1 //===-- llvm/CodeGen/DIEHash.cpp - Dwarf Hashing Framework ----------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains support for DWARF4 hashing of DIEs. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "ByteStreamer.h" 15 #include "DIEHash.h" 16 #include "DIE.h" 17 #include "DwarfDebug.h" 18 #include "llvm/ADT/ArrayRef.h" 19 #include "llvm/ADT/StringRef.h" 20 #include "llvm/CodeGen/AsmPrinter.h" 21 #include "llvm/Support/Debug.h" 22 #include "llvm/Support/Dwarf.h" 23 #include "llvm/Support/Endian.h" 24 #include "llvm/Support/MD5.h" 25 #include "llvm/Support/raw_ostream.h" 26 27 using namespace llvm; 28 29 #define DEBUG_TYPE "dwarfdebug" 30 31 /// \brief Grabs the string in whichever attribute is passed in and returns 32 /// a reference to it. 33 static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr) { 34 const SmallVectorImpl<DIEValue *> &Values = Die.getValues(); 35 const DIEAbbrev &Abbrevs = Die.getAbbrev(); 36 37 // Iterate through all the attributes until we find the one we're 38 // looking for, if we can't find it return an empty string. 39 for (size_t i = 0; i < Values.size(); ++i) { 40 if (Abbrevs.getData()[i].getAttribute() == Attr) { 41 DIEValue *V = Values[i]; 42 assert(isa<DIEString>(V) && "String requested. Not a string."); 43 DIEString *S = cast<DIEString>(V); 44 return S->getString(); 45 } 46 } 47 return StringRef(""); 48 } 49 50 /// \brief Adds the string in \p Str to the hash. This also hashes 51 /// a trailing NULL with the string. 52 void DIEHash::addString(StringRef Str) { 53 DEBUG(dbgs() << "Adding string " << Str << " to hash.\n"); 54 Hash.update(Str); 55 Hash.update(makeArrayRef((uint8_t)'\0')); 56 } 57 58 // FIXME: The LEB128 routines are copied and only slightly modified out of 59 // LEB128.h. 60 61 /// \brief Adds the unsigned in \p Value to the hash encoded as a ULEB128. 62 void DIEHash::addULEB128(uint64_t Value) { 63 DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n"); 64 do { 65 uint8_t Byte = Value & 0x7f; 66 Value >>= 7; 67 if (Value != 0) 68 Byte |= 0x80; // Mark this byte to show that more bytes will follow. 69 Hash.update(Byte); 70 } while (Value != 0); 71 } 72 73 void DIEHash::addSLEB128(int64_t Value) { 74 DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n"); 75 bool More; 76 do { 77 uint8_t Byte = Value & 0x7f; 78 Value >>= 7; 79 More = !((((Value == 0) && ((Byte & 0x40) == 0)) || 80 ((Value == -1) && ((Byte & 0x40) != 0)))); 81 if (More) 82 Byte |= 0x80; // Mark this byte to show that more bytes will follow. 83 Hash.update(Byte); 84 } while (More); 85 } 86 87 /// \brief Including \p Parent adds the context of Parent to the hash.. 88 void DIEHash::addParentContext(const DIE &Parent) { 89 90 DEBUG(dbgs() << "Adding parent context to hash...\n"); 91 92 // [7.27.2] For each surrounding type or namespace beginning with the 93 // outermost such construct... 94 SmallVector<const DIE *, 1> Parents; 95 const DIE *Cur = &Parent; 96 while (Cur->getParent()) { 97 Parents.push_back(Cur); 98 Cur = Cur->getParent(); 99 } 100 assert(Cur->getTag() == dwarf::DW_TAG_compile_unit || 101 Cur->getTag() == dwarf::DW_TAG_type_unit); 102 103 // Reverse iterate over our list to go from the outermost construct to the 104 // innermost. 