ORG 0x7C00 BITS 16 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; SLRboot ; Bootloader for SingOS ; version 0.2.0.3-exp ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; cli jmp long 0x0000:start start: mov ax, 0x1000 mov ss, ax mov sp, 0xb000 mov ax, 0 mov ds, ax mov es, ax mov [disk_identifier], dl sti mov si, 0x7c00 mov di, 0x600 mov cx, 0x100 rep movsw mov bx, relocated sub bx, 0x7600 ; Calculate the offset. push bx ret ; Return far ;jmp long 0:bx relocated: mov si, message ; Put address of the null-terminated string to output into 'si' call print ; Call our string-printing routine ; Check for more than one active partition that we can start from. xor bx, bx xor cx, cx mov ax, [partition_1.active_partition] call dumpax cli hlt cmp ax, 0x80 jne check_p_2 mov bx, 0x01 ; Partion 1 active inc cx check_p_2: mov ax, [partition_2.active_partition] cmp ax, 0x80 jne check_p_3 inc cx mov bx, 0x02 ; Partion 2 active check_p_3: mov ax, [partition_3.active_partition] cmp ax, 0x80 jne check_p_4 inc cx mov bx, 0x03 ; Partion 3 active check_p_4: mov ax, [partition_4.active_partition] cmp ax, 0x80 jne eval_active_partion_number inc cx mov bx, 0x04 ; Partion 4 active eval_active_partion_number: cmp cx, 1 je boot_partition: ; 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 mov bx, 1 boot_partition: ; IMPORTANT bx, has to hold the value 1-4 for the partiotion that wanted to be booted. mov ax, partition_1 .loop: cmp bx, 1 je break add ax, 0x10 dec bx jmp .loop break: add ax, 7 ; This is the offset to fetch the LBA start adress of the partition record mov bx, [ax] ; first part of LBA mov WORD [DAPACK.lba_addr_dw_low], bx inc ax ; next part mov bx, [ax] mov WORD [DAPACK.lba_addr_dw_low + 1], bx inc ax ; next part mov bx, [ax] mov WORD [DAPACK.lba_addr_dw_low + 2], bx inc ax ; next part mov bx, [ax] mov WORD [DAPACK.lba_addr_dw_low + 3], bx mov WORD [DAPACK.blkcnt], 0x01 mov WORD [DAPACK.db_addr_segment], 0x0000 mov WORD [DAPACK.db_addr_offset], 0x7c00 mov si, DAPACK ; address of "disk address packet" xor ax, ax mov ah, 0x42 ; READ mov dl, [disk_identifier] int 0x13 jmp long 0x0:0x7c00 cli hlt %IF 0 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 ; 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 mov ax, 0x0 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 printCRLF: mov ah, 0xE mov al, 13 int 0x10 mov al, 10 int 0x10 ret %ENDIF ;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 ; 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 'SLRboot for SingOS! v0.2.0.3-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 boot_this_partition: dw 0 disk_identifier db 0 DAPACK: .dap_Size: db 0x10 ; This is always 16 bytes (0x10) .rev_byte: db 0x0 ; reserved byte, should always be zero .blkcnt: dw 0x0 ; int 13 resets this to # of blocks actually read/written .db_addr_offset: dw 0x0 ; memory buffer destination address (0:7c00) .db_addr_segment: dw 0x0 ; in memory page zero .lba_addr_dw_low: dd 0x0 ; put the lba to read in this spot .lba_addr_dw_high: dd 0x0 ; more storage bytes only for big lba's ( > 4 bytes ) ; Pad to 510 bytes (boot sector size minus 2) with 0s, and finish with the two-byte standard boot signature times 446-($-$$) db 0 ; First partion entry partition_1: .active_partition db 0x80 .start_CHS db 0x00, 0x00, 0x11;0x20, 0x21, 0x00 .disk_type db 0x83 .end_CHS db 0x8C, 0x3D, 0x0F .start_LBA db 0x10, 0x00, 0x00, 0x00 .size db 0x00, 0xC8, 0x03, 0x00 partition_2: .active_partition db 0x80 .start_CHS db 0x8C, 0x3E, 0x0F .disk_type db 0x83 .end_CHS db 0xFF, 0xFF, 0xFF .start_LBA db 0x00, 0xD0, 0x03, 0x00 .size db 0x00, 0x28, 0x1C, 0x03 partition_3: .active_partition db 0x00 .start_CHS db 0x00, 0x00, 0x00 .disk_type db 0x00 .end_CHS db 0x00, 0x00, 0x00 .start_LBA db 0x00, 0x00, 0x00, 0x00 .size db 0x00, 0x00, 0x00, 0x00 partition_4: .active_partition db 0x00 .start_CHS db 0x00, 0x00, 0x00 .disk_type db 0x00 .end_CHS db 0x00, 0x00, 0x00 .start_LBA db 0x00, 0x00, 0x00, 0x00 .size db 0x00, 0x00, 0x00, 0x00 times 510-($-$$) db 0 dw 0xAA55 ; => 0x55 0xAA (little endian byte order) ; bootloder debug_mode goes here times 8192-($-$$) db 0 ; mov si, 0x7be ; cmp byte [si], al ; jne 0x33 ; add si, 0x10 ; cmp si, 0x7fe ; jne 0x24 ; jmp 0x49 ; mov ah, 2 ; mov al, 1 ; mov bx, 0x7c00 ; mov dl, 0x80 ; mov dh, byte [si + 1] ; mov cx, word [si + 2] ; int 0x13 ; jmp long 0:0x7c00 ; jmp 0x49