SValBuilder.cpp revision 17eb65f1bfcc33d2a9ecefe32368cb374155dbdc 
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/AST/ExprCXX.h"
16#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h"
21
22using namespace clang;
23using namespace ento;
24
25//===----------------------------------------------------------------------===//
26// Basic SVal creation.
27//===----------------------------------------------------------------------===//
28
29void SValBuilder::anchor() { }
30
31DefinedOrUnknownSVal SValBuilder::makeZeroVal(QualType type) {
32  if (Loc::isLocType(type))
33    return makeNull();
34
35  if (type->isIntegerType())
36    return makeIntVal(0, type);
37
38  // FIXME: Handle floats.
39  // FIXME: Handle structs.
40  return UnknownVal();
41}
42
43NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
44                                const llvm::APSInt& rhs, QualType type) {
45  // The Environment ensures we always get a persistent APSInt in
46  // BasicValueFactory, so we don't need to get the APSInt from
47  // BasicValueFactory again.
48  assert(lhs);
49  assert(!Loc::isLocType(type));
50  return nonloc::SymbolVal(SymMgr.getSymIntExpr(lhs, op, rhs, type));
51}
52
53NonLoc SValBuilder::makeNonLoc(const llvm::APSInt& lhs,
54                               BinaryOperator::Opcode op, const SymExpr *rhs,
55                               QualType type) {
56  assert(rhs);
57  assert(!Loc::isLocType(type));
58  return nonloc::SymbolVal(SymMgr.getIntSymExpr(lhs, op, rhs, type));
59}
60
61NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
62                               const SymExpr *rhs, QualType type) {
63  assert(lhs && rhs);
64  assert(!Loc::isLocType(type));
65  return nonloc::SymbolVal(SymMgr.getSymSymExpr(lhs, op, rhs, type));
66}
67
68NonLoc SValBuilder::makeNonLoc(const SymExpr *operand,
69                               QualType fromTy, QualType toTy) {
70  assert(operand);
71  assert(!Loc::isLocType(toTy));
72  return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy));
73}
74
75SVal SValBuilder::convertToArrayIndex(SVal val) {
76  if (val.isUnknownOrUndef())
77    return val;
78
79  // Common case: we have an appropriately sized integer.
80  if (nonloc::ConcreteInt* CI = dyn_cast<nonloc::ConcreteInt>(&val)) {
81    const llvm::APSInt& I = CI->getValue();
82    if (I.getBitWidth() == ArrayIndexWidth && I.isSigned())
83      return val;
84  }
85
86  return evalCastFromNonLoc(cast<NonLoc>(val), ArrayIndexTy);
87}
88
89nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){
90  return makeTruthVal(boolean->getValue());
91}
92
93DefinedOrUnknownSVal
94SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) {
95  QualType T = region->getValueType();
96
97  if (!SymbolManager::canSymbolicate(T))
98    return UnknownVal();
99
100  SymbolRef sym = SymMgr.getRegionValueSymbol(region);
101
102  if (Loc::isLocType(T))
103    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
104
105  return nonloc::SymbolVal(sym);
106}
107
108DefinedOrUnknownSVal
109SValBuilder::getConjuredSymbolVal(const void *symbolTag,
110                                  const Expr *expr,
111                                  const LocationContext *LCtx,
112                                  unsigned count) {
113  QualType T = expr->getType();
114  return getConjuredSymbolVal(symbolTag, expr, LCtx, T, count);
115}
116
117DefinedOrUnknownSVal
118SValBuilder::getConjuredSymbolVal(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.getConjuredSymbol(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
136SValBuilder::getConjuredSymbolVal(const Stmt *stmt,
137                                  const LocationContext *LCtx,
138                                  QualType type,
139                                  unsigned visitCount) {
140  if (!SymbolManager::canSymbolicate(type))
141    return UnknownVal();
142
143  SymbolRef sym = SymMgr.getConjuredSymbol(stmt, LCtx, type, visitCount);
144
145  if (Loc::isLocType(type))
146    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
147
148  return nonloc::SymbolVal(sym);
149}
150
151DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
152                                              const MemRegion *region,
153                                              const Expr *expr, QualType type,
154                                              unsigned count) {
155  assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
156
157  SymbolRef sym =
158      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
159
160  if (Loc::isLocType(type))
161    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
162
163  return nonloc::SymbolVal(sym);
164}
165
166DefinedOrUnknownSVal
167SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
168                                             const TypedValueRegion *region) {
169  QualType T = region->getValueType();
170
171  if (!SymbolManager::canSymbolicate(T))
172    return UnknownVal();
173
174  SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
175
176  if (Loc::isLocType(T))
177    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
178
179  return nonloc::SymbolVal(sym);
180}
181
182DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
183  return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
184}
185
186DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
187                                         CanQualType locTy,
188                                         const LocationContext *locContext) {
189  const BlockTextRegion *BC =
190    MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
191  const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext);
192  return loc::MemRegionVal(BD);
193}
194
195//===----------------------------------------------------------------------===//
196
197SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
198                                   BinaryOperator::Opcode Op,
199                                   NonLoc LHS, NonLoc RHS,
200                                   QualType ResultTy) {
201  if (!State->isTainted(RHS) && !State->isTainted(LHS))
202    return UnknownVal();
203
204  const SymExpr *symLHS = LHS.getAsSymExpr();
205  const SymExpr *symRHS = RHS.getAsSymExpr();
206  // TODO: When the Max Complexity is reached, we should conjure a symbol
207  // instead of generating an Unknown value and propagate the taint info to it.
208  const unsigned MaxComp = 10000; // 100000 28X
209
210  if (symLHS && symRHS &&
211      (symLHS->computeComplexity() + symRHS->computeComplexity()) <  MaxComp)
212    return makeNonLoc(symLHS, Op, symRHS, ResultTy);
213
214  if (symLHS && symLHS->computeComplexity() < MaxComp)
215    if (const nonloc::ConcreteInt *rInt = dyn_cast<nonloc::ConcreteInt>(&RHS))
216      return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
217
218  if (symRHS && symRHS->computeComplexity() < MaxComp)
219    if (const nonloc::ConcreteInt *lInt = dyn_cast<nonloc::ConcreteInt>(&LHS))
220      return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
221
222  return UnknownVal();
223}
224
225
226SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
227                            SVal lhs, SVal rhs, QualType type) {
228
229  if (lhs.isUndef() || rhs.isUndef())
230    return UndefinedVal();
231
232  if (lhs.isUnknown() || rhs.isUnknown())
233    return UnknownVal();
234
235  if (isa<Loc>(lhs)) {
236    if (isa<Loc>(rhs))
237      return evalBinOpLL(state, op, cast<Loc>(lhs), cast<Loc>(rhs), type);
238
239    return evalBinOpLN(state, op, cast<Loc>(lhs), cast<NonLoc>(rhs), type);
240  }
241
242  if (isa<Loc>(rhs)) {
243    // Support pointer arithmetic where the addend is on the left
244    // and the pointer on the right.
245    assert(op == BO_Add);
246
247    // Commute the operands.
248    return evalBinOpLN(state, op, cast<Loc>(rhs), cast<NonLoc>(lhs), type);
249  }
250
251  return evalBinOpNN(state, op, cast<NonLoc>(lhs), cast<NonLoc>(rhs), type);
252}
253
254DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
255                                         DefinedOrUnknownSVal lhs,
256                                         DefinedOrUnknownSVal rhs) {
257  return cast<DefinedOrUnknownSVal>(evalBinOp(state, BO_EQ, lhs, rhs,
258                                              Context.IntTy));
259}
260
261/// Recursively check if the pointer types are equal modulo const, volatile,
262/// and restrict qualifiers. Assumes the input types are canonical.
263/// TODO: This is based off of code in SemaCast; can we reuse it.
264static bool haveSimilarTypes(ASTContext &Context, QualType T1,
265                                                  QualType T2) {
266  while (Context.UnwrapSimilarPointerTypes(T1, T2)) {
267    Qualifiers Quals1, Quals2;
268    T1 = Context.getUnqualifiedArrayType(T1, Quals1);
269    T2 = Context.getUnqualifiedArrayType(T2, Quals2);
270
271    // Make sure that non cvr-qualifiers the other qualifiers (e.g., address
272    // spaces) are identical.
