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
getCountAttrKind(bool CountInBytes,bool OrNull)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
GetEnclosingNamedOrTopAnonRecord(const FieldDecl * FD)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
CheckCountedByAttrOnField(FieldDecl * FD,Expr * E,llvm::SmallVectorImpl<TypeCoupledDeclRefInfo> & Decls,bool CountInBytes,bool OrNull)51 bool Sema::CheckCountedByAttrOnField(
52 FieldDecl *FD, Expr *E,
53 llvm::SmallVectorImpl<TypeCoupledDeclRefInfo> &Decls, bool CountInBytes,
54 bool OrNull) {
55 // Check the context the attribute is used in
56
57 unsigned Kind = getCountAttrKind(CountInBytes, OrNull);
58
59 if (FD->getParent()->isUnion()) {
60 Diag(FD->getBeginLoc(), diag::err_count_attr_in_union)
61 << Kind << FD->getSourceRange();
62 return true;
63 }
64
65 const auto FieldTy = FD->getType();
66 if (FieldTy->isArrayType() && (CountInBytes || OrNull)) {
67 Diag(FD->getBeginLoc(),
68 diag::err_count_attr_not_on_ptr_or_flexible_array_member)
69 << Kind << FD->getLocation() << /* suggest counted_by */ 1;
70 return true;
71 }
72 if (!FieldTy->isArrayType() && !FieldTy->isPointerType()) {
73 Diag(FD->getBeginLoc(),
74 diag::err_count_attr_not_on_ptr_or_flexible_array_member)
75 << Kind << FD->getLocation() << /* do not suggest counted_by */ 0;
76 return true;
77 }
78
79 LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel =
80 LangOptions::StrictFlexArraysLevelKind::IncompleteOnly;
81 if (FieldTy->isArrayType() &&
82 !Decl::isFlexibleArrayMemberLike(getASTContext(), FD, FieldTy,
83 StrictFlexArraysLevel, true)) {
84 Diag(FD->getBeginLoc(),
85 diag::err_counted_by_attr_on_array_not_flexible_array_member)
86 << Kind << FD->getLocation();
87 return true;
88 }
89
90 CountedByInvalidPointeeTypeKind InvalidTypeKind =
91 CountedByInvalidPointeeTypeKind::VALID;
92 QualType PointeeTy;
93 int SelectPtrOrArr = 0;
94 if (FieldTy->isPointerType()) {
95 PointeeTy = FieldTy->getPointeeType();
96 SelectPtrOrArr = 0;
97 } else {
98 assert(FieldTy->isArrayType());
99 const ArrayType *AT = getASTContext().getAsArrayType(FieldTy);
100 PointeeTy = AT->getElementType();
101 SelectPtrOrArr = 1;
102 }
103 // Note: The `Decl::isFlexibleArrayMemberLike` check earlier on means
104 // only `PointeeTy->isStructureTypeWithFlexibleArrayMember()` is reachable
105 // when `FieldTy->isArrayType()`.
106 bool ShouldWarn = false;
107 if (PointeeTy->isIncompleteType() && !CountInBytes) {
108 InvalidTypeKind = CountedByInvalidPointeeTypeKind::INCOMPLETE;
109 } else if (PointeeTy->isSizelessType()) {
110 InvalidTypeKind = CountedByInvalidPointeeTypeKind::SIZELESS;
111 } else if (PointeeTy->isFunctionType()) {
112 InvalidTypeKind = CountedByInvalidPointeeTypeKind::FUNCTION;
113 } else if (PointeeTy->isStructureTypeWithFlexibleArrayMember()) {
114 if (FieldTy->isArrayType() && !getLangOpts().BoundsSafety) {
115 // This is a workaround for the Linux kernel that has already adopted
116 // `counted_by` on a FAM where the pointee is a struct with a FAM. This
117 // should be an error because computing the bounds of the array cannot be
118 // done correctly without manually traversing every struct object in the
119 // array at runtime. To allow the code to be built this error is
120 // downgraded to a warning.
121 ShouldWarn = true;
122 }
123 InvalidTypeKind = CountedByInvalidPointeeTypeKind::FLEXIBLE_ARRAY_MEMBER;
124 }
125
126 if (InvalidTypeKind != CountedByInvalidPointeeTypeKind::VALID) {
127 unsigned DiagID = ShouldWarn
128 ? diag::warn_counted_by_attr_elt_type_unknown_size
129 : diag::err_counted_by_attr_pointee_unknown_size;
130 Diag(FD->getBeginLoc(), DiagID)
131 << SelectPtrOrArr << PointeeTy << (int)InvalidTypeKind
132 << (ShouldWarn ? 1 : 0) << Kind << FD->getSourceRange();
133 return true;
134 }
135
136 // Check the expression
137
138 if (!E->getType()->isIntegerType() || E->getType()->isBooleanType()) {
139 Diag(E->getBeginLoc(), diag::err_count_attr_argument_not_integer)
140 << Kind << E->getSourceRange();
141 return true;
142 }
143
144 auto *DRE = dyn_cast<DeclRefExpr>(E);
145 if (!DRE) {
146 Diag(E->getBeginLoc(),
147 diag::err_count_attr_only_support_simple_decl_reference)
148 << Kind << E->getSourceRange();
149 return true;
150 }
151
152 auto *CountDecl = DRE->getDecl();
153 FieldDecl *CountFD = dyn_cast<FieldDecl>(CountDecl);
154 if (auto *IFD = dyn_cast<IndirectFieldDecl>(CountDecl)) {
155 CountFD = IFD->getAnonField();
156 }
157 if (!CountFD) {
158 Diag(E->getBeginLoc(), diag::err_count_attr_must_be_in_structure)
159 << CountDecl << Kind << E->getSourceRange();
160
161 Diag(CountDecl->getBeginLoc(),
162 diag::note_flexible_array_counted_by_attr_field)
163 << CountDecl << CountDecl->getSourceRange();
164 return true;
165 }
166
167 if (FD->getParent() != CountFD->getParent()) {
168 if (CountFD->getParent()->isUnion()) {
169 Diag(CountFD->getBeginLoc(), diag::err_count_attr_refer_to_union)
170 << Kind << CountFD->getSourceRange();
171 return true;
172 }
173 // Whether CountRD is an anonymous struct is not determined at this
174 // point. Thus, an additional diagnostic in case it's not anonymous struct
175 // is done later in `Parser::ParseStructDeclaration`.
176 auto *RD = GetEnclosingNamedOrTopAnonRecord(FD);
177 auto *CountRD = GetEnclosingNamedOrTopAnonRecord(CountFD);
178
179 if (RD != CountRD) {
180 Diag(E->getBeginLoc(), diag::err_count_attr_param_not_in_same_struct)
181 << CountFD << Kind << FieldTy->isArrayType() << E->getSourceRange();
182 Diag(CountFD->getBeginLoc(),
183 diag::note_flexible_array_counted_by_attr_field)
184 << CountFD << CountFD->getSourceRange();
185 return true;
186 }
187 }
188
189 Decls.push_back(TypeCoupledDeclRefInfo(CountFD, /*IsDref*/ false));
190 return false;
191 }
192
193 } // namespace clang
194