Cleanup and commenting

src/kernel/cpu/cpu.c

@@ -9,9 +9,10 @@ struct cpu __seg_gs *cpu = 0;
 
 void cpu_init()
 {
+  // Set up cpu struct
   struct cpu *c = P2V(pmm_calloc());
   c->cpu = c;
-  write_msr(0xc0000102, (uint64_t)c);
+  write_msr(KERNEL_GS_BASE, (uint64_t)c);
   asm("swapgs");
 
   interrupt_init();

src/kernel/cpu/registers.S

@@ -49,7 +49,6 @@ read_msr:
   shl rdx, 32
   add rax, rdx
   ret
-
 .global write_msr
 write_msr:
   mov rcx, rdi

src/kernel/include/cpu.h

@@ -26,5 +26,8 @@ uint64_t read_cr3();
 void write_cr3(uint64_t);
 uint64_t read_cr4();
 
+// Model Specific Registers
+// Functions defined in cpu/registers.S
 void write_msr(uint64_t reg, uint64_t value);
 uint64_t read_msr(uint64_t reg);
+#define KERNEL_GS_BASE 0xC0000102