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adding bootloader files from the issue in gittea
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@ -1,131 +1,166 @@
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[BITS 16]
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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[ORG 0x7c00]
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; Stage 1 bootloader for ClassicOS ;
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; -------------------------------- ;
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; Determines if it was loaded from ;
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; a floppy disk or an hard disk ;
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; drive, and then loads stage 2 ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;
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; Assembler directives ;
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;;;;;;;;;;;;;;;;;;;;;;;;
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; tells the assembler that the program will be loaded at 0x7C00
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; this is done by the BIOS
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org 0x7C00
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; we are targeting (x86) 16-bit real mode
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bits 16
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;;;;;;;;;;;;;;;;;
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; Jump to start ;
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;;;;;;;;;;;;;;;;;
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jmp start
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;;;;;;;;
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; Data ;
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;;;;;;;;
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; fdd geometry & options
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fddsamt db 8 ; how many sectors to load
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fddretr db 5 ; max retries for fdd operations
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fddcretr db 0 ; current retries left
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; misc strings
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welcome1 db "Welcome to the ClassicOS Stage 1 bootloader.", 13, 10, 0
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disktype db "Drive type: ", 0
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diskfdd db "FDD", 13, 10, 0
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diskhdd db "HDD", 13, 10, 0
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loaded db "Data loaded!", 13, 10, 0
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; errors
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fdderes db "FDD reset failed.", 13, 10, 0
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fddeload db "FDD read failed.", 13, 10, 0
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; storage
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disknum db 0
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;;;;;;;;;;;
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; Program ;
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;;;;;;;;;;;
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start:
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start:
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; Processor initialization (only stack segment register needed)
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xor ax, ax ; set up segment registers to segment 0 since
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mov ss, 0x1000 ; Set stack segment register
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mov ds, ax ; our addresses are already relative to 0x7C00
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mov sp, 0x7C00 ; Set stack pointer (SP)
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mov es, ax
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mov ds, ss ; Set data segment register (DS)
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; Identify boot device using BIOS calls
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mov [disknum], dl ; save disk number to memory
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identify_drive:
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mov ah, 0x0E ; Get Interrupt Vector for INT 13h (Disk Services)
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int 0x80
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cmp cl, 0x41 ; Check for floppy drive interrupt vector (example)
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je is_floppy
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cmp cl, 0x80 ; Check for hard disk interrupt vector (example)
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je is_harddrive
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; Handle invalid drive type (error handling)
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; ...
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is_floppy:
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mov ah, 0x01 ; set cursor shape
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; Perform floppy disk access (assuming AH=0x02 for read sectors)
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mov cx, 0x0100 ; hide cursor by setting ch = 1 and cl = 0x00
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mov ah, 0x02 ; Read sectors
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int 0x10 ; video interrupt
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mov al, 1 ; Number of sectors to read (1)
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; Set CH, CL, DH, DL for floppy based on your system configuration
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mov ah, 0x08 ; read page number into bh
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; (Replace these values with appropriate settings for your floppy drive)
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int 0x10
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mov ch, 0 ; Cylinder (example, adjust based on your floppy)
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mov cl, 1 ; Sector number (example, adjust based on boot sector location)
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mov dh, 0 ; Head number (example, typically 0 for single-sided floppies)
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mov dl, 0x00 ; Drive number (0x00 for floppy drive A)
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; Set ES:BX to the memory address where you want to store the read data
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mov si, welcome1 ; print welcome
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mov es, 0x1000 ; Example segment (adjust as needed)
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call printstr
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mov bx, 0x0 ; Memory offset within the segment (example)
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mov si, disktype ; print first part of disk type
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call printstr
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mov dl, [disknum] ; restore disk number - should not be
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; strictly necessary but you never know
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and dl, 0x80 ; sets zf if disk is floppy
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jz fddload
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hddload:
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mov si, diskhdd ; print disk type
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call printstr
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jmp halt ; not implemented!
