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//===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This file implements the target-independent ELF writer. This file writes out
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// the ELF file in the following order:
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// #2. '.text' section
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// #3. '.data' section
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// #4. '.bss' section (conceptual position in file)
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// #X. '.shstrtab' section
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// The entries in the section table are laid out as:
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// #0. Null entry [required]
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// #1. ".text" entry - the program code
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// #2. ".data" entry - global variables with initializers. [ if needed ]
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// #3. ".bss" entry - global variables without initializers. [ if needed ]
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// #N. ".shstrtab" entry - String table for the section names.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "elfwriter"
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#include "ELFWriter.h"
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#include "ELFCodeEmitter.h"
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#include "llvm/Constants.h"
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#include "llvm/Module.h"
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#include "llvm/PassManager.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/CodeGen/BinaryObject.h"
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#include "llvm/CodeGen/MachineCodeEmitter.h"
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#include "llvm/CodeGen/ObjectCodeEmitter.h"
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#include "llvm/CodeGen/MachineCodeEmitter.h"
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#include "llvm/CodeGen/MachineConstantPool.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/Target/Mangler.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetELFWriterInfo.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetLoweringObjectFile.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/SmallString.h"
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char ELFWriter::ID = 0;
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//===----------------------------------------------------------------------===//
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// ELFWriter Implementation
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//===----------------------------------------------------------------------===//
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ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
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: MachineFunctionPass(ID), O(o), TM(tm),
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OutContext(*new MCContext(*TM.getMCAsmInfo())),
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TLOF(TM.getTargetLowering()->getObjFileLowering()),
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is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
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isLittleEndian(TM.getTargetData()->isLittleEndian()),
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ElfHdr(isLittleEndian, is64Bit) {
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MAI = TM.getMCAsmInfo();
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TEW = TM.getELFWriterInfo();
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// Create the object code emitter object for this target.
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ElfCE = new ELFCodeEmitter(*this);
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// Inital number of sections
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ELFWriter::~ELFWriter() {
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while(!SymbolList.empty()) {
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delete SymbolList.back();
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SymbolList.pop_back();
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while(!PrivateSyms.empty()) {
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delete PrivateSyms.back();
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PrivateSyms.pop_back();
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while(!SectionList.empty()) {
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delete SectionList.back();
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SectionList.pop_back();
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// Release the name mangler object.
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delete Mang; Mang = 0;
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// doInitialization - Emit the file header and all of the global variables for
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// the module to the ELF file.
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bool ELFWriter::doInitialization(Module &M) {
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// Initialize TargetLoweringObjectFile.
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const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
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Mang = new Mangler(OutContext, *TM.getTargetData());
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// Fields e_shnum e_shstrndx are only known after all section have
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// been emitted. They locations in the ouput buffer are recorded so
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// to be patched up later.
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// emitWord method behaves differently for ELF32 and ELF64, writing
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// 4 bytes in the former and 8 in the last for *_off and *_addr elf types
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ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
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ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
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ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
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ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
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ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
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ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
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ElfHdr.emitByte(ELF::EV_CURRENT); // e_ident[EI_VERSION]
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ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
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ElfHdr.emitWord16(ELF::ET_REL); // e_type
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ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
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ElfHdr.emitWord32(ELF::EV_CURRENT); // e_version
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ElfHdr.emitWord(0); // e_entry, no entry point in .o file
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ElfHdr.emitWord(0); // e_phoff, no program header for .o
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ELFHdr_e_shoff_Offset = ElfHdr.size();
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ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
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ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
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ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
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ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
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ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
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// e_shentsize = Section header entry size
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ElfHdr.emitWord16(TEW->getSHdrSize());
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// e_shnum = # of section header ents
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ELFHdr_e_shnum_Offset = ElfHdr.size();
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ElfHdr.emitWord16(0); // Placeholder
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// e_shstrndx = Section # of '.shstrtab'
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ELFHdr_e_shstrndx_Offset = ElfHdr.size();
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ElfHdr.emitWord16(0); // Placeholder
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// Add the null section, which is required to be first in the file.
