//===- lib/ReaderWriter/ELF/X86/X86RelocationHandler.cpp ------------------===//
//
//                             The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "X86LinkingContext.h"
#include "X86TargetHandler.h"

using namespace lld;
using namespace elf;

namespace {
/// \brief R_386_32 - word32:  S + A
static int reloc32(uint8_t *location, uint64_t P, uint64_t S, uint64_t A) {
  int32_t result = (uint32_t)(S + A);
  *reinterpret_cast<llvm::support::ulittle32_t *>(location) =
      result |
      (uint32_t) * reinterpret_cast<llvm::support::ulittle32_t *>(location);
  return 0;
}

/// \brief R_386_PC32 - word32: S + A - P
static int relocPC32(uint8_t *location, uint64_t P, uint64_t S, uint64_t A) {
  uint32_t result = (uint32_t)((S + A) - P);
  *reinterpret_cast<llvm::support::ulittle32_t *>(location) =
      result +
      (uint32_t) * reinterpret_cast<llvm::support::ulittle32_t *>(location);
  return 0;
}
}

std::error_code X86TargetRelocationHandler::applyRelocation(
    ELFWriter &writer, llvm::FileOutputBuffer &buf, const lld::AtomLayout &atom,
    const Reference &ref) const {
  uint8_t *atomContent = buf.getBufferStart() + atom._fileOffset;
  uint8_t *location = atomContent + ref.offsetInAtom();
  uint64_t targetVAddress = writer.addressOfAtom(ref.target());
  uint64_t relocVAddress = atom._virtualAddr + ref.offsetInAtom();

  if (ref.kindNamespace() != Reference::KindNamespace::ELF)
    return std::error_code();
  assert(ref.kindArch() == Reference::KindArch::x86);
  switch (ref.kindValue()) {
  case R_386_32:
    reloc32(location, relocVAddress, targetVAddress, ref.addend());
    break;
  case R_386_PC32:
    relocPC32(location, relocVAddress, targetVAddress, ref.addend());
    break;
  default: {
    std::string str;
    llvm::raw_string_ostream s(str);
    s << "Unhandled I386 relocation # " << ref.kindValue();
    s.flush();
    llvm_unreachable(str.c_str());
  }
  }

  return std::error_code();
}