Disk reading partly done

2025-11-17 20:46:21 +00:00
parent 7906c48a2e
commit 0222a7adb9
10 changed files with 261 additions and 21 deletions
--- a/source/bootload/boot.asm
+++ b/source/bootload/boot.asm
@@ -25,7 +25,7 @@ ebr_drive_number:           db 0 ; ignore
 ebr_signature:              db 29h ; boot signature, indicates that the next three fields are present (0x29)
 ebr_volume_id:              db 12h, 34h, 56h, 78h ; unique id for volume tracking
 ebr_volume_label:           db 'CrawShaw OS' ; must be 11 bytes
-ebr_system_id:              db 'FAT12   ' ' ; must be 8 bytes
+ebr_system_id:              db 'FAT12   ' ; must be 8 bytes

 main:
   ; Setup registers
@@ -117,6 +117,7 @@ found_kernel:
   mov ax, [di+26] ; di is the address of the kernel, 26 is the offset
   mov [kernel_cluster], ax

+   ; Setup registers for disk read
   mov ax, [bdb_reserved_sectors]
   mov bx, buffer
   mov cl, [bdb_sectors_per_fat]
@@ -334,7 +335,7 @@ print_string:
 	  pop si
 	  ret

-boot_text: db 'OK] Boot sequence begun', 0
+boot_text: db 'OK] Boot begun', 0
 kernel_found_text: db 'OK] Kernel located', 0
 kernel_loading: db 'OK] Loading kernel', 0
 disk_read_fail: db 'ERR] Disk read fail', 0
--- a/source/kernel/features/cli.asm
+++ b/source/kernel/features/cli.asm
@@ -17,6 +17,8 @@ os_start_cli:

 os_read_cli:
 	pusha
+	mov si, user_input
+	call os_upper_case ; Make the input uppercase so it's case insensitive

