//===- GNULDBackend.cpp ---------------------------------------------------===//
//
// The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "mcld/Target/GNULDBackend.h"
#include "mcld/IRBuilder.h"
#include "mcld/InputTree.h"
#include "mcld/LinkerConfig.h"
#include "mcld/LinkerScript.h"
#include "mcld/Module.h"
#include "mcld/ADT/SizeTraits.h"
#include "mcld/Config/Config.h"
#include "mcld/Fragment/FillFragment.h"
#include "mcld/LD/BranchIslandFactory.h"
#include "mcld/LD/EhFrame.h"
#include "mcld/LD/EhFrameHdr.h"
#include "mcld/LD/ELFDynObjFileFormat.h"
#include "mcld/LD/ELFExecFileFormat.h"
#include "mcld/LD/ELFFileFormat.h"
#include "mcld/LD/ELFObjectFileFormat.h"
#include "mcld/LD/ELFSegment.h"
#include "mcld/LD/ELFSegmentFactory.h"
#include "mcld/LD/LDContext.h"
#include "mcld/LD/LDSymbol.h"
#include "mcld/LD/RelocData.h"
#include "mcld/LD/RelocationFactory.h"
#include "mcld/LD/StubFactory.h"
#include "mcld/MC/Attribute.h"
#include "mcld/Object/ObjectBuilder.h"
#include "mcld/Object/SectionMap.h"
#include "mcld/Script/Operand.h"
#include "mcld/Script/OutputSectDesc.h"
#include "mcld/Script/RpnEvaluator.h"
#include "mcld/Support/FileOutputBuffer.h"
#include "mcld/Support/MsgHandling.h"
#include "mcld/Target/ELFAttribute.h"
#include "mcld/Target/ELFDynamic.h"
#include "mcld/Target/GNUInfo.h"
#include <llvm/ADT/StringRef.h>
#include <llvm/Support/Host.h>
#include <algorithm>
#include <cstring>
#include <cassert>
#include <map>
#include <string>
#include <vector>
namespace {
//===----------------------------------------------------------------------===//
// non-member functions
//===----------------------------------------------------------------------===//
static const std::string simple_c_identifier_allowed_chars =
"0123456789"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"_";
/// isCIdentifier - return if the pName is a valid C identifier
static bool isCIdentifier(const std::string& pName) {
return (pName.find_first_not_of(simple_c_identifier_allowed_chars) ==
std::string::npos);
}
} // anonymous namespace
namespace mcld {
//===----------------------------------------------------------------------===//
// GNULDBackend
//===----------------------------------------------------------------------===//
GNULDBackend::GNULDBackend(const LinkerConfig& pConfig, GNUInfo* pInfo)
: TargetLDBackend(pConfig),
m_pObjectReader(NULL),
m_pDynObjFileFormat(NULL),
m_pExecFileFormat(NULL),
m_pObjectFileFormat(NULL),
m_pInfo(pInfo),
m_pELFSegmentTable(NULL),
m_pBRIslandFactory(NULL),
m_pStubFactory(NULL),
m_pEhFrameHdr(NULL),
m_pAttribute(NULL),
m_bHasTextRel(false),
m_bHasStaticTLS(false),
f_pPreInitArrayStart(NULL),
f_pPreInitArrayEnd(NULL),
f_pInitArrayStart(NULL),
f_pInitArrayEnd(NULL),
f_pFiniArrayStart(NULL),
f_pFiniArrayEnd(NULL),
f_pStack(NULL),
f_pDynamic(NULL),
f_pTDATA(NULL),
f_pTBSS(NULL),
f_pExecutableStart(NULL),
f_pEText(NULL),
f_p_EText(NULL),
f_p__EText(NULL),
f_pEData(NULL),
f_p_EData(NULL),
f_pBSSStart(NULL),
f_pEnd(NULL),
f_p_End(NULL) {
m_pELFSegmentTable = new ELFSegmentFactory();
m_pSymIndexMap = new HashTableType(1024);
m_pAttribute = new ELFAttribute(*this, pConfig);
}
GNULDBackend::~GNULDBackend() {
delete m_pELFSegmentTable;
delete m_pInfo;
delete m_pDynObjFileFormat;
delete m_pExecFileFormat;
delete m_pObjectFileFormat;
delete m_pSymIndexMap;
delete m_pEhFrameHdr;
delete m_pAttribute;
delete m_pBRIslandFactory;
delete m_pStubFactory;
}
size_t GNULDBackend::sectionStartOffset() const {
if (LinkerConfig::Binary == config().codeGenType())
return 0x0;
switch (config().targets().bitclass()) {
case 32u:
return sizeof(llvm::ELF::Elf32_Ehdr) +
elfSegmentTable().size() * sizeof(llvm::ELF::Elf32_Phdr);
case 64u:
return sizeof(llvm::ELF::Elf64_Ehdr) +
elfSegmentTable().size() * sizeof(llvm::ELF::Elf64_Phdr);
default:
fatal(diag::unsupported_bitclass) << config().targets().triple().str()
<< config().targets().bitclass();
return 0;
}
}
uint64_t GNULDBackend::getSegmentStartAddr(const LinkerScript& pScript) const {
LinkerScript::AddressMap::const_iterator mapping =
pScript.addressMap().find(".text");
if (pScript.addressMap().end() != mapping)
return mapping.getEntry()->value();
else if (config().isCodeIndep())
return 0x0;
else
return m_pInfo->defaultTextSegmentAddr();
}
GNUArchiveReader* GNULDBackend::createArchiveReader(Module& pModule) {
assert(m_pObjectReader != NULL);
return new GNUArchiveReader(pModule, *m_pObjectReader);
}
ELFObjectReader* GNULDBackend::createObjectReader(IRBuilder& pBuilder) {
m_pObjectReader = new ELFObjectReader(*this, pBuilder, config());
return m_pObjectReader;
}
ELFDynObjReader* GNULDBackend::createDynObjReader(IRBuilder& pBuilder) {
return new ELFDynObjReader(*this, pBuilder, config());
}
ELFBinaryReader* GNULDBackend::createBinaryReader(IRBuilder& pBuilder) {
return new ELFBinaryReader(pBuilder, config());
}
ELFObjectWriter* GNULDBackend::createWriter() {
return new ELFObjectWriter(*this, config());
}
bool GNULDBackend::initStdSections(ObjectBuilder& pBuilder) {
switch (config().codeGenType()) {
case LinkerConfig::DynObj: {
if (m_pDynObjFileFormat == NULL)
m_pDynObjFileFormat = new ELFDynObjFileFormat();
m_pDynObjFileFormat->initStdSections(pBuilder,
config().targets().bitclass());
return true;
}
case LinkerConfig::Exec:
case LinkerConfig::Binary: {
if (m_pExecFileFormat == NULL)
m_pExecFileFormat = new ELFExecFileFormat();
m_pExecFileFormat->initStdSections(pBuilder,
config().targets().bitclass());
return true;
}
case LinkerConfig::Object: {
if (m_pObjectFileFormat == NULL)
m_pObjectFileFormat = new ELFObjectFileFormat();
m_pObjectFileFormat->initStdSections(pBuilder,
config().targets().bitclass());
return true;
}
default:
fatal(diag::unrecognized_output_file) << config().codeGenType();
return false;
}
}
/// initStandardSymbols - define and initialize standard symbols.
/// This function is called after section merging but before read relocations.
bool GNULDBackend::initStandardSymbols(IRBuilder& pBuilder, Module& pModule) {
if (LinkerConfig::Object == config().codeGenType())
return true;
// GNU extension: define __start and __stop symbols for the sections whose
// name can be presented as C symbol
Module::iterator iter, iterEnd = pModule.end();
for (iter = pModule.begin(); iter != iterEnd; ++iter) {
LDSection* section = *iter;
switch (section->kind()) {
case LDFileFormat::Relocation:
continue;
case LDFileFormat::EhFrame:
if (!section->hasEhFrame())
continue;
break;
default:
if (!section->hasSectionData())
continue;
break;
} // end of switch
if (isCIdentifier(section->name())) {
std::string start_name = "__start_" + section->name();
FragmentRef* start_fragref =
FragmentRef::Create(section->getSectionData()->front(), 0x0);
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
start_name,
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
start_fragref, // FragRef
ResolveInfo::Default);
std::string stop_name = "__stop_" + section->name();
FragmentRef* stop_fragref = FragmentRef::Create(
section->getSectionData()->front(), section->size());
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
stop_name,
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
stop_fragref, // FragRef
ResolveInfo::Default);
}
}
ELFFileFormat* file_format = getOutputFormat();
// ----- section symbols ----- //
// .preinit_array
FragmentRef* preinit_array = NULL;
if (file_format->hasPreInitArray()) {
preinit_array = FragmentRef::Create(
file_format->getPreInitArray().getSectionData()->front(), 0x0);
} else {
preinit_array = FragmentRef::Null();
}
f_pPreInitArrayStart =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__preinit_array_start",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
preinit_array, // FragRef
ResolveInfo::Hidden);
f_pPreInitArrayEnd =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__preinit_array_end",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Hidden);
// .init_array
FragmentRef* init_array = NULL;
if (file_format->hasInitArray()) {
init_array = FragmentRef::Create(
file_format->getInitArray().getSectionData()->front(), 0x0);
} else {
init_array = FragmentRef::Null();
}
f_pInitArrayStart =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__init_array_start",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
init_array, // FragRef
ResolveInfo::Hidden);
f_pInitArrayEnd =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__init_array_end",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
init_array, // FragRef
ResolveInfo::Hidden);
// .fini_array
FragmentRef* fini_array = NULL;
if (file_format->hasFiniArray()) {
fini_array = FragmentRef::Create(
file_format->getFiniArray().getSectionData()->front(), 0x0);
} else {
fini_array = FragmentRef::Null();
}
f_pFiniArrayStart =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__fini_array_start",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
fini_array, // FragRef
ResolveInfo::Hidden);
f_pFiniArrayEnd =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__fini_array_end",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
fini_array, // FragRef
ResolveInfo::Hidden);
// .stack
FragmentRef* stack = NULL;
if (file_format->hasStack()) {
stack = FragmentRef::Create(
file_format->getStack().getSectionData()->front(), 0x0);
} else {
stack = FragmentRef::Null();
}
f_pStack = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__stack",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Global,
0x0, // size
0x0, // value
stack, // FragRef
ResolveInfo::Hidden);
// _DYNAMIC
// TODO: add SectionData for .dynamic section, and then we can get the correct
// symbol section index for _DYNAMIC. Now it will be ABS.
f_pDynamic = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"_DYNAMIC",
ResolveInfo::Object,
ResolveInfo::Define,
ResolveInfo::Local,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Hidden);
// ----- segment symbols ----- //
f_pExecutableStart =
pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__executable_start",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
f_pEText = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"etext",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
f_p_EText = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"_etext",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
f_p__EText = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"__etext",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
f_pEData = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"edata",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
f_pEnd = pBuilder.AddSymbol<IRBuilder::AsReferred, IRBuilder::Resolve>(
"end",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
// _edata is defined forcefully.
f_p_EData = pBuilder.AddSymbol<IRBuilder::Force, IRBuilder::Resolve>(
"_edata",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
// __bss_start is defined forcefully.
f_pBSSStart = pBuilder.AddSymbol<IRBuilder::Force, IRBuilder::Resolve>(
"__bss_start",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
// _end is defined forcefully.
