1//===-- RuntimeDyldCOFFX86_64.h --- COFF/X86_64 specific code ---*- 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// COFF x86_x64 support for MC-JIT runtime dynamic linker.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
14#define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
15
16#include "../RuntimeDyldCOFF.h"
17#include "llvm/BinaryFormat/COFF.h"
18#include "llvm/Object/COFF.h"
19
20#define DEBUG_TYPE "dyld"
21
22namespace llvm {
23
24class RuntimeDyldCOFFX86_64 : public RuntimeDyldCOFF {
25
26private:
27 // When a module is loaded we save the SectionID of the unwind
28 // sections in a table until we receive a request to register all
29 // unregisteredEH frame sections with the memory manager.
30 SmallVector<SID, 2> UnregisteredEHFrameSections;
31 SmallVector<SID, 2> RegisteredEHFrameSections;
32 uint64_t ImageBase;
33
34 // Fake an __ImageBase pointer by returning the section with the lowest adress
35 uint64_t getImageBase() {
36 if (!ImageBase) {
37 ImageBase = std::numeric_limits<uint64_t>::max();
38 for (const SectionEntry &Section : Sections)
39 // The Sections list may contain sections that weren't loaded for
40 // whatever reason: they may be debug sections, and ProcessAllSections
41 // is false, or they may be sections that contain 0 bytes. If the
42 // section isn't loaded, the load address will be 0, and it should not
43 // be included in the ImageBase calculation.
44 if (Section.getLoadAddress() != 0)
45 ImageBase = std::min(a: ImageBase, b: Section.getLoadAddress());
46 }
47 return ImageBase;
48 }
49
50 void write32BitOffset(uint8_t *Target, int64_t Addend, uint64_t Delta) {
51 uint64_t Result = Addend + Delta;
52 assert(Result <= UINT32_MAX && "Relocation overflow");
53 writeBytesUnaligned(Value: Result, Dst: Target, Size: 4);
54 }
55
56public:
57 RuntimeDyldCOFFX86_64(RuntimeDyld::MemoryManager &MM,
58 JITSymbolResolver &Resolver)
59 : RuntimeDyldCOFF(MM, Resolver, 8, COFF::IMAGE_REL_AMD64_ADDR64),
60 ImageBase(0) {}
61
62 Align getStubAlignment() override { return Align(1); }
63
64 // 2-byte jmp instruction + 32-bit relative address + 64-bit absolute jump
65 unsigned getMaxStubSize() const override { return 14; }
66
67 // The target location for the relocation is described by RE.SectionID and
68 // RE.Offset. RE.SectionID can be used to find the SectionEntry. Each
69 // SectionEntry has three members describing its location.
70 // SectionEntry::Address is the address at which the section has been loaded
71 // into memory in the current (host) process. SectionEntry::LoadAddress is
72 // the address that the section will have in the target process.
73 // SectionEntry::ObjAddress is the address of the bits for this section in the
74 // original emitted object image (also in the current address space).
75 //
76 // Relocations will be applied as if the section were loaded at
77 // SectionEntry::LoadAddress, but they will be applied at an address based
78 // on SectionEntry::Address. SectionEntry::ObjAddress will be used to refer
79 // to Target memory contents if they are required for value calculations.
80 //
81 // The Value parameter here is the load address of the symbol for the
82 // relocation to be applied. For relocations which refer to symbols in the
83 // current object Value will be the LoadAddress of the section in which
84 // the symbol resides (RE.Addend provides additional information about the
85 // symbol location). For external symbols, Value will be the address of the
86 // symbol in the target address space.
87 void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
88 const SectionEntry &Section = Sections[RE.SectionID];
89 uint8_t *Target = Section.getAddressWithOffset(OffsetBytes: RE.Offset);
90
91 switch (RE.RelType) {
92
93 case COFF::IMAGE_REL_AMD64_REL32:
94 case COFF::IMAGE_REL_AMD64_REL32_1:
95 case COFF::IMAGE_REL_AMD64_REL32_2:
96 case COFF::IMAGE_REL_AMD64_REL32_3:
97 case COFF::IMAGE_REL_AMD64_REL32_4:
98 case COFF::IMAGE_REL_AMD64_REL32_5: {
99 uint64_t FinalAddress = Section.getLoadAddressWithOffset(OffsetBytes: RE.Offset);
100 // Delta is the distance from the start of the reloc to the end of the
101 // instruction with the reloc.
102 uint64_t Delta = 4 + (RE.RelType - COFF::IMAGE_REL_AMD64_REL32);
103 Value -= FinalAddress + Delta;
104 uint64_t Result = Value + RE.Addend;
105 assert(((int64_t)Result <= INT32_MAX) && "Relocation overflow");
106 assert(((int64_t)Result >= INT32_MIN) && "Relocation underflow");
107 writeBytesUnaligned(Value: Result, Dst: Target, Size: 4);
108 break;
109 }
110
111 case COFF::IMAGE_REL_AMD64_ADDR32NB: {
112 // ADDR32NB requires an offset less than 2GB from 'ImageBase'.