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fddload:
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mov si, diskfdd ; print disk type
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call printstr
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fddload_onto_reset:
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mov ah, [fddretr] ; load max retries in memory
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mov [fddcretr], ah
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fddload_reset:
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mov si, fdderes ; load error message pointer
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dec byte [fddcretr] ; decrement the retries counter
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jz fddload_err ; if it is 0, we stop trying
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mov ah, 0x00 ; otherwise, reset function (int 0x13)
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int 0x13
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int 0x13
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jc error_floppy
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jc fddload_reset ; if jc (error), we try again
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; Implement error handling (omitted here for brevity)
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fddload_onto_load:
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; Process the read data from the floppy sector (load second stage bootloader, etc.)
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mov ah, [fddretr] ; reset retries counter
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mov [fddcretr], ah
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mov ax, 0x1000 ; need to stay within real mode limits
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mov es, ax
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fddload_load: ; loads 512*fddsamt bytes from sector 2 on.
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mov si, fddeload
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dec byte [fddcretr]
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jz fddload_err
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is_harddrive:
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mov dh, 0 ; head 0
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mov ch, 0 ; cyl/track 0
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mov cl, 2 ; start sector
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mov bx, 0 ; memory location
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mov al, [fddsamt] ; how many sectors to read
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mov ah, 0x02 ; read function (int 0x13)
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int 0x13
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jc fddload_load ; if jc (error), we try again
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cmp al, [fddsamt] ; also if al is not 1, we have a problem
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jnz fddload_load
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; Sample code (not guaranteed to work universally)
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fddload_done:
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mov ah, 0x02 ; Set function for read sectors
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mov si, loaded ; we have successfully loaded the data
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mov al, 0x01 ; Read one sector
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call printstr
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; Set CH, CL, DH for desired sector location (e.g., first sector)
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jmp halt ; this will be jmp 0x1000:0x0000
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mov dl, 0x80 ; Drive number (assuming drive A is boot device)
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mov es, segment_address ; Set ES for buffer to store read data
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mov bx, buffer_offset ; Set BX for offset within the buffer
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int 13h ; Raise BIOS interrupt for disk read
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fddload_err:
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call printstr ; print
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jmp halt ; and die
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; Check Carry flag for error handling
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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jc harddrive_not_found ; Jump if Carry flag is set (potential error)
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; printstr routine, prints the string pointed by si using int 0x10 ;
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; sets the direction flag to 0 ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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printstr:
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cld ; clear df flag - lodsb increments si
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printstr_loop:
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lodsb ; load next character into al, increment si
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or al, al ; sets zf if al is 0x00
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jz printstr_end
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mov ah, 0x0E ; teletype output (int 0x10)
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int 0x10 ; print character
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jmp printstr_loop
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printstr_end:
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ret ; return to caller address
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; Hard drive likely present (further processing can occur)
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; ... (rest of your bootloader code)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; halt routine - infinite loop ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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halt:
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cli
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jmp halt
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harddrive_not_found:
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;;;;;;;;;;;
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; Handle error condition (missing drive or other issue)
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; Padding ;
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;;;;;;;;;;;
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; $ is the address of the current line, $$ is the base address for
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; this program.
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; the expression is expanded to 510 - ($ - 0x7C00), or
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; 510 + 0x7C00 - $, which is, in other words, the number of bytes
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; before the address 510 + 0x7C00 (= 0x7DFD), where the 0xAA55
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; signature shall be put.
