mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73333 91177308-0d34-0410-b5e6-96231b3b80d8
612 lines
21 KiB
C++
612 lines
21 KiB
C++
//===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//===----------------------------------------------------------------------===//
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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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//
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// #1. ELF Header
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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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// ...
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// #X. '.shstrtab' section
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// #Y. Section Table
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//
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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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// ...
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// #N. ".shstrtab" entry - String table for the section names.
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//
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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 "ELF.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/FileWriters.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/CodeGen/MachineFunctionPass.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Mangler.h"
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#include "llvm/Support/Streams.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/Debug.h"
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#include <list>
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using namespace llvm;
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char ELFWriter::ID = 0;
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/// AddELFWriter - Concrete function to add the ELF writer to the function pass
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/// manager.
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MachineCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
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raw_ostream &O,
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TargetMachine &TM) {
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ELFWriter *EW = new ELFWriter(O, TM);
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PM.add(EW);
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return &EW->getMachineCodeEmitter();
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}
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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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is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
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isLittleEndian(TM.getTargetData()->isLittleEndian()),
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ElfHdr(isLittleEndian, is64Bit) {
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TAI = TM.getTargetAsmInfo();
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TEW = TM.getELFWriterInfo();
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// Create the machine code emitter object for this target.
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MCE = new ELFCodeEmitter(*this);
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// Inital number of sections
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NumSections = 0;
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}
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ELFWriter::~ELFWriter() {
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delete MCE;
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}
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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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Mang = new Mangler(M);
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// ELF Header
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// ----------
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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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//
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// Note
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// ----
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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(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(ET_REL); // e_type
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ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
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ElfHdr.emitWord32(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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getSection("", ELFSection::SHT_NULL, 0);
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// Start up the symbol table. The first entry in the symtab is the null
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// entry.
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SymbolList.push_back(ELFSym(0));
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return false;
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}
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void ELFWriter::EmitGlobal(GlobalVariable *GV) {
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// XXX: put local symbols *before* global ones!
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const Section *S = TAI->SectionForGlobal(GV);
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DOUT << "Section " << S->getName() << " for global " << GV->getName() << "\n";
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// If this is an external global, emit it now. TODO: Note that it would be
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// better to ignore the symbol here and only add it to the symbol table if
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// referenced.
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if (!GV->hasInitializer()) {
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ELFSym ExternalSym(GV);
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ExternalSym.SetBind(ELFSym::STB_GLOBAL);
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ExternalSym.SetType(ELFSym::STT_NOTYPE);
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ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
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SymbolList.push_back(ExternalSym);
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return;
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}
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const TargetData *TD = TM.getTargetData();
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unsigned Align = TD->getPreferredAlignment(GV);
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Constant *CV = GV->getInitializer();
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unsigned Size = TD->getTypeAllocSize(CV->getType());
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// If this global has a zero initializer, go to .bss or common section.
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if (CV->isNullValue() || isa<UndefValue>(CV)) {
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// If this global is part of the common block, add it now. Variables are
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// part of the common block if they are zero initialized and allowed to be
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// merged with other symbols.
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if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
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GV->hasCommonLinkage()) {
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ELFSym CommonSym(GV);
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// Value for common symbols is the alignment required.
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CommonSym.Value = Align;
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CommonSym.Size = Size;
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CommonSym.SetBind(ELFSym::STB_GLOBAL);
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CommonSym.SetType(ELFSym::STT_OBJECT);
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CommonSym.SectionIdx = ELFSection::SHN_COMMON;
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SymbolList.push_back(CommonSym);
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getSection(S->getName(), ELFSection::SHT_NOBITS,
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ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 1);
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return;
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}
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// Otherwise, this symbol is part of the .bss section. Emit it now.
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// Handle alignment. Ensure section is aligned at least as much as required
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// by this symbol.
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ELFSection &BSSSection = getBSSSection();
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BSSSection.Align = std::max(BSSSection.Align, Align);
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// Within the section, emit enough virtual padding to get us to an alignment
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// boundary.
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if (Align)
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BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);
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ELFSym BSSSym(GV);
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BSSSym.Value = BSSSection.Size;
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BSSSym.Size = Size;
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BSSSym.SetType(ELFSym::STT_OBJECT);
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switch (GV->getLinkage()) {
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default: // weak/linkonce/common handled above
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assert(0 && "Unexpected linkage type!");
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case GlobalValue::AppendingLinkage: // FIXME: This should be improved!
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case GlobalValue::ExternalLinkage:
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BSSSym.SetBind(ELFSym::STB_GLOBAL);
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break;
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case GlobalValue::InternalLinkage:
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BSSSym.SetBind(ELFSym::STB_LOCAL);
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break;
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}
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// Set the idx of the .bss section
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BSSSym.SectionIdx = BSSSection.SectionIdx;
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if (!GV->hasPrivateLinkage())
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SymbolList.push_back(BSSSym);
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// Reserve space in the .bss section for this symbol.
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BSSSection.Size += Size;
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return;
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}
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/// Emit the Global symbol to the right ELF section
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ELFSym GblSym(GV);
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GblSym.Size = Size;
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GblSym.SetType(ELFSym::STT_OBJECT);
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GblSym.SetBind(ELFSym::STB_GLOBAL);
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unsigned Flags = S->getFlags();
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unsigned SectType = ELFSection::SHT_PROGBITS;
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unsigned SHdrFlags = ELFSection::SHF_ALLOC;
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if (Flags & SectionFlags::Code)
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SHdrFlags |= ELFSection::SHF_EXECINSTR;
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if (Flags & SectionFlags::Writeable)
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SHdrFlags |= ELFSection::SHF_WRITE;
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if (Flags & SectionFlags::Mergeable)
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SHdrFlags |= ELFSection::SHF_MERGE;
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if (Flags & SectionFlags::TLS)
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SHdrFlags |= ELFSection::SHF_TLS;
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if (Flags & SectionFlags::Strings)
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SHdrFlags |= ELFSection::SHF_STRINGS;
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// Remove tab from section name prefix
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std::string SectionName(S->getName());
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size_t Pos = SectionName.find("\t");
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if (Pos != std::string::npos)
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SectionName.erase(Pos, 1);
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// The section alignment should be bound to the element with
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// the largest alignment
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ELFSection &ElfS = getSection(SectionName, SectType, SHdrFlags);
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GblSym.SectionIdx = ElfS.SectionIdx;
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if (Align > ElfS.Align)
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ElfS.Align = Align;
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// S.Value should contain the symbol index inside the section,
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// and all symbols should start on their required alignment boundary
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GblSym.Value = (ElfS.size() + (Align-1)) & (-Align);
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ElfS.emitAlignment(Align);
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// Emit the constant symbol to its section
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EmitGlobalConstant(CV, ElfS);
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SymbolList.push_back(GblSym);
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}
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void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
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ELFSection &GblS) {
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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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for (unsigned p=0; p < padSize; p++)
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GblS.emitByte(0);
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}
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assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
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"Layout of constant struct may be incorrect!");
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}
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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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if (CVA->isString()) {
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std::string GblStr = CVA->getAsString();
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GblS.emitString(GblStr);
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} else { // Not a string. Print the values in successive locations
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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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}
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return;
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} else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
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EmitGlobalConstantStruct(CVS, GblS);
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return;
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} else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
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uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
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if (CFP->getType() == Type::DoubleTy)
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GblS.emitWord64(Val);
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else if (CFP->getType() == Type::FloatTy)
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GblS.emitWord32(Val);
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else if (CFP->getType() == Type::X86_FP80Ty) {
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assert(0 && "X86_FP80Ty global emission not implemented");
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} else if (CFP->getType() == Type::PPC_FP128Ty)
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assert(0 && "PPC_FP128Ty global emission not implemented");
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return;
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} else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
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if (Size == 4)
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GblS.emitWord32(CI->getZExtValue());
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else if (Size == 8)
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GblS.emitWord64(CI->getZExtValue());
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else
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assert(0 && "LargeInt global emission not implemented");
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return;
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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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return;
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}
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assert(0 && "unknown global constant");
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}
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bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
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// Nothing to do here, this is all done through the MCE object above.
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return false;
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}
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/// doFinalization - Now that the module has been completely processed, emit
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/// the ELF file to 'O'.
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bool ELFWriter::doFinalization(Module &M) {
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/// FIXME: This should be removed when moving to ObjectCodeEmiter. Since the
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/// current ELFCodeEmiter uses CurrBuff, ... it doesn't update S.Data
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/// vector size for .text sections, so this is a quick dirty fix
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ELFSection &TS = getTextSection();
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if (TS.Size) {
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BinaryData &BD = TS.getData();
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for (unsigned e=0; e<TS.Size; ++e)
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BD.push_back(BD[e]);
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}
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// Emit .data section placeholder
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getDataSection();
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// Emit .bss section placeholder
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getBSSSection();
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// Build and emit data, bss and "common" sections.
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for (Module::global_iterator I = M.global_begin(), E = M.global_end();
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I != E; ++I)
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EmitGlobal(I);
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// Emit non-executable stack note
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if (TAI->getNonexecutableStackDirective())
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getNonExecStackSection();
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// Emit the symbol table now, if non-empty.
