306 lines
9.4 KiB
C++
306 lines
9.4 KiB
C++
//: Global variables.
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//:
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//: Global variables are just labels in the data segment.
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//: However, they can only be used in imm32 and not disp32 operands. And they
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//: can't be used with jump and call instructions.
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//:
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//: This layer has much the same structure as rewriting labels.
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:(code)
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void test_global_variable() {
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run(
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"== code 0x1\n"
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"b9 x/imm32\n"
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"== data 0x2000\n"
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"x:\n"
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" 00 00 00 00\n"
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);
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CHECK_TRACE_CONTENTS(
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"transform: global variable 'x' is at address 0x00002000\n"
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);
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}
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:(before "End Level-2 Transforms")
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Transform.push_back(rewrite_global_variables);
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:(code)
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void rewrite_global_variables(program& p) {
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trace(3, "transform") << "-- rewrite global variables" << end();
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// Begin rewrite_global_variables
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map<string, uint32_t> address;
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compute_addresses_for_global_variables(p, address);
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if (trace_contains_errors()) return;
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drop_global_variables(p);
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replace_global_variables_with_addresses(p, address);
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}
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void compute_addresses_for_global_variables(const program& p, map<string, uint32_t>& address) {
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for (int i = 0; i < SIZE(p.segments); ++i) {
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if (p.segments.at(i).name != "code")
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compute_addresses_for_global_variables(p.segments.at(i), address);
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}
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}
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void compute_addresses_for_global_variables(const segment& s, map<string, uint32_t>& address) {
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int current_address = s.start;
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for (int i = 0; i < SIZE(s.lines); ++i) {
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const line& inst = s.lines.at(i);
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for (int j = 0; j < SIZE(inst.words); ++j) {
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const word& curr = inst.words.at(j);
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if (*curr.data.rbegin() != ':') {
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current_address += size_of(curr);
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}
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else {
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string variable = drop_last(curr.data);
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// ensure variables look sufficiently different from raw hex
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check_valid_name(variable);
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if (trace_contains_errors()) return;
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if (j > 0)
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raise << "'" << to_string(inst) << "': global variable names can only be the first word in a line.\n" << end();
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if (Labels_file.is_open())
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Labels_file << "0x" << HEXWORD << current_address << ' ' << variable << '\n';
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if (contains_key(address, variable)) {
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raise << "duplicate global '" << variable << "'\n" << end();
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return;
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}
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put(address, variable, current_address);
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trace(99, "transform") << "global variable '" << variable << "' is at address 0x" << HEXWORD << current_address << end();
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// no modifying current_address; global variable definitions won't be in the final binary
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}
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}
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}
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}
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void drop_global_variables(program& p) {
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for (int i = 0; i < SIZE(p.segments); ++i) {
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if (p.segments.at(i).name != "code")
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drop_labels(p.segments.at(i));
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}
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}
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void replace_global_variables_with_addresses(program& p, const map<string, uint32_t>& address) {
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if (p.segments.empty()) return;
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for (int i = 0; i < SIZE(p.segments); ++i) {
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segment& curr = p.segments.at(i);
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if (curr.name == "code")
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replace_global_variables_in_code_segment(curr, address);
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else
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replace_global_variables_in_data_segment(curr, address);
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}
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}
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void replace_global_variables_in_code_segment(segment& code, const map<string, uint32_t>& address) {
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for (int i = 0; i < SIZE(code.lines); ++i) {
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line& inst = code.lines.at(i);
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line new_inst;
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for (int j = 0; j < SIZE(inst.words); ++j) {
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const word& curr = inst.words.at(j);
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if (!contains_key(address, curr.data)) {
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if (!looks_like_hex_int(curr.data))
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raise << "missing reference to global '" << curr.data << "'\n" << end();
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new_inst.words.push_back(curr);
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continue;
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}
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if (!valid_use_of_global_variable(curr)) {
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raise << "'" << to_string(inst) << "': can't refer to global variable '" << curr.data << "'\n" << end();
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return;
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}
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emit_hex_bytes(new_inst, get(address, curr.data), 4);
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}
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inst.words.swap(new_inst.words);
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trace(99, "transform") << "instruction after transform: '" << data_to_string(inst) << "'" << end();
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}
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}
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void replace_global_variables_in_data_segment(segment& data, const map<string, uint32_t>& address) {
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for (int i = 0; i < SIZE(data.lines); ++i) {
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line& l = data.lines.at(i);
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line new_l;
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for (int j = 0; j < SIZE(l.words); ++j) {
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const word& curr = l.words.at(j);
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if (!contains_key(address, curr.data)) {
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if (looks_like_hex_int(curr.data)) {
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if (has_operand_metadata(curr, "imm32"))
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emit_hex_bytes(new_l, curr, 4);
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else if (has_operand_metadata(curr, "imm16"))
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emit_hex_bytes(new_l, curr, 2);
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else if (has_operand_metadata(curr, "imm8"))
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emit_hex_bytes(new_l, curr, 1);
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else if (has_operand_metadata(curr, "disp8"))
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raise << "can't use /disp8 in a non-code segment\n" << end();
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else if (has_operand_metadata(curr, "disp16"))
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raise << "can't use /disp16 in a non-code segment\n" << end();
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else if (has_operand_metadata(curr, "disp32"))
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raise << "can't use /disp32 in a non-code segment\n" << end();
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else
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new_l.words.push_back(curr);
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}
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else {
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raise << "missing reference to global '" << curr.data << "'\n" << end();
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new_l.words.push_back(curr);
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}
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continue;
