1//===-- RuntimeDyldImpl.h - Run-time dynamic linker for MC-JIT --*- C++ -*-===//
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// Interface for the implementations of runtime dynamic linker facilities.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
14#define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
15
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/ADT/StringMap.h"
18#include "llvm/ADT/Triple.h"
19#include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
20#include "llvm/ExecutionEngine/RuntimeDyld.h"
21#include "llvm/ExecutionEngine/RuntimeDyldChecker.h"
22#include "llvm/Object/ObjectFile.h"
23#include "llvm/Support/Debug.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/Format.h"
26#include "llvm/Support/Host.h"
27#include "llvm/Support/Mutex.h"
28#include "llvm/Support/SwapByteOrder.h"
29#include <deque>
30#include <map>
31#include <system_error>
32#include <unordered_map>
33
34using namespace llvm;
35using namespace llvm::object;
36
37namespace llvm {
38
39#define UNIMPLEMENTED_RELOC(RelType) \
40 case RelType: \
41 return make_error<RuntimeDyldError>("Unimplemented relocation: " #RelType)
42
43/// SectionEntry - represents a section emitted into memory by the dynamic
44/// linker.
45class SectionEntry {
46 /// Name - section name.
47 std::string Name;
48
49 /// Address - address in the linker's memory where the section resides.
50 uint8_t *Address;
51
52 /// Size - section size. Doesn't include the stubs.
53 size_t Size;
54
55 /// LoadAddress - the address of the section in the target process's memory.
56 /// Used for situations in which JIT-ed code is being executed in the address
57 /// space of a separate process. If the code executes in the same address
58 /// space where it was JIT-ed, this just equals Address.
59 uint64_t LoadAddress;
60
61 /// StubOffset - used for architectures with stub functions for far
62 /// relocations (like ARM).
63 uintptr_t StubOffset;
64
65 /// The total amount of space allocated for this section. This includes the
66 /// section size and the maximum amount of space that the stubs can occupy.
67 size_t AllocationSize;
68
69 /// ObjAddress - address of the section in the in-memory object file. Used
70 /// for calculating relocations in some object formats (like MachO).
71 uintptr_t ObjAddress;
72
73public:
74 SectionEntry(StringRef name, uint8_t *address, size_t size,
75 size_t allocationSize, uintptr_t objAddress)
76 : Name(std::string(name)), Address(address), Size(size),
77 LoadAddress(reinterpret_cast<uintptr_t>(address)), StubOffset(size),
78 AllocationSize(allocationSize), ObjAddress(objAddress) {
79 // AllocationSize is used only in asserts, prevent an "unused private field"
80 // warning:
81 (void)AllocationSize;
82 }
83
84 StringRef getName() const { return Name; }
85
86 uint8_t *getAddress() const { return Address; }
87
88 /// Return the address of this section with an offset.
89 uint8_t *getAddressWithOffset(unsigned OffsetBytes) const {
90 assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
91 return Address + OffsetBytes;
92 }
93
94 size_t getSize() const { return Size; }
95
96 uint64_t getLoadAddress() const { return LoadAddress; }
97 void setLoadAddress(uint64_t LA) { LoadAddress = LA; }
98
99 /// Return the load address of this section with an offset.
100 uint64_t getLoadAddressWithOffset(unsigned OffsetBytes) const {
101 assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
102 return LoadAddress + OffsetBytes;
103 }
104
105 uintptr_t getStubOffset() const { return StubOffset; }
106
107 void advanceStubOffset(unsigned StubSize) {
108 StubOffset += StubSize;
109 assert(StubOffset <= AllocationSize && "Not enough space allocated!");
110 }
111
112 uintptr_t getObjAddress() const { return ObjAddress; }
113};
114
115/// RelocationEntry - used to represent relocations internally in the dynamic
116/// linker.
117class RelocationEntry {
118public:
119 /// SectionID - the section this relocation points to.
120 unsigned SectionID;
121
122 /// Offset - offset into the section.
123 uint64_t Offset;
124
125 /// RelType - relocation type.
126 uint32_t RelType;
127
128 /// Addend - the relocation addend encoded in the instruction itself. Also
129 /// used to make a relocation section relative instead of symbol relative.
130 int64_t Addend;
131
132 struct SectionPair {
133 uint32_t SectionA;
134 uint32_t SectionB;
135 };
136
137 /// SymOffset - Section offset of the relocation entry's symbol (used for GOT
138 /// lookup).
