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
83 using namespace llvm;
84 using namespace SymbolRewriter;
85
86 #define DEBUG_TYPE "symbol-rewriter"
87
88 static cl::list<std::string> RewriteMapFiles("rewrite-map-file",
89 cl::desc("Symbol Rewrite Map"),
90 cl::value_desc("filename"),
91 cl::Hidden);
92
rewriteComdat(Module & M,GlobalObject * GO,const std::string & Source,const std::string & Target)93 static 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
107 namespace {
108
109 template <RewriteDescriptor::Type DT, typename ValueType,
110 ValueType *(Module::*Get)(StringRef) const>
111 class ExplicitRewriteDescriptor : public RewriteDescriptor {
112 public:
113 const std::string Source;
114 const std::string Target;
115
ExplicitRewriteDescriptor(StringRef S,StringRef T,const bool Naked)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
classof(const RewriteDescriptor * RD)123 static bool classof(const RewriteDescriptor *RD) {
124 return RD->getType() == DT;
125 }
126 };
127
128 } // end anonymous namespace
129
130 template <RewriteDescriptor::Type DT, typename ValueType,
131 ValueType *(Module::*Get)(StringRef) const>
performOnModule(Module & M)132 bool 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
148 namespace {
149
150 template <RewriteDescriptor::Type DT, typename ValueType,
151 ValueType *(Module::*Get)(StringRef) const,
152 iterator_range<typename iplist<ValueType>::iterator>
153 (Module::*Iterator)()>
154 class PatternRewriteDescriptor : public RewriteDescriptor {
155 public:
156 const std::string Pattern;
157 const std::string Transform;
158
PatternRewriteDescriptor(StringRef P,StringRef T)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
classof(const RewriteDescriptor * RD)165 static bool classof(const RewriteDescriptor *RD) {
166 return RD->getType() == DT;
167 }
168 };
169
170 } // end anonymous namespace
171
172 template <RewriteDescriptor::Type DT, typename ValueType,
173 ValueType *(Module::*Get)(StringRef) const,
174 iterator_range<typename iplist<ValueType>::iterator>
175 (Module::*Iterator)()>
176 bool PatternRewriteDescriptor<DT, ValueType, Get, Iterator>::
performOnModule(Module & M)177 performOnModule(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
203 namespace {
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.
208 using 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.
215 using 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.
221 using 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.
228 using 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.
236 using 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.
244 using PatternRewriteNamedAliasDescriptor =
245 PatternRewriteDescriptor<RewriteDescriptor::Type::NamedAlias, GlobalAlias,
246 &Module::getNamedAlias, &Module::aliases>;
247
248 } // end anonymous namespace
249
parse(const std::string & MapFile,RewriteDescriptorList * DL)250 bool 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
parse(std::unique_ptr<MemoryBuffer> & MapFile,RewriteDescriptorList * DL)265 bool 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
parseEntry(yaml::Stream & YS,yaml::KeyValueNode & Entry,RewriteDescriptorList * DL)291 bool 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
322 bool RewriteMapParser::
parseRewriteFunctionDescriptor(yaml::Stream & YS,yaml::ScalarNode * K,yaml::MappingNode * Descriptor,RewriteDescriptorList * DL)323 parseRewriteFunctionDescriptor(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
392 bool RewriteMapParser::
parseRewriteGlobalVariableDescriptor(yaml::Stream & YS,yaml::ScalarNode * K,yaml::MappingNode * Descriptor,RewriteDescriptorList * DL)393 parseRewriteGlobalVariableDescriptor(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
455 bool RewriteMapParser::
parseRewriteGlobalAliasDescriptor(yaml::Stream & YS,yaml::ScalarNode * K,yaml::MappingNode * Descriptor,RewriteDescriptorList * DL)456 parseRewriteGlobalAliasDescriptor(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
run(Module & M,ModuleAnalysisManager & AM)518 PreservedAnalyses RewriteSymbolPass::run(Module &M, ModuleAnalysisManager &AM) {
519 if (!runImpl(M))
520 return PreservedAnalyses::all();
521
522 return PreservedAnalyses::none();
523 }
524
runImpl(Module & M)525 bool 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
loadAndParseMapFiles()535 void 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