1//===-- SymbolizableObjectFile.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// Implementation of SymbolizableObjectFile class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "SymbolizableObjectFile.h"
15#include "llvm/Object/SymbolSize.h"
16#include "llvm/Support/DataExtractor.h"
17#include "llvm/DebugInfo/DWARF/DWARFContext.h"
18
19namespace llvm {
20namespace symbolize {
21
22using namespace object;
23
24static DILineInfoSpecifier
25getDILineInfoSpecifier(FunctionNameKind FNKind) {
26  return DILineInfoSpecifier(
27      DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, FNKind);
28}
29
30ErrorOr<std::unique_ptr<SymbolizableObjectFile>>
31SymbolizableObjectFile::create(object::ObjectFile *Obj,
32                               std::unique_ptr<DIContext> DICtx) {
33  std::unique_ptr<SymbolizableObjectFile> res(
34      new SymbolizableObjectFile(Obj, std::move(DICtx)));
35  std::unique_ptr<DataExtractor> OpdExtractor;
36  uint64_t OpdAddress = 0;
37  // Find the .opd (function descriptor) section if any, for big-endian
38  // PowerPC64 ELF.
39  if (Obj->getArch() == Triple::ppc64) {
40    for (section_iterator Section : Obj->sections()) {
41      StringRef Name;
42      StringRef Data;
43      if (auto EC = Section->getName(Name))
44        return EC;
45      if (Name == ".opd") {
46        if (auto EC = Section->getContents(Data))
47          return EC;
48        OpdExtractor.reset(new DataExtractor(Data, Obj->isLittleEndian(),
49                                             Obj->getBytesInAddress()));
50        OpdAddress = Section->getAddress();
51        break;
52      }
53    }
54  }
55  std::vector<std::pair<SymbolRef, uint64_t>> Symbols =
56      computeSymbolSizes(*Obj);
57  for (auto &P : Symbols)
58    res->addSymbol(P.first, P.second, OpdExtractor.get(), OpdAddress);
59
60  // If this is a COFF object and we didn't find any symbols, try the export
61  // table.
62  if (Symbols.empty()) {
63    if (auto *CoffObj = dyn_cast<COFFObjectFile>(Obj))
64      if (auto EC = res->addCoffExportSymbols(CoffObj))
65        return EC;
66  }
67  return std::move(res);
68}
69
70SymbolizableObjectFile::SymbolizableObjectFile(ObjectFile *Obj,
71                                               std::unique_ptr<DIContext> DICtx)
72    : Module(Obj), DebugInfoContext(std::move(DICtx)) {}
73
74namespace {
75struct OffsetNamePair {
76  uint32_t Offset;
77  StringRef Name;
78  bool operator<(const OffsetNamePair &R) const {
79    return Offset < R.Offset;
80  }
81};
82}
83
84std::error_code SymbolizableObjectFile::addCoffExportSymbols(
85    const COFFObjectFile *CoffObj) {
86  // Get all export names and offsets.
87  std::vector<OffsetNamePair> ExportSyms;
88  for (const ExportDirectoryEntryRef &Ref : CoffObj->export_directories()) {
89    StringRef Name;
90    uint32_t Offset;
91    if (auto EC = Ref.getSymbolName(Name))
92      return EC;
93    if (auto EC = Ref.getExportRVA(Offset))
94      return EC;
95    ExportSyms.push_back(OffsetNamePair{Offset, Name});
96  }
97  if (ExportSyms.empty())
98    return std::error_code();
99
100  // Sort by ascending offset.
101  array_pod_sort(ExportSyms.begin(), ExportSyms.end());
102
103  // Approximate the symbol sizes by assuming they run to the next symbol.
104  // FIXME: This assumes all exports are functions.
105  uint64_t ImageBase = CoffObj->getImageBase();
106  for (auto I = ExportSyms.begin(), E = ExportSyms.end(); I != E; ++I) {
107    OffsetNamePair &Export = *I;
108    // FIXME: The last export has a one byte size now.
109    uint32_t NextOffset = I != E ? I->Offset : Export.Offset + 1;
110    uint64_t SymbolStart = ImageBase + Export.Offset;
111    uint64_t SymbolSize = NextOffset - Export.Offset;
112    SymbolDesc SD = {SymbolStart, SymbolSize};
113    Functions.insert(std::make_pair(SD, Export.Name));
114  }
115  return std::error_code();
116}
117
118std::error_code SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol,
119                                                  uint64_t SymbolSize,
120                                                  DataExtractor *OpdExtractor,
121                                                  uint64_t OpdAddress) {
122  SymbolRef::Type SymbolType = Symbol.getType();
123  if (SymbolType != SymbolRef::ST_Function && SymbolType != SymbolRef::ST_Data)
124    return std::error_code();
125  ErrorOr<uint64_t> SymbolAddressOrErr = Symbol.getAddress();
126  if (auto EC = SymbolAddressOrErr.getError())
127    return EC;
128  uint64_t SymbolAddress = *SymbolAddressOrErr;
129  if (OpdExtractor) {
130    // For big-endian PowerPC64 ELF, symbols in the .opd section refer to
131    // function descriptors. The first word of the descriptor is a pointer to
132    // the function's code.
133    // For the purposes of symbolization, pretend the symbol's address is that
134    // of the function's code, not the descriptor.
