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MIT/X Consortium License

© 2006-2008 Anselm R Garbe <garbeam at gmail dot com>
© 2006-2007 Sander van Dijk <a dot h dot vandijk at gmail dot com>
© 2006-2007 Jukka Salmi <jukka at salmi dot ch>
© 2007 Premysl Hruby <dfenze at gmail dot com>
© 2007 Szabolcs Nagy <nszabolcs at gmail dot com>
© 2007 Christof Musik <christof at sendfax dot de>
© 2007-2008 Enno Gottox Boland <gottox at s01 dot de>

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the 
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in 
all copies or substantial portions of the Software. 

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL 
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
DEALINGS IN THE SOFTWARE.
//: Global variables.
//:
//: Global variables are just labels in the data segment.
//: However, they can only be used in imm32 and not disp32 operands. And they
//: can't be used with jump and call instructions.
//:
//: This layer has much the same structure as rewriting labels.

:(code)
void test_global_variable() {
  run(
      "== code\n"
      "b9  x/imm32\n"
      "== data\n"
      "x:\n"
      "  00 00 00 00\n"
  );
  CHECK_TRACE_CONTENTS(
      "transform: global variable 'x' is at address 0x0a000079\n"
  );
}

:(before "End Level-2 Transforms")
Transform.push_back(rewrite_global_variables);
:(code)
void rewrite_global_variables(program& p) {
  trace(3, "transform") << "-- rewrite global variables" << end();
  // Begin rewrite_global_variables
  map<string, uint32_t> address;
  compute_addresses_for_global_variables(p, address);
  if (trace_contains_errors()) return;
  drop_global_variables(p);
  replace_global_variables_with_addresses(p, address);
}

void compute_addresses_for_global_variables(const program& p, map<string, uint32_t>& address) {
  for (int i = /*skip code segment*/1;  i < SIZE(p.segments);  ++i)
    compute_addresses_for_global_variables(p.segments.at(i), address);
}

void compute_addresses_for_global_variables(const segment& s, map<string, uint32_t>& address) {
  int current_address = s.start;
  for (int i = 0;  i < SIZE(s.lines);  ++i) {
    const line& inst = s.lines.at(i);
    for (int j = 0;  j < SIZE(inst.words);  ++j) {
      const word& curr = inst.words.at(j);
      if (*curr.data.rbegin() != ':') {
        current_address += size_of(curr);
      }
      else {
        string variable = drop_last(curr.data);
        // ensure variables look sufficiently different from raw hex
        check_valid_name(variable);
        if (trace_contains_errors()) return;
        if (j > 0)
          raise << "'" << to_string(inst) << "': global variable names can only be the first word in a line.\n" << end();
        if (Map_file.is_open())
          Map_file << "0x" << HEXWORD << current_address << ' ' << variable << '\n';
        if (contains_key(address, variable)) {
          raise << "duplicate global '" << variable << "'\n" << end();
          return;
        }
        put(address, variable, current_address);
        trace(99, "transform") << "global variable '" << variable << "' is at address 0x" << HEXWORD << current_address << end();
        // no modifying current_address; global variable definitions won't be in the final binary
      }
    }
  }
}

void drop_global_variables(program& p) {
  for (int i = /*skip code segment*/1;  i < SIZE(p.segments);  ++i)
    drop_labels(p.segments.at(i));
}

void replace_global_variables_with_addresses(program& p, const map<string, uint32_t>& address) {
  if (p.segments.empty()) return;
  replace_global_variables_in_code_segment(p.segments.at(0), address);
  for (int i = /*skip code*/1;  i < SIZE(p.segments);  ++i)
    replace_global_variables_in_data_segment(p.segments.at(i), address);
}

void replace_global_variables_in_code_segment(segment& code, const map<string, uint32_t>& address) {
  for (int i = 0;  i < SIZE(code.lines);  ++i) {
    line& inst = code.lines.at(i);
    line new_inst;
    for (int j = 0;  j < SIZE(inst.words);  ++j) {
      const word& curr = inst.words.at(j);
      if (!contains_key(address, curr.data)) {
        if (!looks_like_hex_int(curr.data))
          raise << "missing reference to global '" << curr.data << "'\n" << end();
        new_inst.words.push_back(curr);
        continue;
      }
      if (!valid_use_of_global_variable(curr)) {
        raise << "'" << to_string(inst) << "': can't refer to global variable '" << curr.data << "'\n" << end();
        return;
      }
      emit_hex_bytes(new_inst, get(address, curr.data), 4);
    }
    inst.words.swap(new_inst.words);
    trace(99, "transform") << "instruction after transform: '" << data_to_string(inst) << "'" << end();
  }
}