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// The first entry in the symtab is the null symbol and the second
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// is a local symbol containing the module/file name
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SymbolList.push_back(new ELFSym());
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SymbolList.push_back(ELFSym::getFileSym());
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// AddPendingGlobalSymbol - Add a global to be processed and to
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// the global symbol lookup, use a zero index because the table
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// index will be determined later.
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void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
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bool AddToLookup /* = false */) {
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PendingGlobals.insert(GV);
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GblSymLookup[GV] = 0;
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// AddPendingExternalSymbol - Add the external to be processed
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// and to the external symbol lookup, use a zero index because
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// the symbol table index will be determined later.
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void ELFWriter::AddPendingExternalSymbol(const char *External) {
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PendingExternals.insert(External);
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ExtSymLookup[External] = 0;
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ELFSection &ELFWriter::getDataSection() {
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const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
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return getSection(Data->getSectionName(), Data->getType(),
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Data->getFlags(), 4);
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ELFSection &ELFWriter::getBSSSection() {
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const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
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return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
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// getCtorSection - Get the static constructor section
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ELFSection &ELFWriter::getCtorSection() {
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const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
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return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
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// getDtorSection - Get the static destructor section
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ELFSection &ELFWriter::getDtorSection() {
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const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
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return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
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// getTextSection - Get the text section for the specified function
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ELFSection &ELFWriter::getTextSection(const Function *F) {
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const MCSectionELF *Text =
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(const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
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return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
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// getJumpTableSection - Get a read only section for constants when
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// emitting jump tables. TODO: add PIC support
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ELFSection &ELFWriter::getJumpTableSection() {
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const MCSectionELF *JT =
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(const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
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return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
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TM.getTargetData()->getPointerABIAlignment());
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// getConstantPoolSection - Get a constant pool section based on the machine
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// constant pool entry type and relocation info.
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ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
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switch (CPE.getRelocationInfo()) {
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default: llvm_unreachable("Unknown section kind");
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case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
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Kind = SectionKind::getReadOnlyWithRelLocal();
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switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
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case 4: Kind = SectionKind::getMergeableConst4(); break;
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case 8: Kind = SectionKind::getMergeableConst8(); break;
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case 16: Kind = SectionKind::getMergeableConst16(); break;
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default: Kind = SectionKind::getMergeableConst(); break;
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const MCSectionELF *CPSect =
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(const MCSectionELF *)TLOF.getSectionForConstant(Kind);
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return getSection(CPSect->getSectionName(), CPSect->getType(),
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CPSect->getFlags(), CPE.getAlignment());
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// getRelocSection - Return the relocation section of section 'S'. 'RelA'
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// is true if the relocation section contains entries with addends.
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ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
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unsigned SectionType = TEW->hasRelocationAddend() ?
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ELF::SHT_RELA : ELF::SHT_REL;
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std::string SectionName(".rel");
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if (TEW->hasRelocationAddend())
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SectionName.append("a");
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SectionName.append(S.getName());
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return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
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// getGlobalELFVisibility - Returns the ELF specific visibility type
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unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
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switch (GV->getVisibility()) {
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llvm_unreachable("unknown visibility type");
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case GlobalValue::DefaultVisibility:
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return ELF::STV_DEFAULT;
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case GlobalValue::HiddenVisibility:
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return ELF::STV_HIDDEN;
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case GlobalValue::ProtectedVisibility:
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return ELF::STV_PROTECTED;
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// getGlobalELFBinding - Returns the ELF specific binding type
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unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
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if (GV->hasInternalLinkage())
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return ELF::STB_LOCAL;
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if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
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return ELF::STB_WEAK;
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return ELF::STB_GLOBAL;
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// getGlobalELFType - Returns the ELF specific type for a global
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unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
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if (GV->isDeclaration())
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return ELF::STT_NOTYPE;
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if (isa<Function>(GV))
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return ELF::STT_FUNC;
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return ELF::STT_OBJECT;
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// IsELFUndefSym - True if the global value must be marked as a symbol
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// which points to a SHN_UNDEF section. This means that the symbol has
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// no definition on the module.
