llvm-6502/lib/CodeGen/ELFWriter.h
Bruno Cardoso Lopes e39493eb1b Use a default alignment for data and bss sections.
Only pad when the section size > 0 and move the code that deals
with globals initializers to a place we know for sure the global
is initialized.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73944 91177308-0d34-0410-b5e6-96231b3b80d8
2009-06-23 04:39:27 +00:00

220 lines
7.8 KiB
C++

//===-- ELFWriter.h - Target-independent ELF writer support -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the ELFWriter class.
//
//===----------------------------------------------------------------------===//
#ifndef ELFWRITER_H
#define ELFWRITER_H
#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetELFWriterInfo.h"
#include "ELF.h"
#include <list>
#include <map>
namespace llvm {
class BinaryObject;
class ConstantStruct;
class ELFCodeEmitter;
class GlobalVariable;
class Mangler;
class MachineCodeEmitter;
class raw_ostream;
/// ELFWriter - This class implements the common target-independent code for
/// writing ELF files. Targets should derive a class from this to
/// parameterize the output format.
///
class ELFWriter : public MachineFunctionPass {
friend class ELFCodeEmitter;
public:
static char ID;
MachineCodeEmitter &getMachineCodeEmitter() const {
return *(MachineCodeEmitter*)MCE;
}
ELFWriter(raw_ostream &O, TargetMachine &TM);
~ELFWriter();
typedef std::vector<unsigned char> DataBuffer;
protected:
/// Output stream to send the resultant object file to.
raw_ostream &O;
/// Target machine description.
TargetMachine &TM;
/// Target Elf Writer description.
const TargetELFWriterInfo *TEW;
/// Mang - The object used to perform name mangling for this module.
Mangler *Mang;
/// MCE - The MachineCodeEmitter object that we are exposing to emit machine
/// code for functions to the .o file.
ELFCodeEmitter *MCE;
/// TAI - Target Asm Info, provide information about section names for
/// globals and other target specific stuff.
const TargetAsmInfo *TAI;
//===------------------------------------------------------------------===//
// Properties inferred automatically from the target machine.
//===------------------------------------------------------------------===//
/// is64Bit/isLittleEndian - This information is inferred from the target
/// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
bool is64Bit, isLittleEndian;
/// doInitialization - Emit the file header and all of the global variables
/// for the module to the ELF file.
bool doInitialization(Module &M);
bool runOnMachineFunction(MachineFunction &MF);
/// doFinalization - Now that the module has been completely processed, emit
/// the ELF file to 'O'.
bool doFinalization(Module &M);
private:
/// Blob containing the Elf header
BinaryObject ElfHdr;
/// SectionList - This is the list of sections that we have emitted to the
/// file. Once the file has been completely built, the section header table
/// is constructed from this info.
std::list<ELFSection> SectionList;
unsigned NumSections; // Always = SectionList.size()
/// SectionLookup - This is a mapping from section name to section number in
/// the SectionList.
std::map<std::string, ELFSection*> SectionLookup;
/// GblSymLookup - This is a mapping from global value to a symbol index
/// in the symbol table. This is useful since relocations symbol references
/// must be quickly mapped to a symbol table index
std::map<const GlobalValue*, uint32_t> GblSymLookup;
/// SymbolList - This is the list of symbols emitted to the symbol table
/// Local symbols go to the front and Globals to the back.
std::list<ELFSym> SymbolList;
/// PendingGlobals - List of externally defined symbols that we have been
/// asked to emit, but have not seen a reference to. When a reference
/// is seen, the symbol will move from this list to the SymbolList.
SetVector<GlobalValue*> PendingGlobals;
/// getSection - Return the section with the specified name, creating a new
/// section if one does not already exist.
ELFSection &getSection(const std::string &Name, unsigned Type,
unsigned Flags = 0, unsigned Align = 0) {
ELFSection *&SN = SectionLookup[Name];
if (SN) return *SN;
// Remove tab from section name prefix. This is necessary becase TAI
// sometimes return a section name prefixed with a "\t" char.
std::string SectionName(Name);
size_t Pos = SectionName.find("\t");
if (Pos != std::string::npos)
SectionName.erase(Pos, 1);
SectionList.push_back(ELFSection(SectionName, isLittleEndian, is64Bit));
SN = &SectionList.back();
SN->SectionIdx = NumSections++;
SN->Type = Type;
SN->Flags = Flags;
SN->Link = ELFSection::SHN_UNDEF;
SN->Align = Align;
return *SN;
}
/// TODO: support mangled names here to emit the right .text section
/// for c++ object files.
ELFSection &getTextSection() {
return getSection(".text", ELFSection::SHT_PROGBITS,
ELFSection::SHF_EXECINSTR | ELFSection::SHF_ALLOC);
}
/// Return the relocation section of section 'S'. 'RelA' is true
/// if the relocation section contains entries with addends.
ELFSection &getRelocSection(std::string SName, bool RelA) {
std::string RelSName(".rel");
unsigned SHdrTy = RelA ? ELFSection::SHT_RELA : ELFSection::SHT_REL;
if (RelA) RelSName.append("a");
RelSName.append(SName);
return getSection(RelSName, SHdrTy, 0, TEW->getPrefELFAlignment());
}
ELFSection &getNonExecStackSection() {
return getSection(".note.GNU-stack", ELFSection::SHT_PROGBITS, 0, 1);
}
ELFSection &getSymbolTableSection() {
return getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
}
ELFSection &getStringTableSection() {
return getSection(".strtab", ELFSection::SHT_STRTAB, 0, 1);
}
ELFSection &getSectionHeaderStringTableSection() {
return getSection(".shstrtab", ELFSection::SHT_STRTAB, 0, 1);
}
ELFSection &getDataSection() {
return getSection(".data", ELFSection::SHT_PROGBITS,
ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
}
ELFSection &getBSSSection() {
return getSection(".bss", ELFSection::SHT_NOBITS,
ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 4);
}
ELFSection &getNullSection() {
return getSection("", ELFSection::SHT_NULL, 0);
}
// As we complete the ELF file, we need to update fields in the ELF header
// (e.g. the location of the section table). These members keep track of
// the offset in ELFHeader of these various pieces to update and other
// locations in the file.
unsigned ELFHdr_e_shoff_Offset; // e_shoff in ELF header.
unsigned ELFHdr_e_shstrndx_Offset; // e_shstrndx in ELF header.
unsigned ELFHdr_e_shnum_Offset; // e_shnum in ELF header.
private:
void EmitFunctionDeclaration(const Function *F);
void EmitGlobalVar(const GlobalVariable *GV);
void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
void EmitGlobalConstantStruct(const ConstantStruct *CVS,
ELFSection &GblS);
unsigned getGlobalELFLinkage(const GlobalVariable *GV);
ELFSection &getGlobalSymELFSection(const GlobalVariable *GV, ELFSym &Sym);
void EmitRelocations();
void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
void EmitSectionTableStringTable();
void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
void EmitSymbolTable();
void EmitStringTable();
void OutputSectionsAndSectionTable();
};
}
#endif