llvm-project/llvm/lib/Object/OffloadBinary.cpp

//===- Offloading.cpp - Utilities for handling offloading code  -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/Object/OffloadBinary.h"

#include "llvm/ADT/StringSwitch.h"
#include "llvm/BinaryFormat/Magic.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Module.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/Archive.h"
#include "llvm/Object/ArchiveWriter.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/Error.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/SourceMgr.h"

using namespace llvm;
using namespace llvm::object;

namespace {

/// Attempts to extract all the embedded device images contained inside the
/// buffer \p Contents. The buffer is expected to contain a valid offloading
/// binary format.
Error extractOffloadFiles(MemoryBufferRef Contents,
                          SmallVectorImpl<OffloadFile> &Binaries) {
  uint64_t Offset = 0;
  // There could be multiple offloading binaries stored at this section.
  while (Offset < Contents.getBuffer().size()) {
    std::unique_ptr<MemoryBuffer> Buffer =
        MemoryBuffer::getMemBuffer(Contents.getBuffer().drop_front(Offset), "",
                                   /*RequiresNullTerminator*/ false);
    auto BinaryOrErr = OffloadBinary::create(*Buffer);
    if (!BinaryOrErr)
      return BinaryOrErr.takeError();
    OffloadBinary &Binary = **BinaryOrErr;

    // Create a new owned binary with a copy of the original memory.
    std::unique_ptr<MemoryBuffer> BufferCopy = MemoryBuffer::getMemBufferCopy(
        Binary.getData().take_front(Binary.getSize()),
        Contents.getBufferIdentifier());
    auto NewBinaryOrErr = OffloadBinary::create(*BufferCopy);
    if (!NewBinaryOrErr)
      return NewBinaryOrErr.takeError();
    Binaries.emplace_back(std::move(*NewBinaryOrErr), std::move(BufferCopy));

    Offset += Binary.getSize();
  }

  return Error::success();
}

// Extract offloading binaries from an Object file \p Obj.
Error extractFromBinary(const ObjectFile &Obj,
                        SmallVectorImpl<OffloadFile> &Binaries) {
  for (ELFSectionRef Sec : Obj.sections()) {
    if (Sec.getType() != ELF::SHT_LLVM_OFFLOADING)
      continue;

    Expected<StringRef> Buffer = Sec.getContents();
    if (!Buffer)
      return Buffer.takeError();

    MemoryBufferRef Contents(*Buffer, Obj.getFileName());
    if (Error Err = extractOffloadFiles(Contents, Binaries))
      return Err;
  }

  return Error::success();
}

Error extractFromBitcode(MemoryBufferRef Buffer,
                         SmallVectorImpl<OffloadFile> &Binaries) {
  LLVMContext Context;
  SMDiagnostic Err;
  std::unique_ptr<Module> M = getLazyIRModule(
      MemoryBuffer::getMemBuffer(Buffer, /*RequiresNullTerminator=*/false), Err,
      Context);
  if (!M)
    return createStringError(inconvertibleErrorCode(),
                             "Failed to create module");

  // Extract offloading data from globals referenced by the
  // `llvm.embedded.object` metadata with the `.llvm.offloading` section.
  auto *MD = M->getNamedMetadata("llvm.embedded.objects");
  if (!MD)
    return Error::success();

  for (const MDNode *Op : MD->operands()) {
    if (Op->getNumOperands() < 2)
      continue;

    MDString *SectionID = dyn_cast<MDString>(Op->getOperand(1));
    if (!SectionID || SectionID->getString() != ".llvm.offloading")
      continue;

    GlobalVariable *GV =
        mdconst::dyn_extract_or_null<GlobalVariable>(Op->getOperand(0));
    if (!GV)
      continue;

    auto *CDS = dyn_cast<ConstantDataSequential>(GV->getInitializer());
    if (!CDS)
      continue;

