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| 1 // Copyright (c) 2009 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "third_party/courgette/disassembler.h" | |
| 6 | |
| 7 #include <algorithm> | |
| 8 #include <iostream> | |
| 9 #include <string> | |
| 10 #include <vector> | |
| 11 | |
| 12 #include "base/basictypes.h" | |
| 13 #include "base/logging.h" | |
| 14 | |
| 15 #include "third_party/courgette/assembly_program.h" | |
| 16 #include "third_party/courgette/courgette.h" | |
| 17 #include "third_party/courgette/encoded_program.h" | |
| 18 #include "third_party/courgette/image_info.h" | |
| 19 | |
| 20 // COURGETTE_HISTOGRAM_TARGETS prints out a histogram of how frequently | |
| 21 // different target addresses are referenced. Purely for debugging. | |
| 22 #define COURGETTE_HISTOGRAM_TARGETS 0 | |
| 23 | |
| 24 namespace courgette { | |
| 25 | |
| 26 class DisassemblerWin32X86 : public Disassembler { | |
| 27 public: | |
| 28 explicit DisassemblerWin32X86(PEInfo* pe_info) | |
| 29 : pe_info_(pe_info), | |
| 30 incomplete_disassembly_(false) { | |
| 31 } | |
| 32 | |
| 33 virtual bool Disassemble(AssemblyProgram* target); | |
| 34 | |
| 35 virtual void Destroy() { delete this; } | |
| 36 | |
| 37 protected: | |
| 38 PEInfo& pe_info() { return *pe_info_; } | |
| 39 | |
| 40 void ParseFile(AssemblyProgram* target); | |
| 41 bool ParseAbs32Relocs(); | |
| 42 void ParseRel32RelocsFromSections(); | |
| 43 void ParseRel32RelocsFromSection(const Section* section); | |
| 44 | |
| 45 void ParseNonSectionFileRegion(uint32 start_file_offset, | |
| 46 uint32 end_file_offset, | |
| 47 AssemblyProgram* program); | |
| 48 void ParseFileRegion(const Section* section, | |
| 49 uint32 start_file_offset, uint32 end_file_offset, | |
| 50 AssemblyProgram* program); | |
| 51 | |
| 52 #if COURGETTE_HISTOGRAM_TARGETS | |
| 53 void HistogramTargets(const char* kind, const std::map<RVA, int>& map); | |
| 54 #endif | |
| 55 | |
| 56 PEInfo* pe_info_; | |
| 57 bool incomplete_disassembly_; // 'true' if can leave out 'uninteresting' bits | |
| 58 | |
| 59 std::vector<RVA> abs32_locations_; | |
| 60 std::vector<RVA> rel32_locations_; | |
| 61 | |
| 62 #if COURGETTE_HISTOGRAM_TARGETS | |
| 63 std::map<RVA, int> abs32_target_rvas_; | |
| 64 std::map<RVA, int> rel32_target_rvas_; | |
| 65 #endif | |
| 66 }; | |
| 67 | |
| 68 bool DisassemblerWin32X86::Disassemble(AssemblyProgram* target) { | |
| 69 if (!pe_info().ok()) | |
| 70 return false; | |
| 71 | |
| 72 target->set_image_base(pe_info().image_base()); | |
| 73 | |
| 74 if (!ParseAbs32Relocs()) | |
| 75 return false; | |
| 76 | |
| 77 ParseRel32RelocsFromSections(); | |
| 78 | |
| 79 ParseFile(target); | |
| 80 | |
| 81 target->DefaultAssignIndexes(); | |
| 82 return true; | |
| 83 } | |
| 84 | |
| 85 static uint32 Read32LittleEndian(const void* address) { | |
| 86 return *reinterpret_cast<const uint32*>(address); | |
| 87 } | |
| 88 | |
| 89 bool DisassemblerWin32X86::ParseAbs32Relocs() { | |
| 90 abs32_locations_.clear(); | |
| 91 if (!pe_info().ParseRelocs(&abs32_locations_)) | |
| 92 return false; | |
| 93 | |
| 94 std::sort(abs32_locations_.begin(), abs32_locations_.end()); | |
| 95 | |
| 96 #if COURGETTE_HISTOGRAM_TARGETS | |
| 97 for (size_t i = 0; i < abs32_locations_.size(); ++i) { | |
| 98 RVA rva = abs32_locations_[i]; | |