105 for (SmallVectorImpl<const DIE *>::reverse_iterator I = Parents.rbegin(), 106 E = Parents.rend(); 107 I != E; ++I) { 108 const DIE &Die = **I; 109 110 // ... Append the letter "C" to the sequence... 111 addULEB128('C'); 112 113 // ... Followed by the DWARF tag of the construct... 114 addULEB128(Die.getTag()); 115 116 // ... Then the name, taken from the DW_AT_name attribute. 117 StringRef Name = getDIEStringAttr(Die, dwarf::DW_AT_name); 118 DEBUG(dbgs() << "... adding context: " << Name << "\n"); 119 if (!Name.empty()) 120 addString(Name); 121 } 122 } 123 124 // Collect all of the attributes for a particular DIE in single structure. 125 void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) { 126 const SmallVectorImpl<DIEValue *> &Values = Die.getValues(); 127 const DIEAbbrev &Abbrevs = Die.getAbbrev(); 128 129 #define COLLECT_ATTR(NAME) \ 130 case dwarf::NAME: \ 131 Attrs.NAME.Val = Values[i]; \ 132 Attrs.NAME.Desc = &Abbrevs.getData()[i]; \ 133 break 134 135 for (size_t i = 0, e = Values.size(); i != e; ++i) { 136 DEBUG(dbgs() << "Attribute: " 137 << dwarf::AttributeString(Abbrevs.getData()[i].getAttribute()) 138 << " added.\n"); 139 switch (Abbrevs.getData()[i].getAttribute()) { 140 COLLECT_ATTR(DW_AT_name); 141 COLLECT_ATTR(DW_AT_accessibility); 142 COLLECT_ATTR(DW_AT_address_class); 143 COLLECT_ATTR(DW_AT_allocated); 144 COLLECT_ATTR(DW_AT_artificial); 145 COLLECT_ATTR(DW_AT_associated); 146 COLLECT_ATTR(DW_AT_binary_scale); 147 COLLECT_ATTR(DW_AT_bit_offset); 148 COLLECT_ATTR(DW_AT_bit_size); 149 COLLECT_ATTR(DW_AT_bit_stride); 150 COLLECT_ATTR(DW_AT_byte_size); 151 COLLECT_ATTR(DW_AT_byte_stride); 152 COLLECT_ATTR(DW_AT_const_expr); 153 COLLECT_ATTR(DW_AT_const_value); 154 COLLECT_ATTR(DW_AT_containing_type); 155 COLLECT_ATTR(DW_AT_count); 156 COLLECT_ATTR(DW_AT_data_bit_offset); 157 COLLECT_ATTR(DW_AT_data_location); 158 COLLECT_ATTR(DW_AT_data_member_location); 159 COLLECT_ATTR(DW_AT_decimal_scale); 160 COLLECT_ATTR(DW_AT_decimal_sign); 161 COLLECT_ATTR(DW_AT_default_value); 162 COLLECT_ATTR(DW_AT_digit_count); 163 COLLECT_ATTR(DW_AT_discr); 164 COLLECT_ATTR(DW_AT_discr_list); 165 COLLECT_ATTR(DW_AT_discr_value); 166 COLLECT_ATTR(DW_AT_encoding); 167 COLLECT_ATTR(DW_AT_enum_class); 168 COLLECT_ATTR(DW_AT_endianity); 169 COLLECT_ATTR(DW_AT_explicit); 170 COLLECT_ATTR(DW_AT_is_optional); 171 COLLECT_ATTR(DW_AT_location); 172 COLLECT_ATTR(DW_AT_lower_bound); 173 COLLECT_ATTR(DW_AT_mutable); 174 COLLECT_ATTR(DW_AT_ordering); 175 COLLECT_ATTR(DW_AT_picture_string); 176 COLLECT_ATTR(DW_AT_prototyped); 177 COLLECT_ATTR(DW_AT_small); 178 COLLECT_ATTR(DW_AT_segment); 179 COLLECT_ATTR(DW_AT_string_length); 180 COLLECT_ATTR(DW_AT_threads_scaled); 181 COLLECT_ATTR(DW_AT_upper_bound); 182 COLLECT_ATTR(DW_AT_use_location); 183 COLLECT_ATTR(DW_AT_use_UTF8); 184 COLLECT_ATTR(DW_AT_variable_parameter); 185 COLLECT_ATTR(DW_AT_virtuality); 186 COLLECT_ATTR(DW_AT_visibility); 187 COLLECT_ATTR(DW_AT_vtable_elem_location); 188 COLLECT_ATTR(DW_AT_type); 189 default: 190 break; 191 } 192 } 193 } 194 195 void DIEHash::hashShallowTypeReference(dwarf::Attribute Attribute, 196 const DIE &Entry, StringRef Name) { 197 // append the letter 'N' 198 