1 //===-- lib/CodeGen/ELF.h - ELF constants and data structures ---*- 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 header contains common, non-processor-specific data structures and
11 // constants for the ELF file format.
13 // The details of the ELF32 bits in this file are largely based on the Tool
14 // Interface Standard (TIS) Executable and Linking Format (ELF) Specification
15 // Version 1.2, May 1995. The ELF64 is based on HP/Intel definition of the
16 // ELF-64 object file format document, Version 1.5 Draft 2 May 27, 1998
18 //===----------------------------------------------------------------------===//
23 #include "llvm/CodeGen/BinaryObject.h"
24 #include "llvm/CodeGen/MachineRelocation.h"
25 #include "llvm/Support/DataTypes.h"
30 // Identification Indexes
40 ET_NONE = 0, // No file type
41 ET_REL = 1, // Relocatable file
42 ET_EXEC = 2, // Executable file
43 ET_DYN = 3, // Shared object file
44 ET_CORE = 4, // Core file
45 ET_LOPROC = 0xff00, // Beginning of processor-specific codes
46 ET_HIPROC = 0xffff // Processor-specific
55 /// ELFSym - This struct contains information about each symbol that is
56 /// added to logical symbol table for the module. This is eventually
57 /// turned into a real symbol table in the file.
59 // The global value this symbol matches. This should be null if the symbol
60 // is not a global value.
61 const GlobalValue *GV;
63 // ELF specific fields
64 unsigned NameIdx; // Index in .strtab of name, once emitted.
69 unsigned short SectionIdx;
71 // Symbol index into the Symbol table
75 STB_LOCAL = 0, // Local sym, not visible outside obj file containing def
76 STB_GLOBAL = 1, // Global sym, visible to all object files being combined
77 STB_WEAK = 2 // Weak symbol, like global but lower-precedence
81 STT_NOTYPE = 0, // Symbol's type is not specified
82 STT_OBJECT = 1, // Symbol is a data object (variable, array, etc.)
83 STT_FUNC = 2, // Symbol is executable code (function, etc.)
84 STT_SECTION = 3, // Symbol refers to a section
85 STT_FILE = 4 // Local, absolute symbol that refers to a file
89 STV_DEFAULT = 0, // Visibility is specified by binding type
90 STV_INTERNAL = 1, // Defined by processor supplements
91 STV_HIDDEN = 2, // Not visible to other components
92 STV_PROTECTED = 3 // Visible in other components but not preemptable
95 ELFSym(const GlobalValue *gv) : GV(gv), NameIdx(0), Value(0),
96 Size(0), Info(0), Other(STV_DEFAULT),
97 SectionIdx(0), SymTabIdx(0) {}
99 unsigned getBind() const { return (Info >> 4) & 0xf; }
100 unsigned getType() const { return Info & 0xf; }
101 bool isLocalBind() const { return getBind() == STB_LOCAL; }
103 void setBind(unsigned X) {
104 assert(X == (X & 0xF) && "Bind value out of range!");
105 Info = (Info & 0x0F) | (X << 4);
108 void setType(unsigned X) {
109 assert(X == (X & 0xF) && "Type value out of range!");
110 Info = (Info & 0xF0) | X;
113 void setVisibility(unsigned V) {
114 assert(V == (V & 0x3) && "Visibility value out of range!");
119 /// ELFSection - This struct contains information about each section that is
120 /// emitted to the file. This is eventually turned into the section header
121 /// table at the end of the file.
122 class ELFSection : public BinaryObject {
124 // ELF specific fields
125 unsigned NameIdx; // sh_name - .shstrtab idx of name, once emitted.
126 unsigned Type; // sh_type - Section contents & semantics
127 unsigned Flags; // sh_flags - Section flags.
128 uint64_t Addr; // sh_addr - The mem addr this section is in.
129 unsigned Offset; // sh_offset - Offset from the file start
130 unsigned Size; // sh_size - The section size.
131 unsigned Link; // sh_link - Section header table index link.
132 unsigned Info; // sh_info - Auxillary information.
133 unsigned Align; // sh_addralign - Alignment of section.
