llvm-6502/lib/CodeGen/MachOWriter.cpp

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//===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Nate Begeman and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the target-independent Mach-O writer. This file writes
// out the Mach-O file in the following order:
//
// #1 FatHeader (universal-only)
// #2 FatArch (universal-only, 1 per universal arch)
// Per arch:
// #3 Header
// #4 Load Commands
// #5 Sections
// #6 Relocations
// #7 Symbols
// #8 Strings
//
//===----------------------------------------------------------------------===//
#include "llvm/Module.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachOWriter.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <iostream>
using namespace llvm;
//===----------------------------------------------------------------------===//
// MachOCodeEmitter Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// MachOCodeEmitter - This class is used by the MachOWriter to emit the code
/// for functions to the Mach-O file.
class MachOCodeEmitter : public MachineCodeEmitter {
MachOWriter &MOW;
/// MOS - The current section we're writing to
MachOWriter::MachOSection *MOS;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
/// MBBLocations - This vector is a mapping from MBB ID's to their address.
/// It is filled in by the StartMachineBasicBlock callback and queried by
/// the getMachineBasicBlockAddress callback.
std::vector<intptr_t> MBBLocations;
public:
MachOCodeEmitter(MachOWriter &mow) : MOW(mow) {}
void startFunction(MachineFunction &F);
bool finishFunction(MachineFunction &F);
void addRelocation(const MachineRelocation &MR) {
Relocations.push_back(MR);
}
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
if (MBBLocations.size() <= (unsigned)MBB->getNumber())
MBBLocations.resize((MBB->getNumber()+1)*2);
MBBLocations[MBB->getNumber()] = getCurrentPCValue();
}
virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const {
assert(0 && "CP not implementated yet!");
return 0;
}
virtual intptr_t getJumpTableEntryAddress(unsigned Index) const {
assert(0 && "JT not implementated yet!");
return 0;
}
virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
assert(MBBLocations.size() > (unsigned)MBB->getNumber() &&
MBBLocations[MBB->getNumber()] && "MBB not emitted!");
return MBBLocations[MBB->getNumber()];
}
/// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
void startFunctionStub(unsigned StubSize) {
assert(0 && "JIT specific function called!");
abort();
}
void *finishFunctionStub(const Function *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 MachOCodeEmitter::startFunction(MachineFunction &F) {
// Align the output buffer to the appropriate alignment, power of 2.
// FIXME: GENERICIZE!!
unsigned Align = 4;
// Get the Mach-O Section that this function belongs in.
MOS = &MOW.getTextSection();
// FIXME: better memory management
MOS->SectionData.reserve(4096);
BufferBegin = &(MOS->SectionData[0]);
BufferEnd = BufferBegin + MOS->SectionData.capacity();
CurBufferPtr = BufferBegin + MOS->size;
// Upgrade the section alignment if required.
if (MOS->align < Align) MOS->align = Align;
// Make sure we only relocate to this function's MBBs.
MBBLocations.clear();
}
/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool MachOCodeEmitter::finishFunction(MachineFunction &F) {
MOS->size += CurBufferPtr - BufferBegin;
// Get a symbol for the function to add to the symbol table
const GlobalValue *FuncV = F.getFunction();
MachOSym FnSym(FuncV, MOW.Mang->getValueName(FuncV), MOS->Index);
// FIXME: emit constant pool to appropriate section(s)
// FIXME: emit jump table to appropriate section
// Resolve the function's relocations either to concrete pointers in the case
// of branches from one block to another, or to target relocation entries.
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
MachineRelocation &MR = Relocations[i];
if (MR.isBasicBlock()) {
void *MBBAddr = (void *)getMachineBasicBlockAddress(MR.getBasicBlock());
MR.setResultPointer(MBBAddr);
MOW.TM.getJITInfo()->relocate(BufferBegin, &MR, 1, 0);
} else if (MR.isConstantPoolIndex() || MR.isJumpTableIndex()) {
// Get the address of the index.
uint64_t Addr = 0;
// Generate the relocation(s) for the index.
MOW.GetTargetRelocation(*MOS, MR, Addr);
} else {
// Handle other types later once we've finalized the sections in the file.
MOS->Relocations.push_back(MR);
}
}
Relocations.clear();
// Finally, add it to the symtab.
MOW.SymbolTable.push_back(FnSym);
return false;
}
//===----------------------------------------------------------------------===//
// MachOWriter Implementation
//===----------------------------------------------------------------------===//
MachOWriter::MachOWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
isLittleEndian = TM.getTargetData()->isLittleEndian();
// Create the machine code emitter object for this target.
