Implement syscall interface and version data
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576b2c6546
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145
src/@rdos.asm
145
src/@rdos.asm
@ -1,6 +1,21 @@
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org 0x700
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cseg equ 0x0
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jmp init
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%include "version.inc"
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jmp _entry
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banner db "RDOS KERNEL 1.0", 0x0A, 0x0D, '$', 0x1A
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_entry call .l01
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.l01 pop ax
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sub ax, .l01
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mov cl, 4
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shr ax, cl
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mov cx, cs
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add cx, ax
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push cx
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mov ax, start
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push ax
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retf
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;;; Character I/O
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@ -138,10 +153,15 @@ gets mov si, dx
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call putc
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ret
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;;; System functions
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; Return OS version from version.inc
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ver mov bx, bdosver | 0x1000
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ret
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;;; Disk i/o
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%include "bpb.inc"
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%include "farptr.inc"
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; dflags bitfields
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DRVLOG equ 0x01 ; bit 0 - drive logged in (see drvnum)
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@ -150,23 +170,8 @@ DRVEXT equ 0x04 ; bit 2 - EBIOS supported
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DIRTY equ 0x08 ; bit 3 - dskbuf dirty
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DRVCHS equ 0x10 ; bit 4 - CHS geometry known
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align 16
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; IBM Interrupt Sharing Protocol structure
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i13isp jmp short int13i
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dw 0,0xFFFF
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dw 0x424B
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db 0
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iret
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align 16
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; Entry point when user program calls int13h
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; TODO: flush buffer and log out drive
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int13i call int13
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iret
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; Wrapper around int 13h
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int13 pushf
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call far [i13isp+2]
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int13 int 0x13
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; TODO: on error: reset & retry
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; TODO: record errors
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; TODO: multi-track reading
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@ -209,10 +214,10 @@ getprm test byte [dflags], DRVEXT
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test ax, ax
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jz .ret
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; copy BIOS dpt table over ours
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mov dx, dpt
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mov bx, di
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mov cx, 11
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call lodfar
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;mov dx, dpt
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;mov bx, di
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;mov cx, 11
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;call lodfar
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.ret ret
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; select a drive for io
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@ -379,14 +384,13 @@ flush test word [cs:dflags], DIRTY
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; Sector number is read from [drvseek]
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diskio mov cl, 1 ; read len
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; DS := ES := CS
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call rstseg
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mov ds, [cs:dseg]
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; check if ebios supported
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test word [dflags], DRVEXT
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jz .noext
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; set up regs for ebios call
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mov ax, cx
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xchg ax, cx
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or ah, 0x40
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mov si, dap
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jmp .do
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; check if we can skip controller reset
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.noext test word [dflags], DRVCTL
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@ -419,15 +423,19 @@ diskio mov cl, 1 ; read len
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; shuffle values around for bios
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xchg ax, cx
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xchg dh, dl
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mov bx, dskbuf
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.do mov dl, [biosnum]
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; ah: subfunction selected via cx previously
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; al: 1 = reading 1 sector
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; cx: sector and cylinder number
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; dh: head number
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; dl: drive number
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; bx: offset to disk buffer
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push es
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push si
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mov si, dap
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les bx, [si+4]
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call int13
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pop si
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pop es
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jc .err
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; clear dirty flag on success
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and word [dflags], ~DIRTY
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@ -439,39 +447,6 @@ diskio mov cl, 1 ; read len
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stc
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ret
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init mov ax, cs
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; boot failure if loaded wrong
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cmp ax, cseg
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je $+4
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int 0x18
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call rstseg
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; fetch current DPT
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les bx, [4*0x1E]
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mov dx, dpt
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mov cx, 11
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call lodfar
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; set interrupt vector
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mov word [4*0x1E], dpt
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mov word [4*0x1E+2], ds
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; save int 13 handler
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les bx, [4*0x13]
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mov [i13isp+2], bx
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mov [i13isp+4], es
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; install ours
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mov word [4*0x13], int13i
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mov [4*0x13+2], cs
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; install int21h handler
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mov word [4*0x21], int21h