 .output_the_user_input:
 	call os_print_newline
--- a/source/kernel/features/disk.asm
+++ b/source/kernel/features/disk.asm
@@ -0,0 +1,175 @@
+; Reset the disk system using int 13h / AH = 00h
+disk_reset:
+   pusha
+   stc
+   mov ah, 00h
+   int 13h
+   popa
+   ret
+
+; ------------------------------------
+
+; Load the root directory into memory (into disk_buffer which is 24000h)
+disk_load_root:
+   pusha
+   mov ax, 19 ; First sector of root entry
+   call math_lba_to_chs ; Assigns ch, cl and dh the correct values
+   xor ax,ax
+   mov dl, [ebr_drive_number]  ; Drive number
+   mov ah, 02h  ; BIOS ah code for read disk sectors to memory
+   mov al, 0Ch  ; Root directory has 12 sectors
+
+   mov si, root_buffer		; ES:BX should point to our buffer
+   mov bx, si
+
+   ; repeat drive read 3 times (incase of random error)
+   mov di, 3 ; counter
+   ; This is basically
+   ; for di in range(3,1,1):
+   ; We test to see if we can read the disk 3 times
+.try_read_disk: ; Try read the floppy three times
+   ; When the disk is tried to be read, the CF flag will be
+   ; set if there's an error, so we just clear it to return it to
+   ; the default state
+   stc ; sets the cf flag
+   int 13h
+   jnc .done_read ; jump if cf = 0
+
+   call disk_reset ; Reset drivers of disk
+
+   dec di       ; di -= 1
+   test di, di   ; if di = 0
+   jnz .try_read_disk
+   jmp .disk_error
+.disk_error:
+   mov si, disk_read_fail
+   call os_print_string
+   popa
+   ret
+.done_read:
+   popa
+   ret
+
+; ---------------------------------------------
+
+; Reads a certain number of sectors into memory
+; int 13h/ah = 02h read disk sectors into memory
+; al = number of sectors to read
+; ch = cylinder number
+; cl = sector number
+; dh = head number
+; dl = drive number
+; es:bx = points to data buffer
+disk_read:
+   push ax
+   push bx
+   push cx
+   push dx
+   push di
+
+
+   ; cl = sector
+   ; ch = cylinder
+   ; dh = head
+   ; dl = drive
+   call math_lba_to_chs  ; Get the chs address
+
+   mov ah, 02h  ; BIOS ah code for read disk sectors to memory
+
+   ; repeat drive read 3 times (incase of random error)
+   mov di, 3 ; counter
+
+; This is basically
+; for di in range(3,1,1):
+; We test to see if we can read the disk 3 times
+.retry:
+   ; When the disk is tried to be read, the CF flag will be
+   ; set if there's an error, so we just clear it to return it to
+   ; the default state
+   stc ; sets the cf flag
+   int 13h
+   jnc .done_read ; jump if cf = 0
+
+   call .disk_reset ; Reset drivers of disk
+
+   dec di       ; di -= 1
+   test di, di   ; if di = 0
+   jnz .retry
+
+.fail_disk_read:
+   pop di
+   pop dx
+   pop cx
+   pop bx
+   pop ax
+   ret
+
+; int 13h / ah = 00h reset disk system
+.disk_reset:
+   pusha
+   mov ah, 0 ; Reset drive
+   stc
+   int 13h
+   jc .fail_disk_read
+   popa
+   ret
+
+.done_read:
+   pop di
+   pop dx
+   pop cx
+   pop bx
+   pop ax
+   ret
+
+; -------------------------------------
+
+disk_load_file:
+   pusha
+   mov di, fat12_file_name
+   call os_format_fat_filename
+
+   ; Prepare values
+   mov si, root_buffer
+   xor bx,bx
+.search_root:
+   mov di, fat12_file_name ; Move the name of the kernel into di
+   mov cx, 11 ; length of 'KERNEL  BIN'
+   push si ; Preserve si
+   repe cmpsb ; Repeat a comparison of bytes between file name and current bytes until it finds a match
+   pop si ; Retrieve si
+   je .found_file
+
+   add si, 32 ; increment di to the next directory entry
+   inc bx
+   cmp bx, [bdb_dir_entries_count] ; Have we reached the number of directories that exist
+   jl .search_root ; Repeat search
+
+   jmp .file_not_found ; If the last dir has been searched, then there is no kernel
+.found_file:
+   mov ax, [si+26]   ; ax is now a pointer to the pointer to the file relative to the data segments :D
+   add ax, 20h
+   mov [file_cluster], ax
+   ; Setup registers for disk read
+   mov bx, data_buffer
+   mov dl, [ebr_drive_number]
+
+   call disk_read ; Load file from disk into memory
+   jmp .done
+.file_not_found:
+   mov si, file_not_found
+   call os_print_string
+   jmp .done
+.done:
+   popa
+   ret
+
+
+
+section .data:
+   disk_read_fail: db 'Error: Could not read disk\n', 0
+   file_not_found: db 'File not found\n', 0
+   file_found: db 'File found\n', 0
+   loading_root: db 'Loading root diretory\n', 0
+   file_cluster: dw 0
+   fat12_file_name: db '           '
--- a/source/kernel/features/math.asm
+++ b/source/kernel/features/math.asm
@@ -5,6 +5,7 @@
 ; H = T % heads
 ; C = T / headers
 ; input, LBA index: ax
+; ouput:
 ; sector number: cl
 ; cylinder: ch
 ; head: dh
@@ -29,7 +30,7 @@
 ; cylinder (ch) = 02h
 ; head (cl) = 00h
 ; sector (dh) = 09h
-os_lba_to_chs:
+math_lba_to_chs:
    push ax
    push dx

--- a/source/kernel/features/text.asm
+++ b/source/kernel/features/text.asm
@@ -48,6 +48,31 @@ os_print_string:
 	popa
 	ret

+; This is similar to the previous, however it prints
+; raw output (including null) and prints the number
+; of character defined by ax
+; IN:
+; SI = pointer to start of string to be printed
+; AX = Length of string to print
+text_raw_output:
+	pusha
+
+	mov di, ax
+
+	mov ah, 0Eh			; int 10h teletype function, we're telling the BIOS we will print something
+
+.repeat:
+	lodsb				; Get char from si into al
+	int 10h				; Otherwise, print it
+	dec di
+	cmp di, 00h
+	je .done
+	jne .repeat
+.done:
+	popa
+	ret
+
+
 ; --------------------------------------------

 os_print_newline:
--- a/source/kernel/games/pong.asm
+++ b/source/kernel/games/pong.asm
@@ -48,24 +48,24 @@ game_pong:
   mov dx, [p1_y]
   sub dx, 5
   mov [p1_y], dx
-   jmp .detect_input
+   ret
 .p1_down:
   mov dx, [p1_y]
   add dx, 5
   mov [p1_y], dx
-   jmp .detect_input
+   ret

