1 /*
2 * Copyright (c) 2017 VMware, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <memory>
18 #include <string>
19
20 #include <clang/AST/ASTContext.h>
21 #include <clang/AST/RecordLayout.h>
22 #include <clang/AST/RecursiveASTVisitor.h>
23 #include <llvm/ADT/StringExtras.h>
24 #include <llvm/Config/llvm-config.h>
25 #include "common.h"
26 #include "table_desc.h"
27
28 namespace ebpf {
29
30 using std::string;
31 using std::to_string;
32 using std::unique_ptr;
33 using namespace clang;
34
35 // Helper visitor for constructing a string representation of a key/leaf decl
36 class BMapDeclVisitor : public clang::RecursiveASTVisitor<BMapDeclVisitor> {
37 public:
38 explicit BMapDeclVisitor(clang::ASTContext &C, std::string &result);
39 bool TraverseRecordDecl(clang::RecordDecl *Decl);
40 bool VisitRecordDecl(clang::RecordDecl *Decl);
41 bool VisitFieldDecl(clang::FieldDecl *Decl);
42 bool VisitBuiltinType(const clang::BuiltinType *T);
43 bool VisitTypedefType(const clang::TypedefType *T);
44 bool VisitTagType(const clang::TagType *T);
45 bool VisitPointerType(const clang::PointerType *T);
46 bool VisitEnumDecl(clang::EnumDecl *D);
47 bool VisitAttr(clang::Attr *A);
48
49 private:
50 bool shouldSkipPadding(const RecordDecl *D);
51 void genJSONForField(FieldDecl *F);
52
53 private:
54 clang::ASTContext &C;
55 std::string &result_;
56 };
57
58 // Encode the struct layout as a json description
BMapDeclVisitor(ASTContext & C,string & result)59 BMapDeclVisitor::BMapDeclVisitor(ASTContext &C, string &result) : C(C), result_(result) {}
60
shouldSkipPadding(const RecordDecl * D)61 bool BMapDeclVisitor::shouldSkipPadding(const RecordDecl *D) {
62 if (D->isUnion() || D->field_empty())
63 return true;
64 for (auto F : D->getDefinition()->fields()) {
65 if (F->isBitField())
66 return true;
67 QualType Ty = F->getType();
68 if (Ty->isIncompleteArrayType())
69 return true;
70 }
71 return false;
72 }
73
genJSONForField(FieldDecl * F)74 void BMapDeclVisitor::genJSONForField(FieldDecl *F) {
75 if (F->isAnonymousStructOrUnion()) {
76 if (const RecordType *R = dyn_cast<RecordType>(F->getType()))
77 TraverseDecl(R->getDecl());
78 result_ += ", ";
79 return;
80 }
81 result_ += "[";
82 TraverseDecl(F);
83 if (const ConstantArrayType *T = dyn_cast<ConstantArrayType>(F->getType()))
84 #if LLVM_VERSION_MAJOR >= 13
85 result_ += ", [" + toString(T->getSize(), 10, false) + "]";
86 #else
87 result_ += ", [" + T->getSize().toString(10, false) + "]";
88 #endif
89 if (F->isBitField())
90 result_ += ", " + to_string(F->getBitWidthValue(C));
91 result_ += "], ";
92 }
93
VisitFieldDecl(FieldDecl * D)94 bool BMapDeclVisitor::VisitFieldDecl(FieldDecl *D) {
95 result_ += "\"";
96 result_ += D->getName();
97 result_ += "\",";
98 return true;
99 }
100
VisitEnumDecl(EnumDecl * D)101 bool BMapDeclVisitor::VisitEnumDecl(EnumDecl *D) {
102 TraverseType(D->getIntegerType());
103 return false;
104 }
105
TraverseRecordDecl(RecordDecl * D)106 bool BMapDeclVisitor::TraverseRecordDecl(RecordDecl *D) {
107 // skip children, handled in Visit...
