1 //===- lib/ReaderWriter/ELF/ExecutableWriter.h ----------------------------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
9 #ifndef LLD_READER_WRITER_ELF_EXECUTABLE_WRITER_H
10 #define LLD_READER_WRITER_ELF_EXECUTABLE_WRITER_H
12 #include "OutputELFWriter.h"
17 using namespace llvm::object;
20 class ExecutableWriter;
22 //===----------------------------------------------------------------------===//
23 // ExecutableWriter Class
24 //===----------------------------------------------------------------------===//
26 class ExecutableWriter : public OutputELFWriter<ELFT> {
28 ExecutableWriter(ELFLinkingContext &context, TargetLayout<ELFT> &layout)
29 : OutputELFWriter<ELFT>(context, layout),
30 _runtimeFile(new RuntimeFile<ELFT>(context, "C runtime")) {}
33 virtual void buildDynamicSymbolTable(const File &file);
34 virtual void addDefaultAtoms();
35 virtual bool createImplicitFiles(std::vector<std::unique_ptr<File> > &);
36 virtual void finalizeDefaultAtomValues();
37 virtual void createDefaultSections();
39 virtual bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
40 return this->_layout.isCopied(sla);
43 unique_bump_ptr<InterpSection<ELFT>> _interpSection;
44 std::unique_ptr<RuntimeFile<ELFT> > _runtimeFile;
47 //===----------------------------------------------------------------------===//
49 //===----------------------------------------------------------------------===//
51 void ExecutableWriter<ELFT>::buildDynamicSymbolTable(const File &file) {
52 for (auto sec : this->_layout.sections())
53 if (auto section = dyn_cast<AtomSection<ELFT>>(sec))
54 for (const auto &atom : section->atoms()) {
55 const DefinedAtom *da = dyn_cast<const DefinedAtom>(atom->_atom);
58 if (da->dynamicExport() != DefinedAtom::dynamicExportAlways &&
59 !this->_context.isDynamicallyExportedSymbol(da->name()) &&
60 !(this->_context.shouldExportDynamic() &&
61 da->scope() == Atom::Scope::scopeGlobal))
63 this->_dynamicSymbolTable->addSymbol(atom->_atom, section->ordinal(),
64 atom->_virtualAddr, atom);
67 // Put weak symbols in the dynamic symbol table.
68 if (this->_context.isDynamic()) {
69 for (const UndefinedAtom *a : file.undefined()) {
70 if (this->_layout.isReferencedByDefinedAtom(a) &&
71 a->canBeNull() != UndefinedAtom::canBeNullNever)
72 this->_dynamicSymbolTable->addSymbol(a, ELF::SHN_UNDEF);
76 OutputELFWriter<ELFT>::buildDynamicSymbolTable(file);
79 /// \brief Add absolute symbols by default. These are linker added
82 void ExecutableWriter<ELFT>::addDefaultAtoms() {
83 OutputELFWriter<ELFT>::addDefaultAtoms();
84 _runtimeFile->addUndefinedAtom(this->_context.entrySymbolName());
85 _runtimeFile->addAbsoluteAtom("__bss_start");
86 _runtimeFile->addAbsoluteAtom("__bss_end");
87 _runtimeFile->addAbsoluteAtom("_end");
88 _runtimeFile->addAbsoluteAtom("end");
89 _runtimeFile->addAbsoluteAtom("__preinit_array_start");
90 _runtimeFile->addAbsoluteAtom("__preinit_array_end");
91 _runtimeFile->addAbsoluteAtom("__init_array_start");
92 _runtimeFile->addAbsoluteAtom("__init_array_end");
93 if (this->_context.isRelaOutputFormat()) {
94 _runtimeFile->addAbsoluteAtom("__rela_iplt_start");
95 _runtimeFile->addAbsoluteAtom("__rela_iplt_end");
97 _runtimeFile->addAbsoluteAtom("__rel_iplt_start");