f_p_End = pBuilder.AddSymbol<IRBuilder::Force, IRBuilder::Resolve>(
"_end",
ResolveInfo::NoType,
ResolveInfo::Define,
ResolveInfo::Absolute,
0x0, // size
0x0, // value
FragmentRef::Null(), // FragRef
ResolveInfo::Default);
return true;
}
bool GNULDBackend::finalizeStandardSymbols() {
if (LinkerConfig::Object == config().codeGenType())
return true;
ELFFileFormat* file_format = getOutputFormat();
// ----- section symbols ----- //
if (f_pPreInitArrayStart != NULL) {
if (!f_pPreInitArrayStart->hasFragRef()) {
f_pPreInitArrayStart->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pPreInitArrayStart->setValue(0x0);
}
}
if (f_pPreInitArrayEnd != NULL) {
if (f_pPreInitArrayEnd->hasFragRef()) {
f_pPreInitArrayEnd->setValue(f_pPreInitArrayEnd->value() +
file_format->getPreInitArray().size());
} else {
f_pPreInitArrayEnd->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pPreInitArrayEnd->setValue(0x0);
}
}
if (f_pInitArrayStart != NULL) {
if (!f_pInitArrayStart->hasFragRef()) {
f_pInitArrayStart->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pInitArrayStart->setValue(0x0);
}
}
if (f_pInitArrayEnd != NULL) {
if (f_pInitArrayEnd->hasFragRef()) {
f_pInitArrayEnd->setValue(f_pInitArrayEnd->value() +
file_format->getInitArray().size());
} else {
f_pInitArrayEnd->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pInitArrayEnd->setValue(0x0);
}
}
if (f_pFiniArrayStart != NULL) {
if (!f_pFiniArrayStart->hasFragRef()) {
f_pFiniArrayStart->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pFiniArrayStart->setValue(0x0);
}
}
if (f_pFiniArrayEnd != NULL) {
if (f_pFiniArrayEnd->hasFragRef()) {
f_pFiniArrayEnd->setValue(f_pFiniArrayEnd->value() +
file_format->getFiniArray().size());
} else {
f_pFiniArrayEnd->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pFiniArrayEnd->setValue(0x0);
}
}
if (f_pStack != NULL) {
if (!f_pStack->hasFragRef()) {
f_pStack->resolveInfo()->setBinding(ResolveInfo::Absolute);
f_pStack->setValue(0x0);
}
}
if (f_pDynamic != NULL) {
f_pDynamic->resolveInfo()->setBinding(ResolveInfo::Local);
f_pDynamic->setValue(file_format->getDynamic().addr());
f_pDynamic->setSize(file_format->getDynamic().size());
}
// ----- segment symbols ----- //
if (f_pExecutableStart != NULL) {
ELFSegmentFactory::const_iterator exec_start =
elfSegmentTable().find(llvm::ELF::PT_LOAD, 0x0, 0x0);
if (elfSegmentTable().end() != exec_start) {
if (ResolveInfo::ThreadLocal != f_pExecutableStart->type()) {
f_pExecutableStart->setValue(f_pExecutableStart->value() +
(*exec_start)->vaddr());
}
} else {
f_pExecutableStart->setValue(0x0);
}
}
if (f_pEText != NULL || f_p_EText != NULL || f_p__EText != NULL) {
ELFSegmentFactory::const_iterator etext = elfSegmentTable().find(
llvm::ELF::PT_LOAD, llvm::ELF::PF_X, llvm::ELF::PF_W);
if (elfSegmentTable().end() != etext) {
if (f_pEText != NULL && ResolveInfo::ThreadLocal != f_pEText->type()) {
f_pEText->setValue(f_pEText->value() + (*etext)->vaddr() +
(*etext)->memsz());
}
if (f_p_EText != NULL && ResolveInfo::ThreadLocal != f_p_EText->type()) {
f_p_EText->setValue(f_p_EText->value() + (*etext)->vaddr() +
(*etext)->memsz());
}
if (f_p__EText != NULL &&
ResolveInfo::ThreadLocal != f_p__EText->type()) {
f_p__EText->setValue(f_p__EText->value() + (*etext)->vaddr() +
(*etext)->memsz());
}
} else {
if (f_pEText != NULL)
f_pEText->setValue(0x0);
if (f_p_EText != NULL)
f_p_EText->setValue(0x0);
if (f_p__EText != NULL)
f_p__EText->setValue(0x0);
}
}
if (f_pEData != NULL || f_p_EData != NULL || f_pBSSStart != NULL ||
f_pEnd != NULL || f_p_End != NULL) {
ELFSegmentFactory::const_iterator edata =
elfSegmentTable().find(llvm::ELF::PT_LOAD, llvm::ELF::PF_W, 0x0);
if (elfSegmentTable().end() != edata) {
if (f_pEData != NULL && ResolveInfo::ThreadLocal != f_pEData->type()) {
f_pEData->setValue(f_pEData->value() + (*edata)->vaddr() +
(*edata)->filesz());
}
if (f_p_EData != NULL && ResolveInfo::ThreadLocal != f_p_EData->type()) {
f_p_EData->setValue(f_p_EData->value() + (*edata)->vaddr() +
(*edata)->filesz());
}
if (f_pBSSStart != NULL &&
ResolveInfo::ThreadLocal != f_pBSSStart->type()) {
f_pBSSStart->setValue(f_pBSSStart->value() + (*edata)->vaddr() +
(*edata)->filesz());
}
if (f_pEnd != NULL && ResolveInfo::ThreadLocal != f_pEnd->type()) {
f_pEnd->setValue(f_pEnd->value() + (*edata)->vaddr() +
(*edata)->memsz());
}
if (f_p_End != NULL && ResolveInfo::ThreadLocal != f_p_End->type()) {
f_p_End->setValue(f_p_End->value() + (*edata)->vaddr() +
(*edata)->memsz());
}
} else {
if (f_pEData != NULL)
f_pEData->setValue(0x0);
if (f_p_EData != NULL)
f_p_EData->setValue(0x0);
if (f_pBSSStart != NULL)
f_pBSSStart->setValue(0x0);
if (f_pEnd != NULL)
f_pEnd->setValue(0x0);
if (f_p_End != NULL)
f_p_End->setValue(0x0);
}
}
return true;
}
bool GNULDBackend::finalizeTLSSymbol(LDSymbol& pSymbol) {
// ignore if symbol has no fragRef
if (!pSymbol.hasFragRef())
return true;
// the value of a TLS symbol is the offset to the TLS segment
ELFSegmentFactory::iterator tls_seg =
elfSegmentTable().find(llvm::ELF::PT_TLS, llvm::ELF::PF_R, 0x0);
assert(tls_seg != elfSegmentTable().end());
uint64_t value = pSymbol.fragRef()->getOutputOffset();
uint64_t addr = pSymbol.fragRef()->frag()->getParent()->getSection().addr();
pSymbol.setValue(value + addr - (*tls_seg)->vaddr());
return true;
}
ELFFileFormat* GNULDBackend::getOutputFormat() {
switch (config().codeGenType()) {
case LinkerConfig::DynObj:
assert(m_pDynObjFileFormat != NULL);
return m_pDynObjFileFormat;
case LinkerConfig::Exec:
case LinkerConfig::Binary:
assert(m_pExecFileFormat != NULL);
return m_pExecFileFormat;
case LinkerConfig::Object:
assert(m_pObjectFileFormat != NULL);
return m_pObjectFileFormat;
default:
fatal(diag::unrecognized_output_file) << config().codeGenType();
return NULL;
}
}
const ELFFileFormat* GNULDBackend::getOutputFormat() const {
switch (config().codeGenType()) {
case LinkerConfig::DynObj:
assert(m_pDynObjFileFormat != NULL);
return m_pDynObjFileFormat;
case LinkerConfig::Exec:
case LinkerConfig::Binary:
assert(m_pExecFileFormat != NULL);
return m_pExecFileFormat;
case LinkerConfig::Object:
assert(m_pObjectFileFormat != NULL);
return m_pObjectFileFormat;
default:
fatal(diag::unrecognized_output_file) << config().codeGenType();
return NULL;
}
}
/// sizeShstrtab - compute the size of .shstrtab
void GNULDBackend::sizeShstrtab(Module& pModule) {
size_t shstrtab = 0;
// compute the size of .shstrtab section.
Module::const_iterator sect, sectEnd = pModule.end();
for (sect = pModule.begin(); sect != sectEnd; ++sect) {
shstrtab += (*sect)->name().size() + 1;
} // end of for
getOutputFormat()->getShStrTab().setSize(shstrtab);
}
/// sizeNamePools - compute the size of regular name pools
/// In ELF executable files, regular name pools are .symtab, .strtab,
/// .dynsym, .dynstr, .hash and .shstrtab.
void GNULDBackend::sizeNamePools(Module& pModule) {
assert(LinkerConfig::Unset != config().codePosition());
// number of entries in symbol tables starts from 1 to hold the special entry
// at index 0 (STN_UNDEF). See ELF Spec Book I, p1-21.
size_t symtab = 1;
size_t dynsym = config().isCodeStatic() ? 0 : 1;
// size of string tables starts from 1 to hold the null character in their
// first byte
size_t strtab = 1;
size_t dynstr = config().isCodeStatic() ? 0 : 1;
size_t hash = 0;
size_t gnuhash = 0;
// number of local symbol in the .symtab and .dynsym
size_t symtab_local_cnt = 0;
size_t dynsym_local_cnt = 0;
Module::SymbolTable& symbols = pModule.getSymbolTable();
Module::const_sym_iterator symbol, symEnd;
/// Compute the size of .symtab, .strtab, and symtab_local_cnt
/// @{
/* TODO:
1. discard locals and temporary locals
2. check whether the symbol is used
*/
switch (config().options().getStripSymbolMode()) {
case GeneralOptions::StripSymbolMode::StripAllSymbols: {
symtab = strtab = 0;
break;
}
default: {
symEnd = symbols.end();
for (symbol = symbols.begin(); symbol != symEnd; ++symbol) {
++symtab;
if (hasEntryInStrTab(**symbol))
strtab += (*symbol)->nameSize() + 1;
}
symtab_local_cnt = 1 + symbols.numOfFiles() + symbols.numOfLocals() +
symbols.numOfLocalDyns();
break;
}
} // end of switch
ELFFileFormat* file_format = getOutputFormat();
switch (config().codeGenType()) {
case LinkerConfig::DynObj: {
// soname
dynstr += config().options().soname().size() + 1;
}
/** fall through **/
case LinkerConfig::Exec:
case LinkerConfig::Binary: {
if (!config().isCodeStatic()) {
/// Compute the size of .dynsym, .dynstr, and dynsym_local_cnt
symEnd = symbols.dynamicEnd();
for (symbol = symbols.localDynBegin(); symbol != symEnd; ++symbol) {
++dynsym;
if (hasEntryInStrTab(**symbol))
dynstr += (*symbol)->nameSize() + 1;
}
dynsym_local_cnt = 1 + symbols.numOfLocalDyns();
// compute .gnu.hash
if (config().options().hasGNUHash()) {
// count the number of dynsym to hash
size_t hashed_sym_cnt = 0;
symEnd = symbols.dynamicEnd();
for (symbol = symbols.dynamicBegin(); symbol != symEnd; ++symbol) {
if (DynsymCompare().needGNUHash(**symbol))
++hashed_sym_cnt;
}
// Special case for empty .dynsym
if (hashed_sym_cnt == 0)
gnuhash = 5 * 4 + config().targets().bitclass() / 8;
else {
size_t nbucket = getHashBucketCount(hashed_sym_cnt, true);
gnuhash = (4 + nbucket + hashed_sym_cnt) * 4;
gnuhash += (1U << getGNUHashMaskbitslog2(hashed_sym_cnt)) / 8;
}
}
// compute .hash
if (config().options().hasSysVHash()) {
// Both Elf32_Word and Elf64_Word are 4 bytes
hash = (2 + getHashBucketCount(dynsym, false) + dynsym) *
sizeof(llvm::ELF::Elf32_Word);
}
// add DT_NEEDED
Module::const_lib_iterator lib, libEnd = pModule.lib_end();
for (lib = pModule.lib_begin(); lib != libEnd; ++lib) {
if (!(*lib)->attribute()->isAsNeeded() || (*lib)->isNeeded()) {
dynstr += (*lib)->name().size() + 1;
dynamic().reserveNeedEntry();
}
}
// add DT_RPATH
if (!config().options().getRpathList().empty()) {
dynamic().reserveNeedEntry();
GeneralOptions::const_rpath_iterator rpath,
rpathEnd = config().options().rpath_end();
for (rpath = config().options().rpath_begin(); rpath != rpathEnd;
++rpath)
dynstr += (*rpath).size() + 1;
}
// set size
if (config().targets().is32Bits()) {
file_format->getDynSymTab().setSize(dynsym *
sizeof(llvm::ELF::Elf32_Sym));
} else {
file_format->getDynSymTab().setSize(dynsym *
sizeof(llvm::ELF::Elf64_Sym));
}
file_format->getDynStrTab().setSize(dynstr);
file_format->getHashTab().setSize(hash);
file_format->getGNUHashTab().setSize(gnuhash);
// set .dynsym sh_info to one greater than the symbol table
// index of the last local symbol
file_format->getDynSymTab().setInfo(dynsym_local_cnt);
// Because some entries in .dynamic section need information of .dynsym,
// .dynstr, .symtab, .strtab and .hash, we can not reserve non-DT_NEEDED
// entries until we get the size of the sections mentioned above
dynamic().reserveEntries(*file_format);
file_format->getDynamic().setSize(dynamic().numOfBytes());
}
}
/* fall through */
case LinkerConfig::Object: {
if (config().targets().is32Bits())
file_format->getSymTab().setSize(symtab * sizeof(llvm::ELF::Elf32_Sym));
else
file_format->getSymTab().setSize(symtab * sizeof(llvm::ELF::Elf64_Sym));
file_format->getStrTab().setSize(strtab);
// set .symtab sh_info to one greater than the symbol table
// index of the last local symbol
file_format->getSymTab().setInfo(symtab_local_cnt);
// The size of .shstrtab should be decided after output sections are all
// set, so we just set it to 1 here.
