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//===- ELFReader.cpp ------------------------------------------------------===//
//
// The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include <mcld/LD/ELFReaderIf.h>
#include <mcld/IRBuilder.h>
#include <mcld/Fragment/FillFragment.h>
#include <mcld/LD/EhFrame.h>
#include <mcld/LD/SectionData.h>
#include <mcld/Target/GNULDBackend.h>
#include <cstring>
#include <llvm/ADT/StringRef.h>
#include <llvm/ADT/Twine.h>
#include <llvm/Support/ELF.h>
#include <llvm/Support/Host.h>
using namespace mcld;
//===----------------------------------------------------------------------===//
// ELFReaderIF
//===----------------------------------------------------------------------===//
/// getSymType
ResolveInfo::Type ELFReaderIF::getSymType(uint8_t pInfo, uint16_t pShndx) const
{
ResolveInfo::Type result = static_cast<ResolveInfo::Type>(pInfo & 0xF);
if (llvm::ELF::SHN_ABS == pShndx && ResolveInfo::Section == result) {
// In Mips, __gp_disp is a special section symbol. Its name comes from
// .strtab, not .shstrtab. However, it is unique. Only it is also a ABS
// symbol. So here is a tricky to identify __gp_disp and convert it to
// Object symbol.
return ResolveInfo::Object;
}
return result;
}
/// getSymDesc
ResolveInfo::Desc ELFReaderIF::getSymDesc(uint16_t pShndx, const Input& pInput) const
{
if (pShndx == llvm::ELF::SHN_UNDEF)
return ResolveInfo::Undefined;
if (pShndx < llvm::ELF::SHN_LORESERVE) {
// an ELF symbol defined in a section which we are not including
// must be treated as an Undefined.
// @ref Google gold linker: symtab.cc: 1086
if (NULL == pInput.context()->getSection(pShndx) ||
LDFileFormat::Ignore == pInput.context()->getSection(pShndx)->kind())
return ResolveInfo::Undefined;
return ResolveInfo::Define;
}
if (pShndx == llvm::ELF::SHN_ABS)
return ResolveInfo::Define;
if (pShndx == llvm::ELF::SHN_COMMON)
return ResolveInfo::Common;
if (pShndx >= llvm::ELF::SHN_LOPROC &&
pShndx <= llvm::ELF::SHN_HIPROC)
return target().getSymDesc(pShndx);
// FIXME: ELF weak alias should be ResolveInfo::Indirect
return ResolveInfo::NoneDesc;
}
/// getSymBinding
ResolveInfo::Binding
ELFReaderIF::getSymBinding(uint8_t pBinding, uint16_t pShndx, uint8_t pVis) const
{
// TODO:
// if --just-symbols option is enabled, the symbol must covert to Absolute
switch(pBinding) {
case llvm::ELF::STB_LOCAL:
return ResolveInfo::Local;
case llvm::ELF::STB_GLOBAL:
if (pShndx == llvm::ELF::SHN_ABS)
return ResolveInfo::Absolute;
return ResolveInfo::Global;
case llvm::ELF::STB_WEAK:
return ResolveInfo::Weak;
}
return ResolveInfo::NoneBinding;
}
/// getSymFragmentRef
FragmentRef*
ELFReaderIF::getSymFragmentRef(Input& pInput,
uint16_t pShndx,
uint32_t pOffset) const
{
if (Input::DynObj == pInput.type())
return FragmentRef::Null();
if (pShndx == llvm::ELF::SHN_UNDEF)
return FragmentRef::Null();
if (pShndx >= llvm::ELF::SHN_LORESERVE) // including ABS and COMMON
return FragmentRef::Null();
LDSection* sect_hdr = pInput.context()->getSection(pShndx);
if (NULL == sect_hdr)
unreachable(diag::unreachable_invalid_section_idx) << pShndx
<< pInput.path().native();
if (LDFileFormat::Ignore == sect_hdr->kind())
return FragmentRef::Null();
if (LDFileFormat::Group == sect_hdr->kind())
return FragmentRef::Null();
return FragmentRef::Create(*sect_hdr, pOffset);
}
/// getSymVisibility
ResolveInfo::Visibility
ELFReaderIF::getSymVisibility(uint8_t pVis) const
{
return static_cast<ResolveInfo::Visibility>(pVis);
}
/// getSymValue - get the section offset of the symbol.
uint64_t ELFReaderIF::getSymValue(uint64_t pValue,
uint16_t pShndx,
const Input& pInput) const
{
if (Input::Object == pInput.type()) {
// In relocatable files, st_value holds alignment constraints for a symbol
// whose section index is SHN_COMMON
if (pShndx == llvm::ELF::SHN_COMMON || pShndx == llvm::ELF::SHN_ABS) {
return pValue;
}
// In relocatable files, st_value holds a section offset for a defined symbol.
// TODO:
// if --just-symbols option are enabled, convert the value from section offset
// to virtual address by adding input section's virtual address.
// The section's virtual address in relocatable files is normally zero, but
// people can use link script to change it.
return pValue;
}
// In executable and shared object files, st_value holds a virtual address.
// the virtual address is needed for alias identification.
return pValue;
}
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