SValBuilder.cpp revision a5796f87229b4aeebca71fa6ee1790ae7a5a0382 
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 *expr,
111                                                   const LocationContext *LCtx,
112                                                   unsigned count) {
113  QualType T = expr->getType();
114  return conjureSymbolVal(symbolTag, expr, LCtx, T, count);
115}
116
117DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
118                                                   const Expr *expr,
119                                                   const LocationContext *LCtx,
120                                                   QualType type,
121                                                   unsigned count) {
122  if (!SymbolManager::canSymbolicate(type))
123    return UnknownVal();
124
125  SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
126
127  if (Loc::isLocType(type))
128    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
129
130  return nonloc::SymbolVal(sym);
131}
132
133
134DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
135                                                   const LocationContext *LCtx,
136                                                   QualType type,
137                                                   unsigned visitCount) {
138  if (!SymbolManager::canSymbolicate(type))
139    return UnknownVal();
140
141  SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
142
143  if (Loc::isLocType(type))
144    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
145
146  return nonloc::SymbolVal(sym);
147}
148
149DefinedOrUnknownSVal
150SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
151                                      const LocationContext *LCtx,
152                                      unsigned VisitCount) {
153  QualType T = E->getType();
154  assert(Loc::isLocType(T));
155  assert(SymbolManager::canSymbolicate(T));
156
157  SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
158  return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
159}
160
161DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
162                                              const MemRegion *region,
163                                              const Expr *expr, QualType type,
164                                              unsigned count) {
165  assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
166
167  SymbolRef sym =
168      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
169
170  if (Loc::isLocType(type))
171    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
172
173  return nonloc::SymbolVal(sym);
174}
175
176DefinedOrUnknownSVal
177SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
178                                             const TypedValueRegion *region) {
179  QualType T = region->getValueType();
180
181  if (!SymbolManager::canSymbolicate(T))
182    return UnknownVal();
183
184  SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
185
186  if (Loc::isLocType(T))
187    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
188
189  return nonloc::SymbolVal(sym);
190}
191
192DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
193  return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
194}
195
196DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
197                                         CanQualType locTy,
198                                         const LocationContext *locContext) {
199  const BlockTextRegion *BC =
200    MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
201  const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext);
202  return loc::MemRegionVal(BD);
203}
204
205/// Return a memory region for the 'this' object reference.
206loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
207                                          const StackFrameContext *SFC) {
208  return loc::MemRegionVal(getRegionManager().
209                           getCXXThisRegion(D->getThisType(getContext()), SFC));
210}
211
212/// Return a memory region for the 'this' object reference.
213loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
214                                          const StackFrameContext *SFC) {
215  const Type *T = D->getTypeForDecl();
216  QualType PT = getContext().getPointerType(QualType(T, 0));
217  return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
218}
219
220//===----------------------------------------------------------------------===//
221
222SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
223                                   BinaryOperator::Opcode Op,
224                                   NonLoc LHS, NonLoc RHS,
225                                   QualType ResultTy) {
226  if (!State->isTainted(RHS) && !State->isTainted(LHS))
227    return UnknownVal();
228
229  const SymExpr *symLHS = LHS.getAsSymExpr();
230  const SymExpr *symRHS = RHS.getAsSymExpr();
231  // TODO: When the Max Complexity is reached, we should conjure a symbol
232  // instead of generating an Unknown value and propagate the taint info to it.
233  const unsigned MaxComp = 10000; // 100000 28X
234
235  if (symLHS && symRHS &&
236      (symLHS->computeComplexity() + symRHS->computeComplexity()) <  MaxComp)
237    return makeNonLoc(symLHS, Op, symRHS, ResultTy);
238
239  if (symLHS && symLHS->computeComplexity() < MaxComp)
240    if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>())
241      return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
242
243  if (symRHS && symRHS->computeComplexity() < MaxComp)
244    if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>())
245      return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
246
247  return UnknownVal();
248}
249
250
251SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
252                            SVal lhs, SVal rhs, QualType type) {
253
254  if (lhs.isUndef() || rhs.isUndef())
255    return UndefinedVal();
256
257  if (lhs.isUnknown() || rhs.isUnknown())
258    return UnknownVal();
259
260  if (Optional<Loc> LV = lhs.getAs<Loc>()) {
261    if (Optional<Loc> RV = rhs.getAs<Loc>())
262      return evalBinOpLL(state, op, *LV, *RV, type);
263
264    return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
265  }
266
267  if (Optional<Loc> RV = rhs.getAs<Loc>()) {
268    // Support pointer arithmetic where the addend is on the left
269    // and the pointer on the right.
270    assert(op == BO_Add);
271
272    // Commute the operands.