98 _runtimeFile->addAbsoluteAtom("__rel_iplt_end");
100 _runtimeFile->addAbsoluteAtom("__fini_array_start");
101 _runtimeFile->addAbsoluteAtom("__fini_array_end");
104 /// \brief Hook in lld to add CRuntime file
105 template <class ELFT>
106 bool ExecutableWriter<ELFT>::createImplicitFiles(
107 std::vector<std::unique_ptr<File> > &result) {
108 // Add the default atoms as defined by executables
109 ExecutableWriter<ELFT>::addDefaultAtoms();
110 OutputELFWriter<ELFT>::createImplicitFiles(result);
111 result.push_back(std::move(_runtimeFile));
115 template <class ELFT> void ExecutableWriter<ELFT>::createDefaultSections() {
116 OutputELFWriter<ELFT>::createDefaultSections();
117 if (this->_context.isDynamic()) {
118 _interpSection.reset(new (this->_alloc) InterpSection<ELFT>(
119 this->_context, ".interp", DefaultLayout<ELFT>::ORDER_INTERP,
120 this->_context.getInterpreter()));
121 this->_layout.addSection(_interpSection.get());
125 /// Finalize the value of all the absolute symbols that we
127 template <class ELFT> void ExecutableWriter<ELFT>::finalizeDefaultAtomValues() {
128 OutputELFWriter<ELFT>::finalizeDefaultAtomValues();
129 auto bssStartAtomIter = this->_layout.findAbsoluteAtom("__bss_start");
130 auto bssEndAtomIter = this->_layout.findAbsoluteAtom("__bss_end");
131 auto underScoreEndAtomIter = this->_layout.findAbsoluteAtom("_end");
132 auto endAtomIter = this->_layout.findAbsoluteAtom("end");
134 auto startEnd = [&](StringRef sym, StringRef sec) -> void {
135 std::string start = ("__" + sym + "_start").str();
136 std::string end = ("__" + sym + "_end").str();
137 auto s = this->_layout.findAbsoluteAtom(start);
138 auto e = this->_layout.findAbsoluteAtom(end);
139 auto section = this->_layout.findOutputSection(sec);
141 (*s)->_virtualAddr = section->virtualAddr();
142 (*e)->_virtualAddr = section->virtualAddr() + section->memSize();
144 (*s)->_virtualAddr = 0;
145 (*e)->_virtualAddr = 0;
149 startEnd("preinit_array", ".preinit_array");
150 startEnd("init_array", ".init_array");
151 if (this->_context.isRelaOutputFormat())
152 startEnd("rela_iplt", ".rela.plt");
154 startEnd("rel_iplt", ".rel.plt");
155 startEnd("fini_array", ".fini_array");
157 assert(!(bssStartAtomIter == this->_layout.absoluteAtoms().end() ||
158 bssEndAtomIter == this->_layout.absoluteAtoms().end() ||
159 underScoreEndAtomIter == this->_layout.absoluteAtoms().end() ||
160 endAtomIter == this->_layout.absoluteAtoms().end()) &&
161 "Unable to find the absolute atoms that have been added by lld");
163 auto bssSection = this->_layout.findOutputSection(".bss");
165 // If we don't find a bss section, then don't set these values
167 (*bssStartAtomIter)->_virtualAddr = bssSection->virtualAddr();
168 (*bssEndAtomIter)->_virtualAddr =
169 bssSection->virtualAddr() + bssSection->memSize();
170 (*underScoreEndAtomIter)->_virtualAddr = (*bssEndAtomIter)->_virtualAddr;
171 (*endAtomIter)->_virtualAddr = (*bssEndAtomIter)->_virtualAddr;
172 } else if (auto dataSection = this->_layout.findOutputSection(".data")) {
173 (*underScoreEndAtomIter)->_virtualAddr =
174 dataSection->virtualAddr() + dataSection->memSize();
175 (*endAtomIter)->_virtualAddr = (*underScoreEndAtomIter)->_virtualAddr;
182 #endif // LLD_READER_WRITER_ELF_EXECUTABLE_WRITER_H