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::dump() const {
25   dumpToStream(llvm::errs());
26 }
27 
28 static void print(raw_ostream &os, BinaryOperator::Opcode Op) {
29   switch (Op) {
30     default:
31       llvm_unreachable("operator printing not implemented");
32     case BO_Mul: os << '*'  ; break;
33     case BO_Div: os << '/'  ; break;
34     case BO_Rem: os << '%'  ; break;
35     case BO_Add: os << '+'  ; break;
36     case BO_Sub: os << '-'  ; break;
37     case BO_Shl: os << "<<" ; break;
38     case BO_Shr: os << ">>" ; break;
39     case BO_LT:  os << "<"  ; break;
40     case BO_GT:  os << '>'  ; break;
41     case BO_LE:  os << "<=" ; break;
42     case BO_GE:  os << ">=" ; break;
43     case BO_EQ:  os << "==" ; break;
44     case BO_NE:  os << "!=" ; break;
45     case BO_And: os << '&'  ; break;
46     case BO_Xor: os << '^'  ; break;
47     case BO_Or:  os << '|'  ; break;
48   }
49 }
50 
51 void SymIntExpr::dumpToStream(raw_ostream &os) const {
52   os << '(';
53   getLHS()->dumpToStream(os);
54   os << ") ";
55   print(os, getOpcode());
56   os << ' ' << getRHS().getZExtValue();
57   if (getRHS().isUnsigned()) os << 'U';
58 }
59 
60 void SymSymExpr::dumpToStream(raw_ostream &os) const {
61   os << '(';
62   getLHS()->dumpToStream(os);
63   os << ") ";
64   os << '(';
65   getRHS()->dumpToStream(os);
66   os << ')';
67 }
68 
69 void SymbolCast::dumpToStream(raw_ostream &os) const {
70   os << '(' << ToTy.getAsString() << ") (";
71   Operand->dumpToStream(os);
72   os << ')';
73 }
74 
75 void SymbolConjured::dumpToStream(raw_ostream &os) const {
76   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
77 }
78 
79 void SymbolDerived::dumpToStream(raw_ostream &os) const {
80   os << "derived_$" << getSymbolID() << '{'
81      << getParentSymbol() << ',' << getRegion() << '}';
82 }
83 
84 void SymbolExtent::dumpToStream(raw_ostream &os) const {
85   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
86 }
87 
88 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
89   os << "meta_$" << getSymbolID() << '{'
90      << getRegion() << ',' << T.getAsString() << '}';
91 }
92 
93 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
94   os << "reg_$" << getSymbolID() << "<" << R << ">";
95 }
96 
97 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
98   return itr == X.itr;
99 }
100 
101 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
102   return itr != X.itr;
103 }
104 
105 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
106   itr.push_back(SE);
107   while (!isa<SymbolData>(itr.back())) expand();
108 }
109 
110 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
111   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
112   assert(isa<SymbolData>(itr.back()));
113   itr.pop_back();
114   if (!itr.empty())
115     while (!isa<SymbolData>(itr.back())) expand();
116   return *this;
117 }
118 
119 SymbolRef SymExpr::symbol_iterator::operator*() {
120   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
121   return cast<SymbolData>(itr.back());
122 }
123 
124 void SymExpr::symbol_iterator::expand() {
125   const SymExpr *SE = itr.back();
126   itr.pop_back();
127 
128   if (const SymbolCast *SC = dyn_cast<SymbolCast>(SE)) {
129     itr.push_back(SC->getOperand());
130     return;
131   }
132   if (const SymIntExpr *SIE = dyn_cast<SymIntExpr>(SE)) {
133     itr.push_back(SIE->getLHS());
134     return;
135   }
136   else if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(SE)) {
137     itr.push_back(SSE->getLHS());
138     itr.push_back(SSE->getRHS());
139     return;
140   }
141 
142   llvm_unreachable("unhandled expansion case");
143 }
144 
145 const SymbolRegionValue*
146 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
147   llvm::FoldingSetNodeID profile;
148   SymbolRegionValue::Profile(profile, R);
149   void *InsertPos;
150   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
151   if (!SD) {
152     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
153     new (SD) SymbolRegionValue(SymbolCounter, R);
154     DataSet.InsertNode(SD, InsertPos);
155     ++SymbolCounter;
156   }
157 
158   return cast<SymbolRegionValue>(SD);
159 }
160 
161 const SymbolConjured*
162 SymbolManager::getConjuredSymbol(const Stmt *E, QualType T, unsigned Count,
163                                  const void *SymbolTag) {
164 
165   llvm::FoldingSetNodeID profile;
166   SymbolConjured::Profile(profile, E, T, Count, SymbolTag);
167   void *InsertPos;
168   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
169   if (!SD) {
170     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
171     new (SD) SymbolConjured(SymbolCounter, E, T, Count, SymbolTag);
172     DataSet.InsertNode(SD, InsertPos);
173     ++SymbolCounter;
174   }
175 
176   return cast<SymbolConjured>(SD);
177 }
178 
179 const SymbolDerived*
180 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
181                                 const TypedValueRegion *R) {
182 
183   llvm::FoldingSetNodeID profile;
184   SymbolDerived::Profile(profile, parentSymbol, R);
185   void *InsertPos;
186   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
187   if (!SD) {
