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()
89      << '<' << getType().getAsString() << ' ' << R << '>';
90 }
91 
92 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
93   return itr == X.itr;
94 }
95 
96 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
97   return itr != X.itr;
98 }
99 
100 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
101   itr.push_back(SE);
102 }
103 
104 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
105   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
106   expand();
107   return *this;
108 }
109 
110 SymbolRef SymExpr::symbol_iterator::operator*() {
111   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
112   return itr.back();
113 }
114 
115 void SymExpr::symbol_iterator::expand() {
116   const SymExpr *SE = itr.pop_back_val();
117 
118   switch (SE->getKind()) {
119     case SymExpr::SymbolRegionValueKind:
120     case SymExpr::SymbolConjuredKind:
121     case SymExpr::SymbolDerivedKind:
122     case SymExpr::SymbolExtentKind:
123     case SymExpr::SymbolMetadataKind:
124       return;
125     case SymExpr::SymbolCastKind:
126       itr.push_back(cast<SymbolCast>(SE)->getOperand());
127       return;
128     case SymExpr::SymIntExprKind:
129       itr.push_back(cast<SymIntExpr>(SE)->getLHS());
130       return;
131     case SymExpr::IntSymExprKind:
132       itr.push_back(cast<IntSymExpr>(SE)->getRHS());
133       return;
134     case SymExpr::SymSymExprKind: {
135       const SymSymExpr *x = cast<SymSymExpr>(SE);
136       itr.push_back(x->getLHS());
137       itr.push_back(x->getRHS());
138       return;
139     }
140   }
141   llvm_unreachable("unhandled expansion case");
142 }
143 
144 unsigned SymExpr::computeComplexity() const {
145   unsigned R = 0;
146   for (symbol_iterator I = symbol_begin(), E = symbol_end(); I != E; ++I)
147     R++;
148   return R;
149 }
150 
151 const SymbolRegionValue*
152 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
153   llvm::FoldingSetNodeID profile;
154   SymbolRegionValue::Profile(profile, R);
155   void *InsertPos;
156   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
157   if (!SD) {
158     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
159     new (SD) SymbolRegionValue(SymbolCounter, R);
160     DataSet.InsertNode(SD, InsertPos);
161     ++SymbolCounter;
162   }
163 
164   return cast<SymbolRegionValue>(SD);
165 }
166 
167 const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
168                                                    const LocationContext *LCtx,
169                                                    QualType T,
170                                                    unsigned Count,
171                                                    const void *SymbolTag) {
172   llvm::FoldingSetNodeID profile;
173   SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
174   void *InsertPos;
175   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
176   if (!SD) {
177     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
178     new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
179     DataSet.InsertNode(SD, InsertPos);
180     ++SymbolCounter;
181   }
182 
183   return cast<SymbolConjured>(SD);
184 }
185 
186 const SymbolDerived*
187 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
188                                 const TypedValueRegion *R) {
189 
190   llvm::FoldingSetNodeID profile;
191   SymbolDerived::Profile(profile, parentSymbol, R);
192   void *InsertPos;
193   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
194   if (!SD) {
195     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
196     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
197     DataSet.InsertNode(SD, InsertPos);
198     ++SymbolCounter;
199   }
200 
201   return cast<SymbolDerived>(SD);
202 }
203 
204 const SymbolExtent*
205 SymbolManager::getExtentSymbol(const SubRegion *R) {
206   llvm::FoldingSetNodeID profile;
207   SymbolExtent::Profile(profile, R);
208   void *InsertPos;
209   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
210   if (!SD) {
211     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
212     new (SD) SymbolExtent(SymbolCounter, R);
213     DataSet.InsertNode(SD, InsertPos);
214     ++SymbolCounter;
215   }
216 
217   return cast<SymbolExtent>(SD);
218 }
219 
220 const SymbolMetadata *
221 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
222                                  const LocationContext *LCtx,
223                                  unsigned Count, const void *SymbolTag) {
224 
225   llvm::FoldingSetNodeID profile;
226   SymbolMetadata::Profile(profile, R, S, T, LCtx, Count, SymbolTag);
227   void *InsertPos;
