x86 machine code 初探 (3) - opcode extension

FF 15 D4 81 DF 00 這是 http://www.mouseos.com/x64/preface.html 的例子, 我一直看不懂, 不過我現在搞清楚了。

call dword ptr [00DF81D4h]

descent@w-linux:x86_machine_code$ rasm2 "call dword ptr [00DF81D4h]"
ff15d481df00
descent@w-linux:x86_machine_code$ man rasm2
descent@w-linux:x86_machine_code$ rasm2 -s att "call (0x00DF81D4)"
e8cf81df00
descent@w-linux:x86_machine_code$ rasm2 -d "FF 15 D4 81 DF 00"
call dword [0xdf81d4]

att syntax:
ff 15 d4 81 df 00        call   *0xdf81d4


ModRM: 15
mod: 00
reg: 010
r/m: 101

mod: 00
r/m: 101
-> disp32

ff 查 opcode map 得到 group5 (Grp5), 再根據 reg: 010 查 opcode extensions group 表得到 call (Ev)

E	A modR/M byte follows the opcode and specifies the operand. The operand is either a general register or a memory address. If it is a memory address, the address is computed from a segment register and any of the following values: a base register, an index register, a scaling factor, a displacement.

v	Word or double word, depending on operand size attribute.

One-Byte Opcode Map

0         1         2         3         4         5         6        7        8         9         A         B         C         D         E        F
 +-----------------------------------------------------------+--------+--------+-----------------------------------------------------------+--------+--------+
 |                              ADD                          |  PUSH  |   POP  |                             OR                            |  PUSH  | 2-byte |
0|---------+---------+---------+---------+---------+---------+        |        +---------+---------+---------+---------+---------+---------+        |        |
 |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |   ES   |   ES   |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |   CS   | escape |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                              ADC                          |  PUSH  |   POP  |                            SBB                            |  PUSH  |  POP   |
1|---------+---------+---------+---------+---------+---------+        |        +---------+---------+---------+---------+---------+---------+        |        |
 |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |   SS   |   SS   |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |   DS   |   DS   |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                              AND                          |  SEG   |        |                            SUB                            |  SEG   |        |
2|---------+---------+---------+---------+---------+---------+        |   DAA  +---------+---------+---------+---------+---------+---------+        |  DAS   |
 |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |  =ES   |        |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |  =CS   |        |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                              XOR                          |  SEG   |        |                            CMP                            |  SEG   |        |
3|---------+---------+---------+---------+---------+---------+        |   AAA  +---------+---------+---------+---------+---------+---------+        |  AAS   |
 |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |  =SS   |        |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  AL,Ib  | eAX,Iv  |  =CS   |        |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                               INC general register                          |                              DEC general register                           |
4|---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |   eAX   |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |  eSI   |  eDI   |   eAX   |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |   eSI  |  eDI   |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                               PUSH general register                         |                          POP into general register                          |
5|---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |   eAX   |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |  eSI   |  eDI   |   eAX   |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |  eSI   |  eDI   |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |         |         |  BOUND  |  ARPL   |   SEG   |   SEG   | Operand| Address|  PUSH   |  IMUL   |  PUSH   |  IMUL   |  INSB   | INSW/D  | OUTSB  |OUTSW/D |
6|  PUSHA  |  POPA   |         |         |         |         |        |        |         |         |         |         |         |         |        |        |
 |         |         |  Gv,Ma  |  Ew,Rw  |   =FS   |   =GS   |  Size  |  Size  |   Ib    | GvEvIv  |   Ib    | GvEvIv  |  Yb,DX  |  Yb,DX  | Dx,Xb  | DX,Xv  |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                    Short displacement jump of condition (Jb)                |                   Short-displacement jump on condition(Jb)                  |
7|---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |   JO    |   JNO   |   JB    |   JNB   |   JZ    |  JNZ    |   JBE  |  JNBE  |   JS    |   JNS   |   JP    |   JNP   |   JL    |  JNL    |  JLE   |  JNLE  |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |  Immediate Grpl   |         |  Grpl   |       TEST        |      XCHG       |                 MOV                   |   MOV   |   LEA   |  MOV   |  POP   |
8|---------+---------+         |         +---------+---------+--------+--------+---------+---------+---------+---------+         |         |        |        |
 |  Eb,Ib  |  Ev,Iv  |         |  Ev,Iv  |  Eb,Gb  |  Ev,Gv  |  Eb,Gb |  Ev,Gv |  Eb,Gb  |  Ev,Gv  |  Gb,Eb  |  Gv,Ev  |  Ew,Sw  |  Gv,M   |  Sw,Ew |   Ev   |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |         |              XCHG word or double-word register with eAX           |         |         |  CALL   |         |  PUSHF  |  POPF   |        |        |
9|   NOP   +---------+---------+---------+---------+---------+--------+--------+   CBW   |   CWD   |         |  WAIT   |         |         |  SAHF  |  LAHF  |
 |         |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |  eSI   |  eDI   |         |         |   Ap    |         |   Fv    |   Fv    |        |        |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                  MOV                  |  MOVSB  | MOVSW/D | CMPSB  |CMPSW/D |       TEST        |  STOSB  | STOSW/D |  LODSB  | LODSW/D | SCASB  |SCASW/D |
A|---------+---------+---------+---------+         |         |        |        +---------+---------+         |         |         |         |        |        |
 |  AL,Ob  |  eAX,Ov |  Ob,AL  |  Ov,eAX |  Xb,Yb  |  Xv,Yv  |  Xb,Yb |  Xv,Yv |  AL,Ib  | eAX,Iv  |  Yb,AL  |  Yv,eAX |  AL,Xb  | eAX,Xv  |  AL,Xb |eAX,Xv  |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |                       MOV immediate byte into byte register                 |        MOV immediate word or double into word or double register            |
B|---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |    AL   |   CL    |   DL    |   BL    |   AH    |   CH    |   DH   |   BH   |   eAX   |   eCX   |   eDX   |   eBX   |   eSP   |   eBP   |   eSI  |  eDI   |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |    Shift Grp2     |      RET near     |   LES   |   LDS   |       MOV       |  ENTER  |         |      RET far      |  INT    |  INT    |        |        |
C|---------+---------+---------+---------+         |         +--------+--------+         |  LEAVE  +---------+---------+         |         |  INTO  |  IRET  |
 |  Eb,Ib  |  Ev,Iv  |    Iw   |         |  Gv,Mp  |  Gv,Mp  |  Eb,Ib |  Ev,Iv |  Iw,Ib  |         |   Iw    |         |   3     |  Ib     |        |        |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |               Shift Grp2              |         |         |        |        |                                                                             |
D|---------+---------+---------+---------+   AAM   |   AAD   |        |  XLAT  |                  ESC(Escape to coprocessor instruction set)                 |
 |   Eb,1  |  Ev,1   |  Eb,CL  |  Ev,CL  |         |         |        |        |                                                                             |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+-----------------------------+-------------------+-----------------+
 | LOOPNE  |  LOOPE  |   LOOP  |  JCXZ   |        IN         |       OUT       |   CALL  |             JNP             |        IN         |       OUT       |
E|         |         |         |         +---------+---------+--------+--------+         +---------+---------+---------+---------+---------+--------+--------+
 |   Jb    |   Jb    |    Jb   |   Jb    |  AL,Ib  | eAX,Ib  |  Ib,AL | Ib,eAX |    Av   |   Jv    |   Ap    |   Jb    |  AL,DX  | eAX,DX  | DX,AL  | DX,eAX |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+
 |         |         |         |   REP   |         |         |     Unary Grp3  |         |         |         |         |         |         |INC/DEC |Indirct |
F|  LOCK   |         |  REPNE  |         |   HLT   |   CMC   +--------+--------+   CLC   |   STC   |   CLI   |   STI   |   CLD   |   STD   |        |        |
 |         |         |         |  REPE   |         |         |   Eb   |   Ev   |         |         |         |         |         |         |  Grp4  |  Grp5  |
 +---------+---------+---------+---------+---------+---------+--------+--------+---------+---------+---------+---------+---------+---------+--------+--------+

