1//===- Store.cpp - Interface for maps from Locations to Values ------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file defined the types Store and StoreManager. 10// 11//===----------------------------------------------------------------------===// 12 13#include "clang/StaticAnalyzer/Core/PathSensitive/Store.h" 14#include "clang/AST/ASTContext.h" 15#include "clang/AST/CXXInheritance.h" 16#include "clang/AST/CharUnits.h" 17#include "clang/AST/Decl.h" 18#include "clang/AST/DeclCXX.h" 19#include "clang/AST/DeclObjC.h" 20#include "clang/AST/Expr.h" 21#include "clang/AST/Type.h" 22#include "clang/Basic/LLVM.h" 23#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h" 24#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" 25#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h" 26#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 27#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 28#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h" 29#include "clang/StaticAnalyzer/Core/PathSensitive/StoreRef.h" 30#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h" 31#include "llvm/ADT/APSInt.h" 32#include "llvm/ADT/Optional.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/Support/Casting.h" 35#include "llvm/Support/ErrorHandling.h" 36#include <cassert> 37#include <cstdint> 38 39using namespace clang; 40using namespace ento; 41 42StoreManager::StoreManager(ProgramStateManager &stateMgr) 43 : svalBuilder(stateMgr.getSValBuilder()), StateMgr(stateMgr), 44 MRMgr(svalBuilder.getRegionManager()), Ctx(stateMgr.getContext()) {} 45 46StoreRef StoreManager::enterStackFrame(Store OldStore, 47 const CallEvent &Call, 48 const StackFrameContext *LCtx) { 49 StoreRef Store = StoreRef(OldStore, *this); 50 51 SmallVector<CallEvent::FrameBindingTy, 16> InitialBindings; 52 Call.getInitialStackFrameContents(LCtx, InitialBindings); 53 54 for (const auto &I : InitialBindings) 55 Store = Bind(Store.getStore(), I.first.castAs<Loc>(), I.second); 56 57 return Store; 58} 59 60const ElementRegion *StoreManager::MakeElementRegion(const SubRegion *Base, 61 QualType EleTy, 62 uint64_t index) { 63 NonLoc idx = svalBuilder.makeArrayIndex(index); 64 return MRMgr.getElementRegion(EleTy, idx, Base, svalBuilder.getContext()); 65} 66 67const ElementRegion *StoreManager::GetElementZeroRegion(const SubRegion *R, 68 QualType T) { 69 NonLoc idx = svalBuilder.makeZeroArrayIndex(); 70 assert(!T.isNull()); 71 return MRMgr.getElementRegion(T, idx, R, Ctx); 72} 73 74const MemRegion *StoreManager::castRegion(const MemRegion *R, QualType CastToTy) { 75 ASTContext &Ctx = StateMgr.getContext(); 76 77 // Handle casts to Objective-C objects. 78 if (CastToTy->isObjCObjectPointerType()) 79 return R->StripCasts(); 80 81 if (CastToTy->isBlockPointerType()) { 82 // FIXME: We may need different solutions, depending on the symbol 83 // involved. Blocks can be casted to/from 'id', as they can be treated 84 // as Objective-C objects. This could possibly be handled by enhancing 85 // our reasoning of downcasts of symbolic objects. 86 if (isa<CodeTextRegion>(R) || isa<SymbolicRegion>(R)) 87 return R; 88 89 // We don't know what to make of it. Return a NULL region, which 90 // will be interpreted as UnknownVal. 91 return nullptr; 92 } 93 94 // Now assume we are casting from pointer to pointer. Other cases should 95 // already be handled. 96 QualType PointeeTy = CastToTy->getPointeeType(); 97 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy); 98 99 // Handle casts to void*. We just pass the region through. 100 if (CanonPointeeTy.getLocalUnqualifiedType() == Ctx.VoidTy) 101 return R; 102 103 // Handle casts from compatible types. 