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"
23 /// MCSectionELF - This represents a section on linux, lots of unix variants
24 /// and some bare metal systems.
25 class MCSectionELF : public MCSection {
26 /// SectionName - This is the name of the section. The referenced memory is
27 /// owned by TargetLoweringObjectFileELF's ELFUniqueMap.
28 StringRef SectionName;
30 /// Type - This is the sh_type field of a section, drawn from the enums below.
33 /// Flags - This is the sh_flags field of a section, drawn from the enums.
37 /// EntrySize - The size of each entry in this section. This size only
38 /// makes sense for sections that contain fixed-sized entries. If a
39 /// section does not contain fixed-sized entries 'EntrySize' will be 0.
42 const MCSymbol *Group;
45 friend class MCContext;
46 MCSectionELF(StringRef Section, unsigned type, unsigned flags,
47 SectionKind K, unsigned entrySize, const MCSymbol *group)
48 : MCSection(SV_ELF, K), SectionName(Section), Type(type), Flags(flags),
49 EntrySize(entrySize), Group(group) {}
53 /// ShouldOmitSectionDirective - Decides whether a '.section' directive
54 /// should be printed before the section name
55 bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) 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 // Start of target-specific flags.
123 // Exception Index table
124 SHT_ARM_EXIDX = 0x70000001U,
125 // BPABI DLL dynamic linking pre-emption map
126 SHT_ARM_PREEMPTMAP = 0x70000002U,
127 // Object file compatibility attributes
128 SHT_ARM_ATTRIBUTES = 0x70000003U,
129 SHT_ARM_DEBUGOVERLAY = 0x70000004U,
130 SHT_ARM_OVERLAYSECTION = 0x70000005U,
132 LAST_KNOWN_SECTION_TYPE = SHT_ARM_OVERLAYSECTION
135 /// Valid section flags.
137 // The section contains data that should be writable.
140 // The section occupies memory during execution.
143 // The section contains executable machine instructions.
144 SHF_EXECINSTR = 0x4U,
146 // The data in the section may be merged to eliminate duplication.
149 // Elements in the section consist of null-terminated character strings.
152 // A field in this section holds a section header table index.
153 SHF_INFO_LINK = 0x40U,
155 // Adds special ordering requirements for link editors.
156 SHF_LINK_ORDER = 0x80U,
158 // This section requires special OS-specific processing to avoid incorrect
160 SHF_OS_NONCONFORMING = 0x100U,
162 // This section is a member of a section group.
165 // This section holds Thread-Local Storage.
169 // Start of target-specific flags.
171 /// XCORE_SHF_CP_SECTION - All sections with the "c" flag are grouped
172 /// together by the linker to form the constant pool and the cp register is
173 /// set to the start of the constant pool by the boot code.
174 XCORE_SHF_CP_SECTION = 0x800U,
176 /// XCORE_SHF_DP_SECTION - All sections with the "d" flag are grouped
177 /// together by the linker to form the data section and the dp register is
178 /// set to the start of the section by the boot code.
179 XCORE_SHF_DP_SECTION = 0x1000U
182 StringRef getSectionName() const { return SectionName; }
183 unsigned getType() const { return Type; }
184 unsigned getFlags() const { return Flags; }
185 unsigned getEntrySize() const { return EntrySize; }
186 const MCSymbol *getGroup() const { return Group; }
188 void PrintSwitchToSection(const MCAsmInfo &MAI,
189 raw_ostream &OS) const;
190 virtual bool UseCodeAlign() const;
191 virtual bool isVirtualSection() const;
193 /// isBaseAddressKnownZero - We know that non-allocatable sections (like
194 /// debug info) have a base of zero.
195 virtual bool isBaseAddressKnownZero() const {
196 return (getFlags() & SHF_ALLOC) == 0;
199 static bool classof(const MCSection *S) {
200 return S->getVariant() == SV_ELF;
202 static bool classof(const MCSectionELF *) { return true; }
204 // Return the entry size for sections with fixed-width data.
205 static unsigned DetermineEntrySize(SectionKind Kind);
209 } // end namespace llvm