1 files changed, 134 insertions, 0 deletions
diff --git a/src/boot.asm b/src/boot.asm
new file mode 100644
index 0000000..011c00f
--- /dev/null
+++ b/src/boot.asm
@@ -0,0 +1,134 @@
+; boot.asm - stage 1
+
+[bits 16]
+[org 0x7C00]
+
+start:
+    xor ax, ax
+    mov ds, ax
+    mov es, ax
+    mov ss, ax
+
+                                    ; clear screen by big scrollup
+    mov ah, 0x06                    ; scrollup function
+    mov al, 0                       ; al contains the n of lines to scroll (0 is clearall)
+    mov bh, 0x07                    ; 'attribute byte' 0x07 is white on black
+    mov cx, 0x0000                  ; upper-left corner
+    mov dx, 0x184F                  ; bottom-right corner
+
+    int 0x10                        ; call
+                                    ; set cursor position back to default
+    mov ah, 0x02                    ; set cur pos function
+                                    ; position parameters:
+    mov bh, 0x00                    ; page number (0)
+    mov dh, 0x00                    ; row
+    mov dl, 0x00                    ; col
+
+    int 0x10                        ; call
+
+    mov si, msg1                    ; print msg1
+    call print_string
+
+    mov ah, 0x02                    ; set cur pos function
+                                    ; position parameters:
+    mov bh, 0x00                    ; page number (0)
+    mov dh, 0x01                    ; row
+    mov dl, 0x00                    ; col
+
+    int 0x10                        ; call
+
+    mov si, msg2                    ; print msg2
+    call print_string
+
+    mov ah, 0x02                    ; set cur pos function
+                                    ; position parameters:
+    mov bh, 0x00                    ; page number (0)
+    mov dh, 0x02                    ; row
+    mov dl, 0x00                    ; col
+
+    int 0x10                        ; call
+
+    mov si, msg3
+    call print_string
+
+    mov ah, 0x02                    ; set cur pos function
+                                    ; position parameters:
+    mov bh, 0x00                    ; page number (0)
+    mov dh, 0x03                    ; row
+    mov dl, 0x00                    ; col
+
+    int 0x10                        ; call
+
+load_stage2:
+    mov ax, 0x0000
+    mov es, ax
+    mov bx, 0x1000
+                                    ; load stage2 from disk - first sector at 0x1000
+    mov bx, 0x1000                  ; load address
+    mov dh, 0
+    mov ch, 0
+    mov cl, 2                        ; sector 2
+    mov al, 20                       ; sectors to read
+    mov ah, 0x02
+
+    int 0x13
+    jc halt
+
+                                    ; GDT for protected mode
+gdt_start:
+    dq 0
+    dq 0x00CF9A000000FFFF           ; code
+    dq 0x00CF92000000FFFF           ; data
+    gdt_end:
+
+gdt_descriptor:
+    dw gdt_end - gdt_start -1
+    dd gdt_start
+
+                                    ; enable protected mode cleanly and transfer to 32-bit stub
+    cli
+    lgdt [gdt_descriptor]
+
+    mov eax, cr0
+    or eax, 1
+    mov cr0, eax
+
+                                    ; far jump reloads CS with selector 0x08 and enters protected mode
+    jmp 0x08:pm_entry
+
+                                    ; 32-bit entry point
+    [bits 32]
+pm_entry:
+                                    ; reload data segment registers with data selector (0x10)
+    mov ax, 0x10
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+
+    mov esp, 0x90000                ; setup stack
+
+    mov eax, 0x1000                 ; jump to linear address 0x1000 (which wloud be where s2.bin was loaded)
+    jmp eax
+
+halt:
+    hlt
+    jmp halt
+
+print_string:
+    lodsb
+    cmp al, 0
+    je .done
+    mov ah, 0x0E
+    int 0x10
+    jmp print_string
+.done:
+    ret
+
+msg1 db `mull_bootloader hath bespoken unto thee:\n`, 0
+msg2 db `\"behold, \'O user! mull_kernel doth now commence its solemn journey!\"\n`, 0
+msg3 db `trying to kernel kernel :3`, 0
+
+times 510-($-$$) db 0
+dw 0xAA55