139 union {
140 uint64_t SymOffset;
141 SectionPair Sections;
142 };
143
144 /// True if this is a PCRel relocation (MachO specific).
145 bool IsPCRel;
146
147 /// The size of this relocation (MachO specific).
148 unsigned Size;
149
150 // ARM (MachO and COFF) specific.
151 bool IsTargetThumbFunc = false;
152
153 RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend)
154 : SectionID(id), Offset(offset), RelType(type), Addend(addend),
155 SymOffset(0), IsPCRel(false), Size(0), IsTargetThumbFunc(false) {}
156
157 RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
158 uint64_t symoffset)
159 : SectionID(id), Offset(offset), RelType(type), Addend(addend),
160 SymOffset(symoffset), IsPCRel(false), Size(0),
161 IsTargetThumbFunc(false) {}
162
163 RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
164 bool IsPCRel, unsigned Size)
165 : SectionID(id), Offset(offset), RelType(type), Addend(addend),
166 SymOffset(0), IsPCRel(IsPCRel), Size(Size), IsTargetThumbFunc(false) {}
167
168 RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
169 unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
170 uint64_t SectionBOffset, bool IsPCRel, unsigned Size)
171 : SectionID(id), Offset(offset), RelType(type),
172 Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
173 Size(Size), IsTargetThumbFunc(false) {
174 Sections.SectionA = SectionA;
175 Sections.SectionB = SectionB;
176 }
177
178 RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
179 unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
180 uint64_t SectionBOffset, bool IsPCRel, unsigned Size,
181 bool IsTargetThumbFunc)
182 : SectionID(id), Offset(offset), RelType(type),
183 Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
184 Size(Size), IsTargetThumbFunc(IsTargetThumbFunc) {
185 Sections.SectionA = SectionA;
186 Sections.SectionB = SectionB;
187 }
188};
189
190class RelocationValueRef {
191public:
192 unsigned SectionID = 0;
193 uint64_t Offset = 0;
194 int64_t Addend = 0;
195 const char *SymbolName = nullptr;
196 bool IsStubThumb = false;
197
198 inline bool operator==(const RelocationValueRef &Other) const {
199 return SectionID == Other.SectionID && Offset == Other.Offset &&
200 Addend == Other.Addend && SymbolName == Other.SymbolName &&
201 IsStubThumb == Other.IsStubThumb;
202 }
203 inline bool operator<(const RelocationValueRef &Other) const {
204 if (SectionID != Other.SectionID)
205 return SectionID < Other.SectionID;
206 if (Offset != Other.Offset)
207 return Offset < Other.Offset;
208 if (Addend != Other.Addend)
209 return Addend < Other.Addend;
210 if (IsStubThumb != Other.IsStubThumb)
211 return IsStubThumb < Other.IsStubThumb;
212 return SymbolName < Other.SymbolName;
213 }
214};
215
216/// Symbol info for RuntimeDyld.
217class SymbolTableEntry {
218public:
219 SymbolTableEntry() = default;
220
221 SymbolTableEntry(unsigned SectionID, uint64_t Offset, JITSymbolFlags Flags)
222 : Offset(Offset), SectionID(SectionID), Flags(Flags) {}
223
224 unsigned getSectionID() const { return SectionID; }
225 uint64_t getOffset() const { return Offset; }
226 void setOffset(uint64_t NewOffset) { Offset = NewOffset; }
227
228 JITSymbolFlags getFlags() const { return Flags; }
229
230private:
231 uint64_t Offset = 0;
232 unsigned SectionID = 0;
233 JITSymbolFlags Flags = JITSymbolFlags::None;
234};
235
236typedef StringMap<SymbolTableEntry> RTDyldSymbolTable;
237
238class RuntimeDyldImpl {
239 friend class RuntimeDyld::LoadedObjectInfo;
240protected:
241 static const unsigned AbsoluteSymbolSection = ~0U;
242
243 // The MemoryManager to load objects into.
244 RuntimeDyld::MemoryManager &MemMgr;
245
246 // The symbol resolver to use for external symbols.
247 JITSymbolResolver &Resolver;
248
249 // A list of all sections emitted by the dynamic linker. These sections are
250 // referenced in the code by means of their index in this list - SectionID.
251 // Because references may be kept while the list grows, use a container that
252 // guarantees reference stability.
