,6 +15,10 @@
 #    define OAKNUT_CPU_FEATURE_DETECTION 1
 #    define OAKNUT_SUPPORTS_READING_ID_REGISTERS 1
 #    include "oaknut/feature_detection/feature_detection_linux.hpp"
+#elif defined(__NetBSD__)
+#    define OAKNUT_CPU_FEATURE_DETECTION 1
+#    define OAKNUT_SUPPORTS_READING_ID_REGISTERS 2
+#    include "oaknut/feature_detection/feature_detection_netbsd.hpp"
 #elif defined(__OpenBSD__)
 #    define OAKNUT_CPU_FEATURE_DETECTION 1
 #    define OAKNUT_SUPPORTS_READING_ID_REGISTERS 1

include/oaknut/feature_detection/feature_detection_freebsd.hpp

@@ -24,7 +24,7 @@ namespace oaknut {
 
 namespace detail {
 
-unsigned long getauxval(int aux)
+inline unsigned long getauxval(int aux)
 {
     unsigned long result = 0;
     if (::elf_aux_info(aux, &result, static_cast<int>(sizeof result)) == 0) {

include/oaknut/feature_detection/feature_detection_netbsd.hpp

@@ -0,0 +1,81 @@
+// SPDX-FileCopyrightText: Copyright (c) 2023 merryhime <https://mary.rs>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <string>
+
+#include <aarch64/armreg.h>
+#include <sys/param.h>
+#include <sys/sysctl.h>
+
+#include "oaknut/feature_detection/cpu_feature.hpp"
+#include "oaknut/feature_detection/feature_detection_hwcaps.hpp"
+#include "oaknut/feature_detection/feature_detection_idregs.hpp"
+#include "oaknut/feature_detection/id_registers.hpp"
+
+namespace oaknut {
+
+inline std::optional<id::IdRegisters> read_id_registers(std::size_t core_index)
+{
+    const std::string path = "machdep.cpu" + std::to_string(core_index) + ".cpu_id";
+
+    aarch64_sysctl_cpu_id id;
+    std::size_t id_len = sizeof id;
+
+    if (sysctlbyname(path.c_str(), &id, &id_len, nullptr, 0) < 0)
+        return std::nullopt;
+
+    return id::IdRegisters{
+        id.ac_midr,
+        id::Pfr0Register{id.ac_aa64pfr0},
+        id::Pfr1Register{id.ac_aa64pfr1},
+        id::Pfr2Register{0},
+        id::Zfr0Register{id.ac_aa64zfr0},
+        id::Smfr0Register{0},
+        id::Isar0Register{id.ac_aa64isar0},
+        id::Isar1Register{id.ac_aa64isar1},
+        id::Isar2Register{0},
+        id::Isar3Register{0},
+        id::Mmfr0Register{id.ac_aa64mmfr0},
+        id::Mmfr1Register{id.ac_aa64mmfr1},
+        id::Mmfr2Register{id.ac_aa64mmfr2},
+        id::Mmfr3Register{0},
+        id::Mmfr4Register{0},
+    };
+}
+
+inline std::size_t get_core_count()
+{
+    int result = 0;
+    size_t result_size = sizeof(result);
+    const std::array<int, 2> mib{CTL_HW, HW_NCPU};
+    if (sysctl(mib.data(), mib.size(), &result, &result_size, nullptr, 0) < 0)
+        return 0;
+    return result;
+}
+
+inline CpuFeatures detect_features()
+{
+    std::optional<CpuFeatures> result;
+
+    const std::size_t core_count = get_core_count();
+    for (std::size_t core_index = 0; core_index < core_count; core_index++) {
+        if (const std::optional<id::IdRegisters> id_regs = read_id_registers(core_index)) {
+            const CpuFeatures current_features = detect_features_via_id_registers(*id_regs);
+            if (result) {
+                result = *result & current_features;
+            } else {
+                result = current_features;
+            }
+        }
+    }
+
+    return result.value_or(CpuFeatures{});
+}
+
+}  // namespace oaknut