| 99 // The 4 bytes at the relocation are a reference to some address. | |
| 100 uint32 target_address = Read32LittleEndian(pe_info().RVAToPointer(rva)); | |
| 101 ++abs32_target_rvas_[target_address - pe_info().image_base()]; | |
| 102 } | |
| 103 #endif | |
| 104 return true; | |
| 105 } | |
| 106 | |
| 107 void DisassemblerWin32X86::ParseRel32RelocsFromSections() { | |
| 108 uint32 file_offset = 0; | |
| 109 while (file_offset < pe_info().length()) { | |
| 110 const Section* section = pe_info().FindNextSection(file_offset); | |
| 111 if (section == NULL) | |
| 112 break; | |
| 113 if (file_offset < section->file_offset_of_raw_data) | |
| 114 file_offset = section->file_offset_of_raw_data; | |
| 115 ParseRel32RelocsFromSection(section); | |
| 116 file_offset += section->size_of_raw_data; | |
| 117 } | |
| 118 std::sort(rel32_locations_.begin(), rel32_locations_.end()); | |
| 119 | |
| 120 #if COURGETTE_HISTOGRAM_TARGETS | |
| 121 LOG(INFO) << "abs32_locations_ " << abs32_locations_.size(); | |
| 122 LOG(INFO) << "rel32_locations_ " << rel32_locations_.size(); | |
| 123 LOG(INFO) << "abs32_target_rvas_ " << abs32_target_rvas_.size(); | |
| 124 LOG(INFO) << "rel32_target_rvas_ " << rel32_target_rvas_.size(); | |
| 125 | |
| 126 int common = 0; | |
| 127 std::map<RVA, int>::iterator abs32_iter = abs32_target_rvas_.begin(); | |
| 128 std::map<RVA, int>::iterator rel32_iter = rel32_target_rvas_.begin(); | |
| 129 while (abs32_iter != abs32_target_rvas_.end() && | |
| 130 rel32_iter != rel32_target_rvas_.end()) { | |
| 131 if (abs32_iter->first < rel32_iter->first) | |
| 132 ++abs32_iter; | |
| 133 else if (rel32_iter->first < abs32_iter->first) | |
| 134 ++rel32_iter; | |
| 135 else { | |
| 136 ++common; | |
| 137 ++abs32_iter; | |
| 138 ++rel32_iter; | |
| 139 } | |
| 140 } | |
| 141 LOG(INFO) << "common " << common; | |
| 142 #endif | |
| 143 } | |
| 144 | |
| 145 void DisassemblerWin32X86::ParseRel32RelocsFromSection(const Section* section) { | |
| 146 // TODO(sra): use characteristic. | |
| 147 bool isCode = strcmp(section->name, ".text") == 0; | |
| 148 if (!isCode) | |
| 149 return; | |
| 150 | |
| 151 uint32 start_file_offset = section->file_offset_of_raw_data; | |
| 152 uint32 end_file_offset = start_file_offset + section->size_of_raw_data; | |
| 153 RVA relocs_start_rva = pe_info().base_relocation_table().address_; | |
| 154 | |
| 155 const uint8* start_pointer = pe_info().FileOffsetToPointer(start_file_offset); | |
| 156 const uint8* end_pointer = pe_info().FileOffsetToPointer(end_file_offset); | |
| 157 | |
| 158 RVA start_rva = pe_info().FileOffsetToRVA(start_file_offset); | |
| 159 RVA end_rva = start_rva + section->virtual_size; | |
| 160 | |
| 161 // Quick way to convert from Pointer to RVA within a single Section is to | |
| 162 // subtract 'pointer_to_rva'. | |
| 163 const uint8* const adjust_pointer_to_rva = start_pointer - start_rva; | |
| 164 | |
| 165 std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin(); | |
| 166 | |
| 167 // Find the rel32 relocations. | |
| 168 const uint8* p = start_pointer; | |
| 169 while (p < end_pointer) { | |
| 170 RVA current_rva = p - adjust_pointer_to_rva; | |
| 171 if (current_rva == relocs_start_rva) { | |
| 172 uint32 relocs_size = pe_info().base_relocation_table().size_; | |
| 173 if (relocs_size) { | |
| 174 p += relocs_size; | |
| 175 continue; | |
