--- /dev/null
+; -*- fundamental -*- (asm-mode sucks)
+; $Id$
+; ****************************************************************************
+;
+; memdisk.asm
+;
+; A program to emulate an INT 13h disk BIOS from a "disk" in extended
+; memory.
+;
+; Copyright (C) 2001 H. Peter Anvin
+;
+; This program is free software; you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
+; USA; either version 2 of the License, or (at your option) any later
+; version; incorporated herein by reference.
+;
+; ****************************************************************************
+
+ org 0h
+
+%define SECTORSIZE_LG2 9 ; log2(sector size)
+%define SECTORSIZE (1 << SECTORSIZE_LG2)
+
+MyStack equ 1024
+
+ ; Parameter registers definition; this is the definition
+ ; of the stack frame.
+%define P_DS word [bp+34]
+%define P_ES word [bp+32]
+%define P_EAX dword [bp+28]
+%define P_AX word [bp+28]
+%define P_AL byte [bp+28]
+%define P_AH byte [bp+29]
+%define P_ECX dword [bp+24]
+%define P_CX word [bp+24]
+%define P_CL byte [bp+24]
+%define P_CH byte [bp+25]
+%define P_EDX dword [bp+20]
+%define P_DX word [bp+20]
+%define P_DL byte [bp+20]
+%define P_DH byte [bp+21]
+%define P_EBX dword [bp+16]
+%define P_BX word [bp+16]
+%define P_BL byte [bp+16]
+%define P_BH byte [bp+17]
+%define P_EBP dword [bp+8]
+%define P_BP word [bp+8]
+%define P_ESI dword [bp+4]
+%define P_SI word [bp+4]
+%define P_EDI dword [bp]
+%define P_DI word [bp]
+
+ section .text
+Int13Start:
+ ; See if DL points to our class of device (FD, HD)
+ push dx
+ xor dl,[cs:DriveNo]
+ pop dx
+ js .nomatch ; If SF=0, we have a match here
+ cmp dl,[cs:DriveNo]
+ je .our_drive
+ jb .nomatch ; Drive < Our drive
+ dec dl ; Drive > Our drive, adjust drive #
+.nomatch:
+ jmp far [OldInt13]
+
+.our_drive:
+ mov [cs:Stack],sp
+ mov [cs:SavedAX],ax
+ mov ax,ss
+ mov [cs:Stack+2],ax
+ mov ax,cs
+ mov ss,ax
+ mov sp,MyStack
+ push ds
+ push es
+ mov ds,ax
+ mov es,ax
+ mov ax,[SavedAX]
+ pushad
+ mov bp,sp
+ cmp ah,Int13FuncsMax
+ jae Invalid
+ xor al,al ; AL = 0 is standard entry condition
+ mov di,ax
+ shr di,7
+ call [Int13Funcs+di]
+
+Done: ; Standard routine for return
+ mov [LastStatus],ah
+ mov P_AX,ax
+ cmp ah,1
+DoneWeird:
+ setnb al ; AL <- (AH > 0) ? 1 : 0 (CF)
+ lds bx,[Stack] ; DS:BX <- Old stack pointer
+ mov [bx+4],al ; Low byte of old FLAGS -> arithmetric flags
+ popad
+ pop es
+ pop ds
+ lss sp,[cs:Stack]
+ iret
+
+Reset:
+ ; Reset affects multiple drives, so we need to pass it on
+ pop ax ; Drop return address
+ mov [LastStatus], byte 0
+ popad
+ pop es
+ pop ds
+ lss sp,[cs:Stack]
+ and dl,80h ; Clear all but the type bit
+ jmp far [OldInt13]
+
+Invalid:
+ mov ax,0100h ; Unsupported function
+ ret
+
+GetDriveType:
+ pop ax ; Drop return address
+ mov ah,[DriveNo]
+ shr ah,7
+ or ah,02h ; CF = 0
+ mov P_AH,ah
+ mov [LastStatus],byte 0 ; Success, but AH returns a value
+ jmp short DoneWeird
+
+GetStatus:
+ mov ah,[LastStatus] ; Copy last status
+ ret
+
