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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24278 91177308-0d34-0410-b5e6-96231b3b80d8
527 lines
18 KiB
C++
527 lines
18 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 was developed by Chris Lattner and is distributed under the
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// University of Illinois Open Source 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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// NOTE: This code should eventually be extended to support 64-bit ELF (this
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// won't be hard), but we haven't done so yet!
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/ELFWriter.h"
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#include "llvm/Module.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/Target/TargetMachine.h"
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#include "llvm/Support/Mangler.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// ELFCodeEmitter Implementation
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//===----------------------------------------------------------------------===//
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namespace llvm {
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/// ELFCodeEmitter - This class is used by the ELFWriter to emit the code for
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/// functions to the ELF file.
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class ELFCodeEmitter : public MachineCodeEmitter {
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ELFWriter &EW;
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ELFWriter::ELFSection *ES; // Section to write to.
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std::vector<unsigned char> *OutBuffer;
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size_t FnStart;
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public:
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ELFCodeEmitter(ELFWriter &ew) : EW(ew), OutBuffer(0) {}
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void startFunction(MachineFunction &F);
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void finishFunction(MachineFunction &F);
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void emitConstantPool(MachineConstantPool *MCP) {
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if (MCP->isEmpty()) return;
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assert(0 && "unimp");
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}
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virtual void emitByte(unsigned char B) {
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OutBuffer->push_back(B);
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}
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virtual void emitWordAt(unsigned W, unsigned *Ptr) {
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assert(0 && "ni");
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}
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virtual void emitWord(unsigned W) {
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assert(0 && "ni");
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}
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virtual uint64_t getCurrentPCValue() {
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return OutBuffer->size();
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}
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virtual uint64_t getCurrentPCOffset() {
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return OutBuffer->size()-FnStart;
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}
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void addRelocation(const MachineRelocation &MR) {
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assert(0 && "relo not handled yet!");
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}
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virtual uint64_t getConstantPoolEntryAddress(unsigned Index) {
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assert(0 && "CP not implementated yet!");
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return 0;
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}
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virtual unsigned char* allocateGlobal(unsigned size, unsigned alignment) {
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assert(0 && "Globals not implemented yet!");
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return 0;
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}
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/// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
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void startFunctionStub(unsigned StubSize) {
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assert(0 && "JIT specific function called!");
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abort();
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}
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void *finishFunctionStub(const Function *F) {
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assert(0 && "JIT specific function called!");
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abort();
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return 0;
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}
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};
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}
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/// startFunction - This callback is invoked when a new machine function is
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/// about to be emitted.
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void ELFCodeEmitter::startFunction(MachineFunction &F) {
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// Align the output buffer to the appropriate alignment.
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unsigned Align = 16; // FIXME: GENERICIZE!!
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// Get the ELF Section that this function belongs in.
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ES = &EW.getSection(".text", ELFWriter::ELFSection::SHT_PROGBITS,
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ELFWriter::ELFSection::SHF_EXECINSTR |
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ELFWriter::ELFSection::SHF_ALLOC);
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OutBuffer = &ES->SectionData;
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// Upgrade the section alignment if required.
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if (ES->Align < Align) ES->Align = Align;
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// Add padding zeros to the end of the buffer to make sure that the
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// function will start on the correct byte alignment within the section.
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size_t SectionOff = OutBuffer->size();
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ELFWriter::align(*OutBuffer, Align);
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FnStart = OutBuffer->size();
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}
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/// finishFunction - This callback is invoked after the function is completely
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/// finished.
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void ELFCodeEmitter::finishFunction(MachineFunction &F) {
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// We now know the size of the function, add a symbol to represent it.
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ELFWriter::ELFSym FnSym(F.getFunction());
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// Figure out the binding (linkage) of the symbol.
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switch (F.getFunction()->getLinkage()) {
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default:
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// appending linkage is illegal for functions.
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assert(0 && "Unknown linkage type!");
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case GlobalValue::ExternalLinkage:
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FnSym.SetBind(ELFWriter::ELFSym::STB_GLOBAL);
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break;
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case GlobalValue::LinkOnceLinkage:
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case GlobalValue::WeakLinkage:
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FnSym.SetBind(ELFWriter::ELFSym::STB_WEAK);
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break;
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case GlobalValue::InternalLinkage:
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FnSym.SetBind(ELFWriter::ELFSym::STB_LOCAL);
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break;
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}
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ES->Size = OutBuffer->size();
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FnSym.SetType(ELFWriter::ELFSym::STT_FUNC);
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FnSym.SectionIdx = ES->SectionIdx;
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FnSym.Value = FnStart; // Value = Offset from start of Section.
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FnSym.Size = OutBuffer->size()-FnStart;
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// Finally, add it to the symtab.
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EW.SymbolTable.push_back(FnSym);
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}
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//===----------------------------------------------------------------------===//
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// ELFWriter Implementation
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//===----------------------------------------------------------------------===//
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ELFWriter::ELFWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
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e_machine = 0; // e_machine defaults to 'No Machine'
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e_flags = 0; // e_flags defaults to 0, no flags.
