src/disassembler/llvm/LLVMDisassembler.cxx

   1 #include "disassembler/llvm/LLVMDisassembler.hxx"
   2 #include "disassembler/llvm/LLVMBasicBlock.hxx"
   3 #include "disassembler/llvm/LLVMFunction.hxx"
   4
   5 #include <stack>
   6 #include <algorithm>
   7
   8 using namespace llvm;
   9 using namespace llvm::object;
  10 using std::error_code;
  11
  12 /*
  13  * TODO: fallback code falls die Datei kein ELF/PE/COFF/MacO/.. binary
  14  * ist sondern z.B. einfach nur Instruktionen oder ein Bootsektor oder
  15  * foo
  16  */
  17 LLVMDisassembler::LLVMDisassembler(const std::string& filename)
  18     : Disassembler(filename)
  19     , logger(log4cxx::Logger::getLogger("LLVMDisassembler"))
  20     , triple("unknown-unknown-unknown")
  21 {
  22     LOG4CXX_DEBUG(logger, "Handling file" << filename);
  23     auto result = createBinary(filename);
  24
  25     error_code ec;
  26     if ((ec = result.getError())) {
  27         LOG4CXX_ERROR(logger, "Failed to load Binary" << ec.message());
  28         binary = NULL;
  29         return;
  30     }
  31
  32     binary.reset(result.get());
  33
  34     o = dyn_cast<ObjectFile>(binary.get());
  35
  36     triple.setArch(Triple::ArchType(o->getArch()));
  37     std::string tripleName(triple.getTriple());
  38
  39     LOG4CXX_INFO(logger, "Architecture " << tripleName);
  40
  41
  42     std::string es;
  43     target = TargetRegistry::lookupTarget("", triple, es);
  44     if (!target) {
  45         LOG4CXX_ERROR(logger, es);
  46         return;
  47     }
  48
  49     LOG4CXX_INFO(logger, "Target " << target->getName());
  50
  51     MRI.reset(target->createMCRegInfo(tripleName));
  52     if (!MRI) {
  53         LOG4CXX_ERROR(logger, "no register info for target " << tripleName);
  54         return;
  55     }
  56
  57     // Set up disassembler.
  58     AsmInfo.reset(target->createMCAsmInfo(*MRI, tripleName));
  59     if (!AsmInfo) {
  60         LOG4CXX_ERROR(logger, "no assembly info for target " << tripleName);
  61         return;
  62     }
  63
  64     STI.reset(target->createMCSubtargetInfo(tripleName, "", ""));
  65     if (!STI) {
  66         LOG4CXX_ERROR(logger, "no subtarget info for target " << tripleName);
  67         return;
  68     }
  69
  70     MII.reset(target->createMCInstrInfo());
  71     if (!MII) {
  72         LOG4CXX_ERROR(logger, "no instruction info for target " << tripleName);
  73         return;
  74     }
  75
  76     MOFI.reset(new MCObjectFileInfo);
  77     MCContext Ctx(AsmInfo.get(), MRI.get(), MOFI.get());
  78
  79     DisAsm.reset(target->createMCDisassembler(*STI, Ctx));
  80     if (!DisAsm) {
  81         LOG4CXX_ERROR(logger, "no disassembler for target " << tripleName);
  82         return;
  83     }
  84     RelInfo.reset(
  85         target->createMCRelocationInfo(tripleName, Ctx));
  86     if (RelInfo) {
  87         Symzer.reset(
  88             MCObjectSymbolizer::createObjectSymbolizer(Ctx, std::move(RelInfo), o));
  89         if (Symzer)
  90             DisAsm->setSymbolizer(std::move(Symzer));
  91     }
  92     RelInfo.release();
  93     Symzer.release();
  94
  95     MIA.reset(target->createMCInstrAnalysis(MII.get()));
  96     if (!MIA) {
  97         LOG4CXX_ERROR(logger, "no instruction analysis for target " << tripleName);
  98         return;
  99     }
 100
 101     int AsmPrinterVariant = AsmInfo->getAssemblerDialect();
 102     IP.reset(target->createMCInstPrinter(AsmPrinterVariant, *AsmInfo, *MII, *MRI, *STI));
 103     if (!IP) {
 104         LOG4CXX_ERROR(logger, "no instruction printer for target " << tripleName);
 105         return;
 106     }
 107
 108     IP->setPrintImmHex(llvm::HexStyle::C);
 109     IP->setPrintImmHex(true);
 110
 111     std::unique_ptr<MCObjectDisassembler> OD(
 112         new MCObjectDisassembler(*o, *DisAsm, *MIA));
 113     Mod.reset(OD->buildModule(false));
 114
 115     readSymbols();
 116     readSections();
 117     disassemble();
 118 }
 119
 120 LLVMDisassembler::~LLVMDisassembler() {
 121     std::for_each(functions.begin(), functions.end(),