file_format->getShStrTab().setSize(0x1);
break;
}
default:
fatal(diag::fatal_illegal_codegen_type) << pModule.name();
break;
} // end of switch
}
/// emitSymbol32 - emit an ELF32 symbol
void GNULDBackend::emitSymbol32(llvm::ELF::Elf32_Sym& pSym,
LDSymbol& pSymbol,
char* pStrtab,
size_t pStrtabsize,
size_t pSymtabIdx) {
// FIXME: check the endian between host and target
// write out symbol
if (hasEntryInStrTab(pSymbol)) {
pSym.st_name = pStrtabsize;
::memcpy((pStrtab + pStrtabsize), pSymbol.name(), pSymbol.nameSize());
} else {
pSym.st_name = 0;
}
pSym.st_value = pSymbol.value();
pSym.st_size = getSymbolSize(pSymbol);
pSym.st_info = getSymbolInfo(pSymbol);
pSym.st_other = pSymbol.visibility();
pSym.st_shndx = getSymbolShndx(pSymbol);
}
/// emitSymbol64 - emit an ELF64 symbol
void GNULDBackend::emitSymbol64(llvm::ELF::Elf64_Sym& pSym,
LDSymbol& pSymbol,
char* pStrtab,
size_t pStrtabsize,
size_t pSymtabIdx) {
// FIXME: check the endian between host and target
// write out symbol
if (hasEntryInStrTab(pSymbol)) {
pSym.st_name = pStrtabsize;
::memcpy((pStrtab + pStrtabsize), pSymbol.name(), pSymbol.nameSize());
} else {
pSym.st_name = 0;
}
pSym.st_value = pSymbol.value();
pSym.st_size = getSymbolSize(pSymbol);
pSym.st_info = getSymbolInfo(pSymbol);
pSym.st_other = pSymbol.visibility();
pSym.st_shndx = getSymbolShndx(pSymbol);
}
/// emitRegNamePools - emit regular name pools - .symtab, .strtab
///
/// the size of these tables should be computed before layout
/// layout should computes the start offset of these tables
void GNULDBackend::emitRegNamePools(const Module& pModule,
FileOutputBuffer& pOutput) {
ELFFileFormat* file_format = getOutputFormat();
if (!file_format->hasSymTab())
return;
LDSection& symtab_sect = file_format->getSymTab();
LDSection& strtab_sect = file_format->getStrTab();
MemoryRegion symtab_region =
pOutput.request(symtab_sect.offset(), symtab_sect.size());
MemoryRegion strtab_region =
pOutput.request(strtab_sect.offset(), strtab_sect.size());
// set up symtab_region
llvm::ELF::Elf32_Sym* symtab32 = NULL;
llvm::ELF::Elf64_Sym* symtab64 = NULL;
if (config().targets().is32Bits())
symtab32 = (llvm::ELF::Elf32_Sym*)symtab_region.begin();
else if (config().targets().is64Bits())
symtab64 = (llvm::ELF::Elf64_Sym*)symtab_region.begin();
else {
fatal(diag::unsupported_bitclass) << config().targets().triple().str()
<< config().targets().bitclass();
}
// set up strtab_region
char* strtab = reinterpret_cast<char*>(strtab_region.begin());
// emit the first ELF symbol
if (config().targets().is32Bits())
emitSymbol32(symtab32[0], *LDSymbol::Null(), strtab, 0, 0);
else
emitSymbol64(symtab64[0], *LDSymbol::Null(), strtab, 0, 0);
bool sym_exist = false;
HashTableType::entry_type* entry = NULL;
if (LinkerConfig::Object == config().codeGenType()) {
entry = m_pSymIndexMap->insert(LDSymbol::Null(), sym_exist);
entry->setValue(0);
}
size_t symIdx = 1;
size_t strtabsize = 1;
const Module::SymbolTable& symbols = pModule.getSymbolTable();
Module::const_sym_iterator symbol, symEnd;
symEnd = symbols.end();
for (symbol = symbols.begin(); symbol != symEnd; ++symbol) {
if (LinkerConfig::Object == config().codeGenType()) {
entry = m_pSymIndexMap->insert(*symbol, sym_exist);
entry->setValue(symIdx);
}
if (config().targets().is32Bits())
emitSymbol32(symtab32[symIdx], **symbol, strtab, strtabsize, symIdx);
else
emitSymbol64(symtab64[symIdx], **symbol, strtab, strtabsize, symIdx);
++symIdx;
if (hasEntryInStrTab(**symbol))
strtabsize += (*symbol)->nameSize() + 1;
}
}
/// emitDynNamePools - emit dynamic name pools - .dyntab, .dynstr, .hash
///
/// the size of these tables should be computed before layout
/// layout should computes the start offset of these tables
void GNULDBackend::emitDynNamePools(Module& pModule,
FileOutputBuffer& pOutput) {
ELFFileFormat* file_format = getOutputFormat();
if (!file_format->hasDynSymTab() || !file_format->hasDynStrTab() ||
!file_format->hasDynamic())
return;
bool sym_exist = false;
HashTableType::entry_type* entry = 0;
LDSection& symtab_sect = file_format->getDynSymTab();
LDSection& strtab_sect = file_format->getDynStrTab();
LDSection& dyn_sect = file_format->getDynamic();
MemoryRegion symtab_region =
pOutput.request(symtab_sect.offset(), symtab_sect.size());
MemoryRegion strtab_region =
pOutput.request(strtab_sect.offset(), strtab_sect.size());
MemoryRegion dyn_region = pOutput.request(dyn_sect.offset(), dyn_sect.size());
// set up symtab_region
llvm::ELF::Elf32_Sym* symtab32 = NULL;
llvm::ELF::Elf64_Sym* symtab64 = NULL;
if (config().targets().is32Bits())
symtab32 = (llvm::ELF::Elf32_Sym*)symtab_region.begin();
else if (config().targets().is64Bits())
symtab64 = (llvm::ELF::Elf64_Sym*)symtab_region.begin();
else {
fatal(diag::unsupported_bitclass) << config().targets().triple().str()
<< config().targets().bitclass();
}
// set up strtab_region
char* strtab = reinterpret_cast<char*>(strtab_region.begin());
// emit the first ELF symbol
if (config().targets().is32Bits())
emitSymbol32(symtab32[0], *LDSymbol::Null(), strtab, 0, 0);
else
emitSymbol64(symtab64[0], *LDSymbol::Null(), strtab, 0, 0);
size_t symIdx = 1;
size_t strtabsize = 1;
Module::SymbolTable& symbols = pModule.getSymbolTable();
// emit .gnu.hash
if (config().options().hasGNUHash())
emitGNUHashTab(symbols, pOutput);
// emit .hash
if (config().options().hasSysVHash())
emitELFHashTab(symbols, pOutput);
// emit .dynsym, and .dynstr (emit LocalDyn and Dynamic category)
Module::const_sym_iterator symbol, symEnd = symbols.dynamicEnd();
for (symbol = symbols.localDynBegin(); symbol != symEnd; ++symbol) {
if (config().targets().is32Bits())
emitSymbol32(symtab32[symIdx], **symbol, strtab, strtabsize, symIdx);
else
emitSymbol64(symtab64[symIdx], **symbol, strtab, strtabsize, symIdx);
// maintain output's symbol and index map
entry = m_pSymIndexMap->insert(*symbol, sym_exist);
entry->setValue(symIdx);
// sum up counters
++symIdx;
if (hasEntryInStrTab(**symbol))
strtabsize += (*symbol)->nameSize() + 1;
}
// emit DT_NEED
// add DT_NEED strings into .dynstr
ELFDynamic::iterator dt_need = dynamic().needBegin();
Module::const_lib_iterator lib, libEnd = pModule.lib_end();
for (lib = pModule.lib_begin(); lib != libEnd; ++lib) {
if (!(*lib)->attribute()->isAsNeeded() || (*lib)->isNeeded()) {
::memcpy((strtab + strtabsize),
(*lib)->name().c_str(),
(*lib)->name().size());
(*dt_need)->setValue(llvm::ELF::DT_NEEDED, strtabsize);
strtabsize += (*lib)->name().size() + 1;
++dt_need;
}
}
if (!config().options().getRpathList().empty()) {
if (!config().options().hasNewDTags())
(*dt_need)->setValue(llvm::ELF::DT_RPATH, strtabsize);
else
(*dt_need)->setValue(llvm::ELF::DT_RUNPATH, strtabsize);
++dt_need;
GeneralOptions::const_rpath_iterator rpath,
rpathEnd = config().options().rpath_end();
for (rpath = config().options().rpath_begin(); rpath != rpathEnd; ++rpath) {
memcpy((strtab + strtabsize), (*rpath).data(), (*rpath).size());
strtabsize += (*rpath).size();
strtab[strtabsize++] = (rpath + 1 == rpathEnd ? '\0' : ':');
}
}
// initialize value of ELF .dynamic section
if (LinkerConfig::DynObj == config().codeGenType()) {
// set pointer to SONAME entry in dynamic string table.
dynamic().applySoname(strtabsize);
}
dynamic().applyEntries(*file_format);
dynamic().emit(dyn_sect, dyn_region);
// emit soname
if (LinkerConfig::DynObj == config().codeGenType()) {
::memcpy((strtab + strtabsize),
config().options().soname().c_str(),
config().options().soname().size());
strtabsize += config().options().soname().size() + 1;
}
}
/// emitELFHashTab - emit .hash
void GNULDBackend::emitELFHashTab(const Module::SymbolTable& pSymtab,
FileOutputBuffer& pOutput) {
ELFFileFormat* file_format = getOutputFormat();
if (!file_format->hasHashTab())
return;
LDSection& hash_sect = file_format->getHashTab();
MemoryRegion hash_region =
pOutput.request(hash_sect.offset(), hash_sect.size());
// both 32 and 64 bits hash table use 32-bit entry
// set up hash_region
uint32_t* word_array = reinterpret_cast<uint32_t*>(hash_region.begin());
uint32_t& nbucket = word_array[0];
uint32_t& nchain = word_array[1];
size_t dynsymSize = 1 + pSymtab.numOfLocalDyns() + pSymtab.numOfDynamics();
nbucket = getHashBucketCount(dynsymSize, false);
nchain = dynsymSize;
uint32_t* bucket = (word_array + 2);
uint32_t* chain = (bucket + nbucket);
// initialize bucket
memset(reinterpret_cast<void*>(bucket), 0, nbucket);
hash::StringHash<hash::ELF> hash_func;
size_t idx = 1;
Module::const_sym_iterator symbol, symEnd = pSymtab.dynamicEnd();
for (symbol = pSymtab.localDynBegin(); symbol != symEnd; ++symbol) {
llvm::StringRef name((*symbol)->name());
size_t bucket_pos = hash_func(name) % nbucket;
chain[idx] = bucket[bucket_pos];
bucket[bucket_pos] = idx;
++idx;
}
}
/// emitGNUHashTab - emit .gnu.hash
void GNULDBackend::emitGNUHashTab(Module::SymbolTable& pSymtab,
FileOutputBuffer& pOutput) {
ELFFileFormat* file_format = getOutputFormat();
if (!file_format->hasGNUHashTab())
return;
MemoryRegion gnuhash_region =
pOutput.request(file_format->getGNUHashTab().offset(),
file_format->getGNUHashTab().size());
uint32_t* word_array = reinterpret_cast<uint32_t*>(gnuhash_region.begin());
// fixed-length fields
uint32_t& nbucket = word_array[0];
uint32_t& symidx = word_array[1];
uint32_t& maskwords = word_array[2];
uint32_t& shift2 = word_array[3];
// variable-length fields
uint8_t* bitmask = reinterpret_cast<uint8_t*>(word_array + 4);
uint32_t* bucket = NULL;
uint32_t* chain = NULL;
// count the number of dynsym to hash
size_t unhashed_sym_cnt = pSymtab.numOfLocalDyns();
size_t hashed_sym_cnt = pSymtab.numOfDynamics();
Module::const_sym_iterator symbol, symEnd = pSymtab.dynamicEnd();
for (symbol = pSymtab.dynamicBegin(); symbol != symEnd; ++symbol) {
if (DynsymCompare().needGNUHash(**symbol))
break;
++unhashed_sym_cnt;
--hashed_sym_cnt;
}
// special case for the empty hash table
if (hashed_sym_cnt == 0) {
nbucket = 1; // one empty bucket
symidx = 1 + unhashed_sym_cnt; // symidx above unhashed symbols
maskwords = 1; // bitmask length
shift2 = 0; // bloom filter
if (config().targets().is32Bits()) {
uint32_t* maskval = reinterpret_cast<uint32_t*>(bitmask);
*maskval = 0; // no valid hashes
} else {
// must be 64
uint64_t* maskval = reinterpret_cast<uint64_t*>(bitmask);
*maskval = 0; // no valid hashes
}
bucket = reinterpret_cast<uint32_t*>(bitmask +
config().targets().bitclass() / 8);
*bucket = 0; // no hash in the only bucket
return;
}
uint32_t maskbitslog2 = getGNUHashMaskbitslog2(hashed_sym_cnt);
uint32_t maskbits = 1u << maskbitslog2;
uint32_t shift1 = config().targets().is32Bits() ? 5 : 6;
uint32_t mask = (1u << shift1) - 1;
nbucket = getHashBucketCount(hashed_sym_cnt, true);
