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llvm-mirror/lib/CodeGen/ELFWriter.cpp
Nate Begeman 5e78e558ff Add support to the JIT for true non-lazy operation. When a call to a function 
that has not been JIT'd yet, the callee is put on a list of pending functions
to JIT.  The call is directed through a stub, which is updated with the address
of the function after it has been JIT'd.  A new interface for allocating and
updating empty stubs is provided.

Add support for removing the ModuleProvider the JIT was created with, which
would otherwise invalidate the JIT's PassManager, which is initialized with the
ModuleProvider's Module.

Add support under a new ExecutionEngine flag for emitting the infomration 
necessary to update Function and GlobalVariable stubs after JITing them, by
recording the address of the stub and the name of the GlobalValue.  This allows
code to be copied from one address space to another, where libraries may live
at different virtual addresses, and have the stubs updated with their new
correct target addresses.

llvm-svn: 64906
2009-02-18 08:31:02 +00:00

574 lines
20 KiB
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Raw Blame History

//===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the target-independent ELF writer. This file writes out
// the ELF file in the following order:
//
// #1. ELF Header
// #2. '.text' section
// #3. '.data' section
// #4. '.bss' section (conceptual position in file)
// ...
// #X. '.shstrtab' section
// #Y. Section Table
//
// The entries in the section table are laid out as:
// #0. Null entry [required]
// #1. ".text" entry - the program code
// #2. ".data" entry - global variables with initializers. [ if needed ]
// #3. ".bss" entry - global variables without initializers. [ if needed ]
// ...
// #N. ".shstrtab" entry - String table for the section names.
//
// NOTE: This code should eventually be extended to support 64-bit ELF (this
// won't be hard), but we haven't done so yet!
//
//===----------------------------------------------------------------------===//
#include "ELFWriter.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/DerivedTypes.h"
#include "llvm/CodeGen/FileWriters.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetELFWriterInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/OutputBuffer.h"
#include "llvm/Support/Streams.h"
#include "llvm/Support/raw_ostream.h"
#include <list>
using namespace llvm;
char ELFWriter::ID = 0;
/// AddELFWriter - Concrete function to add the ELF writer to the function pass
/// manager.
MachineCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
raw_ostream &O,
TargetMachine &TM) {
ELFWriter *EW = new ELFWriter(O, TM);
PM.add(EW);
return &EW->getMachineCodeEmitter();
}
//===----------------------------------------------------------------------===//
// ELFCodeEmitter Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// ELFCodeEmitter - This class is used by the ELFWriter to emit the code for
/// functions to the ELF file.
class ELFCodeEmitter : public MachineCodeEmitter {
ELFWriter &EW;
TargetMachine &TM;
ELFWriter::ELFSection *ES; // Section to write to.
std::vector<unsigned char> *OutBuffer;
size_t FnStart;
public:
explicit ELFCodeEmitter(ELFWriter &ew) : EW(ew), TM(EW.TM), OutBuffer(0) {}
void startFunction(MachineFunction &F);
bool finishFunction(MachineFunction &F);
void addRelocation(const MachineRelocation &MR) {
assert(0 && "relo not handled yet!");
}
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
}
virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const {
assert(0 && "CP not implementated yet!");
return 0;
}
virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const {
assert(0 && "JT not implementated yet!");
return 0;
}
virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
assert(0 && "JT not implementated yet!");
return 0;
}
virtual uintptr_t getLabelAddress(uint64_t Label) const {
assert(0 && "Label address not implementated yet!");
abort();
return 0;
}
virtual void emitLabel(uint64_t LabelID) {
assert(0 && "emit Label not implementated yet!");
abort();
}
virtual void setModuleInfo(llvm::MachineModuleInfo* MMI) { }
/// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
void startGVStub(const GlobalValue* F, unsigned StubSize,
unsigned Alignment = 1) {
assert(0 && "JIT specific function called!");
abort();
}
void startGVStub(const GlobalValue* F, void *Buffer, unsigned StubSize) {
assert(0 && "JIT specific function called!");
abort();
}
void *finishGVStub(const GlobalValue *F) {
assert(0 && "JIT specific function called!");
abort();
return 0;
}
};
}
/// startFunction - This callback is invoked when a new machine function is
/// about to be emitted.
void ELFCodeEmitter::startFunction(MachineFunction &F) {
// Align the output buffer to the appropriate alignment.
unsigned Align = 16; // FIXME: GENERICIZE!!
// Get the ELF Section that this function belongs in.
