ObjectContainerUniversalMachO.cpp

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//===-- ObjectContainerUniversalMachO.cpp ---------------------------------===//
//
// 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 "ObjectContainerUniversalMachO.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/ModuleSpec.h"
#include "lldb/Core/PluginManager.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Target/Target.h"
#include "lldb/Utility/ArchSpec.h"
#include "lldb/Utility/DataBuffer.h"
#include "lldb/Utility/Stream.h"
 
#include <algorithm>
 
using namespace lldb;
using namespace lldb_private;
using namespace llvm::MachO;
 
LLDB_PLUGIN_DEFINE_ADV(ObjectContainerUniversalMachO,
                       ObjectContainerMachOArchive)
 
void ObjectContainerUniversalMachO::Initialize() {
  PluginManager::RegisterPlugin(GetPluginNameStatic(),
                                GetPluginDescriptionStatic(), CreateInstance,
                                GetModuleSpecifications);
}
 
void ObjectContainerUniversalMachO::Terminate() {
  PluginManager::UnregisterPlugin(CreateInstance);
}
 
ObjectContainer *ObjectContainerUniversalMachO::CreateInstance(
    const lldb::ModuleSP &module_sp, DataBufferSP &data_sp,
    lldb::offset_t data_offset, const FileSpec *file,
    lldb::offset_t file_offset, lldb::offset_t length) {
  // We get data when we aren't trying to look for cached container
  // information, so only try and look for an architecture slice if we get data
  if (data_sp) {
    DataExtractor data;
    data.SetData(data_sp, data_offset, length);
    if (ObjectContainerUniversalMachO::MagicBytesMatch(data)) {
      std::unique_ptr<ObjectContainerUniversalMachO> container_up(
          new ObjectContainerUniversalMachO(module_sp, data_sp, data_offset,
                                            file, file_offset, length));
      if (container_up->ParseHeader()) {
        return container_up.release();
      }
    }
  }
  return nullptr;
}
 
bool ObjectContainerUniversalMachO::MagicBytesMatch(const DataExtractor &data) {
  lldb::offset_t offset = 0;
  uint32_t magic = data.GetU32(&offset);
  return magic == FAT_MAGIC || magic == FAT_CIGAM || magic == FAT_MAGIC_64 ||
         magic == FAT_CIGAM_64;
}
 
ObjectContainerUniversalMachO::ObjectContainerUniversalMachO(
    const lldb::ModuleSP &module_sp, DataBufferSP &data_sp,
    lldb::offset_t data_offset, const FileSpec *file,
    lldb::offset_t file_offset, lldb::offset_t length)
    : ObjectContainer(module_sp, file, file_offset, length, data_sp,
                      data_offset),
      m_header(), m_fat_archs() {
  memset(&m_header, 0, sizeof(m_header));
}
 
ObjectContainerUniversalMachO::~ObjectContainerUniversalMachO() = default;
 
bool ObjectContainerUniversalMachO::ParseHeader() {
  bool success = ParseHeader(*m_extractor_sp, m_header, m_fat_archs);
  // We no longer need any data, we parsed all we needed to parse and cached it
  // in m_header and m_fat_archs.  Need to have an empty DataExtractor for code
  // that assumes it is non-null.
  m_extractor_sp = std::make_shared<DataExtractor>();
  return success;
}
 
bool ObjectContainerUniversalMachO::ParseHeader(
    lldb_private::DataExtractor &extractor, llvm::MachO::fat_header &header,
    std::vector<FatArch> &fat_archs) {
  // Store the file offset for this universal file as we could have a universal
  // .o file in a BSD archive, or be contained in another kind of object.
  lldb::offset_t offset = 0;
  extractor.SetByteOrder(eByteOrderBig);
  header.magic = extractor.GetU32(&offset);
  fat_archs.clear();
 
  // Universal mach-o files always have their headers in big endian.
  if (header.magic == FAT_MAGIC || header.magic == FAT_MAGIC_64) {
    const bool is_fat64 = header.magic == FAT_MAGIC_64;
    extractor.SetAddressByteSize(is_fat64 ? 8 : 4);
 
    header.nfat_arch = extractor.GetU32(&offset);
 