MCE = new MachOCodeEmitter(*this);
}
MachOWriter::~MachOWriter() {
delete MCE;
}
void MachOWriter::AddSymbolToSection(MachOSection &Sec, GlobalVariable *GV) {
const Type *Ty = GV->getType()->getElementType();
unsigned Size = TM.getTargetData()->getTypeSize(Ty);
unsigned Align = Log2_32(TM.getTargetData()->getTypeAlignment(Ty));
MachOSym Sym(GV, Mang->getValueName(GV), Sec.Index);
// Reserve space in the .bss section for this symbol while maintaining the
// desired section alignment, which must be at least as much as required by
// this symbol.
if (Align) {
Sec.align = std::max(unsigned(Sec.align), Align);
Sec.size = (Sec.size + Align - 1) & ~(Align-1);
}
// Record the offset of the symbol, and then allocate space for it.
Sym.n_value = Sec.size;
Sec.size += Size;
switch (GV->getLinkage()) {
default: // weak/linkonce handled above
assert(0 && "Unexpected linkage type!");
case GlobalValue::ExternalLinkage:
Sym.n_type |= MachOSym::N_EXT;
break;
case GlobalValue::InternalLinkage:
break;
}
SymbolTable.push_back(Sym);
}
void MachOWriter::EmitGlobal(GlobalVariable *GV) {
const Type *Ty = GV->getType()->getElementType();
unsigned Size = TM.getTargetData()->getTypeSize(Ty);
bool NoInit = !GV->hasInitializer();
// If this global has a zero initializer, it is part of the .bss or common
// section.
if (NoInit || 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 (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
MachOSym ExtOrCommonSym(GV, Mang->getValueName(GV), MachOSym::NO_SECT);
// For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
// bytes of the symbol.
ExtOrCommonSym.n_value = Size;
// If the symbol is external, we'll put it on a list of symbols whose
// addition to the symbol table is being pended until we find a reference
if (NoInit)
PendingSyms.push_back(ExtOrCommonSym);
else
SymbolTable.push_back(ExtOrCommonSym);
return;
}
// Otherwise, this symbol is part of the .bss section.
MachOSection &BSS = getBSSSection();
AddSymbolToSection(BSS, GV);
return;
}
// Scalar read-only data goes in a literal section if the scalar is 4, 8, or
// 16 bytes, or a cstring. Other read only data goes into a regular const
// section. Read-write data goes in the data section.
MachOSection &Sec = GV->isConstant() ? getConstSection(Ty) : getDataSection();
AddSymbolToSection(Sec, GV);
// FIXME: A couple significant changes are required for this to work, even for
// trivial cases such as a constant integer:
// 0. InitializeMemory needs to be split out of ExecutionEngine. We don't
// want to have to create an ExecutionEngine such as JIT just to write
// some bytes into a buffer. The only thing necessary for
// InitializeMemory to function properly should be TargetData.
//
// 1. InitializeMemory needs to be enhanced to return MachineRelocations
// rather than accessing the address of objects such basic blocks,
// constant pools, and jump tables. The client of InitializeMemory such
// as an object writer or jit emitter should then handle these relocs
// appropriately.
//
// FIXME: need to allocate memory for the global initializer.
}
bool MachOWriter::runOnMachineFunction(MachineFunction &MF) {
// Nothing to do here, this is all done through the MCE object.
return false;
}
bool MachOWriter::doInitialization(Module &M) {
// Set the magic value, now that we know the pointer size and endianness
Header.setMagic(isLittleEndian, is64Bit);
// Set the file type
// FIXME: this only works for object files, we do not support the creation
// of dynamic libraries or executables at this time.
Header.filetype = MachOHeader::MH_OBJECT;
Mang = new Mangler(M);
return false;
}
/// doFinalization - Now that the module has been completely processed, emit
/// the Mach-O file to 'O'.
bool MachOWriter::doFinalization(Module &M) {
// FIXME: we don't handle debug info yet, we should probably do that.
// Okay, the.text section has 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 to temporary buffers, so that we know the size of
// the string table when we write the load commands in the next phase.
BufferSymbolAndStringTable();
// Emit the header and load commands.
EmitHeaderAndLoadCommands();
// Emit the text and data sections.
EmitSections();
// Emit the relocation entry data for each section.
O.write((char*)&RelocBuffer[0], RelocBuffer.size());
// Write the symbol table and the string table to the end of the file.