 ; Player 2 movements
 .p2_up:
   mov dx, [p2_y]
   sub dx, 5
   mov [p2_y], dx
-   jmp .detect_input
+   ret
 .p2_down:
   mov dx, [p2_y]
   add dx, 5
   mov [p2_y], dx
-   jmp .detect_input
+   ret

 ; Ball bouncing
 ; This should move the ball along one frame
@@ -97,17 +97,17 @@ game_pong:

   ; Player 1
   cmp al, 77h       ; Pressed 'w' (player 1 up)
-   je .p1_up
+   call .p1_up
   cmp al, 73h       ; Pressed 's' (player 1 down)
-   je .p1_down
+   call .p1_down

   ; Player 2
   cmp al, 5bh       ; Pressed '[' (player 2 up)
-   je .p2_up
+   call .p2_up
   cmp al, 27h       ; Pressed ''' (player 2 down)
-   je .p2_down
+   call .p2_down

-   call .bounce_ball
+   ;call .bounce_ball
   call .draw_screen

   jmp .detect_input
--- a/source/kernel/kernel.asm
+++ b/source/kernel/kernel.asm
@@ -1,12 +1,17 @@
-ORG 0h
+ORG 00h
 BITS 16
+root_buffer equ 24000h
+data_buffer equ 26000h

 start:
   mov si, boot_message
   call os_print_string

-   mov si, help_text
-   call os_print_string
+   call disk_load_root ; Loads the root directory into disk_buffer
+
+   ; Physical address = (segment * 16) + offset
+   mov si, file_name
+   call disk_load_file

   call os_start_cli
   hlt
@@ -14,7 +19,31 @@ start:
 halt:
   jmp halt

-boot_message: db 'OK] Kernel successfully loaded!\n', 0
+boot_message: db 'OK] Kernel successfully loaded!\n\n', 0
+file_name: db 'hello.cws', 0
+
+; Define Fat12 header
+bdb_oem:                    db 'MSWIN4.1' ; ignore
+bdb_bytes_per_sector:       dw 200h ; = 512d
+bdb_sectors_per_cluster:    db 01h ; sector = cluster
+bdb_reserved_sectors:       dw 01h
+bdb_fat_count:              db 02h  ; We've got a fat1 and fat2
+bdb_dir_entries_count:      dw 0E0h ; Maximum number of root directory entries
+bdb_total_sectors:          dw 0B40h ; = 2880d
+bdb_media_descriptor_type:  db 0F0h ; ignore
+bdb_sectors_per_fat:        dw 09h
+bdb_sectors_per_track:      dw 12h ; = 18d
+bdb_number_of_heads:        dw 02h ; top and bottom of the floppy disk
+bdb_hidden_sectors:         dd 0 ; ignore
+bdb_large_sector_count:     dd 0 ; total sector count for fat32 (0 for fat12 or fat16)
+
+; extended boot record
+ebr_drive_number:           db 0 ; ignore
+                            db 0 ; ignore
+ebr_signature:              db 29h ; boot signature, indicates that the next three fields are present (0x29)
+ebr_volume_id:              db 12h, 34h, 56h, 78h ; unique id for volume tracking
+ebr_volume_label:           db 'CrawShaw OS' ; must be 11 bytes
+ebr_system_id:              db 'FAT12   ' ; must be 8 bytes

 ; ------------------------------------------------------------------
 ; FEATURES -- Code to pull into the kernel
@@ -25,5 +54,8 @@ boot_message: db 'OK] Kernel successfully loaded!\n', 0
 	%INCLUDE "source/kernel/features/strings.asm"
 	%INCLUDE "source/kernel/features/graphics.asm"
    %INCLUDE "source/kernel/features/disk.asm"
+    %INCLUDE "source/kernel/features/math.asm"
 ; GAMES -- Games that I wrote for it
 	%INCLUDE "source/kernel/games/pong.asm"
+
+