LLVM 19.0.0git
ELF_x86_64.cpp
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1//===---- ELF_x86_64.cpp -JIT linker implementation for ELF/x86-64 ----===//
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// ELF/x86-64 jit-link implementation.
10//
11//===----------------------------------------------------------------------===//
12
19
21#include "EHFrameSupportImpl.h"
22#include "ELFLinkGraphBuilder.h"
23#include "JITLinkGeneric.h"
24
25#define DEBUG_TYPE "jitlink"
26
27using namespace llvm;
28using namespace llvm::jitlink;
29
30namespace {
31
32constexpr StringRef ELFGOTSymbolName = "_GLOBAL_OFFSET_TABLE_";
33constexpr StringRef ELFTLSInfoSectionName = "$__TLSINFO";
34
35class TLSInfoTableManager_ELF_x86_64
36 : public TableManager<TLSInfoTableManager_ELF_x86_64> {
37public:
38 static const uint8_t TLSInfoEntryContent[16];
39
40 static StringRef getSectionName() { return ELFTLSInfoSectionName; }
41
42 bool visitEdge(LinkGraph &G, Block *B, Edge &E) {
45 dbgs() << " Fixing " << G.getEdgeKindName(E.getKind()) << " edge at "
46 << formatv("{0:x}", B->getFixupAddress(E)) << " ("
47 << formatv("{0:x}", B->getAddress()) << " + "
48 << formatv("{0:x}", E.getOffset()) << ")\n";
49 });
52 return true;
53 }
54 return false;
55 }
56
57 Symbol &createEntry(LinkGraph &G, Symbol &Target) {
58 // the TLS Info entry's key value will be written by the fixTLVSectionByName
59 // pass, so create mutable content.
60 auto &TLSInfoEntry = G.createMutableContentBlock(
61 getTLSInfoSection(G), G.allocateContent(getTLSInfoEntryContent()),
62 orc::ExecutorAddr(), 8, 0);
63 TLSInfoEntry.addEdge(x86_64::Pointer64, 8, Target, 0);
64 return G.addAnonymousSymbol(TLSInfoEntry, 0, 16, false, false);
65 }
66
67private:
68 Section &getTLSInfoSection(LinkGraph &G) {
69 if (!TLSInfoTable)
70 TLSInfoTable =
71 &G.createSection(ELFTLSInfoSectionName, orc::MemProt::Read);
72 return *TLSInfoTable;
73 }
74
75 ArrayRef<char> getTLSInfoEntryContent() const {
76 return {reinterpret_cast<const char *>(TLSInfoEntryContent),
77 sizeof(TLSInfoEntryContent)};
78 }
79
80 Section *TLSInfoTable = nullptr;
81};
82
83const uint8_t TLSInfoTableManager_ELF_x86_64::TLSInfoEntryContent[16] = {
84 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /*pthread key */
85 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 /*data address*/
86};
87
88Error buildTables_ELF_x86_64(LinkGraph &G) {
89 LLVM_DEBUG(dbgs() << "Visiting edges in graph:\n");
90
93 TLSInfoTableManager_ELF_x86_64 TLSInfo;
94 visitExistingEdges(G, GOT, PLT, TLSInfo);
95 return Error::success();
96}
97} // namespace
98
99namespace llvm {
100namespace jitlink {
101
102class ELFLinkGraphBuilder_x86_64 : public ELFLinkGraphBuilder<object::ELF64LE> {
103private:
104 using ELFT = object::ELF64LE;
105
106 Error addRelocations() override {
107 LLVM_DEBUG(dbgs() << "Processing relocations:\n");
108
110 using Self = ELFLinkGraphBuilder_x86_64;
111 for (const auto &RelSect : Base::Sections) {
112 // Validate the section to read relocation entries from.
113 if (RelSect.sh_type == ELF::SHT_REL)
114 return make_error<StringError>(
115 "No SHT_REL in valid x64 ELF object files",
117
118 if (Error Err = Base::forEachRelaRelocation(RelSect, this,
119 &Self::addSingleRelocation))
120 return Err;
121 }
122
123 return Error::success();
124 }
125
126 Error addSingleRelocation(const typename ELFT::Rela &Rel,
127 const typename ELFT::Shdr &FixupSection,
128 Block &BlockToFix) {
130
131 auto ELFReloc = Rel.getType(false);
132
133 // R_X86_64_NONE is a no-op.
134 if (LLVM_UNLIKELY(ELFReloc == ELF::R_X86_64_NONE))
135 return Error::success();
136
137 uint32_t SymbolIndex = Rel.getSymbol(false);
138 auto ObjSymbol = Base::Obj.getRelocationSymbol(Rel, Base::SymTabSec);
139 if (!ObjSymbol)
140 return ObjSymbol.takeError();
141
142 Symbol *GraphSymbol = Base::getGraphSymbol(SymbolIndex);
143 if (!GraphSymbol)
144 return make_error<StringError>(
145 formatv("Could not find symbol at given index, did you add it to "
146 "JITSymbolTable? index: {0}, shndx: {1} Size of table: {2}",
147 SymbolIndex, (*ObjSymbol)->st_shndx,
148 Base::GraphSymbols.size()),
150
151 // Validate the relocation kind.