addULEB128('N'); 199 200 // the DWARF attribute code (DW_AT_type or DW_AT_friend), 201 addULEB128(Attribute); 202 203 // the context of the tag, 204 if (const DIE *Parent = Entry.getParent()) 205 addParentContext(*Parent); 206 207 // the letter 'E', 208 addULEB128('E'); 209 210 // and the name of the type. 211 addString(Name); 212 213 // Currently DW_TAG_friends are not used by Clang, but if they do become so, 214 // here's the relevant spec text to implement: 215 // 216 // For DW_TAG_friend, if the referenced entry is the DW_TAG_subprogram, 217 // the context is omitted and the name to be used is the ABI-specific name 218 // of the subprogram (e.g., the mangled linker name). 219 } 220 221 void DIEHash::hashRepeatedTypeReference(dwarf::Attribute Attribute, 222 unsigned DieNumber) { 223 // a) If T is in the list of [previously hashed types], use the letter 224 // 'R' as the marker 225 addULEB128('R'); 226 227 addULEB128(Attribute); 228 229 // and use the unsigned LEB128 encoding of [the index of T in the 230 // list] as the attribute value; 231 addULEB128(DieNumber); 232 } 233 234 void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag, 235 const DIE &Entry) { 236 assert(Tag != dwarf::DW_TAG_friend && "No current LLVM clients emit friend " 237 "tags. Add support here when there's " 238 "a use case"); 239 // Step 5 240 // If the tag in Step 3 is one of [the below tags] 241 if ((Tag == dwarf::DW_TAG_pointer_type || 242 Tag == dwarf::DW_TAG_reference_type || 243 Tag == dwarf::DW_TAG_rvalue_reference_type || 244 Tag == dwarf::DW_TAG_ptr_to_member_type) && 245 // and the referenced type (via the [below attributes]) 246 // FIXME: This seems overly restrictive, and causes hash mismatches 247 // there's a decl/def difference in the containing type of a 248 // ptr_to_member_type, but it's what DWARF says, for some reason. 249 Attribute == dwarf::DW_AT_type) { 250 // ... has a DW_AT_name attribute, 251 StringRef Name = getDIEStringAttr(Entry, dwarf::DW_AT_name); 252 if (!Name.empty()) { 253 hashShallowTypeReference(Attribute, Entry, Name); 254 return; 255 } 256 } 257 258 unsigned &DieNumber = Numbering[&Entry]; 259 if (DieNumber) { 260 hashRepeatedTypeReference(Attribute, DieNumber); 261 return; 262 } 263 264 // otherwise, b) use the letter 'T' as a the marker, ... 265 addULEB128('T'); 266 267 addULEB128(Attribute); 268 269 // ... process the type T recursively by performing Steps 2 through 7, and 270 // use the result as the attribute value. 271 DieNumber = Numbering.size(); 272 computeHash(Entry); 273 } 274 275 // Hash all of the values in a block like set of values. This assumes that 276 // all of the data is going to be added as integers. 277 void DIEHash::hashBlockData(const SmallVectorImpl<DIEValue *> &Values) { 278 for (SmallVectorImpl<DIEValue *>::const_iterator I = Values.begin(), 279 E = Values.end(); 280 I != E; ++I) 281 Hash.update((uint64_t)cast<DIEInteger>(*I)->getValue()); 282 } 283 284 // Hash the contents of a loclistptr class. 