Chip 1995 March/CHIP3.mdf/dos_util/partprog/pdisk.arc/PDISK.ASM

Assembly Source File | 1989-01-12 | 10.5 KB | 439 lines

    TITLE    DISK -- A Multiple Disk Driver
    SUBTTL    Header and global definitions
    PAGE    64D,132D    ; make line length 132
;    .286
    .radix    16
    OK186    EQU    (@Cpu and 02)

;DISK_NO    EQU    1    ; should get this from makefile
RQ        STRUC    ; Standard Request Header
RQ_LEN        DB    ?     ; number of bytes passed  -- first field
RQ_UCD        DB    ?     ; unit code
RQ_CCD        DB    ?     ; command code
RQ_STAT        DW    ?     ; status (return code)
RQ_RES        DB    8 DUP(?) ; reserved area
RQ        ENDS
; Status field bit equates
STAT_ERR    EQU    8000    ; There was an error.  See low byte.
STAT_BUSY    EQU    200    ; Busy.  Used in build BPB call.
STAT_DONE    EQU    100    ; Operation complete.
; low byte error return codes.
STAT_GEN_FAIL    EQU    0E    ; general failure
STAT_READ_FAULT    EQU    0BH    ; read fault
STAT_WRITE_FAULT EQU    0A    ; write fault
STAT_NOT_FOUND    EQU    8    ; sector not found
STAT_UNK_CMD    EQU    3    ; unknown command
STAT_UNK_UNIT    EQU    1    ; unknown unit
;
CSEG         SEGMENT
; start driver.  first section is data
; (though it is in the code segment)
        ASSUME    CS:CSEG,DS:NOTHING,ES:NOTHING
;  special device header
; This MUST be at ORG 0 (i.e. the first code).
START        EQU    $
NEXT_DEV    DD    -1        ; ptr to next device
ATTRIBUTE    DW    4800        ; block device, supports 3.x, ioctl
STRATEGY    DW    DEV_STRAT    ; ptr to device strategy
INTERRUPT    DW    DEV_INT        ; ptr to dev interrupt handler
DEV_COUNT    DB    0        ; number of units
DEV_NAME    DB    'SEGdsk','0'+DISK_NO    ; 7 bytes of filler
DRVTBL  LABEL   WORD
    DW    INIT
    DW    MEDIA_CHK
; according to DOS tech manual, BUILD_BPB should never get called, as long as
; MEDIA_CHK always returns "media unchanged" [sic].  However, this is not true.
; DOS's "reserved" functions 1F and 32 call it, anyway.
    DW    BUILD_BPB
    DW    EXIT        ; would be IOCTL_IN
    DW    DOTRANS
    DW    CMDERR
    DW    CMDERR
    DW    CMDERR
    DW    DOTRANS
    DW    DOTRANS
    DW    CMDERR
    DW    CMDERR
    DW    IOCTL_OUT
    DW    EXIT
    DW    EXIT
    DW    REMOVE
    DW    CMDERR
PTRSAV    DD    ?    ; for DEVSTRAT
    SUBTTL    Small Routines (interrupt, entry, exit, error, media check)
    PAGE
STRATP    PROC    FAR    ; device strategy
DEV_STRAT:
    MOV    WORD PTR CS:[PTRSAV],BX
    MOV    WORD PTR CS:[PTRSAV+2],ES
    RET
STRATP    ENDP

DEV_INT:        ; device interrupt handler
IF    OK186
    PUSHA
ELSE
    PUSH    AX
    PUSH    BX
    PUSH    CX
    PUSH    DX
    PUSH    SI
    PUSH    DI
    PUSH    BP
ENDIF
    PUSH    DS
    PUSH    ES
    ASSUME  DS:CSEG
    MOV    AX,CS        ; get normal data addressability (DS=CS)
    MOV    DS,AX
    LES    BP,[PTRSAV]
    MOV    AL,ES:[BP].RQ_CCD        ; Command code
    CMP    AL,10
    JA    CMDERR            ; Bad command
    CBW                ; = xor ah,ah
    SHL    AX,1            ; 2 times command = word table index
    MOV    SI,AX
    JMP    WORD PTR [SI].DRVTBL        ; Index into table
;
STD_BPB        STRUC        ; a bios parameter block
B_PER_S        DW    ?
SEC_PER_AU    DB    ?
RES_SECTS    DW    ?
NFATS        DB    ?
NDIRENTS    DW    ?
NSECTS        DW    ?
MEDIA_DES    DB    ?
NFATSECTS    DW    ?    ; last word of standard portion
STD_BPB        ENDS