Opcodes determined by bits 5,4,3 of modR/M byte (opcode extensions group)

G                       +-------+-------+-------+
     r                       |  mod  |  nnn  |  R/M  |
     o                       +-------+-------+-------+
     u
     p   000     001     010     011     100     101     110     111
      +-------+-------+-------+-------+-------+-------+-------+-------+
     1|  ADD  |  OR   |  ADC  |  SBB  |  AND  |  SUB  |  XOR  |  CMP  |
      |       |       |       |       |       |       |       |       |
      +-------+-------+-------+-------+-------+-------+-------+-------+
     2|  ROL  |  ROR  |  RCL  |  RCR  |  SHL  |  SHR  |       |  SAR  |
      |       |       |       |       |       |       |       |       |
      +-------+-------+-------+-------+-------+-------+-------+-------+
     3| TEST  |       |  NOT  |  NEG  |  MUL  | IMUL  |  DIV  | IDIV  |
      | Ib/Iv |       |       |       |AL/eAX |AL/eAX |AL/eAX |AL/eAX |
      +-------+-------+-------+-------+-------+-------+-------+-------+
     4|  INC  |  DEC  |       |       |       |       |       |       |
      |  Eb   |  Eb   |       |       |       |       |       |       |
      +-------+-------+-------+-------+-------+-------+-------+-------+
     5|  INC  |  DEC  | CALL  | CALL  |  JMP  |  JMP  | PUSH  |       |
      |  Ev   |  Ev   |  Ev   |  eP   |  Ev   |  Ep   |  Ev   |       |
      +-------+-------+-------+-------+-------+-------+-------+-------+