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mov [4*0x21+2], cs
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mov dl, 0x36
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mov ah, 2
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int 0x21
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halt hlt
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jmp halt
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;;; Export functions as syscalls
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; SP, BP, SI, DI and ES must be preserved by kernel code
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; DL, DX or DS:DX is input argument from prog
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@ -494,7 +469,9 @@ intE0h push bx
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; bx = syscall number
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; stack must be -> BX IP CS FL
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; for return to prog
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sysc add bx, bx
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sysc sti
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cld
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add bx, bx
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mov bx, [cs:bx+stab]
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test bh, srw >> 8 ; fork off bx returns
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jnz .l02
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@ -537,6 +514,38 @@ sysc add bx, bx
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pop dx
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ret
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start xor ax, ax
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mov ds, ax
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; install int20h handler
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mov word [4*0x20], start
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mov [4*0x20+2], cs
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; install int21h handler
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mov word [4*0x21], int21h
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mov [4*0x21+2], cs
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; install intE0h handler
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mov word [4*0xE0], intE0h
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mov [4*0xE0+2], cs
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mov ax, cs
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mov ds, ax
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mov [dseg], ax
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; print banner
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mov dx, banner
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call puts
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; read cmdline
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mov dl, '>'
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call putc
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mov dx, inbuf
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mov byte [inbuf], 72
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call gets
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halt sti
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hlt
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jmp halt
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section .rodata
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; syscall table
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@ -549,10 +558,10 @@ stab dw 0 ; 0 reboot
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dw 0 ; 6 direct console i/o
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dw 0 ; 7 read i/o byte
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dw 0 ; 8 get i/o byte
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dw 0 ; 9 string output
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dw 0 ; 10 string input
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dw puts ; 9 string output
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dw gets ; 10 string input
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dw 0 ; 11 console status
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dw 0 ; 12 get version number
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dw ver ; 12 get version number
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dw 0 ; 13 reset disks
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dw 0 ; 14 set drive
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dw 0 ; 15 open file
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@ -587,7 +596,8 @@ section .data
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dap db 0x10, 0
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dw 1
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dw dskbuf, cseg
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dw dskbuf
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dseg dw 0
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drvseek dw 0,0,0,0
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; bit 0 (1) - drive logged in (see drvnum)
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@ -603,9 +613,6 @@ drvnum resb 1
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; number, just for bios
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biosnum resb 1
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; DPT tables for 4 floppy drives
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dpt resb 4*14
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; Information for logged in drive
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drvss resb 1 ; sector size, 2^(7+n) bytes
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drvcs resb 1 ; cluster size, 2^(7+n) bytes
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@ -622,3 +629,5 @@ drvfn resb 2 ; sectors per fat table
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; disk buffer for I/O operations
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alignb 2
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dskbuf resb 1024
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inbuf resb 128
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@ -1,46 +0,0 @@
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; reset segments
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rstseg mov ax, cs
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mov ds, ax
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mov es, ax
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ret
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; copy to far memory
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; IN es:bx far memory ptr (preserved)
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; ds:dx local ptr (preserved)
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; cx number of bytes to transfer
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; OUT cx set to zero
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; si & di trashed
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stofar mov si, dx
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mov di, bx
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rep movsb
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ret
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; copy from far memory
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; IN es:bx far memory ptr (preserved)
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; ds:dx local ptr (preserved)
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; cx number of bytes to copy
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; OUT cx set to zero
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; si & di trashed
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lodfar call swpds
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mov si, bx
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mov di, dx
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rep movsb
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; exchange es and ds
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swpds push ds
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push es
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pop ds
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pop es
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ret
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; normalize ptr in ds:dx
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norm mov ax, ds
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mov cl, 4
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push dx
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ror dx, cl
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and dh, 0xF
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add ax, dx
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mov ds, ax
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pop dx
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and dx, 0xF
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ret
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2
src/version.inc
Normal file
2
src/version.inc
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@ -0,0 +1,2 @@
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bdosver equ 0x10 ; CP/M 1.0
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bdosrev equ 0
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