104 if (R->isBoundable()) 105 if (const auto *TR = dyn_cast<TypedValueRegion>(R)) { 106 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType()); 107 if (CanonPointeeTy == ObjTy) 108 return R; 109 } 110 111 // Process region cast according to the kind of the region being cast. 112 switch (R->getKind()) { 113 case MemRegion::CXXThisRegionKind: 114 case MemRegion::CodeSpaceRegionKind: 115 case MemRegion::StackLocalsSpaceRegionKind: 116 case MemRegion::StackArgumentsSpaceRegionKind: 117 case MemRegion::HeapSpaceRegionKind: 118 case MemRegion::UnknownSpaceRegionKind: 119 case MemRegion::StaticGlobalSpaceRegionKind: 120 case MemRegion::GlobalInternalSpaceRegionKind: 121 case MemRegion::GlobalSystemSpaceRegionKind: 122 case MemRegion::GlobalImmutableSpaceRegionKind: { 123 llvm_unreachable("Invalid region cast"); 124 } 125 126 case MemRegion::FunctionCodeRegionKind: 127 case MemRegion::BlockCodeRegionKind: 128 case MemRegion::BlockDataRegionKind: 129 case MemRegion::StringRegionKind: 130 // FIXME: Need to handle arbitrary downcasts. 131 case MemRegion::SymbolicRegionKind: 132 case MemRegion::AllocaRegionKind: 133 case MemRegion::CompoundLiteralRegionKind: 134 case MemRegion::FieldRegionKind: 135 case MemRegion::ObjCIvarRegionKind: 136 case MemRegion::ObjCStringRegionKind: 137 case MemRegion::NonParamVarRegionKind: 138 case MemRegion::ParamVarRegionKind: 139 case MemRegion::CXXTempObjectRegionKind: 140 case MemRegion::CXXBaseObjectRegionKind: 141 case MemRegion::CXXDerivedObjectRegionKind: 142 return MakeElementRegion(cast<SubRegion>(R), PointeeTy); 143 144 case MemRegion::ElementRegionKind: { 145 // If we are casting from an ElementRegion to another type, the 146 // algorithm is as follows: 147 // 148 // (1) Compute the "raw offset" of the ElementRegion from the 149 // base region. This is done by calling 'getAsRawOffset()'. 150 // 151 // (2a) If we get a 'RegionRawOffset' after calling 152 // 'getAsRawOffset()', determine if the absolute offset 153 // can be exactly divided into chunks of the size of the 154 // casted-pointee type. If so, create a new ElementRegion with 155 // the pointee-cast type as the new ElementType and the index 156 // being the offset divded by the chunk size. If not, create 157 // a new ElementRegion at offset 0 off the raw offset region. 158 // 159 // (2b) If we don't a get a 'RegionRawOffset' after calling 160 // 'getAsRawOffset()', it means that we are at offset 0. 161 // 162 // FIXME: Handle symbolic raw offsets. 163 164 const ElementRegion *elementR = cast<ElementRegion>(R); 165 const RegionRawOffset &rawOff = elementR->getAsArrayOffset(); 166 const MemRegion *baseR = rawOff.getRegion(); 167 168 // If we cannot compute a raw offset, throw up our hands and return 169 // a NULL MemRegion*. 170 if (!baseR) 171 return nullptr; 172 173 CharUnits off = rawOff.getOffset(); 174 175 if (off.isZero()) { 176 // Edge case: we are at 0 bytes off the beginning of baseR. We 177 // check to see if type we are casting to is the same as the base 178 // region. If so, just return the base region. 179 if (const auto *TR = dyn_cast<TypedValueRegion>(baseR)) { 180 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType()); 181 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy); 182 if (CanonPointeeTy == ObjTy) 183 return baseR; 184 } 185 186 // Otherwise, create a new ElementRegion at offset 0. 187 return MakeElementRegion(cast<SubRegion>(baseR), PointeeTy); 188 } 189 190 // We have a non-zero offset from the base region. We want to determine 191 // if the offset can be evenly divided by sizeof(PointeeTy). If so, 192 // we create an ElementRegion whose index is that value. Otherwise, we 193 // create two ElementRegions, one that reflects a raw offset and the other 194 // that reflects the cast. 195 196 // Compute the index for the new ElementRegion. 197 int64_t newIndex = 0; 198 const MemRegion *newSuperR = nullptr; 199 200 // We can only compute sizeof(PointeeTy) if it is a complete type. 201 if (!PointeeTy->isIncompleteType()) { 202 // Compute the size in **bytes**. 