O.write((char*)&SymT[0], SymT.size());
O.write((char*)&StrT[0], StrT.size());
// We are done with the abstract symbols.
SectionList.clear();
SymbolTable.clear();
DynamicSymbolTable.clear();
// Release the name mangler object.
delete Mang; Mang = 0;
return false;
}
void MachOWriter::EmitHeaderAndLoadCommands() {
// Step #0: Fill in the segment load command size, since we need it to figure
// out the rest of the header fields
MachOSegment SEG("", is64Bit);
SEG.nsects = SectionList.size();
SEG.cmdsize = SEG.cmdSize(is64Bit) +
SEG.nsects * SectionList.begin()->cmdSize(is64Bit);
// Step #1: calculate the number of load commands. We always have at least
// one, for the LC_SEGMENT load command, plus two for the normal
// and dynamic symbol tables, if there are any symbols.
Header.ncmds = SymbolTable.empty() ? 1 : 3;
// Step #2: calculate the size of the load commands
Header.sizeofcmds = SEG.cmdsize;
if (!SymbolTable.empty())
Header.sizeofcmds += SymTab.cmdsize + DySymTab.cmdsize;
// Step #3: write the header to the file
// Local alias to shortenify coming code.
DataBuffer &FH = Header.HeaderData;
outword(FH, Header.magic);
outword(FH, Header.cputype);
outword(FH, Header.cpusubtype);
outword(FH, Header.filetype);
outword(FH, Header.ncmds);
outword(FH, Header.sizeofcmds);
outword(FH, Header.flags);
if (is64Bit)
outword(FH, Header.reserved);
// Step #4: Finish filling in the segment load command and write it out
for (std::list<MachOSection>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I)
SEG.filesize += I->size;
SEG.vmsize = SEG.filesize;
SEG.fileoff = Header.cmdSize(is64Bit) + Header.sizeofcmds;
outword(FH, SEG.cmd);
outword(FH, SEG.cmdsize);
outstring(FH, SEG.segname, 16);
outaddr(FH, SEG.vmaddr);
outaddr(FH, SEG.vmsize);
outaddr(FH, SEG.fileoff);
outaddr(FH, SEG.filesize);
outword(FH, SEG.maxprot);
outword(FH, SEG.initprot);
outword(FH, SEG.nsects);
outword(FH, SEG.flags);
// Step #5: Finish filling in the fields of the MachOSections
uint64_t currentAddr = 0;
for (std::list<MachOSection>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
I->addr = currentAddr;
I->offset = currentAddr + SEG.fileoff;
// FIXME: do we need to do something with alignment here?
currentAddr += I->size;
}
// Step #6: Calculate the number of relocations for each section and write out
// the section commands for each section
currentAddr += SEG.fileoff;
for (std::list<MachOSection>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
// calculate the relocation info for this section command
// FIXME: this could get complicated calculating the address argument, we
// should probably split this out into its own function.
for (unsigned i = 0, e = I->Relocations.size(); i != e; ++i)
GetTargetRelocation(*I, I->Relocations[i], 0);
if (I->nreloc != 0) {
I->reloff = currentAddr;
currentAddr += I->nreloc * 8;
}
// write the finalized section command to the output buffer
outstring(FH, I->sectname, 16);
outstring(FH, I->segname, 16);
outaddr(FH, I->addr);
outaddr(FH, I->size);
outword(FH, I->offset);
outword(FH, I->align);
outword(FH, I->reloff);
outword(FH, I->nreloc);
outword(FH, I->flags);
outword(FH, I->reserved1);
outword(FH, I->reserved2);
if (is64Bit)
outword(FH, I->reserved3);
}
// Step #7: Emit LC_SYMTAB/LC_DYSYMTAB load commands
// FIXME: add size of relocs
SymTab.symoff = currentAddr;
SymTab.nsyms = SymbolTable.size();
SymTab.stroff = SymTab.symoff + SymT.size();
SymTab.strsize = StrT.size();
outword(FH, SymTab.cmd);
outword(FH, SymTab.cmdsize);
outword(FH, SymTab.symoff);
outword(FH, SymTab.nsyms);
outword(FH, SymTab.stroff);
outword(FH, SymTab.strsize);
// FIXME: set DySymTab fields appropriately
// We should probably just update these in BufferSymbolAndStringTable since
// thats where we're partitioning up the different kinds of symbols.
