1 //===- MCSectionELF.h - ELF Machine Code Sections ---------------*- 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 declares the MCSectionELF class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_MC_MCSECTIONELF_H
15 #define LLVM_MC_MCSECTIONELF_H
17 #include "llvm/MC/MCSection.h"
21 /// MCSectionELF - This represents a section on linux, lots of unix variants
22 /// and some bare metal systems.
23 class MCSectionELF : public MCSection {
24 /// SectionName - This is the name of the section. The referenced memory is
25 /// owned by TargetLoweringObjectFileELF's ELFUniqueMap.
26 StringRef SectionName;
28 /// Type - This is the sh_type field of a section, drawn from the enums below.
31 /// Flags - This is the sh_flags field of a section, drawn from the enums.
35 /// IsExplicit - Indicates that this section comes from globals with an
36 /// explicit section specified.
40 MCSectionELF(StringRef Section, unsigned type, unsigned flags,
41 SectionKind K, bool isExplicit)
42 : MCSection(K), SectionName(Section), Type(type), Flags(flags),
43 IsExplicit(isExplicit) {}
46 static MCSectionELF *Create(StringRef Section, unsigned Type,
47 unsigned Flags, SectionKind K, bool isExplicit,
50 /// ShouldOmitSectionDirective - Decides whether a '.section' directive
51 /// should be printed before the section name
52 bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
54 /// ShouldPrintSectionType - Only prints the section type if supported
55 bool ShouldPrintSectionType(unsigned Ty) const;
57 /// HasCommonSymbols - True if this section holds common symbols, this is
58 /// indicated on the ELF object file by a symbol with SHN_COMMON section
60 bool HasCommonSymbols() const;
62 /// These are the section type and flags fields. An ELF section can have
63 /// only one Type, but can have more than one of the flags specified.
65 /// Valid section types.
67 // This value marks the section header as inactive.
70 // Holds information defined by the program, with custom format and meaning.
73 // This section holds a symbol table.
76 // The section holds a string table.
79 // The section holds relocation entries with explicit addends.
82 // The section holds a symbol hash table.
85 // Information for dynamic linking.
88 // The section holds information that marks the file in some way.
91 // A section of this type occupies no space in the file.
94 // The section holds relocation entries without explicit addends.
97 // This section type is reserved but has unspecified semantics.
100 // This section holds a symbol table.
103 // This section contains an array of pointers to initialization functions.
104 SHT_INIT_ARRAY = 0x0EU,
106 // This section contains an array of pointers to termination functions.
107 SHT_FINI_ARRAY = 0x0FU,
109 // This section contains an array of pointers to functions that are invoked
110 // before all other initialization functions.
111 SHT_PREINIT_ARRAY = 0x10U,
113 // A section group is a set of sections that are related and that must be
114 // treated specially by the linker.
117 // This section is associated with a section of type SHT_SYMTAB, when the
118 // referenced symbol table contain the escape value SHN_XINDEX
119 SHT_SYMTAB_SHNDX = 0x12U,
121 LAST_KNOWN_SECTION_TYPE = SHT_SYMTAB_SHNDX
124 /// Valid section flags.
126 // The section contains data that should be writable.
129 // The section occupies memory during execution.
132 // The section contains executable machine instructions.
133 SHF_EXECINSTR = 0x4U,
135 // The data in the section may be merged to eliminate duplication.
138 // Elements in the section consist of null-terminated character strings.
141 // A field in this section holds a section header table index.
142 SHF_INFO_LINK = 0x40U,
144 // Adds special ordering requirements for link editors.
145 SHF_LINK_ORDER = 0x80U,
147 // This section requires special OS-specific processing to avoid incorrect
149 SHF_OS_NONCONFORMING = 0x100U,
151 // This section is a member of a section group.
154 // This section holds Thread-Local Storage.
157 /// FIRST_TARGET_DEP_FLAG - This is the first flag that subclasses are
158 /// allowed to specify.
159 FIRST_TARGET_DEP_FLAG = 0x800U,
161 /// TARGET_INDEP_SHF - This is the bitmask for all the target independent
162 /// section flags. Targets can define their own target flags above these.
163 /// If they do that, they should implement their own MCSectionELF subclasses
164 /// and implement the virtual method hooks below to handle printing needs.
165 TARGET_INDEP_SHF = FIRST_TARGET_DEP_FLAG-1U
168 StringRef getSectionName() const { return SectionName; }
169 unsigned getType() const { return Type; }
170 unsigned getFlags() const { return Flags; }
172 virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
173 raw_ostream &OS) const;
176 /// PrintTargetSpecificSectionFlags - Targets that define their own
177 /// MCSectionELF subclasses with target specific section flags should
178 /// implement this method if they end up adding letters to the attributes
180 virtual void PrintTargetSpecificSectionFlags(const MCAsmInfo &MAI,
181 raw_ostream &OS) const {
187 } // end namespace llvm