203 CharUnits pointeeTySize = Ctx.getTypeSizeInChars(PointeeTy); 204 if (!pointeeTySize.isZero()) { 205 // Is the offset a multiple of the size? If so, we can layer the 206 // ElementRegion (with elementType == PointeeTy) directly on top of 207 // the base region. 208 if (off % pointeeTySize == 0) { 209 newIndex = off / pointeeTySize; 210 newSuperR = baseR; 211 } 212 } 213 } 214 215 if (!newSuperR) { 216 // Create an intermediate ElementRegion to represent the raw byte. 217 // This will be the super region of the final ElementRegion. 218 newSuperR = MakeElementRegion(cast<SubRegion>(baseR), Ctx.CharTy, 219 off.getQuantity()); 220 } 221 222 return MakeElementRegion(cast<SubRegion>(newSuperR), PointeeTy, newIndex); 223 } 224 } 225 226 llvm_unreachable("unreachable"); 227} 228 229static bool regionMatchesCXXRecordType(SVal V, QualType Ty) { 230 const MemRegion *MR = V.getAsRegion(); 231 if (!MR) 232 return true; 233 234 const auto *TVR = dyn_cast<TypedValueRegion>(MR); 235 if (!TVR) 236 return true; 237 238 const CXXRecordDecl *RD = TVR->getValueType()->getAsCXXRecordDecl(); 239 if (!RD) 240 return true; 241 242 const CXXRecordDecl *Expected = Ty->getPointeeCXXRecordDecl(); 243 if (!Expected) 244 Expected = Ty->getAsCXXRecordDecl(); 245 246 return Expected->getCanonicalDecl() == RD->getCanonicalDecl(); 247} 248 249SVal StoreManager::evalDerivedToBase(SVal Derived, const CastExpr *Cast) { 250 // Sanity check to avoid doing the wrong thing in the face of 251 // reinterpret_cast. 252 if (!regionMatchesCXXRecordType(Derived, Cast->getSubExpr()->getType())) 253 return UnknownVal(); 254 255 // Walk through the cast path to create nested CXXBaseRegions. 256 SVal Result = Derived; 257 for (CastExpr::path_const_iterator I = Cast->path_begin(), 258 E = Cast->path_end(); 259 I != E; ++I) { 260 Result = evalDerivedToBase(Result, (*I)->getType(), (*I)->isVirtual()); 261 } 262 return Result; 263} 264 265SVal StoreManager::evalDerivedToBase(SVal Derived, const CXXBasePath &Path) { 266 // Walk through the path to create nested CXXBaseRegions. 267 SVal Result = Derived; 268 for (const auto &I : Path) 269 Result = evalDerivedToBase(Result, I.Base->getType(), 270 I.Base->isVirtual()); 271 return Result; 272} 273 274SVal StoreManager::evalDerivedToBase(SVal Derived, QualType BaseType, 275 bool IsVirtual) { 276 const MemRegion *DerivedReg = Derived.getAsRegion(); 277 if (!DerivedReg) 278 return Derived; 279 280 const CXXRecordDecl *BaseDecl = BaseType->getPointeeCXXRecordDecl(); 281 if (!BaseDecl) 282 BaseDecl = BaseType->getAsCXXRecordDecl(); 283 assert(BaseDecl && "not a C++ object?"); 284 285 if (const auto *AlreadyDerivedReg = 286 dyn_cast<CXXDerivedObjectRegion>(DerivedReg)) { 287 if (const auto *SR = 288 dyn_cast<SymbolicRegion>(AlreadyDerivedReg->getSuperRegion())) 289 if (SR->getSymbol()->getType()->getPointeeCXXRecordDecl() == BaseDecl) 290 return loc::MemRegionVal(SR); 291 292 DerivedReg = AlreadyDerivedReg->getSuperRegion(); 293 } 294 295 const MemRegion *BaseReg = MRMgr.getCXXBaseObjectRegion( 296 BaseDecl, cast<SubRegion>(DerivedReg), IsVirtual); 297 298 return loc::MemRegionVal(BaseReg); 299} 300 301/// Returns the static type of the given region, if it represents a C++ class 302/// object. 303/// 304/// This handles both fully-typed regions, where the dynamic type is known, and 305/// symbolic regions, where the dynamic type is merely bounded (and even then, 306/// only ostensibly!), but does not take advantage of any dynamic type info. 307static const CXXRecordDecl *getCXXRecordType(const MemRegion *MR) { 308 if (const auto *TVR = dyn_cast<TypedValueRegion>(MR)) 309 return TVR->getValueType()->getAsCXXRecordDecl(); 310 if (const auto *SR = dyn_cast<SymbolicRegion>(MR)) 311 return SR->getSymbol()->getType()->getPointeeCXXRecordDecl(); 312 return nullptr; 313} 314 315SVal StoreManager::attemptDownCast(SVal Base, QualType TargetType, 316 bool &Failed) { 317 Failed = false; 318 319 const MemRegion *MR = Base.getAsRegion(); 320 if (!MR) 321 return UnknownVal(); 322 323 // Assume the derived class is a pointer or a reference to a CXX record. 