    MemoryBufferRef Contents(CDS->getAsString(), M->getName());
    if (Error Err = extractOffloadFiles(Contents, Binaries))
      return Err;
  }

  return Error::success();
}

Error extractFromArchive(const Archive &Library,
                         SmallVectorImpl<OffloadFile> &Binaries) {
  // Try to extract device code from each file stored in the static archive.
  Error Err = Error::success();
  for (auto Child : Library.children(Err)) {
    auto ChildBufferOrErr = Child.getMemoryBufferRef();
    if (!ChildBufferOrErr)
      return ChildBufferOrErr.takeError();
    std::unique_ptr<MemoryBuffer> ChildBuffer =
        MemoryBuffer::getMemBuffer(*ChildBufferOrErr, false);

    // Check if the buffer has the required alignment.
    if (!isAddrAligned(Align(OffloadBinary::getAlignment()),
                       ChildBuffer->getBufferStart()))
      ChildBuffer = MemoryBuffer::getMemBufferCopy(
          ChildBufferOrErr->getBuffer(),
          ChildBufferOrErr->getBufferIdentifier());

    if (Error Err = extractOffloadBinaries(*ChildBuffer, Binaries))
      return Err;
  }

  if (Err)
    return Err;
  return Error::success();
}

} // namespace

Expected<std::unique_ptr<OffloadBinary>>
OffloadBinary::create(MemoryBufferRef Buf) {
  if (Buf.getBufferSize() < sizeof(Header) + sizeof(Entry))
    return errorCodeToError(object_error::parse_failed);

  // Check for 0x10FF1OAD magic bytes.
  if (identify_magic(Buf.getBuffer()) != file_magic::offload_binary)
    return errorCodeToError(object_error::parse_failed);

  // Make sure that the data has sufficient alignment.
  if (!isAddrAligned(Align(getAlignment()), Buf.getBufferStart()))
    return errorCodeToError(object_error::parse_failed);

  const char *Start = Buf.getBufferStart();
  const Header *TheHeader = reinterpret_cast<const Header *>(Start);
  if (TheHeader->Version != OffloadBinary::Version)
    return errorCodeToError(object_error::parse_failed);

  if (TheHeader->Size > Buf.getBufferSize() ||
      TheHeader->EntryOffset > TheHeader->Size - sizeof(Entry) ||
      TheHeader->EntrySize > TheHeader->Size - sizeof(Header))
    return errorCodeToError(object_error::unexpected_eof);

  const Entry *TheEntry =
      reinterpret_cast<const Entry *>(&Start[TheHeader->EntryOffset]);

  if (TheEntry->ImageOffset > Buf.getBufferSize() ||
      TheEntry->StringOffset > Buf.getBufferSize())
    return errorCodeToError(object_error::unexpected_eof);

  return std::unique_ptr<OffloadBinary>(
      new OffloadBinary(Buf, TheHeader, TheEntry));
}

std::unique_ptr<MemoryBuffer>
OffloadBinary::write(const OffloadingImage &OffloadingData) {
  // Create a null-terminated string table with all the used strings.
  StringTableBuilder StrTab(StringTableBuilder::ELF);
  for (auto &KeyAndValue : OffloadingData.StringData) {
    StrTab.add(KeyAndValue.getKey());
    StrTab.add(KeyAndValue.getValue());
  }
  StrTab.finalize();

  uint64_t StringEntrySize =
      sizeof(StringEntry) * OffloadingData.StringData.size();

  // Make sure the image we're wrapping around is aligned as well.
  uint64_t BinaryDataSize = alignTo(sizeof(Header) + sizeof(Entry) +
                                        StringEntrySize + StrTab.getSize(),
                                    getAlignment());

  // Create the header and fill in the offsets. The entry will be directly
  // placed after the header in memory. Align the size to the alignment of the
  // header so this can be placed contiguously in a single section.
  Header TheHeader;
  TheHeader.Size = alignTo(
      BinaryDataSize + OffloadingData.Image->getBufferSize(), getAlignment());
  TheHeader.EntryOffset = sizeof(Header);
  TheHeader.EntrySize = sizeof(Entry);

