diff options
| -rw-r--r-- | subx/022check_instruction.cc | 1 | ||||
| -rw-r--r-- | subx/026labels.cc | 96 |
2 files changed, 97 insertions, 0 deletions
diff --git a/subx/022check_instruction.cc b/subx/022check_instruction.cc index c4b169ff..860921ae 100644 --- a/subx/022check_instruction.cc +++ b/subx/022check_instruction.cc @@ -266,6 +266,7 @@ void init_permitted_operands() { :(code) void check_operands(const line& inst, const word& op) { + if (!is_hex_byte(op)) return; uint8_t expected_bitvector = get(Permitted_operands, op.data); if (HAS(expected_bitvector, MODRM)) check_operands_modrm(inst, op); diff --git a/subx/026labels.cc b/subx/026labels.cc new file mode 100644 index 00000000..ece513aa --- /dev/null +++ b/subx/026labels.cc @@ -0,0 +1,96 @@ +//: Labels are defined by ending names with a ':'. This layer will compute +//: addresses for labels, and compute the offset to in jump instructions using +//: them. + +:(scenarios transform) +:(scenario map_label) +== 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 +loop: + 05 0x0d0c0b0a/imm32 # add to EAX ++label: label 'loop' is at address 1 + +:(before "End One-time Setup") +Transform.push_back(replace_labels_with_addresses); + +:(code) +void replace_labels_with_addresses(program& p) { + if (p.segments.empty()) return; + segment& code = p.segments.at(0); + map<string, uint32_t> address; + compute_addresses_for_labels(code, address); + if (trace_contains_errors()) return; + drop_labels(code); + if (trace_contains_errors()) return; + replace_labels_with_addresses(code, address); +} + +void compute_addresses_for_labels(const segment& code, map<string, uint32_t> address) { + int current_byte = 0; + for (int i = 0; i < SIZE(code.lines); ++i) { + const line& inst = code.lines.at(i); + for (int j = 0; j < SIZE(inst.words); ++j) { + const word& curr = inst.words.at(j); + // hack: if we have any operand metadata left after previous transforms, + // deduce its size + // Maybe we should just move this transform to before instruction + // packing, and deduce the size of *all* operands. But then we'll also + // have to deal with bitfields. + if (has_metadata(curr, "disp32") || has_metadata(curr, "imm32")) { + if (*curr.data.rbegin() == ':') + raise << "'" << to_string(inst) << "': don't use ':' when jumping to labels\n" << end(); + current_byte += 4; + } + // automatically handle /disp8 and /imm8 here + else if (*curr.data.rbegin() != ':') { + ++current_byte; + } + else { + if (contains_any_operand_metadata(curr)) + raise << "'" << to_string(inst) << "': mixing label definition with ':' in operand\n" << end(); + if (j == 0) { + string label = curr.data.substr(0, SIZE(curr.data)-1); + put(address, label, current_byte); + trace(99, "label") << "label '" << label << "' is at address " << (current_byte+code.start) << end(); + // no modifying current_byte; label definitions won't be in the final binary + } + else { + raise << "'" << to_string(inst) << "': labels can only be the first word in a line.\n" << end(); + } + } + } + } +} + +void drop_labels(segment& code) { + for (int i = 0; i < SIZE(code.lines); ++i) { + line& inst = code.lines.at(i); + remove_if(inst.words.begin(), inst.words.end(), is_label); + } +} + +bool is_label(const word& w) { + return *w.data.rbegin() == ':'; +} + +void replace_labels_with_addresses(const segment& code, map<string, uint32_t> address) { +} + +//: Label definitions must be the first word on a line. No jumping inside +//: instructions. +//: They should also be the only word on a line. +//: However, you can absolutely have multiple labels map to the same address, +//: as long as they're on separate lines. + +:(scenario multiple_labels_at) +== 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 +loop: +loop2: + 05 0x0d0c0b0a/imm32 # add to EAX ++label: label 'loop' is at address 1 ++label: label 'loop2' is at address 1 |