diff options
Diffstat (limited to 'src/bootloader/loader.asm')
| -rw-r--r-- | src/bootloader/loader.asm | 444 |
1 files changed, 0 insertions, 444 deletions
diff --git a/src/bootloader/loader.asm b/src/bootloader/loader.asm deleted file mode 100644 index 28e4562..0000000 --- a/src/bootloader/loader.asm +++ /dev/null @@ -1,444 +0,0 @@ -BITS 16 -ORG 0x7C00 - -; Save the boot drive id -mov [bootDriveID], dl - -jmp start - -; The print function -print: - mov ah, 0x0E - xor bh, bh - .print_L: - lodsb - test al, al - jz .print_end - int 0x10 - jmp .print_L - .print_end: - ret - -bootDriveID: db 0 - -dapack: - dapack_size: db 0x10 - dapack_null: db 0x00 - dapack_blkcount: dw 0x0001 - dapack_boffset: dw 0x9000 - dapack_bsegment: dw 0x0000 - dapack_start: dd 0x00000000 - dapack_upper_lba_bits: dd 0x00000000 - -readsector: - mov dword [dapack_start], eax - mov ah, 0x42 - mov dl, [bootDriveID] - xor bx, bx - mov ds, bx - mov si, dapack - int 0x13 - ret - -filenameLength dw 1 -filename dw 1 - -findfile: - mov bx, [esp+2] - mov ax, [esp+4] - mov [filenameLength], ax - mov ax, [esp+6] - mov [filename], ax - - .findfile_L: - mov al, [bx] - - test al, al - jz .findfile_notfound - - mov ah, [bx+32] - cmp ah, byte [filenameLength] - jnz .findfile_keep - - call findfile_check - test ax, ax - jz findfile_found - - .findfile_keep: - mov al, [bx] - xor ah, ah - add bx, ax - jmp .findfile_L - - .findfile_notfound: - xor ax, ax - inc ax - ret - - findfile_check: - pusha - add bx, 33 - mov ax, bx - - xor cx, cx - .findfile_check_L: - mov bx, [filename] - add bx, cx - mov dh, [bx] - mov bx, ax - add bx, cx - mov dl, [bx] - cmp dh, dl - jnz .findfile_check_fail - - inc cx - cmp cx, word [filenameLength] - jz .findfile_check_success - jmp .findfile_check_L - - .findfile_check_fail: - popa - xor ax, ax - inc ax - ret - .findfile_check_success: - popa - xor ax, ax - ret - - findfile_found: - xor ax, ax - ret - -LOAD_PVD: - mov eax, 0x10 - PVD_L: - call readsector - mov bx, [dapack_boffset] - mov bl, [bx] - cmp bl, 0x01 - jz PVD_FOUND - inc eax - jmp PVD_L - PVD_FOUND: - ret - -checkA20: - ; Stolen from https://wiki.osdev.org/A20_Line - pushf - push ds - push es - push di - push si - cli - xor ax, ax - mov es, ax - not ax - mov ds, ax - mov di, 0x0500 - mov si, 0x0510 - mov al, byte [es:di] - push ax - mov al, byte [ds:si] - push ax - mov byte [es:di], 0x00 - mov byte [ds:si], 0xFF - cmp byte [es:di], 0xFF - pop ax - mov byte [ds:si], al - pop ax - mov byte [es:di], al - mov ax, 0 - jz checkA20_exit - mov ax, 1 - checkA20_exit: - pop si - pop di - pop es - pop ds - popf - ret - -welcome db "Melvix", 0x0A, 0x0D, 0x00 -nolba db "BIOS lacks support for LBA addressing.", 0x00 -noboot db "Boot directory could not be found.", 0x00 -noa20 db "A20 could not be enabled.", 0 -loading db "Loading kernel...", 0x0A, 0x0D, 0x00 -nokernel db "kernel.bin could not be found!", 0 -booting db "Booting...", 0x0A, 0x0D, 0x00 -nomem db "BIOS does not support memory detection!", 0 -memno20 db "BIOS returns memory detection with 24 bytes. This has never been seen!", 0 - -start: - ; Check if LBA is supported by the BIOS. - mov ah, 0x41 - mov bx, 0x55AA - int 0x13 - jc lba_not_supported - cmp bx, 0xAA55 - jnz lba_not_supported - - call checkA20 - test ax, ax - jnz A20_ENABLED - - in al, 0x92 - or al, 2 - out 0x92, al - - call checkA20 - test ax, ax - jnz A20_ENABLED - - mov si, noa20 - call print - jmp $ - -A20_ENABLED: - ; Inspired