Began moving to C. (No C yet)

If you want to build the assembly version, run the buildAsm.sh script Currently just setting up the bootloader.
2026-11-04 02:23:10 +00:00 · 2024-01-02 14:40:32 +01:00
parent 845e33479a
commit 726247a4f2
15 changed files with 365 additions and 74 deletions
@@ -0,0 +1,98 @@
+[org 0x7c00]
+[bits 16]
+[global start]
+
+start:
+    ; Setup
+    xor ax, ax
+    mov es, ax
+    mov ds, ax
+    mov bp, 0x7c00
+    mov sp, bp
+
+    ; Save drive number
+    mov byte [driveNumber], dl
+
+    ; Print boot message
+    mov si, bootMsg
+    call print
+    mov dl, byte [driveNumber]
+    call printHex
+    mov si, newline
+    call print
+
+    ; Read filetable from disk
+    mov bx, FILETAB_LOC ; Filetable location in memory
+    mov es, bx
+    xor bx, bx
+
+    mov ah, 2           ; Read from disk
+    mov al, 1           ; Read 1 sector (512B)
+
+    mov dl, byte [driveNumber] ; Drive number
+    mov ch, 0           ; Cylinder
+    mov dh, 0           ; Head
+    mov cl, 2           ; Sector
+    int 0x13            ; INT 0x13 - Disk operations
+
+    jc readFail         ; CF will be set if the read fails
+
+    ; Read filetable from disk
+    mov bx, KERNEL_LOC ; Filetable location in memory
+    mov es, bx
+    xor bx, bx
+
+    mov ah, 2           ; Read from disk
+    mov al, 4           ; Read 4 sectors (2kB)
+
+    mov dl, byte [driveNumber] ; Drive number
+    mov ch, 0           ; Cylinder
+    mov dh, 0           ; Head
+    mov cl, 3           ; Sector
+    int 0x13            ; INT 0x13 - Disk operations
+
+    jc readFail         ; CF will be set if the read fails
+
+    ; Setup segmentation
+    mov ax, KERNEL_LOC
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+
+    ; Setup stack
+    mov bp, 0xffff
+    mov sp, bp
+    mov ax, 0x9000
+    mov ss, ax
+
+    mov bl, byte [driveNumber]
+
+    ; Setup video mode
+    mov ax, 0x0003
+    int 0x10
+    mov ah, 0x0b
+    mov bx, 0x0001
+    int 0x10
+
+    ; Far jump to the kernel (never returns)
+    jmp KERNEL_LOC:0x0000
+
+readFail:
+    mov si, diskErrorMsg
+    call print
+    cli
+    hlt
+
+%include "./src/lib/print.asm"
+
+driveNumber: db 0
+
+bootMsg: db ENDL, "Booting kern.", ENDL, "Booting from drive ", 0
+diskErrorMsg: db "Disk Error!", ENDL, 0
+
+FILETAB_LOC equ 0x1000
+KERNEL_LOC equ 0x2000
+
+times 510-($-$$) db 0
+dw 0xaa55