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times 510 - ($ - $$) db 0x00
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; ... (error handling logic)
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;;;;;;;;;;;;;;;;;;
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; BIOS signature ;
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memory_error:
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;;;;;;;;;;;;;;;;;;
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; ... (error handling or continue with limited memory)
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dw 0xAA55
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; Second stage loading (simplified example)
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; Here's an improved version of the load_second_stage section with the placeholder jump replaced by actual loading logic:
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; Code snippet
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load_second_stage:
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; Calculate address of second stage bootloader (assuming offset from boot sector)
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mov dx, 0x0000 ; Clear DX register for better calculation
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add dx, sector_count ; Add number of sectors to skip (adjust as needed)
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shl dx, 5 ; Multiply by sector size (512 bytes)
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add dx, 0x7C00 ; Add boot sector address offset
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; Read second stage bootloader from calculated address
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mov ah, 0x02 ; Function for reading sectors
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mov al, 1 ; Number of sectors to read (1 for second stage)
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mov es, dx ; Set ES segment register to calculated address
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mov bx, 0x0000 ; Set BX offset within the segment (example)
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int 13h ; Raise BIOS interrupt for disk read
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; Check Carry flag for error handling
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jc memory_error ; Jump if Carry flag is set (potential error)
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; Second stage likely loaded successfully, jump to it
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jmp second_stage_address ; Direct jump to the defined address
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error_floppy:
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; Display a basic error message (optional)
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mov ah, 0x0E ; BIOS video call for displaying text (educational purposes)
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mov bh, 0x00 ; Set background color (black)
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mov bl, 0x07 ; Set text color (white)
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mov dx, error_floppy_message ; Address of error message string
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int 0x10 ; BIOS video interrupt
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; Halt the boot process (replace with a retry or more advanced error handling)
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hlt ; Halt instruction
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error_floppy_message db 'Floppy disk read error!', 0x0
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memory_error:
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; Check for available memory (replace with actual method)
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; ... (e.g., call BIOS service for memory size or use a constant value)
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cmp available_memory, memory_threshold ; Compare with minimum required memory
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jb limited_memory_boot ; Jump if below threshold
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; ... (standard error handling for other scenarios)
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limited_memory_boot:
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; Perform minimal setup for limited memory boot
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; ... (disable non-essential features, adjust kernel parameters)
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; Load and jump to second stage bootloader (potentially with adjustments)
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; ... (modify loading logic if necessary)
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; Define variables used for calculation (adjust as needed)
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sector_count db 1 ; Number of sectors to skip before second stage (change if needed)
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second_stage_address equ 0x8000 ; Replace with actual address of your second stage bootloader
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available_memory equ 0x100000 ; Replace with actual memory size detection (1MB in this example)
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memory_threshold equ 0x0A0000 ; Example minimum memory required (adjust based on needs)
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; Padding and magic number (standard practice)
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times 510-($-$$) db 0
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dw 0xaa55
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@ -1,141 +1,91 @@
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[BITS 16]
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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[ORG 0x0000]
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; Stage 2 bootloader for ClassicOS ;
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; -------------------------------- ;
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; Loads the kernel, sets up tables, ;
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; and transitions to protected mode ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;
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; Assembler directives ;
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;;;;;;;;;;;;;;;;;;;;;;;;
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; tells the assembler that the program will be loaded at 0x8000
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; this is done by the first stage bootloader
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org 0x8000
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; we are targeting (x86) 16-bit real mode
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bits 16
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;;;;;;;;;;;;;;;;;
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; Jump to start ;
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;;;;;;;;;;;;;;;;;
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jmp start
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;;;;;;;;
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; Data ;
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;;;;;;;;
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; kernel file name
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kername db "KERNEL.BIN", 0
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;;;;;;;;;;;
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; Program ;
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;;;;;;;;;;;
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start:
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start:
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; Initialize stack
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xor ax, ax ; set up segment registers to segment 0 since
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MOV AX, 0x0000 ; Set up a segment for the stack
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mov ds, ax ; our addresses are already relative to 0x8000
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MOV SS, AX
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mov es, ax
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MOV SP, 0xFFFF ; Stack grows downwards from the top of the segment
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; Copy boot sector data to a safe location
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mov si, kername ; print kernel file name
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call mCopyBootSector
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call printstr
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; Load the kernel
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CALL load_kernel
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switch_to_protected_mode:
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; Load the kernel into memory
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CLI ; Disable interrupts
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; ...
