MCSectionELF.h revision 33adcfb4d217f5f23d9bde8ba02b8e48f9605fc5
1//===- MCSectionELF.h - ELF Machine Code Sections ---------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file declares the MCSectionELF class. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_MC_MCSECTIONELF_H 15#define LLVM_MC_MCSECTIONELF_H 16 17#include "llvm/MC/MCSection.h" 18 19namespace llvm { 20 21/// MCSectionELF - This represents a section on linux, lots of unix variants 22/// and some bare metal systems. 23class MCSectionELF : public MCSection { 24 std::string SectionName; 25 26 /// Type - This is the sh_type field of a section, drawn from the enums below. 27 unsigned Type; 28 29 /// Flags - This is the sh_flags field of a section, drawn from the enums. 30 /// below. 31 unsigned Flags; 32 33 /// IsExplicit - Indicates that this section comes from globals with an 34 /// explicit section specfied. 35 bool IsExplicit; 36 37protected: 38 MCSectionELF(const StringRef &Section, unsigned type, unsigned flags, 39 SectionKind K, bool isExplicit) 40 : MCSection(K), SectionName(Section.str()), Type(type), Flags(flags), 41 IsExplicit(isExplicit) {} 42public: 43 44 static MCSectionELF *Create(const StringRef &Section, unsigned Type, 45 unsigned Flags, SectionKind K, bool isExplicit, 46 MCContext &Ctx); 47 48 /// ShouldOmitSectionDirective - Decides whether a '.section' directive 49 /// should be printed before the section name 50 bool ShouldOmitSectionDirective(const char *Name, 51 const MCAsmInfo &MAI) const; 52 53 /// ShouldPrintSectionType - Only prints the section type if supported 54 bool ShouldPrintSectionType(unsigned Ty) const; 55 56 /// HasCommonSymbols - True if this section holds common symbols, this is 57 /// indicated on the ELF object file by a symbol with SHN_COMMON section 58 /// header index. 59 bool HasCommonSymbols() const; 60 61 /// These are the section type and flags fields. An ELF section can have 62 /// only one Type, but can have more than one of the flags specified. 63 /// 64 /// Valid section types. 65 enum { 66 // This value marks the section header as inactive. 67 SHT_NULL = 0x00U, 68 69 // Holds information defined by the program, with custom format and meaning. 70 SHT_PROGBITS = 0x01U, 71 72 // This section holds a symbol table. 73 SHT_SYMTAB = 0x02U, 74 75 // The section holds a string table. 76 SHT_STRTAB = 0x03U, 77 78 // The section holds relocation entries with explicit addends. 79 SHT_RELA = 0x04U, 80 81 // The section holds a symbol hash table. 82 SHT_HASH = 0x05U, 83 84 // Information for dynamic linking. 85 SHT_DYNAMIC = 0x06U, 86 87 // The section holds information that marks the file in some way. 88 SHT_NOTE = 0x07U, 89 90 // A section of this type occupies no space in the file. 91 SHT_NOBITS = 0x08U, 92 93 // The section holds relocation entries without explicit addends. 94 SHT_REL = 0x09U, 95 96 // This section type is reserved but has unspecified semantics. 97 SHT_SHLIB = 0x0AU, 98 99 // This section holds a symbol table. 100 SHT_DYNSYM = 0x0BU, 101 102 // This section contains an array of pointers to initialization functions. 103 SHT_INIT_ARRAY = 0x0EU, 104 105 // This section contains an array of pointers to termination functions. 106 SHT_FINI_ARRAY = 0x0FU, 107 108 // This section contains an array of pointers to functions that are invoked 109 // before all other initialization functions. 110 SHT_PREINIT_ARRAY = 0x10U, 111 112 // A section group is a set of sections that are related and that must be 113 // treated specially by the linker. 114 SHT_GROUP = 0x11U, 115 116 // This section is associated with a section of type SHT_SYMTAB, when the 117 // referenced symbol table contain the escape value SHN_XINDEX 118 SHT_SYMTAB_SHNDX = 0x12U, 119 120 LAST_KNOWN_SECTION_TYPE = SHT_SYMTAB_SHNDX 121 }; 122 123 /// Valid section flags. 124 enum { 125 // The section contains data that should be writable. 126 SHF_WRITE = 0x1U, 127 128 // The section occupies memory during execution. 129 SHF_ALLOC = 0x2U, 130 131 // The section contains executable machine instructions. 132 SHF_EXECINSTR = 0x4U, 133 134 // The data in the section may be merged to eliminate duplication. 135 SHF_MERGE = 0x10U, 136 137 // Elements in the section consist of null-terminated character strings. 138 SHF_STRINGS = 0x20U, 139 140 // A field in this section holds a section header table index. 141 SHF_INFO_LINK = 0x40U, 142 143 // Adds special ordering requirements for link editors. 144 SHF_LINK_ORDER = 0x80U, 145 146 // This section requires special OS-specific processing to avoid incorrect 147 // behavior. 148 SHF_OS_NONCONFORMING = 0x100U, 149 150 // This section is a member of a section group. 151 SHF_GROUP = 0x200U, 152 153 // This section holds Thread-Local Storage. 154 SHF_TLS = 0x400U, 155 156 /// FIRST_TARGET_DEP_FLAG - This is the first flag that subclasses are 157 /// allowed to specify. 158 FIRST_TARGET_DEP_FLAG = 0x800U, 159 160 /// TARGET_INDEP_SHF - This is the bitmask for all the target independent 161 /// section flags. Targets can define their own target flags above these. 162 /// If they do that, they should implement their own MCSectionELF subclasses 163 /// and implement the virtual method hooks below to handle printing needs. 164 TARGET_INDEP_SHF = FIRST_TARGET_DEP_FLAG-1U 165 }; 166 167 StringRef getSectionName() const { 168 return StringRef(SectionName); 169 } 170 171 unsigned getType() const { return Type; } 172 unsigned getFlags() const { return Flags; } 173 174 virtual void PrintSwitchToSection(const MCAsmInfo &MAI, 175 raw_ostream &OS) const; 176 177 178 /// PrintTargetSpecificSectionFlags - Targets that define their own 179 /// MCSectionELF subclasses with target specific section flags should 180 /// implement this method if they end up adding letters to the attributes 181 /// list. 182 virtual void PrintTargetSpecificSectionFlags(const MCAsmInfo &MAI, 183 raw_ostream &OS) const { 184 } 185 186 187}; 188 189} // end namespace llvm 190 191#endif 192