xref: /llvm-project/llvm/lib/ExecutionEngine/Orc/Debugging/DebuggerSupportPlugin.cpp (revision 630139460ea7fe8c4b6e6ea2973830117a8048ee) 
1 //===------- DebuggerSupportPlugin.cpp - Utils for debugger support -------===//
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 //
10 //===----------------------------------------------------------------------===//
11 
12 #include "llvm/ExecutionEngine/Orc/Debugging/DebuggerSupportPlugin.h"
13 #include "llvm/ExecutionEngine/Orc/MachOBuilder.h"
14 
15 #include "llvm/ADT/SmallSet.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/BinaryFormat/MachO.h"
18 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
19 #include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
20 
21 #include <chrono>
22 
23 #define DEBUG_TYPE "orc"
24 
25 using namespace llvm;
26 using namespace llvm::jitlink;
27 using namespace llvm::orc;
28 
29 static const char *SynthDebugSectionName = "__jitlink_synth_debug_object";
30 
31 namespace {
32 
33 class MachODebugObjectSynthesizerBase
34     : public GDBJITDebugInfoRegistrationPlugin::DebugSectionSynthesizer {
35 public:
36   static bool isDebugSection(Section &Sec) {
37     return Sec.getName().starts_with("__DWARF,");
38   }
39 
40   MachODebugObjectSynthesizerBase(LinkGraph &G, ExecutorAddr RegisterActionAddr)
41       : G(G), RegisterActionAddr(RegisterActionAddr) {}
42   virtual ~MachODebugObjectSynthesizerBase() = default;
43 
44   Error preserveDebugSections() {
45     if (G.findSectionByName(SynthDebugSectionName)) {
46       LLVM_DEBUG({
47         dbgs() << "MachODebugObjectSynthesizer skipping graph " << G.getName()
48                << " which contains an unexpected existing "
49                << SynthDebugSectionName << " section.\n";
50       });
51       return Error::success();
52     }
53 
54     LLVM_DEBUG({
55       dbgs() << "MachODebugObjectSynthesizer visiting graph " << G.getName()
56              << "\n";
57     });
58     for (auto &Sec : G.sections()) {
59       if (!isDebugSection(Sec))
60         continue;
61       // Preserve blocks in this debug section by marking one existing symbol
62       // live for each block, and introducing a new live, anonymous symbol for
63       // each currently unreferenced block.
64       LLVM_DEBUG({
65         dbgs() << "  Preserving debug section " << Sec.getName() << "\n";
66       });
67       SmallSet<Block *, 8> PreservedBlocks;
68       for (auto *Sym : Sec.symbols()) {
69         bool NewPreservedBlock =
70             PreservedBlocks.insert(&Sym->getBlock()).second;
71         if (NewPreservedBlock)
72           Sym->setLive(true);
73       }
74       for (auto *B : Sec.blocks())
75         if (!PreservedBlocks.count(B))
76           G.addAnonymousSymbol(*B, 0, 0, false, true);
77     }
78 
79     return Error::success();
80   }
81 
82 protected:
83   LinkGraph &G;
84   ExecutorAddr RegisterActionAddr;
85 };
86 
87 template <typename MachOTraits>
88 class MachODebugObjectSynthesizer : public MachODebugObjectSynthesizerBase {
89 public:
90   MachODebugObjectSynthesizer(ExecutionSession &ES, LinkGraph &G,
91                               ExecutorAddr RegisterActionAddr)
92       : MachODebugObjectSynthesizerBase(G, RegisterActionAddr),
93         Builder(ES.getPageSize()) {}
94 
95   using MachODebugObjectSynthesizerBase::MachODebugObjectSynthesizerBase;
96 
97   Error startSynthesis() override {
98     LLVM_DEBUG({
99       dbgs() << "Creating " << SynthDebugSectionName << " for " << G.getName()
100              << "\n";
101     });
102 
103     for (auto &Sec : G.sections()) {
104       if (Sec.blocks().empty())
105         continue;
106 
107       // Skip sections whose name's don't fit the MachO standard.
108       if (Sec.getName().empty() || Sec.getName().size() > 33 ||
109           Sec.getName().find(',') > 16)
110         continue;
111 
112       if (isDebugSection(Sec))
113         DebugSections.push_back({&Sec, nullptr});
114       else if (Sec.getMemLifetime() != MemLifetime::NoAlloc)
115         NonDebugSections.push_back({&Sec, nullptr});
116     }
117 
118     // Bail out early if no debug sections.