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lgdt [gdt_descriptor] ; Load the global descriptor table
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MOV EAX, CR0
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OR EAX, 0x1 ; Set the PE (Protection Enable) bit
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MOV CR0, EAX
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; Far jump to flush CPU queue after changing to protected mode
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JMP CODE_SEG:init_pm ; CODE_SEG is the segment selector for code segment in GDT
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init_pm:
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; Update segment registers here
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; Set code segment register (CS) to point to code segment descriptor (selector 1)
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mov ax, 0x0001
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mov ds, ax ; Set data segment register (DS) to point to data segment descriptor (selector 2)
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mov es, ax ; Set other segment registers (ES, SS, etc.) as needed
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RET
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enable_a20:
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; Set up GDT, IDT, IVT
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cli ; Disable interrupts to prevent interference
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; ...
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call a20wait ; Wait for the keyboard controller to be ready
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mov al, 0xAD ; Command to disable keyboard
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out 0x64, al ; Send command to keyboard controller command port
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call a20wait ; Wait for the keyboard controller to be ready
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mov al, 0xD0 ; Command to read output port
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out 0x64, al ; Send command to keyboard controller command port
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call a20wait ; Wait for the keyboard controller to be ready
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in al, 0x60 ; Read current state of output port
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or al, 0x02 ; Set A20 bit
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out 0x64, al ; Send command to keyboard controller command port
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call a20wait ; Wait for the keyboard controller to be ready
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mov al, 0xD1 ; Command to write output port
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out 0x64, al ; Send command to keyboard controller command port
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call a20wait ; Wait for the keyboard controller to be ready
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mov al, 0xAE ; Command to re-enable keyboard
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out 0x64, al ; Send command to keyboard controller command port
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sti ; Re-enable interrupts
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ret
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; Wait for keyboard controller to be ready
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; Switch to protected mode
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a20wait:
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; ...
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in al, 0x64 ; Read keyboard controller status port
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test al, 0x02 ; Check if input buffer is full
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jnz a20wait ; Wait until it's not full
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ret
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; Enter kernel space and jump to the kernel entry point
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; Set up stack and start executing kernel's code
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JMP 0x1000:0x0000
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; ...
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; Code to set up flat memory model for protected mode
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; This involves setting up the segment registers with selectors
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; printstr routine, prints the string pointed by si using int 0x10 ;