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static bool IsELFUndefSym(const GlobalValue *GV) {
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return GV->isDeclaration() || (isa<Function>(GV));
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// AddToSymbolList - Update the symbol lookup and If the symbol is
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// private add it to PrivateSyms list, otherwise to SymbolList.
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void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
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assert(GblSym->isGlobalValue() && "Symbol must be a global value");
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const GlobalValue *GV = GblSym->getGlobalValue();
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if (GV->hasPrivateLinkage()) {
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// For a private symbols, keep track of the index inside
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// the private list since it will never go to the symbol
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// table and won't be patched up later.
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PrivateSyms.push_back(GblSym);
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GblSymLookup[GV] = PrivateSyms.size()-1;
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// Non private symbol are left with zero indices until
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// they are patched up during the symbol table emition
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// (where the indicies are created).
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SymbolList.push_back(GblSym);
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GblSymLookup[GV] = 0;
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// EmitGlobal - Choose the right section for global and emit it
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void ELFWriter::EmitGlobal(const GlobalValue *GV) {
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// Check if the referenced symbol is already emitted
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if (GblSymLookup.find(GV) != GblSymLookup.end())
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// Handle ELF Bind, Visibility and Type for the current symbol
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unsigned SymBind = getGlobalELFBinding(GV);
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unsigned SymType = getGlobalELFType(GV);
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bool IsUndefSym = IsELFUndefSym(GV);
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ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
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: ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
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assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
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const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
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// Handle special llvm globals
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if (EmitSpecialLLVMGlobal(GVar))
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// Get the ELF section where this global belongs from TLOF
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const MCSectionELF *S =
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(const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
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getSection(S->getSectionName(), S->getType(), S->getFlags());
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SectionKind Kind = S->getKind();
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// The symbol align should update the section alignment if needed
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const TargetData *TD = TM.getTargetData();
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unsigned Align = TD->getPreferredAlignment(GVar);
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unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
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if (S->HasCommonSymbols()) { // Symbol must go to a common section
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GblSym->SectionIdx = ELF::SHN_COMMON;
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// A new linkonce section is created for each global in the
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// common section, the default alignment is 1 and the symbol
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// value contains its alignment.
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GblSym->Value = Align;
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} else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
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GblSym->SectionIdx = ES.SectionIdx;
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// Update the size with alignment and the next object can
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// start in the right offset in the section
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if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
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ES.Align = std::max(ES.Align, Align);
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// GblSym->Value should contain the virtual offset inside the section.
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// Virtual because the BSS space is not allocated on ELF objects
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GblSym->Value = ES.Size;
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} else { // The symbol must go to some kind of data section
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GblSym->SectionIdx = ES.SectionIdx;
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// GblSym->Value should contain the symbol offset inside the section,
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// and all symbols should start on their required alignment boundary
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ES.Align = std::max(ES.Align, Align);
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ES.emitAlignment(Align);
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GblSym->Value = ES.size();
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// Emit the global to the data section 'ES'
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EmitGlobalConstant(GVar->getInitializer(), ES);
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AddToSymbolList(GblSym);
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void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
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// Print the fields in successive locations. Pad to align if needed!
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const TargetData *TD = TM.getTargetData();
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unsigned Size = TD->getTypeAllocSize(CVS->getType());
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const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
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uint64_t sizeSoFar = 0;
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for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
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const Constant* field = CVS->getOperand(i);
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// Check if padding is needed and insert one or more 0s.
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uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
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uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
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- cvsLayout->getElementOffset(i)) - fieldSize;
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sizeSoFar += fieldSize + padSize;
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// Now print the actual field value.
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EmitGlobalConstant(field, GblS);
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// Insert padding - this may include padding to increase the size of the
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// current field up to the ABI size (if the struct is not packed) as well
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// as padding to ensure that the next field starts at the right offset.