135    uint64_t OpdOffset = SymbolAddress - OpdAddress;
136    uint32_t OpdOffset32 = OpdOffset;
137    if (OpdOffset == OpdOffset32 &&
138        OpdExtractor->isValidOffsetForAddress(OpdOffset32))
139      SymbolAddress = OpdExtractor->getAddress(&OpdOffset32);
140  }
141  ErrorOr<StringRef> SymbolNameOrErr = Symbol.getName();
142  if (auto EC = SymbolNameOrErr.getError())
143    return EC;
144  StringRef SymbolName = *SymbolNameOrErr;
145  // Mach-O symbol table names have leading underscore, skip it.
146  if (Module->isMachO() && SymbolName.size() > 0 && SymbolName[0] == '_')
147    SymbolName = SymbolName.drop_front();
148  // FIXME: If a function has alias, there are two entries in symbol table
149  // with same address size. Make sure we choose the correct one.
150  auto &M = SymbolType == SymbolRef::ST_Function ? Functions : Objects;
151  SymbolDesc SD = { SymbolAddress, SymbolSize };
152  M.insert(std::make_pair(SD, SymbolName));
153  return std::error_code();
154}
155
156// Return true if this is a 32-bit x86 PE COFF module.
157bool SymbolizableObjectFile::isWin32Module() const {
158  auto *CoffObject = dyn_cast<COFFObjectFile>(Module);
159  return CoffObject && CoffObject->getMachine() == COFF::IMAGE_FILE_MACHINE_I386;
160}
161
162uint64_t SymbolizableObjectFile::getModulePreferredBase() const {
163  if (auto *CoffObject = dyn_cast<COFFObjectFile>(Module))
164    return CoffObject->getImageBase();
165  return 0;
166}
167
168bool SymbolizableObjectFile::getNameFromSymbolTable(SymbolRef::Type Type,
169                                                    uint64_t Address,
170                                                    std::string &Name,
171                                                    uint64_t &Addr,
172                                                    uint64_t &Size) const {
173  const auto &SymbolMap = Type == SymbolRef::ST_Function ? Functions : Objects;
174  if (SymbolMap.empty())
175    return false;
176  SymbolDesc SD = { Address, Address };
177  auto SymbolIterator = SymbolMap.upper_bound(SD);
178  if (SymbolIterator == SymbolMap.begin())
179    return false;
180  --SymbolIterator;
181  if (SymbolIterator->first.Size != 0 &&
182      SymbolIterator->first.Addr + SymbolIterator->first.Size <= Address)
183    return false;
184  Name = SymbolIterator->second.str();
185  Addr = SymbolIterator->first.Addr;
186  Size = SymbolIterator->first.Size;
187  return true;
188}
189
190bool SymbolizableObjectFile::shouldOverrideWithSymbolTable(
191    FunctionNameKind FNKind, bool UseSymbolTable) const {
192  // When DWARF is used with -gline-tables-only / -gmlt, the symbol table gives
193  // better answers for linkage names than the DIContext. Otherwise, we are
194  // probably using PEs and PDBs, and we shouldn't do the override. PE files
195  // generally only contain the names of exported symbols.
196  return FNKind == FunctionNameKind::LinkageName && UseSymbolTable &&
197         isa<DWARFContext>(DebugInfoContext.get());
198}
199
200DILineInfo SymbolizableObjectFile::symbolizeCode(uint64_t ModuleOffset,
201                                                 FunctionNameKind FNKind,
202                                                 bool UseSymbolTable) const {
203  DILineInfo LineInfo;
204  if (DebugInfoContext) {
205    LineInfo = DebugInfoContext->getLineInfoForAddress(
206        ModuleOffset, getDILineInfoSpecifier(FNKind));
207  }
208  // Override function name from symbol table if necessary.
209  if (shouldOverrideWithSymbolTable(FNKind, UseSymbolTable)) {
210    std::string FunctionName;
211    uint64_t Start, Size;
212    if (getNameFromSymbolTable(SymbolRef::ST_Function, ModuleOffset,
213                               FunctionName, Start, Size)) {
214      LineInfo.FunctionName = FunctionName;
215    }
216  }
217  return LineInfo;
218}
219
220DIInliningInfo SymbolizableObjectFile::symbolizeInlinedCode(
221    uint64_t ModuleOffset, FunctionNameKind FNKind, bool UseSymbolTable) const {
222  DIInliningInfo InlinedContext;
223
224  if (DebugInfoContext)
225    InlinedContext = DebugInfoContext->getInliningInfoForAddress(
226        ModuleOffset, getDILineInfoSpecifier(FNKind));
227  // Make sure there is at least one frame in context.
228  if (InlinedContext.getNumberOfFrames() == 0)
229    InlinedContext.addFrame(DILineInfo());
230
231  // Override the function name in lower frame with name from symbol table.
232  if (shouldOverrideWithSymbolTable(FNKind, UseSymbolTable)) {
233    std::string FunctionName;
234    uint64_t Start, Size;
235    if (getNameFromSymbolTable(SymbolRef::ST_Function, ModuleOffset,
236                               FunctionName, Start, Size)) {
237      InlinedContext.getMutableFrame(InlinedContext.getNumberOfFrames() - 1)
238          ->FunctionName = FunctionName;
239    }
240  }
241
242  return InlinedContext;
243}
244
245DIGlobal SymbolizableObjectFile::symbolizeData(uint64_t ModuleOffset) const {
246  DIGlobal Res;
247  getNameFromSymbolTable(SymbolRef::ST_Data, ModuleOffset, Res.Name, Res.Start,
248                         Res.Size);
249  return Res;
250}
251
252}  // namespace symbolize
253}  // namespace llvm
254
255