STD_BPB_LEN    EQU    TYPE STD_BPB

BPB        STRUC
        DB    STD_BPB_LEN DUP (?)
RELSEC        DD    ?    ; add-on: see part_rec.rel_sect
PARTNO        DB    ?    ; save partition number of this drive
BPB        ENDS
;
BPB_NDX        DW    OFFSET BPB_SPACE
        DW    (OFFSET BPB_SPACE)+(TYPE BPB)
        DW    (OFFSET BPB_SPACE)+2*(TYPE BPB)
        DW    (OFFSET BPB_SPACE)+3*(TYPE BPB)
;
BBPBDATA    STRUC    ; build bpb data struct
BP_RQ        DB    (TYPE RQ) DUP(?) ; standard part
BP_MDES        DB    ?        ; media descriptor (input)
BP_TRANS    DD    DWORD PTR ?    ; transfer address
BP_RET1        DW    ?
BP_RET2        DW    ?
BBPBDATA    ENDS
;
BUILD_BPB:
    MOV    AL,ES:[BP].RQ_UCD
    CBW
    MOV    SI,AX
    SHL    SI,1
    MOV    SI,[SI].BPB_NDX
    MOV    ES:[BP].BP_RET1,SI
    MOV    ES:[BP].BP_RET2,CS
    JMP    SHORT EXIT
;
MCDATA        STRUC    ; media check data struct
MC_RQ        DB    (TYPE RQ) DUP(?) ; standard part
MC_MDES        DB    ?        ; media descriptor (input)
MC_RET        DB    ?        ; returned byte: 1 if media unchanged
MCDATA        ENDS
;
MEDIA_CHK:    ; Winchesters never change
    MOV    ES:[BP].MC_RET,1
    JMP    SHORT EXIT
REMOVE:
    MOV    AX,STAT_DONE+STAT_BUSY    ; "busy" bit = non-removable medium
    JMP    SHORT ERR1
CMDERR:
    MOV    AX,STAT_ERR+STAT_UNK_CMD+STAT_DONE    ; unknown command error
    JMP    SHORT ERR1

IOCTL_OUT:            ; only valid return is a copy of the extended BPB
    MOV    AL,ES:[BP].RQ_UCD
    CBW                ; promote AL to AX with sign extension
    SHL    AX,1            ; make device number into table offset
    MOV    SI,AX
    MOV    AX,ES
    LES    DI,DWORD PTR ES:[BP].RW_TRANS
    MOV    SI,[SI].BPB_NDX        ; now SI points to the correct BPB
    MOV    CX,TYPE BPB        ; get length of data to transfer
    REP    MOVSB
    MOV    ES,AX
    MOV    ES:[BP].RW_COUNT,TYPE BPB ; set length of data transferred
    JMP    SHORT EXIT

EXITP   PROC    FAR        ; EXIT - All routines return through this path
EXIT:   MOV    AX,STAT_DONE        ; "done" (no error)
ERR1:   MOV    ES:[BP].RQ_STAT,AX    ; mark operation complete
    POP    ES
    POP    DS
IF    OK186
    POPA
ELSE
    POP    BP
    POP    DI
    POP    SI
    POP    DX
    POP    CX
    POP    BX
    POP    AX
ENDIF
    RET        ; restore regs and return
EXITP   ENDP
    SUBTTL    Read and Write sectors
    PAGE

