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1 files changed, 323 insertions, 0 deletions

diff --git a/subx/012direct_addressing.cc b/subx/012direct_addressing.cc
new file mode 100644
index 00000000..fffcbd6a
--- /dev/null
+++ b/subx/012direct_addressing.cc
@@ -0,0 +1,323 @@
+//: operating directly on a register
+
+:(scenario add_r32_to_r32)
+% Reg[EAX].i = 0x10;
+% Reg[EBX].i = 1;
+# op  ModR/M  SIB   displacement  immediate
+  01  d8                                      # add EBX to EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: add EBX to r/m32
++run: r/m32 is EAX
++run: storing 0x00000011
+
+:(before "End Single-Byte Opcodes")
+case 0x01: {  // add r32 to r/m32
+  uint8_t modrm = next();
+  uint8_t arg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "add " << rname(arg2) << " to r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  BINARY_ARITHMETIC_OP(+, *arg1, Reg[arg2].i);
+  break;
+}
+
+:(code)
+// Implement tables 2-2 and 2-3 in the Intel manual, Volume 2.
+// We return a pointer so that instructions can write to multiple bytes in
+// 'Mem' at once.
+int32_t* effective_address(uint8_t modrm) {
+  uint8_t mod = (modrm>>6);
+  // ignore middle 3 'reg opcode' bits
+  uint8_t rm = modrm & 0x7;
+  uint32_t addr = 0;
+  switch (mod) {
+  case 3:
+    // mod 3 is just register direct addressing
+    trace(2, "run") << "r/m32 is " << rname(rm) << end();
+    return &Reg[rm].i;
+  // End Mod Special-cases(addr)
+  default:
+    cerr << "unrecognized mod bits: " << NUM(mod) << '\n';
+    exit(1);
+  }
+  //: other mods are indirect, and they'll set addr appropriately
+  return mem_addr_i32(addr);
+}
+
+//:: subtract
+
+:(scenario subtract_r32_from_r32)
+% Reg[EAX].i = 10;
+% Reg[EBX].i = 1;
+# op  ModR/M  SIB   displacement  immediate
+  29  d8                                      # subtract EBX from EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: subtract EBX from r/m32
++run: r/m32 is EAX
++run: storing 0x00000009
+
+:(before "End Single-Byte Opcodes")
+case 0x29: {  // subtract r32 from r/m32
+  uint8_t modrm = next();
+  uint8_t arg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "subtract " << rname(arg2) << " from r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  BINARY_ARITHMETIC_OP(-, *arg1, Reg[arg2].i);
+  break;
+}
+
+//:: and
+
+:(scenario and_r32_with_r32)
+% Reg[EAX].i = 0x0a0b0c0d;
+% Reg[EBX].i = 0x000000ff;
+# op  ModR/M  SIB   displacement  immediate
+  21  d8                                      # and EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: and EBX with r/m32
++run: r/m32 is EAX
++run: storing 0x0000000d
+
+:(before "End Single-Byte Opcodes")
+case 0x21: {  // and r32 with r/m32
+  uint8_t modrm = next();
+  uint8_t arg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "and " << rname(arg2) << " with r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  BINARY_BITWISE_OP(&, *arg1, Reg[arg2].u);
+  break;
+}
+
+//:: or
+
+:(scenario or_r32_with_r32)
+% Reg[EAX].i = 0x0a0b0c0d;
+% Reg[EBX].i = 0xa0b0c0d0;
+# op  ModR/M  SIB   displacement  immediate
+  09  d8                                      # or EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: or EBX with r/m32
++run: r/m32 is EAX
++run: storing 0xaabbccdd
+
+:(before "End Single-Byte Opcodes")
+case 0x09: {  // or r32 with r/m32
+  uint8_t modrm = next();
+  uint8_t arg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "or " << rname(arg2) << " with r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  BINARY_BITWISE_OP(|, *arg1, Reg[arg2].u);
+  break;
+}
+
+//:: xor
+
+:(scenario xor_r32_with_r32)
+% Reg[EAX].i = 0x0a0b0c0d;
+% Reg[EBX].i = 0xaabbc0d0;
+# op  ModR/M  SIB   displacement  immediate
+  31  d8                                      # xor EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: xor EBX with r/m32
++run: r/m32 is EAX
++run: storing 0xa0b0ccdd
+
+:(before "End Single-Byte Opcodes")
+case 0x31: {  // xor r32 with r/m32
+  uint8_t modrm = next();
+  uint8_t arg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "xor " << rname(arg2) << " with r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  BINARY_BITWISE_OP(^, *arg1, Reg[arg2].u);
+  break;
+}
+
+//:: not
+
+:(scenario not_r32)
+% Reg[EBX].i = 0x0f0f00ff;
+# op  ModR/M  SIB   displacement  immediate
+  f7  c3                                      # not EBX
+# ModR/M in binary: 11 (direct mode) 000 (unused) 011 (dest EBX)
++run: 'not' of r/m32
++run: r/m32 is EBX
++run: storing 0xf0f0ff00
+
+:(before "End Single-Byte Opcodes")
+case 0xf7: {  // xor r32 with r/m32
+  uint8_t modrm = next();
+  trace(2, "run") << "'not' of r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  *arg1 = ~(*arg1);