 122                   [](std::pair<uint64_t,LLVMFunction*> it) {
 123                       delete it.second;
 124                   });
 125     std::for_each(blocks.begin(), blocks.end(),
 126                   [](std::pair<uint64_t, LLVMBasicBlock*> it) {
 127                       delete it.second;
 128                   });
 129 }
 130
 131 Function* LLVMDisassembler::disassembleFunctionAt(uint64_t address, const std::string& name) {
 132     if (functions.find(address) != functions.end()) {
 133         return functions[address];
 134     }
 135
 136     LLVMFunction * function;
 137     if (name == "") {
 138         std::stringstream s;
 139         s << "<Unnamed 0x" << std::hex << address << ">";
 140         function = new LLVMFunction(s.str(), address);
 141     } else {
 142         function = new LLVMFunction(name, address);
 143     }
 144     functions.insert(std::make_pair(address, function));
 145
 146     disassembleFunction(function);
 147
 148     return function;
 149 }
 150
 151 void LLVMDisassembler::disassembleFunction(LLVMFunction* function) {
 152     std::stack<LLVMBasicBlock*> remaining_blocks;
 153     SectionRef text_section = sections[".text"];
 154     StringRef bytes;
 155     text_section.getContents(bytes);
 156     StringRefMemoryObject ref(bytes);
 157
 158     LOG4CXX_DEBUG(logger, "Handling function " << function->getName());
 159
 160     LLVMBasicBlock * block = new LLVMBasicBlock(function->getStartAddress(), this);
 161     remaining_blocks.push(block);
 162     blocks.insert(std::make_pair(block->getStartAddress(), block));
 163
 164     while (remaining_blocks.size()) {
 165         LLVMBasicBlock * current_block = remaining_blocks.top();
 166         remaining_blocks.pop();
 167
 168         LOG4CXX_DEBUG(logger, "Handling Block starting at " << std::hex << current_block->getStartAddress());
 169
 170         uint64_t inst_size;
 171         uint64_t base_address;
 172         text_section.getAddress(base_address);
 173         uint64_t current_address = current_block->getStartAddress() - base_address;
 174         while(true) {
 175             MCInst inst;
 176             std::string buf;
 177             llvm::raw_string_ostream s(buf);
 178
 179             if(llvm::MCDisassembler::Success ==
 180                DisAsm->getInstruction(inst, inst_size, ref, current_address, nulls(), nulls())) {
 181                 uint64_t jmptarget;
 182
 183                 if (MIA->evaluateBranch(inst, current_address, inst_size, jmptarget)) {
 184                     jmptarget += base_address;
 185                     if (!MIA->isIndirectBranch(inst)) {
 186                         if (MIA->isCall(inst)) {
 187                             if (functions.find(jmptarget) == functions.end()) {
 188                                 disassembleFunctionAt(jmptarget);
 189                             }
 190                         } else {
 191                             current_block->setNextBlock(0, jmptarget);
 192                             if (blocks.find(jmptarget) == blocks.end()) {
 193                                 LLVMBasicBlock * block = new LLVMBasicBlock(jmptarget, this);
 194                                 blocks.insert(std::make_pair(block->getStartAddress(), block));
 195                                 remaining_blocks.push(block);
 196                             }
 197                             if (MIA->isConditionalBranch(inst)) {
 198                                 jmptarget = base_address + current_address + inst_size;
 199                                 current_block->setNextBlock(1, jmptarget);
 200                                 if (blocks.find(jmptarget) == blocks.end()) {
 201                                     LLVMBasicBlock * block = new LLVMBasicBlock(jmptarget, this);
 202                                     blocks.insert(std::make_pair(block->getStartAddress(), block));
 203                                     remaining_blocks.push(block);
 204                                 }
 205                             }