RWDATA        STRUC
RW_RQ        DB    (TYPE RQ) DUP(?) ; standard part
RW_MEDIA    DB    ?          ; media descriptor
RW_TRANS    DD    DWORD PTR ?      ; transfer address
RW_COUNT    DW    ?          ; # of sectors to transfer
RW_START    DW    ?          ; first block to transfer
RWDATA        ENDS
;
; local variables:
DISK_ADDR    EQU    7F+DISK_NO    ; 0x80 = disk #1, 0x81 = disk 2.
NSECS        DB    ?    ; number of sectors per track
SHPROD        DW    ?    ; NHEADS*NSECS
;
DOTRANS:
    MOV    AL,ES:[BP].RQ_UCD
    CBW                ; promote AL to AX with sign extension
    MOV    SI,AX
    INC    AX            ; (adjust for 1-based)
    CMP    AL,[DEV_COUNT]
    JLE    OK_COUNT
    MOV    AX,STAT_ERR+STAT_DONE+STAT_UNK_UNIT
    JMP    SHORT ERR1
OK_COUNT:
    SHL    SI,1            ; make device number into table offset
    MOV    SI,[SI].BPB_NDX        ; now SI points to the correct BPB
    MOV    BX,ES:[BP].RW_START    ; starting sector of request
    MOV    DI,BX            ; start_sec+sec_trans>num_secs =>error
    MOV    AX,ES:[BP].RW_COUNT
    ADD    BX,AX
    CMP    BX,[SI].NSECTS
    JBE    OK_COUNT2
    MOV    AX,STAT_ERR+STAT_DONE+STAT_NOT_FOUND
    JMP    SHORT ERR1
OK_COUNT2:
    MOV    BX,AX            ; save
    MOV    AX,WORD PTR [SI].RELSEC
    MOV    DX,WORD PTR [SI+2].RELSEC
    ADD    AX,DI        ; add starting relative sector word to request
    ADC    DX,0        ; add carry, if any, to high word
    DIV    [SHPROD] ; AX=DX:AX div CX (CX=nsects*nheads), DX=DX:AX mod CX
IF    OK186
    SHL    AH,6
ELSE
    MOV    CL,6    ; Need to put into screwy BIOS format
    SHL    AH,CL
ENDIF
    XCHG    AL,AH
    MOV    CX,AX
    MOV    AX,DX    ; now get head and sector number
    DIV    [NSECS]    ; now AH=sector number, AL=head number
    MOV    DH,AL
    OR    CL,AH
    INC    CX    ; sector number is 1 based, not 0 based (from MOD)
    MOV    DL,DISK_ADDR    ; drive code
    MOV    AX,BX        ; get original RW_COUNT back
    CMP    AX,80
    JLE    BIOS_OK1
BIOS_BAD1:
    MOV    AX,STAT_ERR+STAT_DONE+STAT_GEN_FAIL
    JMP    SHORT ERR1
BIOS_OK1:
    MOV    BX,WORD PTR ES:[BP].RW_TRANS
    PUSH    CX
    PUSH    DX
    MOV    DI,AX
IF    OK186
    SHL    AX,9
ELSE
    MOV    CL,9
    SHL    AX,CL
ENDIF
    MOV    DX,AX
    ADD    AX,BX
    JNC    BIOS_OK2
    SUB    DX,AX
    MOV    AX,DX
IF    OK186
    SHR    AX,9
ELSE
    SHR    AX,CL
ENDIF
    MOV    ES:[BP].RW_COUNT,AX
    JMP    SHORT SKIP_OK2    ; skip restore of original AX
BIOS_OK2:
    MOV    AX,DI    ; original sector count was good
SKIP_OK2:
    ; following depends on fact that BIOS read fcn is 2, write is 3
    MOV    AH,2    ; AL has number of sectors; AH gets op code
    CMP    ES:[BP].RQ_CCD,4    ; 4=read
    JE    DO_OP
    INC    AH
DO_OP:
    POP    DX
    POP    CX
    PUSH    ES
    MOV    ES,WORD PTR ES:[BP+2].RW_TRANS
    INT    13
    POP    ES
    JNC    OK_TRANS    ; Carry bit unaffected by POP
    CMP    AH,11        ; CRC error -- ignore
    JNE    BIOS_BAD1
OK_TRANS:
    JMP    EXIT
;
; the BPB table should be the LAST thing declared before initialization code,
; as we throw away whatever we don't need of it.
BPB_SPACE    BPB    4 DUP(<>) ; space for whatever BPB's we need
;
    SUBTTL    Initialization code
    PAGE
; Equates
CR        EQU    0DH
LF        EQU    0AH
BOOT_BPB    EQU    0BH    ; offset of main BPB in boot sector
BOOT_PARTTAB    EQU    1BE    ; offset of partition table in boot sector
SIGNATURE    EQU    06
; Local Structs
PART_REC    STRUC
BOOT_IND    DB    ?
S_HEAD        DB    ?
S_SEC_CYL    DW    ?