+  trace(2, "run") << "storing 0x" << HEXWORD << *arg1 << end();
+  SF = (*arg1 >> 31);
+  ZF = (*arg1 == 0);
+  OF = false;
+  break;
+}
+
+//:: compare (cmp)
+
+:(scenario compare_r32_with_r32_greater)
+% Reg[EAX].i = 0x0a0b0c0d;
+% Reg[EBX].i = 0x0a0b0c07;
+# op  ModR/M  SIB   displacement  immediate
+  39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: compare EBX with r/m32
++run: r/m32 is EAX
++run: SF=0; ZF=0; OF=0
+
+:(before "End Single-Byte Opcodes")
+case 0x39: {  // set SF if r/m32 < r32
+  uint8_t modrm = next();
+  uint8_t reg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "compare " << rname(reg2) << " with r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  int32_t arg2 = Reg[reg2].i;
+  int32_t tmp1 = *arg1 - arg2;
+  SF = (tmp1 < 0);
+  ZF = (tmp1 == 0);
+  int64_t tmp2 = *arg1 - arg2;
+  OF = (tmp1 != tmp2);
+  trace(2, "run") << "SF=" << SF << "; ZF=" << ZF << "; OF=" << OF << end();
+  break;
+}
+
+:(scenario compare_r32_with_r32_lesser)
+% Reg[EAX].i = 0x0a0b0c07;
+% Reg[EBX].i = 0x0a0b0c0d;
+# op  ModR/M  SIB   displacement  immediate
+  39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: compare EBX with r/m32
++run: r/m32 is EAX
++run: SF=1; ZF=0; OF=0
+
+:(scenario compare_r32_with_r32_equal)
+% Reg[EAX].i = 0x0a0b0c0d;
+% Reg[EBX].i = 0x0a0b0c0d;
+# op  ModR/M  SIB   displacement  immediate
+  39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: compare EBX with r/m32
++run: r/m32 is EAX
++run: SF=0; ZF=1; OF=0
+
+//:: copy (mov)
+
+:(scenario copy_r32_to_r32)
+% Reg[EBX].i = 0xaf;
+# op  ModR/M  SIB   displacement  immediate
+  89  d8                                      # copy EBX to EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: copy EBX to r/m32
++run: r/m32 is EAX
++run: storing 0x000000af
+
+:(before "End Single-Byte Opcodes")
+case 0x89: {  // copy r32 to r/m32
+  uint8_t modrm = next();
+  uint8_t reg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "copy " << rname(reg2) << " to r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  *arg1 = Reg[reg2].i;
+  trace(2, "run") << "storing 0x" << HEXWORD << *arg1 << end();
+  break;
+}
+
+//:: xchg
+
+:(scenario xchg_r32_with_r32)
+% Reg[EBX].i = 0xaf;
+% Reg[EAX].i = 0x2e;
+# op  ModR/M  SIB   displacement  immediate
+  87  d8                                      # exchange EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
++run: exchange EBX with r/m32
++run: r/m32 is EAX
++run: storing 0x000000af in r/m32
++run: storing 0x0000002e in EBX
+
+:(before "End Single-Byte Opcodes")
+case 0x87: {  // exchange r32 with r/m32
+  uint8_t modrm = next();
+  uint8_t reg2 = (modrm>>3)&0x7;
+  trace(2, "run") << "exchange " << rname(reg2) << " with r/m32" << end();
+  int32_t* arg1 = effective_address(modrm);
+  int32_t tmp = *arg1;
+  *arg1 = Reg[reg2].i;
+  Reg[reg2].i = tmp;
+  trace(2, "run") << "storing 0x" << HEXWORD << *arg1 << " in r/m32" << end();
+  trace(2, "run") << "storing 0x" << HEXWORD << Reg[reg2].i << " in " << rname(reg2) << end();
+  break;
+}
+
+//:: push
+
+:(scenario push_r32)
+% Reg[ESP].u = 0x64;
+% Reg[EBX].i = 0x0000000a;
+# op  ModR/M  SIB   displacement  immediate
+  53                                          # push EBX to stack
++run: push EBX
++run: decrementing ESP to 0x00000060
++run: pushing value 0x0000000a
+
+:(before "End Single-Byte Opcodes")
+case 0x50:
+case 0x51:
+case 0x52:
+case 0x53:
+case 0x54:
+case 0x55:
+case 0x56:
+case 0x57: {  // push r32 to stack
+  uint8_t reg = op & 0x7;
+  trace(2, "run") << "push " << rname(reg) << end();
+  push(Reg[reg].u);
+  break;
+}
+:(code)
+void push(uint32_t val) {
+  Reg[ESP].u -= 4;
+  trace(2, "run") << "decrementing ESP to 0x" << HEXWORD << Reg[ESP].u << end();
+  trace(2, "run") << "pushing value 0x" << HEXWORD << val << end();
+  write_mem_u32(Reg[ESP].u, val);
+}
+
+//:: pop
+
+:(scenario pop_r32)
+% Reg[ESP].u = 0x60;
+% write_mem_i32(0x60, 0x0000000a);
+== 0x1  # code segment
+# op  ModR/M  SIB   displacement  immediate
+  5b                                          # pop stack to EBX
+== 0x60  # data segment
+0a 00 00 00  # 0x0a
++run: pop into EBX
++run: popping value 0x0000000a
++run: incrementing ESP to 0x00000064
+
+:(before "End Single-Byte Opcodes")
+case 0x58:
+case 0x59:
+case 0x5a:
+case 0x5b:
+case 0x5c:
+case 0x5d:
+case 0x5e:
+case 0x5f: {  // pop stack into r32
+  uint8_t reg = op & 0x7;
+  trace(2, "run") << "pop into " << rname(reg) << end();
+  Reg[reg].u = pop();
+  break;
+}
+:(code)
+uint32_t pop() {
+  uint32_t result = read_mem_u32(Reg[ESP].u);
+  trace(2, "run") << "popping value 0x" << HEXWORD << result << end();
+  Reg[ESP].u += 4;
+  trace(2, "run") << "incrementing ESP to 0x" << HEXWORD << Reg[ESP].u << end();
+  return result;
+}