kernel: implement diskio using drive table
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4a294ee21c
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f0a000b7d1
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@ -39,17 +39,18 @@ intlp: movsw
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stosw
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loop intlp
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; file descriptor 0 = CON
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mov word [fd_table], con_ftab
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; print banner
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mov dx, banner
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mov cx, 13
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mov bx, 0
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call fd_write
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call drives_init
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mov dl, 0
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call drive_select
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xor ax, ax
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xor dx, dx
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call drive_seek
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call drive_read
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mov ax, [diskbuf+0x1FE]
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int 3
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loop: int 0x28
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jmp loop
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@ -235,12 +236,7 @@ fputc: push ax
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pop ax
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iret
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%include "kernel/fd.asm"
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%include "kernel/con.asm"
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%include "kernel/drive.asm"
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%include "kernel/diskio.asm"
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%include "kernel/fat.asm"
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zero: dw 0
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@ -1,22 +0,0 @@
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con_ftab: dw con_read
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dw con_write
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con_read: stc
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ret
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con_write: push si
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push bx
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push cx
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test cx, cx
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jz .end
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mov si, dx
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mov ah, 0x0E
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xor bx, bx
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.loop: lodsb
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int 0x10
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loop .loop
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pop cx
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.end: pop bx
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pop si
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ret
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@ -1,192 +0,0 @@
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section .bss
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disk_buffer:
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resb 512
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disk_current:
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resb 1
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lba_supported:
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resb 1
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; Seek state and geometry info for CHS access
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disk_chs: ; DL, DH, CL, CH for int 13h CHS functions
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resb 4
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disk_spc: ; sectors per cylinder = heads * spt
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resw 1
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disk_spt:
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resb 1
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; Partition conf from MBR or dummy for floppies
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part_offset:
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resd 1
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part_size:
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resd 1
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dap: ; Disk access packet for EBIOS extensions
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resw 1
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dap_sectors:
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resw 1
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dap_buffer:
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resd 1
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dap_sector:
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resq 1
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section .text
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; Convert between drive number and BIOS dl
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; Bidirectional mapping
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; 0 <-> 0, 1 <-> 1, 2 <-> 0x80, 3 <-> 0x81
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dnconv: mov cx, 7
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ror dx, 1
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rol dl, 1
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dncl: rcl dl, 1
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rcr dh, 1
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loop dncl
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xchg dh, dl
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ret
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; Select a drive for I/O
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; This leave the first sector of the partition in the buffer
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; IN dl 0=A, 1=B, 2=C, 3=D
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select: mov byte [disk_current], 0xFF
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mov byte [lba_supported], 0
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call dnconv
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mov byte [disk_chs], dl
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cmp dl, 0x80
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jc select_floppy
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; detect EBIOS/LBA extensions
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mov ah, 0x41
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mov bx, 0x55AA
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int 0x13
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test cx, 1
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jz select_hdd
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cmp bx, 0xAA55
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jnz select_hdd
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mov byte [lba_supported], 1
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jmp select_hdd
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select_floppy:
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push dx
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call seek_zero
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call read
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; load disk geometry
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mov ax, [disk_buffer+0x0B+bpb_spt]
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mov [disk_spt], ax
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mul word [disk_buffer+0x0B+bpb_nos]
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mov [disk_spc], ax
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; set partition size
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; we dont rely on the 'total sectors' given in the BPB
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; instead, we assume maximum cylinder
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; 1023 is the maximum encodable for int 13h
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lea di, [part_offset]
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xor ax, ax
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; partition offset = 0
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stosw
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stosw
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; partition size = 0x00010000 = 32MB
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stosw
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inc ax
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stosw
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pop dx
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ret
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select_hdd:
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push dx
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; load CHS geometry for drive
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mov ah, 0x8
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int 0x13
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xor ah, ah
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mov al, cl
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mov [disk_spt], ax
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mul byte dh
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mov [disk_spc], ax
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; load offset and size of first partition
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call seek_zero
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call read
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mov bx, disk_buffer+0x1BE
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lea si, [bx+8]
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lea di, [part_offset]
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mov cx, 4
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rep movsw
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; read bpb
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mov dx, [part_offset+2]
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mov ax, [part_offset]
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call seek
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call read
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pop dx
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ret
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; Set absolute sector number
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; IN dx:ax 32-bit sector number
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seek: push ax
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or ax, dx
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pop ax
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jz seek_zero
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test byte [lba_supported], 1
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jnz seek_lba
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; dx:ax = lba
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div word [disk_spc]
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xchg ax, dx
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; dx = cylinder, ax = head * spt + sector
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div byte [disk_spt]
