154 lines
2.0 KiB
ArmAsm
154 lines
2.0 KiB
ArmAsm
.code16
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.text
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.global _start
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_start:
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jmp everything
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.org 20
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.global kernel_size
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kernel_size:
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.long _end - _start
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everything:
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mov $0x1000, %ax
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mov %ax, %es
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mov %ax, %ds
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# reset disk
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mov $0, %ah
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int $0x13
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# stop the cursor
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mov $1, %ah
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mov $0,%cl
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mov $0x20,%ch
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int $0x11
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# get the system memory, if this call fails then halt
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clc
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mov $0, %bx
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mov $0xe801, %ax
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int $0x15
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jc halt
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shr $10, %ax
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shr $4, %bx
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add %ax, %bx
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mov %bx, total_mem_mb-_start
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# vga text mode
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mov $0x0003, %ax
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int $0x10
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enable_a20:
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#enable the a20 gate
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inb $0x92, %al
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orb $2, %al
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outb %al, $0x92
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prep_protected:
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cli
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lgdt (gdt_init-_start)
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mov %cr0, %eax
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or $0x01, %eax
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mov %eax, %cr0 # protected bit set
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ljmpl $8, $protected
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halt16:
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jmp halt16
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.code32
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protected:
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mov $2*8, %ax
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mov %ax, %es
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mov %ax, %ds
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mov %ax, %ss
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mov $5*8, %ax
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ltr %ax
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mov $0, %ax
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mov %ax, %fs
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mov %ax, %gs
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mov $0xFFF0, %sp
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mov $0xFFF0, %bp
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ljmpl $8, $kmain
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.align 4
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.global video_info_struct
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video_info_struct:
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.word 0
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.byte 0,0
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.word 0,0,0,0
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.long 0
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.global video_xbytes
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video_xbytes:
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.word 0
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.global video_xres
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video_xres:
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.word 0
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.global video_yres
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video_yres:
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.word 0
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.byte 0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0
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.global video_buffer
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video_buffer:
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.long 0
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.long 0
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.word 0
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.word 0
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.byte 0,0,0,0,0,0,0,0,0,0
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.long 0
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.rept 190
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.byte 0
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.endr
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# some assembly stubs we can call from the kernel
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.global idt_load
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.extern idtr
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idt_load:
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lidt (idtr)
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ret
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.global gdt_load
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gdt_load:
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lgdt (gdt_init)
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ret
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.global reboot
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reboot:
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cli
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lidt reboot_struct
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int $1
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reboot_struct:
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.word 0
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.long 0
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.global halt
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halt:
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cli
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hlt
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jmp halt
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# kernel data structures
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.align 16
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.global gdt
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gdt:
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.word 0,0,0,0
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.word 0xffff, 0x0000, 0x9a00, 0x00cf
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.word 0xffff, 0x0000, 0x9200, 0x00cf
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.word 0xffff, 0x0000, 0xfa00, 0x00cf
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.word 0xffff, 0x0000, 0xf200, 0x00cf
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.word 0x0068, (tss-_start), 0x8901, 0x00cf
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gdt_init:
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.word gdt_init-gdt
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.long gdt
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.align 16
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.global tss
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tss:
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.long 0
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.global total_mem_mb
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total_mem_mb:
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.word 0
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