identity map 1gb

src/boot.asm

@@ -1,4 +1,5 @@
 global _start
+extern kernel_main
 
 %define FLAGS       0b10
 %define MAGIC       0x1BADB002
@@ -83,7 +84,23 @@ section .text
         or eax, 1 << 5
         mov cr4, eax
 
-        ; todo(nub31): Set up page tables
+        ; pml4[0] -> pdpt
+        mov eax, pdpt
+        or eax, 0x03
+        mov [pml4], eax
+        ; pdpt[0] -> pd
+        mov eax, pd
+        or eax, 0x03
+        mov [pdpt], eax
+        ; Fill pd with 2MB entries
+        mov edi, pd
+        mov eax, 0x83
+        mov ecx, 512
+    .setup_pd:
+        mov [edi], eax
+        add eax, 0x200000
+        add edi, 8
+        loop .setup_pd
 
         ; Load cr3 with the address of pml4
         mov eax, pml4
@@ -97,7 +114,7 @@ section .text
         or eax, 1 << 8
         wrmsr
 
-        ; Enable paging bt setting bit 31 in cr0 to 1
+        ; Enable paging by setting bit 31 in cr0 to 1
         mov eax, cr0
         or eax, 1 << 31
         mov cr0, eax
@@ -116,7 +133,14 @@ section .text
 section .text
     bits 64
     long_mode:
-        cli
+        ; Clear segment registers in long mode
+        xor ax, ax
+        mov ds, ax
+        mov es, ax
+        mov fs, ax
+        mov gs, ax
+        mov ss, ax
+        call kernel_main
     .hang:
         hlt
         jmp .hang