1//===- SymbolRewriter.cpp - Symbol Rewriter -------------------------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// SymbolRewriter is a LLVM pass which can rewrite symbols transparently within 10// existing code. It is implemented as a compiler pass and is configured via a 11// YAML configuration file. 12// 13// The YAML configuration file format is as follows: 14// 15// RewriteMapFile := RewriteDescriptors 16// RewriteDescriptors := RewriteDescriptor | RewriteDescriptors 17// RewriteDescriptor := RewriteDescriptorType ':' '{' RewriteDescriptorFields '}' 18// RewriteDescriptorFields := RewriteDescriptorField | RewriteDescriptorFields 19// RewriteDescriptorField := FieldIdentifier ':' FieldValue ',' 20// RewriteDescriptorType := Identifier 21// FieldIdentifier := Identifier 22// FieldValue := Identifier 23// Identifier := [0-9a-zA-Z]+ 24// 25// Currently, the following descriptor types are supported: 26// 27// - function: (function rewriting) 28// + Source (original name of the function) 29// + Target (explicit transformation) 30// + Transform (pattern transformation) 31// + Naked (boolean, whether the function is undecorated) 32// - global variable: (external linkage global variable rewriting) 33// + Source (original name of externally visible variable) 34// + Target (explicit transformation) 35// + Transform (pattern transformation) 36// - global alias: (global alias rewriting) 37// + Source (original name of the aliased name) 38// + Target (explicit transformation) 39// + Transform (pattern transformation) 40// 41// Note that source and exactly one of [Target, Transform] must be provided 42// 43// New rewrite descriptors can be created. Addding a new rewrite descriptor 44// involves: 45// 46// a) extended the rewrite descriptor kind enumeration 47// (<anonymous>::RewriteDescriptor::RewriteDescriptorType) 48// b) implementing the new descriptor 49// (c.f. <anonymous>::ExplicitRewriteFunctionDescriptor) 50// c) extending the rewrite map parser 51// (<anonymous>::RewriteMapParser::parseEntry) 52// 53// Specify to rewrite the symbols using the `-rewrite-symbols` option, and 54// specify the map file to use for the rewriting via the `-rewrite-map-file` 55// option. 56// 57//===----------------------------------------------------------------------===// 58 59#include "llvm/Transforms/Utils/SymbolRewriter.h" 60#include "llvm/ADT/SmallString.h" 61#include "llvm/ADT/StringRef.h" 62#include "llvm/ADT/ilist.h" 63#include "llvm/ADT/iterator_range.h" 64#include "llvm/IR/Comdat.h" 65#include "llvm/IR/Function.h" 66#include "llvm/IR/GlobalAlias.h" 67#include "llvm/IR/GlobalObject.h" 68#include "llvm/IR/GlobalVariable.h" 69#include "llvm/IR/Module.h" 70#include "llvm/IR/Value.h" 71#include "llvm/Support/Casting.h" 72#include "llvm/Support/CommandLine.h" 73#include "llvm/Support/ErrorHandling.h" 74#include "llvm/Support/ErrorOr.h" 75#include "llvm/Support/MemoryBuffer.h" 76#include "llvm/Support/Regex.h" 77#include "llvm/Support/SourceMgr.h" 78#include "llvm/Support/YAMLParser.h" 79#include <memory> 80#include <string> 81#include <vector> 82 83using namespace llvm; 84using namespace SymbolRewriter; 85 86#define DEBUG_TYPE "symbol-rewriter" 87 88static cl::list<std::string> RewriteMapFiles("rewrite-map-file", 89 cl::desc("Symbol Rewrite Map"), 90 cl::value_desc("filename"), 91 cl::Hidden); 92 93static void rewriteComdat(Module &M, GlobalObject *GO, 94 const std::string &Source, 95 const std::string &Target) { 96 if (Comdat *CD = GO->getComdat()) { 97 auto &Comdats = M.getComdatSymbolTable(); 98 99 Comdat *C = M.getOrInsertComdat(Target); 100 C->setSelectionKind(CD->getSelectionKind()); 101 GO->setComdat(C); 102 103 Comdats.erase(Comdats.find(Source)); 104 } 105} 106 107namespace { 108 109template <RewriteDescriptor::Type DT, typename ValueType, 110 ValueType *(Module::*Get)(StringRef) const> 111class ExplicitRewriteDescriptor : public RewriteDescriptor { 112public: 113 const std::string Source; 114 const std::string Target; 115 116 ExplicitRewriteDescriptor(StringRef S, StringRef T, const bool Naked) 117 : RewriteDescriptor(DT), 118 Source(std::string(Naked ? StringRef("\01" + S.str()) : S)), 119 Target(std::string(T)) {} 120 121 bool performOnModule(Module &M) override; 122 123 static bool classof(const RewriteDescriptor *RD) { 124 return RD->getType() == DT; 125 } 126}; 127 128} // end anonymous namespace 129 130template <RewriteDescriptor::Type DT, typename ValueType, 131 ValueType *(Module::*Get)(StringRef) const> 132bool ExplicitRewriteDescriptor<DT, ValueType, Get>::performOnModule(Module &M) { 133 bool Changed = false; 134 if (ValueType *S = (M.*Get)(Source)) { 135 if (GlobalObject *GO = dyn_cast<GlobalObject>(S)) 136 rewriteComdat(M, GO, Source, Target); 137 138 if (Value *T = (M.*Get)(Target)) 139 S->setValueName(T->getValueName()); 140 else 141 S->setName(Target); 142 143 Changed = true; 144 } 145 return Changed; 146} 147 148namespace { 149 150template <RewriteDescriptor::Type DT, typename ValueType, 151 ValueType *(Module::*Get)(StringRef) const, 152 iterator_range<typename iplist<ValueType>::iterator> 153 (Module::*Iterator)()> 154class PatternRewriteDescriptor : public RewriteDescriptor { 155public: 156 const std::string Pattern; 157 const std::string Transform; 158 159 PatternRewriteDescriptor(StringRef P, StringRef T) 160 : RewriteDescriptor(DT), Pattern(std::string(P)), 161 Transform(std::string(T)) {} 162 163 bool performOnModule(Module &M) override; 164 165 static bool classof(const RewriteDescriptor *RD) { 166 return RD->getType() == DT; 167 } 168}; 169 170} // end anonymous namespace 171 172template <RewriteDescriptor::Type DT, typename ValueType, 173 ValueType *(Module::*Get)(StringRef) const, 174 iterator_range<typename iplist<ValueType>::iterator> 175 (Module::*Iterator)()> 176bool PatternRewriteDescriptor<DT, ValueType, Get, Iterator>:: 177performOnModule(Module &M) { 178 bool Changed = false; 179 for (auto &C : (M.*Iterator)()) { 180 std::string Error; 181 182 std::string Name = Regex(Pattern).sub(Transform, C.getName(), &Error); 183 if (!Error.empty()) 184 report_fatal_error(Twine("unable to transforn ") + C.getName() + " in " + 185 M.getModuleIdentifier() + ": " + Error); 186 187 if (C.getName() == Name) 188 continue; 189 190 if (GlobalObject *GO = dyn_cast<GlobalObject>(&C)) 191 rewriteComdat(M, GO, std::string(C.getName()), Name); 192 193 if (Value *V = (M.*Get)(Name)) 194 C.setValueName(V->getValueName()); 195 else 196 C.setName(Name); 197 198 Changed = true; 199 } 200 return Changed; 201} 202 203namespace { 204 205/// Represents a rewrite for an explicitly named (function) symbol. Both the 206/// source function name and target function name of the transformation are 207/// explicitly spelt out. 208using ExplicitRewriteFunctionDescriptor = 209 ExplicitRewriteDescriptor<RewriteDescriptor::Type::Function, Function, 210 &Module::getFunction>; 211 212/// Represents a rewrite for an explicitly named (global variable) symbol. Both 213/// the source variable name and target variable name are spelt out. This 214/// applies only to module level variables. 