1 //===-- DWARFGdbIndex.cpp -------------------------------------------------===//
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 #include "llvm/DebugInfo/DWARF/DWARFGdbIndex.h"
11 #include "llvm/ADT/Twine.h"
12 #include "llvm/Support/ErrorHandling.h"
13 #include "llvm/Support/Format.h"
14 
15 using namespace llvm;
16 
17 // .gdb_index section format reference:
18 // https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html
19 
20 void DWARFGdbIndex::dumpCUList(raw_ostream &OS) const {
21   OS << format("\n  CU list offset = 0x%x, has %" PRId64 " entries:",
22                CuListOffset, (uint64_t)CuList.size())
23      << '\n';
24   uint32_t I = 0;
25   for (const CompUnitEntry &CU : CuList)
26     OS << format("    %d: Offset = 0x%llx, Length = 0x%llx\n", I++, CU.Offset,
27                  CU.Length);
28 }
29 
30 void DWARFGdbIndex::dumpAddressArea(raw_ostream &OS) const {
31   OS << format("\n  Address area offset = 0x%x, has %" PRId64 " entries:",
32                AddressAreaOffset, (uint64_t)AddressArea.size())
33      << '\n';
34   for (const AddressEntry &Addr : AddressArea)
35     OS << format(
36         "    Low address = 0x%llx, High address = 0x%llx, CU index = %d\n",
37         Addr.LowAddress, Addr.HighAddress, Addr.CuIndex);
38 }
39 
40 void DWARFGdbIndex::dumpSymbolTable(raw_ostream &OS) const {
41   OS << format("\n  Symbol table offset = 0x%x, size = %" PRId64
42                ", filled slots:",
43                SymbolTableOffset, (uint64_t)SymbolTable.size())
44      << '\n';
45   uint32_t I = -1;
46   for (const SymTableEntry &E : SymbolTable) {
47     ++I;
48     if (!E.NameOffset && !E.VecOffset)
49       continue;
50 
51     OS << format("    %d: Name offset = 0x%x, CU vector offset = 0x%x\n", I,
52                  E.NameOffset, E.VecOffset);
53 
54     StringRef Name = ConstantPoolStrings.substr(
55         ConstantPoolOffset - StringPoolOffset + E.NameOffset);
56 
57     auto CuVector = std::find_if(
58         ConstantPoolVectors.begin(), ConstantPoolVectors.end(),
59         [&](const std::pair<uint32_t, SmallVector<uint32_t, 0>> &V) {
60           return V.first == E.VecOffset;
61         });
62     assert(CuVector != ConstantPoolVectors.end() && "Invalid symbol table");
63     uint32_t CuVectorId = CuVector - ConstantPoolVectors.begin();
64     OS << format("      String name: %s, CU vector index: %d\n", Name.data(),
65                  CuVectorId);
66   }
67 }
68 
69 void DWARFGdbIndex::dumpConstantPool(raw_ostream &OS) const {
70   OS << format("\n  Constant pool offset = 0x%x, has %" PRId64 " CU vectors:",
71                ConstantPoolOffset, (uint64_t)ConstantPoolVectors.size());
72   uint32_t I = 0;
73   for (const auto &V : ConstantPoolVectors) {
74     OS << format("\n    %d(0x%x): ", I++, V.first);
75     for (uint32_t Val : V.second)
76       OS << format("0x%x ", Val);
77   }
78   OS << '\n';
79 }
80 
81 void DWARFGdbIndex::dump(raw_ostream &OS) {
82   if (HasError) {
83     OS << "\n<error parsing>\n";
84     return;
85   }
86 
87   if (HasContent) {
88     OS << "  Version = " << Version << '\n';
89     dumpCUList(OS);
90     dumpAddressArea(OS);
91     dumpSymbolTable(OS);
92     dumpConstantPool(OS);
93   }
94 }
95 
96 bool DWARFGdbIndex::parseImpl(DataExtractor Data) {
97   uint32_t Offset = 0;
98 
99   // Only version 7 is supported at this moment.