324 TargetType = TargetType->getPointeeType(); 325 assert(!TargetType.isNull()); 326 const CXXRecordDecl *TargetClass = TargetType->getAsCXXRecordDecl(); 327 if (!TargetClass && !TargetType->isVoidType()) 328 return UnknownVal(); 329 330 // Drill down the CXXBaseObject chains, which represent upcasts (casts from 331 // derived to base). 332 while (const CXXRecordDecl *MRClass = getCXXRecordType(MR)) { 333 // If found the derived class, the cast succeeds. 334 if (MRClass == TargetClass) 335 return loc::MemRegionVal(MR); 336 337 // We skip over incomplete types. They must be the result of an earlier 338 // reinterpret_cast, as one can only dynamic_cast between types in the same 339 // class hierarchy. 340 if (!TargetType->isVoidType() && MRClass->hasDefinition()) { 341 // Static upcasts are marked as DerivedToBase casts by Sema, so this will 342 // only happen when multiple or virtual inheritance is involved. 343 CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true, 344 /*DetectVirtual=*/false); 345 if (MRClass->isDerivedFrom(TargetClass, Paths)) 346 return evalDerivedToBase(loc::MemRegionVal(MR), Paths.front()); 347 } 348 349 if (const auto *BaseR = dyn_cast<CXXBaseObjectRegion>(MR)) { 350 // Drill down the chain to get the derived classes. 351 MR = BaseR->getSuperRegion(); 352 continue; 353 } 354 355 // If this is a cast to void*, return the region. 356 if (TargetType->isVoidType()) 357 return loc::MemRegionVal(MR); 358 359 // Strange use of reinterpret_cast can give us paths we don't reason 360 // about well, by putting in ElementRegions where we'd expect 361 // CXXBaseObjectRegions. If it's a valid reinterpret_cast (i.e. if the 362 // derived class has a zero offset from the base class), then it's safe 363 // to strip the cast; if it's invalid, -Wreinterpret-base-class should 364 // catch it. In the interest of performance, the analyzer will silently 365 // do the wrong thing in the invalid case (because offsets for subregions 366 // will be wrong). 367 const MemRegion *Uncasted = MR->StripCasts(/*IncludeBaseCasts=*/false); 368 if (Uncasted == MR) { 369 // We reached the bottom of the hierarchy and did not find the derived 370 // class. We must be casting the base to derived, so the cast should 371 // fail. 372 break; 373 } 374 375 MR = Uncasted; 376 } 377 378 // If we're casting a symbolic base pointer to a derived class, use 379 // CXXDerivedObjectRegion to represent the cast. If it's a pointer to an 380 // unrelated type, it must be a weird reinterpret_cast and we have to 381 // be fine with ElementRegion. TODO: Should we instead make 382 // Derived{TargetClass, Element{SourceClass, SR}}? 383 if (const auto *SR = dyn_cast<SymbolicRegion>(MR)) { 384 QualType T = SR->getSymbol()->getType(); 385 const CXXRecordDecl *SourceClass = T->getPointeeCXXRecordDecl(); 386 if (TargetClass && SourceClass && TargetClass->isDerivedFrom(SourceClass)) 387 return loc::MemRegionVal( 388 MRMgr.getCXXDerivedObjectRegion(TargetClass, SR)); 389 return loc::MemRegionVal(GetElementZeroRegion(SR, TargetType)); 390 } 391 392 // We failed if the region we ended up with has perfect type info. 393 Failed = isa<TypedValueRegion>(MR); 394 return UnknownVal(); 395} 396 397SVal StoreManager::getLValueFieldOrIvar(const Decl *D, SVal Base) { 398 if (Base.isUnknownOrUndef()) 399 return Base; 400 401 Loc BaseL = Base.castAs<Loc>(); 402 const SubRegion* BaseR = nullptr; 403 404 switch (BaseL.getSubKind()) { 405 case loc::MemRegionValKind: 406 BaseR = cast<SubRegion>(BaseL.castAs<loc::MemRegionVal>().getRegion()); 407 break; 408 409 case loc::GotoLabelKind: 410 // These are anormal cases. Flag an undefined value. 411 return UndefinedVal(); 412 413 case loc::ConcreteIntKind: 414 // While these seem funny, this can happen through casts. 