1 //== SymbolManager.h - Management of Symbolic Values ------------*- C++ -*--==//
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 defines SymbolManager, a class that manages symbolic values
11 //  created for use by ExprEngine and related classes.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
16 #include "clang/Analysis/Analyses/LiveVariables.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
19 #include "llvm/Support/raw_ostream.h"
20 
21 using namespace clang;
22 using namespace ento;
23 
24 void SymExpr::anchor() { }
25 
26 LLVM_DUMP_METHOD void SymExpr::dump() const {
27   dumpToStream(llvm::errs());
28 }
29 
30 void SymIntExpr::dumpToStream(raw_ostream &os) const {
31   os << '(';
32   getLHS()->dumpToStream(os);
33   os << ") "
34      << BinaryOperator::getOpcodeStr(getOpcode()) << ' '
35      << getRHS().getZExtValue();
36   if (getRHS().isUnsigned())
37     os << 'U';
38 }
39 
40 void IntSymExpr::dumpToStream(raw_ostream &os) const {
41   os << getLHS().getZExtValue();
42   if (getLHS().isUnsigned())
43     os << 'U';
44   os << ' '
45      << BinaryOperator::getOpcodeStr(getOpcode())
46      << " (";
47   getRHS()->dumpToStream(os);
48   os << ')';
49 }
50 
51 void SymSymExpr::dumpToStream(raw_ostream &os) const {
52   os << '(';
53   getLHS()->dumpToStream(os);
54   os << ") "
55      << BinaryOperator::getOpcodeStr(getOpcode())
56      << " (";
57   getRHS()->dumpToStream(os);
58   os << ')';
59 }
60 
61 void SymbolCast::dumpToStream(raw_ostream &os) const {
62   os << '(' << ToTy.getAsString() << ") (";
63   Operand->dumpToStream(os);
64   os << ')';
65 }
66 
67 void SymbolConjured::dumpToStream(raw_ostream &os) const {
68   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
69 }
70 
71 void SymbolDerived::dumpToStream(raw_ostream &os) const {
72   os << "derived_$" << getSymbolID() << '{'
73      << getParentSymbol() << ',' << getRegion() << '}';
74 }
75 
76 void SymbolExtent::dumpToStream(raw_ostream &os) const {
77   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
78 }
79 
80 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
81   os << "meta_$" << getSymbolID() << '{'
82      << getRegion() << ',' << T.getAsString() << '}';
83 }
84 
85 void SymbolData::anchor() { }
86 
87 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
88   os << "reg_$" << getSymbolID() << "<" << R << ">";
89 }
90 
91 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
92   return itr == X.itr;
93 }
94 
95 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
96   return itr != X.itr;
97 }
98 
99 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
100   itr.push_back(SE);
101 }
102 
103 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
104   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
105   expand();
106   return *this;
107 }
108 
109 SymbolRef SymExpr::symbol_iterator::operator*() {
110   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
111   return itr.back();
112 }
113 
114 void SymExpr::symbol_iterator::expand() {
115   const SymExpr *SE = itr.pop_back_val();
116 
117   switch (SE->getKind()) {
118     case SymExpr::SymbolRegionValueKind:
119     case SymExpr::SymbolConjuredKind:
120     case SymExpr::SymbolDerivedKind:
121     case SymExpr::SymbolExtentKind:
122     case SymExpr::SymbolMetadataKind:
123       return;
124     case SymExpr::SymbolCastKind:
125       itr.push_back(cast<SymbolCast>(SE)->getOperand());
126       return;
127     case SymExpr::SymIntExprKind:
128       itr.push_back(cast<SymIntExpr>(SE)->getLHS());
129       return;
130     case SymExpr::IntSymExprKind:
131       itr.push_back(cast<IntSymExpr>(SE)->getRHS());
132       return;
133     case SymExpr::SymSymExprKind: {
134       const SymSymExpr *x = cast<SymSymExpr>(SE);
135       itr.push_back(x->getLHS());
136       itr.push_back(x->getRHS());
137       return;
138     }
139   }
140   llvm_unreachable("unhandled expansion case");
141 }
142 
143 unsigned SymExpr::computeComplexity() const {
144   unsigned R = 0;
145   for (symbol_iterator I = symbol_begin(), E = symbol_end(); I != E; ++I)
146     R++;
147   return R;
148 }
149 
150 const SymbolRegionValue*
151 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
152   llvm::FoldingSetNodeID profile;
153   SymbolRegionValue::Profile(profile, R);
154   void *InsertPos;
155   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
156   if (!SD) {
157     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
158     new (SD) SymbolRegionValue(SymbolCounter, R);
159     DataSet.InsertNode(SD, InsertPos);
160     ++SymbolCounter;
161   }
162 
163   return cast<SymbolRegionValue>(SD);
