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author | Kartik Agaram <vc@akkartik.com> | 2018-08-03 23:34:27 -0700 |
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committer | Kartik Agaram <vc@akkartik.com> | 2018-08-03 23:34:27 -0700 |
commit | 96a09ee9f9017294313cfb6daf04864ace78ba75 (patch) | |
tree | bd9f790fb6b594c04ce290632ba746b408eacf92 /subx/032pack_operands.cc | |
parent | 12adb3da8a8979c207b2e7fd17bdb05bacefeb44 (diff) | |
download | mu-96a09ee9f9017294313cfb6daf04864ace78ba75.tar.gz |
4468
Diffstat (limited to 'subx/032pack_operands.cc')
-rw-r--r-- | subx/032pack_operands.cc | 205 |
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) |