152 int64_t Addend = Rel.r_addend;
154
155 switch (ELFReloc) {
156 case ELF::R_X86_64_PC32:
157 case ELF::R_X86_64_GOTPC32:
158 Kind = x86_64::Delta32;
159 break;
160 case ELF::R_X86_64_PC64:
161 case ELF::R_X86_64_GOTPC64:
162 Kind = x86_64::Delta64;
163 break;
164 case ELF::R_X86_64_32:
165 Kind = x86_64::Pointer32;
166 break;
167 case ELF::R_X86_64_16:
168 Kind = x86_64::Pointer16;
169 break;
170 case ELF::R_X86_64_8:
171 Kind = x86_64::Pointer8;
172 break;
173 case ELF::R_X86_64_32S:
175 break;
176 case ELF::R_X86_64_64:
177 Kind = x86_64::Pointer64;
178 break;
179 case ELF::R_X86_64_GOTPCREL:
181 break;
182 case ELF::R_X86_64_REX_GOTPCRELX:
184 Addend = 0;
185 break;
186 case ELF::R_X86_64_TLSGD:
188 break;
189 case ELF::R_X86_64_GOTPCRELX:
191 Addend = 0;
192 break;
193 case ELF::R_X86_64_GOTPCREL64:
195 break;
196 case ELF::R_X86_64_GOT64:
198 break;
199 case ELF::R_X86_64_GOTOFF64:
201 break;
202 case ELF::R_X86_64_PLT32:
204 // BranchPCRel32 implicitly handles the '-4' PC adjustment, so we have to
205 // adjust the addend by '+4' to compensate.
206 Addend += 4;
207 break;
208 default:
209 return make_error<JITLinkError>(
210 "In " + G->getName() + ": Unsupported x86-64 relocation type " +
212 }
213
214 auto FixupAddress = orc::ExecutorAddr(FixupSection.sh_addr) + Rel.r_offset;
215 Edge::OffsetT Offset = FixupAddress - BlockToFix.getAddress();
216 Edge GE(Kind, Offset, *GraphSymbol, Addend);
217 LLVM_DEBUG({
218 dbgs() << " ";
219 printEdge(dbgs(), BlockToFix, GE, x86_64::getEdgeKindName(Kind));
220 dbgs() << "\n";
221 });
222
223 BlockToFix.addEdge(std::move(GE));
224 return Error::success();
225 }
226
227public:
230 SubtargetFeatures Features)
231 : ELFLinkGraphBuilder(Obj, Triple("x86_64-unknown-linux"),
232 std::move(Features), FileName,
233 x86_64::getEdgeKindName) {}
234};
235
236class ELFJITLinker_x86_64 : public JITLinker<ELFJITLinker_x86_64> {
237 friend class JITLinker<ELFJITLinker_x86_64>;
238
239public:
240 ELFJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx,
241 std::unique_ptr<LinkGraph> G,
242 PassConfiguration PassConfig)
243 : JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {
244
245 if (shouldAddDefaultTargetPasses(getGraph().getTargetTriple()))
247 [this](LinkGraph &G) { return getOrCreateGOTSymbol(G); });
248 }
249
250private:
251 Symbol *GOTSymbol = nullptr;
252
253 Error getOrCreateGOTSymbol(LinkGraph &G) {
254 auto DefineExternalGOTSymbolIfPresent =
257 if (Sym.getName() == ELFGOTSymbolName)
258 if (auto *GOTSection = G.findSectionByName(
260 GOTSymbol = &Sym;
261 return {*GOTSection, true};
262 }
263 return {};
264 });
265
266 // Try to attach _GLOBAL_OFFSET_TABLE_ to the GOT if it's defined as an
267 // external.
268 if (auto Err = DefineExternalGOTSymbolIfPresent(G))
269 return Err;
270
271 // If we succeeded then we're done.
272 if (GOTSymbol)
273 return Error::success();
274
275 // Otherwise look for a GOT section: If it already has a start symbol we'll
276 // record it, otherwise we'll create our own.
277 // If there's a GOT section but we didn't find an external GOT symbol...
278 if (auto *GOTSection =
279 G.findSectionByName(x86_64::GOTTableManager::getSectionName())) {
280
281 // Check for an existing defined symbol.
282 for (auto *Sym : GOTSection->symbols())
283 if (Sym->getName() == ELFGOTSymbolName) {
284 GOTSymbol = Sym;
285 return Error::success();
286 }
287
288 // If there's no defined symbol then create one.
289 SectionRange SR(*GOTSection);
290 if (SR.empty())
291 GOTSymbol =
292 &G.addAbsoluteSymbol(ELFGOTSymbolName, orc::ExecutorAddr(), 0,
294 else
295 GOTSymbol =
296 &G.addDefinedSymbol(*SR.getFirstBlock(), 0, ELFGOTSymbolName, 0,
297 Linkage::Strong, Scope::Local, false, true);
298 }
299
300 // If we still haven't found a GOT symbol then double check the externals.