symidx = 1 + unhashed_sym_cnt;
maskwords = 1 << (maskbitslog2 - shift1);
shift2 = maskbitslog2;
// setup bucket and chain
bucket = reinterpret_cast<uint32_t*>(bitmask + maskbits / 8);
chain = (bucket + nbucket);
// build the gnu style hash table
typedef std::multimap<uint32_t, std::pair<LDSymbol*, uint32_t> > SymMapType;
SymMapType symmap;
symEnd = pSymtab.dynamicEnd();
for (symbol = pSymtab.localDynBegin() + symidx - 1; symbol != symEnd;
++symbol) {
hash::StringHash<hash::DJB> hasher;
uint32_t djbhash = hasher((*symbol)->name());
uint32_t hash = djbhash % nbucket;
symmap.insert(std::make_pair(hash, std::make_pair(*symbol, djbhash)));
}
// compute bucket, chain, and bitmask
std::vector<uint64_t> bitmasks(maskwords);
size_t hashedidx = symidx;
for (size_t idx = 0; idx < nbucket; ++idx) {
size_t count = 0;
std::pair<SymMapType::iterator, SymMapType::iterator> ret;
ret = symmap.equal_range(idx);
for (SymMapType::iterator it = ret.first; it != ret.second;) {
// rearrange the hashed symbol ordering
*(pSymtab.localDynBegin() + hashedidx - 1) = it->second.first;
uint32_t djbhash = it->second.second;
uint32_t val = ((djbhash >> shift1) & ((maskbits >> shift1) - 1));
bitmasks[val] |= 1u << (djbhash & mask);
bitmasks[val] |= 1u << ((djbhash >> shift2) & mask);
val = djbhash & ~1u;
// advance the iterator and check if we're dealing w/ the last elment
if (++it == ret.second) {
// last element terminates the chain
val |= 1;
}
chain[hashedidx - symidx] = val;
++hashedidx;
++count;
}
if (count == 0)
bucket[idx] = 0;
else
bucket[idx] = hashedidx - count;
}
// write the bitmasks
if (config().targets().is32Bits()) {
uint32_t* maskval = reinterpret_cast<uint32_t*>(bitmask);
for (size_t i = 0; i < maskwords; ++i)
std::memcpy(maskval + i, &bitmasks[i], 4);
} else {
// must be 64
uint64_t* maskval = reinterpret_cast<uint64_t*>(bitmask);
for (size_t i = 0; i < maskwords; ++i)
std::memcpy(maskval + i, &bitmasks[i], 8);
}
}
/// sizeInterp - compute the size of the .interp section
void GNULDBackend::sizeInterp() {
const char* dyld_name;
if (config().options().hasDyld())
dyld_name = config().options().dyld().c_str();
else
dyld_name = m_pInfo->dyld();
LDSection& interp = getOutputFormat()->getInterp();
interp.setSize(std::strlen(dyld_name) + 1);
}
/// emitInterp - emit the .interp
void GNULDBackend::emitInterp(FileOutputBuffer& pOutput) {
if (getOutputFormat()->hasInterp()) {
const LDSection& interp = getOutputFormat()->getInterp();
MemoryRegion region = pOutput.request(interp.offset(), interp.size());
const char* dyld_name;
if (config().options().hasDyld())
dyld_name = config().options().dyld().c_str();
else
dyld_name = m_pInfo->dyld();
std::memcpy(region.begin(), dyld_name, interp.size());
}
}
bool GNULDBackend::hasEntryInStrTab(const LDSymbol& pSym) const {
return ResolveInfo::Section != pSym.type();
}
void GNULDBackend::orderSymbolTable(Module& pModule) {
Module::SymbolTable& symbols = pModule.getSymbolTable();
if (config().options().hasGNUHash()) {
// Currently we may add output symbols after sizeNamePools(), and a
// non-stable sort is used in SymbolCategory::arrange(), so we just
// sort .dynsym right before emitting .gnu.hash
std::stable_sort(
symbols.dynamicBegin(), symbols.dynamicEnd(), DynsymCompare());
}
}
/// getSectionOrder
unsigned int GNULDBackend::getSectionOrder(const LDSection& pSectHdr) const {
const ELFFileFormat* file_format = getOutputFormat();
// NULL section should be the "1st" section
if (LDFileFormat::Null == pSectHdr.kind())
return SHO_NULL;
if (&pSectHdr == &file_format->getStrTab())
return SHO_STRTAB;
// if the section is not ALLOC, lay it out until the last possible moment
if (0 == (pSectHdr.flag() & llvm::ELF::SHF_ALLOC))
return SHO_UNDEFINED;
bool is_write = (pSectHdr.flag() & llvm::ELF::SHF_WRITE) != 0;
bool is_exec = (pSectHdr.flag() & llvm::ELF::SHF_EXECINSTR) != 0;
// TODO: need to take care other possible output sections
switch (pSectHdr.kind()) {
case LDFileFormat::TEXT:
case LDFileFormat::DATA:
if (is_exec) {
if (&pSectHdr == &file_format->getInit())
return SHO_INIT;
if (&pSectHdr == &file_format->getFini())
return SHO_FINI;
return SHO_TEXT;
} else if (!is_write) {
return SHO_RO;
} else {
if (config().options().hasRelro()) {
if (&pSectHdr == &file_format->getPreInitArray() ||
&pSectHdr == &file_format->getInitArray() ||
&pSectHdr == &file_format->getFiniArray() ||
&pSectHdr == &file_format->getCtors() ||
&pSectHdr == &file_format->getDtors() ||
&pSectHdr == &file_format->getJCR() ||
&pSectHdr == &file_format->getDataRelRo())
return SHO_RELRO;
if (&pSectHdr == &file_format->getDataRelRoLocal())
return SHO_RELRO_LOCAL;
// Make special sections that end with .rel.ro suffix as RELRO.
llvm::StringRef name(pSectHdr.name());
if (name.endswith(".rel.ro")) {
return SHO_RELRO;
}
}
if ((pSectHdr.flag() & llvm::ELF::SHF_TLS) != 0x0) {
return SHO_TLS_DATA;
}
return SHO_DATA;
}
case LDFileFormat::BSS:
if ((pSectHdr.flag() & llvm::ELF::SHF_TLS) != 0x0)
return SHO_TLS_BSS;
return SHO_BSS;
case LDFileFormat::NamePool: {
if (&pSectHdr == &file_format->getDynamic())
return SHO_RELRO;
return SHO_NAMEPOOL;
}
case LDFileFormat::Relocation:
if (&pSectHdr == &file_format->getRelPlt() ||
&pSectHdr == &file_format->getRelaPlt())
return SHO_REL_PLT;
return SHO_RELOCATION;
// get the order from target for target specific sections
case LDFileFormat::Target:
return getTargetSectionOrder(pSectHdr);
// handle .interp and .note.* sections
case LDFileFormat::Note:
if (file_format->hasInterp() && (&pSectHdr == &file_format->getInterp()))
return SHO_INTERP;
else if (is_write)
return SHO_RW_NOTE;
else
return SHO_RO_NOTE;
case LDFileFormat::EhFrame:
// set writable .eh_frame as relro
if (is_write)
return SHO_RELRO;
case LDFileFormat::EhFrameHdr:
case LDFileFormat::GCCExceptTable:
return SHO_EXCEPTION;
case LDFileFormat::MetaData:
case LDFileFormat::Debug:
case LDFileFormat::DebugString:
default:
return SHO_UNDEFINED;
}
}
/// getSymbolSize
uint64_t GNULDBackend::getSymbolSize(const LDSymbol& pSymbol) const {
// undefined and dynamic symbols should have zero size.
if (pSymbol.isDyn() || pSymbol.desc() == ResolveInfo::Undefined)
return 0x0;
return pSymbol.resolveInfo()->size();
}
/// getSymbolInfo
uint64_t GNULDBackend::getSymbolInfo(const LDSymbol& pSymbol) const {
// set binding
uint8_t bind = 0x0;
if (pSymbol.resolveInfo()->isLocal())
bind = llvm::ELF::STB_LOCAL;
else if (pSymbol.resolveInfo()->isGlobal())
bind = llvm::ELF::STB_GLOBAL;
else if (pSymbol.resolveInfo()->isWeak())
bind = llvm::ELF::STB_WEAK;
else if (pSymbol.resolveInfo()->isAbsolute()) {
// (Luba) Is a absolute but not global (weak or local) symbol meaningful?
bind = llvm::ELF::STB_GLOBAL;
}
if (config().codeGenType() != LinkerConfig::Object &&
(pSymbol.visibility() == llvm::ELF::STV_INTERNAL ||
pSymbol.visibility() == llvm::ELF::STV_HIDDEN))
bind = llvm::ELF::STB_LOCAL;
uint32_t type = pSymbol.resolveInfo()->type();
// if the IndirectFunc symbol (i.e., STT_GNU_IFUNC) is from dynobj, change
// its type to Function
if (type == ResolveInfo::IndirectFunc && pSymbol.isDyn())
type = ResolveInfo::Function;
return (type | (bind << 4));
}
/// getSymbolValue - this function is called after layout()
uint64_t GNULDBackend::getSymbolValue(const LDSymbol& pSymbol) const {
if (pSymbol.isDyn())
return 0x0;
return pSymbol.value();
}
/// getSymbolShndx - this function is called after layout()
uint64_t GNULDBackend::getSymbolShndx(const LDSymbol& pSymbol) const {
if (pSymbol.resolveInfo()->isAbsolute())
return llvm::ELF::SHN_ABS;
if (pSymbol.resolveInfo()->isCommon())
return llvm::ELF::SHN_COMMON;
if (pSymbol.resolveInfo()->isUndef() || pSymbol.isDyn())
return llvm::ELF::SHN_UNDEF;
if (pSymbol.resolveInfo()->isDefine() && !pSymbol.hasFragRef())
return llvm::ELF::SHN_ABS;
assert(pSymbol.hasFragRef() &&
"symbols must have fragment reference to get its index");
return pSymbol.fragRef()->frag()->getParent()->getSection().index();
}
/// getSymbolIdx - called by emitRelocation to get the ouput symbol table index
size_t GNULDBackend::getSymbolIdx(const LDSymbol* pSymbol) const {
HashTableType::iterator entry =
m_pSymIndexMap->find(const_cast<LDSymbol*>(pSymbol));
assert(entry != m_pSymIndexMap->end() &&
"symbol not found in the symbol table");
return entry.getEntry()->value();
}
/// isTemporary - Whether pSymbol is a local label.
bool GNULDBackend::isTemporary(const LDSymbol& pSymbol) const {
if (ResolveInfo::Local != pSymbol.binding())
return false;
if (pSymbol.nameSize() < 2)
return false;
const char* name = pSymbol.name();
if ('.' == name[0] && 'L' == name[1])
return true;
// UnixWare 2.1 cc generate DWARF debugging symbols with `..' prefix.
if (name[0] == '.' && name[1] == '.')
return true;
// Work arround for gcc's bug
// gcc sometimes generate symbols with '_.L_' prefix.
if (pSymbol.nameSize() < 4)
return false;
if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_')
return true;
return false;
}
/// allocateCommonSymbols - allocate common symbols in the corresponding
/// sections. This is executed at pre-layout stage.
bool GNULDBackend::allocateCommonSymbols(Module& pModule) {
SymbolCategory& symbol_list = pModule.getSymbolTable();
if (symbol_list.emptyCommons() && symbol_list.emptyFiles() &&
symbol_list.emptyLocals() && symbol_list.emptyLocalDyns())
return true;
SymbolCategory::iterator com_sym, com_end;
// FIXME: If the order of common symbols is defined, then sort common symbols
// std::sort(com_sym, com_end, some kind of order);
// get corresponding BSS LDSection
ELFFileFormat* file_format = getOutputFormat();
LDSection& bss_sect = file_format->getBSS();
LDSection& tbss_sect = file_format->getTBSS();
// get or create corresponding BSS SectionData
SectionData* bss_sect_data = NULL;
if (bss_sect.hasSectionData())
bss_sect_data = bss_sect.getSectionData();
else
bss_sect_data = IRBuilder::CreateSectionData(bss_sect);
SectionData* tbss_sect_data = NULL;
if (tbss_sect.hasSectionData())
tbss_sect_data = tbss_sect.getSectionData();
else
tbss_sect_data = IRBuilder::CreateSectionData(tbss_sect);
// remember original BSS size
uint64_t bss_offset = bss_sect.size();
uint64_t tbss_offset = tbss_sect.size();
// allocate all local common symbols
com_end = symbol_list.localEnd();
for (com_sym = symbol_list.localBegin(); com_sym != com_end; ++com_sym) {
if (ResolveInfo::Common == (*com_sym)->desc()) {
// We have to reset the description of the symbol here. When doing
// incremental linking, the output relocatable object may have common
// symbols. Therefore, we can not treat common symbols as normal symbols
// when emitting the regular name pools. We must change the symbols'
// description here.
