• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
anchor()24 void SymExpr::anchor() { }
25 
dump() const26 LLVM_DUMP_METHOD void SymExpr::dump() const {
27   dumpToStream(llvm::errs());
28 }
29 
dumpToStream(raw_ostream & os) const30 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 
dumpToStream(raw_ostream & os) const40 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 
dumpToStream(raw_ostream & os) const51 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 
dumpToStream(raw_ostream & os) const61 void SymbolCast::dumpToStream(raw_ostream &os) const {
62   os << '(' << ToTy.getAsString() << ") (";
63   Operand->dumpToStream(os);
64   os << ')';
65 }
66 
dumpToStream(raw_ostream & os) const67 void SymbolConjured::dumpToStream(raw_ostream &os) const {
68   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
69 }
70 
dumpToStream(raw_ostream & os) const71 void SymbolDerived::dumpToStream(raw_ostream &os) const {
72   os << "derived_$" << getSymbolID() << '{'
73      << getParentSymbol() << ',' << getRegion() << '}';
74 }
75 
dumpToStream(raw_ostream & os) const76 void SymbolExtent::dumpToStream(raw_ostream &os) const {
77   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
78 }
79 
dumpToStream(raw_ostream & os) const80 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
81   os << "meta_$" << getSymbolID() << '{'
82      << getRegion() << ',' << T.getAsString() << '}';
83 }
84 
anchor()85 void SymbolData::anchor() { }
86 
dumpToStream(raw_ostream & os) const87 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
88   os << "reg_$" << getSymbolID() << "<" << R << ">";
89 }
90 
operator ==(const symbol_iterator & X) const91 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
92   return itr == X.itr;
93 }
94 
operator !=(const symbol_iterator & X) const95 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
96   return itr != X.itr;
97 }
98 
symbol_iterator(const SymExpr * SE)99 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
100   itr.push_back(SE);
101 }
102 
operator ++()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 
operator *()109 SymbolRef SymExpr::symbol_iterator::operator*() {
110   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
111   return itr.back();
112 }
113 
expand()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 
computeComplexity() const143 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*
getRegionValueSymbol(const TypedValueRegion * R)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 
conjureSymbol(const Stmt * E,const LocationContext * LCtx,QualType T,unsigned Count,const void * SymbolTag)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*
getDerivedSymbol(SymbolRef parentSymbol,const TypedValueRegion * R)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*
getExtentSymbol(const SubRegion * R)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*
getMetadataSymbol(const MemRegion * R,const Stmt * S,QualType T,unsigned Count,const void * SymbolTag)220 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
221                                  unsigned Count, const void *SymbolTag) {
222 
223   llvm::FoldingSetNodeID profile;
224   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
225   void *InsertPos;
226   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
227   if (!SD) {
228     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
229     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
230     DataSet.InsertNode(SD, InsertPos);
231     ++SymbolCounter;
232   }
233 
234   return cast<SymbolMetadata>(SD);
235 }
236 
237 const SymbolCast*
getCastSymbol(const SymExpr * Op,QualType From,QualType To)238 SymbolManager::getCastSymbol(const SymExpr *Op,
239                              QualType From, QualType To) {
240   llvm::FoldingSetNodeID ID;
241   SymbolCast::Profile(ID, Op, From, To);
242   void *InsertPos;
243   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
244   if (!data) {
245     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
246     new (data) SymbolCast(Op, From, To);
247     DataSet.InsertNode(data, InsertPos);
248   }
249 
250   return cast<SymbolCast>(data);
251 }
252 
getSymIntExpr(const SymExpr * lhs,BinaryOperator::Opcode op,const llvm::APSInt & v,QualType t)253 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
254                                                BinaryOperator::Opcode op,
255                                                const llvm::APSInt& v,
256                                                QualType t) {
257   llvm::FoldingSetNodeID ID;
258   SymIntExpr::Profile(ID, lhs, op, v, t);
259   void *InsertPos;
260   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
261 
262   if (!data) {
263     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
264     new (data) SymIntExpr(lhs, op, v, t);
265     DataSet.InsertNode(data, InsertPos);
266   }
267 
268   return cast<SymIntExpr>(data);
269 }
270 
getIntSymExpr(const llvm::APSInt & lhs,BinaryOperator::Opcode op,const SymExpr * rhs,QualType t)271 const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
272                                                BinaryOperator::Opcode op,
273                                                const SymExpr *rhs,
274                                                QualType t) {
275   llvm::FoldingSetNodeID ID;
276   IntSymExpr::Profile(ID, lhs, op, rhs, t);
277   void *InsertPos;
278   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
279 