164 }
165 
166 const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
167                                                    const LocationContext *LCtx,
168                                                    QualType T,
169                                                    unsigned Count,
170                                                    const void *SymbolTag) {
171   llvm::FoldingSetNodeID profile;
172   SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
173   void *InsertPos;
174   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
175   if (!SD) {
176     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
177     new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
178     DataSet.InsertNode(SD, InsertPos);
179     ++SymbolCounter;
180   }
181 
182   return cast<SymbolConjured>(SD);
183 }
184 
185 const SymbolDerived*
186 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
187                                 const TypedValueRegion *R) {
188 
189   llvm::FoldingSetNodeID profile;
190   SymbolDerived::Profile(profile, parentSymbol, R);
191   void *InsertPos;
192   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
193   if (!SD) {
194     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
195     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
196     DataSet.InsertNode(SD, InsertPos);
197     ++SymbolCounter;
198   }
199 
200   return cast<SymbolDerived>(SD);
201 }
202 
203 const SymbolExtent*
204 SymbolManager::getExtentSymbol(const SubRegion *R) {
205   llvm::FoldingSetNodeID profile;
206   SymbolExtent::Profile(profile, R);
207   void *InsertPos;
208   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
209   if (!SD) {
210     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
211     new (SD) SymbolExtent(SymbolCounter, R);
212     DataSet.InsertNode(SD, InsertPos);
213     ++SymbolCounter;
214   }
215 
216   return cast<SymbolExtent>(SD);
217 }
218 
219 const SymbolMetadata *
220 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
221                                  const LocationContext *LCtx,
222                                  unsigned Count, const void *SymbolTag) {
223 
224   llvm::FoldingSetNodeID profile;
225   SymbolMetadata::Profile(profile, R, S, T, LCtx, Count, SymbolTag);
226   void *InsertPos;
227   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
228   if (!SD) {
229     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
230     new (SD) SymbolMetadata(SymbolCounter, R, S, T, LCtx, Count, SymbolTag);
231     DataSet.InsertNode(SD, InsertPos);
232     ++SymbolCounter;
233   }
234 
235   return cast<SymbolMetadata>(SD);
236 }
237 
238 const SymbolCast*
239 SymbolManager::getCastSymbol(const SymExpr *Op,
240                              QualType From, QualType To) {
241   llvm::FoldingSetNodeID ID;
242   SymbolCast::Profile(ID, Op, From, To);
243   void *InsertPos;
244   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
245   if (!data) {
246     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
247     new (data) SymbolCast(Op, From, To);
248     DataSet.InsertNode(data, InsertPos);
249   }
250 
251   return cast<SymbolCast>(data);
252 }
253 
254 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
255                                                BinaryOperator::Opcode op,
256                                                const llvm::APSInt& v,
257                                                QualType t) {
258   llvm::FoldingSetNodeID ID;
259   SymIntExpr::Profile(ID, lhs, op, v, t);
260   void *InsertPos;
261   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
262 
263   if (!data) {
264     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
265     new (data) SymIntExpr(lhs, op, v, t);
266     DataSet.InsertNode(data, InsertPos);
267   }
268 
269   return cast<SymIntExpr>(data);
270 }
271 
272 const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
273                                                BinaryOperator::Opcode op,
274                                                const SymExpr *rhs,
275                                                QualType t) {
276   llvm::FoldingSetNodeID ID;
277   IntSymExpr::Profile(ID, lhs, op, rhs, t);
278   void *InsertPos;
279   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
280 
281   if (!data) {
282     data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
283     new (data) IntSymExpr(lhs, op, rhs, t);
284     DataSet.InsertNode(data, InsertPos);
285   }
286 
287   return cast<IntSymExpr>(data);
288 }
289 
290 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
