TITLE DEBUASM
; Code for the UASSEMble command in the debugger
.xlist
.xcref
INCLUDE DEBEQU.ASM
INCLUDE DOSSYM.ASM
.cref
.list
CODE SEGMENT PUBLIC BYTE 'CODE'
CODE ENDS
CONST SEGMENT PUBLIC BYTE
EXTRN SYNERR:BYTE
EXTRN NSEG:WORD,SISAVE:WORD,BPSAVE:WORD,DISAVE:WORD
EXTRN BXSAVE:WORD,DSSAVE:WORD,ESSAVE:WORD,CSSAVE:WORD,IPSAVE:WORD
EXTRN SSSAVE:WORD,CXSAVE:WORD,SPSAVE:WORD,FSAVE:WORD
EXTRN DISTAB:WORD,SHFTAB:WORD,IMMTAB:WORD,GRP1TAB:WORD,GRP2TAB:WORD
EXTRN DBMN:BYTE,ESCMN:BYTE,DISPB:WORD,STACK:BYTE,REG8:BYTE
EXTRN REG16:BYTE,SREG:BYTE,SIZ8:BYTE,SEGTAB:WORD,M8087_TAB:BYTE
EXTRN FI_TAB:BYTE,SIZE_TAB:BYTE,MD9_TAB:BYTE,MD9_TAB2:BYTE
EXTRN MDB_TAB:BYTE,MDB_TAB2:BYTE,MDD_TAB:BYTE,MDD_TAB2:BYTE
EXTRN MDF_TAB:BYTE
CONST ENDS
DATA SEGMENT PUBLIC BYTE
EXTRN DISADD:BYTE,DISCNT:WORD,BYTCNT:BYTE,TEMP:BYTE,AWORD:BYTE
EXTRN MIDFLD:BYTE,MODE:BYTE,REGMEM:BYTE,OPCODE:WORD,OPBUF:BYTE
EXTRN INDEX:WORD
DATA ENDS
DG GROUP CODE,CONST,DATA
CODE SEGMENT PUBLIC BYTE 'CODE'
ASSUME CS:DG,DS:DG,ES:DG,SS:DG
PUBLIC UNASSEM
PUBLIC DISASLN,MEMIMM,JMPCALL,SIGNIMM,ALUFROMREG,WORDTOALU
PUBLIC GRP2,PREFIX,OUTVARW,GRP1,SSPRE,MOVSEGTO,DSPRE,SHIFT
PUBLIC ESPRE,IMMED,CSPRE,OUTVARB,CHK10,ACCIMM,INT3,INVARB
PUBLIC MOVSEGFROM,LOADACC,OUTFIXB,XCHGAX,REGIMMW,SHORTJMP
PUBLIC SAV8,M8087,M8087_DB,M8087_DF,M8087_D9,M8087_DD
PUBLIC SAV16,SAVHEX,INFIXW,REGIMMB,OUTFIXW,SHIFTV,LONGJMP
PUBLIC INVARW,STOREACC,INFIXB,NOOPERANDS,ALUTOREG
PUBLIC SEGOP,REGOP,GETADDR
EXTRN CRLF:NEAR,PRINTMES:NEAR,BLANK:NEAR,TAB:NEAR,OUT:NEAR
EXTRN HEX:NEAR,DEFAULT:NEAR,OUTSI:NEAR,OUTDI:NEAR
UNASSEM:
MOV BP,[CSSAVE] ; Default code segment
MOV DI,OFFSET DG:DISADD ; Default address
MOV CX,DISPB ; Default length
SHR CX,1
SHR CX,1
CALL DEFAULT
MOV WORD PTR [DISADD],DX ; Displacement of disassembly
MOV WORD PTR [DISADD+2],AX ; Segment
MOV WORD PTR [DISCNT],CX ; No. of bytes (but whole instructions)
DISLP:
CALL DISASLN ; Disassemble one line
CALL CRLF
TEST [DISCNT],-1 ; See if we've used up the range
JNZ DISLP
RET
GOTDIS: PUSH DS ; RE-GET LAST BYTE