119     if (DebugSections.empty())
120       return Error::success();
121 
122     // Write MachO header and debug section load commands.
123     Builder.Header.filetype = MachO::MH_OBJECT;
124     if (auto CPUType = MachO::getCPUType(G.getTargetTriple()))
125       Builder.Header.cputype = *CPUType;
126     else
127       return CPUType.takeError();
128     if (auto CPUSubType = MachO::getCPUSubType(G.getTargetTriple()))
129       Builder.Header.cpusubtype = *CPUSubType;
130     else
131       return CPUSubType.takeError();
132 
133     Seg = &Builder.addSegment("");
134 
135     StringMap<std::unique_ptr<MemoryBuffer>> DebugSectionMap;
136     StringRef DebugLineSectionData;
137     for (auto &DSec : DebugSections) {
138       auto [SegName, SecName] = DSec.GraphSec->getName().split(',');
139       DSec.BuilderSec = &Seg->addSection(SecName, SegName);
140 
141       SectionRange SR(*DSec.GraphSec);
142       DSec.BuilderSec->Content.Size = SR.getSize();
143       if (!SR.empty()) {
144         DSec.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());
145         StringRef SectionData(SR.getFirstBlock()->getContent().data(),
146                               SR.getFirstBlock()->getSize());
147         DebugSectionMap[SecName.drop_front(2)] = // drop "__" prefix.
148             MemoryBuffer::getMemBuffer(SectionData, G.getName(), false);
149         if (SecName == "__debug_line")
150           DebugLineSectionData = SectionData;
151       }
152     }
153 
154     std::optional<StringRef> FileName;
155     if (!DebugLineSectionData.empty()) {
156       assert((G.getEndianness() == llvm::endianness::big ||
157               G.getEndianness() == llvm::endianness::little) &&
158              "G.getEndianness() must be either big or little");
159       auto DWARFCtx =
160           DWARFContext::create(DebugSectionMap, G.getPointerSize(),
161                                G.getEndianness() == llvm::endianness::little);
162       DWARFDataExtractor DebugLineData(
163           DebugLineSectionData, G.getEndianness() == llvm::endianness::little,
164           G.getPointerSize());
165       uint64_t Offset = 0;
166       DWARFDebugLine::Prologue P;
167 
168       // Try to parse line data. Consume error on failure.
169       if (auto Err = P.parse(DebugLineData, &Offset, consumeError, *DWARFCtx)) {
170         handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
171           LLVM_DEBUG({
172             dbgs() << "Cannot parse line table for \"" << G.getName() << "\": ";
173             EIB.log(dbgs());
174             dbgs() << "\n";
175           });
176         });
177       } else {
178         for (auto &FN : P.FileNames)
179           if ((FileName = dwarf::toString(FN.Name))) {
180             LLVM_DEBUG({
181               dbgs() << "Using FileName = \"" << *FileName
182                      << "\" from DWARF line table\n";
183             });
184             break;
185           }
186       }
187     }
188 
189     // If no line table (or unable to use) then use graph name.
190     // FIXME: There are probably other debug sections we should look in first.
191     if (!FileName) {
192       LLVM_DEBUG({
193         dbgs() << "Could not find source name from DWARF line table. "
194                   "Using FileName = \"\"\n";
195       });
196       FileName = "";
197     }
198 
199     Builder.addSymbol("", MachO::N_SO, 0, 0, 0);
200     Builder.addSymbol(*FileName, MachO::N_SO, 0, 0, 0);
201     auto TimeStamp = std::chrono::duration_cast<std::chrono::seconds>(
202                          std::chrono::system_clock::now().time_since_epoch())
203                          .count();
204     Builder.addSymbol("", MachO::N_OSO, 3, 1, TimeStamp);
205 
206     for (auto &NDSP : NonDebugSections) {
207       auto [SegName, SecName] = NDSP.GraphSec->getName().split(',');
208       NDSP.BuilderSec = &Seg->addSection(SecName, SegName);
209       SectionRange SR(*NDSP.GraphSec);
210       if (!SR.empty())
211         NDSP.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());
212 
213       // Add stabs.
214       for (auto *Sym : NDSP.GraphSec->symbols()) {
215         // Skip anonymous symbols.