291                                                BinaryOperator::Opcode op,
292                                                const SymExpr *rhs,
293                                                QualType t) {
294   llvm::FoldingSetNodeID ID;
295   SymSymExpr::Profile(ID, lhs, op, rhs, t);
296   void *InsertPos;
297   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
298 
299   if (!data) {
300     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
301     new (data) SymSymExpr(lhs, op, rhs, t);
302     DataSet.InsertNode(data, InsertPos);
303   }
304 
305   return cast<SymSymExpr>(data);
306 }
307 
308 QualType SymbolConjured::getType() const {
309   return T;
310 }
311 
312 QualType SymbolDerived::getType() const {
313   return R->getValueType();
314 }
315 
316 QualType SymbolExtent::getType() const {
317   ASTContext &Ctx = R->getMemRegionManager()->getContext();
318   return Ctx.getSizeType();
319 }
320 
321 QualType SymbolMetadata::getType() const {
322   return T;
323 }
324 
325 QualType SymbolRegionValue::getType() const {
326   return R->getValueType();
327 }
328 
329 SymbolManager::~SymbolManager() {
330   llvm::DeleteContainerSeconds(SymbolDependencies);
331 }
332 
333 bool SymbolManager::canSymbolicate(QualType T) {
334   T = T.getCanonicalType();
335 
336   if (Loc::isLocType(T))
337     return true;
338 
339   if (T->isIntegralOrEnumerationType())
340     return true;
341 
342   if (T->isRecordType() && !T->isUnionType())
343     return true;
344 
345   return false;
346 }
347 
348 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
349                                         const SymbolRef Dependent) {
350   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
351   SymbolRefSmallVectorTy *dependencies = nullptr;
352   if (I == SymbolDependencies.end()) {
353     dependencies = new SymbolRefSmallVectorTy();
354     SymbolDependencies[Primary] = dependencies;
355   } else {
356     dependencies = I->second;
357   }
358   dependencies->push_back(Dependent);
359 }
360 
361 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
362                                                      const SymbolRef Primary) {
363   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
364   if (I == SymbolDependencies.end())
365     return nullptr;
366   return I->second;
367 }
368 
369 void SymbolReaper::markDependentsLive(SymbolRef sym) {
370   // Do not mark dependents more then once.
371   SymbolMapTy::iterator LI = TheLiving.find(sym);
372   assert(LI != TheLiving.end() && "The primary symbol is not live.");
373   if (LI->second == HaveMarkedDependents)
374     return;
375   LI->second = HaveMarkedDependents;
376 
377   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
378     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
379                                                 E = Deps->end(); I != E; ++I) {
380       if (TheLiving.find(*I) != TheLiving.end())
381         continue;
382       markLive(*I);
383     }
384   }
385 }
386 
387 void SymbolReaper::markLive(SymbolRef sym) {
388   TheLiving[sym] = NotProcessed;
389   TheDead.erase(sym);
390   markDependentsLive(sym);
391 }
392 
393 void SymbolReaper::markLive(const MemRegion *region) {
394   RegionRoots.insert(region);
395   markElementIndicesLive(region);
396 }
397 
398 void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
399   for (auto SR = dyn_cast<SubRegion>(region); SR;
400        SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
401     if (auto ER = dyn_cast<ElementRegion>(SR)) {
402       SVal Idx = ER->getIndex();
403       for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
404         markLive(*SI);
405     }
406   }
407 }
408 
409 void SymbolReaper::markInUse(SymbolRef sym) {
410   if (isa<SymbolMetadata>(sym))
411     MetadataInUse.insert(sym);
412 }
413 
414 bool SymbolReaper::maybeDead(SymbolRef sym) {
415   if (isLive(sym))
416     return false;
417 
418   TheDead.insert(sym);
419   return true;
420 }
421 
422 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
423   if (RegionRoots.count(MR))
424     return true;
425 
426   MR = MR->getBaseRegion();
427 
428   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
429     return isLive(SR->getSymbol());
430 
431   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
432     return isLive(VR, true);
433 
434   // FIXME: This is a gross over-approximation. What we really need is a way to
435   // tell if anything still refers to this region. Unlike SymbolicRegions,
436   // AllocaRegions don't have associated symbols, though, so we don't actually
437   // have a way to track their liveness.
