1 files changed, 82 insertions, 30 deletions

diff --git a/src/arch/amd64/boot.S b/src/arch/amd64/boot.S
index fc580fb..9771fe2 100644
--- a/src/arch/amd64/boot.S
+++ b/src/arch/amd64/boot.S
@@ -3,18 +3,6 @@ extern kmain
 extern amd64_shim
 bits 32
 
-; base, limit, access, flags
-%macro gdt_entry 4
-	db %2 & 0xff
-	db (%2 >> 8) & 0xff
-	db %1 & 0xff
-	db (%1 >> 8) & 0xff
-	db (%1 >> 16) & 0xff
-	db %3
-	db ((%2 >> 16) & 0x0f) | (%4 << 4)
-	db (%1 >> 24) & 0xff
-%endmacro
-
 section .multiboot
 align 8
 mb_start:
@@ -38,33 +26,97 @@ stack_end:
 
 section .rodata
 align 16
-gdt_start:
-gdt_entry 0, 0, 0, 0
-gdt_entry 0, 0xFFFFF, 0x9A, 0xC
-gdt_entry 0, 0xFFFFF, 0x92, 0xC
-gdt_end:
-gdt_descriptor:
-	dw gdt_end - gdt_start - 1
-	dd gdt_start
-
+; Access bits
+PRESENT        equ 1 << 7
+NOT_SYS        equ 1 << 4
+EXEC           equ 1 << 3
+DC             equ 1 << 2
+RW             equ 1 << 1
+ACCESSED       equ 1 << 0
+ 
+; Flags bits
+GRAN_4K       equ 1 << 7
+SZ_32         equ 1 << 6
+LONG_MODE     equ 1 << 5
+ 
+GDT:
+    .Null: equ $ - GDT
+        dq 0
+    .Code: equ $ - GDT
+        dd 0xFFFF                                   ; Limit & Base (low, bits 0-15)
+        db 0                                        ; Base (mid, bits 16-23)
+        db PRESENT | NOT_SYS | EXEC | RW            ; Access
+        db GRAN_4K | LONG_MODE | 0xF                ; Flags & Limit (high, bits 16-19)
+        db 0                                        ; Base (high, bits 24-31)
+    .Data: equ $ - GDT
+        dd 0xFFFF                                   ; Limit & Base (low, bits 0-15)
+        db 0                                        ; Base (mid, bits 16-23)
+        db PRESENT | NOT_SYS | RW                   ; Access
+        db GRAN_4K | SZ_32 | 0xF                    ; Flags & Limit (high, bits 16-19)
+        db 0                                        ; Base (high, bits 24-31)
+    .TSS: equ $ - GDT
+        dd 0x00000068
+        dd 0x00CF8900
+    .Pointer:
+        dw $ - GDT - 1
+        dq GDT
 
 section .text
 align 8
 start:
 	cli
-	lgdt [gdt_descriptor]
-	jmp 0x08:after_lgdt
-after_lgdt:
-	mov ax, 0x10
-	mov ds, ax
-	mov ss, ax
-	mov es, ax
-	mov fs, ax
-	mov gs, ax
 	mov esp, stack_end
 	mov ebp, stack_end
+
 	push ebx
+
+	mov edi, 0x1000
+	mov cr3, edi
+	xor eax, eax
+	mov ecx, 4096
+	rep stosd
+	mov edi, cr3
+
+	mov DWORD [edi], 0x2003      ; Set the uint32_t at the destination index to 0x2003.
+	add edi, 0x1000              ; Add 0x1000 to the destination index.
+	mov DWORD [edi], 0x3003      ; Set the uint32_t at the destination index to 0x3003.
+	add edi, 0x1000              ; Add 0x1000 to the destination index.
+	mov DWORD [edi], 0x4003      ; Set the uint32_t at the destination index to 0x4003.
+	add edi, 0x1000              ; Add 0x1000 to the destination index.
+
+	mov ebx, 0x00000003          ; Set the B-register to 0x00000003.
+	mov ecx, 512                 ; Set the C-register to 512.
+ 
+.SetEntry:
+	mov DWORD [edi], ebx         ; Set the uint32_t at the destination index to the B-register.
+	add ebx, 0x1000              ; Add 0x1000 to the B-register.
+	add edi, 8                   ; Add eight to the destination index.
+	loop .SetEntry               ; Set the next entry.
+
+	;push ebx                ; Call our function to set up basic paging
+	;call amd64_shim
+
+
+	mov eax, cr4            ; Enable the PAE bit
+	or eax, 1 << 5
+	mov cr4, eax
+
+	mov ecx, 0xC0000080     ; Enable long mode
+	rdmsr
+	or eax, 1 << 8
+	wrmsr
+
+	mov eax, cr0            ; Enable paging
+	or eax, 1 << 31
+	mov cr0, eax
+
+	lgdt [GDT.Pointer]
+	jmp GDT.Code:code64
+
+	bits 64
+code64:
 	call amd64_shim
+	push rax
 	call kmain
 	cli
 halt: