SValBuilder.cpp revision 112344ab7f96cf482bce80530676712c282756d5 
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->isIntegralOrEnumerationType())
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 (Optional<nonloc::ConcreteInt> CI = val.getAs<nonloc::ConcreteInt>()) {
82    const llvm::APSInt& I = CI->getValue();
83    if (I.getBitWidth() == ArrayIndexWidth && I.isSigned())
84      return val;
85  }
86
87  return evalCastFromNonLoc(val.castAs<NonLoc>(), ArrayIndexTy);
88}
89
90nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){
91  return makeTruthVal(boolean->getValue());
92}
93
94DefinedOrUnknownSVal
95SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) {
96  QualType T = region->getValueType();
97
98  if (!SymbolManager::canSymbolicate(T))
99    return UnknownVal();
100
101  SymbolRef sym = SymMgr.getRegionValueSymbol(region);
102
103  if (Loc::isLocType(T))
104    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
105
106  return nonloc::SymbolVal(sym);
107}
108
109DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *SymbolTag,
110                                                   const Expr *Ex,
111                                                   const LocationContext *LCtx,
112                                                   unsigned Count) {
113  QualType T = Ex->getType();
114
115  // Compute the type of the result. If the expression is not an R-value, the
116  // result should be a location.
117  QualType ExType = Ex->getType();
118  if (Ex->isGLValue())
119    T = LCtx->getAnalysisDeclContext()->getASTContext().getPointerType(ExType);
120
121  return conjureSymbolVal(SymbolTag, Ex, LCtx, T, Count);
122}
123
124DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
125                                                   const Expr *expr,
126                                                   const LocationContext *LCtx,
127                                                   QualType type,
128                                                   unsigned count) {
129  if (!SymbolManager::canSymbolicate(type))
130    return UnknownVal();
131
132  SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
133
134  if (Loc::isLocType(type))
135    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
136
137  return nonloc::SymbolVal(sym);
138}
139
140
141DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
142                                                   const LocationContext *LCtx,
143                                                   QualType type,
144                                                   unsigned visitCount) {
145  if (!SymbolManager::canSymbolicate(type))
146    return UnknownVal();
147
148  SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
149
150  if (Loc::isLocType(type))
151    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
152
153  return nonloc::SymbolVal(sym);
154}
155
156DefinedOrUnknownSVal
157SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
158                                      const LocationContext *LCtx,
159                                      unsigned VisitCount) {
160  QualType T = E->getType();
161  assert(Loc::isLocType(T));
162  assert(SymbolManager::canSymbolicate(T));
163
164  SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
165  return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
166}
167
168DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
169                                              const MemRegion *region,
170                                              const Expr *expr, QualType type,
171                                              unsigned count) {
172  assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
173
174  SymbolRef sym =
175      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
176
177  if (Loc::isLocType(type))
178    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
179
180  return nonloc::SymbolVal(sym);
181}
182
183DefinedOrUnknownSVal
184SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
185                                             const TypedValueRegion *region) {
186  QualType T = region->getValueType();
187
188  if (!SymbolManager::canSymbolicate(T))
189    return UnknownVal();
190
191  SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
192
193  if (Loc::isLocType(T))
194    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
195
196  return nonloc::SymbolVal(sym);
197}
198
199DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
200  return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
201}
202
203DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
204                                         CanQualType locTy,
205                                         const LocationContext *locContext) {
206  const BlockTextRegion *BC =
207    MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
208  const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext);
209  return loc::MemRegionVal(BD);
210}
211
212/// Return a memory region for the 'this' object reference.
213loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
214                                          const StackFrameContext *SFC) {
215  return loc::MemRegionVal(getRegionManager().
216                           getCXXThisRegion(D->getThisType(getContext()), SFC));
217}
218
219/// Return a memory region for the 'this' object reference.
220loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
221                                          const StackFrameContext *SFC) {
222  const Type *T = D->getTypeForDecl();
223  QualType PT = getContext().getPointerType(QualType(T, 0));
224  return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
225}
226
227//===----------------------------------------------------------------------===//
228
229SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
230                                   BinaryOperator::Opcode Op,
231                                   NonLoc LHS, NonLoc RHS,
232                                   QualType ResultTy) {
233  if (!State->isTainted(RHS) && !State->isTainted(LHS))
234    return UnknownVal();
235
236  const SymExpr *symLHS = LHS.getAsSymExpr();
237  const SymExpr *symRHS = RHS.getAsSymExpr();
238  // TODO: When the Max Complexity is reached, we should conjure a symbol
239  // instead of generating an Unknown value and propagate the taint info to it.
240  const unsigned MaxComp = 10000; // 100000 28X
241
242  if (symLHS && symRHS &&
243      (symLHS->computeComplexity() + symRHS->computeComplexity()) <  MaxComp)
244    return makeNonLoc(symLHS, Op, symRHS, ResultTy);
245
246  if (symLHS && symLHS->computeComplexity() < MaxComp)
247    if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>())
248      return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
249
250  if (symRHS && symRHS->computeComplexity() < MaxComp)
251    if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>())
252      return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
253
254  return UnknownVal();
255}
256
257
258SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
259                            SVal lhs, SVal rhs, QualType type) {
260
261  if (lhs.isUndef() || rhs.isUndef())
262    return UndefinedVal();
263
264  if (lhs.isUnknown() || rhs.isUnknown())
265    return UnknownVal();
266
267  if (Optional<Loc> LV = lhs.getAs<Loc>()) {
268    if (Optional<Loc> RV = rhs.getAs<Loc>())
269      return evalBinOpLL(state, op, *LV, *RV, type);
270
271    return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
272  }
273
274  if (Optional<Loc> RV = rhs.getAs<Loc>()) {
275    // Support pointer arithmetic where the addend is on the left
276    // and the pointer on the right.
