diff options
| -rw-r--r-- | subx/014index_addressing.cc | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/subx/014index_addressing.cc b/subx/014index_addressing.cc index 666b775d..4788216b 100644 --- a/subx/014index_addressing.cc +++ b/subx/014index_addressing.cc @@ -14,11 +14,12 @@ +run: storing 0x00000011 :(before "End Mod 0 Special-cases") -case 4: // exception: mod 0b00 rm 0b100 => incoming SIB (scale-index-base) byte +case 4: { // exception: mod 0b00 rm 0b100 => incoming SIB (scale-index-base) byte uint32_t addr = effective_address_from_sib(mod); if (addr == 0) break; result = reinterpret_cast<int32_t*>(&Mem.at(addr)); break; +} :(code) uint32_t effective_address_from_sib(uint8_t mod) { uint8_t sib = next(); @@ -73,3 +74,25 @@ uint32_t effective_address_from_sib(uint8_t mod) { +run: effective address is initially 0x60 (disp32) +run: effective address is 0x60 +run: storing 0x00000011 + +//: + +:(scenario add_r32_to_mem_at_displacement) +% Reg[3].i = 0x10; // source +% Reg[0].i = 0x5e; // dest base +% Reg[1].i = 0x2; // dest index +% SET_WORD_IN_MEM(0x60, 1); +# op ModR/M SIB displacement immediate + 01 1d 60 00 00 00 # add EBX to *0x60 +# ModR/M in binary: 00 (indirect mode) 011 (src EBX) 101 (dest in disp32) ++run: add EBX to r/m32 ++run: effective address is 0x60 (disp32) ++run: storing 0x00000011 + +:(before "End Mod 0 Special-cases") +case 5: { // exception: mod 0b00 rm 0b101 => incoming disp32 + uint32_t addr = imm32(); + result = reinterpret_cast<int32_t*>(&Mem.at(addr)); + trace(2, "run") << "effective address is 0x" << std::hex << addr << " (disp32)" << end(); + break; +} |