215using ExplicitRewriteGlobalVariableDescriptor = 216 ExplicitRewriteDescriptor<RewriteDescriptor::Type::GlobalVariable, 217 GlobalVariable, &Module::getGlobalVariable>; 218 219/// Represents a rewrite for an explicitly named global alias. Both the source 220/// and target name are explicitly spelt out. 221using ExplicitRewriteNamedAliasDescriptor = 222 ExplicitRewriteDescriptor<RewriteDescriptor::Type::NamedAlias, GlobalAlias, 223 &Module::getNamedAlias>; 224 225/// Represents a rewrite for a regular expression based pattern for functions. 226/// A pattern for the function name is provided and a transformation for that 227/// pattern to determine the target function name create the rewrite rule. 228using PatternRewriteFunctionDescriptor = 229 PatternRewriteDescriptor<RewriteDescriptor::Type::Function, Function, 230 &Module::getFunction, &Module::functions>; 231 232/// Represents a rewrite for a global variable based upon a matching pattern. 233/// Each global variable matching the provided pattern will be transformed as 234/// described in the transformation pattern for the target. Applies only to 235/// module level variables. 236using PatternRewriteGlobalVariableDescriptor = 237 PatternRewriteDescriptor<RewriteDescriptor::Type::GlobalVariable, 238 GlobalVariable, &Module::getGlobalVariable, 239 &Module::globals>; 240 241/// PatternRewriteNamedAliasDescriptor - represents a rewrite for global 242/// aliases which match a given pattern. The provided transformation will be 243/// applied to each of the matching names. 244using PatternRewriteNamedAliasDescriptor = 245 PatternRewriteDescriptor<RewriteDescriptor::Type::NamedAlias, GlobalAlias, 246 &Module::getNamedAlias, &Module::aliases>; 247 248} // end anonymous namespace 249 250bool RewriteMapParser::parse(const std::string &MapFile, 251 RewriteDescriptorList *DL) { 252 ErrorOr<std::unique_ptr<MemoryBuffer>> Mapping = 253 MemoryBuffer::getFile(MapFile); 254 255 if (!Mapping) 256 report_fatal_error(Twine("unable to read rewrite map '") + MapFile + 257 "': " + Mapping.getError().message()); 258 259 if (!parse(*Mapping, DL)) 260 report_fatal_error(Twine("unable to parse rewrite map '") + MapFile + "'"); 261 262 return true; 263} 264 265bool RewriteMapParser::parse(std::unique_ptr<MemoryBuffer> &MapFile, 266 RewriteDescriptorList *DL) { 267 SourceMgr SM; 268 yaml::Stream YS(MapFile->getBuffer(), SM); 269 270 for (auto &Document : YS) { 271 yaml::MappingNode *DescriptorList; 272 273 // ignore empty documents 274 if (isa<yaml::NullNode>(Document.getRoot())) 275 continue; 276 277 DescriptorList = dyn_cast<yaml::MappingNode>(Document.getRoot()); 278 if (!DescriptorList) { 279 YS.printError(Document.getRoot(), "DescriptorList node must be a map"); 280 return false; 281 } 282 283 for (auto &Descriptor : *DescriptorList) 284 if (!parseEntry(YS, Descriptor, DL)) 285 return false; 286 } 287 288 return true; 289} 290 291bool RewriteMapParser::parseEntry(yaml::Stream &YS, yaml::KeyValueNode &Entry, 292 RewriteDescriptorList *DL) { 293 yaml::ScalarNode *Key; 294 yaml::MappingNode *Value; 295 SmallString<32> KeyStorage; 296 StringRef RewriteType; 297 298 Key = dyn_cast<yaml::ScalarNode>(Entry.getKey()); 299 if (!Key) { 300 YS.printError(Entry.getKey(), "rewrite type must be a scalar"); 301 return false; 302 } 303 304 Value = dyn_cast<yaml::MappingNode>(Entry.getValue()); 305 if (!Value) { 306 YS.printError(Entry.getValue(), "rewrite