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is64Bit = TM.getTargetData().getPointerSizeInBits() == 64;
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isLittleEndian = TM.getTargetData().isLittleEndian();
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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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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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// Local alias to shortenify coming code.
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std::vector<unsigned char> &FH = FileHeader;
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outbyte(FH, 0x7F); // EI_MAG0
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outbyte(FH, 'E'); // EI_MAG1
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outbyte(FH, 'L'); // EI_MAG2
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outbyte(FH, 'F'); // EI_MAG3
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outbyte(FH, is64Bit ? 2 : 1); // EI_CLASS
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outbyte(FH, isLittleEndian ? 1 : 2); // EI_DATA
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outbyte(FH, 1); // EI_VERSION
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FH.resize(16); // EI_PAD up to 16 bytes.
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// This should change for shared objects.
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outhalf(FH, 1); // e_type = ET_REL
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outhalf(FH, e_machine); // e_machine = whatever the target wants
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outword(FH, 1); // e_version = 1
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outaddr(FH, 0); // e_entry = 0 -> no entry point in .o file
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outaddr(FH, 0); // e_phoff = 0 -> no program header for .o
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ELFHeader_e_shoff_Offset = FH.size();
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outaddr(FH, 0); // e_shoff
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outword(FH, e_flags); // e_flags = whatever the target wants
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outhalf(FH, is64Bit ? 64 : 52); // e_ehsize = ELF header size
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outhalf(FH, 0); // e_phentsize = prog header entry size
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outhalf(FH, 0); // e_phnum = # prog header entries = 0
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outhalf(FH, is64Bit ? 64 : 40); // e_shentsize = sect hdr entry size
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ELFHeader_e_shnum_Offset = FH.size();
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outhalf(FH, 0); // e_shnum = # of section header ents
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ELFHeader_e_shstrndx_Offset = FH.size();
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outhalf(FH, 0); // e_shstrndx = Section # of '.shstrtab'
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// Add the null section, which is required to be first in the file.
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getSection("", 0, 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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SymbolTable.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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// 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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SymbolTable.push_back(ExternalSym);
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return;
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}
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const Type *GVType = (const Type*)GV->getType();
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unsigned Align = TM.getTargetData().getTypeAlignment(GVType);
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unsigned Size = TM.getTargetData().getTypeSize(GVType);
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// If this global has a zero initializer, it is part of the .bss or common
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// section.
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if (GV->getInitializer()->isNullValue()) {
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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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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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// TODO SOMEDAY: add ELF visibility.
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CommonSym.SectionIdx = ELFSection::SHN_COMMON;
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SymbolTable.push_back(CommonSym);
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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 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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SymbolTable.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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// FIXME: handle .rodata
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//assert(!GV->isConstant() && "unimp");
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// FIXME: handle .data
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//assert(0 && "unimp");
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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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// Okay, the ELF header and .text sections have been completed, build the
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// .data, .bss, and "common" sections next.
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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 the symbol table now, if non-empty.
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EmitSymbolTable();
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// FIXME: Emit the relocations now.
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// Emit the string table for the sections in the ELF file we have.
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EmitSectionTableStringTable();
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// Emit the sections to the .o file, and emit the section table for the 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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/// 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 (SymbolTable.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;
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ELFSection &StrTab = getSection(".strtab", ELFSection::SHT_STRTAB, 0);
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StrTab.Align = 1;
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DataBuffer &StrTabBuf = StrTab.SectionData;
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// Set the zero'th symbol to a null byte, as required.
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outbyte(StrTabBuf, 0);
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SymbolTable[0].NameIdx = 0;
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unsigned Index = 1;
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for (unsigned i = 1, e = SymbolTable.size(); i != e; ++i) {
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// Use the name mangler to uniquify the LLVM symbol.
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std::string Name = Mang->getValueName(SymbolTable[i].GV);
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if (Name.empty()) {
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SymbolTable[i].NameIdx = 0;
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} else {
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SymbolTable[i].NameIdx = Index;
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// Add the name to the output buffer, including the null terminator.
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StrTabBuf.insert(StrTabBuf.end(), Name.begin(), Name.end());
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// Add a null terminator.
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StrTabBuf.push_back(0);
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// Keep track of the number of bytes emitted to this section.
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Index += Name.size()+1;
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}
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}
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assert(Index == StrTabBuf.size());
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StrTab.Size = Index;
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// Now that we have emitted the string table and know the offset into the
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// string table of each symbol, emit the symbol table itself.
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ELFSection &SymTab = getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
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SymTab.Align = is64Bit ? 8 : 4;
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SymTab.Link = SymTab.SectionIdx; // Section Index of .strtab.
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SymTab.Info = FirstNonLocalSymbol; // First non-STB_LOCAL symbol.
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SymTab.EntSize = 16; // Size of each symtab entry. FIXME: wrong for ELF64
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DataBuffer &SymTabBuf = SymTab.SectionData;
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if (!is64Bit) { // 32-bit and 64-bit formats are shuffled a bit.