PUSH SI
LDS SI,DWORD PTR [DISADD]
MOV AL,[SI-1]
POP SI
POP DS
RET
GETDIS:
PUSH DS
LDS SI,DWORD PTR [DISADD]
LODSB ; Get the next byte of code
POP DS
MOV WORD PTR [DISADD],SI ; Update pointer
PUSH AX
CALL HEX ; Display each code byte
MOV SI,[DISCNT]
OR SI,SI ; Check if range exhausted
JZ ENDRNG ; If so, don't wrap around
DEC SI ; Count off the bytes
MOV [DISCNT],SI
ENDRNG:
INC BYTE PTR[BYTCNT] ; Keep track of no. of bytes per line
POP AX
RET
DSPRE: INC BYTE PTR [NSEG+1]
SSPRE: INC BYTE PTR [NSEG+1]
CSPRE: INC BYTE PTR [NSEG+1]
ESPRE: INC BYTE PTR [NSEG+1]
PREFIX:
POP BX ; Dump off return address
CALL FINLN
CALL CRLF
DISASLN:
PUSH DS
LDS SI,DWORD PTR [DISADD]
CALL OUTSI ; Show disassembly address
POP DS
CALL BLANK
DISASLN1:
MOV BYTE PTR [BYTCNT],0 ; Count of code bytes per line
MOV DI,OFFSET DG:OPBUF ; Point to operand buffer
MOV AL," "
MOV CX,OPBUFLEN-1 ; Don't do last byte which has end marker
REP STOSB ; Initialize operand buffer to blanks
MOV BYTE PTR [DI]," "+80H
CALL GETDIS ; Get opcode
MOV AH,0
MOV BX,AX
AND AL,1 ; Mask to "W" bit
MOV [AWORD],AL
MOV AL,BL ; Restore opcode
SHL BX,1
SHL BX,1 ; Multiply opcode by 4
ADD BX,OFFSET DG:DISTAB
MOV DX,[BX] ; Get pointer to mnemonic from table
MOV [OPCODE],DX ; Save it until line is complete
MOV DI,OFFSET DG:OPBUF ; Initialize for opcode routines
CALL WORD PTR [BX+2] ; Dispatch to opcode routine
FINLN:
MOV SI,OFFSET DG:DISADD
MOV AH,[BYTCNT] ; See how many bytes in this instruction
ADD AH,AH ; Each uses two characters
MOV AL,14 ; Amount of space we want to use
SUB AL,AH ; See how many fill characters needed
CBW
XCHG CX,AX ; Parameter for TAB needed in CX
CALL TAB
MOV SI,[OPCODE]
OR SI,SI ; MAKE SURE THERE IS SOMETHING TO PRINT
JZ NOOPC
CALL PRINTMES ; Print opcode mnemonic
MOV AL,9
CALL OUT ; and a tab
NOOPC: MOV SI,OFFSET DG:OPBUF
JMP PRINTMES ; and the operand buffer
GETMODE:
CALL GETDIS ; Get the address mode byte
MOV AH,AL
AND AL,7 ; Mask to "r/m" field
MOV [REGMEM],AL
SHR AH,1
SHR AH,1
SHR AH,1
MOV AL,AH
