lib/MC/XCOFFObjectWriter.cpp

   1 //===-- lib/MC/XCOFFObjectWriter.cpp - XCOFF file writer ------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements XCOFF object file writer information.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/MC/MCAssembler.h"
  14 #include "llvm/MC/MCObjectWriter.h"
  15 #include "llvm/MC/MCValue.h"
  16 #include "llvm/MC/MCXCOFFObjectWriter.h"
  17
  18 using namespace llvm;
  19
  20 namespace {
  21
  22 class XCOFFObjectWriter : public MCObjectWriter {
  23   support::endian::Writer W;
  24   std::unique_ptr<MCXCOFFObjectTargetWriter> TargetObjectWriter;
  25
  26   void executePostLayoutBinding(MCAssembler &, const MCAsmLayout &) override;
  27
  28   void recordRelocation(MCAssembler &, const MCAsmLayout &, const MCFragment *,
  29                         const MCFixup &, MCValue, uint64_t &) override;
  30
  31   uint64_t writeObject(MCAssembler &, const MCAsmLayout &) override;
  32
  33 public:
  34   XCOFFObjectWriter(std::unique_ptr<MCXCOFFObjectTargetWriter> MOTW,
  35                     raw_pwrite_stream &OS);
  36 };
  37
  38 XCOFFObjectWriter::XCOFFObjectWriter(
  39     std::unique_ptr<MCXCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
  40     : W(OS, support::big), TargetObjectWriter(std::move(MOTW)) {}
  41
  42 void XCOFFObjectWriter::executePostLayoutBinding(MCAssembler &,
  43                                                  const MCAsmLayout &) {
  44   // TODO Implement once we have sections and symbols to handle.
  45 }
  46
  47 void XCOFFObjectWriter::recordRelocation(MCAssembler &, const MCAsmLayout &,
  48                                          const MCFragment *, const MCFixup &,
  49                                          MCValue, uint64_t &) {
  50   report_fatal_error("XCOFF relocations not supported.");
  51 }
  52
  53 uint64_t XCOFFObjectWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &) {
  54   // We always emit a timestamp of 0 for reproducibility, so ensure incremental
  55   // linking is not enabled, in case, like with Windows COFF, such a timestamp
  56   // is incompatible with incremental linking of XCOFF.
  57   if (Asm.isIncrementalLinkerCompatible())
  58     report_fatal_error("Incremental linking not supported for XCOFF.");
  59
  60   if (TargetObjectWriter->is64Bit())
  61     report_fatal_error("64-bit XCOFF object files are not supported yet.");
  62
  63   uint64_t StartOffset = W.OS.tell();
  64
  65   // TODO FIXME Assign section numbers/finalize sections.
  66
  67   // TODO FIXME Finalize symbols.
  68
  69   // Magic.
  70   W.write<uint16_t>(0x01df);
  71   // Number of sections.
  72   W.write<uint16_t>(0);
  73   // Timestamp field. For reproducible output we write a 0, which represents no
  74   // timestamp.
  75   W.write<int32_t>(0);
  76   // Byte Offset to the start of the symbol table.
  77   W.write<uint32_t>(0);
  78   // Number of entries in the symbol table.
  79   W.write<int32_t>(0);
  80   // Size of the optional header.
  81   W.write<uint16_t>(0);
  82   // Flags.
  83   W.write<uint16_t>(0);
  84
  85   return W.OS.tell() - StartOffset;
  86 }
  87
  88 } // end anonymous namespace
  89
  90 std::unique_ptr<MCObjectWriter>
  91 llvm::createXCOFFObjectWriter(std::unique_ptr<MCXCOFFObjectTargetWriter> MOTW,
  92                               raw_pwrite_stream &OS) {
  93   return std::make_unique<XCOFFObjectWriter>(std::move(MOTW), OS);
  94 }