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 (T->isNullPtrType())
99    return makeZeroVal(T);
100
101  if (!SymbolManager::canSymbolicate(T))
102    return UnknownVal();
103
104  SymbolRef sym = SymMgr.getRegionValueSymbol(region);
105
106  if (Loc::isLocType(T))
107    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
108
109  return nonloc::SymbolVal(sym);
110}
111
112DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *SymbolTag,
113                                                   const Expr *Ex,
114                                                   const LocationContext *LCtx,
115                                                   unsigned Count) {
116  QualType T = Ex->getType();
117
118  if (T->isNullPtrType())
119    return makeZeroVal(T);
120
121  // Compute the type of the result. If the expression is not an R-value, the
122  // result should be a location.
123  QualType ExType = Ex->getType();
124  if (Ex->isGLValue())
125    T = LCtx->getAnalysisDeclContext()->getASTContext().getPointerType(ExType);
126
127  return conjureSymbolVal(SymbolTag, Ex, LCtx, T, Count);
128}
129
130DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
131                                                   const Expr *expr,
132                                                   const LocationContext *LCtx,
133                                                   QualType type,
134                                                   unsigned count) {
135  if (type->isNullPtrType())
136    return makeZeroVal(type);
137
138  if (!SymbolManager::canSymbolicate(type))
139    return UnknownVal();
140
141  SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
142
143  if (Loc::isLocType(type))
144    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
145
146  return nonloc::SymbolVal(sym);
147}
148
149
150DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
151                                                   const LocationContext *LCtx,
152                                                   QualType type,
153                                                   unsigned visitCount) {
154  if (type->isNullPtrType())
155    return makeZeroVal(type);
156
157  if (!SymbolManager::canSymbolicate(type))
158    return UnknownVal();
159
160  SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
161
162  if (Loc::isLocType(type))
163    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
164
165  return nonloc::SymbolVal(sym);
166}
167
168DefinedOrUnknownSVal
169SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
170                                      const LocationContext *LCtx,
171                                      unsigned VisitCount) {
172  QualType T = E->getType();
173  assert(Loc::isLocType(T));
174  assert(SymbolManager::canSymbolicate(T));
175  if (T->isNullPtrType())
176    return makeZeroVal(T);
177
178  SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
179  return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
180}
181
182DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
183                                              const MemRegion *region,
184                                              const Expr *expr, QualType type,
185                                              unsigned count) {
186  assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
187
188  SymbolRef sym =
189      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
190
191  if (Loc::isLocType(type))
192    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
193
194  return nonloc::SymbolVal(sym);
195}
196
197DefinedOrUnknownSVal
198SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
199                                             const TypedValueRegion *region) {
200  QualType T = region->getValueType();
201
202  if (T->isNullPtrType())
203    return makeZeroVal(T);
204
205  if (!SymbolManager::canSymbolicate(T))
206    return UnknownVal();
207
208  SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
209
210  if (Loc::isLocType(T))
211    return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
212
213  return nonloc::SymbolVal(sym);
214}
215
216DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
217  return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
218}
219
220DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
221                                         CanQualType locTy,
222                                         const LocationContext *locContext,
223                                         unsigned blockCount) {
224  const BlockTextRegion *BC =
225    MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
226  const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext,
227                                                        blockCount);
228  return loc::MemRegionVal(BD);
229}
230
231/// Return a memory region for the 'this' object reference.
232loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
233                                          const StackFrameContext *SFC) {
234  return loc::MemRegionVal(getRegionManager().
235                           getCXXThisRegion(D->getThisType(getContext()), SFC));
236}
237
238/// Return a memory region for the 'this' object reference.
239loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
240                                          const StackFrameContext *SFC) {
241  const Type *T = D->getTypeForDecl();
242  QualType PT = getContext().getPointerType(QualType(T, 0));
243  return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
244}
245
246Optional<SVal> SValBuilder::getConstantVal(const Expr *E) {
247  E = E->IgnoreParens();
248
249  switch (E->getStmtClass()) {
250  // Handle expressions that we treat differently from the AST's constant
251  // evaluator.