(*com_sym)->resolveInfo()->setDesc(ResolveInfo::Define);
Fragment* frag = new FillFragment(0x0, 1, (*com_sym)->size());
if (ResolveInfo::ThreadLocal == (*com_sym)->type()) {
// allocate TLS common symbol in tbss section
tbss_offset += ObjectBuilder::AppendFragment(
*frag, *tbss_sect_data, (*com_sym)->value());
ObjectBuilder::UpdateSectionAlign(tbss_sect, (*com_sym)->value());
(*com_sym)->setFragmentRef(FragmentRef::Create(*frag, 0));
} else {
bss_offset += ObjectBuilder::AppendFragment(
*frag, *bss_sect_data, (*com_sym)->value());
ObjectBuilder::UpdateSectionAlign(bss_sect, (*com_sym)->value());
(*com_sym)->setFragmentRef(FragmentRef::Create(*frag, 0));
}
}
}
// allocate all global common symbols
com_end = symbol_list.commonEnd();
for (com_sym = symbol_list.commonBegin(); com_sym != com_end; ++com_sym) {
// We have to reset the description of the symbol here. When doing
// incremental linking, the output relocatable object may have common
// symbols. Therefore, we can not treat common symbols as normal symbols
// when emitting the regular name pools. We must change the symbols'
// description here.
(*com_sym)->resolveInfo()->setDesc(ResolveInfo::Define);
Fragment* frag = new FillFragment(0x0, 1, (*com_sym)->size());
if (ResolveInfo::ThreadLocal == (*com_sym)->type()) {
// allocate TLS common symbol in tbss section
tbss_offset += ObjectBuilder::AppendFragment(
*frag, *tbss_sect_data, (*com_sym)->value());
ObjectBuilder::UpdateSectionAlign(tbss_sect, (*com_sym)->value());
(*com_sym)->setFragmentRef(FragmentRef::Create(*frag, 0));
} else {
bss_offset += ObjectBuilder::AppendFragment(
*frag, *bss_sect_data, (*com_sym)->value());
ObjectBuilder::UpdateSectionAlign(bss_sect, (*com_sym)->value());
(*com_sym)->setFragmentRef(FragmentRef::Create(*frag, 0));
}
}
bss_sect.setSize(bss_offset);
tbss_sect.setSize(tbss_offset);
symbol_list.changeCommonsToGlobal();
return true;
}
/// updateSectionFlags - update pTo's flags when merging pFrom
/// update the output section flags based on input section flags.
bool GNULDBackend::updateSectionFlags(LDSection& pTo, const LDSection& pFrom) {
// union the flags from input
uint32_t flags = pTo.flag();
flags |= (pFrom.flag() & (llvm::ELF::SHF_WRITE | llvm::ELF::SHF_ALLOC |
llvm::ELF::SHF_EXECINSTR));
// if there is an input section is not SHF_MERGE, clean this flag
if (0 == (pFrom.flag() & llvm::ELF::SHF_MERGE))
flags &= ~llvm::ELF::SHF_MERGE;
// if there is an input section is not SHF_STRINGS, clean this flag
if (0 == (pFrom.flag() & llvm::ELF::SHF_STRINGS))
flags &= ~llvm::ELF::SHF_STRINGS;
pTo.setFlag(flags);
return true;
}
/// readRelocation - read ELF32_Rel entry
bool GNULDBackend::readRelocation(const llvm::ELF::Elf32_Rel& pRel,
Relocation::Type& pType,
uint32_t& pSymIdx,
uint32_t& pOffset) const {
uint32_t r_info = 0x0;
if (llvm::sys::IsLittleEndianHost) {
pOffset = pRel.r_offset;
r_info = pRel.r_info;
} else {
pOffset = mcld::bswap32(pRel.r_offset);
r_info = mcld::bswap32(pRel.r_info);
}
pType = static_cast<unsigned char>(r_info);
pSymIdx = (r_info >> 8);
return true;
}
/// readRelocation - read ELF32_Rela entry
bool GNULDBackend::readRelocation(const llvm::ELF::Elf32_Rela& pRel,
Relocation::Type& pType,
uint32_t& pSymIdx,
uint32_t& pOffset,
int32_t& pAddend) const {
uint32_t r_info = 0x0;
if (llvm::sys::IsLittleEndianHost) {
pOffset = pRel.r_offset;
r_info = pRel.r_info;
pAddend = pRel.r_addend;
} else {
pOffset = mcld::bswap32(pRel.r_offset);
r_info = mcld::bswap32(pRel.r_info);
pAddend = mcld::bswap32(pRel.r_addend);
}
pType = static_cast<unsigned char>(r_info);
pSymIdx = (r_info >> 8);
return true;
}
/// readRelocation - read ELF64_Rel entry
bool GNULDBackend::readRelocation(const llvm::ELF::Elf64_Rel& pRel,
Relocation::Type& pType,
uint32_t& pSymIdx,
uint64_t& pOffset) const {
uint64_t r_info = 0x0;
if (llvm::sys::IsLittleEndianHost) {
pOffset = pRel.r_offset;
r_info = pRel.r_info;
} else {
pOffset = mcld::bswap64(pRel.r_offset);
r_info = mcld::bswap64(pRel.r_info);
}
pType = static_cast<uint32_t>(r_info);
pSymIdx = (r_info >> 32);
return true;
}
/// readRel - read ELF64_Rela entry
bool GNULDBackend::readRelocation(const llvm::ELF::Elf64_Rela& pRel,
Relocation::Type& pType,
uint32_t& pSymIdx,
uint64_t& pOffset,
int64_t& pAddend) const {
uint64_t r_info = 0x0;
if (llvm::sys::IsLittleEndianHost) {
pOffset = pRel.r_offset;
r_info = pRel.r_info;
pAddend = pRel.r_addend;
} else {
pOffset = mcld::bswap64(pRel.r_offset);
r_info = mcld::bswap64(pRel.r_info);
pAddend = mcld::bswap64(pRel.r_addend);
}
pType = static_cast<uint32_t>(r_info);
pSymIdx = (r_info >> 32);
return true;
}
/// emitRelocation - write data to the ELF32_Rel entry
void GNULDBackend::emitRelocation(llvm::ELF::Elf32_Rel& pRel,
Relocation::Type pType,
uint32_t pSymIdx,
uint32_t pOffset) const {
pRel.r_offset = pOffset;
pRel.setSymbolAndType(pSymIdx, pType);
}
/// emitRelocation - write data to the ELF32_Rela entry
void GNULDBackend::emitRelocation(llvm::ELF::Elf32_Rela& pRel,
Relocation::Type pType,
uint32_t pSymIdx,
uint32_t pOffset,
int32_t pAddend) const {
pRel.r_offset = pOffset;
pRel.r_addend = pAddend;
pRel.setSymbolAndType(pSymIdx, pType);
}
/// emitRelocation - write data to the ELF64_Rel entry
void GNULDBackend::emitRelocation(llvm::ELF::Elf64_Rel& pRel,
Relocation::Type pType,
uint32_t pSymIdx,
uint64_t pOffset) const {
pRel.r_offset = pOffset;
pRel.setSymbolAndType(pSymIdx, pType);
}
/// emitRelocation - write data to the ELF64_Rela entry
void GNULDBackend::emitRelocation(llvm::ELF::Elf64_Rela& pRel,
Relocation::Type pType,
uint32_t pSymIdx,
uint64_t pOffset,
int64_t pAddend) const {
pRel.r_offset = pOffset;
pRel.r_addend = pAddend;
pRel.setSymbolAndType(pSymIdx, pType);
}
/// createProgramHdrs - base on output sections to create the program headers
void GNULDBackend::createProgramHdrs(Module& pModule) {
ELFFileFormat* file_format = getOutputFormat();
// make PT_INTERP
if (file_format->hasInterp()) {
// make PT_PHDR
elfSegmentTable().produce(llvm::ELF::PT_PHDR);
ELFSegment* interp_seg = elfSegmentTable().produce(llvm::ELF::PT_INTERP);
interp_seg->append(&file_format->getInterp());
}
uint32_t cur_flag, prev_flag = 0x0;
ELFSegment* load_seg = NULL;
// make possible PT_LOAD segments
LinkerScript& ldscript = pModule.getScript();
LinkerScript::AddressMap::iterator addrEnd = ldscript.addressMap().end();
SectionMap::iterator out, prev, outBegin, outEnd;
outBegin = ldscript.sectionMap().begin();
outEnd = ldscript.sectionMap().end();
for (out = outBegin, prev = outEnd; out != outEnd; prev = out, ++out) {
LDSection* sect = (*out)->getSection();
if (0 == (sect->flag() & llvm::ELF::SHF_ALLOC) &&
LDFileFormat::Null != sect->kind())
break;
// bypass empty sections
if (!(*out)->hasContent() &&
(*out)->getSection()->kind() != LDFileFormat::Null)
continue;
cur_flag = getSegmentFlag(sect->flag());
bool createPT_LOAD = false;
if (LDFileFormat::Null == sect->kind()) {
// 1. create text segment
createPT_LOAD = true;
} else if (!config().options().omagic() &&
(prev_flag & llvm::ELF::PF_W) ^ (cur_flag & llvm::ELF::PF_W)) {
// 2. create data segment if w/o omagic set
createPT_LOAD = true;
} else if (sect->kind() == LDFileFormat::BSS && load_seg->isDataSegment() &&
addrEnd != ldscript.addressMap().find(".bss")) {
// 3. create bss segment if w/ -Tbss and there is a data segment
createPT_LOAD = true;
} else if ((sect != &(file_format->getText())) &&
(sect != &(file_format->getData())) &&
(sect != &(file_format->getBSS())) &&
(addrEnd != ldscript.addressMap().find(sect->name()))) {
// 4. create PT_LOAD for sections in address map except for text, data,
// and bss
createPT_LOAD = true;
} else if (LDFileFormat::Null == (*prev)->getSection()->kind() &&
!config().options().getScriptList().empty()) {
// 5. create PT_LOAD to hold NULL section if there is a default ldscript
createPT_LOAD = true;
}
if (createPT_LOAD) {
// create new PT_LOAD segment
load_seg = elfSegmentTable().produce(llvm::ELF::PT_LOAD, cur_flag);
if (!config().options().nmagic() && !config().options().omagic())
load_seg->setAlign(abiPageSize());
}
assert(load_seg != NULL);
load_seg->append(sect);
if (cur_flag != prev_flag)
load_seg->updateFlag(cur_flag);
prev_flag = cur_flag;
}
// make PT_DYNAMIC
if (file_format->hasDynamic()) {
ELFSegment* dyn_seg = elfSegmentTable().produce(
llvm::ELF::PT_DYNAMIC, llvm::ELF::PF_R | llvm::ELF::PF_W);
dyn_seg->append(&file_format->getDynamic());
}
if (config().options().hasRelro()) {
// make PT_GNU_RELRO
ELFSegment* relro_seg = elfSegmentTable().produce(llvm::ELF::PT_GNU_RELRO);
for (ELFSegmentFactory::iterator seg = elfSegmentTable().begin(),
segEnd = elfSegmentTable().end();
seg != segEnd;
++seg) {
if (llvm::ELF::PT_LOAD != (*seg)->type())
continue;
for (ELFSegment::iterator sect = (*seg)->begin(), sectEnd = (*seg)->end();
sect != sectEnd;
++sect) {
unsigned int order = getSectionOrder(**sect);
if (SHO_RELRO_LOCAL == order || SHO_RELRO == order ||
SHO_RELRO_LAST == order) {
relro_seg->append(*sect);
}
}
}
}
// make PT_GNU_EH_FRAME
if (file_format->hasEhFrameHdr()) {
ELFSegment* eh_seg = elfSegmentTable().produce(llvm::ELF::PT_GNU_EH_FRAME);
eh_seg->append(&file_format->getEhFrameHdr());
}
// make PT_TLS
if (file_format->hasTData() || file_format->hasTBSS()) {
ELFSegment* tls_seg = elfSegmentTable().produce(llvm::ELF::PT_TLS);
if (file_format->hasTData())
tls_seg->append(&file_format->getTData());
if (file_format->hasTBSS())
tls_seg->append(&file_format->getTBSS());
}
// make PT_GNU_STACK
if (file_format->hasStackNote()) {
uint32_t flag = getSegmentFlag(file_format->getStackNote().flag());
elfSegmentTable().produce(llvm::ELF::PT_GNU_STACK,
llvm::ELF::PF_R | llvm::ELF::PF_W | flag);
}
// make PT_NOTE
ELFSegment* note_seg = NULL;
prev_flag = 0x0;
Module::iterator sect, sectBegin, sectEnd;
sectBegin = pModule.begin();
sectEnd = pModule.end();
for (sect = sectBegin; sect != sectEnd; ++sect) {
if ((*sect)->type() != llvm::ELF::SHT_NOTE ||
((*sect)->flag() & llvm::ELF::SHF_ALLOC) == 0)
continue;
cur_flag = getSegmentFlag((*sect)->flag());
// we have different section orders for read-only and writable notes, so
// create 2 segments if needed.
