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//===- EhFrameHdr.cpp -----------------------------------------------------===//
//
// The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include <mcld/LD/EhFrameHdr.h>
#include <mcld/LD/EhFrame.h>
#include <mcld/LD/LDSection.h>
#include <llvm/Support/Dwarf.h>
#include <llvm/Support/DataTypes.h>
#include <algorithm>
#include <cstring>
using namespace mcld;
using namespace llvm::dwarf;
//===----------------------------------------------------------------------===//
// Helper Function
//===----------------------------------------------------------------------===//
namespace bit32 {
typedef std::pair<SizeTraits<32>::Address, SizeTraits<32>::Address> Entry;
bool EntryCompare(const Entry& pX, const Entry& pY)
{ return (pX.first < pY.first); }
} // bit32 namespace
//===----------------------------------------------------------------------===//
// Template Specification Functions
//===----------------------------------------------------------------------===//
/// emitOutput<32> - write out eh_frame_hdr
template<>
void EhFrameHdr::emitOutput<32>(FileOutputBuffer& pOutput)
{
MemoryRegion ehframehdr_region = pOutput.request(m_EhFrameHdr.offset(),
m_EhFrameHdr.size());
MemoryRegion ehframe_region = pOutput.request(m_EhFrame.offset(),
m_EhFrame.size());
uint8_t* data = ehframehdr_region.begin();
// version
data[0] = 1;
// eh_frame_ptr_enc
data[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4;
// eh_frame_ptr
uint32_t* eh_frame_ptr = (uint32_t*)(data + 4);
*eh_frame_ptr = m_EhFrame.addr() - (m_EhFrameHdr.addr() + 4);
// fde_count
uint32_t* fde_count = (uint32_t*)(data + 8);
if (m_EhFrame.hasEhFrame())
*fde_count = m_EhFrame.getEhFrame()->numOfFDEs();
else
*fde_count = 0;
if (0 == *fde_count) {
// fde_count_enc
data[2] = DW_EH_PE_omit;
// table_enc
data[3] = DW_EH_PE_omit;
}
else {
// fde_count_enc
data[2] = DW_EH_PE_udata4;
// table_enc
data[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4;
// prepare the binary search table
typedef std::vector<bit32::Entry> SearchTableType;
SearchTableType search_table;
for (EhFrame::const_cie_iterator i = m_EhFrame.getEhFrame()->cie_begin(),
e = m_EhFrame.getEhFrame()->cie_end(); i != e; ++i) {
EhFrame::CIE& cie = **i;
for (EhFrame::const_fde_iterator fi = cie.begin(), fe = cie.end();
fi != fe; ++fi) {
EhFrame::FDE& fde = **fi;
SizeTraits<32>::Offset offset;
SizeTraits<32>::Address fde_pc;
SizeTraits<32>::Address fde_addr;
offset = fde.getOffset();
fde_pc = computePCBegin(fde, ehframe_region);
fde_addr = m_EhFrame.addr() + offset;
search_table.push_back(std::make_pair(fde_pc, fde_addr));
}
}
std::sort(search_table.begin(), search_table.end(), bit32::EntryCompare);
// write out the binary search table
uint32_t* bst = (uint32_t*)(data + 12);
SearchTableType::const_iterator entry, entry_end = search_table.end();
size_t id = 0;
for (entry = search_table.begin(); entry != entry_end; ++entry) {
bst[id++] = (*entry).first - m_EhFrameHdr.addr();
bst[id++] = (*entry).second - m_EhFrameHdr.addr();
}
}
}
//===----------------------------------------------------------------------===//
// EhFrameHdr
//===----------------------------------------------------------------------===//
EhFrameHdr::EhFrameHdr(LDSection& pEhFrameHdr, const LDSection& pEhFrame)
: m_EhFrameHdr(pEhFrameHdr), m_EhFrame(pEhFrame) {
}
EhFrameHdr::~EhFrameHdr()
{
}
/// @ref lsb core generic 4.1
/// .eh_frame_hdr section format
/// uint8_t : version
/// uint8_t : eh_frame_ptr_enc
/// uint8_t : fde_count_enc
/// uint8_t : table_enc
/// uint32_t : eh_frame_ptr
/// uint32_t : fde_count
/// __________________________ when fde_count > 0
/// <uint32_t, uint32_t>+ : binary search table
/// sizeOutput - base on the fde count to size output
void EhFrameHdr::sizeOutput()
{
size_t size = 12;
if (m_EhFrame.hasEhFrame())
size += 8 * m_EhFrame.getEhFrame()->numOfFDEs();
m_EhFrameHdr.setSize(size);
}
/// computePCBegin - return the address of FDE's pc
/// @ref binutils gold: ehframe.cc:222
uint32_t EhFrameHdr::computePCBegin(const EhFrame::FDE& pFDE,
const MemoryRegion& pEhFrameRegion)
{
uint8_t fde_encoding = pFDE.getCIE().getFDEEncode();
unsigned int eh_value = fde_encoding & 0x7;
// check the size to read in
if (eh_value == llvm::dwarf::DW_EH_PE_absptr) {
eh_value = DW_EH_PE_udata4;
}
size_t pc_size = 0x0;
switch (eh_value) {
case DW_EH_PE_udata2:
pc_size = 2;
break;
case DW_EH_PE_udata4:
pc_size = 4;
break;
case DW_EH_PE_udata8:
pc_size = 8;
break;
default:
// TODO
break;
}
SizeTraits<32>::Address pc = 0x0;
const uint8_t* offset = (const uint8_t*) pEhFrameRegion.begin() +
pFDE.getOffset() +
EhFrame::getDataStartOffset<32>();
std::memcpy(&pc, offset, pc_size);
// adjust the signed value
bool is_signed = (fde_encoding & llvm::dwarf::DW_EH_PE_signed) != 0x0;
if (DW_EH_PE_udata2 == eh_value && is_signed)
pc = (pc ^ 0x8000) - 0x8000;
// handle eh application
switch (fde_encoding & 0x70)
{
case DW_EH_PE_absptr:
break;
case DW_EH_PE_pcrel:
pc += m_EhFrame.addr() + pFDE.getOffset() +
EhFrame::getDataStartOffset<32>();
break;
case DW_EH_PE_datarel:
// TODO
break;
default:
// TODO
break;
}
return pc;
}
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