438   if (isa<AllocaRegion>(MR))
439     return true;
440 
441   if (isa<CXXThisRegion>(MR))
442     return true;
443 
444   if (isa<MemSpaceRegion>(MR))
445     return true;
446 
447   if (isa<CodeTextRegion>(MR))
448     return true;
449 
450   return false;
451 }
452 
453 bool SymbolReaper::isLive(SymbolRef sym) {
454   if (TheLiving.count(sym)) {
455     markDependentsLive(sym);
456     return true;
457   }
458 
459   bool KnownLive;
460 
461   switch (sym->getKind()) {
462   case SymExpr::SymbolRegionValueKind:
463     KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
464     break;
465   case SymExpr::SymbolConjuredKind:
466     KnownLive = false;
467     break;
468   case SymExpr::SymbolDerivedKind:
469     KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
470     break;
471   case SymExpr::SymbolExtentKind:
472     KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
473     break;
474   case SymExpr::SymbolMetadataKind:
475     KnownLive = MetadataInUse.count(sym) &&
476                 isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
477     if (KnownLive)
478       MetadataInUse.erase(sym);
479     break;
480   case SymExpr::SymIntExprKind:
481     KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
482     break;
483   case SymExpr::IntSymExprKind:
484     KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
485     break;
486   case SymExpr::SymSymExprKind:
487     KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
488                 isLive(cast<SymSymExpr>(sym)->getRHS());
489     break;
490   case SymExpr::SymbolCastKind:
491     KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
492     break;
493   }
494 
495   if (KnownLive)
496     markLive(sym);
497 
498   return KnownLive;
499 }
500 
501 bool
502 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
503   if (LCtx == nullptr)
504     return false;
505 
506   if (LCtx != ELCtx) {
507     // If the reaper's location context is a parent of the expression's
508     // location context, then the expression value is now "out of scope".
509     if (LCtx->isParentOf(ELCtx))
510       return false;
511     return true;
512   }
513 
514   // If no statement is provided, everything is this and parent contexts is live.
515   if (!Loc)
516     return true;
517 
518   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
519 }
520 
521 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
522   const StackFrameContext *VarContext = VR->getStackFrame();
523 
524   if (!VarContext)
525     return true;
526 
527   if (!LCtx)
528     return false;
529   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
530 
531   if (VarContext == CurrentContext) {
532     // If no statement is provided, everything is live.
533     if (!Loc)
534       return true;
535 
536     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
537       return true;
538 
539     if (!includeStoreBindings)
540       return false;
541 
542     unsigned &cachedQuery =
543       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
544 
545     if (cachedQuery) {
546       return cachedQuery == 1;
547     }
548 
549     // Query the store to see if the region occurs in any live bindings.
550     if (Store store = reapedStore.getStore()) {
551       bool hasRegion =
552         reapedStore.getStoreManager().includedInBindings(store, VR);
553       cachedQuery = hasRegion ? 1 : 2;
554       return hasRegion;
555     }
556 
557     return false;
558   }
559 
560   return VarContext->isParentOf(CurrentContext);
561 }
562