SValBuilder.cpp revision 5251abea41b446c26e3239c8dd6c7edea6fc335d 
1// SValBuilder.cpp - Basic class for all SValBuilder implementations -*- 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 SValBuilder, the base class for all (complete) SValBuilder
11//  implementations.
12//
13//===----------------------------------------------------------------------===//
14
15#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
16#include "clang/AST/DeclCXX.h"
17#include "clang/AST/ExprCXX.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
22
23using namespace clang;
24using namespace ento;
25
26//===----------------------------------------------------------------------===//
27// Basic SVal creation.
28//===----------------------------------------------------------------------===//
29
30void SValBuilder::anchor() { }
31
32DefinedOrUnknownSVal SValBuilder::makeZeroVal(QualType type) {
33  if (Loc::isLocType(type))
34    return makeNull();
35
36  if (type->isIntegerType())
37    return makeIntVal(0, type);
38
39  // FIXME: Handle floats.
40  // FIXME: Handle structs.
41  return UnknownVal();
42}
43
44NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
45                                const llvm::APSInt& rhs, QualType type) {
46  // The Environment ensures we always get a persistent APSInt in
47  // BasicValueFactory, so we don't need to get the APSInt from
48  // BasicValueFactory again.
49  assert(lhs);
50  assert(!Loc::isLocType(type));
51  return nonloc::SymbolVal(SymMgr.getSymIntExpr(lhs, op, rhs, type));
52}
53
54NonLoc SValBuilder::makeNonLoc(const llvm::APSInt& lhs,
55                               BinaryOperator::Opcode op, const SymExpr *rhs,
56                               QualType type) {
57  assert(rhs);
58  assert(!Loc::isLocType(type));
59  return nonloc::SymbolVal(SymMgr.getIntSymExpr(lhs, op, rhs, type));
60}
61
62NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
63                               const SymExpr *rhs, QualType type) {
64  assert(lhs && rhs);
65  assert(!Loc::isLocType(type));
66  return nonloc::SymbolVal(SymMgr.getSymSymExpr(lhs, op, rhs, type));
67}
68
69NonLoc SValBuilder::makeNonLoc(const SymExpr *operand,
70                               QualType fromTy, QualType toTy) {
71  assert(operand);
72  assert(!Loc::isLocType(toTy));
73  return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy));
74}
75
76SVal SValBuilder::convertToArrayIndex(SVal val) {
77  if (val.isUnknownOrUndef())
78    return val;
79
80  // Common case: we have an appropriately sized integer.
81  if (llvm::Optional<nonloc::ConcreteInt> CI =
82          val.getAs<nonloc::ConcreteInt>()) {
83    const llvm::APSInt& I = CI->getValue();
84    if (I.getBitWidth() == ArrayIndexWidth && I.isSigned())
85      return val;
86  }
87
88  return evalCastFromNonLoc(val.castAs<NonLoc>(), ArrayIndexTy);
89}
90
91nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){
92  return makeTruthVal(boolean->getValue());
93}
94
95DefinedOrUnknownSVal
96SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) {
97  QualType T = region->getValueType();
98
99  if (!SymbolManager::canSymbolicate(T))
100    return UnknownVal();
101
102  SymbolRef sym = SymMgr.getRegionValueSymbol(region);
103
104  if (Loc::isLocType(T))
105    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
106
107  return nonloc::SymbolVal(sym);
108}
109
110DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
111                                                   const Expr *expr,
112                                                   const LocationContext *LCtx,
113                                                   unsigned count) {
114  QualType T = expr->getType();
115  return conjureSymbolVal(symbolTag, expr, LCtx, T, count);
116}
117
118DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
119                                                   const Expr *expr,
120                                                   const LocationContext *LCtx,
121                                                   QualType type,
122                                                   unsigned count) {
123  if (!SymbolManager::canSymbolicate(type))
124    return UnknownVal();
125
126  SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
127
128  if (Loc::isLocType(type))
129    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
130
131  return nonloc::SymbolVal(sym);
132}
133
134
135DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
136                                                   const LocationContext *LCtx,
137                                                   QualType type,
138                                                   unsigned visitCount) {
139  if (!SymbolManager::canSymbolicate(type))
140    return UnknownVal();
141
142  SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
143
144  if (Loc::isLocType(type))
145    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
146
147  return nonloc::SymbolVal(sym);
148}
149
150DefinedOrUnknownSVal
151SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
152                                      const LocationContext *LCtx,
153                                      unsigned VisitCount) {
154  QualType T = E->getType();
155  assert(Loc::isLocType(T));
156  assert(SymbolManager::canSymbolicate(T));
157
158  SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
159  return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
160}
161
162DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
163                                              const MemRegion *region,
164                                              const Expr *expr, QualType type,
165                                              unsigned count) {
166  assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
167
168  SymbolRef sym =
169      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
170
171  if (Loc::isLocType(type))
172    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
173
174  return nonloc::SymbolVal(sym);
175}
176
177DefinedOrUnknownSVal
178SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
179                                             const TypedValueRegion *region) {
180  QualType T = region->getValueType();
181
182  if (!SymbolManager::canSymbolicate(T))
183    return UnknownVal();
184
185  SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
186
187  if (Loc::isLocType(T))
188    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
189
190  return nonloc::SymbolVal(sym);
191}
192
193DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
194  return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
195}
196
197DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
198                                         CanQualType locTy,
199                                         const LocationContext *locContext) {
200  const BlockTextRegion *BC =
201    MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
202  const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext);
203  return loc::MemRegionVal(BD);
204}
205
206/// Return a memory region for the 'this' object reference.
207loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
208                                          const StackFrameContext *SFC) {
209  return loc::MemRegionVal(getRegionManager().
210                           getCXXThisRegion(D->getThisType(getContext()), SFC));
211}
212
213/// Return a memory region for the 'this' object reference.
214loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
215                                          const StackFrameContext *SFC) {
216  const Type *T = D->getTypeForDecl();
217  QualType PT = getContext().getPointerType(QualType(T, 0));
218  return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
219}
220
221//===----------------------------------------------------------------------===//
222
223SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
224                                   BinaryOperator::Opcode Op,
225                                   NonLoc LHS, NonLoc RHS,
226                                   QualType ResultTy) {
227  if (!State->isTainted(RHS) && !State->isTainted(LHS))
228    return UnknownVal();
229
230  const SymExpr *symLHS = LHS.getAsSymExpr();
231  const SymExpr *symRHS = RHS.getAsSymExpr();
232  // TODO: When the Max Complexity is reached, we should conjure a symbol
233  // instead of generating an Unknown value and propagate the taint info to it.
234  const unsigned MaxComp = 10000; // 100000 28X
235
236  if (symLHS && symRHS &&
237      (symLHS->computeComplexity() + symRHS->computeComplexity()) <  MaxComp)
238    return makeNonLoc(symLHS, Op, symRHS, ResultTy);
239
240  if (symLHS && symLHS->computeComplexity() < MaxComp)
241    if (llvm::Optional<nonloc::ConcreteInt> rInt =
242            RHS.getAs<nonloc::ConcreteInt>())
243      return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
244
245  if (symRHS && symRHS->computeComplexity() < MaxComp)
246    if (llvm::Optional<nonloc::ConcreteInt> lInt =
247            LHS.getAs<nonloc::ConcreteInt>())
248      return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
249
250  return UnknownVal();
251}
252
253
254SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
255                            SVal lhs, SVal rhs, QualType type) {
256
257  if (lhs.isUndef() || rhs.isUndef())
258    return UndefinedVal();
259
260  if (lhs.isUnknown() || rhs.isUnknown())
261    return UnknownVal();
262
263  if (llvm::Optional<Loc> LV = lhs.getAs<Loc>()) {
264    if (llvm::Optional<Loc> RV = rhs.getAs<Loc>())
265      return evalBinOpLL(state, op, *LV, *RV, type);
266
267    return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
268  }
269
270  if (llvm::Optional<Loc> RV = rhs.getAs<Loc>()) {
271    // Support pointer arithmetic where the addend is on the left
272    // and the pointer on the right.
273    assert(op == BO_Add);
274
275    // Commute the operands.
276    return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
277  }
278
279  return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
280                     type);
281}
282
283DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
284                                         DefinedOrUnknownSVal lhs,
285                                         DefinedOrUnknownSVal rhs) {
286  return evalBinOp(state, BO_EQ, lhs, rhs, Context.IntTy)
287      .castAs<DefinedOrUnknownSVal>();
288}
289
290/// Recursively check if the pointer types are equal modulo const, volatile,
291/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
292/// Assumes the input types are canonical.
293static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
294                                                         QualType FromTy) {
295  while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
296    Qualifiers Quals1, Quals2;
297    ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
298    FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
299
300    // Make sure that non cvr-qualifiers the other qualifiers (e.g., address
301    // spaces) are identical.
