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