if (note_seg == NULL ||
(cur_flag & llvm::ELF::PF_W) != (prev_flag & llvm::ELF::PF_W))
note_seg = elfSegmentTable().produce(llvm::ELF::PT_NOTE, cur_flag);
note_seg->append(*sect);
prev_flag = cur_flag;
}
// create target dependent segments
doCreateProgramHdrs(pModule);
}
/// setupProgramHdrs - set up the attributes of segments
void GNULDBackend::setupProgramHdrs(const LinkerScript& pScript) {
// update segment info
for (ELFSegmentFactory::iterator seg = elfSegmentTable().begin(),
segEnd = elfSegmentTable().end();
seg != segEnd;
++seg) {
// bypass if there is no section in this segment (e.g., PT_GNU_STACK)
if ((*seg)->size() == 0)
continue;
// bypass the PT_LOAD that only has NULL section now
if ((*seg)->type() == llvm::ELF::PT_LOAD &&
(*seg)->front()->kind() == LDFileFormat::Null && (*seg)->size() == 1)
continue;
(*seg)->setOffset((*seg)->front()->offset());
if ((*seg)->type() == llvm::ELF::PT_LOAD &&
(*seg)->front()->kind() == LDFileFormat::Null) {
const LDSection* second = *((*seg)->begin() + 1);
assert(second != NULL);
(*seg)->setVaddr(second->addr() - second->offset());
} else {
(*seg)->setVaddr((*seg)->front()->addr());
}
(*seg)->setPaddr((*seg)->vaddr());
ELFSegment::reverse_iterator sect, sectREnd = (*seg)->rend();
for (sect = (*seg)->rbegin(); sect != sectREnd; ++sect) {
if ((*sect)->kind() != LDFileFormat::BSS)
break;
}
if (sect != sectREnd) {
(*seg)->setFilesz((*sect)->offset() + (*sect)->size() - (*seg)->offset());
} else {
(*seg)->setFilesz(0x0);
}
(*seg)->setMemsz((*seg)->back()->addr() + (*seg)->back()->size() -
(*seg)->vaddr());
} // end of for
// handle the case if text segment only has NULL section
LDSection* null_sect = &getOutputFormat()->getNULLSection();
ELFSegmentFactory::iterator null_seg =
elfSegmentTable().find(llvm::ELF::PT_LOAD, null_sect);
if ((*null_seg)->size() == 1) {
// find 2nd PT_LOAD
ELFSegmentFactory::iterator seg, segEnd = elfSegmentTable().end();
for (seg = null_seg + 1; seg != segEnd; ++seg) {
if ((*seg)->type() == llvm::ELF::PT_LOAD)
break;
}
if (seg != segEnd) {
uint64_t addr = (*seg)->front()->addr() - (*seg)->front()->offset();
uint64_t size = sectionStartOffset();
if (addr + size == (*seg)->front()->addr()) {
// if there is no space between the 2 segments, we can merge them.
(*seg)->setOffset(0x0);
(*seg)->setVaddr(addr);
(*seg)->setPaddr(addr);
ELFSegment::iterator sect, sectEnd = (*seg)->end();
for (sect = (*seg)->begin(); sect != sectEnd; ++sect) {
if ((*sect)->kind() == LDFileFormat::BSS) {
--sect;
break;
}
}
if (sect == sectEnd) {
(*seg)->setFilesz((*seg)->back()->offset() + (*seg)->back()->size() -
(*seg)->offset());
} else if (*sect != (*seg)->front()) {
--sect;
(*seg)->setFilesz((*sect)->offset() + (*sect)->size() -
(*seg)->offset());
} else {
(*seg)->setFilesz(0x0);
}
(*seg)->setMemsz((*seg)->back()->addr() + (*seg)->back()->size() -
(*seg)->vaddr());
(*seg)->insert((*seg)->begin(), null_sect);
elfSegmentTable().erase(null_seg);
} else if (addr + size < (*seg)->vaddr()) {
(*null_seg)->setOffset(0x0);
(*null_seg)->setVaddr(addr);
(*null_seg)->setPaddr(addr);
(*null_seg)->setFilesz(size);
(*null_seg)->setMemsz(size);
} else {
// erase the non valid segment contains NULL.
elfSegmentTable().erase(null_seg);
}
}
}
// set up PT_PHDR
ELFSegmentFactory::iterator phdr =
elfSegmentTable().find(llvm::ELF::PT_PHDR, llvm::ELF::PF_R, 0x0);
if (phdr != elfSegmentTable().end()) {
ELFSegmentFactory::iterator null_seg =
elfSegmentTable().find(llvm::ELF::PT_LOAD, null_sect);
if (null_seg != elfSegmentTable().end()) {
uint64_t offset = 0x0, phdr_size = 0x0;
if (config().targets().is32Bits()) {
offset = sizeof(llvm::ELF::Elf32_Ehdr);
phdr_size = sizeof(llvm::ELF::Elf32_Phdr);
} else {
offset = sizeof(llvm::ELF::Elf64_Ehdr);
phdr_size = sizeof(llvm::ELF::Elf64_Phdr);
}
(*phdr)->setOffset(offset);
(*phdr)->setVaddr((*null_seg)->vaddr() + offset);
(*phdr)->setPaddr((*phdr)->vaddr());
(*phdr)->setFilesz(elfSegmentTable().size() * phdr_size);
(*phdr)->setMemsz(elfSegmentTable().size() * phdr_size);
(*phdr)->setAlign(config().targets().bitclass() / 8);
} else {
elfSegmentTable().erase(phdr);
}
}
}
/// getSegmentFlag - give a section flag and return the corresponding segment
/// flag
uint32_t GNULDBackend::getSegmentFlag(const uint32_t pSectionFlag) {
uint32_t flag = 0x0;
if ((pSectionFlag & llvm::ELF::SHF_ALLOC) != 0x0)
flag |= llvm::ELF::PF_R;
if ((pSectionFlag & llvm::ELF::SHF_WRITE) != 0x0)
flag |= llvm::ELF::PF_W;
if ((pSectionFlag & llvm::ELF::SHF_EXECINSTR) != 0x0)
flag |= llvm::ELF::PF_X;
return flag;
}
/// setupGNUStackInfo - setup the section flag of .note.GNU-stack in output
void GNULDBackend::setupGNUStackInfo(Module& pModule) {
uint32_t flag = 0x0;
if (config().options().hasStackSet()) {
// 1. check the command line option (-z execstack or -z noexecstack)
if (config().options().hasExecStack())
flag = llvm::ELF::SHF_EXECINSTR;
} else {
// 2. check the stack info from the input objects
// FIXME: since we alway emit .note.GNU-stack in output now, we may be able
// to check this from the output .note.GNU-stack directly after section
// merging is done
size_t object_count = 0, stack_note_count = 0;
Module::const_obj_iterator obj, objEnd = pModule.obj_end();
for (obj = pModule.obj_begin(); obj != objEnd; ++obj) {
++object_count;
const LDSection* sect = (*obj)->context()->getSection(".note.GNU-stack");
if (sect != NULL) {
++stack_note_count;
// 2.1 found a stack note that is set as executable
if (0 != (llvm::ELF::SHF_EXECINSTR & sect->flag())) {
flag = llvm::ELF::SHF_EXECINSTR;
break;
}
}
}
// 2.2 there are no stack note sections in all input objects
if (0 == stack_note_count)
return;
// 2.3 a special case. Use the target default to decide if the stack should
// be executable
if (llvm::ELF::SHF_EXECINSTR != flag && object_count != stack_note_count)
if (m_pInfo->isDefaultExecStack())
flag = llvm::ELF::SHF_EXECINSTR;
}
if (getOutputFormat()->hasStackNote()) {
getOutputFormat()->getStackNote().setFlag(flag);
}
}
/// setOutputSectionOffset - helper function to set output sections' offset.
void GNULDBackend::setOutputSectionOffset(Module& pModule) {
LinkerScript& script = pModule.getScript();
uint64_t offset = 0x0;
LDSection* cur = NULL;
LDSection* prev = NULL;
SectionMap::iterator out, outBegin, outEnd;
outBegin = script.sectionMap().begin();
outEnd = script.sectionMap().end();
for (out = outBegin; out != outEnd; ++out, prev = cur) {
cur = (*out)->getSection();
if (cur->kind() == LDFileFormat::Null) {
cur->setOffset(0x0);
continue;
}
switch (prev->kind()) {
case LDFileFormat::Null:
offset = sectionStartOffset();
break;
case LDFileFormat::BSS:
offset = prev->offset();
break;
default:
offset = prev->offset() + prev->size();
break;
}
alignAddress(offset, cur->align());
cur->setOffset(offset);
}
}
/// setOutputSectionAddress - helper function to set output sections' address.
void GNULDBackend::setOutputSectionAddress(Module& pModule) {
RpnEvaluator evaluator(pModule, *this);
LinkerScript& script = pModule.getScript();
uint64_t vma = 0x0, offset = 0x0;
LDSection* cur = NULL;
LDSection* prev = NULL;
LinkerScript::AddressMap::iterator addr, addrEnd = script.addressMap().end();
ELFSegmentFactory::iterator seg, segEnd = elfSegmentTable().end();
SectionMap::Output::dot_iterator dot;
SectionMap::iterator out, outBegin, outEnd;
outBegin = script.sectionMap().begin();
outEnd = script.sectionMap().end();
for (out = outBegin; out != outEnd; prev = cur, ++out) {
cur = (*out)->getSection();
if (cur->kind() == LDFileFormat::Null) {
cur->setOffset(0x0);
continue;
}
// process dot assignments between 2 output sections
for (SectionMap::Output::dot_iterator it = (*out)->dot_begin(),
ie = (*out)->dot_end();
it != ie;
++it) {
(*it).assign(evaluator);
}
seg = elfSegmentTable().find(llvm::ELF::PT_LOAD, cur);
if (seg != segEnd && cur == (*seg)->front()) {
if ((*seg)->isBssSegment())
addr = script.addressMap().find(".bss");
else if ((*seg)->isDataSegment())
addr = script.addressMap().find(".data");
else
addr = script.addressMap().find(cur->name());
} else
addr = addrEnd;
if (addr != addrEnd) {
// use address mapping in script options
vma = addr.getEntry()->value();
} else if ((*out)->prolog().hasVMA()) {
// use address from output section description
evaluator.eval((*out)->prolog().vma(), vma);
} else if ((dot = (*out)->find_last_explicit_dot()) != (*out)->dot_end()) {
// assign address based on `.' symbol in ldscript
vma = (*dot).symbol().value();
alignAddress(vma, cur->align());
} else {
if ((*out)->prolog().type() == OutputSectDesc::NOLOAD) {
vma = prev->addr() + prev->size();
} else if ((cur->flag() & llvm::ELF::SHF_ALLOC) != 0) {
if (prev->kind() == LDFileFormat::Null) {
// Let SECTIONS starts at 0 if we have a default ldscript but don't
// have any initial value (VMA or `.').
if (!config().options().getScriptList().empty())
vma = 0x0;
else
vma = getSegmentStartAddr(script) + sectionStartOffset();
} else {
if ((prev->kind() == LDFileFormat::BSS))
vma = prev->addr();
else
vma = prev->addr() + prev->size();
}
alignAddress(vma, cur->align());
if (config().options().getScriptList().empty()) {
if (seg != segEnd && cur == (*seg)->front()) {
// Try to align p_vaddr at page boundary if not in script options.
// To do so will add more padding in file, but can save one page
// at runtime.
// Avoid doing this optimization if -z relro is given, because there
// seems to be too many padding.
if (!config().options().hasRelro()) {
alignAddress(vma, (*seg)->align());
} else {
vma += abiPageSize();
}
}
}
} else {
vma = 0x0;
}
}
if (config().options().hasRelro()) {
// if -z relro is given, we need to adjust sections' offset again, and
// let PT_GNU_RELRO end on a abi page boundary
// check if current is the first non-relro section
SectionMap::iterator relro_last = out - 1;
if (relro_last != outEnd && (*relro_last)->order() <= SHO_RELRO_LAST &&
(*out)->order() > SHO_RELRO_LAST) {
// align the first non-relro section to page boundary
alignAddress(vma, abiPageSize());
// It seems that compiler think .got and .got.plt are continuous (w/o
// any padding between). If .got is the last section in PT_RELRO and
// it's not continuous to its next section (i.e. .got.plt), we need to
// add padding in front of .got instead.