| 176 } | |
| 177 } | |
| 178 | |
| 179 //while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva) | |
| 180 // ++abs32_pos; | |
| 181 | |
| 182 // Heuristic discovery of rel32 locations in instruction stream: are the | |
| 183 // next few bytes the start of an instruction containing a rel32 | |
| 184 // addressing mode? | |
| 185 const uint8* rel32 = NULL; | |
| 186 | |
| 187 if (p + 5 < end_pointer) { | |
| 188 if (*p == 0xE8 || *p == 0xE9) { // jmp rel32 and call rel32 | |
| 189 rel32 = p + 1; | |
| 190 } | |
| 191 } | |
| 192 if (p + 6 < end_pointer) { | |
| 193 if (*p == 0x0F && (*(p+1) & 0xF0) == 0x80) { // Jcc long form | |
| 194 if (p[1] != 0x8A && p[1] != 0x8B) // JPE/JPO unlikely | |
| 195 rel32 = p + 2; | |
| 196 } | |
| 197 } | |
| 198 if (rel32) { | |
| 199 RVA rel32_rva = rel32 - adjust_pointer_to_rva; | |
| 200 | |
| 201 // Is there an abs32 reloc overlapping the candidate? | |
| 202 while (abs32_pos != abs32_locations_.end() && *abs32_pos < rel32_rva - 3) | |
| 203 ++abs32_pos; | |
| 204 // Now: (*abs32_pos > rel32_rva - 4) i.e. the lowest addressed 4-byte | |
| 205 // region that could overlap rel32_rva. | |
| 206 if (abs32_pos != abs32_locations_.end()) { | |
| 207 if (*abs32_pos < rel32_rva + 4) { | |
| 208 // Beginning of abs32 reloc is before end of rel32 reloc so they | |
| 209 // overlap. Skip four bytes past the abs32 reloc. | |
| 210 p += (*abs32_pos + 4) - current_rva; | |
| 211 continue; | |
| 212 } | |
| 213 } | |
| 214 | |
| 215 RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32); | |
| 216 // To be valid, rel32 target must be within image, and within this | |
| 217 // section. | |
| 218 if (pe_info().IsValidRVA(target_rva) && | |
| 219 start_rva <= target_rva && target_rva < end_rva) { | |
| 220 rel32_locations_.push_back(rel32_rva); | |
| 221 #if COURGETTE_HISTOGRAM_TARGETS | |
| 222 ++rel32_target_rvas_[target_rva]; | |
| 223 #endif | |
| 224 p += 4; | |
| 225 continue; | |
| 226 } | |
| 227 } | |
| 228 p += 1; | |
| 229 } | |
| 230 } | |
| 231 | |
| 232 void DisassemblerWin32X86::ParseFile(AssemblyProgram* program) { | |
| 233 // Walk all the bytes in the file, whether or not in a section. | |
| 234 uint32 file_offset = 0; | |
| 235 while (file_offset < pe_info().length()) { | |
| 236 const Section* section = pe_info().FindNextSection(file_offset); | |
| 237 if (section == NULL) { | |
| 238 // No more sections. There should not be extra stuff following last | |
| 239 // section. | |
| 240 // ParseNonSectionFileRegion(file_offset, pe_info().length(), program); | |
| 241 break; | |
| 242 } | |
| 243 if (file_offset < section->file_offset_of_raw_data) { | |
| 244 uint32 section_start_offset = section->file_offset_of_raw_data; | |
| 245 ParseNonSectionFileRegion(file_offset, section_start_offset, program); | |
| 246 file_offset = section_start_offset; | |
| 247 } | |
| 248 uint32 end = file_offset + section->size_of_raw_data; | |
| 249 ParseFileRegion(section, file_offset, end, program); | |
| 250 file_offset = end; | |
| 251 } | |
| 252 | |
| 253 #if COURGETTE_HISTOGRAM_TARGETS | |
| 254 HistogramTargets("abs32 relocs", abs32_target_rvas_); | |
| 255 HistogramTargets("rel32 relocs", rel32_target_rvas_); | |
| 256 #endif | |
| 257 } | |
| 258 | |
| 259 void DisassemblerWin32X86::ParseNonSectionFileRegion( | |
| 260 uint32 start_file_offset, | |