285 void DIEHash::hashLocList(const DIELocList &LocList) { 286 HashingByteStreamer Streamer(*this); 287 DwarfDebug &DD = *AP->getDwarfDebug(); 288 for (const auto &Entry : 289 DD.getDebugLocEntries()[LocList.getValue()].List) 290 DD.emitDebugLocEntry(Streamer, Entry); 291 } 292 293 // Hash an individual attribute \param Attr based on the type of attribute and 294 // the form. 295 void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) { 296 const DIEValue *Value = Attr.Val; 297 const DIEAbbrevData *Desc = Attr.Desc; 298 dwarf::Attribute Attribute = Desc->getAttribute(); 299 300 // Other attribute values use the letter 'A' as the marker, and the value 301 // consists of the form code (encoded as an unsigned LEB128 value) followed by 302 // the encoding of the value according to the form code. To ensure 303 // reproducibility of the signature, the set of forms used in the signature 304 // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag, 305 // DW_FORM_string, and DW_FORM_block. 306 307 switch (Value->getType()) { 308 // 7.27 Step 3 309 // ... An attribute that refers to another type entry T is processed as 310 // follows: 311 case DIEValue::isEntry: 312 hashDIEEntry(Attribute, Tag, cast<DIEEntry>(Value)->getEntry()); 313 break; 314 case DIEValue::isInteger: { 315 addULEB128('A'); 316 addULEB128(Attribute); 317 switch (Desc->getForm()) { 318 case dwarf::DW_FORM_data1: 319 case dwarf::DW_FORM_data2: 320 case dwarf::DW_FORM_data4: 321 case dwarf::DW_FORM_data8: 322 case dwarf::DW_FORM_udata: 323 case dwarf::DW_FORM_sdata: 324 addULEB128(dwarf::DW_FORM_sdata); 325 addSLEB128((int64_t)cast<DIEInteger>(Value)->getValue()); 326 break; 327 // DW_FORM_flag_present is just flag with a value of one. We still give it a 328 // value so just use the value. 329 case dwarf::DW_FORM_flag_present: 330 case dwarf::DW_FORM_flag: 331 addULEB128(dwarf::DW_FORM_flag); 332 addULEB128((int64_t)cast<DIEInteger>(Value)->getValue()); 333 break; 334 default: 335 llvm_unreachable("Unknown integer form!"); 336 } 337 break; 338 } 339 case DIEValue::isString: 340 addULEB128('A'); 341 addULEB128(Attribute); 342 addULEB128(dwarf::DW_FORM_string); 343 addString(cast<DIEString>(Value)->getString()); 344 break; 345 case DIEValue::isBlock: 346 case DIEValue::isLoc: 347 case DIEValue::isLocList: 348 addULEB128('A'); 349 addULEB128(Attribute); 350 addULEB128(dwarf::DW_FORM_block); 351 if (isa<DIEBlock>(Value)) { 352 addULEB128(cast<DIEBlock>(Value)->ComputeSize(AP)); 353 hashBlockData(cast<DIEBlock>(Value)->getValues()); 354 } else if (isa<DIELoc>(Value)) { 355 addULEB128(cast<DIELoc>(Value)->ComputeSize(AP)); 356 hashBlockData(cast<DIELoc>(Value)->getValues()); 357 } else { 358 // We could add the block length, but that would take 359 // a bit of work and not add a lot of uniqueness 360 // to the hash in some way we could test. 361 hashLocList(*cast<DIELocList>(Value)); 362 } 363 break; 364 // FIXME: It's uncertain whether or not we should handle this at the moment. 