AND AL,7 ; Mask to center 3-bit field
MOV [MIDFLD],AL
SHR AH,1
SHR AH,1
SHR AH,1
MOV [MODE],AH ; Leaving 2-bit "MOD" field
RET
IMMED:
MOV BX,OFFSET DG:IMMTAB
CALL GETMNE
FINIMM:
CALL TESTREG
JMP SHORT IMM
MEMIMM:
CALL GETMODE
JMP SHORT FINIMM
ACCIMM:
XOR AL,AL
IMM1:
CALL SAVREG
IMM:
MOV AL,","
STOSB
TEST BYTE PTR [AWORD],-1
JNZ SAV16
SAV8:
CALL GETDIS
JMP SHORT SAVHEX
LONGJMP:
PUSH DI
MOV DI,OFFSET DG:TEMP
CALL SAV16
POP DI
CALL SAV16
MOV AL,":"
STOSB
MOV SI,OFFSET DG:TEMP
MOV CX,4
MOVDIG:
LODSB
STOSB
LOOP MOVDIG
RET
SAV16:
CALL GETDIS ; Get low byte
MOV DL,AL
CALL GETDIS ; Get high byte
MOV DH,AL
CALL SAVHEX ; Convert and store high byte
MOV AL,DL
SAVHEX:
MOV AH,AL
SHR AL,1
SHR AL,1
SHR AL,1
SHR AL,1
CALL SAVDIG
MOV AL,AH
SAVDIG:
AND AL,0FH
ADD AL,90H
DAA
ADC AL,40H
DAA
STOSB
RET
CHK10:
CALL GETDIS
CMP AL,10
JNZ SAVHEX
RET
SIGNIMM:
MOV BX,OFFSET DG:IMMTAB
CALL GETMNE
CALL TESTREG
MOV AL,","
STOSB
SAVD8:
CALL GETDIS ; Get signed 8-bit number
CBW
MOV DX,AX ; Save true 16-bit value in DX
MOV AH,AL
MOV AL,"+"
OR AH,AH
; JZ nosign
JNS POSITIV ; OK if positive
MOV AL,"-"
NEG AH ; Get magnitude if negative
POSITIV:
STOSB
; nosign:
MOV AL,AH
JMP SHORT SAVHEX
ALUFROMREG:
CALL GETADDR
MOV AL,","
STOSB
REGFLD:
MOV AL,[MIDFLD]
SAVREG:
MOV SI,OFFSET DG:REG8
CMP BYTE PTR [AWORD],1
JNE FNDREG
SAVREG16:
MOV SI,OFFSET DG:REG16
FNDREG:
CBW
ADD SI,AX
ADD SI,AX
MOVSW
RET
SEGOP:
SHR AL,1
SHR AL,1
SHR AL,1
SAVSEG:
AND AL,3
MOV SI,OFFSET DG:SREG
JMP SHORT FNDREG
REGOP:
AND AL,7
JMP SHORT SAVREG16
MOVSEGTO:
MOV BYTE PTR [AWORD],1
CALL GETADDR
MOV AL,","
STOSB
MOV AL,[MIDFLD]
JMP SHORT SAVSEG
MOVSEGFROM:
CALL GETMODE
CALL SAVSEG
MOV BYTE PTR [AWORD],1
JMP SHORT MEMOP2
GETADDR:
CALL GETMODE
JMP SHORT ADDRMOD
WORDTOALU:
MOV BYTE PTR [AWORD],1
ALUTOREG:
CALL GETMODE
CALL REGFLD
MEMOP2:
MOV AL,","
STOSB
ADDRMOD:
CMP BYTE PTR [MODE],3
MOV AL,[REGMEM]
JE SAVREG
XOR BX,BX
MOV BYTE PTR [NSEG],3
MOV BYTE PTR [DI],"["
INC DI
CMP AL,6
JNE NODRCT
CMP BYTE PTR [MODE],0
JE DIRECT ; Mode=0 and R/M=6 means direct addr.
