This repository has been archived on 2023-08-20. You can view files and clone it. You cannot open issues or pull requests or push a commit.
Files
RescueBootCD/extra/syslinux-3.09/memdisk/memdisk.asm

760 lines
16 KiB
Plaintext

; -*- fundamental -*- (asm-mode sucks)
; $Id: memdisk.asm,v 1.29 2005/04/29 06:08:03 hpa Exp $
; ****************************************************************************
;
; memdisk.asm
;
; A program to emulate an INT 13h disk BIOS from a "disk" in extended
; memory.
;
; Copyright (C) 2001-2004 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., 53 Temple Place Ste 330,
; Boston MA 02111-1307, USA; either version 2 of the License, or
; (at your option) any later version; incorporated herein by reference.
;
; ****************************************************************************
%ifndef DEPEND
%include "../version.gen"
%endif
; %define DEBUG_TRACERS ; Uncomment to get debugging tracers
%ifdef DEBUG_TRACERS
%macro TRACER 1
call debug_tracer
db %1
%endmacro
%else ; DEBUG_TRACERS
%macro TRACER 1
%endmacro
%endif ; DEBUG_TRACERS
%define CONFIG_READONLY 0x01
%define CONFIG_RAW 0x02
%define CONFIG_BIGRAW 0x08 ; MUST be 8!
org 0h
%define SECTORSIZE_LG2 9 ; log2(sector size)
%define SECTORSIZE (1 << SECTORSIZE_LG2)
; 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_HAX word [bp+30]
%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_HCX word [bp+26]
%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_HDX word [bp+22]
%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_HBX word [bp+18]
%define P_HBXL byte [bp+18]
%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
; These pointers are used by the installer and
; must be first in the binary
Pointers: dw Int13Start
dw Int15Start
dw PatchArea
dw TotalSize
Int13Start:
; Swap stack
mov [cs:Stack],esp
mov [cs:SavedAX],ax
mov ax,ss
mov [cs:Stack+4],ax
mov ax,cs
mov ss,ax
mov sp,[cs:MyStack]
; See if DL points to our class of device (FD, HD)
push dx
push dx
xor dl,[cs:DriveNo]
pop dx
js .nomatch ; If SF=0, we have a class match here
jz .our_drive ; If ZF=1, we have an exact match
cmp dl,[cs:DriveNo]
jb .nomatch ; Drive < Our drive
dec dl ; Drive > Our drive, adjust drive #
.nomatch:
mov ax,[cs:SavedAX]
pushf
call far [cs:OldInt13]
pushf
push bp
mov bp,sp
cmp byte [cs:SavedAX+1],08h
je .norestoredl
cmp byte [cs:SavedAX+1],15h
jne .restoredl
test byte [bp+4],80h ; Hard disk?
jnz .norestoredl
.restoredl:
mov dl,[bp+4]
.norestoredl:
push ax
push ebx
push ds
mov ax,[bp+2] ; Flags
lds ebx,[cs:Stack]
mov [bx+4],al ; Arithmetric flags
pop ds
pop ebx
pop ax
pop bp
lss esp,[cs:Stack]
iret
.our_drive:
; Set up standard entry frame
push ds
push es
mov ds,ax
mov es,ax
mov ax,[SavedAX]
pushad
mov bp,sp ; Point BP to the entry stack frame
TRACER 'F'
; Note: AH == P_AH here
cmp ah,Int13FuncsMax
jae Invalid_jump
xor al,al ; AL = 0 is standard entry condition
mov di,ax
shr di,7 ; Convert AH to an offset in DI
call [Int13Funcs+di]
Done: ; Standard routine for return
mov P_AX,ax
DoneWeird:
TRACER 'D'
xor bx,bx
mov es,bx
mov bx,[StatusPtr]
mov [es:bx],ah ; Save status
and ah,ah
lds ebx,[Stack]
; This sets the low byte (the arithmetric flags) of the
; FLAGS on stack to either 00h (no flags) or 01h (CF)
; depending on if AH was zero or not.
setnz [bx+4] ; Set CF iff error
popad
pop es
pop ds
lss esp,[cs:Stack]
iret
Reset:
; Reset affects multiple drives, so we need to pass it on
TRACER 'R'
test dl,dl ; Always pass it on if we are resetting HD
js .pass_on ; Bit 7 set
; Some BIOSes get very unhappy if we pass a reset floppy
; command to them and don't actually have any floppies.
; This is a bug, but we have to deal with it nontheless.