ES = &EW.getSection(".text", ELFWriter::ELFSection::SHT_PROGBITS,
ELFWriter::ELFSection::SHF_EXECINSTR |
ELFWriter::ELFSection::SHF_ALLOC);
OutBuffer = &ES->SectionData;
cerr << "FIXME: This code needs to be updated for changes in the "
<< "CodeEmitter interfaces. In particular, this should set "
<< "BufferBegin/BufferEnd/CurBufferPtr, not deal with OutBuffer!";
abort();
// Upgrade the section alignment if required.
if (ES->Align < Align) ES->Align = Align;
// Add padding zeros to the end of the buffer to make sure that the
// function will start on the correct byte alignment within the section.
OutputBuffer OB(*OutBuffer,
TM.getTargetData()->getPointerSizeInBits() == 64,
TM.getTargetData()->isLittleEndian());
OB.align(Align);
FnStart = OutBuffer->size();
}
/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool ELFCodeEmitter::finishFunction(MachineFunction &F) {
// We now know the size of the function, add a symbol to represent it.
ELFWriter::ELFSym FnSym(F.getFunction());
// Figure out the binding (linkage) of the symbol.
switch (F.getFunction()->getLinkage()) {
default:
// appending linkage is illegal for functions.
assert(0 && "Unknown linkage type!");
case GlobalValue::ExternalLinkage:
FnSym.SetBind(ELFWriter::ELFSym::STB_GLOBAL);
break;
case GlobalValue::LinkOnceLinkage:
case GlobalValue::WeakLinkage:
FnSym.SetBind(ELFWriter::ELFSym::STB_WEAK);
break;
case GlobalValue::PrivateLinkage:
assert (0 && "PrivateLinkage should not be in the symbol table.");
case GlobalValue::InternalLinkage:
FnSym.SetBind(ELFWriter::ELFSym::STB_LOCAL);
break;
}
ES->Size = OutBuffer->size();
FnSym.SetType(ELFWriter::ELFSym::STT_FUNC);
FnSym.SectionIdx = ES->SectionIdx;
FnSym.Value = FnStart; // Value = Offset from start of Section.
FnSym.Size = OutBuffer->size()-FnStart;
// Finally, add it to the symtab.
EW.SymbolTable.push_back(FnSym);
return false;
}
//===----------------------------------------------------------------------===//
// ELFWriter Implementation
//===----------------------------------------------------------------------===//
ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
: MachineFunctionPass(&ID), O(o), TM(tm) {
e_flags = 0; // e_flags defaults to 0, no flags.
is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
isLittleEndian = TM.getTargetData()->isLittleEndian();
// Create the machine code emitter object for this target.
MCE = new ELFCodeEmitter(*this);
NumSections = 0;
}
ELFWriter::~ELFWriter() {
delete MCE;
}
// doInitialization - Emit the file header and all of the global variables for
// the module to the ELF file.
bool ELFWriter::doInitialization(Module &M) {
Mang = new Mangler(M);
// Local alias to shortenify coming code.
std::vector<unsigned char> &FH = FileHeader;
OutputBuffer FHOut(FH, is64Bit, isLittleEndian);
FHOut.outbyte(0x7F); // EI_MAG0
FHOut.outbyte('E'); // EI_MAG1
FHOut.outbyte('L'); // EI_MAG2
FHOut.outbyte('F'); // EI_MAG3
FHOut.outbyte(is64Bit ? 2 : 1); // EI_CLASS
FHOut.outbyte(isLittleEndian ? 1 : 2); // EI_DATA
FHOut.outbyte(1); // EI_VERSION
FH.resize(16); // EI_PAD up to 16 bytes.
// This should change for shared objects.
FHOut.outhalf(1); // e_type = ET_REL
FHOut.outhalf(TM.getELFWriterInfo()->getEMachine()); // target-defined
FHOut.outword(1); // e_version = 1
FHOut.outaddr(0); // e_entry = 0 -> no entry point in .o file
FHOut.outaddr(0); // e_phoff = 0 -> no program header for .o
ELFHeader_e_shoff_Offset = FH.size();
FHOut.outaddr(0); // e_shoff
FHOut.outword(e_flags); // e_flags = whatever the target wants
FHOut.outhalf(is64Bit ? 64 : 52); // e_ehsize = ELF header size
FHOut.outhalf(0); // e_phentsize = prog header entry size
FHOut.outhalf(0); // e_phnum = # prog header entries = 0
FHOut.outhalf(is64Bit ? 64 : 40); // e_shentsize = sect hdr entry size
ELFHeader_e_shnum_Offset = FH.size();
FHOut.outhalf(0); // e_shnum = # of section header ents
ELFHeader_e_shstrndx_Offset = FH.size();
FHOut.outhalf(0); // e_shstrndx = Section # of '.shstrtab'
// Add the null section, which is required to be first in the file.
getSection("", 0, 0);
// Start up the symbol table. The first entry in the symtab is the null
// entry.