273    return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
274  }
275
276  return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
277                     type);
278}
279
280DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
281                                         DefinedOrUnknownSVal lhs,
282                                         DefinedOrUnknownSVal rhs) {
283  return evalBinOp(state, BO_EQ, lhs, rhs, Context.IntTy)
284      .castAs<DefinedOrUnknownSVal>();
285}
286
287/// Recursively check if the pointer types are equal modulo const, volatile,
288/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
289/// Assumes the input types are canonical.
290static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
291                                                         QualType FromTy) {
292  while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
293    Qualifiers Quals1, Quals2;
294    ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
295    FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
296
297    // Make sure that non cvr-qualifiers the other qualifiers (e.g., address
298    // spaces) are identical.
299    Quals1.removeCVRQualifiers();
300    Quals2.removeCVRQualifiers();
301    if (Quals1 != Quals2)
302      return false;
303  }
304
305  // If we are casting to void, the 'From' value can be used to represent the
306  // 'To' value.
307  if (ToTy->isVoidType())
308    return true;
309
310  if (ToTy != FromTy)
311    return false;
312
313  return true;
314}
315
316// FIXME: should rewrite according to the cast kind.
317SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
318  castTy = Context.getCanonicalType(castTy);
319  originalTy = Context.getCanonicalType(originalTy);
320  if (val.isUnknownOrUndef() || castTy == originalTy)
321    return val;
322
323  // For const casts, casts to void, just propagate the value.
324  if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
325    if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
326                                         Context.getPointerType(originalTy)))
327      return val;
328
329  // Check for casts from pointers to integers.
330  if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy))
331    return evalCastFromLoc(val.castAs<Loc>(), castTy);
332
333  // Check for casts from integers to pointers.
334  if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) {
335    if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) {
336      if (const MemRegion *R = LV->getLoc().getAsRegion()) {
337        StoreManager &storeMgr = StateMgr.getStoreManager();
338        R = storeMgr.castRegion(R, castTy);
339        return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
340      }
341      return LV->getLoc();
342    }
343    return dispatchCast(val, castTy);
344  }
345
346  // Just pass through function and block pointers.
347  if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
348    assert(Loc::isLocType(castTy));
349    return val;
350  }
351
352  // Check for casts from array type to another type.
353  if (originalTy->isArrayType()) {
354    // We will always decay to a pointer.
355    val = StateMgr.ArrayToPointer(val.castAs<Loc>());
356
357    // Are we casting from an array to a pointer?  If so just pass on
358    // the decayed value.
359    if (castTy->isPointerType() || castTy->isReferenceType())
360      return val;
361
362    // Are we casting from an array to an integer?  If so, cast the decayed
363    // pointer value to an integer.
364    assert(castTy->isIntegralOrEnumerationType());
365
366    // FIXME: Keep these here for now in case we decide soon that we
367    // need the original decayed type.
368    //    QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
369    //    QualType pointerTy = C.getPointerType(elemTy);
370    return evalCastFromLoc(val.castAs<Loc>(), castTy);
371  }
372
373  // Check for casts from a region to a specific type.
374  if (const MemRegion *R = val.getAsRegion()) {
375    // Handle other casts of locations to integers.
376    if (castTy->isIntegralOrEnumerationType())
377      return evalCastFromLoc(loc::MemRegionVal(R), castTy);
378
379    // FIXME: We should handle the case where we strip off view layers to get
380    //  to a desugared type.
381    if (!Loc::isLocType(castTy)) {
382      // FIXME: There can be gross cases where one casts the result of a function
383      // (that returns a pointer) to some other value that happens to fit
384      // within that pointer value.  We currently have no good way to
385      // model such operations.  When this happens, the underlying operation
386      // is that the caller is reasoning about bits.  Conceptually we are
387      // layering a "view" of a location on top of those bits.  Perhaps
388      // we need to be more lazy about mutual possible views, even on an
389      // SVal?  This may be necessary for bit-level reasoning as well.
390      return UnknownVal();
391    }
392
393    // We get a symbolic function pointer for a dereference of a function
394    // pointer, but it is of function type. Example:
395
396    //  struct FPRec {
397    //    void (*my_func)(int * x);
398    //  };
399    //
400    //  int bar(int x);
401    //
402    //  int f1_a(struct FPRec* foo) {
403    //    int x;
404    //    (*foo->my_func)(&x);
405    //    return bar(x)+1; // no-warning
406    //  }
407
408    assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
409           originalTy->isBlockPointerType() || castTy->isReferenceType());
410
411    StoreManager &storeMgr = StateMgr.getStoreManager();
412
413    // Delegate to store manager to get the result of casting a region to a
414    // different type.  If the MemRegion* returned is NULL, this expression
415    // Evaluates to UnknownVal.
416    R = storeMgr.castRegion(R, castTy);
417    return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
418  }
419
420  return dispatchCast(val, castTy);
421}
422