| 261 uint32 end_file_offset, | |
| 262 AssemblyProgram* program) { | |
| 263 if (incomplete_disassembly_) | |
| 264 return; | |
| 265 | |
| 266 const uint8* start = pe_info().FileOffsetToPointer(start_file_offset); | |
| 267 const uint8* end = pe_info().FileOffsetToPointer(end_file_offset); | |
| 268 | |
| 269 const uint8* p = start; | |
| 270 | |
| 271 while (p < end) { | |
| 272 program->EmitByteInstruction(*p); | |
| 273 ++p; | |
| 274 } | |
| 275 } | |
| 276 | |
| 277 void DisassemblerWin32X86::ParseFileRegion( | |
| 278 const Section* section, | |
| 279 uint32 start_file_offset, uint32 end_file_offset, | |
| 280 AssemblyProgram* program) { | |
| 281 RVA relocs_start_rva = pe_info().base_relocation_table().address_; | |
| 282 | |
| 283 const uint8* start_pointer = pe_info().FileOffsetToPointer(start_file_offset); | |
| 284 const uint8* end_pointer = pe_info().FileOffsetToPointer(end_file_offset); | |
| 285 | |
| 286 RVA start_rva = pe_info().FileOffsetToRVA(start_file_offset); | |
| 287 RVA end_rva = start_rva + section->virtual_size; | |
| 288 | |
| 289 // Quick way to convert from Pointer to RVA within a single Section is to | |
| 290 // subtract 'pointer_to_rva'. | |
| 291 const uint8* const adjust_pointer_to_rva = start_pointer - start_rva; | |
| 292 | |
| 293 std::vector<RVA>::iterator rel32_pos = rel32_locations_.begin(); | |
| 294 std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin(); | |
| 295 | |
| 296 program->EmitOriginInstruction(start_rva); | |
| 297 | |
| 298 const uint8* p = start_pointer; | |
| 299 | |
| 300 while (p < end_pointer) { | |
| 301 RVA current_rva = p - adjust_pointer_to_rva; | |
| 302 | |
| 303 // The base relocation table is usually in the .relocs section, but it could | |
| 304 // actually be anywhere. Make sure we skip it because we will regenerate it | |
| 305 // during assembly. | |
| 306 if (current_rva == relocs_start_rva) { | |
| 307 program->EmitMakeRelocsInstruction(); | |
| 308 uint32 relocs_size = pe_info().base_relocation_table().size_; | |
| 309 if (relocs_size) { | |
| 310 p += relocs_size; | |
| 311 continue; | |
| 312 } | |
| 313 } | |
| 314 | |
| 315 while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva) | |
| 316 ++abs32_pos; | |
| 317 | |
| 318 if (abs32_pos != abs32_locations_.end() && *abs32_pos == current_rva) { | |
| 319 uint32 target_address = Read32LittleEndian(p); | |
| 320 RVA target_rva = target_address - pe_info().image_base(); | |
| 321 // TODO(sra): target could be Label+offset. It is not clear how to guess | |
| 322 // which it might be. We assume offset==0. | |
| 323 program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)); | |
| 324 p += 4; | |
| 325 continue; | |
| 326 } | |
| 327 | |
| 328 while (rel32_pos != rel32_locations_.end() && *rel32_pos < current_rva) | |
| 329 ++rel32_pos; | |
| 330 | |
| 331 if (rel32_pos != rel32_locations_.end() && *rel32_pos == current_rva) { | |
| 332 RVA target_rva = current_rva + 4 + Read32LittleEndian(p); | |
| 333 program->EmitRel32(program->FindOrMakeRel32Label(target_rva)); | |
| 334 p += 4; | |
| 335 continue; | |
| 336 } | |
| 337 | |
| 338 if (incomplete_disassembly_) { | |
| 339 if ((abs32_pos == abs32_locations_.end() || end_rva <= *abs32_pos) && | |
| 340 (rel32_pos == rel32_locations_.end() || end_rva <= *rel32_pos) && | |
| 341 (end_rva <= relocs_start_rva || current_rva >= relocs_start_rva)) { | |