 206                         }
 207                     }
 208                 }
 209             } else {
 210                 inst_size = 0;
 211             }
 212
 213
 214             if (inst_size == 0 || MIA->isTerminator(inst) || MIA->isBranch(inst)) {
 215                 current_block->setEndAddress(current_address + base_address + inst_size);
 216                 LOG4CXX_DEBUG(logger, "Finished Block at " << std::hex <<
 217                               current_block->getEndAddress());
 218                 break;
 219             }
 220             current_address += inst_size;
 221         }
 222     }
 223     LOG4CXX_DEBUG(logger, "Finished function " << function->getName());
 224 }
 225
 226 void LLVMDisassembler::disassemble() {
 227     SectionRef text_section = sections[".text"];
 228     std::vector<LLVMFunction*> remaining_functions;
 229
 230     // Assume all function symbols actually start a real function
 231     for (auto x = symbols.begin(); x != symbols.end(); ++x) {
 232         uint64_t result;
 233         bool contains;
 234         SymbolRef::Type symbol_type;
 235
 236
 237         if (text_section.containsSymbol(x->second, contains) || !contains)
 238             continue;
 239
 240         if (x->second.getType(symbol_type)
 241             || SymbolRef::ST_Function != symbol_type)
 242             continue;
 243
 244         if (!x->second.getAddress(result)) {
 245             LLVMFunction * fun = new LLVMFunction(x->first, result);
 246             remaining_functions.push_back(fun);
 247             functions.insert(std::make_pair(result, fun));
 248             LOG4CXX_DEBUG(logger, "Disasembling " << x->first);
 249         }
 250     }
 251
 252     for (LLVMFunction* function : remaining_functions) {
 253         disassembleFunction(function);
 254     }
 255
 256     if (binary->isELF()) {
 257         bool is64bit = (binary->getData()[4] == 0x02);
 258
 259         uint64_t entry(0);
 260         for (int i(0); i < (is64bit? 8 : 4); ++i) {
 261             if (binary->isLittleEndian()) {
 262                 entry |= (unsigned int)((unsigned char)binary->getData()[0x18 + i]) << 8*i;
 263             } else {
 264                 entry = entry << 8;
 265                 entry |= (unsigned char)binary->getData()[0x18 + i];
 266             }
 267         }
 268         LOG4CXX_DEBUG(logger, "Adding entry at: " << std::hex << entry);
 269         std::stringstream s;
 270         s << "<_start 0x" << std::hex << entry << ">";
 271
 272         disassembleFunctionAt(entry, s.str());
 273     }
 274
 275     if (functions.empty()) {
 276         uint64_t text_entry;
 277         text_section.getAddress(text_entry);
 278         LOG4CXX_INFO(logger, "No Symbols found, starting at the beginning of the text segment");
 279         disassembleFunctionAt(text_entry);
 280     }
 281
 282     splitBlocks();
 283 }
 284
 285 void LLVMDisassembler::splitBlocks() {
 286     SectionRef text_section = sections[".text"];
 287     StringRef bytes;
 288     text_section.getContents(bytes);
 289     StringRefMemoryObject ref(bytes);
 290
 291     // Split blocks where jumps are going inside the block
 292     for (auto it = blocks.begin(); it != blocks.end(); ++it) {
 293         LLVMBasicBlock * current_block = it->second;
 294         uint64_t inst_size;
 295         uint64_t base_address;
 296         text_section.getAddress(base_address);
 297         uint64_t current_address = current_block->getStartAddress() - base_address;
 298         while(current_block->getEndAddress() - base_address > current_address) {
 299             MCInst inst;
 300             std::string buf;
 301             llvm::raw_string_ostream s(buf);
 302
 303             if(llvm::MCDisassembler::Success ==
 304                DisAsm->getInstruction(inst, inst_size, ref, current_address, nulls(), nulls())) {
 305                 auto other = blocks.find(current_address + inst_size + base_address);
 306
 307                 if (other != blocks.end()) {
 308                     uint64_t endaddress = current_address + inst_size + base_address;
