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8086asm: add support for modrm 8-bit displacement

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This commit is contained in:
Virgil Dupras 2020-06-15 06:52:47 -04:00
parent d8d2e05eb2
commit dabbd6c253
6 changed files with 17 additions and 12 deletions
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2
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@ -6,7 +6,7 @@ Mnemonics are followed by argument types. For example, MOVri,
moves 8-bit immediate to 8-bit register.
'r' = 8-bit register 'x' = 16-bit register
'i' = immediate, size depends on other operand.
'i' = 8-bit immediate 'I' = 16-bit immediate
's' = SREG register
Mnemonics that only have one signature (for example INT,) don't

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@ -1,11 +1,16 @@
: OPrm CREATE C, DOES> C@ A, SWAP 3 LSHIFT OR A, ;
0x8a OPrm MOVr[], 0x8b OPrm MOVx[],
: OPrm+ ( r m off ) CREATE C, DOES>
C@ A, ROT 3 LSHIFT ROT OR 0x40 OR A, A, ;
0x8a OPrm+ MOVr[]+, 0x8b OPrm+ MOVx[]+,
: MOVri, SWAP 0xb0 OR A, A, ;
: MOVxi, SWAP 0xb8 OR A, A,, ;
: MOVxI, SWAP 0xb8 OR A, A,, ;
: MOVsx, 0x8e A, SWAP 3 LSHIFT OR 0xc0 OR A, ;
: MOVxm, 0x8b A, SWAP 3 LSHIFT 0x6 OR A, A,, ;
: INT, 0xcd A, A, ;
: ADDAXi, 0x05 A, A,, ; : ADDALi, 0x04 A, A, ;
: ADDAXI, 0x05 A, A,, ; : ADDALi, 0x04 A, A, ;
: SUBxi, 0x83 A, SWAP 0xe8 OR A, A, ;
: JMPr, 0xff A, 7 AND 0xe0 OR A, ;
: JMPf, ( seg off ) 0xea A, SPLITB A, A, A,, ;

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@ -2,9 +2,9 @@ H@ ORG ! 0x7c00 BIN( ! ( BIOS loads boot bin at 0x7c00 )
JMPs, L1 FWRs ( start )
ORG @ 0x25 + HERE ! ( bypass BPB )
L1 FSET ( start )
CLI, CLD, AX 0x800 MOVxi, DS AX MOVsx, ES AX MOVsx,
SS AX MOVsx, SP 0xffff MOVxi, STI,
AH 2 MOVri, DX 0 MOVxi, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
BX 0 MOVxi, 0x13 INT, ( read 2nd sector of boot floppy )
CLI, CLD, AX 0x800 MOVxI, DS AX MOVsx, ES AX MOVsx,
SS AX MOVsx, SP 0xffff MOVxI, STI,
AH 2 MOVri, DX 0 MOVxI, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
BX 0 MOVxI, 0x13 INT, ( read 2nd sector of boot floppy )
0x800 0 JMPf,
ORG @ 0x1fe + HERE ! 0x55 A, 0xaa A,

6
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@ -5,12 +5,12 @@ L4 BSET PC 3 - ORG @ 4 + ! ( find )
SI INCx, ( first char ) AX AX XORxx, ( initial prev )
BEGIN, ( loop )
DI AX SUBxx, ( jump to prev wordref )
DI DECx, AL [DI] MOVr[], ( strlen )
AL [DI] -1 MOVr[]+, ( strlen )
CL AL CMPrr, IFZ, ( same len )
SI PUSHx, DI PUSHx, CX PUSHx, ( --> lvl 3 )
2 ADDALi, ( prev ) AH AH XORrr, DI AX SUBxx,
3 ADDALi, ( header ) AH AH XORrr, DI AX SUBxx,
REPZ, CMPSB,
CX POPx, DI POPx, SI POPx, ( <-- lvl 3 )
IFZ, DI INCx, AL AL XORrr, ( Z ) RETn, THEN,
IFZ, AL AL XORrr, ( Z ) RETn, THEN,
THEN,
( cont. )

2
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@ -1,5 +1,5 @@
( find cont. )
DI DECx, DI DECx, AX [DI] MOVx[], ( prev )
DI 3 SUBxi, AX [DI] MOVx[], ( prev )
AX AX ORxx,
JNZ, AGAIN, ( loop )
AX INCx, ( NZ ) RETn,

2
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@ -1,7 +1,7 @@
L3 BSET 3 A, 'F' A, 'O' A, 'O' A,
PC 3 - ORG @ 1+ ! ( main )
DI 0x08 MOVxm, ( LATEST )
SI L3 @ MOVxi,
SI L3 @ MOVxI,
CALLn, L4 @ RPCn, ( find )
IFZ, JMPs, L1 @ RPCs, ( execute ) THEN,
AH 0x0e MOVri, ( print char ) AL '!' MOVri, 0x10 INT,