  // Create the entry using the string table offsets. The string table will be
  // placed directly after the entry in memory, and the image after that.
  Entry TheEntry;
  TheEntry.TheImageKind = OffloadingData.TheImageKind;
  TheEntry.TheOffloadKind = OffloadingData.TheOffloadKind;
  TheEntry.Flags = OffloadingData.Flags;
  TheEntry.StringOffset = sizeof(Header) + sizeof(Entry);
  TheEntry.NumStrings = OffloadingData.StringData.size();

  TheEntry.ImageOffset = BinaryDataSize;
  TheEntry.ImageSize = OffloadingData.Image->getBufferSize();

  SmallVector<char> Data;
  Data.reserve(TheHeader.Size);
  raw_svector_ostream OS(Data);
  OS << StringRef(reinterpret_cast<char *>(&TheHeader), sizeof(Header));
  OS << StringRef(reinterpret_cast<char *>(&TheEntry), sizeof(Entry));
  for (auto &KeyAndValue : OffloadingData.StringData) {
    uint64_t Offset = sizeof(Header) + sizeof(Entry) + StringEntrySize;
    StringEntry Map{Offset + StrTab.getOffset(KeyAndValue.getKey()),
                    Offset + StrTab.getOffset(KeyAndValue.getValue())};
    OS << StringRef(reinterpret_cast<char *>(&Map), sizeof(StringEntry));
  }
  StrTab.write(OS);
  // Add padding to required image alignment.
  OS.write_zeros(TheEntry.ImageOffset - OS.tell());
  OS << OffloadingData.Image->getBuffer();

  // Add final padding to required alignment.
  assert(TheHeader.Size >= OS.tell() && "Too much data written?");
  OS.write_zeros(TheHeader.Size - OS.tell());
  assert(TheHeader.Size == OS.tell() && "Size mismatch");

  return MemoryBuffer::getMemBufferCopy(OS.str());
}

Error object::extractOffloadBinaries(MemoryBufferRef Buffer,
                                     SmallVectorImpl<OffloadFile> &Binaries) {
  file_magic Type = identify_magic(Buffer.getBuffer());
  switch (Type) {
  case file_magic::bitcode:
    return extractFromBitcode(Buffer, Binaries);
  case file_magic::elf_relocatable: {
    Expected<std::unique_ptr<ObjectFile>> ObjFile =
        ObjectFile::createObjectFile(Buffer, Type);
    if (!ObjFile)
      return ObjFile.takeError();
    return extractFromBinary(*ObjFile->get(), Binaries);
  }
  case file_magic::archive: {
    Expected<std::unique_ptr<llvm::object::Archive>> LibFile =
        object::Archive::create(Buffer);
    if (!LibFile)
      return LibFile.takeError();
    return extractFromArchive(*LibFile->get(), Binaries);
  }
  case file_magic::offload_binary:
    return extractOffloadFiles(Buffer, Binaries);
  default:
    return Error::success();
  }
}

OffloadKind object::getOffloadKind(StringRef Name) {
  return llvm::StringSwitch<OffloadKind>(Name)
      .Case("openmp", OFK_OpenMP)
      .Case("cuda", OFK_Cuda)
      .Case("hip", OFK_HIP)
      .Default(OFK_None);
}

StringRef object::getOffloadKindName(OffloadKind Kind) {
  switch (Kind) {
  case OFK_OpenMP:
    return "openmp";
  case OFK_Cuda:
    return "cuda";
  case OFK_HIP:
    return "hip";
  default:
    return "none";
  }
}

ImageKind object::getImageKind(StringRef Name) {
  return llvm::StringSwitch<ImageKind>(Name)
      .Case("o", IMG_Object)
      .Case("bc", IMG_Bitcode)
      .Case("cubin", IMG_Cubin)
      .Case("fatbin", IMG_Fatbinary)
      .Case("s", IMG_PTX)
      .Default(IMG_None);
}

StringRef object::getImageKindName(ImageKind Kind) {
  switch (Kind) {
  case IMG_Object:
    return "o";
  case IMG_Bitcode:
    return "bc";
  case IMG_Cubin:
    return "cubin";
  case IMG_Fatbinary:
    return "fatbin";
  case IMG_PTX:
    return "s";
  default:
    return "";
  }
}