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- ORG 0x7C00
- BITS 16
- ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
- ; Bootloader for SingOS
- ; version 0.1.0.10-exp
- ;
- ; Please edit the version number if any changes is made, the last number
- ; represent the build number.
- ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
- cli
- jmp long 0x0000:start
-
- start:
- xor ax, ax
- mov ds, ax
- mov es, ax
- mov ss, ax
- mov [disk_identifier], dl
-
- ; initialize stack
- ; Set up 4K stack after this bootloader
- ; [Remember: Effective Address = Segment*16 + Offset]
- mov ax, 0x7C0 ; Set 'ax' equal to the location of this bootloader divided by 16
- add ax, 0x20 ; Skip over the size of the bootloader divided by 16
- mov ss, ax ; Set 'ss' to this location (the beginning of our stack region)
- mov sp, 8192 ; Set 'ss:sp' to the top of our 8K stack
- sti
- mov si, message ; Put address of the null-terminated string to output into 'si'
- call print ; Call our string-printing routine
-
- mov si, enter_debug_mode
- call print
- call printCRLF
- %IF 0
- ; here goes wait call, for the user to enter debug mode.
- ; Wating for 2 seconds:
- mov ah, 0x86 ; code for waiting interupt call
- mov cx, 0x001e ; high count of microseconds
- mov dx, 0x8480 ; low count
- int 0x15
-
- .busy_wait_for_key:
- xor ax, ax
- mov ah, 0x01 ; BIOS call to wait for key
- int 0x16
- jnz debug_mode
- %ENDIF
- ; entering system check:
- mov si, enter_system_check
-
- mov si, sys_check_ok ; Put address of the null-terminated string to output into 'si'
- call print ; Call our string-printing routine
-
- mov si, boot_system ; Put address of the null-terminated string to output into 'si'
- call print ; Call our string-printing routine
-
- ;This goes first as to now overwrite %ah and %al.
- mov ax, 0x0050
- mov es, ax ;Section to write into
- mov ah, 0x2 ;Read sectors from drive
- mov al, 0x08 ;Number of sectors to read (31 * 512 = 15872 bytes)
- mov ch, 0x0 ;Low 8 bits of cylinder
- mov cl, 0x11 ;First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
- mov dh, 0x0 ;Head number
- mov dl, [disk_identifier] ;Drive number
- mov bx, 0x0000 ;Offset into section
- int 0x13 ;Low level disk services
-
- jnc notcarry
- mov si, error_str
- call print
- jmp endcarrycheck
-
- notcarry:
- mov si, success_str
- call print
- call printCRLF
- ;call printCRLF
- ;mov ax, cs
- ;call dumpax
- ;mov ax, start
- ;call dumpax
- ;call printCRLF
-
- mov dl, [disk_identifier]
- xor ax, ax
- mov al, dl
- call dumpax
- call printCRLF
-
- mov ax, 0x50
- mov ds, ax
- mov ax, 89 ; lba adress
-
- jmp 0x50:0x0000 ; Jump to the kernel
-
- endcarrycheck:
- cli ; Clear the Interrupt Flag (disable external interrupts)
- hlt ; Halt the CPU (until the next external interrupt)
-
- debug_mode:
- mov si, .welcome_debug
- call print
- cli ; Clear the Interrupt Flag (disable external interrupts)
- hlt
-
- .welcome_debug db 'This is debug mode', 0
-
- ;Routine for printing a 'ax' as hex
- dumpax:
- pusha ; save registers
- mov bx, ax
- mov ah, 0xE ; Teletype output
-
- mov cx, 4 ; 4 nipples in a 16 bit word
- .loop:
- rol bx, 4 ; rotate to next nipple
- mov al, bl ; we copy to al because we need to mask only the low 4 bits
- and al, 1111b ; Do the masking
- add al, '0' ; convert to ASCII
- cmp al, '9' ; If we are greater than 9 ascii, we add 7 to make digit 10 be represented as 'A'
- jbe .skip ; -|-
- add al, 7 ; -|-
- .skip: ; -|-
- int 0x10 ; BIOS call 'output'
- loop .loop
-
- popa ; restore registers
- ret
-
- printCRLF:
- mov ah, 0xE
- mov al, 13
- int 0x10
- mov al, 10
- int 0x10
- ret
-
- ; Routine for outputting string in 'si' register to screen
- print:
- mov ah, 0xE ; Specify 'int 0x10' 'teletype output' function
- ; [AL = Character, BH = Page Number, BL = Colour (in graphics mode)]
- .printchar:
- lodsb ; Load byte at address SI into AL, and increment SI
- cmp al, 0
- je .done ; If the character is zero (NUL), stop writing the string
- int 0x10 ; Otherwise, print the character via 'int 0x10'
- jmp .printchar ; Repeat for the next character
- .done:
- ret
-
- data:
- message db 'Bootloader for SingOS! v0.1.0.10-exp',13,10,0
- enter_debug_mode db 'Press d to enter bootloader debug mode',13,10,0
- enter_system_check db 'Performing system check:',13,10,0
- sys_check_ok db 'System check ok', 13, 10, 0
- boot_system db 'Read SingOS from disk', 13, 10, 0
- error_str db 'Error', 0
- success_str db 'Success', 0
- disk_identifier db 0
-
- ; Pad to 510 bytes (boot sector size minus 2) with 0s, and finish with the two-byte standard boot signature
- times 446-($-$$) db 0 ; First partion entry
- db 0x80 ; active partition
- db 0, 0x00, 0x17 ; First sector CHS
- db 0x18 ; Disk type (Other) (Why 18, answer ':' ^ ')' )
- db 0xff, 0xff, 0xff ; Ending CHS values
- db 0x18, 0, 0, 0x00 ; Staring LBA
- db 0, 0xff, 0xff, 0xff ; Size
-
- db 0x00
- db 0x0, 0x0, 0x0
- db 0x0
- db 0x0, 0x0, 0x0
- db 0x00, 0x00, 0x00, 0x00
- db 0x0, 0x00, 0x00, 0x00
-
- times 478-($-$$) db 0 ; Third partion entry
-
- times 494-($-$$) db 0 ; Forth partion entry
-
- times 510-($-$$) db 0
- dw 0xAA55 ; => 0x55 0xAA (little endian byte order)
- ; bootloder debug_mode goes here
-
- times 8192-($-$$) db 0
-
- ; From Version 0.0.3 we are concatinate the bootloader and the kernel after compile time
- ;%include "kernel.nasm"
-
- ;times 8192-($-$$) db 0
-
- ;80
- ;00 01 00
- ;00
- ;3F 60 21
- ;00 00 00 00
- ;00 10 09 00
-
- ;00
- ;FE FF FF
- ;EF
- ;FE FF FF
- ;B0 0E 00 00
- ;40 03 00 00
-
- ;00
- ;00 00 00
- ;00
- ;00 00 00
- ;00 00 00 00
- ;00 00 00 00
-
- ;00
- ;00
- ;00 00 00 00
- ;00 00 00 00
- ;00 00 00
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