Add rdmsr/wrmsr to io.cpp

src/kernel/io.cpp

@@ -14,3 +14,19 @@ outb(uint16_t port, uint8_t val)
 	__asm__ __volatile__ ( "outb %0, %1" :: "a"(val), "Nd"(port) );
 }
 
+uint64_t
+rdmsr(uint64_t addr)
+{
+	uint32_t low, high;
+	__asm__ __volatile__ ("rdmsr" : "=a"(low), "=d"(high) : "c"(addr));
+	return (static_cast<uint64_t>(high) << 32) | low;
+}
+
+void
+wrmsr(uint64_t addr, uint64_t value)
+{
+	uint32_t low = value & 0xffffffff;
+	uint32_t high = value >> 32;
+	__asm__ __volatile__ ("wrmsr" :: "c"(addr), "a"(low), "d"(high));
+}
+

src/kernel/io.h

@@ -14,6 +14,16 @@ uint8_t inb(uint16_t port);
 /// \arg val   The byte to write
 void outb(uint16_t port, uint8_t val);
 
+/// Read the value of a MSR
+/// \arg addr   The MSR address
+/// \returns    The current value of the MSR
+uint64_t rdmsr(uint64_t addr);
+
+/// Write to a MSR
+/// \arg addr   The MSR address
+/// \arg value  The value to write
+void wrmsr(uint64_t addr, uint64_t value);
+
 }
 
 const uint16_t COM1 = 0x03f8;