365 case DIEValue::isExpr: 366 case DIEValue::isLabel: 367 case DIEValue::isDelta: 368 case DIEValue::isTypeSignature: 369 llvm_unreachable("Add support for additional value types."); 370 } 371 } 372 373 // Go through the attributes from \param Attrs in the order specified in 7.27.4 374 // and hash them. 375 void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) { 376 #define ADD_ATTR(ATTR) \ 377 { \ 378 if (ATTR.Val != 0) \ 379 hashAttribute(ATTR, Tag); \ 380 } 381 382 ADD_ATTR(Attrs.DW_AT_name); 383 ADD_ATTR(Attrs.DW_AT_accessibility); 384 ADD_ATTR(Attrs.DW_AT_address_class); 385 ADD_ATTR(Attrs.DW_AT_allocated); 386 ADD_ATTR(Attrs.DW_AT_artificial); 387 ADD_ATTR(Attrs.DW_AT_associated); 388 ADD_ATTR(Attrs.DW_AT_binary_scale); 389 ADD_ATTR(Attrs.DW_AT_bit_offset); 390 ADD_ATTR(Attrs.DW_AT_bit_size); 391 ADD_ATTR(Attrs.DW_AT_bit_stride); 392 ADD_ATTR(Attrs.DW_AT_byte_size); 393 ADD_ATTR(Attrs.DW_AT_byte_stride); 394 ADD_ATTR(Attrs.DW_AT_const_expr); 395 ADD_ATTR(Attrs.DW_AT_const_value); 396 ADD_ATTR(Attrs.DW_AT_containing_type); 397 ADD_ATTR(Attrs.DW_AT_count); 398 ADD_ATTR(Attrs.DW_AT_data_bit_offset); 399 ADD_ATTR(Attrs.DW_AT_data_location); 400 ADD_ATTR(Attrs.DW_AT_data_member_location); 401 ADD_ATTR(Attrs.DW_AT_decimal_scale); 402 ADD_ATTR(Attrs.DW_AT_decimal_sign); 403 ADD_ATTR(Attrs.DW_AT_default_value); 404 ADD_ATTR(Attrs.DW_AT_digit_count); 405 ADD_ATTR(Attrs.DW_AT_discr); 406 ADD_ATTR(Attrs.DW_AT_discr_list); 407 ADD_ATTR(Attrs.DW_AT_discr_value); 408 ADD_ATTR(Attrs.DW_AT_encoding); 409 ADD_ATTR(Attrs.DW_AT_enum_class); 410 ADD_ATTR(Attrs.DW_AT_endianity); 411 ADD_ATTR(Attrs.DW_AT_explicit); 412 ADD_ATTR(Attrs.DW_AT_is_optional); 413 ADD_ATTR(Attrs.DW_AT_location); 414 ADD_ATTR(Attrs.DW_AT_lower_bound); 415 ADD_ATTR(Attrs.DW_AT_mutable); 416 ADD_ATTR(Attrs.DW_AT_ordering); 417 ADD_ATTR(Attrs.DW_AT_picture_string); 418 ADD_ATTR(Attrs.DW_AT_prototyped); 419 ADD_ATTR(Attrs.DW_AT_small); 420 ADD_ATTR(Attrs.DW_AT_segment); 421 ADD_ATTR(Attrs.DW_AT_string_length); 422 ADD_ATTR(Attrs.DW_AT_threads_scaled); 423 ADD_ATTR(Attrs.DW_AT_upper_bound); 424 ADD_ATTR(Attrs.DW_AT_use_location); 425 ADD_ATTR(Attrs.DW_AT_use_UTF8); 426 ADD_ATTR(Attrs.DW_AT_variable_parameter); 427 ADD_ATTR(Attrs.DW_AT_virtuality); 428 ADD_ATTR(Attrs.DW_AT_visibility); 429 ADD_ATTR(Attrs.DW_AT_vtable_elem_location); 430 ADD_ATTR(Attrs.DW_AT_type); 431 432 // FIXME: Add the extended attributes. 433 } 434 435 // Add all of the attributes for \param Die to the hash. 436 void DIEHash::addAttributes(const DIE &Die) { 437 DIEAttrs Attrs = {}; 438 collectAttributes(Die, Attrs); 439 hashAttributes(Attrs, Die.getTag()); 440 } 441 442 void DIEHash::hashNestedType(const DIE &Die, StringRef Name) { 443 // 7.27 Step 7 444 // ... append the letter 'S', 445 addULEB128('S'); 446 447 // the tag of C, 448 addULEB128(Die.getTag()); 449 450 // and the name. 451 addString(Name); 452 } 453 454 // Compute the hash of a DIE. This is based on the type signature computation 455 // given in section 7.27 of the DWARF4 standard. It is the md5 hash of a 456 // flattened description of the DIE. 457 void DIEHash::computeHash(const DIE &Die) { 458 // Append the letter 'D', followed by the DWARF tag of the DIE. 459 addULEB128('D'); 460 addULEB128(Die.getTag()); 461 462 // Add each of the attributes of the DIE. 463 addAttributes(Die); 464 465 // Then hash each of the children of the DIE. 466 for (auto &C : Die.getChildren()) { 467 // 7.27 Step 7 468 // If C is a nested type entry or a member function entry, ... 