diff options
Diffstat (limited to 'diskio.asm')
| -rw-r--r-- | diskio.asm | 147 |
1 files changed, 126 insertions, 21 deletions
@@ -1,21 +1,126 @@ -;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; Reset the disk system -;; DL must be disk to reset -diskio_ResetDiskSystem: - pop ax - pop dx - push ax - xor ah, ah - int 0x13 - ret -;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -diskio_DumpBootSector: - xor bx, bx - mov es, bx - mov bx, diskio_SectorBuffer ; ES:BX = address - mov dl, [Drive] ; DL = Drive number - mov ah, 2 ; AH = Read command - int 0x13 ; Read sector - push diskio_SectorBuffer - call OutText - ret +; Cheers to the BOOT12 bootloader for a lot of these handy definitions.
+; Modified them slightly to fit the kernel's needs
+;; TO DO: Confirm that these aren't destroyed as kernel loads
+;%define s_per_clu 0x7C00+0x0D ; byte Sectors per cluster
+;%define s_b4_fat 0x7C00+0x0E ; word Sectors (in partition) before FAT
+;%define fats 0x7C00+0x10 ; byte Number of FATs
+;%define dir_ent 0x7C00+0x11 ; word Number of root directory entries
+;%define s_p_fat 0x7C00+0x16 ; word Sectors per FAT
+;%define s_p_t 0x7C00+0x18 ; word Sectors per track
+;%define heads 0x7C00+0x1A ; word Number of heads
+;%define s_b4_prt 0x7C00+0x1C ; dword Sectors before partition
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_disk_reset
+;; @param disk disk number to reset
+;; @return none
+;; Resets the disk system
+;;
+jaspos_disk_reset:
+ push dx
+ push ax
+ mov dl, [Drive] ; DL = drive #
+ xor ah, ah ; AH = 0 = reset disk system
+ int 0x13 ; Perform the reset
+ pop ax
+ pop dx
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_disk_readsector
+;; @param buffer memory buffer to write sector into
+;; @param sector relative sector number to load
+;; @return none
+;; Loads one sector from the boot disk into memory
+;;
+jaspos_disk_readsector:
+ pop bp ; Save CALL's address
+ pop cx ; Get sector number into CX
+ pop bx ; Get buffer location
+ push bp ; Push CALL's address back onto stack ready for RET
+
+ push cx
+ call jaspos_disk_make_chs ; Convert the sector number supplied into a useful CHS (cylinder, head, sector) triplet
+ ;mov dl, [Drive] ; DL = Drive number
+ ;xor dh, dh ; DH = Head
+ xor ch, ch ; CH = Track number
+ mov al, 1 ; AL = # Sectors to read
+ mov ah, 2 ; AH = Read command
+ int 0x13 ; Read sector
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_disk_make_chs
+;; @param sector relative sector number to load
+;; @return CHS registers ready for INT13
+;; Converts relative sector into CHS, ready for
+;; interrupt 13
+;;
+jaspos_disk_make_chs:
+ pop bp
+ pop ax
+ push bp
+
+ xor dx, dx ; DIV's input is DXAX - clear DX so we're only dividing AX
+ div word [s_per_track] ; Sectors per track
+ inc dl ; Sectors start at 1, not 0
+ mov cl, dl ; Sectors belong in CL for int 13h
+ mov ax, bx
+
+ xor dx, dx ; Now calculate the head
+ div word [s_per_track] ; Sectors per track
+
+ xor dx, dx
+ div word [heads] ; Floppy sides
+ mov dh, dl ; Head/side
+ mov ch, al ; Track
+
+ mov dl, [Drive] ; Set correct device
+
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_disk_get_info
+;; @param none
+;; @return none
+;; Load the boot sector into memory and patches
+;; the disk info (label, heads etc) into memory
+;; for use by kernel
+;;
+jaspos_disk_get_info:
+ call jaspos_disk_reset ;
+ jc jaspos.panic ; If the reset fails, just panic
+
+ ; We need to call INT13 manually, because jaspos_diskio_readsector
+ ; relies on having the disk info we're about to load, loaded.
+ ; Hooray for having to bootstrap
+ mov bx, free_ram ; Buffer location
+ mov dl, [Drive] ; DL = Drive number
+ xor dh, dh ; DH = Head
+ xor ch, ch ; CH = Track number
+ mov al, 1 ; AL = # Sectors to read
+ mov ah, 2 ; AH = Read command
+ int 0x13 ; Read sector
+
+ mov di, msgDiskLabel + 13 ; Load the disk label into the disk label message
+ mov si, free_ram+0x2B ; The label starts 0x2B bytes into the sector
+ mov cx, 11d ; Disk labels are 11 bytes long on FAT12
+ rep movsb ; Copy 11 bytes from the sector buffer into the inside of
+
+ mov cx, 25d ; There are 25d bytes that I want copied and saved
+ mov si, free_ram+0x0B ; Start copying from byte 0x0B
+ mov di, b_per_s ; Start storing at the b_per_s label
+ rep movsb ; Copy the bytes
+
+ ret ; the disk label message, thus filling it with the disk label
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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