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GblS.emitZeros(padSize);
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assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
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"Layout of constant struct may be incorrect!");
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void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
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const TargetData *TD = TM.getTargetData();
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unsigned Size = TD->getTypeAllocSize(CV->getType());
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if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
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for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
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EmitGlobalConstant(CVA->getOperand(i), GblS);
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} else if (isa<ConstantAggregateZero>(CV)) {
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GblS.emitZeros(Size);
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} else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
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EmitGlobalConstantStruct(CVS, GblS);
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} else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
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APInt Val = CFP->getValueAPF().bitcastToAPInt();
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if (CFP->getType()->isDoubleTy())
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GblS.emitWord64(Val.getZExtValue());
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else if (CFP->getType()->isFloatTy())
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GblS.emitWord32(Val.getZExtValue());
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else if (CFP->getType()->isX86_FP80Ty()) {
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unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
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TD->getTypeStoreSize(CFP->getType());
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GblS.emitWordFP80(Val.getRawData(), PadSize);
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} else if (CFP->getType()->isPPC_FP128Ty())
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llvm_unreachable("PPC_FP128Ty global emission not implemented");
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} else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
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GblS.emitByte(CI->getZExtValue());
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GblS.emitWord16(CI->getZExtValue());
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GblS.emitWord32(CI->getZExtValue());
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EmitGlobalConstantLargeInt(CI, GblS);
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} else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
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const VectorType *PTy = CP->getType();
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for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
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EmitGlobalConstant(CP->getOperand(I), GblS);
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} else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
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// Resolve a constant expression which returns a (Constant, Offset)
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// pair. If 'Res.first' is a GlobalValue, emit a relocation with
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// the offset 'Res.second', otherwise emit a global constant like
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// it is always done for not contant expression types.
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CstExprResTy Res = ResolveConstantExpr(CE);
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const Constant *Op = Res.first;
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if (isa<GlobalValue>(Op))
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EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
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TD->getTypeAllocSize(Op->getType()),
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EmitGlobalConstant(Op, GblS);
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} else if (CV->getType()->getTypeID() == Type::PointerTyID) {
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// Fill the data entry with zeros or emit a relocation entry
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if (isa<ConstantPointerNull>(CV))
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GblS.emitZeros(Size);
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EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
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} else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
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// This is a constant address for a global variable or function and
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// therefore must be referenced using a relocation entry.
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EmitGlobalDataRelocation(GV, Size, GblS);
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raw_string_ostream ErrorMsg(msg);
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ErrorMsg << "Constant unimp for type: " << *CV->getType();
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report_fatal_error(ErrorMsg.str());
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// ResolveConstantExpr - Resolve the constant expression until it stop
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// yielding other constant expressions.
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CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
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const TargetData *TD = TM.getTargetData();
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// There ins't constant expression inside others anymore
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if (!isa<ConstantExpr>(CV))
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return std::make_pair(CV, 0);
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const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
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switch (CE->getOpcode()) {
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case Instruction::BitCast:
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return ResolveConstantExpr(CE->getOperand(0));
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case Instruction::GetElementPtr: {
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const Constant *ptrVal = CE->getOperand(0);
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SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
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int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
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return std::make_pair(ptrVal, Offset);
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case Instruction::IntToPtr: {
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Constant *Op = CE->getOperand(0);
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Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
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return ResolveConstantExpr(Op);
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case Instruction::PtrToInt: {
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Constant *Op = CE->getOperand(0);
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const Type *Ty = CE->getType();
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// We can emit the pointer value into this slot if the slot is an
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// integer slot greater or equal to the size of the pointer.
