lld/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp

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

#include "Atoms.h"
#include "GroupedSectionsPass.h"
#include "IdataPass.h"
#include "LinkerGeneratedSymbolFile.h"

#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Path.h"
#include "lld/Core/PassManager.h"
#include "lld/Passes/LayoutPass.h"
#include "lld/ReaderWriter/PECOFFLinkingContext.h"
#include "lld/ReaderWriter/Reader.h"
#include "lld/ReaderWriter/Simple.h"
#include "lld/ReaderWriter/Writer.h"

#include <bitset>
#include <set>

namespace lld {

namespace {} // anonymous namespace

bool PECOFFLinkingContext::validateImpl(raw_ostream &diagnostics) {
  if (_stackReserve < _stackCommit) {
    diagnostics << "Invalid stack size: reserve size must be equal to or "
                << "greater than commit size, but got " << _stackCommit
                << " and " << _stackReserve << ".\n";
    return false;
  }

  if (_heapReserve < _heapCommit) {
    diagnostics << "Invalid heap size: reserve size must be equal to or "
                << "greater than commit size, but got " << _heapCommit
                << " and " << _heapReserve << ".\n";
    return false;
  }

  // It's an error if the base address is not multiple of 64K.
  if (_baseAddress & 0xffff) {
    diagnostics << "Base address have to be multiple of 64K, but got "
                << _baseAddress << "\n";
    return false;
  }

  std::bitset<64> alignment(_sectionAlignment);
  if (alignment.count() != 1) {
    diagnostics << "Section alignment must be a power of 2, but got "
                << _sectionAlignment << "\n";
    return false;
  }

  // Architectures other than i386 is not supported yet.
  if (_machineType != llvm::COFF::IMAGE_FILE_MACHINE_I386) {
    diagnostics << "Machine type other than x86 is not supported.\n";
    return false;
  }

  _reader = createReaderPECOFF(*this);
  _writer = createWriterPECOFF(*this);
  return true;
}

std::unique_ptr<File> PECOFFLinkingContext::createEntrySymbolFile() const {
  if (entrySymbolName().empty())
    return nullptr;
  std::unique_ptr<SimpleFile> entryFile(
      new SimpleFile(*this, "command line option /entry"));
  entryFile->addAtom(
      *(new (_allocator) SimpleUndefinedAtom(*entryFile, entrySymbolName())));
  return std::move(entryFile);
}

std::unique_ptr<File> PECOFFLinkingContext::createUndefinedSymbolFile() const {
  if (_initialUndefinedSymbols.empty())
    return nullptr;
  std::unique_ptr<SimpleFile> undefinedSymFile(
      new SimpleFile(*this, "command line option /c (or) /include"));
  for (auto undefSymStr : _initialUndefinedSymbols)
    undefinedSymFile->addAtom(*(new (_allocator) SimpleUndefinedAtom(
                                   *undefinedSymFile, undefSymStr)));
  return std::move(undefinedSymFile);
}

bool PECOFFLinkingContext::createImplicitFiles(
    std::vector<std::unique_ptr<File> > &) const {
  std::unique_ptr<SimpleFileNode> fileNode(
      new SimpleFileNode("Implicit Files"));
  std::unique_ptr<File> linkerGeneratedSymFile(
      new coff::LinkerGeneratedSymbolFile(*this));
  fileNode->appendInputFile(std::move(linkerGeneratedSymFile));
  inputGraph().insertOneElementAt(std::move(fileNode),
                                  InputGraph::Position::END);
  return true;
}

/// Returns the section name in the resulting executable.
///
/// Sections in object files are usually output to the executable with the same
/// name, but you can rename by command line option. /merge:from=to makes the
/// linker to combine "from" section contents to "to" section in the
/// executable. We have a mapping for the renaming. This method looks up the
/// table and returns a new section name if renamed.
StringRef
PECOFFLinkingContext::getFinalSectionName(StringRef sectionName) const {
  auto it = _renamedSections.find(sectionName);
  if (it == _renamedSections.end())
    return sectionName;
  return getFinalSectionName(it->second);
}

/// Adds a mapping to the section renaming table. This method will be used for
/// /merge command line option.
bool PECOFFLinkingContext::addSectionRenaming(raw_ostream &diagnostics,
                                              StringRef from, StringRef to) {
  auto it = _renamedSections.find(from);
  if (it != _renamedSections.end()) {
    if (it->second == to)
      // There's already the same mapping.
      return true;
    diagnostics << "Section \"" << from << "\" is already mapped to \""
                << it->second << ", so it cannot be mapped to \"" << to << "\".";
    return true;
  }

  // Add a mapping, and check if there's no cycle in the renaming mapping. The
  // cycle detection algorithm we use here is naive, but that's OK because the
  // number of mapping is usually less than 10.
  _renamedSections[from] = to;
  for (auto elem : _renamedSections) {
    StringRef sectionName = elem.first;
    std::set<StringRef> visited;
    visited.insert(sectionName);
    for (;;) {
      auto it = _renamedSections.find(sectionName);
      if (it == _renamedSections.end())
        break;
      if (visited.count(it->second)) {
        diagnostics << "/merge:" << from << "=" << to << " makes a cycle";
        return false;
      }
      sectionName = it->second;
      visited.insert(sectionName);
    }
  }
  return true;
}

/// Try to find the input library file from the search paths and append it to
/// the input file list. Returns true if the library file is found.
StringRef PECOFFLinkingContext::searchLibraryFile(StringRef filename) const {
  // Current directory always takes precedence over the search paths.
  if (llvm::sys::path::is_absolute(filename) || llvm::sys::fs::exists(filename))
    return filename;
  // Iterate over the search paths.
  for (StringRef dir : _inputSearchPaths) {
    SmallString<128> path = dir;
    llvm::sys::path::append(path, filename);
    if (llvm::sys::fs::exists(path.str()))
      return allocateString(path.str());
  }
  return filename;
}

Writer &PECOFFLinkingContext::writer() const { return *_writer; }

#define LLD_CASE(name) .Case(#name, llvm::COFF::name)

ErrorOr<Reference::Kind>
PECOFFLinkingContext::relocKindFromString(StringRef str) const {
  int32_t ret = llvm::StringSwitch<int32_t>(str)
        LLD_CASE(IMAGE_REL_I386_ABSOLUTE)
        LLD_CASE(IMAGE_REL_I386_DIR32)
        LLD_CASE(IMAGE_REL_I386_DIR32NB)
        LLD_CASE(IMAGE_REL_I386_REL32)
        .Default(-1);
  if (ret == -1)
    return make_error_code(YamlReaderError::illegal_value);
  return ret;
}

#undef LLD_CASE

#define LLD_CASE(name)                                                         \
  case llvm::COFF::name:                                                        \
  return std::string(#name);

ErrorOr<std::string>
PECOFFLinkingContext::stringFromRelocKind(Reference::Kind kind) const {
  switch (kind) {
    LLD_CASE(IMAGE_REL_I386_ABSOLUTE)
    LLD_CASE(IMAGE_REL_I386_DIR32)
    LLD_CASE(IMAGE_REL_I386_DIR32NB)
    LLD_CASE(IMAGE_REL_I386_REL32)
  }
  return make_error_code(YamlReaderError::illegal_value);
}

void PECOFFLinkingContext::addPasses(PassManager &pm) {
  pm.add(std::unique_ptr<Pass>(new pecoff::GroupedSectionsPass()));
  pm.add(std::unique_ptr<Pass>(new pecoff::IdataPass(*this)));
  pm.add(std::unique_ptr<Pass>(new LayoutPass()));
}
} // end namespace lld