1 //===-- ELFWriter.h - Target-independent ELF writer support -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the ELFWriter class.
12 //===----------------------------------------------------------------------===//
17 #include "llvm/ADT/SetVector.h"
18 #include "llvm/CodeGen/MachineFunctionPass.h"
31 class MachineCodeEmitter;
32 class MachineConstantPoolEntry;
33 class ObjectCodeEmitter;
35 class TargetELFWriterInfo;
40 typedef std::vector<ELFSym*>::iterator ELFSymIter;
41 typedef std::vector<ELFSection*>::iterator ELFSectionIter;
42 typedef SetVector<const GlobalValue*>::const_iterator PendingGblsIter;
43 typedef SetVector<const char *>::const_iterator PendingExtsIter;
45 /// ELFWriter - This class implements the common target-independent code for
46 /// writing ELF files. Targets should derive a class from this to
47 /// parameterize the output format.
49 class ELFWriter : public MachineFunctionPass {
50 friend class ELFCodeEmitter;
54 /// Return the ELFCodeEmitter as an instance of ObjectCodeEmitter
55 ObjectCodeEmitter *getObjectCodeEmitter() {
56 return reinterpret_cast<ObjectCodeEmitter*>(ElfCE);
59 ELFWriter(raw_ostream &O, TargetMachine &TM);
63 /// Output stream to send the resultant object file to.
66 /// Target machine description.
69 MCContext &OutContext;
71 /// Target Elf Writer description.
72 const TargetELFWriterInfo *TEW;
74 /// Mang - The object used to perform name mangling for this module.
77 /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
78 /// code for functions to the .o file.
79 ELFCodeEmitter *ElfCE;
81 /// TAI - Target Asm Info, provide information about section names for
82 /// globals and other target specific stuff.
83 const TargetAsmInfo *TAI;
85 //===------------------------------------------------------------------===//
86 // Properties inferred automatically from the target machine.
87 //===------------------------------------------------------------------===//
89 /// is64Bit/isLittleEndian - This information is inferred from the target
90 /// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
91 bool is64Bit, isLittleEndian;
93 /// doInitialization - Emit the file header and all of the global variables
94 /// for the module to the ELF file.
95 bool doInitialization(Module &M);
96 bool runOnMachineFunction(MachineFunction &MF);
98 /// doFinalization - Now that the module has been completely processed, emit
99 /// the ELF file to 'O'.
100 bool doFinalization(Module &M);
103 /// Blob containing the Elf header
106 /// SectionList - This is the list of sections that we have emitted to the
107 /// file. Once the file has been completely built, the section header table
108 /// is constructed from this info.
109 std::vector<ELFSection*> SectionList;
110 unsigned NumSections; // Always = SectionList.size()
112 /// SectionLookup - This is a mapping from section name to section number in
113 /// the SectionList. Used to quickly gather the Section Index from TAI names
114 std::map<std::string, ELFSection*> SectionLookup;
116 /// PendingGlobals - Globals not processed as symbols yet.
117 SetVector<const GlobalValue*> PendingGlobals;
119 /// GblSymLookup - This is a mapping from global value to a symbol index
120 /// in the symbol table or private symbols list. This is useful since reloc
121 /// symbol references must be quickly mapped to their indices on the lists.
122 std::map<const GlobalValue*, uint32_t> GblSymLookup;
124 /// PendingExternals - Externals not processed as symbols yet.
125 SetVector<const char *> PendingExternals;
127 /// ExtSymLookup - This is a mapping from externals to a symbol index
128 /// in the symbol table list. This is useful since reloc symbol references
129 /// must be quickly mapped to their symbol table indices.
130 std::map<const char *, uint32_t> ExtSymLookup;
132 /// SymbolList - This is the list of symbols emitted to the symbol table.
133 /// When the SymbolList is finally built, local symbols must be placed in
134 /// the beginning while non-locals at the end.
135 std::vector<ELFSym*> SymbolList;
137 /// PrivateSyms - Record private symbols, every symbol here must never be
138 /// present in the SymbolList.
139 std::vector<ELFSym*> PrivateSyms;
141 // Remove tab from section name prefix. This is necessary becase TAI
142 // sometimes return a section name prefixed with elf unused chars. This is
143 // a little bit dirty. FIXME: find a better approach, maybe add more
144 // methods to TAI to get the clean name?
