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244 lines
9.1 KiB
244 lines
9.1 KiB
#include <vmutils.hpp>
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namespace vm::utils {
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void print(const zydis_decoded_instr_t& instr) {
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char buffer[256];
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ZydisFormatterFormatInstruction(vm::utils::g_formatter.get(), &instr, buffer,
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sizeof(buffer), 0u);
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std::puts(buffer);
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}
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void print(zydis_rtn_t& routine) {
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char buffer[256];
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for (auto [instr, raw, addr] : routine) {
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ZydisFormatterFormatInstruction(vm::utils::g_formatter.get(), &instr,
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buffer, sizeof(buffer), addr);
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std::printf("> %p %s\n", addr, buffer);
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}
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}
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bool is_jmp(const zydis_decoded_instr_t& instr) {
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return instr.mnemonic >= ZYDIS_MNEMONIC_JB &&
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instr.mnemonic <= ZYDIS_MNEMONIC_JZ;
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}
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bool is_mov(const zydis_decoded_instr_t& instr) {
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return instr.mnemonic == ZYDIS_MNEMONIC_MOV ||
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instr.mnemonic == ZYDIS_MNEMONIC_MOVSX ||
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instr.mnemonic == ZYDIS_MNEMONIC_MOVZX;
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}
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bool flatten(zydis_rtn_t& routine,
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std::uintptr_t routine_addr,
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bool keep_jmps,
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std::uint32_t max_instrs,
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std::uintptr_t module_base) {
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zydis_decoded_instr_t instr;
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std::uint32_t instr_cnt = 0u;
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while (ZYAN_SUCCESS(ZydisDecoderDecodeBuffer(
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vm::utils::g_decoder.get(), reinterpret_cast<void*>(routine_addr), 0x1000,
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&instr))) {
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if (++instr_cnt > max_instrs)
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return false;
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// detect if we have already been at this instruction... if so that means
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// there is a loop and we are going to just return...
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if (std::find_if(routine.begin(), routine.end(),
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[&](const zydis_instr_t& zydis_instr) -> bool {
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return zydis_instr.addr == routine_addr;
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}) != routine.end())
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return true;
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std::vector<u8> raw_instr;
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raw_instr.insert(raw_instr.begin(), (u8*)routine_addr,
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(u8*)routine_addr + instr.length);
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if (is_jmp(instr) ||
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instr.mnemonic == ZYDIS_MNEMONIC_CALL &&
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instr.operands[0].type != ZYDIS_OPERAND_TYPE_REGISTER) {
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if (instr.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER) {
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routine.push_back({instr, raw_instr, routine_addr});
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return true;
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}
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if (keep_jmps)
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routine.push_back({instr, raw_instr, routine_addr});
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ZydisCalcAbsoluteAddress(&instr, &instr.operands[0], routine_addr,
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&routine_addr);
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} else if (instr.mnemonic == ZYDIS_MNEMONIC_RET) {
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routine.push_back({instr, raw_instr, routine_addr});
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return true;
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} else {
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routine.push_back({instr, raw_instr, routine_addr});
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routine_addr += instr.length;
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}
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// optional sanity checking...
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if (module_base && !vm::utils::scn::executable(module_base, routine_addr))
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return false;
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}
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return false;
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}
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void deobfuscate(zydis_rtn_t& routine) {
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static const auto _uses_reg = [](zydis_decoded_operand_t& op,
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zydis_reg_t reg) -> bool {
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switch (op.type) {
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case ZYDIS_OPERAND_TYPE_MEMORY: {
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return vm::utils::reg::compare(op.mem.base, reg) ||
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vm::utils::reg::compare(op.mem.index, reg);
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}
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case ZYDIS_OPERAND_TYPE_REGISTER: {
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return vm::utils::reg::compare(op.reg.value, reg);
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}
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default:
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break;
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}
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return false;
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};
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static const auto _reads = [](zydis_decoded_instr_t& instr,
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zydis_reg_t reg) -> bool {
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if (instr.operands[0].type == ZYDIS_OPERAND_TYPE_MEMORY &&
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vm::utils::reg::compare(instr.operands[0].mem.base, reg))
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return true;
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for (auto op_idx = 0u; op_idx < instr.operand_count; ++op_idx)
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if (instr.operands[op_idx].actions & ZYDIS_OPERAND_ACTION_READ &&
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_uses_reg(instr.operands[op_idx], reg))
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return true;
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return false;
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};
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static const auto _writes = [](zydis_decoded_instr_t& instr,
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zydis_reg_t reg) -> bool {
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for (auto op_idx = 0u; op_idx < instr.operand_count; ++op_idx)
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// if instruction writes to the specific register...
