MCSectionELF.h revision fdf229eda95a542fc34d5182e1a91a22789ba122 
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
37  MCSectionELF(const StringRef &Section, unsigned T, unsigned F,
38               SectionKind K, bool isExplicit)
39    : MCSection(K), SectionName(Section.str()), Type(T), Flags(F),
40      IsExplicit(isExplicit) {}
41public:
42
43  static MCSectionELF *Create(const StringRef &Section, unsigned Type,
44                              unsigned Flags, SectionKind K, bool isExplicit,
45                              MCContext &Ctx);
46
47  /// ShouldOmitSectionDirective - Decides whether a '.section' directive
48  /// should be printed before the section name
49  bool ShouldOmitSectionDirective(const char *Name,
50                                  const TargetAsmInfo &TAI) const;
51
52  /// ShouldPrintSectionType - Only prints the section type if supported
53  bool ShouldPrintSectionType(unsigned Ty) const;
54
55  /// IsCommon - True if this section contains only common symbols
56  bool IsCommon() const;
57
58  /// These are the section type and flags fields.  An ELF section can have
59  /// only one Type, but can have more than one of the flags specified.
60  ///
61  /// Valid section types.
62  enum {
63    // This value marks the section header as inactive.
64    SHT_NULL             = 0x00U,
65
66    // Holds information defined by the program, with custom format and meaning.
67    SHT_PROGBITS         = 0x01U,
68
69    // This section holds a symbol table.
70    SHT_SYMTAB           = 0x02U,
71
72    // The section holds a string table.
73    SHT_STRTAB           = 0x03U,
74
75    // The section holds relocation entries with explicit addends.
76    SHT_RELA             = 0x04U,
77
78    // The section holds a symbol hash table.
79    SHT_HASH             = 0x05U,
80
81    // Information for dynamic linking.
82    SHT_DYNAMIC          = 0x06U,
83
84    // The section holds information that marks the file in some way.
85    SHT_NOTE             = 0x07U,
86
87    // A section of this type occupies no space in the file.
88    SHT_NOBITS           = 0x08U,
89
90    // The section holds relocation entries without explicit addends.
91    SHT_REL              = 0x09U,
92
93    // This section type is reserved but has unspecified semantics.
94    SHT_SHLIB            = 0x0aU,
95
96    // This section holds a symbol table.
97    SHT_DYNSYM           = 0x0bU,
98
99    // This section contains an array of pointers to initialization functions.
100    SHT_INIT_ARRAY       = 0x0eU,
101
102    // This section contains an array of pointers to termination functions.
103    SHT_FINI_ARRAY       = 0x0fU,
104
105    // This section contains an array of pointers to functions that are invoked
106    // before all other initialization functions.
107    SHT_PREINIT_ARRAY    = 0x10U,
108
109    // A section group is a set of sections that are related and that must be
110    // treated specially by the linker.
111    SHT_GROUP            = 0x11U,
112
113    // This section is associated with a section of type SHT_SYMTAB, when the
114    // referenced symbol table contain the escape value SHN_XINDEX
115    SHT_SYMTAB_SHNDX     = 0x12U,
116
117    LAST_KNOWN_SECTION_TYPE = SHT_SYMTAB_SHNDX
118  };
119
120  /// Valid section flags.
121  enum {
122    // The section contains data that should be writable.
123    SHF_WRITE            = 0x1U,
124
125    // The section occupies memory during execution.
126    SHF_ALLOC            = 0x2U,
127
128    // The section contains executable machine instructions.
129    SHF_EXECINSTR        = 0x4U,
130
131    // The data in the section may be merged to eliminate duplication.
132    SHF_MERGE            = 0x10U,
133
134    // Elements in the section consist of null-terminated character strings.
135    SHF_STRINGS          = 0x20U,
136
137    // A field in this section holds a section header table index.
138    SHF_INFO_LINK        = 0x40U,
139
140    // Adds special ordering requirements for link editors.
141    SHF_LINK_ORDER       = 0x80U,
142
143    // This section requires special OS-specific processing to avoid incorrect
144    // behavior.
145    SHF_OS_NONCONFORMING = 0x100U,
146
147    // This section is a member of a section group.
148    SHF_GROUP            = 0x200U,
149
150    // This section holds Thread-Local Storage.
151    SHF_TLS              = 0x400U
152  };
153
154  StringRef getSectionName() const {
155    return StringRef(SectionName);
156  }
157
158  unsigned getType() const { return Type; }
159  unsigned getFlags() const { return Flags; }
160
161  virtual void PrintSwitchToSection(const TargetAsmInfo &TAI,
162                                    raw_ostream &OS) const;
163};
164
165} // end namespace llvm
166
167#endif
168