1 //===-- SemaBoundsSafety.cpp - Bounds Safety specific routines-*- C++ -*---===// 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 /// \file 9 /// This file declares semantic analysis functions specific to `-fbounds-safety` 10 /// (Bounds Safety) and also its attributes when used without `-fbounds-safety` 11 /// (e.g. `counted_by`) 12 /// 13 //===----------------------------------------------------------------------===// 14 #include "clang/Sema/Sema.h" 15 16 namespace clang { 17 18 static CountAttributedType::DynamicCountPointerKind 19 getCountAttrKind(bool CountInBytes, bool OrNull) { 20 if (CountInBytes) 21 return OrNull ? CountAttributedType::SizedByOrNull 22 : CountAttributedType::SizedBy; 23 return OrNull ? CountAttributedType::CountedByOrNull 24 : CountAttributedType::CountedBy; 25 } 26 27 static const RecordDecl *GetEnclosingNamedOrTopAnonRecord(const FieldDecl *FD) { 28 const auto *RD = FD->getParent(); 29 // An unnamed struct is anonymous struct only if it's not instantiated. 30 // However, the struct may not be fully processed yet to determine 31 // whether it's anonymous or not. In that case, this function treats it as 32 // an anonymous struct and tries to find a named parent. 33 while (RD && (RD->isAnonymousStructOrUnion() || 34 (!RD->isCompleteDefinition() && RD->getName().empty()))) { 35 const auto *Parent = dyn_cast<RecordDecl>(RD->getParent()); 36 if (!Parent) 37 break; 38 RD = Parent; 39 } 40 return RD; 41 } 42 43 enum class CountedByInvalidPointeeTypeKind { 44 INCOMPLETE, 45 SIZELESS, 46 FUNCTION, 47 FLEXIBLE_ARRAY_MEMBER, 48 VALID, 49 }; 50 51 bool Sema::CheckCountedByAttrOnField(FieldDecl *FD, Expr *E, bool CountInBytes, 52 bool OrNull) { 53 // Check the context the attribute is used in 54 55 unsigned Kind = getCountAttrKind(CountInBytes, OrNull); 56 57 if (FD->getParent()->isUnion()) { 58 Diag(FD->getBeginLoc(), diag::err_count_attr_in_union) 59 << Kind << FD->getSourceRange(); 60 return true; 61 } 62 63 const auto FieldTy = FD->getType(); 64 if (FieldTy->isArrayType() && (CountInBytes || OrNull)) { 65 Diag(FD->getBeginLoc(), 66 diag::err_count_attr_not_on_ptr_or_flexible_array_member) 67 << Kind << FD->getLocation() << /* suggest counted_by */ 1; 68 return true; 69 } 70 if (!FieldTy->isArrayType() && !FieldTy->isPointerType()) { 71 Diag(FD->getBeginLoc(), 72 diag::err_count_attr_not_on_ptr_or_flexible_array_member) 73 << Kind << FD->getLocation() << /* do not suggest counted_by */ 0; 74 return true; 75 } 76 77 LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel = 78 LangOptions::StrictFlexArraysLevelKind::IncompleteOnly; 79 if (FieldTy->isArrayType() && 80 !Decl::isFlexibleArrayMemberLike(getASTContext(), FD, FieldTy, 81 StrictFlexArraysLevel, true)) { 82 Diag(FD->getBeginLoc(), 83 diag::err_counted_by_attr_on_array_not_flexible_array_member) 84 << Kind << FD->getLocation(); 85 return true; 86 } 87 88 CountedByInvalidPointeeTypeKind InvalidTypeKind = 89 CountedByInvalidPointeeTypeKind::VALID; 90 QualType PointeeTy; 91 int SelectPtrOrArr = 0; 92 if (FieldTy->isPointerType()) { 93 PointeeTy = FieldTy->getPointeeType(); 94 SelectPtrOrArr = 0; 95 } else { 96 assert(FieldTy->isArrayType()); 97 const ArrayType *AT = getASTContext().getAsArrayType(FieldTy); 98 PointeeTy = AT->getElementType(); 99 SelectPtrOrArr = 1; 100 } 101 // Note: The `Decl::isFlexibleArrayMemberLike` check earlier on means 102 // only `PointeeTy->isStructureTypeWithFlexibleArrayMember()` is reachable 103 // when `FieldTy->isArrayType()`. 