// FIXME: Maybe we can handle this in a more general way.
LDSection& got = getOutputFormat()->getGOT();
if ((getSectionOrder(got) == SHO_RELRO_LAST) &&
(got.addr() + got.size() < vma)) {
uint64_t diff = vma - got.addr() - got.size();
got.setAddr(vma - got.size());
got.setOffset(got.offset() + diff);
}
}
} // end of if - for relro processing
cur->setAddr(vma);
switch (prev->kind()) {
case LDFileFormat::Null:
offset = sectionStartOffset();
break;
case LDFileFormat::BSS:
offset = prev->offset();
break;
default:
offset = prev->offset() + prev->size();
break;
}
alignAddress(offset, cur->align());
// in p75, http://www.sco.com/developers/devspecs/gabi41.pdf
// p_align: As "Program Loading" describes in this chapter of the
// processor supplement, loadable process segments must have congruent
// values for p_vaddr and p_offset, modulo the page size.
// FIXME: Now make all sh_addr and sh_offset are congruent, modulo the page
// size. Otherwise, old objcopy (e.g., binutils 2.17) may fail with our
// output!
if ((cur->flag() & llvm::ELF::SHF_ALLOC) != 0 &&
(vma & (abiPageSize() - 1)) != (offset & (abiPageSize() - 1))) {
uint64_t padding = abiPageSize() + (vma & (abiPageSize() - 1)) -
(offset & (abiPageSize() - 1));
offset += padding;
}
cur->setOffset(offset);
// process dot assignments in the output section
bool changed = false;
Fragment* invalid = NULL;
for (SectionMap::Output::iterator in = (*out)->begin(),
inEnd = (*out)->end();
in != inEnd;
++in) {
if (invalid != NULL && !(*in)->dotAssignments().empty()) {
while (invalid != (*in)->dotAssignments().front().first) {
Fragment* prev = invalid->getPrevNode();
invalid->setOffset(prev->getOffset() + prev->size());
invalid = invalid->getNextNode();
}
invalid = NULL;
}
for (SectionMap::Input::dot_iterator it = (*in)->dot_begin(),
ie = (*in)->dot_end();
it != ie;
++it) {
(*it).second.assign(evaluator);
if ((*it).first != NULL) {
uint64_t new_offset = (*it).second.symbol().value() - vma;
if (new_offset != (*it).first->getOffset()) {
(*it).first->setOffset(new_offset);
invalid = (*it).first->getNextNode();
changed = true;
}
}
} // for each dot assignment
} // for each input description
if (changed) {
while (invalid != NULL) {
Fragment* prev = invalid->getPrevNode();
invalid->setOffset(prev->getOffset() + prev->size());
invalid = invalid->getNextNode();
}
cur->setSize(cur->getSectionData()->back().getOffset() +
cur->getSectionData()->back().size());
}
} // for each output section description
}
/// placeOutputSections - place output sections based on SectionMap
void GNULDBackend::placeOutputSections(Module& pModule) {
typedef std::vector<LDSection*> Orphans;
Orphans orphans;
SectionMap& sectionMap = pModule.getScript().sectionMap();
for (Module::iterator it = pModule.begin(), ie = pModule.end(); it != ie;
++it) {
bool wanted = false;
switch ((*it)->kind()) {
// take NULL and StackNote directly
case LDFileFormat::Null:
case LDFileFormat::StackNote:
wanted = true;
break;
// ignore if section size is 0
case LDFileFormat::EhFrame:
if (((*it)->size() != 0) ||
((*it)->hasEhFrame() &&
config().codeGenType() == LinkerConfig::Object))
wanted = true;
break;
case LDFileFormat::Relocation:
if (((*it)->size() != 0) ||
((*it)->hasRelocData() &&
config().codeGenType() == LinkerConfig::Object))
wanted = true;
break;
case LDFileFormat::TEXT:
case LDFileFormat::DATA:
case LDFileFormat::Target:
case LDFileFormat::MetaData:
case LDFileFormat::BSS:
case LDFileFormat::Debug:
case LDFileFormat::DebugString:
case LDFileFormat::GCCExceptTable:
case LDFileFormat::Note:
case LDFileFormat::NamePool:
case LDFileFormat::EhFrameHdr:
if (((*it)->size() != 0) ||
((*it)->hasSectionData() &&
config().codeGenType() == LinkerConfig::Object))
wanted = true;
break;
case LDFileFormat::Group:
if (LinkerConfig::Object == config().codeGenType()) {
// TODO: support incremental linking
}
break;
case LDFileFormat::Version:
if ((*it)->size() != 0) {
wanted = true;
warning(diag::warn_unsupported_symbolic_versioning) << (*it)->name();
}
break;
default:
if ((*it)->size() != 0) {
error(diag::err_unsupported_section) << (*it)->name()
<< (*it)->kind();
}
break;
} // end of switch
if (wanted) {
SectionMap::iterator out, outBegin, outEnd;
outBegin = sectionMap.begin();
outEnd = sectionMap.end();
for (out = outBegin; out != outEnd; ++out) {
bool matched = false;
if ((*it)->name().compare((*out)->name()) == 0) {
switch ((*out)->prolog().constraint()) {
case OutputSectDesc::NO_CONSTRAINT:
matched = true;
break;
case OutputSectDesc::ONLY_IF_RO:
matched = ((*it)->flag() & llvm::ELF::SHF_WRITE) == 0;
break;
case OutputSectDesc::ONLY_IF_RW:
matched = ((*it)->flag() & llvm::ELF::SHF_WRITE) != 0;
break;
} // end of switch
if (matched)
break;
}
} // for each output section description
if (out != outEnd) {
// set up the section
(*out)->setSection(*it);
(*out)->setOrder(getSectionOrder(**it));
} else {
orphans.push_back(*it);
}
}
} // for each section in Module
// set up sections in SectionMap but do not exist at all.
uint32_t flag = 0x0;
unsigned int order = SHO_UNDEFINED;
OutputSectDesc::Type type = OutputSectDesc::LOAD;
for (SectionMap::reverse_iterator out = sectionMap.rbegin(),
outEnd = sectionMap.rend();
out != outEnd;
++out) {
if ((*out)->hasContent() ||
(*out)->getSection()->kind() == LDFileFormat::Null ||
(*out)->getSection()->kind() == LDFileFormat::StackNote) {
flag = (*out)->getSection()->flag();
order = (*out)->order();
type = (*out)->prolog().type();
} else {
(*out)->getSection()->setFlag(flag);
(*out)->setOrder(order);
(*out)->prolog().setType(type);
}
} // for each output section description
// place orphan sections
for (Orphans::iterator it = orphans.begin(), ie = orphans.end(); it != ie;
++it) {
size_t order = getSectionOrder(**it);
SectionMap::iterator out, outBegin, outEnd;
outBegin = sectionMap.begin();
outEnd = sectionMap.end();
if ((*it)->kind() == LDFileFormat::Null)
out = sectionMap.insert(outBegin, *it);
else {
for (out = outBegin; out != outEnd; ++out) {
if ((*out)->order() > order)
break;
}
out = sectionMap.insert(out, *it);
}
(*out)->setOrder(order);
} // for each orphan section
// sort output section orders if there is no default ldscript
if (config().options().getScriptList().empty()) {
std::stable_sort(
sectionMap.begin(), sectionMap.end(), SectionMap::SHOCompare());
}
// when section ordering is fixed, now we can make sure dot assignments are
// all set appropriately
sectionMap.fixupDotSymbols();
}
/// layout - layout method
void GNULDBackend::layout(Module& pModule) {
// 1. place output sections based on SectionMap from SECTIONS command
placeOutputSections(pModule);
// 2. update output sections in Module
SectionMap& sectionMap = pModule.getScript().sectionMap();
pModule.getSectionTable().clear();
for (SectionMap::iterator out = sectionMap.begin(), outEnd = sectionMap.end();
out != outEnd;
++out) {
if ((*out)->hasContent() ||
(*out)->getSection()->kind() == LDFileFormat::Null ||
(*out)->getSection()->kind() == LDFileFormat::StackNote ||
config().codeGenType() == LinkerConfig::Object) {
(*out)->getSection()->setIndex(pModule.size());
pModule.getSectionTable().push_back((*out)->getSection());
}
} // for each output section description
// 3. update the size of .shstrtab
sizeShstrtab(pModule);
// 4. create program headers
if (LinkerConfig::Object != config().codeGenType()) {
createProgramHdrs(pModule);
}
// 5. set output section address/offset
if (LinkerConfig::Object != config().codeGenType())
setOutputSectionAddress(pModule);
else
setOutputSectionOffset(pModule);
}
void GNULDBackend::createAndSizeEhFrameHdr(Module& pModule) {
if (LinkerConfig::Object != config().codeGenType() &&
config().options().hasEhFrameHdr() && getOutputFormat()->hasEhFrame()) {
// init EhFrameHdr and size the output section
ELFFileFormat* format = getOutputFormat();
m_pEhFrameHdr =
new EhFrameHdr(format->getEhFrameHdr(), format->getEhFrame());
m_pEhFrameHdr->sizeOutput();
}
}
/// mayHaveUnsafeFunctionPointerAccess - check if the section may have unsafe
/// function pointer access
bool GNULDBackend::mayHaveUnsafeFunctionPointerAccess(
const LDSection& pSection) const {
llvm::StringRef name(pSection.name());
return !name.startswith(".rodata._ZTV") &&
!name.startswith(".data.rel.ro._ZTV") &&
!name.startswith(".rodata._ZTC") &&
!name.startswith(".data.rel.ro._ZTC") && !name.startswith(".eh_frame");
}
/// preLayout - Backend can do any needed modification before layout
void GNULDBackend::preLayout(Module& pModule, IRBuilder& pBuilder) {
// prelayout target first
doPreLayout(pBuilder);
// change .tbss and .tdata section symbol from Local to LocalDyn category
if (f_pTDATA != NULL)
pModule.getSymbolTable().changeToDynamic(*f_pTDATA);
if (f_pTBSS != NULL)
pModule.getSymbolTable().changeToDynamic(*f_pTBSS);
// To merge input's relocation sections into output's relocation sections.
//
// If we are generating relocatables (-r), move input relocation sections
// to corresponding output relocation sections.
if (LinkerConfig::Object == config().codeGenType()) {
Module::obj_iterator input, inEnd = pModule.obj_end();
for (input = pModule.obj_begin(); input != inEnd; ++input) {
LDContext::sect_iterator rs, rsEnd = (*input)->context()->relocSectEnd();
for (rs = (*input)->context()->relocSectBegin(); rs != rsEnd; ++rs) {
// get the output relocation LDSection with identical name.
LDSection* output_sect = pModule.getSection((*rs)->name());
if (output_sect == NULL) {
output_sect = LDSection::Create(
(*rs)->name(), (*rs)->kind(), (*rs)->type(), (*rs)->flag());
output_sect->setAlign((*rs)->align());
pModule.getSectionTable().push_back(output_sect);
}
// set output relocation section link
const LDSection* input_link = (*rs)->getLink();
assert(input_link != NULL && "Illegal input relocation section.");
// get the linked output section
LDSection* output_link = pModule.getSection(input_link->name());
assert(output_link != NULL);
output_sect->setLink(output_link);
// get output relcoationData, create one if not exist
if (!output_sect->hasRelocData())
IRBuilder::CreateRelocData(*output_sect);
RelocData* out_reloc_data = output_sect->getRelocData();
// move relocations from input's to output's RelcoationData
RelocData::RelocationListType& out_list =
out_reloc_data->getRelocationList();
RelocData::RelocationListType& in_list =
(*rs)->getRelocData()->getRelocationList();
out_list.splice(out_list.end(), in_list);
// size output
if (llvm::ELF::SHT_REL == output_sect->type())
output_sect->setSize(out_reloc_data->size() * getRelEntrySize());
else if (llvm::ELF::SHT_RELA == output_sect->type())
output_sect->setSize(out_reloc_data->size() * getRelaEntrySize());
else {
fatal(diag::unknown_reloc_section_type) << output_sect->type()
<< output_sect->name();
}
} // end of for each relocation section
} // end of for each input
} // end of if
// set up the section flag of .note.GNU-stack section
setupGNUStackInfo(pModule);
}
/// postLayout - Backend can do any needed modification after layout
void GNULDBackend::postLayout(Module& pModule, IRBuilder& pBuilder) {
if (LinkerConfig::Object != config().codeGenType()) {
// do relaxation
relax(pModule, pBuilder);
// set up the attributes of program headers
setupProgramHdrs(pModule.getScript());
}
doPostLayout(pModule, pBuilder);
}
void GNULDBackend::postProcessing(FileOutputBuffer& pOutput) {
if (LinkerConfig::Object != config().codeGenType() &&
config().options().hasEhFrameHdr() && getOutputFormat()->hasEhFrame()) {
// emit eh_frame_hdr
m_pEhFrameHdr->emitOutput<32>(pOutput);
}
}
/// getHashBucketCount - calculate hash bucket count.