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EmitSymbolTable();
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// Emit the relocation sections.
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EmitRelocations();
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// Emit the sections string table.
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EmitSectionTableStringTable();
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// Dump the sections and section table to the .o file.
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OutputSectionsAndSectionTable();
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// We are done with the abstract symbols.
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SectionList.clear();
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NumSections = 0;
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// Release the name mangler object.
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delete Mang; Mang = 0;
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return false;
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}
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/// EmitRelocations - Emit relocations
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void ELFWriter::EmitRelocations() {
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}
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/// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
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void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
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if (is64Bit) {
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SymbolTable.emitWord32(Sym.NameIdx);
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SymbolTable.emitByte(Sym.Info);
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SymbolTable.emitByte(Sym.Other);
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SymbolTable.emitWord16(Sym.SectionIdx);
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SymbolTable.emitWord64(Sym.Value);
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SymbolTable.emitWord64(Sym.Size);
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} else {
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SymbolTable.emitWord32(Sym.NameIdx);
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SymbolTable.emitWord32(Sym.Value);
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SymbolTable.emitWord32(Sym.Size);
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SymbolTable.emitByte(Sym.Info);
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SymbolTable.emitByte(Sym.Other);
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SymbolTable.emitWord16(Sym.SectionIdx);
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}
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}
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/// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
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/// Section Header Table
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void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
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const ELFSection &SHdr) {
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SHdrTab.emitWord32(SHdr.NameIdx);
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SHdrTab.emitWord32(SHdr.Type);
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if (is64Bit) {
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SHdrTab.emitWord64(SHdr.Flags);
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SHdrTab.emitWord(SHdr.Addr);
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SHdrTab.emitWord(SHdr.Offset);
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SHdrTab.emitWord64(SHdr.Size);
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SHdrTab.emitWord32(SHdr.Link);
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SHdrTab.emitWord32(SHdr.Info);
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SHdrTab.emitWord64(SHdr.Align);
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SHdrTab.emitWord64(SHdr.EntSize);
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} else {
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SHdrTab.emitWord32(SHdr.Flags);
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SHdrTab.emitWord(SHdr.Addr);
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SHdrTab.emitWord(SHdr.Offset);
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SHdrTab.emitWord32(SHdr.Size);
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SHdrTab.emitWord32(SHdr.Link);
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SHdrTab.emitWord32(SHdr.Info);
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SHdrTab.emitWord32(SHdr.Align);
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SHdrTab.emitWord32(SHdr.EntSize);
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}
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}
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/// EmitSymbolTable - If the current symbol table is non-empty, emit the string
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/// table for it and then the symbol table itself.
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void ELFWriter::EmitSymbolTable() {
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if (SymbolList.size() == 1) return; // Only the null entry.
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// FIXME: compact all local symbols to the start of the symtab.
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unsigned FirstNonLocalSymbol = 1;
|
|
|
|
ELFSection &StrTab = getStringTableSection();
|
|
|
|
// Set the zero'th symbol to a null byte, as required.
|
|
StrTab.emitByte(0);
|
|
|
|
unsigned Index = 1;
|
|
for (unsigned i = 1, e = SymbolList.size(); i != e; ++i) {
|
|
// Use the name mangler to uniquify the LLVM symbol.
|
|
std::string Name = Mang->getValueName(SymbolList[i].GV);
|
|
|
|
if (Name.empty()) {
|
|
SymbolList[i].NameIdx = 0;
|
|
} else {
|
|
SymbolList[i].NameIdx = Index;
|
|
StrTab.emitString(Name);
|
|
|
|
// Keep track of the number of bytes emitted to this section.
|
|
Index += Name.size()+1;
|
|
}
|
|
}
|
|
assert(Index == StrTab.size());
|
|
StrTab.Size = Index;
|
|
|
|
// Now that we have emitted the string table and know the offset into the
|
|
// string table of each symbol, emit the symbol table itself.
|
|
ELFSection &SymTab = getSymbolTableSection();
|
|
SymTab.Align = TEW->getSymTabAlignment();
|
|
SymTab.Link = StrTab.SectionIdx; // Section Index of .strtab.
|
|
SymTab.Info = FirstNonLocalSymbol; // First non-STB_LOCAL symbol.
|
|
|
|
// Size of each symtab entry.
