157 lines
3.2 KiB
ArmAsm
157 lines
3.2 KiB
ArmAsm
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.set TARGET_WIDTH, 800
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.set TARGET_HEIGHT, 600
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.set TARGET_BPP, 32
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.code16
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.section .stage2
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# Find suitable video mode
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# return:
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# ax: video mode number if found, 0 otherwise
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.global vesa_find_video_mode
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vesa_find_video_mode:
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pushw %ax
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pushw %cx
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pushw %di
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pushl %esi
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# clear target mode and frame buffer
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movw $0, (vesa_target_mode)
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movl $0, (framebuffer + 0)
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movl $0, (framebuffer + 4)
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movl $0, (framebuffer + 8)
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movl $0, (framebuffer + 12)
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movw $0, (framebuffer + 16)
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# get vesa information
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movw $0x4F00, %ax
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movw $vesa_info_buffer, %di
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int $0x10
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cmpb $0x4F, %al; jne .vesa_unsupported
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cmpb $0x00, %ah; jne .vesa_error
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# confirm that response starts with 'VESA'
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cmpl $0x41534556, (vesa_info_buffer)
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jne .vesa_error
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# confirm that version is atleast 2.0
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cmpw $0x0200, (vesa_info_buffer + 0x04)
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jb .vesa_unsupported_version
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movl $(vesa_info_buffer + 0x0E), %esi
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movl (%esi), %esi
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.vesa_find_video_mode_loop_modes:
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cmpw $0xFFFF, (%esi)
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je .vesa_find_video_mode_loop_modes_done
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# get info of next mode
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movw $0x4F01, %ax
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movw (%esi), %cx
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movw $vesa_mode_info_buffer, %di
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int $0x10
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cmpb $0x4F, %al; jne .vesa_unsupported
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cmpb $0x00, %ah; jne .vesa_error
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# check whether in graphics mode
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testb $0x10, (vesa_mode_info_buffer + 0)
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jz .vesa_find_video_mode_next_mode
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# compare mode's dimensions
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cmpw $TARGET_WIDTH, (vesa_mode_info_buffer + 0x12)
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jne .vesa_find_video_mode_next_mode
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cmpw $TARGET_HEIGHT, (vesa_mode_info_buffer + 0x14)
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jne .vesa_find_video_mode_next_mode
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cmpb $TARGET_BPP, (vesa_mode_info_buffer + 0x19)
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jne .vesa_find_video_mode_next_mode
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movl (vesa_mode_info_buffer + 0x28), %esi
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movl %esi, (framebuffer + 0)
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movw (vesa_mode_info_buffer + 0x10), %ax
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movw %ax, (framebuffer + 4)
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movl $TARGET_WIDTH, (framebuffer + 8)
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movl $TARGET_HEIGHT, (framebuffer + 12)
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movb $TARGET_BPP, (framebuffer + 16)
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movb $1, (framebuffer + 17)
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movw %cx, (vesa_target_mode)
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jmp .vesa_find_video_mode_loop_modes_done
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.vesa_find_video_mode_next_mode:
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addl $2, %esi
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jmp .vesa_find_video_mode_loop_modes
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.vesa_find_video_mode_loop_modes_done:
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popl %esi
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popw %di
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popw %cx
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popw %ax
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ret
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.vesa_unsupported:
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movw $vesa_unsupported_msg, %si
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jmp print_and_halt
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.vesa_unsupported_version:
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movw $vesa_unsupported_version_msg, %si
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jmp print_and_halt
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.vesa_error:
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movw $vesa_error_msg, %si
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jmp print_and_halt
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# set mode found from vesa_find_video_mode. if no mode
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# was found, set it to 80x25 text mode to clear the screen.
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.global vesa_set_target_mode
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vesa_set_target_mode:
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pushw %ax
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pushw %bx
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movw (vesa_target_mode), %bx
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testw %bx, %bx
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jz .vesa_set_target_mode_generic
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movw $0x4F02, %ax
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orw $0x4000, %bx
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int $0x10
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jmp .set_video_done
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.vesa_set_target_mode_generic:
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movb $0x03, %al
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movb $0x00, %ah
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int $0x10
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.set_video_done:
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popw %bx
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popw %ax
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ret
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vesa_error_msg:
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.asciz "VESA error"
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vesa_unsupported_msg:
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.asciz "VESA unsupported"
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vesa_unsupported_version_msg:
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.asciz "VESA unsupported version"
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vesa_success_msg:
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.asciz "VESA success"
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.section .bss
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vesa_info_buffer:
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.skip 512
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vesa_mode_info_buffer:
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.skip 256
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vesa_target_mode:
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.skip 2
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.global framebuffer
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framebuffer:
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.skip 4 # address
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.skip 4 # pitch
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.skip 4 # width
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.skip 4 # height
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.skip 1 # bpp
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.skip 1 # type
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