    // Now we should have enough data for all of the fat headers, so lets index
    // them so we know how many architectures that this universal binary
    // contains.
    for (uint32_t arch_idx = 0; arch_idx < header.nfat_arch; ++arch_idx) {
      if (extractor.ValidOffsetForDataOfSize(offset, sizeof(fat_arch))) {
        if (is_fat64) {
          fat_arch_64 arch;
          arch.cputype = extractor.GetU32(&offset);
          arch.cpusubtype = extractor.GetU32(&offset);
          arch.offset = extractor.GetU64(&offset);
          arch.size = extractor.GetU64(&offset);
          arch.align = extractor.GetU32(&offset);
          arch.reserved = extractor.GetU32(&offset);
          fat_archs.emplace_back(arch);
        } else {
          fat_arch arch;
          arch.cputype = extractor.GetU32(&offset);
          arch.cpusubtype = extractor.GetU32(&offset);
          arch.offset = extractor.GetU32(&offset);
          arch.size = extractor.GetU32(&offset);
          arch.align = extractor.GetU32(&offset);
          fat_archs.emplace_back(arch);
        }
      } else {
        // nfat_arch is read from the file and is untrusted (up to 0xFFFFFFFF).
        // Once the data is exhausted the offset can no longer advance, so the
        // remaining iterations would spin uselessly; stop here.
        break;
      }
    }
    return true;
  }
 
  memset(&header, 0, sizeof(header));
  return true;
}
 
size_t ObjectContainerUniversalMachO::GetNumArchitectures() const {
  return m_header.nfat_arch;
}
 
bool ObjectContainerUniversalMachO::GetArchitectureAtIndex(
    uint32_t idx, ArchSpec &arch) const {
  if (idx < m_fat_archs.size()) {
    arch.SetArchitecture(eArchTypeMachO, m_fat_archs[idx].GetCPUType(),
                         m_fat_archs[idx].GetCPUSubType());
    return true;
  }
  return false;
}
 
ObjectFileSP
ObjectContainerUniversalMachO::GetObjectFile(const FileSpec *file) {
  uint32_t arch_idx = 0;
  ArchSpec arch;
  // If the module hasn't specified an architecture yet, set it to the default
  // architecture:
  ModuleSP module_sp(GetModule());
  if (module_sp) {
    if (!module_sp->GetArchitecture().IsValid()) {
      arch = Target::GetDefaultArchitecture();
      if (!arch.IsValid())
        arch.SetTriple(LLDB_ARCH_DEFAULT);
    } else
      arch = module_sp->GetArchitecture();
 
    ArchSpec curr_arch;
    // First, try to find an exact match for the Arch of the Target.
    for (arch_idx = 0; arch_idx < m_header.nfat_arch; ++arch_idx) {
      if (GetArchitectureAtIndex(arch_idx, curr_arch) &&
          arch.IsExactMatch(curr_arch))
        break;
    }
 
    // Failing an exact match, try to find a compatible Arch of the Target.
    if (arch_idx >= m_header.nfat_arch) {
      for (arch_idx = 0; arch_idx < m_header.nfat_arch; ++arch_idx) {
        if (GetArchitectureAtIndex(arch_idx, curr_arch) &&
            arch.IsCompatibleMatch(curr_arch))
          break;
      }
    }
 
    if (arch_idx < m_header.nfat_arch) {
      const FatArch &fat_arch = m_fat_archs[arch_idx];
      const uint64_t byte_size = GetByteSize();
      // The slice must start strictly past this container's own bytes and
      // fit within them.
      if (fat_arch.GetOffset() > 0 && fat_arch.GetOffset() < byte_size) {
        DataExtractorSP extractor_sp;
        lldb::offset_t data_offset = 0;
        const uint64_t slice_size =
            std::min(fat_arch.GetSize(), byte_size - fat_arch.GetOffset());
        return ObjectFile::FindPlugin(module_sp, file,
                                      m_offset + fat_arch.GetOffset(),
                                      slice_size, extractor_sp, data_offset);
      }
    }
  }
  return ObjectFileSP();
}
 
ModuleSpecList ObjectContainerUniversalMachO::GetModuleSpecifications(
    const lldb_private::FileSpec &file, lldb::DataExtractorSP &extractor_sp,
    lldb::offset_t file_offset, lldb::offset_t file_size) {
  if (!extractor_sp)
    return {};
 
  ModuleSpecList specs;
  if (ObjectContainerUniversalMachO::MagicBytesMatch(*extractor_sp)) {
    llvm::MachO::fat_header header;
    std::vector<FatArch> fat_archs;
    if (ParseHeader(*extractor_sp, header, fat_archs)) {
      for (const FatArch &fat_arch : fat_archs) {
        const lldb::offset_t slice_file_offset =
            fat_arch.GetOffset() + file_offset;
        // The slice must start strictly past the current offset.  A slice whose
        // offset is 0 (or otherwise does not advance) is self-referential: the
        // recursive call below would re-parse the same range and recurse
        // without bound.  Skip such slices instead of overflowing the stack.
        if (slice_file_offset > file_offset &&
            fat_arch.GetOffset() < file_size && file_size > slice_file_offset) {
          ModuleSpecList arch_specs = ObjectFile::GetModuleSpecifications(
              file, slice_file_offset, file_size - slice_file_offset);
          specs.Append(arch_specs);
        }
      }
    }
  }
  return specs;
}