SymbolTable.push_back(ELFSym(0));
return false;
}
void ELFWriter::EmitGlobal(GlobalVariable *GV) {
// If this is an external global, emit it now. TODO: Note that it would be
// better to ignore the symbol here and only add it to the symbol table if
// referenced.
if (!GV->hasInitializer()) {
ELFSym ExternalSym(GV);
ExternalSym.SetBind(ELFSym::STB_GLOBAL);
ExternalSym.SetType(ELFSym::STT_NOTYPE);
ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
SymbolTable.push_back(ExternalSym);
return;
}
unsigned Align = TM.getTargetData()->getPreferredAlignment(GV);
unsigned Size =
TM.getTargetData()->getTypePaddedSize(GV->getType()->getElementType());
// If this global has a zero initializer, it is part of the .bss or common
// section.
if (GV->getInitializer()->isNullValue()) {
// If this global is part of the common block, add it now. Variables are
// part of the common block if they are zero initialized and allowed to be
// merged with other symbols.
if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
GV->hasCommonLinkage()) {
ELFSym CommonSym(GV);
// Value for common symbols is the alignment required.
CommonSym.Value = Align;
CommonSym.Size = Size;
CommonSym.SetBind(ELFSym::STB_GLOBAL);
CommonSym.SetType(ELFSym::STT_OBJECT);
// TODO SOMEDAY: add ELF visibility.
CommonSym.SectionIdx = ELFSection::SHN_COMMON;
SymbolTable.push_back(CommonSym);
return;
}
// Otherwise, this symbol is part of the .bss section. Emit it now.
// Handle alignment. Ensure section is aligned at least as much as required
// by this symbol.
ELFSection &BSSSection = getBSSSection();
BSSSection.Align = std::max(BSSSection.Align, Align);
// Within the section, emit enough virtual padding to get us to an alignment
// boundary.
if (Align)
BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);
ELFSym BSSSym(GV);
BSSSym.Value = BSSSection.Size;
BSSSym.Size = Size;
BSSSym.SetType(ELFSym::STT_OBJECT);
switch (GV->getLinkage()) {
default: // weak/linkonce/common handled above
assert(0 && "Unexpected linkage type!");
case GlobalValue::AppendingLinkage: // FIXME: This should be improved!
case GlobalValue::ExternalLinkage:
BSSSym.SetBind(ELFSym::STB_GLOBAL);
break;
case GlobalValue::InternalLinkage:
BSSSym.SetBind(ELFSym::STB_LOCAL);
break;
}
// Set the idx of the .bss section
BSSSym.SectionIdx = BSSSection.SectionIdx;
if (!GV->hasPrivateLinkage())
SymbolTable.push_back(BSSSym);
// Reserve space in the .bss section for this symbol.
BSSSection.Size += Size;
return;
}
// FIXME: handle .rodata
//assert(!GV->isConstant() && "unimp");
// FIXME: handle .data
//assert(0 && "unimp");
}
bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
// Nothing to do here, this is all done through the MCE object above.
return false;
}
/// doFinalization - Now that the module has been completely processed, emit
/// the ELF file to 'O'.
bool ELFWriter::doFinalization(Module &M) {
// Okay, the ELF header and .text sections have been completed, build the
// .data, .bss, and "common" sections next.
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
EmitGlobal(I);
// Emit the symbol table now, if non-empty.
EmitSymbolTable();
// FIXME: Emit the relocations now.
// Emit the string table for the sections in the ELF file we have.
EmitSectionTableStringTable();
// Emit the sections to the .o file, and emit the section table for the file.
OutputSectionsAndSectionTable();
// We are done with the abstract symbols.
SectionList.clear();
NumSections = 0;
// Release the name mangler object.
delete Mang; Mang = 0;
return false;
}
/// EmitSymbolTable - If the current symbol table is non-empty, emit the string
/// table for it and then the symbol table itself.
void ELFWriter::EmitSymbolTable() {
if (SymbolTable.size() == 1) return; // Only the null entry.