; Therefore, if we are the *ONLY* floppy drive, and the
; user didn't request HD reset, then just drop the command.
xor ax,ax ; Bottom of memory
mov es,ax
; BIOS equipment byte, top two bits + 1 == total # of floppies
test byte [es:0x410],0C0h
jz success
; ... otherwise pass it to the BIOS
.pass_on:
pop ax ; Drop return address
popad ; Restore all registers
pop es
pop ds
lss esp,[cs:Stack] ; Restore the stack
and dl,80h ; Clear all but the type bit
jmp far [cs:OldInt13]
Invalid:
pop dx ; Drop return address
Invalid_jump:
TRACER 'I'
mov ah,01h ; Unsupported function
jmp short Done
GetDriveType:
test byte [DriveNo],80h
mov bl,02h ; Type 02h = floppy with changeline
jz .floppy
; Hard disks only...
inc bx ; Type = 03h
mov dx,[DiskSize] ; Return the disk size in sectors
mov P_DX,dx
mov cx,[DiskSize+2]
mov P_CX,cx
.floppy:
mov P_AH,bl ; 02h floppy, 03h hard disk
pop ax ; Drop return address
xor ax,ax ; Success...
jmp short DoneWeird ; But don't stick it into P_AX
GetStatus:
xor ax,ax
mov es,ax
mov bx,[StatusPtr]
mov ah,[bx] ; Copy last status
ret
ReadMult:
TRACER 'm'
Read:
TRACER 'R'
call setup_regs
do_copy:
TRACER '<'
call bcopy
TRACER '>'
movzx ax,P_AL ; AH = 0, AL = transfer count
ret
WriteMult:
TRACER 'M'
Write:
TRACER 'W'
test byte [ConfigFlags],CONFIG_READONLY
jnz .readonly
call setup_regs
xchg esi,edi ; Opposite direction of a Read!
jmp short do_copy
.readonly: mov ah,03h ; Write protected medium
ret
; Verify integrity; just bounds-check
Seek:
Verify:
call setup_regs ; Returns error if appropriate
; And fall through to success
CheckIfReady: ; These are always-successful noop functions
Recalibrate:
InitWithParms:
DetectChange:
SetMode:
success:
xor ax,ax ; Always successful
ret
GetParms:
TRACER 'G'
mov dl,[DriveCnt] ; Cached data
mov P_DL,dl
test byte [DriveNo],80h
jnz .hd
mov P_DI,DPT
mov P_ES,cs
mov bl,[DriveType]
mov P_BL,bl
.hd:
mov ax,[Cylinders]
dec ax ; We report the highest #, not the count
xchg al,ah
shl al,6
or al,[Sectors]
mov P_CX,ax
mov ax,[Heads]
dec ax
mov P_DH,al
;
; Is this MEMDISK installation check?
;
cmp P_HAX,'ME'
jne .notic
cmp P_HCX,'MD'
jne .notic
cmp P_HDX,'IS'
jne .notic
cmp P_HBX,'K?'
jne .notic
; MEMDISK installation check...
mov P_HAX,'!M'
mov P_HCX,'EM'
mov P_HDX,'DI'
mov P_HBX,'SK'
mov P_ES,cs
mov P_DI,MemDisk_Info
.notic:
xor ax,ax
ret
; Set up registers as for a "Read", and compares against disk size
setup_regs:
; Convert a CHS address in P_CX/P_DH into an LBA in eax
; CH = cyl[7:0]
; CL[0:5] = sector (1-based) CL[7:6] = cyl[9:8]
; DH = head
movzx ecx,P_CX
movzx ebx,cl ; Sector number
and bl,3Fh
dec ebx ; Sector number is 1-based
cmp bx,[Sectors]
jae .overrun
movzx edi,P_DH ; Head number
movzx eax,word [Heads]
cmp di,ax
jae .overrun
shr cl,6
xchg cl,ch ; Now (E)CX <- cylinder number
mul ecx ; eax <- Heads*cyl# (edx <- 0)
add eax,edi
mul dword [Sectors]
add eax,ebx
; Now eax = LBA, edx = 0
;
; setup_regs continues...