SYS_IND        DB    ?
E_HEAD        DB    ?
E_SEC_CYL    DW    ?
REL_SECT    DD    ?
NUM_SECT    DD    ?
PART_REC    ENDS
;
INITDATA    STRUC
INI_RQ        DB    (TYPE RQ) DUP(?) ; standard part
INI_NUNITS    DB    ?          ; number of units in driver
INI_END_OFF    DW    ?          ; ending address offset
INI_END_SEG    DW    ?          ; ending address segment
INI_BPB_OFF    DW    ?          ; BPB array offset
INI_BPB_SEG    DW    ?          ; BPB array segment
INI_BLOCKDEV    DB    ?
INITDATA    ENDS
; Data
PREFIX    DB    "Pdisk",'0'+DISK_NO,": $"
COPYRIGHT    DB    "(c) 1986, 1988 S. E. Garfinkle.  All Rights Reserved.$"
NO_VOLS        DB    "No volumes found.$"
NO_DRIVE    DB    "No valid drive connected.$"
DRV_INST    DB    "0 Drive(s) installed.$"
BOOT_SEC    DB    200 DUP(?)
SEC_BUF_2    DB    200 DUP(?)
; Initialization code
INIT:
    PUSH    ES    ; save ES until end of initialization
    MOV    AX,DS    ; ES=DS
    MOV    ES,AX
    MOV    DX,OFFSET COPYRIGHT
    CALL    PR_MSG
    MOV    AH,8    ; set up for "determine drive characteristics" call
    MOV    DL,DISK_ADDR
    INT    13
    CMP    DL,DISK_NO
    JAE    GOT_DISKS
    MOV    DX,OFFSET NO_DRIVE
    CALL    PR_MSG
    XOR    DX,DX
    JMP    END_INIT
GOT_DISKS:
    AND    CL,3F    ; max # of sectors.  rest of CL is cylinder high bits
    MOV    [NSECS],CL
    MOV    AL,DH    ; max # of heads.
    INC    AL    ; was zero-based.
    MUL    CL
    MOV    [SHPROD],AX    ; saves a lot of time later
    MOV    AX,201    ; need to read master boot record: AH=read, AL=1 sector
    MOV    BX,OFFSET BOOT_SEC
    MOV    CX,1    ; cylinder 1, sector 0
    MOV    DX,DISK_ADDR    ; head 0, current disk
    INT    13
    CLD
    MOV    SI,OFFSET BOOT_SEC+BOOT_PARTTAB
; DI does double duty here:  it serves as the ptr to the BPBs being filled and
; also as the pointer to the end of retainable code.
    MOV    DI,OFFSET BPB_SPACE
    MOV    BX,OFFSET SEC_BUF_2
    MOV    CX,4        ; max number of partitions
    MOV    DX,((DISK_NO - 1) SHL 0C) ; volume count=0 (DL), partno=DISK_NO << 4
LOOP1A:
    CMP    [SI].SYS_IND,SIGNATURE
    JNE    E_LOOP1A
    PUSH    CX
    PUSH    DX
    PUSH    SI
    MOV    CX,[SI].S_SEC_CYL
    MOV    DH,[SI].S_HEAD
    MOV    DL,DISK_ADDR
    MOV    AX,201
    INT    13
    MOV    SI,OFFSET SEC_BUF_2+BOOT_BPB
    MOV    CX,STD_BPB_LEN
    REP    MOVSB
    POP    SI                ; SI once again points to PARTTAB
    MOV    AX,WORD PTR [SI].REL_SECT
    STOSW
    MOV    AX,WORD PTR [SI+2].REL_SECT
    STOSW
    POP    DX
    MOV    AL,DH                ; low 4 bits are partition number
    STOSB
    POP    CX
    INC    DL
E_LOOP1A:
    INC    DH
    ADD    SI,TYPE PART_REC
    LOOP    LOOP1A
    MOV    AX,STAT_DONE
    OR    DL,DL
    JNZ    END_INIT
NONE:
    MOV    DX,OFFSET NO_VOLS
    CALL    PR_MSG
    MOV    AX,STAT_DONE+STAT_ERR+STAT_GEN_FAIL
    XOR    DL,DL
    XOR    DI,DI
END_INIT:
    POP    ES        ; restore addressability to DOS request header
    MOV    [DEV_COUNT],DL    ; "not necessary," according to manual
    MOV    ES:[BP].INI_NUNITS,DL
    MOV    ES:[BP].INI_END_OFF,DI
    MOV    ES:[BP].INI_BPB_OFF,OFFSET BPB_NDX
    MOV    ES:[BP].INI_END_SEG,CS
    MOV    ES:[BP].INI_BPB_SEG,CS
    MOV    DI,OFFSET DRV_INST
    ADD    BYTE PTR [DI],DL
    MOV    DX,DI
    CALL    PR_MSG
    JMP    ERR1

CRLF    DB    CR,LF,"$"

PR_MSG    PROC    NEAR
    MOV    AH,9
    PUSH    DX
    MOV    DX,OFFSET PREFIX
    INT    21
    POP    DX
    INT    21
    MOV    DX,OFFSET CRLF
    INT    21
    RET
PR_MSG    ENDP

CSEG    ENDS
    END