253 typedef std::deque<SectionEntry> SectionList;
254 SectionList Sections;
255
256 typedef unsigned SID; // Type for SectionIDs
257#define RTDYLD_INVALID_SECTION_ID ((RuntimeDyldImpl::SID)(-1))
258
259 // Keep a map of sections from object file to the SectionID which
260 // references it.
261 typedef std::map<SectionRef, unsigned> ObjSectionToIDMap;
262
263 // A global symbol table for symbols from all loaded modules.
264 RTDyldSymbolTable GlobalSymbolTable;
265
266 // Keep a map of common symbols to their info pairs
267 typedef std::vector<SymbolRef> CommonSymbolList;
268
269 // For each symbol, keep a list of relocations based on it. Anytime
270 // its address is reassigned (the JIT re-compiled the function, e.g.),
271 // the relocations get re-resolved.
272 // The symbol (or section) the relocation is sourced from is the Key
273 // in the relocation list where it's stored.
274 typedef SmallVector<RelocationEntry, 64> RelocationList;
275 // Relocations to sections already loaded. Indexed by SectionID which is the
276 // source of the address. The target where the address will be written is
277 // SectionID/Offset in the relocation itself.
278 std::unordered_map<unsigned, RelocationList> Relocations;
279
280 // Relocations to external symbols that are not yet resolved. Symbols are
281 // external when they aren't found in the global symbol table of all loaded
282 // modules. This map is indexed by symbol name.
283 StringMap<RelocationList> ExternalSymbolRelocations;
284
285
286 typedef std::map<RelocationValueRef, uintptr_t> StubMap;
287
288 Triple::ArchType Arch;
289 bool IsTargetLittleEndian;
290 bool IsMipsO32ABI;
291 bool IsMipsN32ABI;
292 bool IsMipsN64ABI;
293
294 // True if all sections should be passed to the memory manager, false if only
295 // sections containing relocations should be. Defaults to 'false'.
296 bool ProcessAllSections;
297
298 // This mutex prevents simultaneously loading objects from two different
299 // threads. This keeps us from having to protect individual data structures
300 // and guarantees that section allocation requests to the memory manager
301 // won't be interleaved between modules. It is also used in mapSectionAddress
302 // and resolveRelocations to protect write access to internal data structures.
303 //
304 // loadObject may be called on the same thread during the handling of of
305 // processRelocations, and that's OK. The handling of the relocation lists
306 // is written in such a way as to work correctly if new elements are added to
307 // the end of the list while the list is being processed.
308 sys::Mutex lock;
309
310 using NotifyStubEmittedFunction =
311 RuntimeDyld::NotifyStubEmittedFunction;
312 NotifyStubEmittedFunction NotifyStubEmitted;
313
314 virtual unsigned getMaxStubSize() const = 0;
315 virtual unsigned getStubAlignment() = 0;
316
317 bool HasError;
318 std::string ErrorStr;
319
320 void writeInt16BE(uint8_t *Addr, uint16_t Value) {
321 llvm::support::endian::write<uint16_t, llvm::support::unaligned>(
322 Addr, Value, IsTargetLittleEndian ? support::little : support::big);
323 }
324
325 void writeInt32BE(uint8_t *Addr, uint32_t Value) {
326 llvm::support::endian::write<uint32_t, llvm::support::unaligned>(
327 Addr, Value, IsTargetLittleEndian ? support::little : support::big);
328 }
329
330 void writeInt64BE(uint8_t *Addr, uint64_t Value) {
331 llvm::support::endian::write<uint64_t, llvm::support::unaligned>(
332 Addr, Value, IsTargetLittleEndian ? support::little : support::big);
333 }
334
335 virtual void setMipsABI(const ObjectFile &Obj) {
336 IsMipsO32ABI = false;
337 IsMipsN32ABI = false;
338 IsMipsN64ABI = false;
339 }
340
341 /// Endian-aware read Read the least significant Size bytes from Src.
342 uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const;
343
344 /// Endian-aware write. Write the least significant Size bytes from Value to
345 /// Dst.
346 void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const;
347
348 /// Generate JITSymbolFlags from a libObject symbol.
349 virtual Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &Sym);
350
351 /// Modify the given target address based on the given symbol flags.
352 /// This can be used by subclasses to tweak addresses based on symbol flags,
353 /// For example: the MachO/ARM target uses it to set the low bit if the target
354 /// is a thumb symbol.