134 unsigned EntSize; // sh_entsize - Size of entries in the section e
136 // Section Header Flags
138 SHF_WRITE = 1 << 0, // Writable
139 SHF_ALLOC = 1 << 1, // Mapped into the process addr space
140 SHF_EXECINSTR = 1 << 2, // Executable
141 SHF_MERGE = 1 << 4, // Might be merged if equal
142 SHF_STRINGS = 1 << 5, // Contains null-terminated strings
143 SHF_INFO_LINK = 1 << 6, // 'sh_info' contains SHT index
144 SHF_LINK_ORDER = 1 << 7, // Preserve order after combining
145 SHF_OS_NONCONFORMING = 1 << 8, // nonstandard OS support required
146 SHF_GROUP = 1 << 9, // Section is a member of a group
147 SHF_TLS = 1 << 10 // Section holds thread-local data
152 SHT_NULL = 0, // No associated section (inactive entry).
153 SHT_PROGBITS = 1, // Program-defined contents.
154 SHT_SYMTAB = 2, // Symbol table.
155 SHT_STRTAB = 3, // String table.
156 SHT_RELA = 4, // Relocation entries; explicit addends.
157 SHT_HASH = 5, // Symbol hash table.
158 SHT_DYNAMIC = 6, // Information for dynamic linking.
159 SHT_NOTE = 7, // Information about the file.
160 SHT_NOBITS = 8, // Data occupies no space in the file.
161 SHT_REL = 9, // Relocation entries; no explicit addends.
162 SHT_SHLIB = 10, // Reserved.
163 SHT_DYNSYM = 11, // Symbol table.
164 SHT_LOPROC = 0x70000000, // Lowest processor arch-specific type.
165 SHT_HIPROC = 0x7fffffff, // Highest processor arch-specific type.
166 SHT_LOUSER = 0x80000000, // Lowest type reserved for applications.
167 SHT_HIUSER = 0xffffffff // Highest type reserved for applications.
170 // Special section indices.
172 SHN_UNDEF = 0, // Undefined, missing, irrelevant
173 SHN_LORESERVE = 0xff00, // Lowest reserved index
174 SHN_LOPROC = 0xff00, // Lowest processor-specific index
175 SHN_HIPROC = 0xff1f, // Highest processor-specific index
176 SHN_ABS = 0xfff1, // Symbol has absolute value; no relocation
177 SHN_COMMON = 0xfff2, // FORTRAN COMMON or C external global variables
178 SHN_HIRESERVE = 0xffff // Highest reserved index
181 /// SectionIdx - The number of the section in the Section Table.
182 unsigned short SectionIdx;
184 /// Sym - The symbol to represent this section if it has one.
187 /// getSymIndex - Returns the symbol table index of the symbol
188 /// representing this section.
189 unsigned getSymbolTableIndex() const {
190 assert(Sym && "section not present in the symbol table");
191 return Sym->SymTabIdx;
194 ELFSection(const std::string &name, bool isLittleEndian, bool is64Bit)
195 : BinaryObject(name, isLittleEndian, is64Bit), Type(0), Flags(0), Addr(0),
196 Offset(0), Size(0), Link(0), Info(0), Align(0), EntSize(0), Sym(0) {}
199 /// ELFRelocation - This class contains all the information necessary to
200 /// to generate any 32-bit or 64-bit ELF relocation entry.
201 class ELFRelocation {
202 uint64_t r_offset; // offset in the section of the object this applies to
203 uint32_t r_symidx; // symbol table index of the symbol to use
204 uint32_t r_type; // machine specific relocation type
205 int64_t r_add; // explicit relocation addend
206 bool r_rela; // if true then the addend is part of the entry
207 // otherwise the addend is at the location specified
210 uint64_t getInfo(bool is64Bit) const {
212 return ((uint64_t)r_symidx << 32) + ((uint64_t)r_type & 0xFFFFFFFFL);
214 return (r_symidx << 8) + (r_type & 0xFFL);
217 uint64_t getOffset() const { return r_offset; }
218 int64_t getAddend() const { return r_add; }
220 ELFRelocation(uint64_t off, uint32_t sym, uint32_t type,
221 bool rela = true, int64_t addend = 0) :
222 r_offset(off), r_symidx(sym), r_type(type),
223 r_add(addend), r_rela(rela) {}
226 } // end namespace llvm