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if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
547
return ResolveConstantExpr(Op);
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llvm_unreachable("Integer size less then pointer size");
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case Instruction::Add:
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case Instruction::Sub: {
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// Only handle cases where there's a constant expression with GlobalValue
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// as first operand and ConstantInt as second, which are the cases we can
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// solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
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// 1) Instruction::Add => (global) + CstInt
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// 2) Instruction::Sub => (global) + -CstInt
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const Constant *Op0 = CE->getOperand(0);
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const Constant *Op1 = CE->getOperand(1);
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assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
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CstExprResTy Res = ResolveConstantExpr(Op0);
563
assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
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const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
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switch (CE->getOpcode()) {
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case Instruction::Add:
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return std::make_pair(Res.first, RHS.getSExtValue());
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case Instruction::Sub:
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return std::make_pair(Res.first, (-RHS).getSExtValue());
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report_fatal_error(CE->getOpcodeName() +
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StringRef(": Unsupported ConstantExpr type"));
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return std::make_pair(CV, 0); // silence warning
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void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
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ELFSection &GblS, int64_t Offset) {
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// Create the relocation entry for the global value
584
MachineRelocation MR =
585
MachineRelocation::getGV(GblS.getCurrentPCOffset(),
586
TEW->getAbsoluteLabelMachineRelTy(),
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const_cast<GlobalValue*>(GV),
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// Fill the data entry with zeros
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GblS.emitZeros(Size);
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// Add the relocation entry for the current data section
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GblS.addRelocation(MR);
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void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
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const TargetData *TD = TM.getTargetData();
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unsigned BitWidth = CI->getBitWidth();
601
assert(isPowerOf2_32(BitWidth) &&
602
"Non-power-of-2-sized integers not handled!");
604
const uint64_t *RawData = CI->getValue().getRawData();
606
for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
607
Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
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/// EmitSpecialLLVMGlobal - Check to see if the specified global is a
613
/// special global used by LLVM. If so, emit it and return true, otherwise
614
/// do nothing and return false.
615
bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
616
if (GV->getName() == "llvm.used")
617
llvm_unreachable("not implemented yet");
619
// Ignore debug and non-emitted data. This handles llvm.compiler.used.
620
if (GV->getSection() == "llvm.metadata" ||
621
GV->hasAvailableExternallyLinkage())
624
if (!GV->hasAppendingLinkage()) return false;
626
assert(GV->hasInitializer() && "Not a special LLVM global!");
628
const TargetData *TD = TM.getTargetData();
629
unsigned Align = TD->getPointerPrefAlignment();
630
if (GV->getName() == "llvm.global_ctors") {
631
ELFSection &Ctor = getCtorSection();
632
Ctor.emitAlignment(Align);
633
EmitXXStructorList(GV->getInitializer(), Ctor);
637
if (GV->getName() == "llvm.global_dtors") {
638
ELFSection &Dtor = getDtorSection();
639
Dtor.emitAlignment(Align);
640
EmitXXStructorList(GV->getInitializer(), Dtor);
647
/// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
648
/// function pointers, ignoring the init priority.
649
void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
650
// Should be an array of '{ int, void ()* }' structs. The first value is the
651
// init priority, which we ignore.
652
if (!isa<ConstantArray>(List)) return;
653
ConstantArray *InitList = cast<ConstantArray>(List);
654
for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
655
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
656
if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
658
if (CS->getOperand(1)->isNullValue())
659
return; // Found a null terminator, exit printing.
660
// Emit the function pointer.
661
EmitGlobalConstant(CS->getOperand(1), Xtor);
665
bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
666
// Nothing to do here, this is all done through the ElfCE object above.
670
/// doFinalization - Now that the module has been completely processed, emit
671
/// the ELF file to 'O'.
672
bool ELFWriter::doFinalization(Module &M) {
673
// Emit .data section placeholder
676
// Emit .bss section placeholder
679
// Build and emit data, bss and "common" sections.
680
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
684
// Emit all pending globals
685
for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
689
// Emit all pending externals
690
for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
692
SymbolList.push_back(ELFSym::getExtSym(*I));
694
// Emit a symbol for each section created until now, skip null section
695
for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
696
ELFSection &ES = *SectionList[i];
697
ELFSym *SectionSym = ELFSym::getSectionSym();
698
SectionSym->SectionIdx = ES.SectionIdx;
699
SymbolList.push_back(SectionSym);
700
ES.Sym = SymbolList.back();
704
EmitStringTable(M.getModuleIdentifier());
706
// Emit the symbol table now, if non-empty.