273    Quals1.removeCVRQualifiers();
274    Quals2.removeCVRQualifiers();
275    if (Quals1 != Quals2)
276      return false;
277  }
278
279  if (T1 != T2)
280    return false;
281
282  return true;
283}
284
285// FIXME: should rewrite according to the cast kind.
286SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
287  castTy = Context.getCanonicalType(castTy);
288  originalTy = Context.getCanonicalType(originalTy);
289  if (val.isUnknownOrUndef() || castTy == originalTy)
290    return val;
291
292  // For const casts, just propagate the value.
293  if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
294    if (haveSimilarTypes(Context, Context.getPointerType(castTy),
295                                  Context.getPointerType(originalTy)))
296      return val;
297
298  // Check for casts from pointers to integers.
299  if (castTy->isIntegerType() && Loc::isLocType(originalTy))
300    return evalCastFromLoc(cast<Loc>(val), castTy);
301
302  // Check for casts from integers to pointers.
303  if (Loc::isLocType(castTy) && originalTy->isIntegerType()) {
304    if (nonloc::LocAsInteger *LV = dyn_cast<nonloc::LocAsInteger>(&val)) {
305      if (const MemRegion *R = LV->getLoc().getAsRegion()) {
306        StoreManager &storeMgr = StateMgr.getStoreManager();
307        R = storeMgr.castRegion(R, castTy);
308        return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
309      }
310      return LV->getLoc();
311    }
312    return dispatchCast(val, castTy);
313  }
314
315  // Just pass through function and block pointers.
316  if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
317    assert(Loc::isLocType(castTy));
318    return val;
319  }
320
321  // Check for casts from array type to another type.
322  if (originalTy->isArrayType()) {
323    // We will always decay to a pointer.
324    val = StateMgr.ArrayToPointer(cast<Loc>(val));
325
326    // Are we casting from an array to a pointer?  If so just pass on
327    // the decayed value.
328    if (castTy->isPointerType() || castTy->isReferenceType())
329      return val;
330
331    // Are we casting from an array to an integer?  If so, cast the decayed
332    // pointer value to an integer.
333    assert(castTy->isIntegerType());
334
335    // FIXME: Keep these here for now in case we decide soon that we
336    // need the original decayed type.
337    //    QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
338    //    QualType pointerTy = C.getPointerType(elemTy);
339    return evalCastFromLoc(cast<Loc>(val), castTy);
340  }
341
342  // Check for casts from a region to a specific type.
343  if (const MemRegion *R = val.getAsRegion()) {
344    // Handle other casts of locations to integers.
345    if (castTy->isIntegerType())
346      return evalCastFromLoc(loc::MemRegionVal(R), castTy);
347
348    // FIXME: We should handle the case where we strip off view layers to get
349    //  to a desugared type.
350    if (!Loc::isLocType(castTy)) {
351      // FIXME: There can be gross cases where one casts the result of a function
352      // (that returns a pointer) to some other value that happens to fit
353      // within that pointer value.  We currently have no good way to
354      // model such operations.  When this happens, the underlying operation
355      // is that the caller is reasoning about bits.  Conceptually we are
356      // layering a "view" of a location on top of those bits.  Perhaps
357      // we need to be more lazy about mutual possible views, even on an
358      // SVal?  This may be necessary for bit-level reasoning as well.
359      return UnknownVal();
360    }
361
362    // We get a symbolic function pointer for a dereference of a function
363    // pointer, but it is of function type. Example:
364
365    //  struct FPRec {
366    //    void (*my_func)(int * x);
367    //  };
368    //
369    //  int bar(int x);
370    //
371    //  int f1_a(struct FPRec* foo) {
372    //    int x;
373    //    (*foo->my_func)(&x);
374    //    return bar(x)+1; // no-warning
375    //  }
376
377    assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
378           originalTy->isBlockPointerType() || castTy->isReferenceType());
379
380    StoreManager &storeMgr = StateMgr.getStoreManager();
381
382    // Delegate to store manager to get the result of casting a region to a
383    // different type.  If the MemRegion* returned is NULL, this expression
384    // Evaluates to UnknownVal.
385    R = storeMgr.castRegion(R, castTy);
386    return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
387  }
388
389  return dispatchCast(val, castTy);
390}
391