228   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
229   if (!SD) {
230     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
231     new (SD) SymbolMetadata(SymbolCounter, R, S, T, LCtx, Count, SymbolTag);
232     DataSet.InsertNode(SD, InsertPos);
233     ++SymbolCounter;
234   }
235 
236   return cast<SymbolMetadata>(SD);
237 }
238 
239 const SymbolCast*
240 SymbolManager::getCastSymbol(const SymExpr *Op,
241                              QualType From, QualType To) {
242   llvm::FoldingSetNodeID ID;
243   SymbolCast::Profile(ID, Op, From, To);
244   void *InsertPos;
245   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
246   if (!data) {
247     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
248     new (data) SymbolCast(Op, From, To);
249     DataSet.InsertNode(data, InsertPos);
250   }
251 
252   return cast<SymbolCast>(data);
253 }
254 
255 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
256                                                BinaryOperator::Opcode op,
257                                                const llvm::APSInt& v,
258                                                QualType t) {
259   llvm::FoldingSetNodeID ID;
260   SymIntExpr::Profile(ID, lhs, op, v, t);
261   void *InsertPos;
262   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
263 
264   if (!data) {
265     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
266     new (data) SymIntExpr(lhs, op, v, t);
267     DataSet.InsertNode(data, InsertPos);
268   }
269 
270   return cast<SymIntExpr>(data);
271 }
272 
273 const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
274                                                BinaryOperator::Opcode op,
275                                                const SymExpr *rhs,
276                                                QualType t) {
277   llvm::FoldingSetNodeID ID;
278   IntSymExpr::Profile(ID, lhs, op, rhs, t);
279   void *InsertPos;
280   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
281 
282   if (!data) {
283     data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
284     new (data) IntSymExpr(lhs, op, rhs, t);
285     DataSet.InsertNode(data, InsertPos);
286   }
287 
288   return cast<IntSymExpr>(data);
289 }
290 
291 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
292                                                BinaryOperator::Opcode op,
293                                                const SymExpr *rhs,
294                                                QualType t) {
295   llvm::FoldingSetNodeID ID;
296   SymSymExpr::Profile(ID, lhs, op, rhs, t);
297   void *InsertPos;
298   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
299 
300   if (!data) {
301     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
302     new (data) SymSymExpr(lhs, op, rhs, t);
303     DataSet.InsertNode(data, InsertPos);
304   }
305 
306   return cast<SymSymExpr>(data);
307 }
308 
309 QualType SymbolConjured::getType() const {
310   return T;
311 }
312 
313 QualType SymbolDerived::getType() const {
314   return R->getValueType();
315 }
316 
317 QualType SymbolExtent::getType() const {
318   ASTContext &Ctx = R->getMemRegionManager()->getContext();
319   return Ctx.getSizeType();
320 }
321 
322 QualType SymbolMetadata::getType() const {
323   return T;
324 }
325 
326 QualType SymbolRegionValue::getType() const {
327   return R->getValueType();
328 }
329 
330 SymbolManager::~SymbolManager() {
331   llvm::DeleteContainerSeconds(SymbolDependencies);
332 }
333 
334 bool SymbolManager::canSymbolicate(QualType T) {
335   T = T.getCanonicalType();
336 
337   if (Loc::isLocType(T))
338     return true;
339 
340   if (T->isIntegralOrEnumerationType())
341     return true;
342 
343   if (T->isRecordType() && !T->isUnionType())
344     return true;
345 
346   return false;
347 }
348 
349 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
350                                         const SymbolRef Dependent) {
351   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
352   SymbolRefSmallVectorTy *dependencies = nullptr;
353   if (I == SymbolDependencies.end()) {
354     dependencies = new SymbolRefSmallVectorTy();
355     SymbolDependencies[Primary] = dependencies;
356   } else {
357     dependencies = I->second;
358   }
359   dependencies->push_back(Dependent);
360 }
361 
362 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
363                                                      const SymbolRef Primary) {
364   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
365   if (I == SymbolDependencies.end())
366     return nullptr;
367   return I->second;
368 }
369 
370 void SymbolReaper::markDependentsLive(SymbolRef sym) {
371   // Do not mark dependents more then once.