188     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
189     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
190     DataSet.InsertNode(SD, InsertPos);
191     ++SymbolCounter;
192   }
193 
194   return cast<SymbolDerived>(SD);
195 }
196 
197 const SymbolExtent*
198 SymbolManager::getExtentSymbol(const SubRegion *R) {
199   llvm::FoldingSetNodeID profile;
200   SymbolExtent::Profile(profile, R);
201   void *InsertPos;
202   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
203   if (!SD) {
204     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
205     new (SD) SymbolExtent(SymbolCounter, R);
206     DataSet.InsertNode(SD, InsertPos);
207     ++SymbolCounter;
208   }
209 
210   return cast<SymbolExtent>(SD);
211 }
212 
213 const SymbolMetadata*
214 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
215                                  unsigned Count, const void *SymbolTag) {
216 
217   llvm::FoldingSetNodeID profile;
218   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
219   void *InsertPos;
220   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
221   if (!SD) {
222     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
223     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
224     DataSet.InsertNode(SD, InsertPos);
225     ++SymbolCounter;
226   }
227 
228   return cast<SymbolMetadata>(SD);
229 }
230 
231 const SymbolCast*
232 SymbolManager::getCastSymbol(const SymExpr *Op,
233                              QualType From, QualType To) {
234   llvm::FoldingSetNodeID ID;
235   SymbolCast::Profile(ID, Op, From, To);
236   void *InsertPos;
237   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
238   if (!data) {
239     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
240     new (data) SymbolCast(Op, From, To);
241     DataSet.InsertNode(data, InsertPos);
242   }
243 
244   return cast<SymbolCast>(data);
245 }
246 
247 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
248                                                BinaryOperator::Opcode op,
249                                                const llvm::APSInt& v,
250                                                QualType t) {
251   llvm::FoldingSetNodeID ID;
252   SymIntExpr::Profile(ID, lhs, op, v, t);
253   void *InsertPos;
254   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
255 
256   if (!data) {
257     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
258     new (data) SymIntExpr(lhs, op, v, t);
259     DataSet.InsertNode(data, InsertPos);
260   }
261 
262   return cast<SymIntExpr>(data);
263 }
264 
265 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
266                                                BinaryOperator::Opcode op,
267                                                const SymExpr *rhs,
268                                                QualType t) {
269   llvm::FoldingSetNodeID ID;
270   SymSymExpr::Profile(ID, lhs, op, rhs, t);
271   void *InsertPos;
272   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
273 
274   if (!data) {
275     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
276     new (data) SymSymExpr(lhs, op, rhs, t);
277     DataSet.InsertNode(data, InsertPos);
278   }
279 
280   return cast<SymSymExpr>(data);
281 }
282 
283 QualType SymbolConjured::getType(ASTContext&) const {
284   return T;
285 }
286 
287 QualType SymbolDerived::getType(ASTContext &Ctx) const {
288   return R->getValueType();
289 }
290 
291 QualType SymbolExtent::getType(ASTContext &Ctx) const {
292   return Ctx.getSizeType();
293 }
294 
295 QualType SymbolMetadata::getType(ASTContext&) const {
296   return T;
297 }
298 
299 QualType SymbolRegionValue::getType(ASTContext &C) const {
300   return R->getValueType();
301 }
302 
303 SymbolManager::~SymbolManager() {
304   for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
305        E = SymbolDependencies.end(); I != E; ++I) {
306     delete I->second;
307   }
308 
309 }
310 
311 bool SymbolManager::canSymbolicate(QualType T) {
312   T = T.getCanonicalType();
313 
314   if (Loc::isLocType(T))
315     return true;
316 
317   if (T->isIntegerType())
318     return T->isScalarType();
319 
320   if (T->isRecordType() && !T->isUnionType())
321     return true;
322 
323   return false;
324 }
325 
326 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
327                                         const SymbolRef Dependent) {
328   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
329   SymbolRefSmallVectorTy *dependencies = 0;
330   if (I == SymbolDependencies.end()) {
331     dependencies = new SymbolRefSmallVectorTy();
332     SymbolDependencies[Primary] = dependencies;
333   } else {
334     dependencies = I->second;
335   }
336   dependencies->push_back(Dependent);
337 }
338 
339 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
340                                                      const SymbolRef Primary) {
341   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
342   if (I == SymbolDependencies.end())
343     return 0;
344   return I->second;
345 }
346 
347 void SymbolReaper::markDependentsLive(SymbolRef sym) {
348   // Do not mark dependents more then once.