+CheckIfReady: ; These are always-successful noop functions
+Recalibrate:
+InitWithParms:
+DetectChange:
+success:
+ xor ax,ax ; Always successful
+ ret
+
+Read:
+ call setup_regs
+do_copy:
+ call bcopy
+ movzx ax,P_AL ; AH = 0, AL = transfer count
+ ret
+
+Write:
+ call setup_regs
+ xchg esi,edi
+ jmp short do_copy
+
+ ; These verify one sector only
+Seek:
+ mov P_AL,1
+
+ ; Verify integrity; just bounds-check
+Verify:
+ call setup_regs ; Returns error if appropriate
+ jmp short success
+
+GetParms:
+ ; We need to get the "number of drives" from the BIOS
+ mov dl,P_DL
+ inc dl ; The drive whose number we're stealing
+ mov ah,08h
+ int 13h
+ inc dl ; Add ourselves to the count
+ mov P_DL,dl ; Drive count
+ mov P_DI,di ; Steal the diskette parameter table if applicable
+ mov ax,es
+ mov P_ES,ax
+ mov bl,[DriveType]
+ mov P_BL,bl
+ mov ax,[Cylinders]
+ dec ax ; We report the highest #, not the count
+ or ah,[Sectors]
+ xchg al,ah
+ mov P_CX,ax
+ mov al,[Heads]
+ dec al
+ mov P_DH,al
+ xor ax,ax
+ ret
+
+ ; Convert a CHS address in CX/DH into an LBA in EAX
+chstolba:
+ xor ebx,ebx
+ mov bl,cl ; Sector number
+ and bl,3Fh
+ dec bx
+ mov si,dx
+ mov ax,[Heads]
+ shr cl,6
+ xchg cl,ch ; Now CX <- cylinder number
+ mul cx ; DX:AX <- AX*CX
+ shr si,8 ; SI <- head number
+ add ax,si
+ adc dx,byte 0
+ shl edx,16
+ or eax,edx
+ mul dword [Sectors]
+ add eax,ebx
+ ret
+
+ ; Set up registers as for a "Read", and compares against disk size
+setup_regs:
+ call chstolba
+ movzx edi,P_BX ; Get linear address of target buffer
+ movzx ecx,P_ES
+ shr ecx,4
+ add edi,ecx
+ movzx ecx,P_AL
+ lea ebx,[eax+ecx]
+ mov esi,eax
+ shr esi,SECTORSIZE_LG2
+ add esi,[DiskBuf]
+ cmp ebx,[DiskSize]
+ jae .overrun
+ shr ecx,SECTORSIZE_LG2-1
+ ret
+
+.overrun: pop ax ; Drop return address
+ mov ax,0400h ; Sector not found
+ ret
+
+int15_e820:
+ cmp edx,534D4150h
+ jne near oldint15
+ cmp ecx,20 ; Need 20 bytes
+ jb err86
+ push edx ; "SMAP"
+ push esi
+ push edi
+ and ebx,ebx
+ jne .renew
+ mov ebx,[E820Table]
+.renew: mov esi,ebx
+ xor edi,edi
+ mov di,cs
+ shr di,4
+ add edi,E820Buf
+ mov ecx,24/2
+ call bcopy
+ add ebx, byte 12
+ pop edi
+ pop esi
+ mov eax,[cs:E820Buf]
+ mov [es:di],eax
+ mov eax,[cs:E820Buf+4]
+ mov [es:di+4],eax
+ mov eax,[cs:E820Buf+12]
+ mov [es:di+8],eax
+ mov eax,[cs:E820Buf+16]
+ mov [es:di+12],eax
+ mov eax,[cs:E820Buf+8]
+ mov [es:di+16],eax
+ cmp dword [cs:E820Buf+20], byte -1
+ jne .notdone
+ xor ebx,ebx ; Done with table
+.notdone:
+ pop eax ; "SMAP"
+ mov ecx,20 ; Bytes loaded
+int15_success:
+ mov byte [bp+12], 02h ; Clear CF
+ pop bp
+ iret
+
+err86:
+ mov byte [bp+12], 03h ; Set CF
+ mov ah,86h
+ pop bp
+ iret
+
+Int15Start:
+ push bp
+ mov bp,sp
+ cmp ax,0E820h
+ je near int15_e820
+ cmp ax,0E801h
+ je int15_e801
+ cmp ax,0E881h
+ je int15_e881
+ cmp ah,88h
+ je int15_88
+oldint15: pop bp
+ jmp far [cs:OldInt15]
+
+int15_e801:
+ mov ax,[cs:Mem1MB]
+ mov cx,ax
+ mov bx,[cs:Mem16MB]
+ mov dx,ax
+ jmp short int15_success
+