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; dx = cylinder, al = head, ah = sector
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xchg dl, dh
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ror dl, 1
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ror dl, 1
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or dl, ah
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inc dx
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; dh bit 0-7: cylinder 0-7
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; dl bit 0-5: sector number 0-5
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; dl bit 6-7: cylinder 8-9
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; store
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mov byte [disk_chs+1], al
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mov word [disk_chs+2], dx
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ret
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seek_zero:
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; set chs data to first sector
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mov byte [disk_chs+1], 0
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mov word [disk_chs+2], 1
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; set lba data to first sector
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xor ax, ax
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xor dx, dx
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seek_lba:
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mov word [dap], 0x10
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mov word [dap_sectors], 1
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mov word [dap_buffer], disk_buffer
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mov [dap_buffer+2], cs
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lea di, [dap_sector]
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stosw
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mov ax, dx
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stosw
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xor ax, ax
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stosw
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stosw
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ret
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; Read a sector into buffer
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read: test byte [lba_supported], 1
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jnz read_lba
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mov ax, 0x0201
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mov dx, [disk_chs]
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mov cx, [disk_chs+2]
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lea bx, [disk_buffer]
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push cs
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pop es
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int 0x13
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ret
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read_lba:
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mov ah, 0x42
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mov dl, [disk_chs]
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lea si, [dap]
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int 0x13
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ret
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; Write a sector into buffer
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write: stc
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ret
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@ -16,6 +16,13 @@ drive_ptr: resw 1
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drive_table: resb (drives * drive_size)
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; DX and CX for int 13 CHS access
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chs_dx: resw 1
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chs_cx: resw 1
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; disk buffer for I/O operations
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diskbuf: resb 1024
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section .text
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drives_init: ; CX = number of floppy drives in the system
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@ -32,6 +39,7 @@ drives_init: ; CX = number of floppy drives in the system
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.loop: push cx
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push dx
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mov [bx+drive.biosnum], dl
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mov byte [bx+drive.flag], 1 ; 1 = drive letter used
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; query bios for floppy format
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mov ah, 8
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push bx
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@ -82,3 +90,79 @@ drives_init: ; CX = number of floppy drives in the system
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add bx, drive_size
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loop .loop
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ret
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; select drive
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; IN dl drive number
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drive_select: xor dh, dh
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mov ax, drive_size
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mul dx
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add ax, drive_table
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mov word [drive_ptr], ax
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ret
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; reset currently selected drive
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drive_reset: mov bx, [drive_ptr]
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mov dl, [bx+drive.biosnum]
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; our ptr = CX:BX
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lea bx, [bx+drive.dpt]
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mov cx, ds
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; toggle in our ptr
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mov si, [0x1E*4]
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xchg bx, [si]
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xchg cx, [si+2]
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; do the call
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xor ax, ax
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int 0x13
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pushf
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; restore original ptr
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xchg bx, [si]
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xchg cx, [si+2]
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; pass int 13 flags
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popf
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ret
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; query status of selected drive
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; OUT ah
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drive_status: mov bx, [drive_ptr]
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mov dl, [bx+drive.biosnum]
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mov ah, 1
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int 0x13
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ret
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; set sector for read/write operation
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; IN dx:ax 32-bit sector number
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drive_seek: mov bx, [drive_ptr]
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div word [bx+drive.spc]
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xchg ax, dx
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; dx = cylinder, ax = head * spt + sector
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div byte [bx+drive.dpt+dpt.lastsector]
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; dx = cylinder, al = head, ah = sector
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xchg dl, dh
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ror dl, 1
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ror dl, 1
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or dl, ah
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inc dx
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; al: head number
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; dh bit 0-7: cylinder bits 0-7
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; dl bit 0-5: sector bits 0-5
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; dl bit 6-7: cylinder bits 8-9
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xchg al, ah
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mov al, [bx+drive.biosnum]
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; store
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mov word [chs_dx], ax
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mov word [chs_cx], dx
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ret
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drive_read: mov ax, 0x0201
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mov cx, [chs_cx]
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mov dx, [chs_dx]
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mov bx, diskbuf
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int 0x13
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ret
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drive_write: mov ah, 0x0301
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mov cx, [chs_cx]
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mov dx, [chs_dx]
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mov bx, diskbuf
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int 0x13
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ret
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@ -1,32 +0,0 @@
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%define fd_num 32
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section .bss
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fd_table: resb (0x10 * fd_num)
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section .text
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fd_to_ptr: push cx
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mov cl, 4
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sal bx, cl
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add bx, fd_table
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pop cx
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ret
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fd_read: cmp bx, fd_num
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jnc fd_inv_hnd
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call fd_to_ptr
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; read ptr to ftab
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mov bx, [bx]
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; jmp to addr in ftab[0]
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jmp [bx]
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fd_write: cmp bx, fd_num
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jnc fd_inv_hnd
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call fd_to_ptr
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mov bx, [bx]
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jmp [bx+2]
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fd_inv_hnd: mov ax, 6
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stc
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ret
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