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; that point to descriptors in the GDT that define a flat memory model
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; sets the direction flag to 0 ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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printstr:
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cld ; clear df flag - lodsb increments si
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printstr_loop:
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lodsb ; load next character into al, increment si
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or al, al ; sets zf if al is 0x00
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jz printstr_end
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||||||
|
mov ah, 0x0E ; teletype output (int 0x10)
|
||||||
|
int 0x10 ; print character
|
||||||
|
jmp printstr_loop
|
||||||
|
printstr_end:
|
||||||
|
ret ; return to caller address
|
||||||
|
|
||||||
limit = 0x00CFFFFFh ; Define limit as a separate variable within gdt_struct
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
||||||
|
; halt routine - infinite loop ;
|
||||||
; Placeholder instruction to satisfy NASM
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
||||||
dummy_instruction DB 0x90 ; NOP instruction as a placeholder
|
halt:
|
||||||
|
|
||||||
gdt_struct:
|
|
||||||
|
|
||||||
base_addr equ 0x0000000
|
|
||||||
|
|
||||||
; Null descriptor (ignored)
|
|
||||||
dd base_addr, 0 ; Both values are zero for a null descriptor
|
|
||||||
|
|
||||||
; Code segment descriptor (flat memory model)
|
|
||||||
dd base_addr, limit
|
|
||||||
db 0x9A
|
|
||||||
db 0xCF
|
|
||||||
|
|
||||||
; Data segment descriptor (flat memory model)
|
|
||||||
dd base_addr, limit
|
|
||||||
db 0x92
|
|
||||||
db 0xCF
|
|
||||||
|
|
||||||
; Macro to copy boot sector data to a safe location
|
|
||||||
mCopyBootSector:
|
|
||||||
pusha ; Save all general-purpose registers
|
|
||||||
mov si, 0x7C00 ; Source address: where BIOS loads the boot sector
|
|
||||||
mov di, 0x6000 ; Destination address: safe memory area
|
|
||||||
mov cx, 512 ; Number of bytes to copy (size of boot sector)
|
|
||||||
cld ; Clear direction flag to increment SI and DI
|
|
||||||
copy_loop:
|
|
||||||
lodsb ; Load byte at address DS:SI into AL, increment SI
|
|
||||||
stosb ; Store byte from AL to address ES:DI, increment DI
|
|
||||||
loop copy_loop ; Decrement CX; if CX != 0, repeat loop
|
|
||||||
popa ; Restore all general-purpose registers
|
|
||||||
ret
|
|
||||||
|
|
||||||
; Subroutine to load the kernel
|
|
||||||
load_kernel:
|
|
||||||
; Disable interrupts
|
|
||||||
cli
|
cli
|
||||||
|
jmp halt
|
||||||
|
|
||||||
; Setup disk parameters
|
;;;;;;;;;;;
|
||||||
; ... (set CH, CL, DH, DL for LBA, set DX for drive number)
|
; Padding ;
|
||||||
|
;;;;;;;;;;;
|
||||||
|
; $ is the address of the current line, $$ is the base address for
|
||||||
|
; this program.
|
||||||
|
; the expression is expanded to 510 - ($ - 0x8000), or
|
||||||
|
; 510 + 0x8000 - $, which is, in other words, the number of bytes
|
||||||
|
; before the address 510 + 0x8000 (= 0x80FD), where the 0xAA55
|
||||||
|
; signature shall be put.
|
||||||
|
times 510 - ($ - $$) db 0x00
|
||||||
|
|
||||||
; Calculate load address for kernel
|
;;;;;;;;;;;;;;;;;;
|
||||||
; ... (set ES:BX to the target memory address)
|
; BIOS signature ;
|
||||||
|
;;;;;;;;;;;;;;;;;;
|
||||||
; Read sectors from disk into memory
|
dw 0xAA55
|
||||||
mov ah, 0x02 ; Read sectors function
|
|
||||||
mov al, 1 ; Number of sectors to read
|
|
||||||
int 0x13 ; BIOS disk services
|
|
||||||
|
|
||||||
; Check for read error
|
|
||||||
jc .disk_error ; Carry flag set means an error occurred
|
|
||||||
|
|
||||||
; Enable A20 line if necessary
|
|
||||||
; ... (implementation depends on your system)
|
|
||||||
|
|
||||||
; Jump to the kernel's entry point
|
|
||||||
jmp 0x1000:0x0000 ; Assuming the kernel is loaded at 0x1000:0x0000
|
|
||||||
|
|
||||||
.disk_error:
|
|
||||||
; Handle disk read error
|
|
||||||
; ... (display error message or halt)
|
|
||||||
|
|
||||||
hlt ; Halt the system
|
|
||||||
|
|
||||||
; Function or Subroutine to switch to protected mode
|
|
||||||
switch_to_protected_mode:
|
|
||||||
CLI ; Disable interrupts
|
|
||||||
LGDT [gdt_descriptor] ; Load the global descriptor table
|
|
||||||
MOV EAX, CR0
|
|
||||||
OR EAX, 0x1 ; Set the PE (Protection Enable) bit
|
|
||||||
MOV CR0, EAX
|
|
||||||
; Far jump to flush CPU queue after changing to protected mode
|
|
||||||
JMP CODE_SEG:init_pm ; CODE_SEG is the segment selector for code segment in GDT
|
|
||||||
|
|||||||
Loading…
Reference in New Issue
Block a user