1 //===- DWARFAcceleratorTable.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/DWARFAcceleratorTable.h"
11 
12 #include "llvm/ADT/SmallVector.h"
13 #include "llvm/BinaryFormat/Dwarf.h"
14 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
15 #include "llvm/DebugInfo/DWARF/DWARFRelocMap.h"
16 #include "llvm/Support/Compiler.h"
17 #include "llvm/Support/Format.h"
18 #include "llvm/Support/raw_ostream.h"
19 #include <cstddef>
20 #include <cstdint>
21 #include <utility>
22 
23 using namespace llvm;
24 
25 bool DWARFAcceleratorTable::extract() {
26   uint32_t Offset = 0;
27 
28   // Check that we can at least read the header.
29   if (!AccelSection.isValidOffset(offsetof(Header, HeaderDataLength)+4))
30     return false;
31 
32   Hdr.Magic = AccelSection.getU32(&Offset);
33   Hdr.Version = AccelSection.getU16(&Offset);
34   Hdr.HashFunction = AccelSection.getU16(&Offset);
35   Hdr.NumBuckets = AccelSection.getU32(&Offset);
36   Hdr.NumHashes = AccelSection.getU32(&Offset);
37   Hdr.HeaderDataLength = AccelSection.getU32(&Offset);
38 
39   // Check that we can read all the hashes and offsets from the
40   // section (see SourceLevelDebugging.rst for the structure of the index).
41   if (!AccelSection.isValidOffset(sizeof(Hdr) + Hdr.HeaderDataLength +
42                                   Hdr.NumBuckets*4 + Hdr.NumHashes*8))
43     return false;
44 
45   HdrData.DIEOffsetBase = AccelSection.getU32(&Offset);
46   uint32_t NumAtoms = AccelSection.getU32(&Offset);
47 
48   for (unsigned i = 0; i < NumAtoms; ++i) {
49     uint16_t AtomType = AccelSection.getU16(&Offset);
50     auto AtomForm = static_cast<dwarf::Form>(AccelSection.getU16(&Offset));
51     HdrData.Atoms.push_back(std::make_pair(AtomType, AtomForm));
52   }
53 
54   IsValid = true;
55   return true;
56 }
57 
58 uint32_t DWARFAcceleratorTable::getNumBuckets() { return Hdr.NumBuckets; }
59 uint32_t DWARFAcceleratorTable::getNumHashes() { return Hdr.NumHashes; }
60 uint32_t DWARFAcceleratorTable::getSizeHdr() { return sizeof(Hdr); }
61 uint32_t DWARFAcceleratorTable::getHeaderDataLength() {
62   return Hdr.HeaderDataLength;
63 }
64 
65 ArrayRef<std::pair<DWARFAcceleratorTable::HeaderData::AtomType,
66                    DWARFAcceleratorTable::HeaderData::Form>>
67 DWARFAcceleratorTable::getAtomsDesc() {
68   return HdrData.Atoms;
69 }
70 
71 bool DWARFAcceleratorTable::validateForms() {
72   for (auto Atom : getAtomsDesc()) {
73     DWARFFormValue FormValue(Atom.second);
74     switch (Atom.first) {
75     case dwarf::DW_ATOM_die_offset:
76     case dwarf::DW_ATOM_die_tag:
77     case dwarf::DW_ATOM_type_flags:
78       if ((!FormValue.isFormClass(DWARFFormValue::FC_Constant) &&
79            !FormValue.isFormClass(DWARFFormValue::FC_Flag)) ||
80           FormValue.getForm() == dwarf::DW_FORM_sdata)
81         return false;
82     default:
83       break;
84     }
85   }
86   return true;
87 }
88 
89 std::pair<uint32_t, dwarf::Tag>
90 DWARFAcceleratorTable::readAtoms(uint32_t &HashDataOffset) {
91   uint32_t DieOffset = dwarf::DW_INVALID_OFFSET;
92   dwarf::Tag DieTag = dwarf::DW_TAG_null;
93 
94   for (auto Atom : getAtomsDesc()) {
95     DWARFFormValue FormValue(Atom.second);
96     FormValue.extractValue(AccelSection, &HashDataOffset, NULL);
97     switch (Atom.first) {
98     case dwarf::DW_ATOM_die_offset:
99       DieOffset = *FormValue.getAsUnsignedConstant();
100       break;
101     case dwarf::DW_ATOM_die_tag:
102       DieTag = (dwarf::Tag)*FormValue.getAsUnsignedConstant();
103       break;
104     default:
105       break;
106     }
107   }
108   return {DieOffset, DieTag};
109 }
110 
111 LLVM_DUMP_METHOD void DWARFAcceleratorTable::dump(raw_ostream &OS) const {
112   if (!IsValid)
113     return;
114 
115   // Dump the header.