113 // The MemoryManager can make sure this is always true by forcing the
114 // memory layout to be: CodeSection < ReadOnlySection < ReadWriteSection.
115 const uint64_t ImageBase = getImageBase();
116 if (Value < ImageBase || ((Value - ImageBase) > UINT32_MAX))
117 report_fatal_error(reason: "IMAGE_REL_AMD64_ADDR32NB relocation requires an "
118 "ordered section layout");
119 else {
120 write32BitOffset(Target, Addend: RE.Addend, Delta: Value - ImageBase);
121 }
122 break;
123 }
124
125 case COFF::IMAGE_REL_AMD64_ADDR64: {
126 writeBytesUnaligned(Value: Value + RE.Addend, Dst: Target, Size: 8);
127 break;
128 }
129
130 case COFF::IMAGE_REL_AMD64_SECREL: {
131 assert(static_cast<int64_t>(RE.Addend) <= INT32_MAX && "Relocation overflow");
132 assert(static_cast<int64_t>(RE.Addend) >= INT32_MIN && "Relocation underflow");
133 writeBytesUnaligned(Value: RE.Addend, Dst: Target, Size: 4);
134 break;
135 }
136
137 case COFF::IMAGE_REL_AMD64_SECTION: {
138 assert(static_cast<int16_t>(RE.SectionID) <= INT16_MAX && "Relocation overflow");
139 assert(static_cast<int16_t>(RE.SectionID) >= INT16_MIN && "Relocation underflow");
140 writeBytesUnaligned(Value: RE.SectionID, Dst: Target, Size: 2);
141 break;
142 }
143
144 default:
145 llvm_unreachable("Relocation type not implemented yet!");
146 break;
147 }
148 }
149
150 std::tuple<uint64_t, uint64_t, uint64_t>
151 generateRelocationStub(unsigned SectionID, StringRef TargetName,
152 uint64_t Offset, uint64_t RelType, uint64_t Addend,
153 StubMap &Stubs) {
154 uintptr_t StubOffset;
155 SectionEntry &Section = Sections[SectionID];
156
157 RelocationValueRef OriginalRelValueRef;
158 OriginalRelValueRef.SectionID = SectionID;
159 OriginalRelValueRef.Offset = Offset;
160 OriginalRelValueRef.Addend = Addend;
161 OriginalRelValueRef.SymbolName = TargetName.data();
162
163 auto [Stub, Inserted] = Stubs.try_emplace(k: OriginalRelValueRef);
164 if (Inserted) {
165 LLVM_DEBUG(dbgs() << " Create a new stub function for "
166 << TargetName.data() << "\n");
167
168 StubOffset = Section.getStubOffset();
169 Stub->second = StubOffset;
170 createStubFunction(Addr: Section.getAddressWithOffset(OffsetBytes: StubOffset));
171 Section.advanceStubOffset(StubSize: getMaxStubSize());
172 } else {
173 LLVM_DEBUG(dbgs() << " Stub function found for " << TargetName.data()
174 << "\n");
175 StubOffset = Stub->second;
176 }
177
178 // FIXME: If RelType == COFF::IMAGE_REL_AMD64_ADDR32NB we should be able
179 // to ignore the __ImageBase requirement and just forward to the stub
180 // directly as an offset of this section:
181 // write32BitOffset(Section.getAddressWithOffset(Offset), 0, StubOffset);
182 // .xdata exception handler's aren't having this though.
183
184 // Resolve original relocation to stub function.
185 const RelocationEntry RE(SectionID, Offset, RelType, Addend);
186 resolveRelocation(RE, Value: Section.getLoadAddressWithOffset(OffsetBytes: StubOffset));
187
188 // adjust relocation info so resolution writes to the stub function
189 Addend = 0;
190 Offset = StubOffset + 6;
191 RelType = COFF::IMAGE_REL_AMD64_ADDR64;
192
193 return std::make_tuple(args&: Offset, args&: RelType, args&: Addend);
194 }
195
196 Expected<object::relocation_iterator>
197 processRelocationRef(unsigned SectionID,
198 object::relocation_iterator RelI,
199 const object::ObjectFile &Obj,
200 ObjSectionToIDMap &ObjSectionToID,
201 StubMap &Stubs) override {
202 // If possible, find the symbol referred to in the relocation,
203 // and the section that contains it.
204 object::symbol_iterator Symbol = RelI->getSymbol();
205 if (Symbol == Obj.symbol_end())
206 report_fatal_error(reason: "Unknown symbol in relocation");
207 auto SectionOrError = Symbol->getSection();
208 if (!SectionOrError)
209 return SectionOrError.takeError();
210 object::section_iterator SecI = *SectionOrError;
211 // If there is no section, this must be an external reference.