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for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
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ELFSym &Sym = SymbolTable[i];
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outword(SymTabBuf, Sym.NameIdx);
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outaddr32(SymTabBuf, Sym.Value);
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outword(SymTabBuf, Sym.Size);
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outbyte(SymTabBuf, Sym.Info);
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outbyte(SymTabBuf, Sym.Other);
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outhalf(SymTabBuf, Sym.SectionIdx);
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}
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} else {
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for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
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ELFSym &Sym = SymbolTable[i];
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outword(SymTabBuf, Sym.NameIdx);
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outbyte(SymTabBuf, Sym.Info);
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outbyte(SymTabBuf, Sym.Other);
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outhalf(SymTabBuf, Sym.SectionIdx);
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outaddr64(SymTabBuf, Sym.Value);
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outxword(SymTabBuf, Sym.Size);
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}
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}
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SymTab.Size = SymTabBuf.size();
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}
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/// EmitSectionTableStringTable - This method adds and emits a section for the
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/// ELF Section Table string table: the string table that holds all of the
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/// section names.
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void ELFWriter::EmitSectionTableStringTable() {
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// First step: add the section for the string table to the list of sections:
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ELFSection &SHStrTab = getSection(".shstrtab", ELFSection::SHT_STRTAB, 0);
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// Now that we know which section number is the .shstrtab section, update the
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// e_shstrndx entry in the ELF header.
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fixhalf(FileHeader, SHStrTab.SectionIdx, ELFHeader_e_shstrndx_Offset);
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// Set the NameIdx of each section in the string table and emit the bytes for
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// the string table.
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unsigned Index = 0;
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DataBuffer &Buf = SHStrTab.SectionData;
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for (std::list<ELFSection>::iterator I = SectionList.begin(),
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E = SectionList.end(); I != E; ++I) {
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// Set the index into the table. Note if we have lots of entries with
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// common suffixes, we could memoize them here if we cared.
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I->NameIdx = Index;
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// Add the name to the output buffer, including the null terminator.
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Buf.insert(Buf.end(), I->Name.begin(), I->Name.end());
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// Add a null terminator.
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Buf.push_back(0);
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// Keep track of the number of bytes emitted to this section.
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Index += I->Name.size()+1;
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}
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// Set the size of .shstrtab now that we know what it is.
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assert(Index == Buf.size());
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SHStrTab.Size = Index;
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}
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/// OutputSectionsAndSectionTable - Now that we have constructed the file header
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/// and all of the sections, emit these to the ostream destination and emit the
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/// SectionTable.
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void ELFWriter::OutputSectionsAndSectionTable() {
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// Pass #1: Compute the file offset for each section.
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size_t FileOff = FileHeader.size(); // File header first.
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// Emit all of the section data in order.
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for (std::list<ELFSection>::iterator I = SectionList.begin(),
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E = SectionList.end(); I != E; ++I) {
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// Align FileOff to whatever the alignment restrictions of the section are.
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if (I->Align)
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FileOff = (FileOff+I->Align-1) & ~(I->Align-1);
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I->Offset = FileOff;
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FileOff += I->SectionData.size();
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}
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// Align Section Header.
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unsigned TableAlign = is64Bit ? 8 : 4;
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FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
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// Now that we know where all of the sections will be emitted, set the e_shnum
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// entry in the ELF header.
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fixhalf(FileHeader, NumSections, ELFHeader_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.
|
|
fixaddr(FileHeader, FileOff, ELFHeader_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*)&FileHeader[0], FileHeader.size());
|
|
FileOff = FileHeader.size();
|
|
DataBuffer().swap(FileHeader);
|
|
|
|
DataBuffer Table;
|
|
|
|
// Emit all of the section data and build the section table itself.
|
|
while (!SectionList.empty()) {
|
|
const ELFSection &S = *SectionList.begin();
|
|
|
|
// 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.put((char)0xAB);
|
|
O.write((char*)&S.SectionData[0], S.SectionData.size());
|
|
FileOff += S.SectionData.size();
|
|
|
|
outword(Table, S.NameIdx); // sh_name - Symbol table name idx
|
|
outword(Table, S.Type); // sh_type - Section contents & semantics
|
|
outword(Table, S.Flags); // sh_flags - Section flags.
|
|
outaddr(Table, S.Addr); // sh_addr - The mem addr this section is in.
|
|
outaddr(Table, S.Offset); // sh_offset - Offset from the file start.
|
|
outword(Table, S.Size); // sh_size - The section size.
|
|
outword(Table, S.Link); // sh_link - Section header table index link.
|
|
outword(Table, S.Info); // sh_info - Auxillary information.
|
|
outword(Table, S.Align); // sh_addralign - Alignment of section.
|
|
outword(Table, S.EntSize); // sh_entsize - Size of entries in the section.
|
|
|
|
SectionList.pop_front();
|
|
}
|
|
|
|
// Align output for the section table.
|
|
for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
|
|
FileOff != NewFileOff; ++FileOff)
|
|
O.put((char)0xAB);
|
|
|
|
// Emit the section table itself.
|
|
O.write((char*)&Table[0], Table.size());
|
|
}
|