301 // We may have a GOT-relative reference but no GOT section, in which case
302 // we just need to point the GOT symbol at some address in this graph.
303 if (!GOTSymbol) {
304 for (auto *Sym : G.external_symbols()) {
305 if (Sym->getName() == ELFGOTSymbolName) {
306 auto Blocks = G.blocks();
307 if (!Blocks.empty()) {
308 G.makeAbsolute(*Sym, (*Blocks.begin())->getAddress());
309 GOTSymbol = Sym;
310 break;
311 }
312 }
313 }
314 }
315
316 return Error::success();
317 }
318
319 Error applyFixup(LinkGraph &G, Block &B, const Edge &E) const {
320 return x86_64::applyFixup(G, B, E, GOTSymbol);
321 }
322};
323
326 LLVM_DEBUG({
327 dbgs() << "Building jitlink graph for new input "
328 << ObjectBuffer.getBufferIdentifier() << "...\n";
329 });
330
331 auto ELFObj = object::ObjectFile::createELFObjectFile(ObjectBuffer);
332 if (!ELFObj)
333 return ELFObj.takeError();
334
335 auto Features = (*ELFObj)->getFeatures();
336 if (!Features)
337 return Features.takeError();
338
339 auto &ELFObjFile = cast<object::ELFObjectFile<object::ELF64LE>>(**ELFObj);
340 return ELFLinkGraphBuilder_x86_64((*ELFObj)->getFileName(),
341 ELFObjFile.getELFFile(),
342 std::move(*Features))
343 .buildGraph();
344}
345
346void link_ELF_x86_64(std::unique_ptr<LinkGraph> G,
347 std::unique_ptr<JITLinkContext> Ctx) {
349
350 if (Ctx->shouldAddDefaultTargetPasses(G->getTargetTriple())) {
351
352 Config.PrePrunePasses.push_back(DWARFRecordSectionSplitter(".eh_frame"));
353 Config.PrePrunePasses.push_back(EHFrameEdgeFixer(
356 Config.PrePrunePasses.push_back(EHFrameNullTerminator(".eh_frame"));
357
358 // Construct a JITLinker and run the link function.
359 // Add a mark-live pass.
360 if (auto MarkLive = Ctx->getMarkLivePass(G->getTargetTriple()))
361 Config.PrePrunePasses.push_back(std::move(MarkLive));
362 else
363 Config.PrePrunePasses.push_back(markAllSymbolsLive);
364
365 // Add an in-place GOT/Stubs/TLSInfoEntry build pass.
366 Config.PostPrunePasses.push_back(buildTables_ELF_x86_64);
367
368 // Resolve any external section start / end symbols.
369 Config.PostAllocationPasses.push_back(
372
373 // Add GOT/Stubs optimizer pass.
374 Config.PreFixupPasses.push_back(x86_64::optimizeGOTAndStubAccesses);
375 }
376
377 if (auto Err = Ctx->modifyPassConfig(*G, Config))
378 return Ctx->notifyFailed(std::move(Err));
379
380 ELFJITLinker_x86_64::link(std::move(Ctx), std::move(G), std::move(Config));
381}
382} // end namespace jitlink
383} // end namespace llvm
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
#define LLVM_UNLIKELY(EXPR)
Definition: Compiler.h:241
#define LLVM_DEBUG(X)
Definition: Debug.h:101
RelaxConfig Config
Definition: ELF_riscv.cpp:506
DenseMap< Block *, BlockRelaxAux > Blocks
Definition: ELF_riscv.cpp:507
Symbol * Sym
Definition: ELF_riscv.cpp:479
#define G(x, y, z)
Definition: MD5.cpp:56
if(VerifyEach)
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
Lightweight error class with error context and mandatory checking.
Definition: Error.h:160
static ErrorSuccess success()
Create a success value.
Definition: Error.h:334
Tagged union holding either a T or a Error.
Definition: Error.h:474
StringRef getBufferIdentifier() const
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
Manages the enabling and disabling of subtarget specific features.
Target - Wrapper for Target specific information.
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
static Expected< std::unique_ptr< ObjectFile > > createELFObjectFile(MemoryBufferRef Object, bool InitContent=true)
Represents an address in the executor process.
@ EM_X86_64
Definition: ELF.h:178
@ SHT_REL
Definition: ELF.h:1071
static constexpr const StringLiteral & getSectionName(DebugSectionKind SectionKind)
Return the name of the section.
ELFType< llvm::endianness::little, true > ELF64LE
Definition: ELFTypes.h:97
StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type)
Definition: ELF.cpp:23
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ Offset
Definition: DWP.cpp:456
auto formatv(const char *Fmt, Ts &&... Vals) -> formatv_object< decltype(std::make_tuple(detail::build_format_adapter(std::forward< Ts >(Vals))...))>
std::error_code inconvertibleErrorCode()
The value returned by this function can be returned from convertToErrorCode for Error values where no...
Definition: Error.cpp:90
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
OutputIt move(R &&Range, OutputIt Out)
Provide wrappers to std::move which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1858
Implement std::hash so that hash_code can be used in STL containers.
Definition: BitVector.h:858