1//===- SymbolizableObjectFile.cpp -----------------------------------------===//
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//
9// Implementation of SymbolizableObjectFile class.
10//
11//===----------------------------------------------------------------------===//
12
13#include "SymbolizableObjectFile.h"
14#include "llvm/ADT/STLExtras.h"
15#include "llvm/ADT/Triple.h"
16#include "llvm/BinaryFormat/COFF.h"
17#include "llvm/DebugInfo/DWARF/DWARFContext.h"
18#include "llvm/Object/COFF.h"
19#include "llvm/Object/ELFObjectFile.h"
20#include "llvm/Object/ObjectFile.h"
21#include "llvm/Object/SymbolSize.h"
22#include "llvm/Support/Casting.h"
23#include "llvm/Support/DataExtractor.h"
24#include <algorithm>
25
26using namespace llvm;
27using namespace object;
28using namespace symbolize;
29
30Expected<std::unique_ptr<SymbolizableObjectFile>>
31SymbolizableObjectFile::create(const object::ObjectFile *Obj,
32 std::unique_ptr<DIContext> DICtx,
33 bool UntagAddresses) {
34 assert(DICtx);
35 std::unique_ptr<SymbolizableObjectFile> res(
36 new SymbolizableObjectFile(Obj, std::move(DICtx), UntagAddresses));
37 std::unique_ptr<DataExtractor> OpdExtractor;
38 uint64_t OpdAddress = 0;
39 // Find the .opd (function descriptor) section if any, for big-endian
40 // PowerPC64 ELF.
41 if (Obj->getArch() == Triple::ppc64) {
42 for (section_iterator Section : Obj->sections()) {
43 Expected<StringRef> NameOrErr = Section->getName();
44 if (!NameOrErr)
45 return NameOrErr.takeError();
46
47 if (*NameOrErr == ".opd") {
48 Expected<StringRef> E = Section->getContents();
49 if (!E)
50 return E.takeError();
51 OpdExtractor.reset(new DataExtractor(*E, Obj->isLittleEndian(),
52 Obj->getBytesInAddress()));
53 OpdAddress = Section->getAddress();
54 break;
55 }
56 }
57 }
58 std::vector<std::pair<SymbolRef, uint64_t>> Symbols =
59 computeSymbolSizes(*Obj);
60 for (auto &P : Symbols)
61 if (Error E =
62 res->addSymbol(P.first, P.second, OpdExtractor.get(), OpdAddress))
63 return std::move(E);
64
65 // If this is a COFF object and we didn't find any symbols, try the export
66 // table.
67 if (Symbols.empty()) {
68 if (auto *CoffObj = dyn_cast<COFFObjectFile>(Obj))
69 if (Error E = res->addCoffExportSymbols(CoffObj))
70 return std::move(E);
71 }
72
73 std::vector<SymbolDesc> &SS = res->Symbols;
74 // Sort by (Addr,Size,Name). If several SymbolDescs share the same Addr,
75 // pick the one with the largest Size. This helps us avoid symbols with no
76 // size information (Size=0).
77 llvm::stable_sort(SS);
78 auto I = SS.begin(), E = SS.end(), J = SS.begin();
79 while (I != E) {
80 auto OI = I;
81 while (++I != E && OI->Addr == I->Addr) {
82 }
83 *J++ = I[-1];
84 }
85 SS.erase(J, SS.end());
86
87 return std::move(res);
88}
89
90SymbolizableObjectFile::SymbolizableObjectFile(const ObjectFile *Obj,
91 std::unique_ptr<DIContext> DICtx,
92 bool UntagAddresses)
93 : Module(Obj), DebugInfoContext(std::move(DICtx)),
94 UntagAddresses(UntagAddresses) {}
95
96namespace {
97
98struct OffsetNamePair {
99 uint32_t Offset;
100 StringRef Name;
101
102 bool operator<(const OffsetNamePair &R) const {
103 return Offset < R.Offset;
104 }
105};
106
107} // end anonymous namespace
108
109Error SymbolizableObjectFile::addCoffExportSymbols(
110 const COFFObjectFile *CoffObj) {
111 // Get all export names and offsets.