415 // FIXME: What we should return is the field offset, not base. For example, 416 // add the field offset to the integer value. That way things 417 // like this work properly: &(((struct foo *) 0xa)->f) 418 // However, that's not easy to fix without reducing our abilities 419 // to catch null pointer dereference. Eg., ((struct foo *)0x0)->f = 7 420 // is a null dereference even though we're dereferencing offset of f 421 // rather than null. Coming up with an approach that computes offsets 422 // over null pointers properly while still being able to catch null 423 // dereferences might be worth it. 424 return Base; 425 426 default: 427 llvm_unreachable("Unhandled Base."); 428 } 429 430 // NOTE: We must have this check first because ObjCIvarDecl is a subclass 431 // of FieldDecl. 432 if (const auto *ID = dyn_cast<ObjCIvarDecl>(D)) 433 return loc::MemRegionVal(MRMgr.getObjCIvarRegion(ID, BaseR)); 434 435 return loc::MemRegionVal(MRMgr.getFieldRegion(cast<FieldDecl>(D), BaseR)); 436} 437 438SVal StoreManager::getLValueIvar(const ObjCIvarDecl *decl, SVal base) { 439 return getLValueFieldOrIvar(decl, base); 440} 441 442SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset, 443 SVal Base) { 444 // If the base is an unknown or undefined value, just return it back. 445 // FIXME: For absolute pointer addresses, we just return that value back as 446 // well, although in reality we should return the offset added to that 447 // value. See also the similar FIXME in getLValueFieldOrIvar(). 448 if (Base.isUnknownOrUndef() || Base.getAs<loc::ConcreteInt>()) 449 return Base; 450 451 if (Base.getAs<loc::GotoLabel>()) 452 return UnknownVal(); 453 454 const SubRegion *BaseRegion = 455 Base.castAs<loc::MemRegionVal>().getRegionAs<SubRegion>(); 456 457 // Pointer of any type can be cast and used as array base. 458 const auto *ElemR = dyn_cast<ElementRegion>(BaseRegion); 459 460 // Convert the offset to the appropriate size and signedness. 461 Offset = svalBuilder.convertToArrayIndex(Offset).castAs<NonLoc>(); 462 463 if (!ElemR) { 464 // If the base region is not an ElementRegion, create one. 465 // This can happen in the following example: 466 // 467 // char *p = __builtin_alloc(10); 468 // p[1] = 8; 469 // 470 // Observe that 'p' binds to an AllocaRegion. 471 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset, 472 BaseRegion, Ctx)); 473 } 474 475 SVal BaseIdx = ElemR->getIndex(); 476 477 if (!BaseIdx.getAs<nonloc::ConcreteInt>()) 478 return UnknownVal(); 479 480 const llvm::APSInt &BaseIdxI = 481 BaseIdx.castAs<nonloc::ConcreteInt>().getValue(); 482 483 // Only allow non-integer offsets if the base region has no offset itself. 484 // FIXME: This is a somewhat arbitrary restriction. We should be using 485 // SValBuilder here to add the two offsets without checking their types. 486 if (!Offset.getAs<nonloc::ConcreteInt>()) { 487 if (isa<ElementRegion>(BaseRegion->StripCasts())) 488 return UnknownVal(); 489 490 return loc::MemRegionVal(MRMgr.getElementRegion( 491 elementType, Offset, cast<SubRegion>(ElemR->getSuperRegion()), Ctx)); 492 } 493 494 const llvm::APSInt& OffI = Offset.castAs<nonloc::ConcreteInt>().getValue(); 495 assert(BaseIdxI.isSigned()); 496 497 // Compute the new index. 498 nonloc::ConcreteInt NewIdx(svalBuilder.getBasicValueFactory().getValue(BaseIdxI + 499 OffI)); 500 501 // Construct the new ElementRegion. 502 const SubRegion *ArrayR = cast<SubRegion>(ElemR->getSuperRegion()); 503 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, NewIdx, ArrayR, 504 Ctx)); 505} 506 507StoreManager::BindingsHandler::~BindingsHandler() = default; 508 509bool StoreManager::FindUniqueBinding::HandleBinding(StoreManager& SMgr, 510 Store store, 511 const MemRegion* R, 512 SVal val) { 513 SymbolRef SymV = val.getAsLocSymbol(); 514 if (!SymV || SymV != Sym) 515 return true; 516 517 if (Binding) { 518 First = false; 519 return false; 520 } 521 else 522 Binding = R; 523 524 return true; 525} 526