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"
29 class MachineCodeEmitter;
31 class TargetELFWriterInfo;
37 /// ELFWriter - This class implements the common target-independent code for
38 /// writing ELF files. Targets should derive a class from this to
39 /// parameterize the output format.
41 class ELFWriter : public MachineFunctionPass {
42 friend class ELFCodeEmitter;
46 MachineCodeEmitter &getMachineCodeEmitter() const {
47 return *(MachineCodeEmitter*)MCE;
50 ELFWriter(raw_ostream &O, TargetMachine &TM);
53 typedef std::vector<unsigned char> DataBuffer;
56 /// Output stream to send the resultant object file to.
59 /// Target machine description.
62 /// Target Elf Writer description.
63 const TargetELFWriterInfo *TEW;
65 /// Mang - The object used to perform name mangling for this module.
68 /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
69 /// code for functions to the .o file.
72 /// TAI - Target Asm Info, provide information about section names for
73 /// globals and other target specific stuff.
74 const TargetAsmInfo *TAI;
76 //===------------------------------------------------------------------===//
77 // Properties inferred automatically from the target machine.
78 //===------------------------------------------------------------------===//
80 /// is64Bit/isLittleEndian - This information is inferred from the target
81 /// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
82 bool is64Bit, isLittleEndian;
84 /// doInitialization - Emit the file header and all of the global variables
85 /// for the module to the ELF file.
86 bool doInitialization(Module &M);
87 bool runOnMachineFunction(MachineFunction &MF);
89 /// doFinalization - Now that the module has been completely processed, emit
90 /// the ELF file to 'O'.
91 bool doFinalization(Module &M);
94 /// Blob containing the Elf header
97 /// SectionList - This is the list of sections that we have emitted to the
98 /// file. Once the file has been completely built, the section header table
99 /// is constructed from this info.
100 std::list<ELFSection> SectionList;
101 unsigned NumSections; // Always = SectionList.size()
103 /// SectionLookup - This is a mapping from section name to section number in
105 std::map<std::string, ELFSection*> SectionLookup;
107 /// GblSymLookup - This is a mapping from global value to a symbol index
108 /// in the symbol table. This is useful since relocations symbol references
109 /// must be quickly mapped to a symbol table index
110 std::map<const GlobalValue*, uint32_t> GblSymLookup;
112 /// SymbolList - This is the list of symbols emitted to the symbol table
113 /// Local symbols go to the front and Globals to the back.
114 std::list<ELFSym> SymbolList;
116 /// PendingGlobals - List of externally defined symbols that we have been
117 /// asked to emit, but have not seen a reference to. When a reference
118 /// is seen, the symbol will move from this list to the SymbolList.
119 SetVector<GlobalValue*> PendingGlobals;
121 /// getSection - Return the section with the specified name, creating a new
122 /// section if one does not already exist.
123 ELFSection &getSection(const std::string &Name, unsigned Type,
124 unsigned Flags = 0, unsigned Align = 0) {
125 ELFSection *&SN = SectionLookup[Name];
128 // Remove tab from section name prefix. This is necessary becase TAI
129 // sometimes return a section name prefixed with a "\t" char.
130 std::string SectionName(Name);
131 size_t Pos = SectionName.find("\t");
132 if (Pos != std::string::npos)
133 SectionName.erase(Pos, 1);
135 SectionList.push_back(ELFSection(SectionName, isLittleEndian, is64Bit));
136 SN = &SectionList.back();
137 SN->SectionIdx = NumSections++;
140 SN->Link = ELFSection::SHN_UNDEF;
145 /// TODO: support mangled names here to emit the right .text section
146 /// for c++ object files.
147 ELFSection &getTextSection() {
148 return getSection(".text", ELFSection::SHT_PROGBITS,
149 ELFSection::SHF_EXECINSTR | ELFSection::SHF_ALLOC);
152 /// Get a constant pool section based on the section name returned by TAI
153 ELFSection &getConstantPoolSection(std::string SName, unsigned Align) {
154 return getSection(SName, ELFSection::SHT_PROGBITS,
155 ELFSection::SHF_MERGE | ELFSection::SHF_ALLOC, Align);
158 /// Return the relocation section of section 'S'. 'RelA' is true
159 /// if the relocation section contains entries with addends.
160 ELFSection &getRelocSection(std::string SName, bool RelA, unsigned Align) {
161 std::string RelSName(".rel");
162 unsigned SHdrTy = RelA ? ELFSection::SHT_RELA : ELFSection::SHT_REL;
164 if (RelA) RelSName.append("a");
165 RelSName.append(SName);
167 return getSection(RelSName, SHdrTy, 0, Align);
170 ELFSection &getNonExecStackSection() {
171 return getSection(".note.GNU-stack", ELFSection::SHT_PROGBITS, 0, 1);
174 ELFSection &getSymbolTableSection() {
175 return getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
178 ELFSection &getStringTableSection() {
179 return getSection(".strtab", ELFSection::SHT_STRTAB, 0, 1);
182 ELFSection &getSectionHeaderStringTableSection() {
183 return getSection(".shstrtab", ELFSection::SHT_STRTAB, 0, 1);
186 ELFSection &getDataSection() {
187 return getSection(".data", ELFSection::SHT_PROGBITS,
188 ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
191 ELFSection &getBSSSection() {
192 return getSection(".bss", ELFSection::SHT_NOBITS,
193 ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
196 ELFSection &getNullSection() {
197 return getSection("", ELFSection::SHT_NULL, 0);
200 // Helpers for obtaining ELF specific Linkage and Visibility info.
201 unsigned getGlobalELFLinkage(const GlobalValue *GV);
202 unsigned getGlobalELFVisibility(const GlobalValue *GV);
204 // As we complete the ELF file, we need to update fields in the ELF header
205 // (e.g. the location of the section table). These members keep track of
206 // the offset in ELFHeader of these various pieces to update and other
207 // locations in the file.
208 unsigned ELFHdr_e_shoff_Offset; // e_shoff in ELF header.
209 unsigned ELFHdr_e_shstrndx_Offset; // e_shstrndx in ELF header.
210 unsigned ELFHdr_e_shnum_Offset; // e_shnum in ELF header.
213 void EmitFunctionDeclaration(const Function *F);
214 void EmitGlobalVar(const GlobalVariable *GV);
215 void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
216 void EmitGlobalConstantStruct(const ConstantStruct *CVS,
218 ELFSection &getGlobalSymELFSection(const GlobalVariable *GV, ELFSym &Sym);
219 void EmitRelocations();
220 void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
221 void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
222 void EmitSectionTableStringTable();
223 void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
224 void EmitSymbolTable();
225 void EmitStringTable();
226 void OutputSectionsAndSectionTable();