108 if (!WalkUpFromRecordDecl(D))
109 return false;
110 return true;
111 }
112
VisitRecordDecl(RecordDecl * D)113 bool BMapDeclVisitor::VisitRecordDecl(RecordDecl *D) {
114 result_ += "[\"";
115 result_ += D->getName();
116 result_ += "\", [";
117
118 bool SkipPadding = shouldSkipPadding(D);
119 if (SkipPadding) {
120 for (auto F : D->getDefinition()->fields()) {
121 genJSONForField(F);
122 }
123 } else {
124 const ASTRecordLayout &Layout = C.getASTRecordLayout(D);
125 CharUnits Offset = C.toCharUnitsFromBits(Layout.getFieldOffset(0));
126 for (auto F : D->getDefinition()->fields()) {
127 CharUnits FieldSize = C.getTypeSizeInChars(F->getType());
128 auto FieldOffsetBits = Layout.getFieldOffset(F->getFieldIndex());
129 CharUnits FieldOffset = C.toCharUnitsFromBits(FieldOffsetBits);
130
131 uint64_t Padding = (FieldOffset - Offset).getQuantity();
132 if (Padding) {
133 /* Padding before this field with "char __pad_<FieldIndex>[Padding]". */
134 result_ += "[\"__pad_" + to_string(F->getFieldIndex()) + "\",\"char\",["
135 + to_string(Padding) + "]], ";
136 }
137 Offset = FieldOffset + FieldSize;
138 genJSONForField(F);
139 }
140
141 /* Additional Padding after the last field so that the Record Size matches */
142 CharUnits RecordSize = Layout.getSize();
143 if (RecordSize > Offset) {
144 result_ += "[\"__pad_end\",\"char\",["
145 + to_string((RecordSize - Offset).getQuantity()) + "]], ";
146 }
147 }
148
149 if (!D->getDefinition()->field_empty())
150 result_.erase(result_.end() - 2);
151 result_ += "]";
152 if (D->isUnion())
153 result_ += ", \"union\"";
154 else if (D->isStruct()) {
155 if (SkipPadding)
156 result_ += ", \"struct\"";
157 else
158 result_ += ", \"struct_packed\"";
159 }
160 result_ += "]";
161 return true;
162 }
163 // pointer to anything should be treated as terminal, don't recurse further
VisitPointerType(const PointerType * T)164 bool BMapDeclVisitor::VisitPointerType(const PointerType *T) {
165 result_ += "\"unsigned long long\"";
166 return false;
167 }
VisitTagType(const TagType * T)168 bool BMapDeclVisitor::VisitTagType(const TagType *T) {
169 return TraverseDecl(T->getDecl()->getDefinition());
170 }
VisitTypedefType(const TypedefType * T)171 bool BMapDeclVisitor::VisitTypedefType(const TypedefType *T) { return TraverseDecl(T->getDecl()); }
VisitBuiltinType(const BuiltinType * T)172 bool BMapDeclVisitor::VisitBuiltinType(const BuiltinType *T) {
173 result_ += "\"";
174 result_ += T->getName(C.getPrintingPolicy());
175 result_ += "\"";
176 return true;
177 }
VisitAttr(clang::Attr * A)178 bool BMapDeclVisitor::VisitAttr(clang::Attr *A) { return false; }
179
180 class JsonMapTypesVisitor : public virtual MapTypesVisitor {
181 public:
Visit(TableDesc & desc,clang::ASTContext & C,clang::QualType key_type,clang::QualType leaf_type)182 virtual void Visit(TableDesc &desc, clang::ASTContext &C, clang::QualType key_type,
183 clang::QualType leaf_type) {
184 BMapDeclVisitor v1(C, desc.key_desc), v2(C, desc.leaf_desc);
185 v1.TraverseType(key_type);
186 v2.TraverseType(leaf_type);
187 }
188 };
189
createJsonMapTypesVisitor()190 unique_ptr<MapTypesVisitor> createJsonMapTypesVisitor() {
191 return make_unique<JsonMapTypesVisitor>();
192 }
193
194 } // namespace ebpf
195