145 void fixNameForSection(std::string &Name) {
146 size_t Pos = Name.find("\t");
147 if (Pos != std::string::npos)
150 Pos = Name.find(".section ");
151 if (Pos != std::string::npos)
154 Pos = Name.find("\n");
155 if (Pos != std::string::npos)
159 /// getSection - Return the section with the specified name, creating a new
160 /// section if one does not already exist.
161 ELFSection &getSection(const std::string &Name, unsigned Type,
162 unsigned Flags = 0, unsigned Align = 0) {
163 std::string SName(Name);
164 fixNameForSection(SName);
166 ELFSection *&SN = SectionLookup[SName];
169 SectionList.push_back(new ELFSection(SName, isLittleEndian, is64Bit));
170 SN = SectionList.back();
171 SN->SectionIdx = NumSections++;
174 SN->Link = ELFSection::SHN_UNDEF;
179 /// TODO: support mangled names here to emit the right .text section
180 /// for c++ object files.
181 ELFSection &getTextSection() {
182 return getSection(".text", ELFSection::SHT_PROGBITS,
183 ELFSection::SHF_EXECINSTR | ELFSection::SHF_ALLOC);
186 ELFSection &getNonExecStackSection() {
187 return getSection(".note.GNU-stack", ELFSection::SHT_PROGBITS, 0, 1);
190 ELFSection &getSymbolTableSection() {
191 return getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
194 ELFSection &getStringTableSection() {
195 return getSection(".strtab", ELFSection::SHT_STRTAB, 0, 1);
198 ELFSection &getSectionHeaderStringTableSection() {
199 return getSection(".shstrtab", ELFSection::SHT_STRTAB, 0, 1);
202 ELFSection &getDataSection() {
203 return getSection(".data", ELFSection::SHT_PROGBITS,
204 ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
207 ELFSection &getBSSSection() {
208 return getSection(".bss", ELFSection::SHT_NOBITS,
209 ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
212 ELFSection &getNullSection() {
213 return getSection("", ELFSection::SHT_NULL, 0);
216 ELFSection &getJumpTableSection();
217 ELFSection &getConstantPoolSection(MachineConstantPoolEntry &CPE);
218 ELFSection &getRelocSection(ELFSection &S);
220 // Helpers for obtaining ELF specific info.
221 unsigned getGlobalELFBinding(const GlobalValue *GV);
222 unsigned getGlobalELFType(const GlobalValue *GV);
223 unsigned getGlobalELFVisibility(const GlobalValue *GV);
224 unsigned getElfSectionFlags(SectionKind Kind);
226 // addGlobalSymbol - Add a global to be processed and to the
227 // global symbol lookup, use a zero index for non private symbols
228 // because the table index will be determined later.
229 void addGlobalSymbol(const GlobalValue *GV);
231 // addExternalSymbol - Add the external to be processed and to the
232 // external symbol lookup, use a zero index because the symbol
233 // table index will be determined later
234 void addExternalSymbol(const char *External);
236 // As we complete the ELF file, we need to update fields in the ELF header
237 // (e.g. the location of the section table). These members keep track of
238 // the offset in ELFHeader of these various pieces to update and other
239 // locations in the file.
240 unsigned ELFHdr_e_shoff_Offset; // e_shoff in ELF header.
241 unsigned ELFHdr_e_shstrndx_Offset; // e_shstrndx in ELF header.
242 unsigned ELFHdr_e_shnum_Offset; // e_shnum in ELF header.
245 void EmitGlobal(const GlobalValue *GV);
246 void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
247 void EmitGlobalConstantStruct(const ConstantStruct *CVS,
249 ELFSection &getGlobalSymELFSection(const GlobalVariable *GV, ELFSym &Sym);
250 void EmitRelocations();
251 void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
252 void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
253 void EmitSectionTableStringTable();
254 void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
255 void EmitSymbolTable();
256 void EmitStringTable(const std::string &ModuleName);
257 void OutputSectionsAndSectionTable();
258 void RelocateField(BinaryObject &BO, uint32_t Offset, int64_t Value,
260 unsigned SortSymbols();