112 std::vector<OffsetNamePair> ExportSyms;
113 for (const ExportDirectoryEntryRef &Ref : CoffObj->export_directories()) {
114 StringRef Name;
115 uint32_t Offset;
116 if (auto EC = Ref.getSymbolName(Name))
117 return EC;
118 if (auto EC = Ref.getExportRVA(Offset))
119 return EC;
120 ExportSyms.push_back(OffsetNamePair{Offset, Name});
121 }
122 if (ExportSyms.empty())
123 return Error::success();
124
125 // Sort by ascending offset.
126 array_pod_sort(ExportSyms.begin(), ExportSyms.end());
127
128 // Approximate the symbol sizes by assuming they run to the next symbol.
129 // FIXME: This assumes all exports are functions.
130 uint64_t ImageBase = CoffObj->getImageBase();
131 for (auto I = ExportSyms.begin(), E = ExportSyms.end(); I != E; ++I) {
132 OffsetNamePair &Export = *I;
133 // FIXME: The last export has a one byte size now.
134 uint32_t NextOffset = I != E ? I->Offset : Export.Offset + 1;
135 uint64_t SymbolStart = ImageBase + Export.Offset;
136 uint64_t SymbolSize = NextOffset - Export.Offset;
137 Symbols.push_back({SymbolStart, SymbolSize, Export.Name, 0});
138 }
139 return Error::success();
140}
141
142Error SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol,
143 uint64_t SymbolSize,
144 DataExtractor *OpdExtractor,
145 uint64_t OpdAddress) {
146 // Avoid adding symbols from an unknown/undefined section.
147 const ObjectFile &Obj = *Symbol.getObject();
148 Expected<StringRef> SymbolNameOrErr = Symbol.getName();
149 if (!SymbolNameOrErr)
150 return SymbolNameOrErr.takeError();
151 StringRef SymbolName = *SymbolNameOrErr;
152
153 uint32_t ELFSymIdx =
154 Obj.isELF() ? ELFSymbolRef(Symbol).getRawDataRefImpl().d.b : 0;
155 Expected<section_iterator> Sec = Symbol.getSection();
156 if (!Sec || Obj.section_end() == *Sec) {
157 if (Obj.isELF()) {
158 // Store the (index, filename) pair for a file symbol.
159 ELFSymbolRef ESym(Symbol);
160 if (ESym.getELFType() == ELF::STT_FILE)
161 FileSymbols.emplace_back(ELFSymIdx, SymbolName);
162 }
163 return Error::success();
164 }
165
166 Expected<SymbolRef::Type> SymbolTypeOrErr = Symbol.getType();
167 if (!SymbolTypeOrErr)
168 return SymbolTypeOrErr.takeError();
169 SymbolRef::Type SymbolType = *SymbolTypeOrErr;
170 if (Obj.isELF()) {
171 // Allow function and data symbols. Additionally allow STT_NONE, which are
172 // common for functions defined in assembly.
173 uint8_t Type = ELFSymbolRef(Symbol).getELFType();
174 if (Type != ELF::STT_NOTYPE && Type != ELF::STT_FUNC &&
175 Type != ELF::STT_OBJECT && Type != ELF::STT_GNU_IFUNC)
176 return Error::success();
177 // Some STT_NOTYPE symbols are not desired. This excludes STT_SECTION and
178 // ARM mapping symbols.
179 uint32_t Flags = cantFail(Symbol.getFlags());
180 if (Flags & SymbolRef::SF_FormatSpecific)
181 return Error::success();
182 } else if (SymbolType != SymbolRef::ST_Function &&
183 SymbolType != SymbolRef::ST_Data) {
184 return Error::success();
185 }
186
187 Expected<uint64_t> SymbolAddressOrErr = Symbol.getAddress();
188 if (!SymbolAddressOrErr)
189 return SymbolAddressOrErr.takeError();
190 uint64_t SymbolAddress = *SymbolAddressOrErr;
191 if (UntagAddresses) {
192 // For kernel addresses, bits 56-63 need to be set, so we sign extend bit 55
193 // into bits 56-63 instead of masking them out.