;
; Note: edi[31:16] and ecx[31:16] = 0 already
mov di,P_BX ; Get linear address of target buffer
mov cx,P_ES
shl ecx,4
add edi,ecx ; EDI = address to fetch to
movzx ecx,P_AL ; Sector count
mov esi,eax
add eax,ecx ; LBA of final sector + 1
shl esi,SECTORSIZE_LG2 ; LBA -> byte offset
add esi,[DiskBuf] ; Get address in high memory
cmp eax,[DiskSize] ; Check the high mark against limit
ja .overrun
shl ecx,SECTORSIZE_LG2-2 ; Convert count to 32-bit words
ret
.overrun: pop ax ; Drop setup_regs return address
mov ax,0200h ; Missing address mark
ret ; Return to Done
int15_e820:
cmp edx,534D4150h ; "SMAP"
jne near oldint15
cmp ecx,20 ; Need 20 bytes
jb err86
push ds
push cs
pop ds
and ebx,ebx
jne .renew
mov ebx,E820Table
.renew:
add bx,12 ; Advance to next
mov eax,[bx-4] ; Type
and eax,eax ; Null type?
jz .renew ; If so advance to next
mov [es:di+16],eax
mov eax,[bx-12] ; Start addr (low)
mov [es:di],eax
mov ecx,[bx-8] ; Start addr (high)
mov [es:di+4],ecx
mov eax,[bx] ; End addr (low)
mov ecx,[bx+4] ; End addr (high)
sub eax,[bx-12] ; Derive the length
sbb ecx,[bx-8]
mov [es:di+8],eax ; Length (low)
mov [es:di+12],ecx ; Length (high)
cmp dword [bx+8],-1 ; Type of next = end?
jne .notdone
xor ebx,ebx ; Done with table
.notdone:
mov eax,edx ; "SMAP"
pop ds
mov ecx,20 ; Bytes loaded
int15_success:
mov byte [bp+6], 02h ; Clear CF
pop bp
iret
err86:
mov byte [bp+6], 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,bx
jmp short int15_success
int15_e881:
mov eax,[cs:Mem1MB]
mov ecx,eax
mov ebx,[cs:Mem16MB]
mov edx,ebx
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 = 32-bit word count
;
; Assumes cs = ds = es
;
bcopy:
push eax
push ebx
push edx
push ebp
test byte [ConfigFlags],CONFIG_RAW
jz .anymode
smsw ax ; Unprivileged!
test al,01h
jnz .protmode
.realmode:
TRACER 'r'
; We're in real mode, do it outselves
pushfd
push ds
push es
cli
cld
xor ebx,ebx
mov bx,cs
shl ebx,4
lea edx,[Shaker+ebx]
mov [Shaker+2],edx
; Test to see if A20 is enabled or not
xor ax,ax
mov ds,ax
dec ax
mov es,ax
mov ax,[0]
mov bx,ax
xor bx,[es:10h]
not ax
mov [0],ax
mov dx,ax
xor dx,[es:10h]
not ax
mov [0],ax
or dx,bx
push dx ; Save A20 status
jnz .skip_a20e
mov ax,2401h ; Enable A20
int 15h
.skip_a20e:
mov dl,[ConfigFlags]
and dx,CONFIG_BIGRAW
add dx,8
; DX = 16 for BIGRAW, 8 for RAW
; 8 is selector for a 64K flat segment,
; 16 is selector for a 4GB flat segment.
lgdt [cs:Shaker]
mov eax,cr0
or al,01h
mov cr0,eax
mov bx,16 ; Large flat segment
mov ds,bx
mov es,bx
a32 rep movsd
; DX has the appropriate value to put in
; the registers on return
mov ds,dx
mov es,dx
and al,~01h
mov cr0,eax
pop es
pop ds
pop dx ; A20 status
and dx,dx
jnz .skip_a20d
mov ax,2400h ; Disable A20
int 15h
.skip_a20d:
popfd
jmp .done
.protmode:
TRACER 'p'
.anymode:
.copy_loop:
push esi
push edi
push ecx
cmp ecx,4000h
jna .safe_size
mov ecx,4000h
.safe_size:
push ecx ; Transfer size this cycle
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
shl cx,1 ; Convert to 16-bit words
int 15h
cli ; Some BIOSes enable interrupts on INT 15h
pop eax ; Transfer size this cycle
pop ecx
pop edi
pop esi
jc .error
lea esi,[esi+4*eax]
lea edi,[edi+4*eax]
sub ecx, eax
jnz .copy_loop
; CF = 0
.error:
