feat: add timer calibration

kernel/include/util/cpuid.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <cpuid.h>
+#include <stdint.h>
+
+#include "util/optional.h"
+
+struct cpuid_result_t {
+    uint32_t eax;
+    uint32_t ebx;
+    uint32_t ecx;
+    uint32_t edx;
+};
+
+inline optional<cpuid_result_t> cpuid(uint32_t leaf, uint32_t subleaf = 0) {
+    cpuid_result_t result{};
+    if (__get_cpuid_count(leaf, subleaf, &result.eax, &result.ebx, &result.ecx, &result.edx) == 0) {
+        return {};
+    }
+    return result;
+}