NODRCT:
MOV DL,AL
CMP AL,1
JBE USEBX
CMP AL,7
JE USEBX
CMP AL,3
JBE USEBP
CMP AL,6
JNE CHKPLS
USEBP:
MOV BX,[BPSAVE]
MOV BYTE PTR [NSEG],2 ; Change default to Stack Segment
MOV AX,BPREG
SAVBASE:
STOSW
CHKPLS:
CMP DL,4
JAE NOPLUS
MOV AL,"+"
STOSB
NOPLUS:
CMP DL,6
JAE DOMODE ; No index register
AND DL,1 ; Even for SI, odd for DI
JZ USESI
ADD BX,[DISAVE]
MOV AX,DIREG
SAVINDX:
STOSW
DOMODE:
MOV AL,[MODE]
OR AL,AL
JZ CLOSADD ; If no displacement, then done
CMP AL,2
JZ ADDDIR
CALL SAVD8 ; Signed 8-bit displacement
ADDCLOS:
ADD BX,DX
CLOSADD:
MOV AL,"]"
STOSB
MOV [INDEX],BX
NOOPERANDS:
RET
ADDDIR:
MOV AL,"+"
STOSB
DIRECT:
CALL SAV16
JMP SHORT ADDCLOS
USEBX:
MOV BX,[BXSAVE]
MOV AX,BXREG
JMP SHORT SAVBASE
USESI:
ADD BX,[SISAVE]
MOV AX,SIREG
JMP SHORT SAVINDX
SHORTJMP:
CALL GETDIS
CBW
ADD AX,WORD PTR [DISADD]
XCHG DX,AX
SAVJMP:
MOV AL,DH
CALL SAVHEX
MOV AL,DL
JMP SAVHEX
JMPCALL:
CALL GETDIS
MOV DL,AL
CALL GETDIS
MOV DH,AL
ADD DX,WORD PTR [DISADD]
JMP SHORT SAVJMP
XCHGAX:
AND AL,7
CALL SAVREG16
MOV AL,","
STOSB
XOR AL,AL
JMP SAVREG16
LOADACC:
XOR AL,AL
CALL SAVREG
MOV AL,","
STOSB
MEMDIR:
MOV AL,"["
STOSB
XOR BX,BX
MOV BYTE PTR [NSEG],3
JMP DIRECT
STOREACC:
CALL MEMDIR
MOV AL,","
STOSB
XOR AL,AL
JMP SAVREG
REGIMMB:
MOV BYTE PTR [AWORD],0
JMP SHORT REGIMM
REGIMMW:
MOV BYTE PTR [AWORD],1
REGIMM:
AND AL,7
JMP IMM1
INT3:
MOV BYTE PTR [DI],"3"
RET
;
; 8087 instructions whose first byte is 0dfh
;
M8087_DF:
CALL GET64F
JZ ISDD3
MOV SI,OFFSET DG:MDF_TAB
JMP NODB3
;
; 8087 instructions whose first byte is 0ddh
;
M8087_DD:
CALL GET64F
JZ ISDD3
MOV SI,OFFSET DG:MDD_TAB
JMP NOD93
ISDD3:
MOV AL,DL
TEST AL,100B
JZ ISSTI
JMP ESC0
ISSTI: AND AL,11B
MOV SI,OFFSET DG:MDD_TAB2
MOV CL,AL
CALL MOVBYT
JMP PUTRST
;
; 8087 instructions whose first byte is 0dbh
;
M8087_DB:
CALL GET64F
JZ ISDB3
MOV SI,OFFSET DG:MDB_TAB
NODB3: CALL PUTOP
CALL PUTSIZE
JMP ADDRMOD
ISDB3:
MOV AL,DL
TEST AL,100B
JNZ ISDBIG
ESC0V: JMP ESC0
ISDBIG: CALL GOTDIS
AND AL,11111B
CMP AL,4
JAE ESC0V
MOV SI,OFFSET DG:MDB_TAB2
JMP DOBIG
;
; 8087 instructions whose first byte is 0d9h
;
M8087_D9:
CALL GET64F
JZ ISD93
MOV SI,OFFSET DG:MD9_TAB
NOD93: CALL PUTOP
AND AL,111B
CMP AL,3
JA NOSHO
MOV AL,DL
CALL PUTSIZE
NOSHO: JMP ADDRMOD
ISD93: MOV AL,DL
TEST AL,100B
JNZ ISD9BIG
AND AL,111B
OR AL,AL
JNZ NOTFLD
MOV AX,"DL"
STOSW
JMP SHORT PUTRST
NOTFLD: CMP AL,1
JNZ NOTFXCH
MOV AX,"CX"
STOSW
MOV AL,"H"
JMP SHORT PUTRST1
NOTFXCH:CMP AL,3
JNZ NOTFSTP
MOV AX,"TS"
STOSW
MOV AL,"P"
PUTRST1:STOSB
PUTRST: MOV AL,9
STOSB
JMP PUTST0
NOTFSTP:CALL GOTDIS
CMP AL,11010000B ; CHECK FOR FNOP
JZ GOTFNOP
JMP ESC0
GOTFNOP:MOV AX,"ON"
STOSW
MOV AL,"P"
STOSB
RET
ISD9BIG:
CALL GOTDIS ; GET THE MODE BYTE
MOV SI,OFFSET DG:MD9_TAB2
DOBIG: AND AL,11111B
MOV CL,AL
JMP MOVBYT
;
; entry point for the remaining 8087 instructions
;
M8087:
CALL GET64
CALL PUTFI ; PUT FIRST PART OF OPCODE
MOV AL,DL
CMP BYTE PTR [MODE],11B ; CHECK FOR REGISTER MODE
JZ MODEIS3
CALL PUTMN ; PUT MIDDLE PART OF OPCODE
NO3: MOV AL,9 ; OUTPUT A TAB
STOSB
MOV AL,DL
CALL PUTSIZE ; OUTPUT THE OPERAND SIZE
JMP ADDRMOD
MODEIS3:
TEST AL,100000B ; D BIT SET?