by https://wiki.osdev.org/Unreal_Mode - cli - push ds - lgdt [gdtinfo] - - mov eax, cr0 - or al, 1 - mov cr0, eax - - jmp $+2 - - mov bx, 0x08 - mov ds, bx - - and al, 0xFE - mov cr0, eax - pop ds - - mov si, loading - call print - - call LOAD_PVD - - mov bx, 0x9000 - add bx, 156 - add bx, 2 - mov eax, dword [bx] - call readsector - - push boot - push boot_len - push 0x9000 - call findfile - add esp, 6 - test ax, ax - jz continue_BOOT - - mov si, noboot - call print - jmp $ - -continue_BOOT: - mov word [dapack_blkcount], 0x0001 - add bx, 2 - mov eax, [bx] - call readsector - - push kernelbin - push kernelbin_len - push 0x9000 - call findfile - add esp, 6 - test ax, ax - jz continue_KERNEL - - mov si, nokernel - call print - jmp $ - -continue_KERNEL: - mov word [dapack_blkcount], 1 - mov word [dapack_boffset], 0x9000 - - push bx - add bx, 10 - mov eax, [bx] - xor edx, edx - mov ebx, 2048 - div ebx - inc eax - pop bx - push eax - - add bx, 2 - mov eax, [bx] - push eax - - ; Offsetless count. - xor ecx, ecx -LOAD_KERNEL: - mov eax, [esp] - add eax, ecx - call readsector - - mov eax, ecx - shl eax, 11 - add eax, 0x200000 - - push ecx - xor ecx, ecx - .LOAD_KERNEL_L: - mov ebx, ecx - add ebx, 0x9000 - mov ebx, dword [ebx] - - mov edx, ebx - mov ebx, eax - add ebx, ecx - mov dword [ebx], edx - - add ecx, 4 - cmp ecx, 2048 - jl .LOAD_KERNEL_L - pop ecx - - inc ecx - cmp ecx, dword [esp+4] - jl LOAD_KERNEL - -mov si, booting -call print - -mov dl, [bootDriveID] -mov byte [0x9000], dl - -mov di, 0xA000 -mov eax, 0xE820 -xor ebx, ebx -mov ecx, 24 -mov edx, 0x534D4150 -int 0x15 - -jc BIOS_NO_MEM -cmp eax, 0x534D4150 -jnz BIOS_NO_MEM -cmp cl, 20 -jnz BIOS_MEM_NO20 - -MEM_L: - test ebx, ebx - jz MEM_FINISHED - - mov ax, di - xor ch, ch - add ax, cx - mov di, ax - - mov eax, 0xE820 - mov ecx, 24 - int 0x15 - jmp MEM_L - -MEM_FINISHED: - mov eax, cr0 - or al, 1 - mov cr0, eax - - mov ax, 0x08 - mov ds, ax - mov es, ax - mov fs, ax - mov gs, ax - mov ss, ax - -; Infomation: https://wiki.osdev.org/ELF -mov ebx, 0x20002C -mov dl, byte [ebx] -push dx - -mov ebx, 0x20001C -mov ebx, dword [ebx] -push ebx - -xor dh, dh -PHT: - xor eax, eax - mov al, dh - shl eax, 5 - add eax, dword [esp] - add eax, 0x200000 - mov ebx, eax - - mov eax, dword [ebx] - cmp eax, 1 - jnz .PHT_ignore - - add ebx, 4 - mov eax, dword [ebx] - add eax, 0x200000 - push eax - - add ebx, 4 - mov eax, dword [ebx] - push eax - - add ebx, 8 - mov eax, dword [ebx] - push eax - - push dx - xor ecx, ecx - .MOVE_KERNEL_L: - mov ebx, [esp+10] - add ebx, ecx - mov ebx, dword [ebx] - - mov eax, ebx - mov ebx, dword [esp+6] - add ebx, ecx - mov dword [ebx], eax - - add ecx, 4 - cmp ecx, dword [esp+2] - jl .MOVE_KERNEL_L - pop dx - add esp, 12 - - .PHT_ignore: - inc dh - cmp dh, dl - jl PHT - -jmp (codedesc - gdt):protectedMode - -protectedMode: - BITS 32 - mov ebx, 0x100000 - mov eax, dword [ebx] - jmp eax - -BITS 16 -BIOS_NO_MEM: - mov si, nomem - call print - jmp $ -BIOS_MEM_NO20: - mov si, memno20 - call print - jmp $ - -gdtinfo: - dw gdt_end - gdt - 1 - dd gdt - gdt dd 0, 0 - flatdesc db 0xff, 0xff, 0, 0, 0, 10010010b, 11001111b, 0 - codedesc db 0xff, 0xff, 0, 0, 0, 10011010b, 11001111b, 0 - gdt_end: - -lba_not_supported: - mov si, nolba - call print - jmp $ - -boot db "BOOT" -boot_len equ ($ - boot) -kernelbin db "KERNEL.BIN", 0x3B, "1" -kernelbin_len equ ($ - kernelbin)
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