194 SymbolAddress &= (1ull << 56) - 1;
195 SymbolAddress = (int64_t(SymbolAddress) << 8) >> 8;
196 }
197 if (OpdExtractor) {
198 // For big-endian PowerPC64 ELF, symbols in the .opd section refer to
199 // function descriptors. The first word of the descriptor is a pointer to
200 // the function's code.
201 // For the purposes of symbolization, pretend the symbol's address is that
202 // of the function's code, not the descriptor.
203 uint64_t OpdOffset = SymbolAddress - OpdAddress;
204 if (OpdExtractor->isValidOffsetForAddress(OpdOffset))
205 SymbolAddress = OpdExtractor->getAddress(&OpdOffset);
206 }
207 // Mach-O symbol table names have leading underscore, skip it.
208 if (Module->isMachO() && !SymbolName.empty() && SymbolName[0] == '_')
209 SymbolName = SymbolName.drop_front();
210
211 if (Obj.isELF() && ELFSymbolRef(Symbol).getBinding() != ELF::STB_LOCAL)
212 ELFSymIdx = 0;
213 Symbols.push_back({SymbolAddress, SymbolSize, SymbolName, ELFSymIdx});
214 return Error::success();
215}
216
217// Return true if this is a 32-bit x86 PE COFF module.
218bool SymbolizableObjectFile::isWin32Module() const {
219 auto *CoffObject = dyn_cast<COFFObjectFile>(Module);
220 return CoffObject && CoffObject->getMachine() == COFF::IMAGE_FILE_MACHINE_I386;
221}
222
223uint64_t SymbolizableObjectFile::getModulePreferredBase() const {
224 if (auto *CoffObject = dyn_cast<COFFObjectFile>(Module))
225 return CoffObject->getImageBase();
226 return 0;
227}
228
229bool SymbolizableObjectFile::getNameFromSymbolTable(
230 uint64_t Address, std::string &Name, uint64_t &Addr, uint64_t &Size,
231 std::string &FileName) const {
232 SymbolDesc SD{Address, UINT64_C(-1), StringRef(), 0};
233 auto SymbolIterator = llvm::upper_bound(Symbols, SD);
234 if (SymbolIterator == Symbols.begin())
235 return false;
236 --SymbolIterator;
237 if (SymbolIterator->Size != 0 &&
238 SymbolIterator->Addr + SymbolIterator->Size <= Address)
239 return false;
240 Name = SymbolIterator->Name.str();
241 Addr = SymbolIterator->Addr;
242 Size = SymbolIterator->Size;
243
244 if (SymbolIterator->ELFLocalSymIdx != 0) {
245 // If this is an ELF local symbol, find the STT_FILE symbol preceding
246 // SymbolIterator to get the filename. The ELF spec requires the STT_FILE
247 // symbol (if present) precedes the other STB_LOCAL symbols for the file.
248 assert(Module->isELF());
249 auto It = llvm::upper_bound(
250 FileSymbols,
251 std::make_pair(SymbolIterator->ELFLocalSymIdx, StringRef()));
252 if (It != FileSymbols.begin())
253 FileName = It[-1].second.str();
254 }
255 return true;
256}
257
258bool SymbolizableObjectFile::shouldOverrideWithSymbolTable(
259 FunctionNameKind FNKind, bool UseSymbolTable) const {
260 // When DWARF is used with -gline-tables-only / -gmlt, the symbol table gives
261 // better answers for linkage names than the DIContext. Otherwise, we are
262 // probably using PEs and PDBs, and we shouldn't do the override. PE files
263 // generally only contain the names of exported symbols.