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if (instr.operands[op_idx].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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instr.operands[op_idx].actions & ZYDIS_OPERAND_ACTION_WRITE &&
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!(instr.operands[op_idx].actions & ZYDIS_OPERAND_ACTION_READ) &&
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vm::utils::reg::compare(instr.operands[op_idx].reg.value, reg))
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return true;
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return false;
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};
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std::uint32_t last_size = 0u;
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static const std::vector<ZydisMnemonic> blacklist = {
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ZYDIS_MNEMONIC_CLC, ZYDIS_MNEMONIC_BT, ZYDIS_MNEMONIC_TEST,
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ZYDIS_MNEMONIC_CMP, ZYDIS_MNEMONIC_CMC, ZYDIS_MNEMONIC_STC,
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ZYDIS_MNEMONIC_CMOVB, ZYDIS_MNEMONIC_CMOVBE, ZYDIS_MNEMONIC_CMOVL,
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ZYDIS_MNEMONIC_CMOVLE, ZYDIS_MNEMONIC_CMOVNB, ZYDIS_MNEMONIC_CMOVNBE,
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ZYDIS_MNEMONIC_CMOVNL, ZYDIS_MNEMONIC_CMOVNLE, ZYDIS_MNEMONIC_CMOVNO,
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ZYDIS_MNEMONIC_CMOVNP, ZYDIS_MNEMONIC_CMOVNS, ZYDIS_MNEMONIC_CMOVNZ,
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ZYDIS_MNEMONIC_CMOVO, ZYDIS_MNEMONIC_CMOVP, ZYDIS_MNEMONIC_CMOVS,
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ZYDIS_MNEMONIC_CMOVZ,
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};
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static const std::vector<ZydisMnemonic> whitelist = {
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ZYDIS_MNEMONIC_PUSH, ZYDIS_MNEMONIC_POP, ZYDIS_MNEMONIC_CALL,
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ZYDIS_MNEMONIC_DIV};
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do {
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last_size = routine.size();
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for (auto itr = routine.begin(); itr != routine.end(); ++itr) {
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if (std::find(whitelist.begin(), whitelist.end(), itr->instr.mnemonic) !=
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whitelist.end())
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continue;
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if (std::find(blacklist.begin(), blacklist.end(), itr->instr.mnemonic) !=
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blacklist.end()) {
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routine.erase(itr);
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break;
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}
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if (is_jmp(itr->instr)) {
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routine.erase(itr);
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break;
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}
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zydis_reg_t reg = ZYDIS_REGISTER_NONE;
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// look for operands with writes to a register...
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for (auto op_idx = 0u; op_idx < itr->instr.operand_count; ++op_idx)
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if (itr->instr.operands[op_idx].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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itr->instr.operands[op_idx].actions & ZYDIS_OPERAND_ACTION_WRITE)
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reg = vm::utils::reg::to64(itr->instr.operands[0].reg.value);
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// if this current instruction writes to a register, look ahead in the
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// instruction stream to see if it gets written too before it gets read...
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if (reg != ZYDIS_REGISTER_NONE) {
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// find the next place that this register is written too...
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auto write_result = std::find_if(itr + 1, routine.end(),
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[&](zydis_instr_t& instr) -> bool {
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return _writes(instr.instr, reg);
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});
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auto read_result = std::find_if(itr + 1, write_result,
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[&](zydis_instr_t& instr) -> bool {
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return _reads(instr.instr, reg);
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});
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// if there is neither a read or a write to this register in the
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// instruction stream then we are going to be safe and leave the
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// instruction in the stream...
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if (read_result == routine.end() && write_result == routine.end())
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continue;
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// if there is no read of the register before the next write... and
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// there is a known next write, then remove the instruction from the
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// stream...
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if (read_result == write_result && write_result != routine.end()) {
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// if the instruction reads and writes the same register than skip...
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if (_reads(read_result->instr, reg) &&
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_writes(read_result->instr, reg))
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continue;
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routine.erase(itr);
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break;
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}
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}
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}
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} while (last_size != routine.size());
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}
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namespace reg {
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zydis_reg_t to64(zydis_reg_t reg) {
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return ZydisRegisterGetLargestEnclosing(ZYDIS_MACHINE_MODE_LONG_64, reg);
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}
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bool compare(zydis_reg_t a, zydis_reg_t b) {
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return to64(a) == to64(b);
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}
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} // namespace reg
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namespace scn {
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bool read_only(std::uint64_t module_base, std::uint64_t ptr) {
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auto win_image = reinterpret_cast<win::image_t<>*>(module_base);
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auto section_count = win_image->get_file_header()->num_sections;
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auto sections = win_image->get_nt_headers()->get_sections();
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for (auto idx = 0u; idx < section_count; ++idx)
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if (ptr >= sections[idx].virtual_address + module_base &&
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ptr < sections[idx].virtual_address + sections[idx].virtual_size +
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module_base)
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return !(sections[idx].characteristics.mem_discardable) &&
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!(sections[idx].characteristics.mem_write);
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return false;
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}
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bool executable(std::uint64_t module_base, std::uint64_t ptr) {
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auto win_image = reinterpret_cast<win::image_t<>*>(module_base);
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auto section_count = win_image->get_file_header()->num_sections;
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auto sections = win_image->get_nt_headers()->get_sections();
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for (auto idx = 0u; idx < section_count; ++idx)
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if (ptr >= sections[idx].virtual_address + module_base &&
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ptr < sections[idx].virtual_address + sections[idx].virtual_size +
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module_base)
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return !(sections[idx].characteristics.mem_discardable) &&
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sections[idx].characteristics.mem_execute;
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return false;
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}
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} // namespace scn
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} // namespace vm::utils
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