xref: /freebsd/contrib/llvm-project/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFX86_64.h (revision 5b56413d04e608379c9a306373554a8e4d321bc0) 
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 
22 namespace llvm {
23 
24 class RuntimeDyldCOFFX86_64 : public RuntimeDyldCOFF {
25 
26 private:
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(ImageBase, 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(Result, Target, 4);
54   }
55 
56 public:
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(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(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(Result, Target, 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("IMAGE_REL_AMD64_ADDR32NB relocation requires an "
118                            "ordered section layout");
119       else {
120         write32BitOffset(Target, RE.Addend, Value - ImageBase);
121       }
122       break;
123     }
124 
125     case COFF::IMAGE_REL_AMD64_ADDR64: {
126       writeBytesUnaligned(Value + RE.Addend, Target, 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(RE.Addend, Target, 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(RE.SectionID, Target, 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 = Stubs.find(OriginalRelValueRef);
164     if (Stub == Stubs.end()) {
165       LLVM_DEBUG(dbgs() << " Create a new stub function for "
166                         << TargetName.data() << "\n");
167 
168       StubOffset = Section.getStubOffset();
169       Stubs[OriginalRelValueRef] = StubOffset;
170       createStubFunction(Section.getAddressWithOffset(StubOffset));
171       Section.advanceStubOffset(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, Section.getLoadAddressWithOffset(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(Offset, RelType, 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("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(getImportSymbolPrefix())) {
230       assert(IsExtern && "DLLImport not marked extern?");
231       TargetSectionID = SectionID;
232       TargetOffset = getDLLImportOffset(SectionID, Stubs, TargetName);
233       TargetName = StringRef();
234       IsExtern = false;
235     } else if (!IsExtern) {
236       if (auto TargetSectionIDOrErr =
237               findOrEmitSection(Obj, *SecI, SecI->isText(), ObjSectionToID))
238         TargetSectionID = *TargetSectionIDOrErr;
239       else
240         return TargetSectionIDOrErr.takeError();
241       TargetOffset = getSymbolOffset(*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(Displacement, 4);
255 
256       if (IsExtern)
257         std::tie(Offset, RelType, 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(Displacement, 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, TargetName);
280     } else {
281       RelocationEntry RE(SectionID, Offset, RelType, TargetOffset + Addend);
282       addRelocationForSection(RE, 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(EHFrameAddr, EHFrameLoadAddr, EHFrameSize);
294       RegisteredEHFrameSections.push_back(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(SectionPair.second);
313     }
314     return Error::success();
315   }
316 };
317 
318 } // end namespace llvm
319 
320 #undef DEBUG_TYPE
321 
322 #endif
323