175 lines
2.6 KiB
ArmAsm
175 lines
2.6 KiB
ArmAsm
.include "common.S"
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.code16
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#########################################
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#
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# STAGE 1 BOOTLOADER
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#
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# its sole purpose is to load stage2 from
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# bios boot partition
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#
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#########################################
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.section .stage1
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.global stage1_main
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stage1_main:
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# setup segments and stack
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xorw %ax, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %ss
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movl $0x7C00, %esp
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# save boot disk number
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call read_stage2_into_memory
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jmp stage2_main
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.global print_and_halt
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print_and_halt:
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call puts
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halt:
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hlt
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jmp halt
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#########################################
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#
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# STAGE 2 BOOTLOADER
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#
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#########################################
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.section .stage2
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stage2_main:
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# clear screen and enter 80x25 text mode
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movb $0x03, %al
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movb $0x00, %ah
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int $0x10
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# print hello message
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movw $hello_msg, %si
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call puts; call print_newline
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lgdt gdtr
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call enter_unreal_mode
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movw $unreal_enter_msg, %si
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call puts; call print_newline
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call enable_a20
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call get_memory_map
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call print_newline
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call read_user_command_line
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call print_newline
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movw $start_kernel_load_msg, %si
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call puts; call print_newline
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call print_memory_map
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call find_root_disk
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call find_root_partition
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call print_root_partition_info
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call print_newline
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call has_ext2_filesystem
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testb %al, %al
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jz print_and_halt
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call ext2_find_kernel
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movl $ext2_inode_read_bytes, %esi
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call elf_read_kernel_to_memory
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call vesa_set_video_mode
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cli
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# kernel entry point
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movl %eax, %ecx
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# setup kernel parameters
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movl $0xD3C60CFF, %eax
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movl $banan_boot_info, %ebx
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# setup protected mode
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movl %cr0, %edx
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orb $1, %dl
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movl %edx, %cr0
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# jump to protected mode
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ljmpl $GDT_CODE32, $protected_mode
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.code32
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protected_mode:
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# setup protected mode segments
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movw $GDT_DATA32, %dx
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movw %dx, %ds
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movw %dx, %es
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movw %dx, %fs
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movw %dx, %gs
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movw %dx, %ss
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# jump to kernel entry
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jmp *%ecx
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.code16
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enter_unreal_mode:
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cli
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pushw %ds
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movl %cr0, %eax
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orb $1, %al
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movl %eax, %cr0
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ljmpl $GDT_CODE16, $.enter_unreal_mode_pmode
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.enter_unreal_mode_pmode:
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movw $GDT_DATA32, %bx
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movw %bx, %ds
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andb $0xFE, %al
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movl %eax, %cr0
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ljmpl $0x00, $.enter_unreal_mode_unreal
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.enter_unreal_mode_unreal:
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popw %ds
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sti
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ret
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.section .data
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hello_msg:
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.asciz "This is banan-os bootloader"
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unreal_enter_msg:
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.asciz "Entered unreal mode"
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start_kernel_load_msg:
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.asciz "Starting to load kernel"
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gdt:
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.quad 0x0000000000000000
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.quad 0x008F9A000000FFFF # 16-bit code
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.quad 0x00CF92000000FFFF # 32-bit data
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.quad 0x00CF9A000000FFFF # 32-bit code
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gdtr:
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.short . - gdt - 1
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.long gdt
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banan_boot_info:
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boot_command_line:
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.long command_line
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boot_framebuffer:
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.long framebuffer
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boot_memory_map:
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.long memory_map
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