216         if (!Sym->hasName())
217           continue;
218 
219         uint8_t SymType = Sym->isCallable() ? MachO::N_FUN : MachO::N_GSYM;
220 
221         Builder.addSymbol("", MachO::N_BNSYM, 1, 0, 0);
222         StabSymbols.push_back(
223             {*Sym, Builder.addSymbol(*Sym->getName(), SymType, 1, 0, 0),
224              Builder.addSymbol(*Sym->getName(), SymType, 0, 0, 0)});
225         Builder.addSymbol("", MachO::N_ENSYM, 1, 0, 0);
226       }
227     }
228 
229     Builder.addSymbol("", MachO::N_SO, 1, 0, 0);
230 
231     // Lay out the debug object, create a section and block for it.
232     size_t DebugObjectSize = Builder.layout();
233 
234     auto &SDOSec = G.createSection(SynthDebugSectionName, MemProt::Read);
235     MachOContainerBlock = &G.createMutableContentBlock(
236         SDOSec, G.allocateBuffer(DebugObjectSize), orc::ExecutorAddr(), 8, 0);
237 
238     return Error::success();
239   }
240 
241   Error completeSynthesisAndRegister() override {
242     if (!MachOContainerBlock) {
243       LLVM_DEBUG({
244         dbgs() << "Not writing MachO debug object header for " << G.getName()
245                << " since createDebugSection failed\n";
246       });
247 
248       return Error::success();
249     }
250     ExecutorAddr MaxAddr;
251     for (auto &NDSec : NonDebugSections) {
252       SectionRange SR(*NDSec.GraphSec);
253       NDSec.BuilderSec->addr = SR.getStart().getValue();
254       NDSec.BuilderSec->size = SR.getSize();
255       NDSec.BuilderSec->offset = SR.getStart().getValue();
256       if (SR.getEnd() > MaxAddr)
257         MaxAddr = SR.getEnd();
258     }
259 
260     for (auto &DSec : DebugSections) {
261       if (DSec.GraphSec->blocks_size() != 1)
262         return make_error<StringError>(
263             "Unexpected number of blocks in debug info section",
264             inconvertibleErrorCode());
265 
266       if (ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size > MaxAddr)
267         MaxAddr = ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size;
268 
269       auto &B = **DSec.GraphSec->blocks().begin();
270       DSec.BuilderSec->Content.Data = B.getContent().data();
271       DSec.BuilderSec->Content.Size = B.getContent().size();
272       DSec.BuilderSec->flags |= MachO::S_ATTR_DEBUG;
273     }
274 
275     LLVM_DEBUG({
276       dbgs() << "Writing MachO debug object header for " << G.getName() << "\n";
277     });
278 
279     // Update stab symbol addresses.
280     for (auto &SS : StabSymbols) {
281       SS.StartStab.nlist().n_value = SS.Sym.getAddress().getValue();
282       SS.EndStab.nlist().n_value = SS.Sym.getSize();
283     }
284 
285     Builder.write(MachOContainerBlock->getAlreadyMutableContent());
286 
287     static constexpr bool AutoRegisterCode = true;
288     SectionRange R(MachOContainerBlock->getSection());
289     G.allocActions().push_back(
290         {cantFail(shared::WrapperFunctionCall::Create<
291                   shared::SPSArgList<shared::SPSExecutorAddrRange, bool>>(
292              RegisterActionAddr, R.getRange(), AutoRegisterCode)),
293          {}});
294 
295     return Error::success();
296   }
297 
298 private:
299   struct SectionPair {
300     Section *GraphSec = nullptr;
301     typename MachOBuilder<MachOTraits>::Section *BuilderSec = nullptr;
302   };
303 
304   struct StabSymbolsEntry {
305     using RelocTarget = typename MachOBuilder<MachOTraits>::RelocTarget;
306 
307     StabSymbolsEntry(Symbol &Sym, RelocTarget StartStab, RelocTarget EndStab)
308         : Sym(Sym), StartStab(StartStab), EndStab(EndStab) {}
309 
310     Symbol &Sym;
311     RelocTarget StartStab, EndStab;
312   };
313 
314   using BuilderType = MachOBuilder<MachOTraits>;
315 
316   Block *MachOContainerBlock = nullptr;
317   MachOBuilder<MachOTraits> Builder;
318   typename MachOBuilder<MachOTraits>::Segment *Seg = nullptr;
319   std::vector<StabSymbolsEntry> StabSymbols;
320   SmallVector<SectionPair, 16> DebugSections;
321   SmallVector<SectionPair, 16> NonDebugSections;
322 };
323 