302    Quals1.removeCVRQualifiers();
303    Quals2.removeCVRQualifiers();
304    if (Quals1 != Quals2)
305      return false;
306  }
307
308  // If we are casting to void, the 'From' value can be used to represent the
309  // 'To' value.
310  if (ToTy->isVoidType())
311    return true;
312
313  if (ToTy != FromTy)
314    return false;
315
316  return true;
317}
318
319// FIXME: should rewrite according to the cast kind.
320SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
321  castTy = Context.getCanonicalType(castTy);
322  originalTy = Context.getCanonicalType(originalTy);
323  if (val.isUnknownOrUndef() || castTy == originalTy)
324    return val;
325
326  // For const casts, casts to void, just propagate the value.
327  if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
328    if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
329                                         Context.getPointerType(originalTy)))
330      return val;
331
332  // Check for casts from pointers to integers.
333  if (castTy->isIntegerType() && Loc::isLocType(originalTy))
334    return evalCastFromLoc(val.castAs<Loc>(), castTy);
335
336  // Check for casts from integers to pointers.
337  if (Loc::isLocType(castTy) && originalTy->isIntegerType()) {
338    if (llvm::Optional<nonloc::LocAsInteger> LV =
339            val.getAs<nonloc::LocAsInteger>()) {
340      if (const MemRegion *R = LV->getLoc().getAsRegion()) {
341        StoreManager &storeMgr = StateMgr.getStoreManager();
342        R = storeMgr.castRegion(R, castTy);
343        return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
344      }
345      return LV->getLoc();
346    }
347    return dispatchCast(val, castTy);
348  }
349
350  // Just pass through function and block pointers.
351  if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
352    assert(Loc::isLocType(castTy));
353    return val;
354  }
355
356  // Check for casts from array type to another type.
357  if (originalTy->isArrayType()) {
358    // We will always decay to a pointer.
359    val = StateMgr.ArrayToPointer(val.castAs<Loc>());
360
361    // Are we casting from an array to a pointer?  If so just pass on
362    // the decayed value.
363    if (castTy->isPointerType() || castTy->isReferenceType())
364      return val;
365
366    // Are we casting from an array to an integer?  If so, cast the decayed
367    // pointer value to an integer.
368    assert(castTy->isIntegerType());
369
370    // FIXME: Keep these here for now in case we decide soon that we
371    // need the original decayed type.
372    //    QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
373    //    QualType pointerTy = C.getPointerType(elemTy);
374    return evalCastFromLoc(val.castAs<Loc>(), castTy);
375  }
376
377  // Check for casts from a region to a specific type.
378  if (const MemRegion *R = val.getAsRegion()) {
379    // Handle other casts of locations to integers.
380    if (castTy->isIntegerType())
381      return evalCastFromLoc(loc::MemRegionVal(R), castTy);
382
383    // FIXME: We should handle the case where we strip off view layers to get
384    //  to a desugared type.
385    if (!Loc::isLocType(castTy)) {
386      // FIXME: There can be gross cases where one casts the result of a function
387      // (that returns a pointer) to some other value that happens to fit
388      // within that pointer value.  We currently have no good way to
389      // model such operations.  When this happens, the underlying operation
390      // is that the caller is reasoning about bits.  Conceptually we are
391      // layering a "view" of a location on top of those bits.  Perhaps
392      // we need to be more lazy about mutual possible views, even on an
393      // SVal?  This may be necessary for bit-level reasoning as well.
394      return UnknownVal();
395    }
396
397    // We get a symbolic function pointer for a dereference of a function
398    // pointer, but it is of function type. Example:
399
400    //  struct FPRec {
401    //    void (*my_func)(int * x);
402    //  };
403    //
404    //  int bar(int x);
405    //
406    //  int f1_a(struct FPRec* foo) {
407    //    int x;
408    //    (*foo->my_func)(&x);
409    //    return bar(x)+1; // no-warning
410    //  }
411
412    assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
413           originalTy->isBlockPointerType() || castTy->isReferenceType());
414
415    StoreManager &storeMgr = StateMgr.getStoreManager();
416
417    // Delegate to store manager to get the result of casting a region to a
418    // different type.  If the MemRegion* returned is NULL, this expression
419    // Evaluates to UnknownVal.
420    R = storeMgr.castRegion(R, castTy);
421    return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
422  }
423
424  return dispatchCast(val, castTy);
425}
426