about summary refs log tree commit diff stats
path: root/020byte_addressing.cc
blob: 93e269e163dea65cc3ff0c7c83c4feecda17408b (plain) (blame)
1
2
3
4
5
6
7
8
9
generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-07-12 06:17:43 +0000
 


n228' href='#n228'>228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
//: SubX mostly deals with instructions operating on 32-bit operands, but we
//: still need to deal with raw bytes for strings and so on.

//: Unfortunately the register encodings when dealing with bytes are a mess.
//: We need a special case for them.
:(code)
string rname_8bit(uint8_t r) {
  switch (r) {
  case 0: return "AL";  // lowest byte of EAX
  case 1: return "CL";  // lowest byte of ECX
  case 2: return "DL";  // lowest byte of EDX
  case 3: return "BL";  // lowest byte of EBX
  case 4: return "AH";  // second lowest byte of EAX
  case 5: return "CH";  // second lowest byte of ECX
  case 6: return "DH";  // second lowest byte of EDX
  case 7: return "BH";  // second lowest byte of EBX
  default: raise << "invalid 8-bit register " << r << '\n' << end();  return "";
  }
}

uint8_t* effective_byte_address(uint8_t modrm) {
  uint8_t mod = (modrm>>6);
  uint8_t rm = modrm & 0x7;
  if (mod == 3) {
    // select an 8-bit register
    trace(Callstack_depth+1, "run") << "r/m8 is " << rname_8bit(rm) << end();
    return reg_8bit(rm);
  }
  // the rest is as usual
  return mem_addr_u8(effective_address_number(modrm));
}

uint8_t* reg_8bit(uint8_t rm) {
  uint8_t* result = reinterpret_cast<uint8_t*>(&Reg[rm & 0x3].i);  // _L register
  if (rm & 0x4)
    ++result;  // _H register;  assumes host is little-endian
  return result;
}

:(before "End Initialize Op Names")
put_new(Name, "88", "copy r8 to r8/m8-at-r32");

:(code)
void test_copy_r8_to_mem_at_rm32() {
  Reg[EBX].i = 0x224488ab;
  Reg[EAX].i = 0x2000;
  run(
      "== code 0x1\n"
      // op     ModR/M  SIB   displacement  immediate
      "  88     18                                      \n"  // copy BL to the byte at *EAX
      // ModR/M in binary: 00 (indirect mode) 011 (src BL) 000 (dest EAX)
      "== data 0x2000\n"
      "f0 cc bb aa\n"
  );
  CHECK_TRACE_CONTENTS(
      "run: copy BL to r8/m8-at-r32\n"
      "run: effective address is 0x00002000 (EAX)\n"
      "run: storing 0xab\n"
  );
  CHECK_EQ(0xaabbccab, read_mem_u32(0x2000));
}

:(before "End Single-Byte Opcodes")
case 0x88: {  // copy r8 to r/m8
  const uint8_t modrm = next();
  const uint8_t rsrc = (modrm>>3)&0x7;
  trace(Callstack_depth+1, "run") << "copy " << rname_8bit(rsrc) << " to r8/m8-at-r32" << end();
  // use unsigned to zero-extend 8-bit value to 32 bits
  uint8_t* dest = effective_byte_address(modrm);
  const uint8_t* src = reg_8bit(rsrc);
  *dest = *src;  // Read/write multiple elements of vector<uint8_t> at once. Assumes sizeof(int) == 4 on the host as well.
  trace(Callstack_depth+1, "run") << "storing 0x" << HEXBYTE << NUM(*dest) << end();
  break;
}

//:

:(before "End Initialize Op Names")
put_new(Name, "8a", "copy r8/m8-at-r32 to r8");

:(code)
void test_copy_mem_at_rm32_to_r8() {
  Reg[EBX].i = 0xaabbcc0f;  // one nibble each of lowest byte set to all 0s and all 1s, to maximize value of this test
  Reg[EAX].i = 0x2000;
  run(
      "== code 0x1\n"
      // op     ModR/M  SIB   displacement  immediate
      "  8a     18                                      \n"  // copy just the byte at *EAX to BL
      // ModR/M in binary: 00 (indirect mode) 011 (dest EBX) 000 (src EAX)
      "== data 0x2000\n"
      "ab ff ff ff\n"  // 0xab with more data in following bytes
  );
  CHECK_TRACE_CONTENTS(
      "run: copy r8/m8-at-r32 to BL\n"
      "run: effective address is 0x00002000 (EAX)\n"
      "run: storing 0xab\n"
      // remaining bytes of EBX are *not* cleared
      "run: EBX now contains 0xaabbccab\n"
  );
}

:(before "End Single-Byte Opcodes")
case 0x8a: {  // copy r/m8 to r8
  const uint8_t modrm = next();
  const uint8_t rdest = (modrm>>3)&0x7;
  trace(Callstack_depth+1, "run") << "copy r8/m8-at-r32 to " << rname_8bit(rdest) << end();
  // use unsigned to zero-extend 8-bit value to 32 bits
  const uint8_t* src = effective_byte_address(modrm);
  uint8_t* dest = reg_8bit(rdest);
  trace(Callstack_depth+1, "run") << "storing 0x" << HEXBYTE << NUM(*src) << end();
  *dest = *src;  // Read/write multiple elements of vector<uint8_t> at once. Assumes sizeof(int) == 4 on the host as well.
  const uint8_t rdest_32bit = rdest & 0x3;
  trace(Callstack_depth+1, "run") << rname(rdest_32bit) << " now contains 0x" << HEXWORD << Reg[rdest_32bit].u << end();
  break;
}