264 return FNKind == FunctionNameKind::LinkageName && UseSymbolTable &&
265 isa<DWARFContext>(DebugInfoContext.get());
266}
267
268DILineInfo
269SymbolizableObjectFile::symbolizeCode(object::SectionedAddress ModuleOffset,
270 DILineInfoSpecifier LineInfoSpecifier,
271 bool UseSymbolTable) const {
272 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection)
273 ModuleOffset.SectionIndex =
274 getModuleSectionIndexForAddress(ModuleOffset.Address);
275 DILineInfo LineInfo =
276 DebugInfoContext->getLineInfoForAddress(ModuleOffset, LineInfoSpecifier);
277
278 // Override function name from symbol table if necessary.
279 if (shouldOverrideWithSymbolTable(LineInfoSpecifier.FNKind, UseSymbolTable)) {
280 std::string FunctionName, FileName;
281 uint64_t Start, Size;
282 if (getNameFromSymbolTable(ModuleOffset.Address, FunctionName, Start, Size,
283 FileName)) {
284 LineInfo.FunctionName = FunctionName;
285 if (LineInfo.FileName == DILineInfo::BadString && !FileName.empty())
286 LineInfo.FileName = FileName;
287 }
288 }
289 return LineInfo;
290}
291
292DIInliningInfo SymbolizableObjectFile::symbolizeInlinedCode(
293 object::SectionedAddress ModuleOffset,
294 DILineInfoSpecifier LineInfoSpecifier, bool UseSymbolTable) const {
295 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection)
296 ModuleOffset.SectionIndex =
297 getModuleSectionIndexForAddress(ModuleOffset.Address);
298 DIInliningInfo InlinedContext = DebugInfoContext->getInliningInfoForAddress(
299 ModuleOffset, LineInfoSpecifier);
300
301 // Make sure there is at least one frame in context.
302 if (InlinedContext.getNumberOfFrames() == 0)
303 InlinedContext.addFrame(DILineInfo());
304
305 // Override the function name in lower frame with name from symbol table.
306 if (shouldOverrideWithSymbolTable(LineInfoSpecifier.FNKind, UseSymbolTable)) {
307 std::string FunctionName, FileName;
308 uint64_t Start, Size;
309 if (getNameFromSymbolTable(ModuleOffset.Address, FunctionName, Start, Size,
310 FileName)) {
311 DILineInfo *LI = InlinedContext.getMutableFrame(
312 InlinedContext.getNumberOfFrames() - 1);
313 LI->FunctionName = FunctionName;
314 if (LI->FileName == DILineInfo::BadString && !FileName.empty())
315 LI->FileName = FileName;
316 }
317 }
318
319 return InlinedContext;
320}
321
322DIGlobal SymbolizableObjectFile::symbolizeData(
323 object::SectionedAddress ModuleOffset) const {
324 DIGlobal Res;
325 std::string FileName;
326 getNameFromSymbolTable(ModuleOffset.Address, Res.Name, Res.Start, Res.Size,
327 FileName);
328 return Res;
329}
330
331std::vector<DILocal> SymbolizableObjectFile::symbolizeFrame(
332 object::SectionedAddress ModuleOffset) const {
333 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection)
334 ModuleOffset.SectionIndex =
335 getModuleSectionIndexForAddress(ModuleOffset.Address);
336 return DebugInfoContext->getLocalsForAddress(ModuleOffset);
337}
338
339/// Search for the first occurence of specified Address in ObjectFile.
340uint64_t SymbolizableObjectFile::getModuleSectionIndexForAddress(
341 uint64_t Address) const {
342
343 for (SectionRef Sec : Module->sections()) {
344 if (!Sec.isText() || Sec.isVirtual())
345 continue;
346
347 if (Address >= Sec.getAddress() &&
348 Address < Sec.getAddress() + Sec.getSize())
349 return Sec.getIndex();
350 }
351
352 return object::SectionedAddress::UndefSection;
353}
354