355 virtual uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
356 JITSymbolFlags Flags) const {
357 return Addr;
358 }
359
360 /// Given the common symbols discovered in the object file, emit a
361 /// new section for them and update the symbol mappings in the object and
362 /// symbol table.
363 Error emitCommonSymbols(const ObjectFile &Obj,
364 CommonSymbolList &CommonSymbols, uint64_t CommonSize,
365 uint32_t CommonAlign);
366
367 /// Emits section data from the object file to the MemoryManager.
368 /// \param IsCode if it's true then allocateCodeSection() will be
369 /// used for emits, else allocateDataSection() will be used.
370 /// \return SectionID.
371 Expected<unsigned> emitSection(const ObjectFile &Obj,
372 const SectionRef &Section,
373 bool IsCode);
374
375 /// Find Section in LocalSections. If the secton is not found - emit
376 /// it and store in LocalSections.
377 /// \param IsCode if it's true then allocateCodeSection() will be
378 /// used for emmits, else allocateDataSection() will be used.
379 /// \return SectionID.
380 Expected<unsigned> findOrEmitSection(const ObjectFile &Obj,
381 const SectionRef &Section, bool IsCode,
382 ObjSectionToIDMap &LocalSections);
383
384 // Add a relocation entry that uses the given section.
385 void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
386
387 // Add a relocation entry that uses the given symbol. This symbol may
388 // be found in the global symbol table, or it may be external.
389 void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName);
390
391 /// Emits long jump instruction to Addr.
392 /// \return Pointer to the memory area for emitting target address.
393 uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
394
395 /// Resolves relocations from Relocs list with address from Value.
396 void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
397
398 /// A object file specific relocation resolver
399 /// \param RE The relocation to be resolved
400 /// \param Value Target symbol address to apply the relocation action
401 virtual void resolveRelocation(const RelocationEntry &RE, uint64_t Value) = 0;
402
403 /// Parses one or more object file relocations (some object files use
404 /// relocation pairs) and stores it to Relocations or SymbolRelocations
405 /// (this depends on the object file type).
406 /// \return Iterator to the next relocation that needs to be parsed.
407 virtual Expected<relocation_iterator>
408 processRelocationRef(unsigned SectionID, relocation_iterator RelI,
409 const ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID,
410 StubMap &Stubs) = 0;
411
412 void applyExternalSymbolRelocations(
413 const StringMap<JITEvaluatedSymbol> ExternalSymbolMap);
414
415 /// Resolve relocations to external symbols.
416 Error resolveExternalSymbols();
417
418 // Compute an upper bound of the memory that is required to load all
419 // sections
420 Error computeTotalAllocSize(const ObjectFile &Obj,
421 uint64_t &CodeSize, uint32_t &CodeAlign,
422 uint64_t &RODataSize, uint32_t &RODataAlign,
423 uint64_t &RWDataSize, uint32_t &RWDataAlign);
424
425 // Compute GOT size
426 unsigned computeGOTSize(const ObjectFile &Obj);
427
428 // Compute the stub buffer size required for a section
429 unsigned computeSectionStubBufSize(const ObjectFile &Obj,
430 const SectionRef &Section);
431
432 // Implementation of the generic part of the loadObject algorithm.
433 Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
434
435 // Return size of Global Offset Table (GOT) entry
436 virtual size_t getGOTEntrySize() { return 0; }
437
438 // Return true if the relocation R may require allocating a GOT entry.
439 virtual bool relocationNeedsGot(const RelocationRef &R) const {
440 return false;
441 }
442
443 // Return true if the relocation R may require allocating a stub.
