1 //===-- ELFWriter.h - Target-independent ELF writer support -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the ELFWriter class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_ELFWRITER_H
15 #define LLVM_CODEGEN_ELFWRITER_H
17 #include "llvm/CodeGen/MachineFunctionPass.h"
22 class MachineCodeEmitter;
25 /// ELFWriter - This class implements the common target-independent code for
26 /// writing ELF files. Targets should derive a class from this to
27 /// parameterize the output format.
29 class ELFWriter : public MachineFunctionPass {
30 friend class ELFCodeEmitter;
32 MachineCodeEmitter &getMachineCodeEmitter() const {
33 return *(MachineCodeEmitter*)MCE;
39 ELFWriter(std::ostream &O, TargetMachine &TM);
41 /// Output stream to send the resultant object file to.
45 /// Target machine description.
49 /// Mang - The object used to perform name mangling for this module.
53 /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
54 /// code for functions to the .o file.
57 //===------------------------------------------------------------------===//
58 // Properties to be set by the derived class ctor, used to configure the
61 // e_machine - This field is the target specific value to emit as the
62 // e_machine member of the ELF header.
63 unsigned short e_machine;
65 // e_flags - The machine flags for the target. This defaults to zero.
68 //===------------------------------------------------------------------===//
69 // Properties inferred automatically from the target machine.
72 /// is64Bit/isLittleEndian - This information is inferred from the target
73 /// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
74 bool is64Bit, isLittleEndian;
76 /// doInitialization - Emit the file header and all of the global variables
77 /// for the module to the ELF file.
78 bool doInitialization(Module &M);
80 bool runOnMachineFunction(MachineFunction &MF);
83 /// doFinalization - Now that the module has been completely processed, emit
84 /// the ELF file to 'O'.
85 bool doFinalization(Module &M);
88 // The buffer we are accumulating the file into. Note that this should be
89 // changed into something much more efficient later (and the bytecode writer
91 std::vector<unsigned char> OutputBuffer;
93 /// ELFSection - This struct contains information about each section that is
94 /// emitted to the OutputBuffer. This is eventually turned into the section
95 /// header table at the end of the file.
97 std::string Name; // Name of the section.
98 unsigned NameIdx; // Index in .shstrtab of name, once emitted.
109 enum { SHT_NULL = 0, SHT_PROGBITS = 1, SHT_SYMTAB = 2, SHT_STRTAB = 3,
110 SHT_RELA = 4, SHT_HASH = 5, SHT_DYNAMIC = 6, SHT_NOTE = 7,
111 SHT_NOBITS = 8, SHT_REL = 9, SHT_SHLIB = 10, SHT_DYNSYM = 11 };
112 enum { SHN_UNDEF = 0, SHN_ABS = 0xFFF1, SHN_COMMON = 0xFFF2 };
113 enum { // SHF - ELF Section Header Flags
114 SHF_WRITE = 1 << 0, // Writable
115 SHF_ALLOC = 1 << 1, // Mapped into the process addr space
116 SHF_EXECINSTR = 1 << 2, // Executable
117 SHF_MERGE = 1 << 4, // Might be merged if equal
118 SHF_STRINGS = 1 << 5, // Contains null-terminated strings
119 SHF_INFO_LINK = 1 << 6, // 'sh_info' contains SHT index
120 SHF_LINK_ORDER = 1 << 7, // Preserve order after combining
121 SHF_OS_NONCONFORMING = 1 << 8, // nonstandard OS support required
122 SHF_GROUP = 1 << 9, // Section is a member of a group
123 SHF_TLS = 1 << 10,// Section holds thread-local data
126 ELFSection(const char *name = "", unsigned offset = 0)
127 : Name(name), Type(0), Flags(0), Addr(0), Offset(offset), Size(0),
128 Link(0), Info(0), Align(0), EntSize(0) {
132 /// SectionList - This is the list of sections that we have emitted to the
133 /// file. Once the file has been completely built, the section header table
134 /// is constructed from this info.
135 std::vector<ELFSection> SectionList;
137 /// ELFSym - This struct contains information about each symbol that is
138 /// added to logical symbol table for the module. This is eventually
139 /// turned into a real symbol table in the file.