116   OS << "Magic = " << format("0x%08x", Hdr.Magic) << '\n'
117      << "Version = " << format("0x%04x", Hdr.Version) << '\n'
118      << "Hash function = " << format("0x%08x", Hdr.HashFunction) << '\n'
119      << "Bucket count = " << Hdr.NumBuckets << '\n'
120      << "Hashes count = " << Hdr.NumHashes << '\n'
121      << "HeaderData length = " << Hdr.HeaderDataLength << '\n'
122      << "DIE offset base = " << HdrData.DIEOffsetBase << '\n'
123      << "Number of atoms = " << HdrData.Atoms.size() << '\n';
124 
125   unsigned i = 0;
126   SmallVector<DWARFFormValue, 3> AtomForms;
127   for (const auto &Atom: HdrData.Atoms) {
128     OS << format("Atom[%d] Type: ", i++);
129     auto TypeString = dwarf::AtomTypeString(Atom.first);
130     if (!TypeString.empty())
131       OS << TypeString;
132     else
133       OS << format("DW_ATOM_Unknown_0x%x", Atom.first);
134     OS << " Form: ";
135     auto FormString = dwarf::FormEncodingString(Atom.second);
136     if (!FormString.empty())
137       OS << FormString;
138     else
139       OS << format("DW_FORM_Unknown_0x%x", Atom.second);
140     OS << '\n';
141     AtomForms.push_back(DWARFFormValue(Atom.second));
142   }
143 
144   // Now go through the actual tables and dump them.
145   uint32_t Offset = sizeof(Hdr) + Hdr.HeaderDataLength;
146   unsigned HashesBase = Offset + Hdr.NumBuckets * 4;
147   unsigned OffsetsBase = HashesBase + Hdr.NumHashes * 4;
148 
149   for (unsigned Bucket = 0; Bucket < Hdr.NumBuckets; ++Bucket) {
150     unsigned Index = AccelSection.getU32(&Offset);
151 
152     OS << format("Bucket[%d]\n", Bucket);
153     if (Index == UINT32_MAX) {
154       OS << "  EMPTY\n";
155       continue;
156     }
157 
158     for (unsigned HashIdx = Index; HashIdx < Hdr.NumHashes; ++HashIdx) {
159       unsigned HashOffset = HashesBase + HashIdx*4;
160       unsigned OffsetsOffset = OffsetsBase + HashIdx*4;
161       uint32_t Hash = AccelSection.getU32(&HashOffset);
162 
163       if (Hash % Hdr.NumBuckets != Bucket)
164         break;
165 
166       unsigned DataOffset = AccelSection.getU32(&OffsetsOffset);
167       OS << format("  Hash = 0x%08x Offset = 0x%08x\n", Hash, DataOffset);
168       if (!AccelSection.isValidOffset(DataOffset)) {
169         OS << "    Invalid section offset\n";
170         continue;
171       }
172       while (AccelSection.isValidOffsetForDataOfSize(DataOffset, 4)) {
173         unsigned StringOffset = AccelSection.getRelocatedValue(4, &DataOffset);
174         if (!StringOffset)
175           break;
176         OS << format("    Name: %08x \"%s\"\n", StringOffset,
177                      StringSection.getCStr(&StringOffset));
178         unsigned NumData = AccelSection.getU32(&DataOffset);
179         for (unsigned Data = 0; Data < NumData; ++Data) {
180           OS << format("    Data[%d] => ", Data);
181           unsigned i = 0;