.done:
pop ebp
pop edx
pop ebx
pop eax
ret
%ifdef DEBUG_TRACERS
debug_tracer: pushad
pushfd
mov bp,sp
mov bx,[bp+9*4]
mov al,[cs:bx]
inc word [bp+9*4]
mov ah,0Eh
mov bx,7
int 10h
popfd
popad
ret
%endif
section .data
alignb 2
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
%if 0
dw Invalid ; 17h
dw Invalid ; 18h
dw Invalid ; 19h
dw Invalid ; 1Ah
dw Invalid ; 1Bh
dw Invalid ; 1Ch
dw Invalid ; 1Dh
dw Invalid ; 1Eh
dw Invalid ; 1Fh
dw Invalid ; 20h
dw ReadMult ; 21h - READ MULTIPLE
dw WriteMult ; 22h - WRITE MULTIPLE
dw SetMode ; 23h - SET CONTROLLER FEATURES
dw SetMode ; 24h - SET MULTIPLE MODE
dw Invalid ; 25h - IDENTIFY DRIVE
dw Invalid ; 26h
dw Invalid ; 27h
dw Invalid ; 28h
dw Invalid ; 29h
dw Invalid ; 2Ah
dw Invalid ; 2Bh
dw Invalid ; 2Ch
dw Invalid ; 2Dh
dw Invalid ; 2Eh
dw Invalid ; 2Fh
dw Invalid ; 30h
dw Invalid ; 31h
dw Invalid ; 32h
dw Invalid ; 33h
dw Invalid ; 34h
dw Invalid ; 35h
dw Invalid ; 36h
dw Invalid ; 37h
dw Invalid ; 38h
dw Invalid ; 39h
dw Invalid ; 3Ah
dw Invalid ; 3Bh
dw Invalid ; 3Ch
dw Invalid ; 3Dh
dw Invalid ; 3Eh
dw Invalid ; 3Fh
dw Invalid ; 40h
dw EDDPresence ; 41h - EDD PRESENCE DETECT
dw EDDRead ; 42h - EDD READ
dw EDDWrite ; 43h - EDD WRITE
dw EDDVerify ; 44h - EDD VERIFY
dw Invalid ; 45h - EDD LOCK/UNLOCK MEDIA
dw Invalid ; 46h - EDD EJECT
dw EDDSeek ; 47h - EDD SEEK
dw EDDGetParms ; 48h - EDD GET PARAMETERS
%endif
Int13FuncsEnd equ $
Int13FuncsMax equ (Int13FuncsEnd-Int13Funcs) >> 1
alignb 8, db 0
Shaker dw ShakerEnd-$
dd 0 ; Pointer to self
dw 0
Shaker_RMDS: dd 0x0000ffff ; 64K data segment
dd 0x00009300
Shaker_DS: dd 0x0000ffff ; 4GB data segment
dd 0x008f9300
ShakerEnd equ $
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
dw 0ffffh ; 64 K segment size
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
Mover_dummy2: dd 0, 0, 0, 0 ; More space for the BIOS
alignb 4, db 0
MemDisk_Info equ $ ; Pointed to by installation check
MDI_Bytes dw 27 ; Total bytes in MDI structure
MDI_Version db VER_MINOR, VER_MAJOR ; MEMDISK version
PatchArea equ $ ; This gets filled in by the installer
DiskBuf dd 0 ; Linear address of high memory disk
DiskSize dd 0 ; Size of disk in blocks
CommandLine dw 0, 0 ; Far pointer to saved command line
OldInt13 dd 0 ; INT 13h in chain
OldInt15 dd 0 ; INT 15h in chain
OldDosMem dw 0 ; Old position of DOS mem end
BootLoaderID db 0 ; Boot loader ID from header
; ---- MDI structure ends here ---
db 0, 0, 0 ; pad
MemInt1588 dw 0 ; 1MB-65MB memory amount (1K)
Cylinders dw 0 ; Cylinder count
Heads dw 0 ; Head count
Sectors dd 0 ; Sector count (zero-extended)
Mem1MB dd 0 ; 1MB-16MB memory amount (1K)
Mem16MB dd 0 ; 16MB-4G memory amount (64K)
DriveNo db 0 ; Our drive number
DriveType db 0 ; Our drive type (floppies)
DriveCnt db 0 ; Drive count (from the BIOS)
ConfigFlags db 0 ; Bit 0 - readonly
MyStack dw 0 ; Offset of stack
StatusPtr dw 0 ; Where to save status (zeroseg ptr)
DPT times 16 db 0 ; BIOS parameter table pointer (floppies)
; End patch area
Stack dd 0 ; Saved SS:ESP on invocation
dw 0
SavedAX dw 0 ; AX saved on invocation
alignb 4, db 0 ; We *MUST* end on a dword boundary
E820Table equ $ ; The installer loads the E820 table here
TotalSize equ $ ; End pointer