324 } // end anonymous namespace
325 
326 namespace llvm {
327 namespace orc {
328 
329 Expected<std::unique_ptr<GDBJITDebugInfoRegistrationPlugin>>
330 GDBJITDebugInfoRegistrationPlugin::Create(ExecutionSession &ES,
331                                           JITDylib &ProcessJD,
332                                           const Triple &TT) {
333   auto RegisterActionAddr =
334       TT.isOSBinFormatMachO()
335           ? ES.intern("_llvm_orc_registerJITLoaderGDBAllocAction")
336           : ES.intern("llvm_orc_registerJITLoaderGDBAllocAction");
337 
338   if (auto RegisterSym = ES.lookup({&ProcessJD}, RegisterActionAddr))
339     return std::make_unique<GDBJITDebugInfoRegistrationPlugin>(
340         RegisterSym->getAddress());
341   else
342     return RegisterSym.takeError();
343 }
344 
345 Error GDBJITDebugInfoRegistrationPlugin::notifyFailed(
346     MaterializationResponsibility &MR) {
347   return Error::success();
348 }
349 
350 Error GDBJITDebugInfoRegistrationPlugin::notifyRemovingResources(
351     JITDylib &JD, ResourceKey K) {
352   return Error::success();
353 }
354 
355 void GDBJITDebugInfoRegistrationPlugin::notifyTransferringResources(
356     JITDylib &JD, ResourceKey DstKey, ResourceKey SrcKey) {}
357 
358 void GDBJITDebugInfoRegistrationPlugin::modifyPassConfig(
359     MaterializationResponsibility &MR, LinkGraph &LG,
360     PassConfiguration &PassConfig) {
361 
362   if (LG.getTargetTriple().getObjectFormat() == Triple::MachO)
363     modifyPassConfigForMachO(MR, LG, PassConfig);
364   else {
365     LLVM_DEBUG({
366       dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unspported graph "
367              << LG.getName() << "(triple = " << LG.getTargetTriple().str()
368              << "\n";
369     });
370   }
371 }
372 
373 void GDBJITDebugInfoRegistrationPlugin::modifyPassConfigForMachO(
374     MaterializationResponsibility &MR, jitlink::LinkGraph &LG,
375     jitlink::PassConfiguration &PassConfig) {
376 
377   switch (LG.getTargetTriple().getArch()) {
378   case Triple::x86_64:
379   case Triple::aarch64:
380     // Supported, continue.
381     assert(LG.getPointerSize() == 8 && "Graph has incorrect pointer size");
382     assert(LG.getEndianness() == llvm::endianness::little &&
383            "Graph has incorrect endianness");
384     break;
385   default:
386     // Unsupported.
387     LLVM_DEBUG({
388       dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unsupported "
389              << "MachO graph " << LG.getName()
390              << "(triple = " << LG.getTargetTriple().str()
391              << ", pointer size = " << LG.getPointerSize() << ", endianness = "
392              << (LG.getEndianness() == llvm::endianness::big ? "big" : "little")
393              << ")\n";
394     });
395     return;
396   }
397 
398   // Scan for debug sections. If we find one then install passes.
399   bool HasDebugSections = false;
400   for (auto &Sec : LG.sections())
401     if (MachODebugObjectSynthesizerBase::isDebugSection(Sec)) {
402       HasDebugSections = true;
403       break;
404     }
405 
406   if (HasDebugSections) {
407     LLVM_DEBUG({
408       dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
409              << " contains debug info. Installing debugger support passes.\n";
410     });
411 
412     auto MDOS = std::make_shared<MachODebugObjectSynthesizer<MachO64LE>>(
413         MR.getTargetJITDylib().getExecutionSession(), LG, RegisterActionAddr);
414     PassConfig.PrePrunePasses.push_back(
415         [=](LinkGraph &G) { return MDOS->preserveDebugSections(); });
416     PassConfig.PostPrunePasses.push_back(
417         [=](LinkGraph &G) { return MDOS->startSynthesis(); });
418     PassConfig.PostFixupPasses.push_back(
419         [=](LinkGraph &G) { return MDOS->completeSynthesisAndRegister(); });
420   } else {
421     LLVM_DEBUG({
422       dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
423              << " contains no debug info. Skipping.\n";
424     });
425   }
426 }
427 
428 } // namespace orc
429 } // namespace llvm
430