182           for (auto &Atom : AtomForms) {
183             OS << format("{Atom[%d]: ", i++);
184             if (Atom.extractValue(AccelSection, &DataOffset, nullptr))
185               Atom.dump(OS);
186             else
187               OS << "Error extracting the value";
188             OS << "} ";
189           }
190           OS << '\n';
191         }
192       }
193     }
194   }
195 }
196 
197 DWARFAcceleratorTable::ValueIterator::ValueIterator(
198     const DWARFAcceleratorTable &AccelTable, unsigned Offset)
199     : AccelTable(&AccelTable), DataOffset(Offset) {
200   if (!AccelTable.AccelSection.isValidOffsetForDataOfSize(DataOffset, 4))
201     return;
202 
203   for (const auto &Atom : AccelTable.HdrData.Atoms)
204     AtomForms.push_back(DWARFFormValue(Atom.second));
205 
206   // Read the first entry.
207   NumData = AccelTable.AccelSection.getU32(&DataOffset);
208   Next();
209 }
210 
211 void DWARFAcceleratorTable::ValueIterator::Next() {
212   assert(NumData > 0 && "attempted to increment iterator past the end");
213   auto &AccelSection = AccelTable->AccelSection;
214   if (Data >= NumData ||
215       !AccelSection.isValidOffsetForDataOfSize(DataOffset, 4)) {
216     NumData = 0;
217     return;
218   }
219   for (auto &Atom : AtomForms)
220     Atom.extractValue(AccelSection, &DataOffset, nullptr);
221   ++Data;
222 }
223 
224 iterator_range<DWARFAcceleratorTable::ValueIterator>
225 DWARFAcceleratorTable::equal_range(StringRef Key) const {
226   if (!IsValid)
227     return make_range(ValueIterator(), ValueIterator());
228 
229   // Find the bucket.
230   unsigned HashValue = dwarf::djbHash(Key);
231   unsigned Bucket = HashValue % Hdr.NumBuckets;
232   unsigned BucketBase = sizeof(Hdr) + Hdr.HeaderDataLength;
233   unsigned HashesBase = BucketBase + Hdr.NumBuckets * 4;
234   unsigned OffsetsBase = HashesBase + Hdr.NumHashes * 4;
235 
236   unsigned BucketOffset = BucketBase + Bucket * 4;
237   unsigned Index = AccelSection.getU32(&BucketOffset);
238 
239   // Search through all hashes in the bucket.
240   for (unsigned HashIdx = Index; HashIdx < Hdr.NumHashes; ++HashIdx) {
241     unsigned HashOffset = HashesBase + HashIdx * 4;
242     unsigned OffsetsOffset = OffsetsBase + HashIdx * 4;
243     uint32_t Hash = AccelSection.getU32(&HashOffset);
244 
245     if (Hash % Hdr.NumBuckets != Bucket)
246       // We are already in the next bucket.
247       break;
248 
249     unsigned DataOffset = AccelSection.getU32(&OffsetsOffset);
250     unsigned StringOffset = AccelSection.getRelocatedValue(4, &DataOffset);
251     if (!StringOffset)
252       break;
253 
254     // Finally, compare the key.
255     if (Key == StringSection.getCStr(&StringOffset))
256       return make_range({*this, DataOffset}, ValueIterator());
257   }
258   return make_range(ValueIterator(), ValueIterator());
259 }
260