141 const GlobalValue *GV; // The global value this corresponds to.
142 unsigned NameIdx; // Index in .strtab of name, once emitted.
147 unsigned short SectionIdx;
149 enum { STB_LOCAL = 0, STB_GLOBAL = 1, STB_WEAK = 2 };
150 enum { STT_NOTYPE = 0, STT_OBJECT = 1, STT_FUNC = 2, STT_SECTION = 3,
152 ELFSym(const GlobalValue *gv) : GV(gv), Value(0), Size(0), Info(0),
153 Other(0), SectionIdx(0) {}
155 void SetBind(unsigned X) {
156 assert(X == (X & 0xF) && "Bind value out of range!");
157 Info = (Info & 0x0F) | (X << 4);
159 void SetType(unsigned X) {
160 assert(X == (X & 0xF) && "Type value out of range!");
161 Info = (Info & 0xF0) | X;
165 /// SymbolTable - This is the list of symbols we have emitted to the file.
166 /// This actually gets rearranged before emission to OutputBuffer (to put
167 /// the local symbols first in the list).
168 std::vector<ELFSym> SymbolTable;
170 // As we accumulate the ELF file into OutputBuffer, we occasionally need to
171 // keep track of locations to update later (e.g. the location of the section
172 // table in the ELF header. These members keep track of the offset in
173 // OffsetBuffer of these various pieces to update and other locations in the
175 unsigned ELFHeader_e_shoff_Offset; // e_shoff in ELF header.
176 unsigned ELFHeader_e_shstrndx_Offset; // e_shstrndx in ELF header.
177 unsigned ELFHeader_e_shnum_Offset; // e_shnum in ELF header.
179 // align - Emit padding into the file until the current output position is
180 // aligned to the specified power of two boundary.
181 void align(unsigned Boundary) {
182 assert(Boundary && (Boundary & (Boundary-1)) == 0 &&
183 "Must align to 2^k boundary");
184 while (OutputBuffer.size() & (Boundary-1))
188 void outbyte(unsigned char X) { OutputBuffer.push_back(X); }
189 void outhalf(unsigned short X) {
190 if (isLittleEndian) {
191 OutputBuffer.push_back(X&255);
192 OutputBuffer.push_back(X >> 8);
194 OutputBuffer.push_back(X >> 8);
195 OutputBuffer.push_back(X&255);
198 void outword(unsigned X) {
199 if (isLittleEndian) {
200 OutputBuffer.push_back((X >> 0) & 255);
201 OutputBuffer.push_back((X >> 8) & 255);
202 OutputBuffer.push_back((X >> 16) & 255);
203 OutputBuffer.push_back((X >> 24) & 255);
205 OutputBuffer.push_back((X >> 24) & 255);
206 OutputBuffer.push_back((X >> 16) & 255);
207 OutputBuffer.push_back((X >> 8) & 255);
208 OutputBuffer.push_back((X >> 0) & 255);
211 void outaddr(uint64_t X) {
213 outword((unsigned)X);
215 assert(0 && "Emission of 64-bit data not implemented yet!");
218 // fix functions - Replace an existing entry at an offset.
219 void fixhalf(unsigned short X, unsigned Offset) {
220 unsigned char *P = &OutputBuffer[Offset];
221 P[0] = (X >> (isLittleEndian ? 0 : 8)) & 255;
222 P[1] = (X >> (isLittleEndian ? 8 : 0)) & 255;
225 void fixword(unsigned X, unsigned Offset) {
226 unsigned char *P = &OutputBuffer[Offset];
227 P[0] = (X >> (isLittleEndian ? 0 : 24)) & 255;
228 P[1] = (X >> (isLittleEndian ? 8 : 16)) & 255;
229 P[2] = (X >> (isLittleEndian ? 16 : 8)) & 255;
230 P[3] = (X >> (isLittleEndian ? 24 : 0)) & 255;
233 void fixaddr(uint64_t X, unsigned Offset) {
235 fixword((unsigned)X, Offset);
237 assert(0 && "Emission of 64-bit data not implemented yet!");
241 void EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
242 ELFSection &BSSSection);
244 void EmitSymbolTable();
246 void EmitSectionTableStringTable();
247 void EmitSectionTable();