349   SymbolMapTy::iterator LI = TheLiving.find(sym);
350   assert(LI != TheLiving.end() && "The primary symbol is not live.");
351   if (LI->second == HaveMarkedDependents)
352     return;
353   LI->second = HaveMarkedDependents;
354 
355   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
356     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
357                                                 E = Deps->end(); I != E; ++I) {
358       if (TheLiving.find(*I) != TheLiving.end())
359         continue;
360       markLive(*I);
361     }
362   }
363 }
364 
365 void SymbolReaper::markLive(SymbolRef sym) {
366   TheLiving[sym] = NotProcessed;
367   TheDead.erase(sym);
368   markDependentsLive(sym);
369 }
370 
371 void SymbolReaper::markLive(const MemRegion *region) {
372   RegionRoots.insert(region);
373 }
374 
375 void SymbolReaper::markInUse(SymbolRef sym) {
376   if (isa<SymbolMetadata>(sym))
377     MetadataInUse.insert(sym);
378 }
379 
380 bool SymbolReaper::maybeDead(SymbolRef sym) {
381   if (isLive(sym))
382     return false;
383 
384   TheDead.insert(sym);
385   return true;
386 }
387 
388 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
389   if (RegionRoots.count(MR))
390     return true;
391 
392   MR = MR->getBaseRegion();
393 
394   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
395     return isLive(SR->getSymbol());
396 
397   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
398     return isLive(VR, true);
399 
400   // FIXME: This is a gross over-approximation. What we really need is a way to
401   // tell if anything still refers to this region. Unlike SymbolicRegions,
402   // AllocaRegions don't have associated symbols, though, so we don't actually
403   // have a way to track their liveness.
404   if (isa<AllocaRegion>(MR))
405     return true;
406 
407   if (isa<CXXThisRegion>(MR))
408     return true;
409 
410   if (isa<MemSpaceRegion>(MR))
411     return true;
412 
413   return false;
414 }
415 
416 bool SymbolReaper::isLive(SymbolRef sym) {
417   if (TheLiving.count(sym)) {
418     markDependentsLive(sym);
419     return true;
420   }
421 
422   if (const SymbolDerived *derived = dyn_cast<SymbolDerived>(sym)) {
423     if (isLive(derived->getParentSymbol())) {
424       markLive(sym);
425       return true;
426     }
427     return false;
428   }
429 
430   if (const SymbolExtent *extent = dyn_cast<SymbolExtent>(sym)) {
431     if (isLiveRegion(extent->getRegion())) {
432       markLive(sym);
433       return true;
434     }
435     return false;
436   }
437 
438   if (const SymbolMetadata *metadata = dyn_cast<SymbolMetadata>(sym)) {
439     if (MetadataInUse.count(sym)) {
440       if (isLiveRegion(metadata->getRegion())) {
441         markLive(sym);
442         MetadataInUse.erase(sym);
443         return true;
444       }
445     }
446     return false;
447   }
448 
449   // Interogate the symbol.  It may derive from an input value to
450   // the analyzed function/method.
451   return isa<SymbolRegionValue>(sym);
452 }
453 
454 bool SymbolReaper::isLive(const Stmt *ExprVal) const {
455   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
456 }
457 
458 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
459   const StackFrameContext *VarContext = VR->getStackFrame();
460   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
461 
462   if (VarContext == CurrentContext) {
463     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
464       return true;
465 
466     if (!includeStoreBindings)
467       return false;
468 
469     unsigned &cachedQuery =
470       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
471 
472     if (cachedQuery) {
473       return cachedQuery == 1;
474     }
475 
476     // Query the store to see if the region occurs in any live bindings.
477     if (Store store = reapedStore.getStore()) {
478       bool hasRegion =
479         reapedStore.getStoreManager().includedInBindings(store, VR);
480       cachedQuery = hasRegion ? 1 : 2;
481       return hasRegion;
482     }
483 
484     return false;
485   }
486 
487   return VarContext->isParentOf(CurrentContext);
488 }
489 
490 SymbolVisitor::~SymbolVisitor() {}
491