4468

1 files changed, 205 insertions, 0 deletions

diff --git a/subx/032pack_operands.cc b/subx/032pack_operands.cc
new file mode 100644
index 00000000..f8effd16
--- /dev/null
+++ b/subx/032pack_operands.cc
@@ -0,0 +1,205 @@
+//: Operands can refer to bitfields smaller than a byte. This layer packs
+//: operands into their containing bytes in the right order.
+
+:(scenario pack_immediate_constants)
+== 0x1
+# instruction                     effective address                                                   operand     displacement    immediate
+# op          subop               mod             rm32          base        index         scale       r32
+# 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+  bb                                                                                                                              0x2a/imm32        # copy 42 to EBX
++transform: packing instruction 'bb 0x2a/imm32'
++transform: instruction after packing: 'bb 2a 00 00 00'
++run: copy imm32 0x0000002a to EBX
+
+:(scenario pack_disp8)
+== 0x1
+74 2/disp8  # jump 2 bytes away if ZF is set
++transform: packing instruction '74 2/disp8'
++transform: instruction after packing: '74 02'
+
+:(scenarios transform)
+:(scenario pack_disp8_negative)
+== 0x1
+# running this will cause an infinite loop
+74 -1/disp8  # jump 1 byte before if ZF is set
++transform: packing instruction '74 -1/disp8'
++transform: instruction after packing: '74 ff'
+:(scenarios run)
+
+:(scenario pack_modrm_imm32)
+== 0x1
+# instruction                     effective address                                                   operand     displacement    immediate
+# op          subop               mod             rm32          base        index         scale       r32
+# 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+  81          0/add/subop         3/mod/direct    3/ebx/rm32                                                                      1/imm32           # add 1 to EBX
++transform: packing instruction '81 0/add/subop 3/mod/direct 3/ebx/rm32 1/imm32'
++transform: instruction after packing: '81 c3 01 00 00 00'
+
+:(scenario pack_imm32_large)
+== 0x1
+b9 0x080490a7/imm32  # copy to ECX
++transform: packing instruction 'b9 0x080490a7/imm32'
++transform: instruction after packing: 'b9 a7 90 04 08'
+
+:(before "End One-time Setup")
+Transform.push_back(pack_operands);
+
+:(code)
+void pack_operands(program& p) {
+  trace(99, "transform") << "-- pack operands" << end();
+  if (p.segments.empty()) return;
+  segment& code = p.segments.at(0);
+  for (int i = 0;  i < SIZE(code.lines);  ++i) {
+    line& inst = code.lines.at(i);
+    if (all_hex_bytes(inst)) continue;
+    trace(99, "transform") << "packing instruction '" << to_string(/*with metadata*/inst) << "'" << end();
+    pack_operands(inst);
+    trace(99, "transform") << "instruction after packing: '" << to_string(/*without metadata*/inst.words) << "'" << end();
+  }
+}
+
+void pack_operands(line& inst) {
+  line new_inst;
+  add_opcodes(inst, new_inst);
+  add_modrm_byte(inst, new_inst);
+  add_sib_byte(inst, new_inst);
+  add_disp_bytes(inst, new_inst);
+  add_imm_bytes(inst, new_inst);
+  inst.words.swap(new_inst.words);
+}
+
+void add_opcodes(const line& in, line& out) {
+  out.words.push_back(in.words.at(0));
+  if (in.words.at(0).data == "0f" || in.words.at(0).data == "f3")
+    out.words.push_back(in.words.at(1));
+  if (in.words.at(0).data == "f3" && in.words.at(1).data == "0f")
+    out.words.push_back(in.words.at(2));
+}
+
+void add_modrm_byte(const line& in, line& out) {
+  uint8_t mod=0, reg_subop=0, rm32=0;
+  bool emit = false;
+  for (int i = 0;  i < SIZE(in.words);  ++i) {
+    const word& curr = in.words.at(i);
+    if (has_metadata(curr, "mod")) {
+      mod = hex_byte(curr.data);
+      emit = true;
+    }
+    else if (has_metadata(curr, "rm32")) {