descriptor must be a map"); 307 return false; 308 } 309 310 RewriteType = Key->getValue(KeyStorage); 311 if (RewriteType.equals("function")) 312 return parseRewriteFunctionDescriptor(YS, Key, Value, DL); 313 else if (RewriteType.equals("global variable")) 314 return parseRewriteGlobalVariableDescriptor(YS, Key, Value, DL); 315 else if (RewriteType.equals("global alias")) 316 return parseRewriteGlobalAliasDescriptor(YS, Key, Value, DL); 317 318 YS.printError(Entry.getKey(), "unknown rewrite type"); 319 return false; 320} 321 322bool RewriteMapParser:: 323parseRewriteFunctionDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 324 yaml::MappingNode *Descriptor, 325 RewriteDescriptorList *DL) { 326 bool Naked = false; 327 std::string Source; 328 std::string Target; 329 std::string Transform; 330 331 for (auto &Field : *Descriptor) { 332 yaml::ScalarNode *Key; 333 yaml::ScalarNode *Value; 334 SmallString<32> KeyStorage; 335 SmallString<32> ValueStorage; 336 StringRef KeyValue; 337 338 Key = dyn_cast<yaml::ScalarNode>(Field.getKey()); 339 if (!Key) { 340 YS.printError(Field.getKey(), "descriptor key must be a scalar"); 341 return false; 342 } 343 344 Value = dyn_cast<yaml::ScalarNode>(Field.getValue()); 345 if (!Value) { 346 YS.printError(Field.getValue(), "descriptor value must be a scalar"); 347 return false; 348 } 349 350 KeyValue = Key->getValue(KeyStorage); 351 if (KeyValue.equals("source")) { 352 std::string Error; 353 354 Source = std::string(Value->getValue(ValueStorage)); 355 if (!Regex(Source).isValid(Error)) { 356 YS.printError(Field.getKey(), "invalid regex: " + Error); 357 return false; 358 } 359 } else if (KeyValue.equals("target")) { 360 Target = std::string(Value->getValue(ValueStorage)); 361 } else if (KeyValue.equals("transform")) { 362 Transform = std::string(Value->getValue(ValueStorage)); 363 } else if (KeyValue.equals("naked")) { 364 std::string Undecorated; 365 366 Undecorated = std::string(Value->getValue(ValueStorage)); 367 Naked = StringRef(Undecorated).lower() == "true" || Undecorated == "1"; 368 } else { 369 YS.printError(Field.getKey(), "unknown key for function"); 370 return false; 371 } 372 } 373 374 if (Transform.empty() == Target.empty()) { 375 YS.printError(Descriptor, 376 "exactly one of transform or target must be specified"); 377 return false; 378 } 379 380 // TODO see if there is a more elegant solution to selecting the rewrite 381 // descriptor type 382 if (!Target.empty()) 383 DL->push_back(std::make_unique<ExplicitRewriteFunctionDescriptor>( 384 Source, Target, Naked)); 385 else 386 DL->push_back( 387 std::make_unique<PatternRewriteFunctionDescriptor>(Source, Transform)); 388 389 return true; 390} 391 392bool RewriteMapParser:: 393parseRewriteGlobalVariableDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 394 yaml::MappingNode *Descriptor, 395 RewriteDescriptorList *DL) { 396 std::string Source; 397 std::string Target; 398 std::string Transform; 399 400 for (auto &Field : *Descriptor) { 401 yaml::ScalarNode *Key; 402 yaml::ScalarNode *Value; 403 SmallString<32> KeyStorage; 404 SmallString<32> ValueStorage; 405 StringRef KeyValue; 406 407 Key = dyn_cast<yaml::ScalarNode>(Field.getKey()); 408 if (!Key) { 409 YS.printError(Field.getKey(), "descriptor Key must be a scalar"); 410 return false; 411 } 412 413 Value = dyn_cast<yaml::ScalarNode>(Field.getValue()); 414 if (!Value) { 415 YS.printError(Field.getValue(), "descriptor value must be a scalar"); 416 return false; 417 } 418 419 KeyValue = Key->getValue(KeyStorage); 