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;
38 typedef std::vector<ELFSym*>::iterator ELFSymIter;
39 typedef std::vector<ELFSection*>::iterator ELFSectionIter;
41 /// ELFWriter - This class implements the common target-independent code for
42 /// writing ELF files. Targets should derive a class from this to
43 /// parameterize the output format.
45 class ELFWriter : public MachineFunctionPass {
46 friend class ELFCodeEmitter;
50 /// Return the ELFCodeEmitter as an instance of ObjectCodeEmitter
51 ObjectCodeEmitter *getObjectCodeEmitter() {
52 return reinterpret_cast<ObjectCodeEmitter*>(ElfCE);
55 ELFWriter(raw_ostream &O, TargetMachine &TM);
59 /// Output stream to send the resultant object file to.
62 /// Target machine description.
65 /// Target Elf Writer description.
66 const TargetELFWriterInfo *TEW;
68 /// Mang - The object used to perform name mangling for this module.
71 /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
72 /// code for functions to the .o file.
73 ELFCodeEmitter *ElfCE;
75 /// TAI - Target Asm Info, provide information about section names for
76 /// globals and other target specific stuff.
77 const TargetAsmInfo *TAI;
79 //===------------------------------------------------------------------===//
80 // Properties inferred automatically from the target machine.
81 //===------------------------------------------------------------------===//
83 /// is64Bit/isLittleEndian - This information is inferred from the target
84 /// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
85 bool is64Bit, isLittleEndian;
87 /// doInitialization - Emit the file header and all of the global variables
88 /// for the module to the ELF file.
89 bool doInitialization(Module &M);
90 bool runOnMachineFunction(MachineFunction &MF);
92 /// doFinalization - Now that the module has been completely processed, emit
93 /// the ELF file to 'O'.
94 bool doFinalization(Module &M);
97 /// Blob containing the Elf header
100 /// SectionList - This is the list of sections that we have emitted to the
101 /// file. Once the file has been completely built, the section header table
102 /// is constructed from this info.
103 std::vector<ELFSection*> SectionList;
104 unsigned NumSections; // Always = SectionList.size()
106 /// SectionLookup - This is a mapping from section name to section number in
107 /// the SectionList. Used to quickly gather the Section Index from TAI names
108 std::map<std::string, ELFSection*> SectionLookup;
110 /// GblSymLookup - This is a mapping from global value to a symbol index
111 /// in the symbol table or private symbols list. This is useful since reloc
112 /// symbol references must be quickly mapped to their indices on the lists
113 std::map<const GlobalValue*, uint32_t> GblSymLookup;
115 /// SymbolList - This is the list of symbols emitted to the symbol table.
116 /// When the SymbolList is finally built, local symbols must be placed in
117 /// the beginning while non-locals at the end.
118 std::vector<ELFSym*> SymbolList;
120 /// PrivateSyms - Record private symbols, every symbol here must never be
121 /// present in the SymbolList.
122 std::vector<ELFSym*> PrivateSyms;
124 /// PendingGlobals - List of externally defined symbols that we have been
125 /// asked to emit, but have not seen a reference to. When a reference
126 /// is seen, the symbol will move from this list to the SymbolList.
127 SetVector<GlobalValue*> PendingGlobals;
129 // Remove tab from section name prefix. This is necessary becase TAI
130 // sometimes return a section name prefixed with elf unused chars. This is
131 // a little bit dirty. FIXME: find a better approach, maybe add more
132 // methods to TAI to get the clean name?
133 void fixNameForSection(std::string &Name) {
134 size_t Pos = Name.find("\t");
135 if (Pos != std::string::npos)
138 Pos = Name.find(".section ");
139 if (Pos != std::string::npos)
142 Pos = Name.find("\n");
143 if (Pos != std::string::npos)
147 /// getSection - Return the section with the specified name, creating a new
148 /// section if one does not already exist.
149 ELFSection &getSection(const std::string &Name, unsigned Type,
150 unsigned Flags = 0, unsigned Align = 0) {
151 std::string SName(Name);
152 fixNameForSection(SName);
154 ELFSection *&SN = SectionLookup[SName];
157 SectionList.push_back(new ELFSection(SName, isLittleEndian, is64Bit));
158 SN = SectionList.back();
159 SN->SectionIdx = NumSections++;
162 SN->Link = ELFSection::SHN_UNDEF;
167 /// TODO: support mangled names here to emit the right .text section
168 /// for c++ object files.
169 ELFSection &getTextSection() {
170 return getSection(".text", ELFSection::SHT_PROGBITS,
171 ELFSection::SHF_EXECINSTR | ELFSection::SHF_ALLOC);
174 /// Return the relocation section of section 'S'. 'RelA' is true
175 /// if the relocation section contains entries with addends.
176 ELFSection &getRelocSection(std::string SName, bool RelA, unsigned Align) {
177 std::string RelSName(".rel");
178 unsigned SHdrTy = RelA ? ELFSection::SHT_RELA : ELFSection::SHT_REL;
180 if (RelA) RelSName.append("a");
181 RelSName.append(SName);
183 return getSection(RelSName, SHdrTy, 0, Align);
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);
219 // Helpers for obtaining ELF specific info.
220 unsigned getGlobalELFBinding(const GlobalValue *GV);
221 unsigned getGlobalELFType(const GlobalValue *GV);
222 unsigned getGlobalELFVisibility(const GlobalValue *GV);
223 unsigned getElfSectionFlags(unsigned Flags);
225 // As we complete the ELF file, we need to update fields in the ELF header
226 // (e.g. the location of the section table). These members keep track of
227 // the offset in ELFHeader of these various pieces to update and other
228 // locations in the file.
229 unsigned ELFHdr_e_shoff_Offset; // e_shoff in ELF header.
230 unsigned ELFHdr_e_shstrndx_Offset; // e_shstrndx in ELF header.
231 unsigned ELFHdr_e_shnum_Offset; // e_shnum in ELF header.
234 void EmitGlobal(const GlobalValue *GV);
235 void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
236 void EmitGlobalConstantStruct(const ConstantStruct *CVS,
238 ELFSection &getGlobalSymELFSection(const GlobalVariable *GV, ELFSym &Sym);
239 void EmitRelocations();
240 void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
241 void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
242 void EmitSectionTableStringTable();
243 void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
244 void EmitSymbolTable();
245 void EmitStringTable();
246 void OutputSectionsAndSectionTable();
247 unsigned SortSymbols();