372   SymbolMapTy::iterator LI = TheLiving.find(sym);
373   assert(LI != TheLiving.end() && "The primary symbol is not live.");
374   if (LI->second == HaveMarkedDependents)
375     return;
376   LI->second = HaveMarkedDependents;
377 
378   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
379     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
380                                                 E = Deps->end(); I != E; ++I) {
381       if (TheLiving.find(*I) != TheLiving.end())
382         continue;
383       markLive(*I);
384     }
385   }
386 }
387 
388 void SymbolReaper::markLive(SymbolRef sym) {
389   TheLiving[sym] = NotProcessed;
390   TheDead.erase(sym);
391   markDependentsLive(sym);
392 }
393 
394 void SymbolReaper::markLive(const MemRegion *region) {
395   RegionRoots.insert(region);
396   markElementIndicesLive(region);
397 }
398 
399 void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
400   for (auto SR = dyn_cast<SubRegion>(region); SR;
401        SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
402     if (auto ER = dyn_cast<ElementRegion>(SR)) {
403       SVal Idx = ER->getIndex();
404       for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
405         markLive(*SI);
406     }
407   }
408 }
409 
410 void SymbolReaper::markInUse(SymbolRef sym) {
411   if (isa<SymbolMetadata>(sym))
412     MetadataInUse.insert(sym);
413 }
414 
415 bool SymbolReaper::maybeDead(SymbolRef sym) {
416   if (isLive(sym))
417     return false;
418 
419   TheDead.insert(sym);
420   return true;
421 }
422 
423 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
424   if (RegionRoots.count(MR))
425     return true;
426 
427   MR = MR->getBaseRegion();
428 
429   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
430     return isLive(SR->getSymbol());
431 
432   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
433     return isLive(VR, true);
434 
435   // FIXME: This is a gross over-approximation. What we really need is a way to
436   // tell if anything still refers to this region. Unlike SymbolicRegions,
437   // AllocaRegions don't have associated symbols, though, so we don't actually
438   // have a way to track their liveness.
439   if (isa<AllocaRegion>(MR))
440     return true;
441 
442   if (isa<CXXThisRegion>(MR))
443     return true;
444 
445   if (isa<MemSpaceRegion>(MR))
446     return true;
447 
448   if (isa<CodeTextRegion>(MR))
449     return true;
450 
451   return false;
452 }
453 
454 bool SymbolReaper::isLive(SymbolRef sym) {
455   if (TheLiving.count(sym)) {
456     markDependentsLive(sym);
457     return true;
458   }
459 
460   bool KnownLive;
461 
462   switch (sym->getKind()) {
463   case SymExpr::SymbolRegionValueKind:
464     KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
465     break;
466   case SymExpr::SymbolConjuredKind:
467     KnownLive = false;
468     break;
469   case SymExpr::SymbolDerivedKind:
470     KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
471     break;
472   case SymExpr::SymbolExtentKind:
473     KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
474     break;
475   case SymExpr::SymbolMetadataKind:
476     KnownLive = MetadataInUse.count(sym) &&
477                 isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
478     if (KnownLive)
479       MetadataInUse.erase(sym);
480     break;
481   case SymExpr::SymIntExprKind:
482     KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
483     break;
484   case SymExpr::IntSymExprKind:
485     KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
486     break;
487   case SymExpr::SymSymExprKind:
488     KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
489                 isLive(cast<SymSymExpr>(sym)->getRHS());
490     break;
491   case SymExpr::SymbolCastKind:
492     KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
493     break;
494   }
495 
496   if (KnownLive)
497     markLive(sym);
498 
499   return KnownLive;
500 }
501 
502 bool
503 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
504   if (LCtx == nullptr)
505     return false;
506 
507   if (LCtx != ELCtx) {
508     // If the reaper's location context is a parent of the expression's
509     // location context, then the expression value is now "out of scope".
510     if (LCtx->isParentOf(ELCtx))
511       return false;
512     return true;
513   }
514 
515   // If no statement is provided, everything is this and parent contexts is live.
516   if (!Loc)
517     return true;
518 
519   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
520 }
521 
522 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
523   const StackFrameContext *VarContext = VR->getStackFrame();
524 
525   if (!VarContext)
526     return true;
527 
528   if (!LCtx)
529     return false;
530   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
531 
532   if (VarContext == CurrentContext) {
533     // If no statement is provided, everything is live.
534     if (!Loc)
535       return true;
536 
537     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
538       return true;
539 
540     if (!includeStoreBindings)
541       return false;
542 
543     unsigned &cachedQuery =
544       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
545 
546     if (cachedQuery) {
547       return cachedQuery == 1;
548     }
549 
550     // Query the store to see if the region occurs in any live bindings.
551     if (Store store = reapedStore.getStore()) {
552       bool hasRegion =
553         reapedStore.getStoreManager().includedInBindings(store, VR);
554       cachedQuery = hasRegion ? 1 : 2;
555       return hasRegion;
556     }
557 
558     return false;
559   }
560 
561   return VarContext->isParentOf(CurrentContext);
562 }
563