252  case Stmt::AddrLabelExprClass:
253    return makeLoc(cast<AddrLabelExpr>(E));
254
255  case Stmt::CXXScalarValueInitExprClass:
256  case Stmt::ImplicitValueInitExprClass:
257    return makeZeroVal(E->getType());
258
259  case Stmt::ObjCStringLiteralClass: {
260    const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
261    return makeLoc(getRegionManager().getObjCStringRegion(SL));
262  }
263
264  case Stmt::StringLiteralClass: {
265    const StringLiteral *SL = cast<StringLiteral>(E);
266    return makeLoc(getRegionManager().getStringRegion(SL));
267  }
268
269  // Fast-path some expressions to avoid the overhead of going through the AST's
270  // constant evaluator
271  case Stmt::CharacterLiteralClass: {
272    const CharacterLiteral *C = cast<CharacterLiteral>(E);
273    return makeIntVal(C->getValue(), C->getType());
274  }
275
276  case Stmt::CXXBoolLiteralExprClass:
277    return makeBoolVal(cast<CXXBoolLiteralExpr>(E));
278
279  case Stmt::TypeTraitExprClass: {
280    const TypeTraitExpr *TE = cast<TypeTraitExpr>(E);
281    return makeTruthVal(TE->getValue(), TE->getType());
282  }
283
284  case Stmt::IntegerLiteralClass:
285    return makeIntVal(cast<IntegerLiteral>(E));
286
287  case Stmt::ObjCBoolLiteralExprClass:
288    return makeBoolVal(cast<ObjCBoolLiteralExpr>(E));
289
290  case Stmt::CXXNullPtrLiteralExprClass:
291    return makeNull();
292
293  case Stmt::ImplicitCastExprClass: {
294    const CastExpr *CE = cast<CastExpr>(E);
295    switch (CE->getCastKind()) {
296    default:
297      break;
298    case CK_ArrayToPointerDecay:
299    case CK_BitCast: {
300      const Expr *SE = CE->getSubExpr();
301      Optional<SVal> Val = getConstantVal(SE);
302      if (!Val)
303        return None;
304      return evalCast(*Val, CE->getType(), SE->getType());
305    }
306    }
307    // FALLTHROUGH
308  }
309
310  // If we don't have a special case, fall back to the AST's constant evaluator.
311  default: {
312    // Don't try to come up with a value for materialized temporaries.
313    if (E->isGLValue())
314      return None;
315
316    ASTContext &Ctx = getContext();
317    llvm::APSInt Result;
318    if (E->EvaluateAsInt(Result, Ctx))
319      return makeIntVal(Result);
320
321    if (Loc::isLocType(E->getType()))
322      if (E->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull))
323        return makeNull();
324
325    return None;
326  }
327  }
328}
329
330//===----------------------------------------------------------------------===//
331
332SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
333                                   BinaryOperator::Opcode Op,
334                                   NonLoc LHS, NonLoc RHS,
335                                   QualType ResultTy) {
336  if (!State->isTainted(RHS) && !State->isTainted(LHS))
337    return UnknownVal();
338
339  const SymExpr *symLHS = LHS.getAsSymExpr();
340  const SymExpr *symRHS = RHS.getAsSymExpr();
341  // TODO: When the Max Complexity is reached, we should conjure a symbol
342  // instead of generating an Unknown value and propagate the taint info to it.
343  const unsigned MaxComp = 10000; // 100000 28X
344
345  if (symLHS && symRHS &&
346      (symLHS->computeComplexity() + symRHS->computeComplexity()) <  MaxComp)
347    return makeNonLoc(symLHS, Op, symRHS, ResultTy);
348
349  if (symLHS && symLHS->computeComplexity() < MaxComp)
350    if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>())
351      return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
352
353  if (symRHS && symRHS->computeComplexity() < MaxComp)
354    if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>())
355      return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
356
357  return UnknownVal();
358}
359
360
361SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
362                            SVal lhs, SVal rhs, QualType type) {
363
364  if (lhs.isUndef() || rhs.isUndef())
365    return UndefinedVal();
366
367  if (lhs.isUnknown() || rhs.isUnknown())
368    return UnknownVal();
369
370  if (Optional<Loc> LV = lhs.getAs<Loc>()) {
371    if (Optional<Loc> RV = rhs.getAs<Loc>())
372      return evalBinOpLL(state, op, *LV, *RV, type);
373
374    return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
375  }
376
377  if (Optional<Loc> RV = rhs.getAs<Loc>()) {
378    // Support pointer arithmetic where the addend is on the left
379    // and the pointer on the right.
380    assert(op == BO_Add);
381
382    // Commute the operands.
383    return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
384  }
385
386  return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
387                     type);
388}
389
390DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
391                                         DefinedOrUnknownSVal lhs,
392                                         DefinedOrUnknownSVal rhs) {
393  return evalBinOp(state, BO_EQ, lhs, rhs, getConditionType())
394      .castAs<DefinedOrUnknownSVal>();
395}
396
397/// Recursively check if the pointer types are equal modulo const, volatile,
398/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
399/// Assumes the input types are canonical.
400static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
401                                                         QualType FromTy) {
402  while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
403    Qualifiers Quals1, Quals2;
404    ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
405    FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
406
407    // Make sure that non-cvr-qualifiers the other qualifiers (e.g., address
408    // spaces) are identical.
409    Quals1.removeCVRQualifiers();
410    Quals2.removeCVRQualifiers();
411    if (Quals1 != Quals2)
412      return false;
413  }
414
415  // If we are casting to void, the 'From' value can be used to represent the
416  // 'To' value.
417  if (ToTy->isVoidType())
418    return true;
419
420  if (ToTy != FromTy)
421    return false;
422
423  return true;
424}
425
426// FIXME: should rewrite according to the cast kind.
427SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
428  castTy = Context.getCanonicalType(castTy);
429  originalTy = Context.getCanonicalType(originalTy);
430  if (val.isUnknownOrUndef() || castTy == originalTy)
431    return val;
432
433  if (castTy->isBooleanType()) {
434    if (val.isUnknownOrUndef())
435      return val;
436    if (val.isConstant())
437      return makeTruthVal(!val.isZeroConstant(), castTy);
438    if (!Loc::isLocType(originalTy) &&
439        !originalTy->isIntegralOrEnumerationType() &&
440        !originalTy->isMemberPointerType())
441      return UnknownVal();
442    if (SymbolRef Sym = val.getAsSymbol(true)) {
443      BasicValueFactory &BVF = getBasicValueFactory();
444      // FIXME: If we had a state here, we could see if the symbol is known to
445      // be zero, but we don't.
446      return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy);
447    }
448    // Loc values are not always true, they could be weakly linked functions.
449    if (Optional<Loc> L = val.getAs<Loc>())
450      return evalCastFromLoc(*L, castTy);
451
452    Loc L = val.castAs<nonloc::LocAsInteger>().getLoc();
453    return evalCastFromLoc(L, castTy);
454  }
455
456  // For const casts, casts to void, just propagate the value.
457  if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
458    if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
459                                         Context.getPointerType(originalTy)))
460      return val;
461
462  // Check for casts from pointers to integers.
463  if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy))
464    return evalCastFromLoc(val.castAs<Loc>(), castTy);
465
466  // Check for casts from integers to pointers.
467  if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) {
468    if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) {
469      if (const MemRegion *R = LV->getLoc().getAsRegion()) {
470        StoreManager &storeMgr = StateMgr.getStoreManager();
471        R = storeMgr.castRegion(R, castTy);
472        return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
473      }
474      return LV->getLoc();
475    }
476    return dispatchCast(val, castTy);
477  }
478
479  // Just pass through function and block pointers.
480  if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
481    assert(Loc::isLocType(castTy));
482    return val;
483  }
484
485  // Check for casts from array type to another type.
486  if (const ArrayType *arrayT =
487                      dyn_cast<ArrayType>(originalTy.getCanonicalType())) {
488    // We will always decay to a pointer.
489    QualType elemTy = arrayT->getElementType();
490    val = StateMgr.ArrayToPointer(val.castAs<Loc>(), elemTy);
491
492    // Are we casting from an array to a pointer?  If so just pass on
493    // the decayed value.
494    if (castTy->isPointerType() || castTy->isReferenceType())
495      return val;
496
497    // Are we casting from an array to an integer?  If so, cast the decayed
498    // pointer value to an integer.
499    assert(castTy->isIntegralOrEnumerationType());
500
501    // FIXME: Keep these here for now in case we decide soon that we
502    // need the original decayed type.
503    //    QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
504    //    QualType pointerTy = C.getPointerType(elemTy);
505    return evalCastFromLoc(val.castAs<Loc>(), castTy);
506  }
507
508  // Check for casts from a region to a specific type.
509  if (const MemRegion *R = val.getAsRegion()) {
510    // Handle other casts of locations to integers.
511    if (castTy->isIntegralOrEnumerationType())
512      return evalCastFromLoc(loc::MemRegionVal(R), castTy);
513
514    // FIXME: We should handle the case where we strip off view layers to get
515    //  to a desugared type.
516    if (!Loc::isLocType(castTy)) {
517      // FIXME: There can be gross cases where one casts the result of a function
518      // (that returns a pointer) to some other value that happens to fit
519      // within that pointer value.  We currently have no good way to
520      // model such operations.  When this happens, the underlying operation
521      // is that the caller is reasoning about bits.  Conceptually we are
522      // layering a "view" of a location on top of those bits.  Perhaps
523      // we need to be more lazy about mutual possible views, even on an
524      // SVal?  This may be necessary for bit-level reasoning as well.
525      return UnknownVal();
526    }
527
528    // We get a symbolic function pointer for a dereference of a function
529    // pointer, but it is of function type. Example:
530
531    //  struct FPRec {
532    //    void (*my_func)(int * x);
533    //  };
534    //
535    //  int bar(int x);
536    //
537    //  int f1_a(struct FPRec* foo) {
538    //    int x;
539    //    (*foo->my_func)(&x);
540    //    return bar(x)+1; // no-warning
541    //  }
542
543    assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
544           originalTy->isBlockPointerType() || castTy->isReferenceType());
545
546    StoreManager &storeMgr = StateMgr.getStoreManager();
547
548    // Delegate to store manager to get the result of casting a region to a
549    // different type.  If the MemRegion* returned is NULL, this expression
550    // Evaluates to UnknownVal.
551    R = storeMgr.castRegion(R, castTy);
552    return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
553  }
554
555  return dispatchCast(val, castTy);
556}
557