// FIXME: compact all local symbols to the start of the symtab.
unsigned FirstNonLocalSymbol = 1;
ELFSection &StrTab = getSection(".strtab", ELFSection::SHT_STRTAB, 0);
StrTab.Align = 1;
DataBuffer &StrTabBuf = StrTab.SectionData;
OutputBuffer StrTabOut(StrTabBuf, is64Bit, isLittleEndian);
// Set the zero'th symbol to a null byte, as required.
StrTabOut.outbyte(0);
SymbolTable[0].NameIdx = 0;
unsigned Index = 1;
for (unsigned i = 1, e = SymbolTable.size(); i != e; ++i) {
// Use the name mangler to uniquify the LLVM symbol.
std::string Name = Mang->getValueName(SymbolTable[i].GV);
if (Name.empty()) {
SymbolTable[i].NameIdx = 0;
} else {
SymbolTable[i].NameIdx = Index;
// Add the name to the output buffer, including the null terminator.
StrTabBuf.insert(StrTabBuf.end(), Name.begin(), Name.end());
// Add a null terminator.
StrTabBuf.push_back(0);
// Keep track of the number of bytes emitted to this section.
Index += Name.size()+1;
}
}
assert(Index == StrTabBuf.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 = getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
SymTab.Align = is64Bit ? 8 : 4;
SymTab.Link = SymTab.SectionIdx; // Section Index of .strtab.
SymTab.Info = FirstNonLocalSymbol; // First non-STB_LOCAL symbol.
SymTab.EntSize = 16; // Size of each symtab entry. FIXME: wrong for ELF64
DataBuffer &SymTabBuf = SymTab.SectionData;
OutputBuffer SymTabOut(SymTabBuf, is64Bit, isLittleEndian);
if (!is64Bit) { // 32-bit and 64-bit formats are shuffled a bit.
for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
ELFSym &Sym = SymbolTable[i];
SymTabOut.outword(Sym.NameIdx);
SymTabOut.outaddr32(Sym.Value);
SymTabOut.outword(Sym.Size);
SymTabOut.outbyte(Sym.Info);
SymTabOut.outbyte(Sym.Other);
SymTabOut.outhalf(Sym.SectionIdx);
}
} else {
for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
ELFSym &Sym = SymbolTable[i];
SymTabOut.outword(Sym.NameIdx);
SymTabOut.outbyte(Sym.Info);
SymTabOut.outbyte(Sym.Other);
SymTabOut.outhalf(Sym.SectionIdx);
SymTabOut.outaddr64(Sym.Value);
SymTabOut.outxword(Sym.Size);
}
}
SymTab.Size = SymTabBuf.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.
OutputBuffer FHOut(FileHeader, is64Bit, isLittleEndian);
FHOut.fixhalf(SHStrTab.SectionIdx, ELFHeader_e_shstrndx_Offset);
// Set the NameIdx of each section in the string table and emit the bytes for
// the string table.
unsigned Index = 0;
DataBuffer &Buf = SHStrTab.SectionData;
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;
// Add the name to the output buffer, including the null terminator.
Buf.insert(Buf.end(), I->Name.begin(), I->Name.end());
// Add a null terminator.
Buf.push_back(0);
// Keep track of the number of bytes emitted to this section.
Index += I->Name.size()+1;
}
// Set the size of .shstrtab now that we know what it is.
assert(Index == Buf.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 = FileHeader.size(); // File header first.
// Emit all of the section data in order.
for (std::list<ELFSection>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
// 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->SectionData.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.
OutputBuffer FHOut(FileHeader, is64Bit, isLittleEndian);
FHOut.fixhalf(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.
FHOut.fixaddr(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;
OutputBuffer TableOut(Table, is64Bit, isLittleEndian);
// 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 << (char)0xAB;
O.write((char*)&S.SectionData[0], S.SectionData.size());
FileOff += S.SectionData.size();
TableOut.outword(S.NameIdx); // sh_name - Symbol table name idx
TableOut.outword(S.Type); // sh_type - Section contents & semantics
TableOut.outword(S.Flags); // sh_flags - Section flags.
TableOut.outaddr(S.Addr); // sh_addr - The mem addr this section is in.
TableOut.outaddr(S.Offset); // sh_offset - Offset from the file start.
TableOut.outword(S.Size); // sh_size - The section size.
TableOut.outword(S.Link); // sh_link - Section header table index link.
TableOut.outword(S.Info); // sh_info - Auxillary information.
TableOut.outword(S.Align); // sh_addralign - Alignment of section.
TableOut.outword(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 << (char)0xAB;
// Emit the section table itself.
O.write((char*)&Table[0], Table.size());
}
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