444 virtual bool relocationNeedsStub(const RelocationRef &R) const {
445 return true; // Conservative answer
446 }
447
448public:
449 RuntimeDyldImpl(RuntimeDyld::MemoryManager &MemMgr,
450 JITSymbolResolver &Resolver)
451 : MemMgr(MemMgr), Resolver(Resolver),
452 ProcessAllSections(false), HasError(false) {
453 }
454
455 virtual ~RuntimeDyldImpl();
456
457 void setProcessAllSections(bool ProcessAllSections) {
458 this->ProcessAllSections = ProcessAllSections;
459 }
460
461 virtual std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
462 loadObject(const object::ObjectFile &Obj) = 0;
463
464 uint64_t getSectionLoadAddress(unsigned SectionID) const {
465 if (SectionID == AbsoluteSymbolSection)
466 return 0;
467 else
468 return Sections[SectionID].getLoadAddress();
469 }
470
471 uint8_t *getSectionAddress(unsigned SectionID) const {
472 if (SectionID == AbsoluteSymbolSection)
473 return nullptr;
474 else
475 return Sections[SectionID].getAddress();
476 }
477
478 StringRef getSectionContent(unsigned SectionID) const {
479 if (SectionID == AbsoluteSymbolSection)
480 return {};
481 else
482 return StringRef(
483 reinterpret_cast<char *>(Sections[SectionID].getAddress()),
484 Sections[SectionID].getStubOffset() + getMaxStubSize());
485 }
486
487 uint8_t* getSymbolLocalAddress(StringRef Name) const {
488 // FIXME: Just look up as a function for now. Overly simple of course.
489 // Work in progress.
490 RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
491 if (pos == GlobalSymbolTable.end())
492 return nullptr;
493 const auto &SymInfo = pos->second;
494 // Absolute symbols do not have a local address.
495 if (SymInfo.getSectionID() == AbsoluteSymbolSection)
496 return nullptr;
497 return getSectionAddress(SymInfo.getSectionID()) + SymInfo.getOffset();
498 }
499
500 unsigned getSymbolSectionID(StringRef Name) const {
501 auto GSTItr = GlobalSymbolTable.find(Name);
502 if (GSTItr == GlobalSymbolTable.end())
503 return ~0U;
504 return GSTItr->second.getSectionID();
505 }
506
507 JITEvaluatedSymbol getSymbol(StringRef Name) const {
508 // FIXME: Just look up as a function for now. Overly simple of course.
509 // Work in progress.
510 RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
511 if (pos == GlobalSymbolTable.end())
512 return nullptr;
513 const auto &SymEntry = pos->second;
514 uint64_t SectionAddr = 0;
515 if (SymEntry.getSectionID() != AbsoluteSymbolSection)
516 SectionAddr = getSectionLoadAddress(SymEntry.getSectionID());
517 uint64_t TargetAddr = SectionAddr + SymEntry.getOffset();
518
519 // FIXME: Have getSymbol should return the actual address and the client
520 // modify it based on the flags. This will require clients to be
521 // aware of the target architecture, which we should build
522 // infrastructure for.
523 TargetAddr = modifyAddressBasedOnFlags(TargetAddr, SymEntry.getFlags());
524 return JITEvaluatedSymbol(TargetAddr, SymEntry.getFlags());
525 }
526
527 std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const {
528 std::map<StringRef, JITEvaluatedSymbol> Result;
529
530 for (auto &KV : GlobalSymbolTable) {
531 auto SectionID = KV.second.getSectionID();
532 uint64_t SectionAddr = getSectionLoadAddress(SectionID);
533 Result[KV.first()] =
534 JITEvaluatedSymbol(SectionAddr + KV.second.getOffset(), KV.second.getFlags());
535 }
536
537 return Result;
538 }
539
540 void resolveRelocations();
541
542 void resolveLocalRelocations();
543
544 static void finalizeAsync(
545 std::unique_ptr<RuntimeDyldImpl> This,
546 unique_function<void(object::OwningBinary<object::ObjectFile>,
547 std::unique_ptr<RuntimeDyld::LoadedObjectInfo>,
548 Error)>
549 OnEmitted,
550 object::OwningBinary<object::ObjectFile> O,
551 std::unique_ptr<RuntimeDyld::LoadedObjectInfo> Info);
552
553 void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
554
555 void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
556
557 // Is the linker in an error state?
558 bool hasError() { return HasError; }
559
560 // Mark the error condition as handled and continue.
561 void clearError() { HasError = false; }
562
563 // Get the error message.
564 StringRef getErrorString() { return ErrorStr; }
565
566 virtual bool isCompatibleFile(const ObjectFile &Obj) const = 0;
567
568 void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
569 this->NotifyStubEmitted = std::move(NotifyStubEmitted);
570 }
571
572 virtual void registerEHFrames();
573
574 void deregisterEHFrames();
575
576 virtual Error finalizeLoad(const ObjectFile &ObjImg,
577 ObjSectionToIDMap &SectionMap) {
578 return Error::success();
579 }
580};
581
582} // end namespace llvm
583
584#endif
585