222 lines
3 KiB
NASM
222 lines
3 KiB
NASM
bits 16
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org 0x7c3e
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kernel_sectors equ 64
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kernel_segment equ 0x3000
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support_flags equ 0x4000
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pci_hw_char equ 0x4001
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pci_ver equ 0x4002
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last_pci_bus equ 0x4004
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bios_mmap_len equ 0x4006
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vbe_mode equ 0x4008
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vbe_block equ 0x4200
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vbe_mode_info equ 0x4400
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pci_support equ 0x80
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pae_support equ 0x40
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in al, 0x92
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or al, 0x02
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out 0x92, al
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xor ax, ax
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mov ss, ax
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mov sp, 0x8000
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mov ax, kernel_segment
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mov es, ax
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mov ax, 0x0200 + kernel_sectors
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xor bx, bx
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mov cx, 0x0002
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xor dh, dh
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int 0x13
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mov ax, 0xb101
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int 0x1a
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cmp edx, 0x20494350
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jne no_pci
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test ah, ah
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jnz no_pci
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mov byte [support_flags], pci_support
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mov byte [pci_hw_char], al
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mov word [pci_ver], bx
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mov byte [last_pci_bus], cl
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no_pci:
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mov eax, 1
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cpuid
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test dl, 0x40
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jz no_pae
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or byte [support_flags], pae_support
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no_pae:
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mov ax, 0x1000
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mov es, ax
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xor di, di
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mov edx, 0x534d4150
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xor ebx, ebx
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mmap_loop:
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mov eax, 0xe820
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mov ecx, 24
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int 0x15
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jc mmap_end
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add di, 24
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test ebx, ebx
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jnz mmap_loop
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mmap_end:
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mov word [bios_mmap_len], di
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xor ax, ax
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mov es, ax
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mov di, vbe_block
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mov ah, 0x4f
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mov dword [di], 0x32454256;'VBE2'
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int 0x10
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cmp dword [di], 0x41534556;'VESA'
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jne no_vbe
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mov bx, word [di + 0x0e]
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mov ax, word [di + 0x10]
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mov fs, ax
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xor esi, esi
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mov bp, 0xffff
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mov di, 0x5000
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vbe_loop:
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max_height equ 800
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;fs:bx is mode pointer
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;esi is highest resolution yet (width * height)
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;bp is that mode's number
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;uses 0x5000 - 0x50ff as mode info buffer
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;skips those without byte-aligned pixels
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mov cx, word [fs:bx]
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cmp cx, 0xffff
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je got_highest_vbe
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add bx, 4
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mov ax, 0x4f01
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int 0x10
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mov al, byte [di]
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not al
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test al, 0x9a
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jnz vbe_loop
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mov dx, word [di + 0x14];height
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cmp dx, max_height
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jg vbe_loop
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mov ax, word [di + 0x12];width
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mul dx
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shl edx, 16
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mov dx, ax
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xor eax, eax
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mov al, byte [di + 0x19];bpp
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test al, 0x07
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jnz vbe_loop
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mul edx
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cmp eax, esi
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jle vbe_loop
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mov esi, eax
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mov bp, cx
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jmp vbe_loop
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got_highest_vbe:
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cmp bp, 0xffff
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je no_vbe
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mov cx, bp
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mov ax, 0x4f01
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mov di, vbe_mode_info
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int 0x10
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or ch, 0x40
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mov word [vbe_mode], cx
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mov ax, 0x4f02
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mov bx, cx
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int 0x10
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cli
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lgdt [gdt]
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mov eax, cr0
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or al, 0x01
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mov cr0, eax
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jmp 0x10:pmode
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no_vbe:
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xor ax, ax
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mov es, ax
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mov ax, 0x1300
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mov bx, 0x004f
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mov cx, no_vbe_str.len
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xor dx, dx
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mov bp, no_vbe_str
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int 0x10
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real_halt:
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hlt
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jmp real_halt
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no_vbe_str:
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db "NO VBE2!"
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.len equ $ - no_vbe_str
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bits 32
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pmode:
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mov ax, 0x18
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mov ds, ax
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mov es, ax
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mov ss, ax
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mov esp, 0x00040000
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xor ebp, ebp
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call kernel_segment * 16
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halt:
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hlt
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jmp halt
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times $$ + 510 - 0x3e - $ - (gdt.e - gdt) db 0
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gdt:
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dw .e - .t
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dd .t
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.t:
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dq 0x0000_0000_0000_0000;0x00: null
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dq 0x0040_8900_4f98_0068;0x08: tss, 0x4f98
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dq 0x00cf_9a00_0000_ffff;0x10: kernel code
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dq 0x00cf_9200_0000_ffff;0x18: kernel data
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dq 0x00cf_fa00_0000_ffff;0x20: user code
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dq 0x00cf_f200_0000_ffff;0x28: user data
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.e:
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dw 0xaa55
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