:(code)
void test_cannot_copy_byte_to_ESP_EBP_ESI_EDI() {
  Reg[ESI].u = 0xaabbccdd;
  Reg[EBX].u = 0x11223344;
  run(
      "== code 0x1\n"
      // op     ModR/M  SIB   displacement  immediate
      "  8a     f3                                      \n"  // copy just the byte at *EBX to 8-bit register '6'
      // ModR/M in binary: 11 (direct mode) 110 (dest 8-bit 'register 6') 011 (src EBX)
  );
  CHECK_TRACE_CONTENTS(
      // ensure 8-bit register '6' is DH, not ESI
      "run: copy r8/m8-at-r32 to DH\n"
      "run: storing 0x44\n"
  );
  // ensure ESI is unchanged
  CHECK_EQ(Reg[ESI].u, 0xaabbccdd);
}

//:

:(before "End Initialize Op Names")
put_new(Name, "c6", "copy imm8 to r8/m8-at-r32 (mov)");

:(code)
void test_copy_imm8_to_mem_at_rm32() {
  Reg[EAX].i = 0x2000;
  run(
      "== code 0x1\n"
      // op     ModR/M  SIB   displacement  immediate
      "  c6     00                          dd          \n"  // copy to the byte at *EAX
      // ModR/M in binary: 00 (indirect mode) 000 (unused) 000 (dest EAX)
      "== data 0x2000\n"
      "f0 cc bb aa\n"
  );
  CHECK_TRACE_CONTENTS(
      "run: copy imm8 to r8/m8-at-r32\n"
      "run: effective address is 0x00002000 (EAX)\n"
      "run: storing 0xdd\n"
  );
  CHECK_EQ(0xaabbccdd, read_mem_u32(0x2000));
}

:(before "End Single-Byte Opcodes")
case 0xc6: {  // copy imm8 to r/m8
  const uint8_t modrm = next();
  const uint8_t src = next();
  trace(Callstack_depth+1, "run") << "copy imm8 to r8/m8-at-r32" << end();
  trace(Callstack_depth+1, "run") << "imm8 is 0x" << HEXBYTE << NUM(src) << end();
  const uint8_t subop = (modrm>>3)&0x7;  // middle 3 'reg opcode' bits
  if (subop != 0) {
    cerr << "unrecognized subop for opcode c6: " << NUM(subop) << " (only 0/copy currently implemented)\n";
    exit(1);
  }
  // use unsigned to zero-extend 8-bit value to 32 bits
  uint8_t* dest = effective_byte_address(modrm);
  *dest = src;  // Write multiple elements of vector<uint8_t> at once. Assumes sizeof(int) == 4 on the host as well.
  trace(Callstack_depth+1, "run") << "storing 0x" << HEXBYTE << NUM(*dest) << end();
  break;
}

//:: set flags (setcc)

:(before "End Initialize Op Names")
put_new(Name_0f, "94", "set r8/m8-at-rm32 to 1 if equal, if ZF is set, 0 otherwise (setcc/setz/sete)");
put_new(Name_0f, "95", "set r8/m8-at-rm32 to 1 if not equal, if ZF is not set, 0 otherwise (setcc/setnz/setne)");
put_new(Name_0f, "9f", "set r8/m8-at-rm32 to 1 if greater, if ZF is unset and SF == OF, 0 otherwise (setcc/setg/setnle)");
put_new(Name_0f, "97", "set r8/m8-at-rm32 to 1 if greater (addr, float), if ZF is unset and CF is unset, 0 otherwise (setcc/seta/setnbe)");
put_new(Name_0f, "9d", "set r8/m8-at-rm32 to 1 if greater or equal, if SF == OF, 0 otherwise (setcc/setge/setnl)");
put_new(Name_0f, "93", "set r8/m8-at-rm32 to 1 if greater or equal (addr, float), if CF is unset, 0 otherwise (setcc/setae/setnb)");
put_new(Name_0f, "9c", "set r8/m8-at-rm32 to 1 if lesser, if SF != OF, 0 otherwise (setcc/setl/setnge)");
put_new(Name_0f, "92", "set r8/m8-at-rm32 to 1 if lesser (addr, float), if CF is set, 0 otherwise (setcc/setb/setnae)");
put_new(Name_0f, "9e", "set r8/m8-at-rm32 to 1 if lesser or equal, if ZF is set or SF != OF, 0 otherwise (setcc/setle/setng)");
put_new(Name_0f, "96", "set r8/m8-at-rm32 to 1 if lesser or equal (addr, float), if ZF is set or CF is set, 0 otherwise (setcc/setbe/setna)");

:(before "End Two-Byte Opcodes Starting With 0f")
case 0x94: {  // set r8/m8-at-rm32 if ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = ZF;
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x95: {  // set r8/m8-at-rm32 if !ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = !ZF;
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x9f: {  // set r8/m8-at-rm32 if !SF and !ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = !ZF && SF == OF;
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x97: {  // set r8/m8-at-rm32 if !CF and !ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = (!CF && !ZF);
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x9d: {  // set r8/m8-at-rm32 if !SF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = (SF == OF);
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x93: {  // set r8/m8-at-rm32 if !CF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = !CF;
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x9c: {  // set r8/m8-at-rm32 if SF and !ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = (SF != OF);
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x92: {  // set r8/m8-at-rm32 if CF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = CF;
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x9e: {  // set r8/m8-at-rm32 if SF or ZF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = (ZF || SF != OF);
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}
case 0x96: {  // set r8/m8-at-rm32 if ZF or CF
  const uint8_t modrm = next();
  trace(Callstack_depth+1, "run") << "set r8/m8-at-rm32" << end();
  uint8_t* dest = effective_byte_address(modrm);
  *dest = (ZF || CF);
  trace(Callstack_depth+1, "run") << "storing " << NUM(*dest) << end();
  break;
}