+int15_e881:
+ mov eax,[cs:Mem1MB]
+ mov ecx,eax
+ mov ebx,[cs:Mem16MB]
+ mov edx,eax
+ jmp short int15_success
+
+int15_88:
+ mov ax,[cs:MemInt1588]
+ jmp short int15_success
+
+;
+; Routine to copy in/out of high memory
+; esi = linear source address
+; edi = linear target address
+; ecx = 16-bit word count
+;
+; Assumes cs = ds = es
+;
+bcopy:
+ push eax
+ push ebx
+ push edx
+ push ebp
+ push esi
+ push edi
+.copy_loop:
+ push ecx
+ cmp ecx,8000h
+ jna .safe_size
+ mov ecx,8000h
+.safe_size:
+ push ecx
+ mov eax, esi
+ mov [Mover_src1], si
+ shr eax, 16
+ mov [Mover_src1+2], al
+ mov [Mover_src2], ah
+ mov eax, edi
+ mov [Mover_dst1], di
+ shr eax, 16
+ mov [Mover_dst1+2], al
+ mov [Mover_dst2], ah
+ mov si,Mover
+ mov ah, 87h
+ int 15h
+ pop eax
+ pop ecx
+ pop edi
+ pop esi
+ jc .error
+ lea esi,[esi+2*eax]
+ lea edi,[edi+2*eax]
+ sub ecx, eax
+ jnz .copy_loop
+ ; CF = 0
+.error:
+ pop ebp
+ pop edx
+ pop ebx
+ pop eax
+ ret
+
+ section .data
+Int13Funcs dw Reset ; 00h - RESET
+ dw GetStatus ; 01h - GET STATUS
+ dw Read ; 02h - READ
+ dw Write ; 03h - WRITE
+ dw Verify ; 04h - VERIFY
+ dw Invalid ; 05h - FORMAT TRACK
+ dw Invalid ; 06h - FORMAT TRACK AND SET BAD FLAGS
+ dw Invalid ; 07h - FORMAT DRIVE AT TRACK
+ dw GetParms ; 08h - GET PARAMETERS
+ dw InitWithParms ; 09h - INITIALIZE CONTROLLER WITH DRIVE PARAMETERS
+ dw Invalid ; 0Ah
+ dw Invalid ; 0Bh
+ dw Seek ; 0Ch - SEEK TO CYLINDER
+ dw Reset ; 0Dh - RESET HARD DISKS
+ dw Invalid ; 0Eh
+ dw Invalid ; 0Fh
+ dw CheckIfReady ; 10h - CHECK IF READY
+ dw Recalibrate ; 11h - RECALIBRATE
+ dw Invalid ; 12h
+ dw Invalid ; 13h
+ dw Invalid ; 14h
+ dw GetDriveType ; 15h - GET DRIVE TYPE
+ dw DetectChange ; 16h - DETECT DRIVE CHANGE
+Int13FuncsEnd equ $
+Int13FuncsMax equ (Int13FuncsEnd-Int13Funcs) >> 1
+
+DriveNo db 0 ; Our drive number
+DriveType db 0 ; Our drive type (floppies)
+LastStatus db 0 ; Last return status
+
+ alignb 4, db 0
+Cylinders dw 0 ; Cylinder count
+Heads dw 0 ; Head count
+Sectors dd 0 ; Sector count (zero-extended)
+DiskSize dd 0 ; Size of disk in blocks
+DiskBuf dd 0 ; Linear address of high memory disk
+
+E820Table dd 0 ; E820 table in high memory
+Mem1MB dd 0 ; 1MB-16MB memory amount (1K)
+Mem16MB dd 0 ; 16MB-4G memory amount (64K)
+MemInt1588 dw 0 ; 1MB-65MB memory amount (1K)
+
+ alignb 8, db 0
+Mover dd 0, 0, 0, 0 ; Must be zero
+ dw 0ffffh ; 64 K segment size
+Mover_src1: db 0, 0, 0 ; Low 24 bits of source addy
+ db 93h ; Access rights
+ db 00h ; Extended access rights
+Mover_src2: db 0 ; High 8 bits of source addy
+Mover_dst1: db 0, 0, 0 ; Low 24 bits of target addy
+ db 93h ; Access rights
+ db 00h ; Extended access rights
+Mover_dst2: db 0 ; High 8 bits of source addy
+
+ section .bss
+OldInt13 resd 1 ; INT 13h in chain
+OldInt15 resd 1 ; INT 15h in chain
+Stack resd 1 ; Saved SS:SP on invocation
+E820Buf resd 6 ; E820 fetch buffer
+SavedAX resw 1 ; AX saved during initialization
projects / platform / upstream / syslinux.git / commitdiff