|
|
SymTab.EntSize = TEW->getSymTabEntrySize();
|
|
|
|
for (unsigned i = 0, e = SymbolList.size(); i != e; ++i)
|
|
EmitSymbol(SymTab, SymbolList[i]);
|
|
|
|
SymTab.Size = SymTab.size();
|
|
}
|
|
|
|
/// EmitSectionTableStringTable - This method adds and emits a section for the
|
|
/// ELF Section Table string table: the string table that holds all of the
|
|
/// section names.
|
|
void ELFWriter::EmitSectionTableStringTable() {
|
|
// First step: add the section for the string table to the list of sections:
|
|
ELFSection &SHStrTab = getSection(".shstrtab", ELFSection::SHT_STRTAB, 0);
|
|
|
|
// Now that we know which section number is the .shstrtab section, update the
|
|
// e_shstrndx entry in the ELF header.
|
|
ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
|
|
|
|
// Set the NameIdx of each section in the string table and emit the bytes for
|
|
// the string table.
|
|
unsigned Index = 0;
|
|
|
|
for (std::list<ELFSection>::iterator I = SectionList.begin(),
|
|
E = SectionList.end(); I != E; ++I) {
|
|
// Set the index into the table. Note if we have lots of entries with
|
|
// common suffixes, we could memoize them here if we cared.
|
|
I->NameIdx = Index;
|
|
SHStrTab.emitString(I->getName());
|
|
|
|
// Keep track of the number of bytes emitted to this section.
|
|
Index += I->getName().size()+1;
|
|
}
|
|
|
|
// Set the size of .shstrtab now that we know what it is.
|
|
assert(Index == SHStrTab.size());
|
|
SHStrTab.Size = Index;
|
|
}
|
|
|
|
/// OutputSectionsAndSectionTable - Now that we have constructed the file header
|
|
/// and all of the sections, emit these to the ostream destination and emit the
|
|
/// SectionTable.
|
|
void ELFWriter::OutputSectionsAndSectionTable() {
|
|
// Pass #1: Compute the file offset for each section.
|
|
size_t FileOff = ElfHdr.size(); // File header first.
|
|
|
|
// Adjust alignment of all section if needed.
|
|
for (std::list<ELFSection>::iterator I = SectionList.begin(),
|
|
E = SectionList.end(); I != E; ++I) {
|
|
|
|
// Section idx 0 has 0 offset
|
|
if (!I->SectionIdx)
|
|
continue;
|
|
|
|
if (!I->size()) {
|
|
I->Offset = FileOff;
|
|
continue;
|
|
}
|
|
|
|
// Update Section size
|
|
if (!I->Size)
|
|
I->Size = I->size();
|
|
|
|
// Align FileOff to whatever the alignment restrictions of the section are.
|
|
if (I->Align)
|
|
FileOff = (FileOff+I->Align-1) & ~(I->Align-1);
|
|
|
|
I->Offset = FileOff;
|
|
FileOff += I->Size;
|
|
}
|
|
|
|
// Align Section Header.
|
|
unsigned TableAlign = is64Bit ? 8 : 4;
|
|
FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
|
|
|
|
// Now that we know where all of the sections will be emitted, set the e_shnum
|
|
// entry in the ELF header.
|
|
ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
|
|
|
|
// Now that we know the offset in the file of the section table, update the
|
|
// e_shoff address in the ELF header.
|
|
ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
|
|
|
|
// Now that we know all of the data in the file header, emit it and all of the
|
|
// sections!
|
|
O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
|
|
FileOff = ElfHdr.size();
|
|
|
|
// Section Header Table blob
|
|
BinaryObject SHdrTable(isLittleEndian, is64Bit);
|
|
|
|
// Emit all of sections to the file and build the section header table.
|
|
while (!SectionList.empty()) {
|
|
ELFSection &S = *SectionList.begin();
|
|
DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
|
|
<< ", Size: " << S.Size << ", Offset: " << S.Offset
|
|
<< ", SectionData Size: " << S.size() << "\n";
|
|
|
|
// Align FileOff to whatever the alignment restrictions of the section are.
|
|
if (S.Align) {
|
|
for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
|
|
FileOff != NewFileOff; ++FileOff)
|
|
O << (char)0xAB;
|
|
}
|
|
|
|
if (S.size()) {
|
|
O.write((char *)&S.getData()[0], S.Size);
|
|
FileOff += S.Size;
|
|
}
|
|
|
|
EmitSectionHeader(SHdrTable, S);
|
|
SectionList.pop_front();
|
|
}
|
|
|
|
// Align output for the section table.
|
|
for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
|
|
FileOff != NewFileOff; ++FileOff)
|
|
O << (char)0xAB;
|
|
|
|
// Emit the section table itself.
|
|
O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
|
|
}
|