void replace_global_variables_in_data_segment(segment& data, const map<string, uint32_t>& address) {
  for (int i = 0;  i < SIZE(data.lines);  ++i) {
    line& l = data.lines.at(i);
    line new_l;
    for (int j = 0;  j < SIZE(l.words);  ++j) {
      const word& curr = l.words.at(j);
      if (!contains_key(address, curr.data)) {
        if (looks_like_hex_int(curr.data)) {
          if (has_operand_metadata(curr, "imm32"))
            emit_hex_bytes(new_l, curr, 4);
          else if (has_operand_metadata(curr, "imm16"))
            emit_hex_bytes(new_l, curr, 2);
          else if (has_operand_metadata(curr, "imm8"))
            emit_hex_bytes(new_l, curr, 1);
          else if (has_operand_metadata(curr, "disp8"))
            raise << "can't use /disp8 in a non-code segment\n" << end();
          else if (has_operand_metadata(curr, "disp16"))
            raise << "can't use /disp16 in a non-code segment\n" << end();
          else if (has_operand_metadata(curr, "disp32"))
            raise << "can't use /disp32 in a non-code segment\n" << end();
          else
            new_l.words.push_back(curr);
        }
        else {
          raise << "missing reference to global '" << curr.data << "'\n" << end();
          new_l.words.push_back(curr);
        }
        continue;
      }
      trace(99, "transform") << curr.data << " maps to " << HEXWORD << get(address, curr.data) << end();
      emit_hex_bytes(new_l, get(address, curr.data), 4);
    }
    l.words.swap(new_l.words);
    trace(99, "transform") << "after transform: '" << data_to_string(l) << "'" << end();
  }
}

bool valid_use_of_global_variable(const word& curr) {
  if (has_operand_metadata(curr, "imm32")) return true;
  // End Valid Uses Of Global Variable(curr)
  return false;
}

//:: a more complex sanity check for how we use global variables
//: requires first saving some data early before we pack operands

:(after "Begin Level-2 Transforms")
Transform.push_back(correlate_disp32_with_mod);
:(code)
void correlate_disp32_with_mod(program& p) {
  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);
    for (int j = 0;  j < SIZE(inst.words);  ++j) {
      word& curr = inst.words.at(j);
      if (has_operand_metadata(curr, "disp32")
          && has_operand_metadata(inst, "mod"))
        curr.metadata.push_back("has_mod");
    }
  }
}

:(before "End Valid Uses Of Global Variable(curr)")
if (has_operand_metadata(curr, "disp32"))
  return has_metadata(curr, "has_mod");
// todo: more sophisticated check, to ensure we don't use global variable
// addresses as a real displacement added to other operands.

:(code)
bool has_metadata(const word& w, const string& m) {
  for (int i = 0;  i < SIZE(w.metadata);  ++i)
    if (w.metadata.at(i) == m) return true;
  return false;
}

void test_global_variable_disallowed_in_jump() {
  Hide_errors = true;
  run(
      "== code\n"
      "eb/jump  x/disp8\n"
      "== data\n"
      "x:\n"
      "  00 00 00 00\n"
  );
  CHECK_TRACE_CONTENTS(
      "error: 'eb/jump x/disp8': can't refer to global variable 'x'\n"
      // sub-optimal error message; should be
//?       "error: can't jump to data (variable 'x')\n"
  );
}

void test_global_variable_disallowed_in_call() {
  Hide_errors = true;
  run(
      "== code\n"
      "e8/call  x/disp32\n"
      "== data\n"
      "x:\n"
      "  00 00 00 00\n"
  );
  CHECK_TRACE_CONTENTS(
      "error: 'e8/call x/disp32': can't refer to global variable 'x'\n"
      // sub-optimal error message; should be
//?       "error: can't call to the data segment ('x')\n"
  );
}

void test_global_variable_in_data_segment() {
  run(
      "== 0x1\n"
      "b9  x/imm32\n"
      "== 0x0a000000\n"
      "x:\n"
      "  y/imm32\n"
      "y:\n"
      "  00 00 00 00\n"
  );
  // check that we loaded 'x' with the address of 'y'
  CHECK_TRACE_CONTENTS(
      "load: 0x0a000000 -> 04\n"
      "load: 0x0a000001 -> 00\n"
      "load: 0x0a000002 -> 00\n"
      "load: 0x0a000003 -> 0a\n"
  );
  CHECK_TRACE_COUNT("error", 0);
}

void test_raw_number_with_imm32_in_data_segment() {
  run(
      "== 0x1\n"
      "b9  x/imm32\n"
      "== 0x0a000000\n"
      "x:\n"
      "  1/imm32\n"
  );
  // check that we loaded 'x' with the address of 1
  CHECK_TRACE_CONTENTS(
      "load: 0x0a000000 -> 01\n"
      "load: 0x0a000001 -> 00\n"
      "load: 0x0a000002 -> 00\n"
      "load: 0x0a000003 -> 00\n"
  );
  CHECK_TRACE_COUNT("error", 0);
}

void test_duplicate_global_variable() {
  Hide_errors = true;
  run(
      "== 0x1\n"
      "40/increment-EAX\n"
      "== 0x0a000000\n"
      "x:\n"
      "x:\n"
      "  00\n"
  );
  CHECK_TRACE_CONTENTS(
      "error: duplicate global 'x'\n"
  );
}

void test_global_variable_disp32_with_modrm() {
  run(
      "== code\n"
      "8b/copy 0/mod/indirect 5/rm32/.disp32 2/r32/EDX x/disp32\n"
      "== data\n"
      "x:\n"
      "  00 00 00 00\n"
  );
  CHECK_TRACE_COUNT("error", 0);
}

void test_global_variable_disp32_with_call() {
  transform(
      "== code\n"
      "foo:\n"
      "  e8/call bar/disp32\n"
      "bar:\n"
  );
  CHECK_TRACE_COUNT("error", 0);
}

string to_full_string(const line& in) {
  ostringstream out;
  for (int i = 0;  i < SIZE(in.words);  ++i) {
    if (i > 0) out << ' ';
    out << in.words.at(i).data;
    for (int j = 0;  j < SIZE(in.words.at(i).metadata);  ++j)
      out << '/' << in.words.at(i).metadata.at(j);
  }
  return out.str();
}