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}
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trace(99, "transform") << curr.data << " maps to " << HEXWORD << get(address, curr.data) << end();
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emit_hex_bytes(new_l, get(address, curr.data), 4);
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}
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l.words.swap(new_l.words);
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trace(99, "transform") << "after transform: '" << data_to_string(l) << "'" << end();
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}
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}
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bool valid_use_of_global_variable(const word& curr) {
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if (has_operand_metadata(curr, "imm32")) return true;
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// End Valid Uses Of Global Variable(curr)
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return false;
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}
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//:: a more complex sanity check for how we use global variables
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//: requires first saving some data early before we pack operands
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:(after "Begin Level-2 Transforms")
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Transform.push_back(correlate_disp32_with_mod);
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:(code)
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void correlate_disp32_with_mod(program& p) {
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if (p.segments.empty()) return;
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segment& code = *find(p, "code");
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for (int i = 0; i < SIZE(code.lines); ++i) {
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line& inst = code.lines.at(i);
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for (int j = 0; j < SIZE(inst.words); ++j) {
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word& curr = inst.words.at(j);
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if (has_operand_metadata(curr, "disp32")
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&& has_operand_metadata(inst, "mod"))
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curr.metadata.push_back("has_mod");
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}
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}
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}
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:(before "End Valid Uses Of Global Variable(curr)")
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if (has_operand_metadata(curr, "disp32"))
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return has_metadata(curr, "has_mod");
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// todo: more sophisticated check, to ensure we don't use global variable
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// addresses as a real displacement added to other operands.
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:(code)
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bool has_metadata(const word& w, const string& m) {
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for (int i = 0; i < SIZE(w.metadata); ++i)
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if (w.metadata.at(i) == m) return true;
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return false;
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}
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void test_global_variable_disallowed_in_jump() {
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Hide_errors = true;
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run(
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"== code 0x1\n"
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"eb/jump x/disp8\n"
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"== data 0x2000\n"
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"x:\n"
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" 00 00 00 00\n"
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);
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CHECK_TRACE_CONTENTS(
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"error: 'eb/jump x/disp8': can't refer to global variable 'x'\n"
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// sub-optimal error message; should be
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//? "error: can't jump to data (variable 'x')\n"
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);
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}
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void test_global_variable_disallowed_in_call() {
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Hide_errors = true;
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run(
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"== code 0x1\n"
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"e8/call x/disp32\n"
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"== data 0x2000\n"
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"x:\n"
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" 00 00 00 00\n"
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);
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CHECK_TRACE_CONTENTS(
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"error: 'e8/call x/disp32': can't refer to global variable 'x'\n"
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// sub-optimal error message; should be
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//? "error: can't call to the data segment ('x')\n"
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);
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}
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void test_global_variable_in_data_segment() {
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run(
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"== code 0x1\n"
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"b9 x/imm32\n"
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"== data 0x2000\n"
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"x:\n"
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" y/imm32\n"
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"y:\n"
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" 00 00 00 00\n"
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);
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// check that we loaded 'x' with the address of 'y'
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CHECK_TRACE_CONTENTS(
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"load: 0x00002000 -> 04\n"
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"load: 0x00002001 -> 20\n"
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"load: 0x00002002 -> 00\n"
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"load: 0x00002003 -> 00\n"
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);
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CHECK_TRACE_COUNT("error", 0);
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}
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void test_raw_number_with_imm32_in_data_segment() {
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run(
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"== code 0x1\n"
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"b9 x/imm32\n"
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"== data 0x2000\n"
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"x:\n"
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" 1/imm32\n"
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);
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// check that we loaded 'x' with the address of 1
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CHECK_TRACE_CONTENTS(
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"load: 0x00002000 -> 01\n"
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"load: 0x00002001 -> 00\n"
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"load: 0x00002002 -> 00\n"
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"load: 0x00002003 -> 00\n"
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);
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CHECK_TRACE_COUNT("error", 0);
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}
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void test_duplicate_global_variable() {
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Hide_errors = true;
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run(
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"== code 0x1\n"
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"40/increment-EAX\n"
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"== data 0x2000\n"
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"x:\n"
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"x:\n"
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" 00\n"
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);
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CHECK_TRACE_CONTENTS(
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"error: duplicate global 'x'\n"
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);
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}
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void test_global_variable_disp32_with_modrm() {
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run(
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"== code 0x1\n"
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"8b/copy 0/mod/indirect 5/rm32/.disp32 2/r32/EDX x/disp32\n"
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"== data 0x2000\n"
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"x:\n"
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" 00 00 00 00\n"
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);
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CHECK_TRACE_COUNT("error", 0);
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}
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void test_global_variable_disp32_with_call() {
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transform(
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"== code 0x1\n"
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"foo:\n"
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" e8/call bar/disp32\n"
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"bar:\n"
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);
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CHECK_TRACE_COUNT("error", 0);
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}
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string to_full_string(const line& in) {
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ostringstream out;
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for (int i = 0; i < SIZE(in.words); ++i) {
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if (i > 0) out << ' ';
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out << in.words.at(i).data;
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for (int j = 0; j < SIZE(in.words.at(i).metadata); ++j)
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out << '/' << in.words.at(i).metadata.at(j);
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}
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return out.str();
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}
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