unsigned GNULDBackend::getHashBucketCount(unsigned pNumOfSymbols,
bool pIsGNUStyle) {
static const unsigned int buckets[] = {
1, 3, 17, 37, 67, 97, 131, 197, 263, 521, 1031, 2053, 4099, 8209, 16411,
32771, 65537, 131101, 262147
};
const unsigned buckets_count = sizeof buckets / sizeof buckets[0];
unsigned int result = 1;
for (unsigned i = 0; i < buckets_count; ++i) {
if (pNumOfSymbols < buckets[i])
break;
result = buckets[i];
}
if (pIsGNUStyle && result < 2)
result = 2;
return result;
}
/// getGNUHashMaskbitslog2 - calculate the number of mask bits in log2
unsigned GNULDBackend::getGNUHashMaskbitslog2(unsigned pNumOfSymbols) const {
uint32_t maskbitslog2 = 1;
for (uint32_t x = pNumOfSymbols >> 1; x != 0; x >>= 1)
++maskbitslog2;
if (maskbitslog2 < 3)
maskbitslog2 = 5;
else if (((1U << (maskbitslog2 - 2)) & pNumOfSymbols) != 0)
maskbitslog2 += 3;
else
maskbitslog2 += 2;
if (config().targets().bitclass() == 64 && maskbitslog2 == 5)
maskbitslog2 = 6;
return maskbitslog2;
}
/// isDynamicSymbol
bool GNULDBackend::isDynamicSymbol(const LDSymbol& pSymbol) const {
// If a local symbol is in the LDContext's symbol table, it's a real local
// symbol. We should not add it
if (pSymbol.binding() == ResolveInfo::Local)
return false;
// If we are building shared object, and the visibility is external, we
// need to add it.
if (LinkerConfig::DynObj == config().codeGenType() ||
LinkerConfig::Exec == config().codeGenType() ||
LinkerConfig::Binary == config().codeGenType()) {
if (pSymbol.resolveInfo()->visibility() == ResolveInfo::Default ||
pSymbol.resolveInfo()->visibility() == ResolveInfo::Protected)
return true;
}
return false;
}
/// isDynamicSymbol
bool GNULDBackend::isDynamicSymbol(const ResolveInfo& pResolveInfo) const {
// If a local symbol is in the LDContext's symbol table, it's a real local
// symbol. We should not add it
if (pResolveInfo.binding() == ResolveInfo::Local)
return false;
// If we are building shared object, and the visibility is external, we
// need to add it.
if (LinkerConfig::DynObj == config().codeGenType() ||
LinkerConfig::Exec == config().codeGenType() ||
LinkerConfig::Binary == config().codeGenType()) {
if (pResolveInfo.visibility() == ResolveInfo::Default ||
pResolveInfo.visibility() == ResolveInfo::Protected)
return true;
}
return false;
}
/// elfSegmentTable - return the reference of the elf segment table
ELFSegmentFactory& GNULDBackend::elfSegmentTable() {
assert(m_pELFSegmentTable != NULL && "Do not create ELFSegmentTable!");
return *m_pELFSegmentTable;
}
/// elfSegmentTable - return the reference of the elf segment table
const ELFSegmentFactory& GNULDBackend::elfSegmentTable() const {
assert(m_pELFSegmentTable != NULL && "Do not create ELFSegmentTable!");
return *m_pELFSegmentTable;
}
/// commonPageSize - the common page size of the target machine.
uint64_t GNULDBackend::commonPageSize() const {
if (config().options().commPageSize() > 0)
return std::min(config().options().commPageSize(), abiPageSize());
else
return std::min(m_pInfo->commonPageSize(), abiPageSize());
}
/// abiPageSize - the abi page size of the target machine.
uint64_t GNULDBackend::abiPageSize() const {
if (config().options().maxPageSize() > 0)
return config().options().maxPageSize();
else
return m_pInfo->abiPageSize();
}
/// isSymbolPreemtible - whether the symbol can be preemted by other
/// link unit
bool GNULDBackend::isSymbolPreemptible(const ResolveInfo& pSym) const {
if (pSym.other() != ResolveInfo::Default)
return false;
// This is because the codeGenType of pie is DynObj. And gold linker check
// the "shared" option instead.
if (config().options().isPIE())
return false;
if (LinkerConfig::DynObj != config().codeGenType())
return false;
if (config().options().Bsymbolic())
return false;
// A local defined symbol should be non-preemptible.
// This issue is found when linking libstdc++ on freebsd. A R_386_GOT32
// relocation refers to a local defined symbol, and we should generate a
// relative dynamic relocation when applying the relocation.
if (pSym.isDefine() && pSym.binding() == ResolveInfo::Local)
return false;
return true;
}
/// symbolNeedsDynRel - return whether the symbol needs a dynamic relocation
bool GNULDBackend::symbolNeedsDynRel(const ResolveInfo& pSym,
bool pSymHasPLT,
bool isAbsReloc) const {
// an undefined reference in the executables should be statically
// resolved to 0 and no need a dynamic relocation
if (pSym.isUndef() && !pSym.isDyn() &&
(LinkerConfig::Exec == config().codeGenType() ||
LinkerConfig::Binary == config().codeGenType()))
return false;
// An absolute symbol can be resolved directly if it is either local
// or we are linking statically. Otherwise it can still be overridden
// at runtime.
if (pSym.isAbsolute() &&
(pSym.binding() == ResolveInfo::Local || config().isCodeStatic()))
return false;
if (config().isCodeIndep() && isAbsReloc)
return true;
if (pSymHasPLT && ResolveInfo::Function == pSym.type())
return false;
if (!config().isCodeIndep() && pSymHasPLT)
return false;
if (pSym.isDyn() || pSym.isUndef() || isSymbolPreemptible(pSym))
return true;
return false;
}
/// symbolNeedsPLT - return whether the symbol needs a PLT entry
bool GNULDBackend::symbolNeedsPLT(const ResolveInfo& pSym) const {
if (pSym.isUndef() && !pSym.isDyn() &&
LinkerConfig::DynObj != config().codeGenType())
return false;
// An IndirectFunc symbol (i.e., STT_GNU_IFUNC) always needs a plt entry
if (pSym.type() == ResolveInfo::IndirectFunc)
return true;
if (pSym.type() != ResolveInfo::Function)
return false;
if (config().isCodeStatic())
return false;
if (config().options().isPIE())
return false;
return (pSym.isDyn() || pSym.isUndef() || isSymbolPreemptible(pSym));
}
/// symbolHasFinalValue - return true if the symbol's value can be decided at
/// link time
bool GNULDBackend::symbolFinalValueIsKnown(const ResolveInfo& pSym) const {
// if the output is pic code or if not executables, symbols' value may change
// at runtime
// FIXME: CodeIndep() || LinkerConfig::Relocatable == CodeGenType
if (config().isCodeIndep() ||
(LinkerConfig::Exec != config().codeGenType() &&
LinkerConfig::Binary != config().codeGenType()))
return false;
// if the symbol is from dynamic object, then its value is unknown
if (pSym.isDyn())
return false;
// if the symbol is not in dynamic object and is not undefined, then its value
// is known
if (!pSym.isUndef())
return true;
// if the symbol is undefined and not in dynamic objects, for example, a weak
// undefined symbol, then whether the symbol's final value can be known
// depends on whrther we're doing static link
return config().isCodeStatic();
}
/// symbolNeedsCopyReloc - return whether the symbol needs a copy relocation
bool GNULDBackend::symbolNeedsCopyReloc(const Relocation& pReloc,
const ResolveInfo& pSym) const {
// only the reference from dynamic executable to non-function symbol in
// the dynamic objects may need copy relocation
if (config().isCodeIndep() || !pSym.isDyn() ||
pSym.type() == ResolveInfo::Function || pSym.size() == 0)
return false;
// check if the option -z nocopyreloc is given
if (config().options().hasNoCopyReloc())
return false;
// TODO: Is this check necessary?
// if relocation target place is readonly, a copy relocation is needed
uint32_t flag = pReloc.targetRef().frag()->getParent()->getSection().flag();
if (0 == (flag & llvm::ELF::SHF_WRITE))
return true;
return false;
}
LDSymbol& GNULDBackend::getTDATASymbol() {
assert(f_pTDATA != NULL);
return *f_pTDATA;
}
const LDSymbol& GNULDBackend::getTDATASymbol() const {
assert(f_pTDATA != NULL);
return *f_pTDATA;
}
LDSymbol& GNULDBackend::getTBSSSymbol() {
assert(f_pTBSS != NULL);
return *f_pTBSS;
}
const LDSymbol& GNULDBackend::getTBSSSymbol() const {
assert(f_pTBSS != NULL);
return *f_pTBSS;
}
llvm::StringRef GNULDBackend::getEntry(const Module& pModule) const {
if (pModule.getScript().hasEntry())
return pModule.getScript().entry();
else
return getInfo().entry();
}
void GNULDBackend::checkAndSetHasTextRel(const LDSection& pSection) {
if (m_bHasTextRel)
return;
// if the target section of the dynamic relocation is ALLOCATE but is not
// writable, than we should set DF_TEXTREL
const uint32_t flag = pSection.flag();
if (0 == (flag & llvm::ELF::SHF_WRITE) && (flag & llvm::ELF::SHF_ALLOC))
m_bHasTextRel = true;
return;
}
/// sortRelocation - sort the dynamic relocations to let dynamic linker
/// process relocations more efficiently
void GNULDBackend::sortRelocation(LDSection& pSection) {
if (!config().options().hasCombReloc())
return;
assert(pSection.kind() == LDFileFormat::Relocation);
switch (config().codeGenType()) {
case LinkerConfig::DynObj:
case LinkerConfig::Exec:
if (&pSection == &getOutputFormat()->getRelDyn() ||
&pSection == &getOutputFormat()->getRelaDyn()) {
if (pSection.hasRelocData())
pSection.getRelocData()->sort(RelocCompare(*this));
}
default:
return;
}
}
unsigned GNULDBackend::stubGroupSize() const {
const unsigned group_size = config().targets().getStubGroupSize();
if (group_size == 0) {
return m_pInfo->stubGroupSize();
} else {
return group_size;
}
}
/// initBRIslandFactory - initialize the branch island factory for relaxation
bool GNULDBackend::initBRIslandFactory() {
if (m_pBRIslandFactory == NULL) {
m_pBRIslandFactory = new BranchIslandFactory(maxFwdBranchOffset(),
maxBwdBranchOffset(),
stubGroupSize());
}
return true;
}
/// initStubFactory - initialize the stub factory for relaxation
bool GNULDBackend::initStubFactory() {
if (m_pStubFactory == NULL) {
m_pStubFactory = new StubFactory();
}
return true;
}
bool GNULDBackend::relax(Module& pModule, IRBuilder& pBuilder) {
if (!mayRelax())
return true;
getBRIslandFactory()->group(pModule);
bool finished = true;
do {
if (doRelax(pModule, pBuilder, finished)) {
setOutputSectionAddress(pModule);
}
} while (!finished);
return true;
}
bool GNULDBackend::DynsymCompare::needGNUHash(const LDSymbol& X) const {
// FIXME: in bfd and gold linker, an undefined symbol might be hashed
// when the ouput is not PIC, if the symbol is referred by a non pc-relative
// reloc, and its value is set to the addr of the plt entry.
return !X.resolveInfo()->isUndef() && !X.isDyn();
}
bool GNULDBackend::DynsymCompare::operator()(const LDSymbol* X,
const LDSymbol* Y) const {
return !needGNUHash(*X) && needGNUHash(*Y);
}
bool GNULDBackend::RelocCompare::operator()(const Relocation& X,
const Relocation& Y) const {
// 1. compare if relocation is relative
if (X.symInfo() == NULL) {
if (Y.symInfo() != NULL)
return true;
} else if (Y.symInfo() == NULL) {
return false;
} else {
// 2. compare the symbol index
size_t symIdxX = m_Backend.getSymbolIdx(X.symInfo()->outSymbol());
size_t symIdxY = m_Backend.getSymbolIdx(Y.symInfo()->outSymbol());
if (symIdxX < symIdxY)
return true;
if (symIdxX > symIdxY)
return false;
}
// 3. compare the relocation address
if (X.place() < Y.place())
return true;
if (X.place() > Y.place())
return false;
// 4. compare the relocation type
if (X.type() < Y.type())
return true;
if (X.type() > Y.type())
return false;
// 5. compare the addend
if (X.addend() < Y.addend())
return true;
if (X.addend() > Y.addend())
return false;
return false;
}
} // namespace mcld