Add an MSR utility struct

kernel/include/misc/MSR.h

@@ -0,0 +1,18 @@
+#pragma once
+#include <stdint.h>
+
+#define IA32_EFER_MSR 0xC0000080
+
+struct MSR
+{
+    void write(uint64_t value);
+    uint64_t read();
+
+    MSR(uint32_t msr_num);
+
+    static void write_to(uint32_t msr_num, uint64_t value);
+    static uint64_t read_from(uint32_t msr_num);
+
+  private:
+    uint32_t m_msr_num;
+};

kernel/src/misc/MSR.cpp

@@ -0,0 +1,30 @@
+#include "misc/MSR.h"
+
+void MSR::write_to(uint32_t msr_num, uint64_t value)
+{
+    uint32_t lo = value & 0xFFFFFFFF;
+    uint32_t hi = value << 32;
+    asm volatile("wrmsr" : : "a"(lo), "d"(hi), "c"(msr_num));
+}
+
+uint64_t MSR::read_from(uint32_t msr_num)
+{
+    uint32_t lo;
+    uint32_t hi;
+    asm volatile("rdmsr" : "=a"(lo), "=d"(hi) : "c"(msr_num));
+    return (uint64_t)hi << 32 | (uint64_t)lo;
+}
+
+void MSR::write(uint64_t value)
+{
+    write_to(m_msr_num, value);
+}
+
+uint64_t MSR::read()
+{
+    return read_from(m_msr_num);
+}
+
+MSR::MSR(uint32_t msr_num) : m_msr_num(msr_num)
+{
+}