709
// Emit the relocation sections.
712
// Emit the sections string table.
713
EmitSectionTableStringTable();
715
// Dump the sections and section table to the .o file.
716
OutputSectionsAndSectionTable();
721
// RelocateField - Patch relocatable field with 'Offset' in 'BO'
722
// using a 'Value' of known 'Size'
723
void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
724
int64_t Value, unsigned Size) {
726
BO.fixWord32(Value, Offset);
728
BO.fixWord64(Value, Offset);
730
llvm_unreachable("don't know howto patch relocatable field");
733
/// EmitRelocations - Emit relocations
734
void ELFWriter::EmitRelocations() {
736
// True if the target uses the relocation entry to hold the addend,
737
// otherwise the addend is written directly to the relocatable field.
738
bool HasRelA = TEW->hasRelocationAddend();
740
// Create Relocation sections for each section which needs it.
741
for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
742
ELFSection &S = *SectionList[i];
744
// This section does not have relocations
745
if (!S.hasRelocations()) continue;
746
ELFSection &RelSec = getRelocSection(S);
748
// 'Link' - Section hdr idx of the associated symbol table
749
// 'Info' - Section hdr idx of the section to which the relocation applies
750
ELFSection &SymTab = getSymbolTableSection();
751
RelSec.Link = SymTab.SectionIdx;
752
RelSec.Info = S.SectionIdx;
753
RelSec.EntSize = TEW->getRelocationEntrySize();
755
// Get the relocations from Section
756
std::vector<MachineRelocation> Relos = S.getRelocations();
757
for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
758
MRE = Relos.end(); MRI != MRE; ++MRI) {
759
MachineRelocation &MR = *MRI;
761
// Relocatable field offset from the section start
762
unsigned RelOffset = MR.getMachineCodeOffset();
764
// Symbol index in the symbol table
767
// Target specific relocation field type and size
768
unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
769
unsigned RelTySize = TEW->getRelocationTySize(RelType);
772
// There are several machine relocations types, and each one of
773
// them needs a different approach to retrieve the symbol table index.
774
if (MR.isGlobalValue()) {
775
const GlobalValue *G = MR.getGlobalValue();
776
int64_t GlobalOffset = MR.getConstantVal();
777
SymIdx = GblSymLookup[G];
778
if (G->hasPrivateLinkage()) {
779
// If the target uses a section offset in the relocation:
780
// SymIdx + Addend = section sym for global + section offset
781
unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
782
Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
783
SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
785
Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
787
} else if (MR.isExternalSymbol()) {
788
const char *ExtSym = MR.getExternalSymbol();
789
SymIdx = ExtSymLookup[ExtSym];
790
Addend = TEW->getDefaultAddendForRelTy(RelType);
792
// Get the symbol index for the section symbol
793
unsigned SectionIdx = MR.getConstantVal();
794
SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
796
// The symbol offset inside the section
797
int64_t SymOffset = (int64_t)MR.getResultPointer();
799
// For pc relative relocations where symbols are defined in the same
800
// section they are referenced, ignore the relocation entry and patch
801
// the relocatable field with the symbol offset directly.
