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Diffstat (limited to 'linux/bootstrap/016index_addressing.cc')
-rw-r--r-- | linux/bootstrap/016index_addressing.cc | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/linux/bootstrap/016index_addressing.cc b/linux/bootstrap/016index_addressing.cc new file mode 100644 index 00000000..f6c6f2aa --- /dev/null +++ b/linux/bootstrap/016index_addressing.cc @@ -0,0 +1,155 @@ +//: operating on memory at the address provided by some register plus optional scale and offset + +:(code) +void test_add_r32_to_mem_at_rm32_with_sib() { + Reg[EBX].i = 0x10; + Reg[EAX].i = 0x2000; + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 01 1c 20 \n" // add EBX to *EAX + // ModR/M in binary: 00 (indirect mode) 011 (src EBX) 100 (dest in SIB) + // SIB in binary: 00 (scale 1) 100 (no index) 000 (base EAX) + "== data 0x2000\n" + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: add EBX to r/m32\n" + "run: effective address is initially 0x00002000 (EAX)\n" + "run: effective address is 0x00002000\n" + "run: storing 0x00000011\n" + ); +} + +:(before "End Mod 0 Special-cases(addr)") +case 4: // exception: mod 0b00 rm 0b100 => incoming SIB (scale-index-base) byte + addr = effective_address_from_sib(mod); + break; +:(code) +uint32_t effective_address_from_sib(uint8_t mod) { + const uint8_t sib = next(); + const uint8_t base = sib&0x7; + uint32_t addr = 0; + if (base != EBP || mod != 0) { + addr = Reg[base].u; + trace(Callstack_depth+1, "run") << "effective address is initially 0x" << HEXWORD << addr << " (" << rname(base) << ")" << end(); + } + else { + // base == EBP && mod == 0 + addr = next32(); // ignore base + trace(Callstack_depth+1, "run") << "effective address is initially 0x" << HEXWORD << addr << " (disp32)" << end(); + } + const uint8_t index = (sib>>3)&0x7; + if (index == ESP) { + // ignore index and scale + trace(Callstack_depth+1, "run") << "effective address is 0x" << HEXWORD << addr << end(); + } + else { + const uint8_t scale = (1 << (sib>>6)); + addr += Reg[index].i*scale; // treat index register as signed. Maybe base as well? But we'll always ensure it's non-negative. + trace(Callstack_depth+1, "run") << "effective address is 0x" << HEXWORD << addr << " (after adding " << rname(index) << "*" << NUM(scale) << ")" << end(); + } + return addr; +} + +:(code) +void test_add_r32_to_mem_at_base_r32_index_r32() { + Reg[EBX].i = 0x10; // source + Reg[EAX].i = 0x1ffe; // dest base + Reg[ECX].i = 0x2; // dest index + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 01 1c 08 \n" // add EBX to *(EAX+ECX) + // ModR/M in binary: 00 (indirect mode) 011 (src EBX) 100 (dest in SIB) + // SIB in binary: 00 (scale 1) 001 (index ECX) 000 (base EAX) + "== data 0x2000\n" + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: add EBX to r/m32\n" + "run: effective address is initially 0x00001ffe (EAX)\n" + "run: effective address is 0x00002000 (after adding ECX*1)\n" + "run: storing 0x00000011\n" + ); +} + +:(code) +void test_add_r32_to_mem_at_displacement_using_sib() { + Reg[EBX].i = 0x10; // source + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 01 1c 25 00 20 00 00 \n" // add EBX to *0x2000 + // ModR/M in binary: 00 (indirect mode) 011 (src EBX) 100 (dest in SIB) + // SIB in binary: 00 (scale 1) 100 (no index) 101 (not EBP but disp32) + "== data 0x2000\n" + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: add EBX to r/m32\n" + "run: effective address is initially 0x00002000 (disp32)\n" + "run: effective address is 0x00002000\n" + "run: storing 0x00000011\n" + ); +} + +//: + +:(code) +void test_add_r32_to_mem_at_base_r32_index_r32_plus_disp8() { + Reg[EBX].i = 0x10; // source + Reg[EAX].i = 0x1ff9; // dest base + Reg[ECX].i = 0x5; // dest index + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 01 5c 08 02 \n" // add EBX to *(EAX+ECX+2) + // ModR/M in binary: 01 (indirect+disp8 mode) 011 (src EBX) 100 (dest in SIB) + // SIB in binary: 00 (scale 1) 001 (index ECX) 000 (base EAX) + "== data 0x2000\n" + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: add EBX to r/m32\n" + "run: effective address is initially 0x00001ff9 (EAX)\n" + "run: effective address is 0x00001ffe (after adding ECX*1)\n" + "run: effective address is 0x00002000 (after adding disp8)\n" + "run: storing 0x00000011\n" + ); +} + +:(before "End Mod 1 Special-cases(addr)") +case 4: // exception: mod 0b01 rm 0b100 => incoming SIB (scale-index-base) byte + addr = effective_address_from_sib(mod); + break; + +//: + +:(code) +void test_add_r32_to_mem_at_base_r32_index_r32_plus_disp32() { + Reg[EBX].i = 0x10; // source + Reg[EAX].i = 0x1ff9; // dest base + Reg[ECX].i = 0x5; // dest index + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 01 9c 08 02 00 00 00 \n" // add EBX to *(EAX+ECX+2) + // ModR/M in binary: 10 (indirect+disp32 mode) 011 (src EBX) 100 (dest in SIB) + // SIB in binary: 00 (scale 1) 001 (index ECX) 000 (base EAX) + "== data 0x2000\n" + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: add EBX to r/m32\n" + "run: effective address is initially 0x00001ff9 (EAX)\n" + "run: effective address is 0x00001ffe (after adding ECX*1)\n" + "run: effective address is 0x00002000 (after adding disp32)\n" + "run: storing 0x00000011\n" + ); +} + +:(before "End Mod 2 Special-cases(addr)") +case 4: // exception: mod 0b10 rm 0b100 => incoming SIB (scale-index-base) byte + addr = effective_address_from_sib(mod); + break; |