| 342 // No more relocs in this section, don't bother encoding bytes. | |
| 343 break; | |
| 344 } | |
| 345 } | |
| 346 | |
| 347 program->EmitByteInstruction(*p); | |
| 348 p += 1; | |
| 349 } | |
| 350 } | |
| 351 | |
| 352 #if COURGETTE_HISTOGRAM_TARGETS | |
| 353 // Histogram is printed to std::cout. It is purely for debugging the algorithm | |
| 354 // and is only enabled manually in 'exploration' builds. I don't want to add | |
| 355 // command-line configuration for this feature because this code has to be | |
| 356 // small, which means compiled-out. | |
| 357 void DisassemblerWin32X86::HistogramTargets(const char* kind, | |
| 358 const std::map<RVA, int>& map) { | |
| 359 int total = 0; | |
| 360 std::map<int, std::vector<RVA> > h; | |
| 361 for (std::map<RVA, int>::const_iterator p = map.begin(); | |
| 362 p != map.end(); | |
| 363 ++p) { | |
| 364 h[p->second].push_back(p->first); | |
| 365 total += p->second; | |
| 366 } | |
| 367 | |
| 368 std::cout << total << " " << kind << " to " | |
| 369 << map.size() << " unique targets" << std::endl; | |
| 370 | |
| 371 std::cout << "indegree: #targets-with-indegree (example)" << std::endl; | |
| 372 const int kFirstN = 15; | |
| 373 bool someSkipped = false; | |
| 374 int index = 0; | |
| 375 for (std::map<int, std::vector<RVA> >::reverse_iterator p = h.rbegin(); | |
| 376 p != h.rend(); | |
| 377 ++p) { | |
| 378 ++index; | |
| 379 if (index <= kFirstN || p->first <= 3) { | |
| 380 if (someSkipped) { | |
| 381 std::cout << "..." << std::endl; | |
| 382 } | |
| 383 size_t count = p->second.size(); | |
| 384 std::cout << std::dec << p->first << ": " << count; | |
| 385 if (count <= 2) { | |
| 386 for (size_t i = 0; i < count; ++i) | |
| 387 std::cout << " " << pe_info().DescribeRVA(p->second[i]); | |
| 388 } | |
| 389 std::cout << std::endl; | |
| 390 someSkipped = false; | |
| 391 } else { | |
| 392 someSkipped = true; | |
| 393 } | |
| 394 } | |
| 395 } | |
| 396 #endif // COURGETTE_HISTOGRAM_TARGETS | |
| 397 | |
| 398 Disassembler* Disassembler::MakeDisassemberWin32X86(PEInfo* pe_info) { | |
| 399 return new DisassemblerWin32X86(pe_info); | |
| 400 } | |
| 401 | |
| 402 //////////////////////////////////////////////////////////////////////////////// | |
| 403 | |
| 404 Status ParseWin32X86PE(const void* buffer, size_t length, | |
| 405 AssemblyProgram** output) { | |
| 406 *output = NULL; | |
| 407 | |
| 408 PEInfo* pe_info = new PEInfo(); | |
| 409 pe_info->Init(buffer, length); | |
| 410 | |
| 411 if (!pe_info->ParseHeader()) { | |
| 412 delete pe_info; | |
| 413 return C_INPUT_NOT_RECOGNIZED; | |
| 414 } | |
| 415 | |
| 416 Disassembler* disassembler = Disassembler::MakeDisassemberWin32X86(pe_info); | |
| 417 AssemblyProgram* program = new AssemblyProgram(); | |
| 418 | |
| 419 if (!disassembler->Disassemble(program)) { | |
| 420 delete program; | |
| 421 disassembler->Destroy(); | |
| 422 delete pe_info; | |
| 423 return C_DISASSEMBLY_FAILED; | |
| 424 } | |
| 425 | |
| 426 disassembler->Destroy(); | |
| 427 delete pe_info; | |
| 428 *output = program; | |
| 429 return C_OK; | |
| 430 } | |
| 431 | |
| 432 void DeleteAssemblyProgram(AssemblyProgram* program) { | |
| 433 delete program; | |
| 434 } | |
| 435 | |
| 436 } // namespace courgette | |
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