469 if (isType(C->getTag()) || C->getTag() == dwarf::DW_TAG_subprogram) { 470 StringRef Name = getDIEStringAttr(*C, dwarf::DW_AT_name); 471 // ... and has a DW_AT_name attribute 472 if (!Name.empty()) { 473 hashNestedType(*C, Name); 474 continue; 475 } 476 } 477 computeHash(*C); 478 } 479 480 // Following the last (or if there are no children), append a zero byte. 481 Hash.update(makeArrayRef((uint8_t)'\0')); 482 } 483 484 /// This is based on the type signature computation given in section 7.27 of the 485 /// DWARF4 standard. It is the md5 hash of a flattened description of the DIE 486 /// with the exception that we are hashing only the context and the name of the 487 /// type. 488 uint64_t DIEHash::computeDIEODRSignature(const DIE &Die) { 489 490 // Add the contexts to the hash. We won't be computing the ODR hash for 491 // function local types so it's safe to use the generic context hashing 492 // algorithm here. 493 // FIXME: If we figure out how to account for linkage in some way we could 494 // actually do this with a slight modification to the parent hash algorithm. 495 if (const DIE *Parent = Die.getParent()) 496 addParentContext(*Parent); 497 498 // Add the current DIE information. 499 500 // Add the DWARF tag of the DIE. 501 addULEB128(Die.getTag()); 502 503 // Add the name of the type to the hash. 504 addString(getDIEStringAttr(Die, dwarf::DW_AT_name)); 505 506 // Now get the result. 507 MD5::MD5Result Result; 508 Hash.final(Result); 509 510 // ... take the least significant 8 bytes and return those. Our MD5 511 // implementation always returns its results in little endian, swap bytes 512 // appropriately. 513 return *reinterpret_cast<support::ulittle64_t *>(Result + 8); 514 } 515 516 /// This is based on the type signature computation given in section 7.27 of the 517 /// DWARF4 standard. It is an md5 hash of the flattened description of the DIE 518 /// with the inclusion of the full CU and all top level CU entities. 519 // TODO: Initialize the type chain at 0 instead of 1 for CU signatures. 520 uint64_t DIEHash::computeCUSignature(const DIE &Die) { 521 Numbering.clear(); 522 Numbering[&Die] = 1; 523 524 // Hash the DIE. 525 computeHash(Die); 526 527 // Now return the result. 528 MD5::MD5Result Result; 529 Hash.final(Result); 530 531 // ... take the least significant 8 bytes and return those. Our MD5 532 // implementation always returns its results in little endian, swap bytes 533 // appropriately. 534 return *reinterpret_cast<support::ulittle64_t *>(Result + 8); 535 } 536 537 /// This is based on the type signature computation given in section 7.27 of the 538 /// DWARF4 standard. It is an md5 hash of the flattened description of the DIE 539 /// with the inclusion of additional forms not specifically called out in the 540 /// standard. 541 uint64_t DIEHash::computeTypeSignature(const DIE &Die) { 542 Numbering.clear(); 543 Numbering[&Die] = 1; 544 545 if (const DIE *Parent = Die.getParent()) 546 addParentContext(*Parent); 547 548 // Hash the DIE. 549 computeHash(Die); 550 551 // Now return the result. 552 MD5::MD5Result Result; 553 Hash.final(Result); 554 555 // ... take the least significant 8 bytes and return those. Our MD5 556 // implementation always returns its results in little endian, swap bytes 557 // appropriately. 558 return *reinterpret_cast<support::ulittle64_t *>(Result + 8); 559 } 560