280   if (!data) {
281     data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
282     new (data) IntSymExpr(lhs, op, rhs, t);
283     DataSet.InsertNode(data, InsertPos);
284   }
285 
286   return cast<IntSymExpr>(data);
287 }
288 
getSymSymExpr(const SymExpr * lhs,BinaryOperator::Opcode op,const SymExpr * rhs,QualType t)289 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
290                                                BinaryOperator::Opcode op,
291                                                const SymExpr *rhs,
292                                                QualType t) {
293   llvm::FoldingSetNodeID ID;
294   SymSymExpr::Profile(ID, lhs, op, rhs, t);
295   void *InsertPos;
296   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
297 
298   if (!data) {
299     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
300     new (data) SymSymExpr(lhs, op, rhs, t);
301     DataSet.InsertNode(data, InsertPos);
302   }
303 
304   return cast<SymSymExpr>(data);
305 }
306 
getType() const307 QualType SymbolConjured::getType() const {
308   return T;
309 }
310 
getType() const311 QualType SymbolDerived::getType() const {
312   return R->getValueType();
313 }
314 
getType() const315 QualType SymbolExtent::getType() const {
316   ASTContext &Ctx = R->getMemRegionManager()->getContext();
317   return Ctx.getSizeType();
318 }
319 
getType() const320 QualType SymbolMetadata::getType() const {
321   return T;
322 }
323 
getType() const324 QualType SymbolRegionValue::getType() const {
325   return R->getValueType();
326 }
327 
~SymbolManager()328 SymbolManager::~SymbolManager() {
329   llvm::DeleteContainerSeconds(SymbolDependencies);
330 }
331 
canSymbolicate(QualType T)332 bool SymbolManager::canSymbolicate(QualType T) {
333   T = T.getCanonicalType();
334 
335   if (Loc::isLocType(T))
336     return true;
337 
338   if (T->isIntegralOrEnumerationType())
339     return true;
340 
341   if (T->isRecordType() && !T->isUnionType())
342     return true;
343 
344   return false;
345 }
346 
addSymbolDependency(const SymbolRef Primary,const SymbolRef Dependent)347 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
348                                         const SymbolRef Dependent) {
349   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
350   SymbolRefSmallVectorTy *dependencies = nullptr;
351   if (I == SymbolDependencies.end()) {
352     dependencies = new SymbolRefSmallVectorTy();
353     SymbolDependencies[Primary] = dependencies;
354   } else {
355     dependencies = I->second;
356   }
357   dependencies->push_back(Dependent);
358 }
359 
getDependentSymbols(const SymbolRef Primary)360 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
361                                                      const SymbolRef Primary) {
362   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
363   if (I == SymbolDependencies.end())
364     return nullptr;
365   return I->second;
366 }
367 
markDependentsLive(SymbolRef sym)368 void SymbolReaper::markDependentsLive(SymbolRef sym) {
369   // Do not mark dependents more then once.
370   SymbolMapTy::iterator LI = TheLiving.find(sym);
371   assert(LI != TheLiving.end() && "The primary symbol is not live.");
372   if (LI->second == HaveMarkedDependents)
373     return;
374   LI->second = HaveMarkedDependents;
375 
376   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
377     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
378                                                 E = Deps->end(); I != E; ++I) {
379       if (TheLiving.find(*I) != TheLiving.end())
380         continue;
381       markLive(*I);
382     }
383   }
384 }
385 
markLive(SymbolRef sym)386 void SymbolReaper::markLive(SymbolRef sym) {
387   TheLiving[sym] = NotProcessed;
388   TheDead.erase(sym);
389   markDependentsLive(sym);
390 }
391 
markLive(const MemRegion * region)392 void SymbolReaper::markLive(const MemRegion *region) {
393   RegionRoots.insert(region);
394   markElementIndicesLive(region);
395 }
396 
markElementIndicesLive(const MemRegion * region)397 void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
398   for (auto SR = dyn_cast<SubRegion>(region); SR;
399        SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
400     if (auto ER = dyn_cast<ElementRegion>(SR)) {
401       SVal Idx = ER->getIndex();
402       for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
403         markLive(*SI);
404     }
405   }
406 }
407 
markInUse(SymbolRef sym)408 void SymbolReaper::markInUse(SymbolRef sym) {
409   if (isa<SymbolMetadata>(sym))
410     MetadataInUse.insert(sym);
411 }
412 
maybeDead(SymbolRef sym)413 bool SymbolReaper::maybeDead(SymbolRef sym) {
414   if (isLive(sym))
415     return false;
416 
417   TheDead.insert(sym);
418   return true;
419 }
420 
isLiveRegion(const MemRegion * MR)421 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
422   if (RegionRoots.count(MR))
423     return true;
424 
425   MR = MR->getBaseRegion();
426 
427   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
428     return isLive(SR->getSymbol());
429 
430   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
431     return isLive(VR, true);
432 
433   // FIXME: This is a gross over-approximation. What we really need is a way to
434   // tell if anything still refers to this region. Unlike SymbolicRegions,
435   // AllocaRegions don't have associated symbols, though, so we don't actually
436   // have a way to track their liveness.