277    assert(op == BO_Add);
278
279    // Commute the operands.
280    return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
281  }
282
283  return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
284                     type);
285}
286
287DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
288                                         DefinedOrUnknownSVal lhs,
289                                         DefinedOrUnknownSVal rhs) {
290  return evalBinOp(state, BO_EQ, lhs, rhs, Context.IntTy)
291      .castAs<DefinedOrUnknownSVal>();
292}
293
294/// Recursively check if the pointer types are equal modulo const, volatile,
295/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
296/// Assumes the input types are canonical.
297static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
298                                                         QualType FromTy) {
299  while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
300    Qualifiers Quals1, Quals2;
301    ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
302    FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
303
304    // Make sure that non cvr-qualifiers the other qualifiers (e.g., address
305    // spaces) are identical.
306    Quals1.removeCVRQualifiers();
307    Quals2.removeCVRQualifiers();
308    if (Quals1 != Quals2)
309      return false;
310  }
311
312  // If we are casting to void, the 'From' value can be used to represent the
313  // 'To' value.
314  if (ToTy->isVoidType())
315    return true;
316
317  if (ToTy != FromTy)
318    return false;
319
320  return true;
321}
322
323// FIXME: should rewrite according to the cast kind.
324SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
325  castTy = Context.getCanonicalType(castTy);
326  originalTy = Context.getCanonicalType(originalTy);
327  if (val.isUnknownOrUndef() || castTy == originalTy)
328    return val;
329
330  if (castTy->isBooleanType()) {
331    if (val.isUnknownOrUndef())
332      return val;
333    if (val.isConstant())
334      return makeTruthVal(!val.isZeroConstant(), castTy);
335    if (SymbolRef Sym = val.getAsSymbol()) {
336      BasicValueFactory &BVF = getBasicValueFactory();
337      // FIXME: If we had a state here, we could see if the symbol is known to
338      // be zero, but we don't.
339      return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy);
340    }
341
342    assert(val.getAs<Loc>());
343    return makeTruthVal(true, castTy);
344  }
345
346  // For const casts, casts to void, just propagate the value.
347  if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
348    if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
349                                         Context.getPointerType(originalTy)))
350      return val;
351
352  // Check for casts from pointers to integers.
353  if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy))
354    return evalCastFromLoc(val.castAs<Loc>(), castTy);
355
356  // Check for casts from integers to pointers.
357  if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) {
358    if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) {
359      if (const MemRegion *R = LV->getLoc().getAsRegion()) {
360        StoreManager &storeMgr = StateMgr.getStoreManager();
361        R = storeMgr.castRegion(R, castTy);
362        return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
363      }
364      return LV->getLoc();
365    }
366    return dispatchCast(val, castTy);
367  }
368
369  // Just pass through function and block pointers.
370  if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
371    assert(Loc::isLocType(castTy));
372    return val;
373  }
374
375  // Check for casts from array type to another type.
376  if (originalTy->isArrayType()) {
377    // We will always decay to a pointer.
378    val = StateMgr.ArrayToPointer(val.castAs<Loc>());
379
380    // Are we casting from an array to a pointer?  If so just pass on
381    // the decayed value.
382    if (castTy->isPointerType() || castTy->isReferenceType())
383      return val;
384
385    // Are we casting from an array to an integer?  If so, cast the decayed
386    // pointer value to an integer.
387    assert(castTy->isIntegralOrEnumerationType());
388
389    // FIXME: Keep these here for now in case we decide soon that we
390    // need the original decayed type.
391    //    QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
392    //    QualType pointerTy = C.getPointerType(elemTy);
393    return evalCastFromLoc(val.castAs<Loc>(), castTy);
394  }
395
396  // Check for casts from a region to a specific type.
397  if (const MemRegion *R = val.getAsRegion()) {
398    // Handle other casts of locations to integers.
399    if (castTy->isIntegralOrEnumerationType())
400      return evalCastFromLoc(loc::MemRegionVal(R), castTy);
401
402    // FIXME: We should handle the case where we strip off view layers to get
403    //  to a desugared type.
404    if (!Loc::isLocType(castTy)) {
405      // FIXME: There can be gross cases where one casts the result of a function
406      // (that returns a pointer) to some other value that happens to fit
407      // within that pointer value.  We currently have no good way to
408      // model such operations.  When this happens, the underlying operation
409      // is that the caller is reasoning about bits.  Conceptually we are
410      // layering a "view" of a location on top of those bits.  Perhaps
411      // we need to be more lazy about mutual possible views, even on an
412      // SVal?  This may be necessary for bit-level reasoning as well.
413      return UnknownVal();
414    }
415
416    // We get a symbolic function pointer for a dereference of a function
417    // pointer, but it is of function type. Example:
418
419    //  struct FPRec {
420    //    void (*my_func)(int * x);
421    //  };
422    //
423    //  int bar(int x);
424    //
425    //  int f1_a(struct FPRec* foo) {
426    //    int x;
427    //    (*foo->my_func)(&x);
428    //    return bar(x)+1; // no-warning
429    //  }
430
431    assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
432           originalTy->isBlockPointerType() || castTy->isReferenceType());
433
434    StoreManager &storeMgr = StateMgr.getStoreManager();
435
436    // Delegate to store manager to get the result of casting a region to a
437    // different type.  If the MemRegion* returned is NULL, this expression
438    // Evaluates to UnknownVal.
439    R = storeMgr.castRegion(R, castTy);
440    return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
441  }
442
443  return dispatchCast(val, castTy);
444}
445