2019-07-21 18:13:42 +00:00
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[BITS 32] ;... somehow.
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[GLOBAL start]
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start:
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mov esp, _sys_stack ; Stack pointer!
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jmp stublet ; This has a purpse. I don't know what it is, but there is one.
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ALIGN 4 ; 4KB alignment, required by GRUB.
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mboot: ; This is all magic, and all of it required for GRUB to see our stuff.
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MULTIBOOT_ALIGN equ 1<<0
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MULTIBOOT_MEM equ 1<<1
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MULTIBOOT_AOUT equ 1<<16
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MULTIBOOT_MAGIC equ 0x1BADB002
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MULTIBOOT_FLAGS equ MULTIBOOT_ALIGN | MULTIBOOT_MEM | MULTIBOOT_AOUT
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MULTIBOOT_CHECKSUM equ -(MULTIBOOT_MAGIC + MULTIBOOT_FLAGS)
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EXTERN code, bss, end
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dd MULTIBOOT_MAGIC
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dd MULTIBOOT_FLAGS
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dd MULTIBOOT_CHECKSUM
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dd mboot
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dd code
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dd bss
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dd end
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dd start
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stublet: ; Where the kernel stuff goes.
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;=====================================
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;===Priority: 32 bit Protected Mode===
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;=====================================
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cli ; Interrupts be gone!
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xor cx, cx ; CX - GP, useful here.
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kbempty:
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in al, 64h ; Read keyboard status
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test al, 02h ; Check if the buffer is full
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loopnz kbempty ; Wait until it is
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mov al, 0d1h ; Prepare a message
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out 64h, al ; And then send it to the keyboard (controller)
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kbempty2:
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in al, 64h ; Read the status again
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test al, 02h ; Check if it's processed our message
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loopnz kbempty2 ; And wait until it has
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mov al, 0dfh ; Prepare a different message, telling it to enable A20
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out 60h, al ; Send the message
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mov cx, 14h ; Restore the value of CX
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wait_kb: ; Insinuate a 25uS delay to allow the processor to catch up
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out 0edh, ax
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loop wait_kb
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mov eax, cr0 ; Read the control register
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or al, 1 ; Set bit 1: protected mode
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mov cr0, eax ; Set the control register back
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jmp $+2 ; Clear the queue
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nop ; (jump straight to kernel)
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nop
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;==================================
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;===32-bit Protected Mode active===
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;==================================
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; Call the kernel
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EXTERN kernel_main
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call kernel_main
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jmp $
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[GLOBAL load_gdt]
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[EXTERN gp]
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load_gdt:
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lgdt [gp] ; Load the new GDT pointer
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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 0x08:flush
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flush:
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ret
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[GLOBAL idt_load]
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[EXTERN idtp]
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idt_load:
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lidt [idtp]
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ret
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SECTION .bss
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resb 8192
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_sys_stack:
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