212 bool IsExtern = SecI == Obj.section_end();
213
214 // Determine the Addend used to adjust the relocation value.
215 uint64_t RelType = RelI->getType();
216 uint64_t Offset = RelI->getOffset();
217 uint64_t Addend = 0;
218 SectionEntry &Section = Sections[SectionID];
219 uintptr_t ObjTarget = Section.getObjAddress() + Offset;
220
221 Expected<StringRef> TargetNameOrErr = Symbol->getName();
222 if (!TargetNameOrErr)
223 return TargetNameOrErr.takeError();
224
225 StringRef TargetName = *TargetNameOrErr;
226 unsigned TargetSectionID = 0;
227 uint64_t TargetOffset = 0;
228
229 if (TargetName.starts_with(Prefix: getImportSymbolPrefix())) {
230 assert(IsExtern && "DLLImport not marked extern?");
231 TargetSectionID = SectionID;
232 TargetOffset = getDLLImportOffset(SectionID, Stubs, Name: TargetName);
233 TargetName = StringRef();
234 IsExtern = false;
235 } else if (!IsExtern) {
236 if (auto TargetSectionIDOrErr =
237 findOrEmitSection(Obj, Section: *SecI, IsCode: SecI->isText(), LocalSections&: ObjSectionToID))
238 TargetSectionID = *TargetSectionIDOrErr;
239 else
240 return TargetSectionIDOrErr.takeError();
241 TargetOffset = getSymbolOffset(Sym: *Symbol);
242 }
243
244 switch (RelType) {
245
246 case COFF::IMAGE_REL_AMD64_REL32:
247 case COFF::IMAGE_REL_AMD64_REL32_1:
248 case COFF::IMAGE_REL_AMD64_REL32_2:
249 case COFF::IMAGE_REL_AMD64_REL32_3:
250 case COFF::IMAGE_REL_AMD64_REL32_4:
251 case COFF::IMAGE_REL_AMD64_REL32_5:
252 case COFF::IMAGE_REL_AMD64_ADDR32NB: {
253 uint8_t *Displacement = (uint8_t *)ObjTarget;
254 Addend = readBytesUnaligned(Src: Displacement, Size: 4);
255
256 if (IsExtern)
257 std::tie(args&: Offset, args&: RelType, args&: Addend) = generateRelocationStub(
258 SectionID, TargetName, Offset, RelType, Addend, Stubs);
259
260 break;
261 }
262
263 case COFF::IMAGE_REL_AMD64_ADDR64: {
264 uint8_t *Displacement = (uint8_t *)ObjTarget;
265 Addend = readBytesUnaligned(Src: Displacement, Size: 8);
266 break;
267 }
268
269 default:
270 break;
271 }
272
273 LLVM_DEBUG(dbgs() << "\t\tIn Section " << SectionID << " Offset " << Offset
274 << " RelType: " << RelType << " TargetName: "
275 << TargetName << " Addend " << Addend << "\n");
276
277 if (IsExtern) {
278 RelocationEntry RE(SectionID, Offset, RelType, Addend);
279 addRelocationForSymbol(RE, SymbolName: TargetName);
280 } else {
281 RelocationEntry RE(SectionID, Offset, RelType, TargetOffset + Addend);
282 addRelocationForSection(RE, SectionID: TargetSectionID);
283 }
284
285 return ++RelI;
286 }
287
288 void registerEHFrames() override {
289 for (auto const &EHFrameSID : UnregisteredEHFrameSections) {
290 uint8_t *EHFrameAddr = Sections[EHFrameSID].getAddress();
291 uint64_t EHFrameLoadAddr = Sections[EHFrameSID].getLoadAddress();
292 size_t EHFrameSize = Sections[EHFrameSID].getSize();
293 MemMgr.registerEHFrames(Addr: EHFrameAddr, LoadAddr: EHFrameLoadAddr, Size: EHFrameSize);
294 RegisteredEHFrameSections.push_back(Elt: EHFrameSID);
295 }
296 UnregisteredEHFrameSections.clear();
297 }
298
299 Error finalizeLoad(const object::ObjectFile &Obj,
300 ObjSectionToIDMap &SectionMap) override {
301 // Look for and record the EH frame section IDs.
302 for (const auto &SectionPair : SectionMap) {
303 const object::SectionRef &Section = SectionPair.first;
304 Expected<StringRef> NameOrErr = Section.getName();
305 if (!NameOrErr)
306 return NameOrErr.takeError();
307
308 // Note unwind info is stored in .pdata but often points to .xdata
309 // with an IMAGE_REL_AMD64_ADDR32NB relocation. Using a memory manager
310 // that keeps sections ordered in relation to __ImageBase is necessary.
311 if ((*NameOrErr) == ".pdata")
312 UnregisteredEHFrameSections.push_back(Elt: SectionPair.second);
313 }
314 return Error::success();
315 }
316};
317
318} // end namespace llvm
319
320#undef DEBUG_TYPE
321
322#endif
323