420 if (KeyValue.equals("source")) { 421 std::string Error; 422 423 Source = std::string(Value->getValue(ValueStorage)); 424 if (!Regex(Source).isValid(Error)) { 425 YS.printError(Field.getKey(), "invalid regex: " + Error); 426 return false; 427 } 428 } else if (KeyValue.equals("target")) { 429 Target = std::string(Value->getValue(ValueStorage)); 430 } else if (KeyValue.equals("transform")) { 431 Transform = std::string(Value->getValue(ValueStorage)); 432 } else { 433 YS.printError(Field.getKey(), "unknown Key for Global Variable"); 434 return false; 435 } 436 } 437 438 if (Transform.empty() == Target.empty()) { 439 YS.printError(Descriptor, 440 "exactly one of transform or target must be specified"); 441 return false; 442 } 443 444 if (!Target.empty()) 445 DL->push_back(std::make_unique<ExplicitRewriteGlobalVariableDescriptor>( 446 Source, Target, 447 /*Naked*/ false)); 448 else 449 DL->push_back(std::make_unique<PatternRewriteGlobalVariableDescriptor>( 450 Source, Transform)); 451 452 return true; 453} 454 455bool RewriteMapParser:: 456parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 457 yaml::MappingNode *Descriptor, 458 RewriteDescriptorList *DL) { 459 std::string Source; 460 std::string Target; 461 std::string Transform; 462 463 for (auto &Field : *Descriptor) { 464 yaml::ScalarNode *Key; 465 yaml::ScalarNode *Value; 466 SmallString<32> KeyStorage; 467 SmallString<32> ValueStorage; 468 StringRef KeyValue; 469 470 Key = dyn_cast<yaml::ScalarNode>(Field.getKey()); 471 if (!Key) { 472 YS.printError(Field.getKey(), "descriptor key must be a scalar"); 473 return false; 474 } 475 476 Value = dyn_cast<yaml::ScalarNode>(Field.getValue()); 477 if (!Value) { 478 YS.printError(Field.getValue(), "descriptor value must be a scalar"); 479 return false; 480 } 481 482 KeyValue = Key->getValue(KeyStorage); 483 if (KeyValue.equals("source")) { 484 std::string Error; 485 486 Source = std::string(Value->getValue(ValueStorage)); 487 if (!Regex(Source).isValid(Error)) { 488 YS.printError(Field.getKey(), "invalid regex: " + Error); 489 return false; 490 } 491 } else if (KeyValue.equals("target")) { 492 Target = std::string(Value->getValue(ValueStorage)); 493 } else if (KeyValue.equals("transform")) { 494 Transform = std::string(Value->getValue(ValueStorage)); 495 } else { 496 YS.printError(Field.getKey(), "unknown key for Global Alias"); 497 return false; 498 } 499 } 500 501 if (Transform.empty() == Target.empty()) { 502 YS.printError(Descriptor, 503 "exactly one of transform or target must be specified"); 504 return false; 505 } 506 507 if (!Target.empty()) 508 DL->push_back(std::make_unique<ExplicitRewriteNamedAliasDescriptor>( 509 Source, Target, 510 /*Naked*/ false)); 511 else 512 DL->push_back(std::make_unique<PatternRewriteNamedAliasDescriptor>( 513 Source, Transform)); 514 515 return true; 516} 517 518PreservedAnalyses RewriteSymbolPass::run(Module &M, ModuleAnalysisManager &AM) { 519 if (!runImpl(M)) 520 return PreservedAnalyses::all(); 521 522 return PreservedAnalyses::none(); 523} 524 525bool RewriteSymbolPass::runImpl(Module &M) { 526 bool Changed; 527 528 Changed = false; 529 for (auto &Descriptor : Descriptors) 530 Changed |= Descriptor->performOnModule(M); 531 532 return Changed; 533} 534 535void RewriteSymbolPass::loadAndParseMapFiles() { 536 const std::vector<std::string> MapFiles(RewriteMapFiles); 537 SymbolRewriter::RewriteMapParser Parser; 538 539 for (const auto &MapFile : MapFiles) 540 Parser.parse(MapFile, &Descriptors); 541} 542