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//===- MCSectionELF.h - ELF Machine Code Sections ---------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the MCSectionELF class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCSECTIONELF_H
#define LLVM_MC_MCSECTIONELF_H
#include "llvm/MC/MCSection.h"
namespace llvm {
class MCSymbol;
/// MCSectionELF - This represents a section on linux, lots of unix variants
/// and some bare metal systems.
class MCSectionELF : public MCSection {
/// SectionName - This is the name of the section. The referenced memory is
/// owned by TargetLoweringObjectFileELF's ELFUniqueMap.
StringRef SectionName;
/// Type - This is the sh_type field of a section, drawn from the enums below.
unsigned Type;
/// Flags - This is the sh_flags field of a section, drawn from the enums.
/// below.
unsigned Flags;
/// EntrySize - The size of each entry in this section. This size only
/// makes sense for sections that contain fixed-sized entries. If a
/// section does not contain fixed-sized entries 'EntrySize' will be 0.
unsigned EntrySize;
const MCSymbol *Group;
private:
friend class MCContext;
MCSectionELF(StringRef Section, unsigned type, unsigned flags,
SectionKind K, unsigned entrySize, const MCSymbol *group)
: MCSection(SV_ELF, K), SectionName(Section), Type(type), Flags(flags),
EntrySize(entrySize), Group(group) {}
~MCSectionELF();
public:
/// ShouldOmitSectionDirective - Decides whether a '.section' directive
/// should be printed before the section name
bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
/// HasCommonSymbols - True if this section holds common symbols, this is
/// indicated on the ELF object file by a symbol with SHN_COMMON section
/// header index.
bool HasCommonSymbols() const;
/// These are the section type and flags fields. An ELF section can have
/// only one Type, but can have more than one of the flags specified.
///
/// Valid section types.
enum {
// This value marks the section header as inactive.
SHT_NULL = 0x00U,
// Holds information defined by the program, with custom format and meaning.
SHT_PROGBITS = 0x01U,
// This section holds a symbol table.
SHT_SYMTAB = 0x02U,
// The section holds a string table.
SHT_STRTAB = 0x03U,
// The section holds relocation entries with explicit addends.
SHT_RELA = 0x04U,
// The section holds a symbol hash table.
SHT_HASH = 0x05U,
// Information for dynamic linking.
SHT_DYNAMIC = 0x06U,
// The section holds information that marks the file in some way.
SHT_NOTE = 0x07U,
// A section of this type occupies no space in the file.
SHT_NOBITS = 0x08U,
// The section holds relocation entries without explicit addends.
SHT_REL = 0x09U,
// This section type is reserved but has unspecified semantics.
SHT_SHLIB = 0x0AU,
// This section holds a symbol table.
SHT_DYNSYM = 0x0BU,
// This section contains an array of pointers to initialization functions.
SHT_INIT_ARRAY = 0x0EU,
// This section contains an array of pointers to termination functions.
SHT_FINI_ARRAY = 0x0FU,
// This section contains an array of pointers to functions that are invoked
// before all other initialization functions.
SHT_PREINIT_ARRAY = 0x10U,
// A section group is a set of sections that are related and that must be
// treated specially by the linker.
SHT_GROUP = 0x11U,
// This section is associated with a section of type SHT_SYMTAB, when the
// referenced symbol table contain the escape value SHN_XINDEX
SHT_SYMTAB_SHNDX = 0x12U,
// Start of target-specific flags.
// Exception Index table
SHT_ARM_EXIDX = 0x70000001U,
// BPABI DLL dynamic linking pre-emption map
SHT_ARM_PREEMPTMAP = 0x70000002U,
// Object file compatibility attributes
SHT_ARM_ATTRIBUTES = 0x70000003U,
SHT_ARM_DEBUGOVERLAY = 0x70000004U,
SHT_ARM_OVERLAYSECTION = 0x70000005U,
LAST_KNOWN_SECTION_TYPE = SHT_ARM_OVERLAYSECTION
};
/// Valid section flags.
enum {
// The section contains data that should be writable.
SHF_WRITE = 0x1U,
// The section occupies memory during execution.
SHF_ALLOC = 0x2U,
// The section contains executable machine instructions.
SHF_EXECINSTR = 0x4U,
// The data in the section may be merged to eliminate duplication.
SHF_MERGE = 0x10U,
// Elements in the section consist of null-terminated character strings.
SHF_STRINGS = 0x20U,
// A field in this section holds a section header table index.
SHF_INFO_LINK = 0x40U,
// Adds special ordering requirements for link editors.
SHF_LINK_ORDER = 0x80U,
// This section requires special OS-specific processing to avoid incorrect
// behavior.
SHF_OS_NONCONFORMING = 0x100U,
// This section is a member of a section group.
SHF_GROUP = 0x200U,
// This section holds Thread-Local Storage.
SHF_TLS = 0x400U,
// Start of target-specific flags.
/// XCORE_SHF_CP_SECTION - All sections with the "c" flag are grouped
/// together by the linker to form the constant pool and the cp register is
/// set to the start of the constant pool by the boot code.
XCORE_SHF_CP_SECTION = 0x800U,
/// XCORE_SHF_DP_SECTION - All sections with the "d" flag are grouped
/// together by the linker to form the data section and the dp register is
/// set to the start of the section by the boot code.
XCORE_SHF_DP_SECTION = 0x1000U
};
StringRef getSectionName() const { return SectionName; }
unsigned getType() const { return Type; }
unsigned getFlags() const { return Flags; }
unsigned getEntrySize() const { return EntrySize; }
const MCSymbol *getGroup() const { return Group; }
void PrintSwitchToSection(const MCAsmInfo &MAI,
raw_ostream &OS) const;
virtual bool UseCodeAlign() const;
virtual bool isVirtualSection() const;
/// isBaseAddressKnownZero - We know that non-allocatable sections (like
/// debug info) have a base of zero.
virtual bool isBaseAddressKnownZero() const {
return (getFlags() & SHF_ALLOC) == 0;
}
static bool classof(const MCSection *S) {
return S->getVariant() == SV_ELF;
}
static bool classof(const MCSectionELF *) { return true; }
// Return the entry size for sections with fixed-width data.
static unsigned DetermineEntrySize(SectionKind Kind);
};
} // end namespace llvm
#endif
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