100   Version = Data.getU32(&Offset);
101   if (Version != 7)
102     return false;
103 
104   CuListOffset = Data.getU32(&Offset);
105   uint32_t CuTypesOffset = Data.getU32(&Offset);
106   AddressAreaOffset = Data.getU32(&Offset);
107   SymbolTableOffset = Data.getU32(&Offset);
108   ConstantPoolOffset = Data.getU32(&Offset);
109 
110   if (Offset != CuListOffset)
111     return false;
112 
113   uint32_t CuListSize = (CuTypesOffset - CuListOffset) / 16;
114   CuList.reserve(CuListSize);
115   for (uint32_t i = 0; i < CuListSize; ++i) {
116     uint64_t CuOffset = Data.getU64(&Offset);
117     uint64_t CuLength = Data.getU64(&Offset);
118     CuList.push_back({CuOffset, CuLength});
119   }
120 
121   // CU Types are no longer needed as DWARF skeleton type units never made it
122   // into the standard.
123   uint32_t CuTypesListSize = (AddressAreaOffset - CuTypesOffset) / 24;
124   if (CuTypesListSize != 0)
125     return false;
126 
127   uint32_t AddressAreaSize = (SymbolTableOffset - AddressAreaOffset) / 20;
128   AddressArea.reserve(AddressAreaSize);
129   for (uint32_t i = 0; i < AddressAreaSize; ++i) {
130     uint64_t LowAddress = Data.getU64(&Offset);
131     uint64_t HighAddress = Data.getU64(&Offset);
132     uint32_t CuIndex = Data.getU32(&Offset);
133     AddressArea.push_back({LowAddress, HighAddress, CuIndex});
134   }
135 
136   // The symbol table. This is an open addressed hash table. The size of the
137   // hash table is always a power of 2.
138   // Each slot in the hash table consists of a pair of offset_type values. The
139   // first value is the offset of the symbol's name in the constant pool. The
140   // second value is the offset of the CU vector in the constant pool.
141   // If both values are 0, then this slot in the hash table is empty. This is ok
142   // because while 0 is a valid constant pool index, it cannot be a valid index
143   // for both a string and a CU vector.
144   uint32_t SymTableSize = (ConstantPoolOffset - SymbolTableOffset) / 8;
145   SymbolTable.reserve(SymTableSize);
146   uint32_t CuVectorsTotal = 0;
147   for (uint32_t i = 0; i < SymTableSize; ++i) {
148     uint32_t NameOffset = Data.getU32(&Offset);
149     uint32_t CuVecOffset = Data.getU32(&Offset);
150     SymbolTable.push_back({NameOffset, CuVecOffset});
151     if (NameOffset || CuVecOffset)
152       ++CuVectorsTotal;
153   }
154 
155   // The constant pool. CU vectors are stored first, followed by strings.
156   // The first value is the number of CU indices in the vector. Each subsequent
157   // value is the index and symbol attributes of a CU in the CU list.
158   for (uint32_t i = 0; i < CuVectorsTotal; ++i) {
159     ConstantPoolVectors.emplace_back(0, SmallVector<uint32_t, 0>());
160     auto &Vec = ConstantPoolVectors.back();
161     Vec.first = Offset - ConstantPoolOffset;
162 
163     uint32_t Num = Data.getU32(&Offset);
164     for (uint32_t j = 0; j < Num; ++j)
165       Vec.second.push_back(Data.getU32(&Offset));
166   }
167 
168   ConstantPoolStrings = Data.getData().drop_front(Offset);
169   StringPoolOffset = Offset;
170   return true;
171 }
172 
173 void DWARFGdbIndex::parse(DataExtractor Data) {
174   HasContent = !Data.getData().empty();
175   HasError = HasContent && !parseImpl(Data);
176 }
177