802
if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
803
int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
804
RelocateField(S, RelOffset, Value, RelTySize);
808
Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
811
// The target without addend on the relocation symbol must be
812
// patched in the relocation place itself to contain the addend
813
// otherwise write zeros to make sure there is no garbage there
814
RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
816
// Get the relocation entry and emit to the relocation section
817
ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
818
EmitRelocation(RelSec, Rel, HasRelA);
823
/// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
824
void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
826
RelSec.emitWord(Rel.getOffset());
827
RelSec.emitWord(Rel.getInfo(is64Bit));
829
RelSec.emitWord(Rel.getAddend());
832
/// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
833
void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
835
SymbolTable.emitWord32(Sym.NameIdx);
836
SymbolTable.emitByte(Sym.Info);
837
SymbolTable.emitByte(Sym.Other);
838
SymbolTable.emitWord16(Sym.SectionIdx);
839
SymbolTable.emitWord64(Sym.Value);
840
SymbolTable.emitWord64(Sym.Size);
842
SymbolTable.emitWord32(Sym.NameIdx);
843
SymbolTable.emitWord32(Sym.Value);
844
SymbolTable.emitWord32(Sym.Size);
845
SymbolTable.emitByte(Sym.Info);
846
SymbolTable.emitByte(Sym.Other);
847
SymbolTable.emitWord16(Sym.SectionIdx);
851
/// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
852
/// Section Header Table
853
void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
854
const ELFSection &SHdr) {
855
SHdrTab.emitWord32(SHdr.NameIdx);
856
SHdrTab.emitWord32(SHdr.Type);
858
SHdrTab.emitWord64(SHdr.Flags);
859
SHdrTab.emitWord(SHdr.Addr);
860
SHdrTab.emitWord(SHdr.Offset);
861
SHdrTab.emitWord64(SHdr.Size);
862
SHdrTab.emitWord32(SHdr.Link);
863
SHdrTab.emitWord32(SHdr.Info);
864
SHdrTab.emitWord64(SHdr.Align);
865
SHdrTab.emitWord64(SHdr.EntSize);
867
SHdrTab.emitWord32(SHdr.Flags);
868
SHdrTab.emitWord(SHdr.Addr);
869
SHdrTab.emitWord(SHdr.Offset);
870
SHdrTab.emitWord32(SHdr.Size);
871
SHdrTab.emitWord32(SHdr.Link);
872
SHdrTab.emitWord32(SHdr.Info);
873
SHdrTab.emitWord32(SHdr.Align);
874
SHdrTab.emitWord32(SHdr.EntSize);
878
/// EmitStringTable - If the current symbol table is non-empty, emit the string
880
void ELFWriter::EmitStringTable(const std::string &ModuleName) {
881
if (!SymbolList.size()) return; // Empty symbol table.
882
ELFSection &StrTab = getStringTableSection();
884
// Set the zero'th symbol to a null byte, as required.
887
// Walk on the symbol list and write symbol names into the string table.
889
for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
893
if (Sym.isGlobalValue()) {
894
SmallString<40> NameStr;
895
Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
896
Name.append(NameStr.begin(), NameStr.end());
897
} else if (Sym.isExternalSym())
898
Name.append(Sym.getExternalSymbol());
899
else if (Sym.isFileType())
900
Name.append(ModuleName);
906
StrTab.emitString(Name);
908
// Keep track of the number of bytes emitted to this section.
909
Index += Name.size()+1;
912
assert(Index == StrTab.size());
916
// SortSymbols - On the symbol table local symbols must come before
917
// all other symbols with non-local bindings. The return value is
918
// the position of the first non local symbol.
919
unsigned ELFWriter::SortSymbols() {
920
unsigned FirstNonLocalSymbol;
921
std::vector<ELFSym*> LocalSyms, OtherSyms;
923
for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
924
if ((*I)->isLocalBind())
925
LocalSyms.push_back(*I);
927
OtherSyms.push_back(*I);
930
FirstNonLocalSymbol = LocalSyms.size();
932
for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
933
SymbolList.push_back(LocalSyms[i]);
935
for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
936
SymbolList.push_back(*I);
941
return FirstNonLocalSymbol;
944
/// EmitSymbolTable - Emit the symbol table itself.
945
void ELFWriter::EmitSymbolTable() {
946
if (!SymbolList.size()) return; // Empty symbol table.
948
// Now that we have emitted the string table and know the offset into the
949
// string table of each symbol, emit the symbol table itself.
950
ELFSection &SymTab = getSymbolTableSection();
951
SymTab.Align = TEW->getPrefELFAlignment();
953
// Section Index of .strtab.
954
SymTab.Link = getStringTableSection().SectionIdx;
956
// Size of each symtab entry.