104 bool ShouldWarn = false; 105 if (PointeeTy->isIncompleteType() && !CountInBytes) { 106 InvalidTypeKind = CountedByInvalidPointeeTypeKind::INCOMPLETE; 107 } else if (PointeeTy->isSizelessType()) { 108 InvalidTypeKind = CountedByInvalidPointeeTypeKind::SIZELESS; 109 } else if (PointeeTy->isFunctionType()) { 110 InvalidTypeKind = CountedByInvalidPointeeTypeKind::FUNCTION; 111 } else if (PointeeTy->isStructureTypeWithFlexibleArrayMember()) { 112 if (FieldTy->isArrayType() && !getLangOpts().BoundsSafety) { 113 // This is a workaround for the Linux kernel that has already adopted 114 // `counted_by` on a FAM where the pointee is a struct with a FAM. This 115 // should be an error because computing the bounds of the array cannot be 116 // done correctly without manually traversing every struct object in the 117 // array at runtime. To allow the code to be built this error is 118 // downgraded to a warning. 119 ShouldWarn = true; 120 } 121 InvalidTypeKind = CountedByInvalidPointeeTypeKind::FLEXIBLE_ARRAY_MEMBER; 122 } 123 124 if (InvalidTypeKind != CountedByInvalidPointeeTypeKind::VALID) { 125 unsigned DiagID = ShouldWarn 126 ? diag::warn_counted_by_attr_elt_type_unknown_size 127 : diag::err_counted_by_attr_pointee_unknown_size; 128 Diag(FD->getBeginLoc(), DiagID) 129 << SelectPtrOrArr << PointeeTy << (int)InvalidTypeKind 130 << (ShouldWarn ? 1 : 0) << Kind << FD->getSourceRange(); 131 return true; 132 } 133 134 // Check the expression 135 136 if (!E->getType()->isIntegerType() || E->getType()->isBooleanType()) { 137 Diag(E->getBeginLoc(), diag::err_count_attr_argument_not_integer) 138 << Kind << E->getSourceRange(); 139 return true; 140 } 141 142 auto *DRE = dyn_cast<DeclRefExpr>(E); 143 if (!DRE) { 144 Diag(E->getBeginLoc(), 145 diag::err_count_attr_only_support_simple_decl_reference) 146 << Kind << E->getSourceRange(); 147 return true; 148 } 149 150 auto *CountDecl = DRE->getDecl(); 151 FieldDecl *CountFD = dyn_cast<FieldDecl>(CountDecl); 152 if (auto *IFD = dyn_cast<IndirectFieldDecl>(CountDecl)) { 153 CountFD = IFD->getAnonField(); 154 } 155 if (!CountFD) { 156 Diag(E->getBeginLoc(), diag::err_count_attr_must_be_in_structure) 157 << CountDecl << Kind << E->getSourceRange(); 158 159 Diag(CountDecl->getBeginLoc(), 160 diag::note_flexible_array_counted_by_attr_field) 161 << CountDecl << CountDecl->getSourceRange(); 162 return true; 163 } 164 165 if (FD->getParent() != CountFD->getParent()) { 166 if (CountFD->getParent()->isUnion()) { 167 Diag(CountFD->getBeginLoc(), diag::err_count_attr_refer_to_union) 168 << Kind << CountFD->getSourceRange(); 169 return true; 170 } 171 // Whether CountRD is an anonymous struct is not determined at this 172 // point. Thus, an additional diagnostic in case it's not anonymous struct 173 // is done later in `Parser::ParseStructDeclaration`. 174 auto *RD = GetEnclosingNamedOrTopAnonRecord(FD); 175 auto *CountRD = GetEnclosingNamedOrTopAnonRecord(CountFD); 176 177 if (RD != CountRD) { 178 Diag(E->getBeginLoc(), diag::err_count_attr_param_not_in_same_struct) 179 << CountFD << Kind << FieldTy->isArrayType() << E->getSourceRange(); 180 Diag(CountFD->getBeginLoc(), 181 diag::note_flexible_array_counted_by_attr_field) 182 << CountFD << CountFD->getSourceRange(); 183 return true; 184 } 185 } 186 return false; 187 } 188 189 } // namespace clang 190