150 lines
2.5 KiB
NASM
150 lines
2.5 KiB
NASM
;; File: loader.asm
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format binary
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include '../common/const.inc'
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include '../common/macro.inc'
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include 'multiboot.inc'
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org LOADER_BASE
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use32
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jmp _start
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align 4
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multiboot_header:
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mb_header MultibootHeader multiboot_header
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_start:
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cmp eax, MULTIBOOT_MAGIC
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je multiboot
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use16
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align 2
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; =========================================================================
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; real mode code
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; =========================================================================
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push cs
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pop ds
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mov [drive_number], dl
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mov si, msg_stage2
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call bios_log
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; enable A20 line
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call a20_enable
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jc .error_a20
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; check drive type
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; dl <= 0x7F == floppy
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; dl >= 0x80 == hard drive
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; dl == 0xE0 ~= CD/DVD
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; dl <= 0xFF == hard drive
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mov dl, [drive_number]
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cmp dl, 0x7F
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; skip disk extension check
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jle @f
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; check disk extensions
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mov ah, 0x41
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mov bx, 0x55AA
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int 0x13
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jc @f
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mov [drive_lba], 1
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@@:
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; detect filesystem (FAT12/16 or StpdFS)
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; load kernel from filesystem
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; fetch memory map from bios
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call memory_get_map
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jc .error_memory
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; video information
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call video_setup
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; load GDT and enter Protected-Mode
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lgdt [gdt_ptr]
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; enable protected mode
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mov eax, cr0
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or al, 1
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mov cr0, eax
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; reload ds, es, fs, gs, ss
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mov ax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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jmp 0x8:common32
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.error_memory:
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mov si, msg_error_memory
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jmp .error
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.error_a20:
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mov si, msg_error_a20
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.error:
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call bios_log
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@@:
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hlt
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jmp @b
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include 'a20.inc'
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include '../common/bios.inc'
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include 'logger.inc'
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include 'memory.inc'
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include 'video.inc'
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include 'gdt.inc'
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drive_number rb 1
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drive_lba db 0
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msg_stage2 db "StupidOS Loader", 0
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kernel_fat12_file db "VMSTUPIDSYS", 0
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config_fat12_file db "BOOT INI", 0
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msg_error_a20 db "ERROR: can't enable a20 line", 0
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msg_error_memory db "ERROR: can't detect available memory", 0
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use32
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; =========================================================================
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; protected mode code
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; =========================================================================
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multiboot:
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; https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Machine-state
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; get screen information
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; get memory map
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; get kernel from module
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common32:
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mov dword [0xb8000], 0x07690748
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; paging
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; identity map first 1MB
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; map kernel to 0xC0000000
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push STPDBOOT_MAGIC
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mov eax, 0xC0000000
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jmp eax
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hang:
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hlt
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jmp $
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_edata:
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boot_structure:
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align 4096
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boot_page_directory:
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rb 4096
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boot_768_page_table:
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rb 4096
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_end:
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