957
SymTab.EntSize = TEW->getSymTabEntrySize();
959
// Reorder the symbol table with local symbols first!
960
unsigned FirstNonLocalSymbol = SortSymbols();
962
// Emit all the symbols to the symbol table.
963
for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
964
ELFSym &Sym = *SymbolList[i];
966
// Emit symbol to the symbol table
967
EmitSymbol(SymTab, Sym);
969
// Record the symbol table index for each symbol
970
if (Sym.isGlobalValue())
971
GblSymLookup[Sym.getGlobalValue()] = i;
972
else if (Sym.isExternalSym())
973
ExtSymLookup[Sym.getExternalSymbol()] = i;
975
// Keep track on the symbol index into the symbol table
979
// One greater than the symbol table index of the last local symbol
980
SymTab.Info = FirstNonLocalSymbol;
981
SymTab.Size = SymTab.size();
984
/// EmitSectionTableStringTable - This method adds and emits a section for the
985
/// ELF Section Table string table: the string table that holds all of the
987
void ELFWriter::EmitSectionTableStringTable() {
988
// First step: add the section for the string table to the list of sections:
989
ELFSection &SHStrTab = getSectionHeaderStringTableSection();
991
// Now that we know which section number is the .shstrtab section, update the
992
// e_shstrndx entry in the ELF header.
993
ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
995
// Set the NameIdx of each section in the string table and emit the bytes for
999
for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1000
ELFSection &S = *(*I);
1001
// Set the index into the table. Note if we have lots of entries with
1002
// common suffixes, we could memoize them here if we cared.
1004
SHStrTab.emitString(S.getName());
1006
// Keep track of the number of bytes emitted to this section.
1007
Index += S.getName().size()+1;
1010
// Set the size of .shstrtab now that we know what it is.
1011
assert(Index == SHStrTab.size());
1012
SHStrTab.Size = Index;
1015
/// OutputSectionsAndSectionTable - Now that we have constructed the file header
1016
/// and all of the sections, emit these to the ostream destination and emit the
1018
void ELFWriter::OutputSectionsAndSectionTable() {
1019
// Pass #1: Compute the file offset for each section.
1020
size_t FileOff = ElfHdr.size(); // File header first.
1022
// Adjust alignment of all section if needed, skip the null section.
1023
for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1024
ELFSection &ES = *SectionList[i];
1026
ES.Offset = FileOff;
1030
// Update Section size
1032
ES.Size = ES.size();
1034
// Align FileOff to whatever the alignment restrictions of the section are.
1036
FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1038
ES.Offset = FileOff;
1042
// Align Section Header.
1043
unsigned TableAlign = TEW->getPrefELFAlignment();
1044
FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1046
// Now that we know where all of the sections will be emitted, set the e_shnum
1047
// entry in the ELF header.
1048
ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1050
// Now that we know the offset in the file of the section table, update the
1051
// e_shoff address in the ELF header.
1052
ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1054
// Now that we know all of the data in the file header, emit it and all of the
1056
O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1057
FileOff = ElfHdr.size();
1059
// Section Header Table blob
1060
BinaryObject SHdrTable(isLittleEndian, is64Bit);
1062
// Emit all of sections to the file and build the section header table.
1063
for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1064
ELFSection &S = *(*I);
1065
DEBUG(dbgs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1066
<< ", Size: " << S.Size << ", Offset: " << S.Offset
1067
<< ", SectionData Size: " << S.size() << "\n");
1069
// Align FileOff to whatever the alignment restrictions of the section are.
1072
for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1073
FileOff != NewFileOff; ++FileOff)
1076
O.write((char *)&S.getData()[0], S.Size);
1080
EmitSectionHeader(SHdrTable, S);
1083
// Align output for the section table.
1084
for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1085
FileOff != NewFileOff; ++FileOff)
1088
// Emit the section table itself.
1089
O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
added
removed
libclamav/c++/llvm/lib/CodeGen/ELFWriter.cpp