437   if (isa<AllocaRegion>(MR))
438     return true;
439 
440   if (isa<CXXThisRegion>(MR))
441     return true;
442 
443   if (isa<MemSpaceRegion>(MR))
444     return true;
445 
446   if (isa<CodeTextRegion>(MR))
447     return true;
448 
449   return false;
450 }
451 
isLive(SymbolRef sym)452 bool SymbolReaper::isLive(SymbolRef sym) {
453   if (TheLiving.count(sym)) {
454     markDependentsLive(sym);
455     return true;
456   }
457 
458   bool KnownLive;
459 
460   switch (sym->getKind()) {
461   case SymExpr::SymbolRegionValueKind:
462     KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
463     break;
464   case SymExpr::SymbolConjuredKind:
465     KnownLive = false;
466     break;
467   case SymExpr::SymbolDerivedKind:
468     KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
469     break;
470   case SymExpr::SymbolExtentKind:
471     KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
472     break;
473   case SymExpr::SymbolMetadataKind:
474     KnownLive = MetadataInUse.count(sym) &&
475                 isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
476     if (KnownLive)
477       MetadataInUse.erase(sym);
478     break;
479   case SymExpr::SymIntExprKind:
480     KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
481     break;
482   case SymExpr::IntSymExprKind:
483     KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
484     break;
485   case SymExpr::SymSymExprKind:
486     KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
487                 isLive(cast<SymSymExpr>(sym)->getRHS());
488     break;
489   case SymExpr::SymbolCastKind:
490     KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
491     break;
492   }
493 
494   if (KnownLive)
495     markLive(sym);
496 
497   return KnownLive;
498 }
499 
500 bool
isLive(const Stmt * ExprVal,const LocationContext * ELCtx) const501 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
502   if (LCtx == nullptr)
503     return false;
504 
505   if (LCtx != ELCtx) {
506     // If the reaper's location context is a parent of the expression's
507     // location context, then the expression value is now "out of scope".
508     if (LCtx->isParentOf(ELCtx))
509       return false;
510     return true;
511   }
512 
513   // If no statement is provided, everything is this and parent contexts is live.
514   if (!Loc)
515     return true;
516 
517   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
518 }
519 
isLive(const VarRegion * VR,bool includeStoreBindings) const520 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
521   const StackFrameContext *VarContext = VR->getStackFrame();
522 
523   if (!VarContext)
524     return true;
525 
526   if (!LCtx)
527     return false;
528   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
529 
530   if (VarContext == CurrentContext) {
531     // If no statement is provided, everything is live.
532     if (!Loc)
533       return true;
534 
535     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
536       return true;
537 
538     if (!includeStoreBindings)
539       return false;
540 
541     unsigned &cachedQuery =
542       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
543 
544     if (cachedQuery) {
545       return cachedQuery == 1;
546     }
547 
548     // Query the store to see if the region occurs in any live bindings.
549     if (Store store = reapedStore.getStore()) {
550       bool hasRegion =
551         reapedStore.getStoreManager().includedInBindings(store, VR);
552       cachedQuery = hasRegion ? 1 : 2;
553       return hasRegion;
554     }
555 
556     return false;
557   }
558 
559   return VarContext->isParentOf(CurrentContext);
560 }
561