JZ MPUT ; NOPE...
TEST AL,000100B ; FDIV OR FSUB?
JZ MPUT ; NOPE...
XOR AL,1 ; REVERSE SENSE OF R
MOV DL,AL ; SAVE CHANGE
MPUT: CALL PUTMN ; PUT MIDDLE PART OF OPCODE
MOV AL,DL
TEST AL,010000B
JZ NOPSH
MOV AL,"P"
STOSB
NOPSH: MOV AL,9
STOSB
MOV AL,DL
AND AL,00000111B
CMP AL,2 ; FCOM
JZ PUTST0
CMP AL,3 ; FCOMP
JZ PUTST0
MOV AL,DL
TEST AL,100000B
JZ PUTSTST0
;
; output 8087 registers in the form st(n),st
;
PUTST0ST:
CALL PUTST0
MOV AL,','
ISCOMP: STOSB
PUTST: MOV AX,"TS"
STOSW
RET
;
; output 8087 registers in the form st,st(n)
;
PUTSTST0:
CALL PUTST
MOV AL,','
STOSB
PUTST0: CALL PUTST
MOV AL,"("
STOSB
MOV AL,[REGMEM]
ADD AL,"0"
STOSB
MOV AL,")"
STOSB
RET
;
; output an 8087 mnemonic
;
PUTMN: MOV SI,OFFSET DG:M8087_TAB
MOV CL,AL
AND CL,00000111B
JMP SHORT MOVBYT
;
; output either 'FI' or 'F' for first byte of opcode
;
PUTFI: MOV SI,OFFSET DG:FI_TAB
JMP SHORT PUTFI2
;
; output size (dword, tbyte, etc.)
;
PUTSIZE:MOV SI,OFFSET DG:SIZE_TAB
PUTFI2: CMP BYTE PTR [MODE],11B ; check if 8087 register
JNZ PUTFI3
AND AL,111000B ; LOOK FOR INVALID FORM OF 0DAH OPERANDS
CMP AL,010000B
JZ ESC0PJ
MOV AL,DL
CMP AL,110011B ; FCOMPP
JNZ GOFI
CMP BYTE PTR [REGMEM],1
JZ GOFI
ESC0PJ: JMP ESC0P
GOFI: XOR CL,CL
JMP SHORT MOVBYT
;
; Look for qword
;
PUTFI3: CMP AL,111101B
JZ GOTQU
CMP AL,111111B
JNZ NOTQU
GOTQU: MOV CL,2
JMP SHORT MOVBYT
;
; look for tbyte
;
NOTQU: CMP AL,011101B
JZ GOTTB
CMP AL,111100B
JZ GOTTB
CMP AL,111110B
JZ GOTTB
CMP AL,011111B
JNZ NOTTB
GOTTB: MOV CL,5
JMP SHORT MOVBYT
NOTTB: MOV CL,4
SHR AL,CL
MOV CL,AL
;
; SI POINTS TO A TABLE OF TEXT SEPARATED BY "$"
; CL = WHICH ELEMENT IN THE TABLE YOU WISH TO COPY TO [DI]
;
MOVBYT: PUSH AX
INC CL
MOVBYT1:DEC CL
JZ MOVBYT3
MOVBYT2:LODSB
CMP AL,'$'
JZ MOVBYT1
JMP MOVBYT2
MOVBYT3:LODSB
CMP AL,'$'
JZ MOVBYT5
CMP AL,'@' ; THIS MEANS RESVERED OP-CODE
JNZ MOVBYT4
POP AX
JMP SHORT ESC0P ; GO DO AN ESCAPE COMMAND