+      rm32 = hex_byte(curr.data);
+      emit = true;
+    }
+    else if (has_metadata(curr, "r32")) {
+      reg_subop = hex_byte(curr.data);
+      emit = true;
+    }
+    else if (has_metadata(curr, "subop")) {
+      reg_subop = hex_byte(curr.data);
+      emit = true;
+    }
+  }
+  if (emit)
+    out.words.push_back(hex_byte_text((mod << 6) | (reg_subop << 3) | rm32));
+}
+
+void add_sib_byte(const line& in, line& out) {
+  uint8_t scale=0, index=0, base=0;
+  bool emit = false;
+  for (int i = 0;  i < SIZE(in.words);  ++i) {
+    const word& curr = in.words.at(i);
+    if (has_metadata(curr, "scale")) {
+      scale = hex_byte(curr.data);
+      emit = true;
+    }
+    else if (has_metadata(curr, "index")) {
+      index = hex_byte(curr.data);
+      emit = true;
+    }
+    else if (has_metadata(curr, "base")) {
+      base = hex_byte(curr.data);
+      emit = true;
+    }
+  }
+  if (emit)
+    out.words.push_back(hex_byte_text((scale << 6) | (index << 3) | base));
+}
+
+void add_disp_bytes(const line& in, line& out) {
+  for (int i = 0;  i < SIZE(in.words);  ++i) {
+    const word& curr = in.words.at(i);
+    if (has_metadata(curr, "disp8"))
+      emit_hex_bytes(out, curr, 1);
+    if (has_metadata(curr, "disp16"))
+      emit_hex_bytes(out, curr, 2);
+    else if (has_metadata(curr, "disp32"))
+      emit_hex_bytes(out, curr, 4);
+  }
+}
+
+void add_imm_bytes(const line& in, line& out) {
+  for (int i = 0;  i < SIZE(in.words);  ++i) {
+    const word& curr = in.words.at(i);
+    if (has_metadata(curr, "imm8"))
+      emit_hex_bytes(out, curr, 1);
+    else if (has_metadata(curr, "imm32"))
+      emit_hex_bytes(out, curr, 4);
+  }
+}
+
+void emit_hex_bytes(line& out, const word& w, int num) {
+  assert(num <= 4);
+  if (!is_hex_int(w.data)) {
+    out.words.push_back(w);
+    return;
+  }
+  emit_hex_bytes(out, static_cast<uint32_t>(parse_int(w.data)), num);
+}
+
+void emit_hex_bytes(line& out, uint32_t val, int num) {
+  assert(num <= 4);
+  for (int i = 0;  i < num;  ++i) {
+    out.words.push_back(hex_byte_text(val & 0xff));
+    val = val >> 8;
+  }
+}
+
+word hex_byte_text(uint8_t val) {
+  ostringstream out;
+  out << HEXBYTE << NUM(val);
+  word result;
+  result.data = out.str();
+  result.original = out.str()+"/auto";
+  return result;
+}
+
+string to_string(const vector<word>& in) {
+  ostringstream out;
+  for (int i = 0;  i < SIZE(in);  ++i) {
+    if (i > 0) out << ' ';
+    out << in.at(i).data;
+  }
+  return out.str();
+}
+
+:(scenario pack_immediate_constants_hex)
+== 0x1
+# instruction                     effective address                                                   operand     displacement    immediate
+# op          subop               mod             rm32          base        index         scale       r32
+# 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+  bb                                                                                                                              0x2a/imm32        # copy 42 to EBX
++transform: packing instruction 'bb 0x2a/imm32'
++transform: instruction after packing: 'bb 2a 00 00 00'
++run: copy imm32 0x0000002a to EBX
+
+:(scenarios transform)
+:(scenario pack_silently_ignores_non_hex)
+== 0x1
+# instruction                     effective address                                                   operand     displacement    immediate
+# op          subop               mod             rm32          base        index         scale       r32
+# 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+  bb                                                                                                                              foo/imm32         # copy foo to EBX
++transform: packing instruction 'bb foo/imm32'
+# no change (we're just not printing metadata to the trace)
++transform: instruction after packing: 'bb foo'
+$error: 0
+:(scenarios run)