outword(FH, DySymTab.cmd);
outword(FH, DySymTab.cmdsize);
outword(FH, DySymTab.ilocalsym);
outword(FH, DySymTab.nlocalsym);
outword(FH, DySymTab.iextdefsym);
outword(FH, DySymTab.nextdefsym);
outword(FH, DySymTab.iundefsym);
outword(FH, DySymTab.nundefsym);
outword(FH, DySymTab.tocoff);
outword(FH, DySymTab.ntoc);
outword(FH, DySymTab.modtaboff);
outword(FH, DySymTab.nmodtab);
outword(FH, DySymTab.extrefsymoff);
outword(FH, DySymTab.nextrefsyms);
outword(FH, DySymTab.indirectsymoff);
outword(FH, DySymTab.nindirectsyms);
outword(FH, DySymTab.extreloff);
outword(FH, DySymTab.nextrel);
outword(FH, DySymTab.locreloff);
outword(FH, DySymTab.nlocrel);
O.write((char*)&FH[0], FH.size());
}
/// EmitSections - Now that we have constructed the file header and load
/// commands, emit the data for each section to the file.
void MachOWriter::EmitSections() {
for (std::list<MachOSection>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
O.write((char*)&I->SectionData[0], I->size);
}
}
/// PartitionByLocal - Simple boolean predicate that returns true if Sym is
/// a local symbol rather than an external symbol.
bool MachOWriter::PartitionByLocal(const MachOSym &Sym) {
// FIXME: Not totally sure if private extern counts as external
return (Sym.n_type & (MachOSym::N_EXT | MachOSym::N_PEXT)) == 0;
}
/// PartitionByDefined - Simple boolean predicate that returns true if Sym is
/// defined in this module.
bool MachOWriter::PartitionByDefined(const MachOSym &Sym) {
// FIXME: Do N_ABS or N_INDR count as defined?
return (Sym.n_type & MachOSym::N_SECT) == MachOSym::N_SECT;
}
/// BufferSymbolAndStringTable - Sort the symbols we encountered and assign them
/// each a string table index so that they appear in the correct order in the
/// output file.
void MachOWriter::BufferSymbolAndStringTable() {
// The order of the symbol table is:
// 1. local symbols
// 2. defined external symbols (sorted by name)
// 3. undefined external symbols (sorted by name)
// Sort the symbols by name, so that when we partition the symbols by scope
// of definition, we won't have to sort by name within each partition.
std::sort(SymbolTable.begin(), SymbolTable.end(), MachOSymCmp());
// Parition the symbol table entries so that all local symbols come before
// all symbols with external linkage. { 1 | 2 3 }
std::partition(SymbolTable.begin(), SymbolTable.end(), PartitionByLocal);
// Advance iterator to beginning of external symbols and partition so that
// all external symbols defined in this module come before all external
// symbols defined elsewhere. { 1 | 2 | 3 }
for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
E = SymbolTable.end(); I != E; ++I) {
if (!PartitionByLocal(*I)) {
std::partition(I, E, PartitionByDefined);
break;
}
}
// Write out a leading zero byte when emitting string table, for n_strx == 0
// which means an empty string.
outbyte(StrT, 0);
// The order of the string table is:
// 1. strings for external symbols
// 2. strings for local symbols
// Since this is the opposite order from the symbol table, which we have just
// sorted, we can walk the symbol table backwards to output the string table.
for (std::vector<MachOSym>::reverse_iterator I = SymbolTable.rbegin(),
E = SymbolTable.rend(); I != E; ++I) {
if (I->GVName == "") {
I->n_strx = 0;
} else {
I->n_strx = StrT.size();
outstring(StrT, I->GVName, I->GVName.length()+1);
}
}
for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
E = SymbolTable.end(); I != E; ++I) {
// Emit nlist to buffer
outword(SymT, I->n_strx);
outbyte(SymT, I->n_type);
outbyte(SymT, I->n_sect);
outhalf(SymT, I->n_desc);
outaddr(SymT, I->n_value);
}
}
MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect) :
GV(gv), GVName(name), n_strx(0), n_type(sect == NO_SECT ? N_UNDF : N_SECT),
n_sect(sect), n_desc(0), n_value(0) {
// FIXME: take a target machine, and then add the appropriate prefix for
// the linkage type based on the TargetAsmInfo
switch (GV->getLinkage()) {
default:
assert(0 && "Unexpected linkage type!");
break;
case GlobalValue::WeakLinkage:
case GlobalValue::LinkOnceLinkage:
assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
case GlobalValue::ExternalLinkage:
n_type |= N_EXT;
break;
case GlobalValue::InternalLinkage:
break;
}
}