MOVBYT4:STOSB
JMP MOVBYT3
MOVBYT5:POP AX
RET
PUTOP: AND AL,111B
MOV CL,AL
CALL MOVBYT
MOV AL,9
STOSB
MOV AL,DL
RET
GET64F: CALL GET64
MOV AL,"F"
STOSB
CMP BYTE PTR [MODE],3
MOV AL,DL
RET
GET64:
AND AL,7
MOV DL,AL
CALL GETMODE
SHL DL,1
SHL DL,1
SHL DL,1
OR AL,DL
MOV DL,AL ; SAVE RESULT
RET
ESC0P: POP DI ; CLEAN UP STACK
ESC0: MOV WORD PTR [OPCODE],OFFSET DG:ESCMN
MOV AL,DL
MOV DI,OFFSET DG:OPBUF
JMP SHORT ESC1
ESC: CALL GET64
ESC1: CALL SAVHEX
CMP BYTE PTR [MODE],3
JZ SHRTESC
MOV BYTE PTR [AWORD],1
JMP MEMOP2
SHRTESC:
MOV AL,","
STOSB
MOV AL,[REGMEM]
AND AL,7
JMP SAVREG
INVARW:
CALL PUTAX
JMP SHORT INVAR
INVARB:
CALL PUTAL
INVAR: MOV AL,','
STOSB
JMP PUTDX
INFIXW:
CALL PUTAX
JMP SHORT INFIX
INFIXB:
CALL PUTAL
INFIX: MOV AL,','
STOSB
JMP SAV8
STOSW
RET
OUTVARB:
MOV BX,"LA"
JMP SHORT OUTVAR
OUTVARW:
MOV BX,"XA"
OUTVAR: CALL PUTDX
OUTFV: MOV AL,','
STOSB
MOV AX,BX
STOSW
RET
OUTFIXB:
MOV BX,"LA"
JMP SHORT OUTFIX
OUTFIXW:
MOV BX,"XA"
OUTFIX: CALL SAV8
JMP OUTFV
PUTAL: MOV AX,"A"+4C00H ; "AL"
JMP SHORT PUTX
PUTAX: MOV AX,"A"+5800H ; "AX"
JMP SHORT PUTX
PUTDX: MOV AX,"D"+5800H ; "DX"
PUTX: STOSW
RET
SHFT:
MOV BX,OFFSET DG:SHFTAB
CALL GETMNE
TESTREG:
CMP BYTE PTR [MODE],3
JZ NOFLG
MOV SI,OFFSET DG:SIZE_TAB
MOV CL,3
TEST BYTE PTR [AWORD],-1
JNZ TEST_1
INC CL
TEST_1: CALL MOVBYT
NOFLG:
JMP ADDRMOD
SHIFTV:
CALL SHFT
MOV AL,","
STOSB
MOV WORD PTR [DI],"C"+4C00H ; "CL"
RET
SHIFT:
CALL SHFT
MOV AX,"1,"
STOSW
RET
GETMNE:
CALL GETMODE
MOV DL,AL
CBW
SHL AX,1
ADD BX,AX
MOV AX,[BX]
MOV [OPCODE],AX
MOV AL,DL
RET
GRP1:
MOV BX,OFFSET DG:GRP1TAB
CALL GETMNE
OR AL,AL
JZ FINIMMJ
JMP TESTREG
FINIMMJ:
JMP FINIMM
GRP2:
MOV BX,OFFSET DG:GRP2TAB
CALL GETMNE
CMP AL,2
JB TESTREG
CMP AL,6
JAE INDIRECT
TEST AL,1
JZ INDIRECT
MOV AX,"AF" ; "FAR"
STOSW
MOV AX," R"
STOSW
INDIRECT:
JMP ADDRMOD
CODE ENDS
END UNASSEM
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