 309                     if (endaddress != current_block->getEndAddress()) {
 310                         LOG4CXX_DEBUG(logger, "Shortening block starting at "
 311                                       << std::hex
 312                                       << current_block->getStartAddress()
 313                                       << " now ending at "
 314                                       << other->first);
 315                         current_block->setEndAddress(endaddress);
 316                         current_block->setNextBlock(0, other->first);
 317                         current_block->setNextBlock(1, 0);
 318                     }
 319                 }
 320             } else {
 321                 inst_size = 1;
 322             }
 323             current_address += inst_size;
 324         }
 325     }
 326 }
 327
 328 void LLVMDisassembler::readSymbols() {
 329     error_code ec;
 330     symbol_iterator si(o->symbol_begin()), se(o->symbol_end());
 331     for (; si != se; ++si) {
 332         StringRef name;
 333         if ((ec = si->getName(name))) {
 334             LOG4CXX_ERROR(logger, ec.message());
 335             break;
 336         }
 337         LOG4CXX_DEBUG(logger, "Added symbol " << name.str());
 338         symbols.insert(make_pair(name.str(), *si));
 339     }
 340 }
 341
 342 void LLVMDisassembler::readSections() {
 343     error_code ec;
 344     section_iterator i(o->section_begin()), e(o->section_end());
 345     for (; i != e; ++i) {
 346         StringRef name;
 347         if ((ec = i->getName(name))) {
 348             LOG4CXX_ERROR(logger, ec.message());
 349             break;
 350         }
 351         LOG4CXX_DEBUG(logger, "Added section " << name.str());
 352         sections.insert(make_pair(name.str(), *i));
 353     }
 354
 355 }
 356
 357 void LLVMDisassembler::forEachFunction(std::function<void (uint64_t, Function*)> callback) {
 358     std::for_each(functions.begin(), functions.end(),
 359                   [&](std::pair<uint64_t, LLVMFunction*> x) {
 360                       callback(x.first, x.second);
 361                   });
 362 }
 363
 364 void LLVMDisassembler::printEachInstruction(uint64_t start, uint64_t end,
 365                                                                                         std::function<void (uint8_t*, size_t, const std::string&)> fun) {
 366     SectionRef text_section = sections[".text"];
 367     uint64_t base_address;
 368     text_section.getAddress(base_address);
 369     uint64_t current_address = start - base_address;
 370
 371     StringRef bytes;
 372     text_section.getContents(bytes);
 373     StringRefMemoryObject ref(bytes);
 374
 375     while (current_address < end - base_address) {
 376         uint64_t inst_size;
 377         MCInst inst;
 378                 std::string buf;
 379                 llvm::raw_string_ostream s(buf);
 380
 381         if(llvm::MCDisassembler::Success ==
 382            DisAsm->getInstruction(inst, inst_size, ref, current_address, nulls(), nulls())) {
 383
 384             uint8_t bytes[inst_size+2];
 385             ref.readBytes(current_address, inst_size, bytes);
 386
 387                         uint64_t jmptarget;
 388                         if (MIA->evaluateBranch(inst, current_address, inst_size, jmptarget)) {
 389                                 std::stringstream stream;
 390                                 stream << std::hex << (base_address + jmptarget);
 391                                 IP->printInst(&inst, s, stream.str());
 392                         } else
 393                                 IP->printInst(&inst, s, "");
 394
 395                         fun(bytes, inst_size, s.str());
 396         } else {
 397                         LOG4CXX_WARN(logger, "Invalid byte at" << std::hex << current_address + base_address);
 398                         fun(NULL, 0, "Invalid Byte");
 399                         inst_size = 1;
 400                 }
 401
 402                 current_address += inst_size;
 403     }
 404 }