//===------------------------- AddressSpace.hpp ---------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//
// Abstracts accessing local vs remote address spaces.
//
//===----------------------------------------------------------------------===//

#ifndef __ADDRESSSPACE_HPP__
#define __ADDRESSSPACE_HPP__

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifndef _LIBUNWIND_USE_DLADDR
  #if !defined(_LIBUNWIND_IS_BAREMETAL) && !defined(_WIN32)
    #define _LIBUNWIND_USE_DLADDR 1
  #else
    #define _LIBUNWIND_USE_DLADDR 0
  #endif
#endif

#if _LIBUNWIND_USE_DLADDR
#include <dlfcn.h>
#endif

#ifdef __APPLE__
#include <mach-o/getsect.h>
namespace libunwind {
   bool checkKeyMgrRegisteredFDEs(uintptr_t targetAddr, void *&fde);
}
#endif

#include "libunwind.h"
#include "config.h"
#include "dwarf2.h"
#include "EHHeaderParser.hpp"
#include "Registers.hpp"

#if defined(STARBOARD_IMPLEMENTATION)
#include "starboard/memory.h"
#include "starboard/elf_loader/evergreen_info.h"
#endif

#ifdef __APPLE__

  struct dyld_unwind_sections
  {
    const struct mach_header*   mh;
    const void*                 dwarf_section;
    uintptr_t                   dwarf_section_length;
    const void*                 compact_unwind_section;
    uintptr_t                   compact_unwind_section_length;
  };
  #if (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) \
                                 && (__MAC_OS_X_VERSION_MIN_REQUIRED >= 1070)) \
      || defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
    // In 10.7.0 or later, libSystem.dylib implements this function.
    extern "C" bool _dyld_find_unwind_sections(void *, dyld_unwind_sections *);
  #else
    // In 10.6.x and earlier, we need to implement this functionality. Note
    // that this requires a newer version of libmacho (from cctools) than is
    // present in libSystem on 10.6.x (for getsectiondata).
    static inline bool _dyld_find_unwind_sections(void* addr,
                                                    dyld_unwind_sections* info) {
      // Find mach-o image containing address.
      Dl_info dlinfo;
      if (!dladdr(addr, &dlinfo))
        return false;
#if __LP64__
      const struct mach_header_64 *mh = (const struct mach_header_64 *)dlinfo.dli_fbase;
#else
      const struct mach_header *mh = (const struct mach_header *)dlinfo.dli_fbase;
#endif

      // Initialize the return struct
      info->mh = (const struct mach_header *)mh;
      info->dwarf_section = getsectiondata(mh, "__TEXT", "__eh_frame", &info->dwarf_section_length);
      info->compact_unwind_section = getsectiondata(mh, "__TEXT", "__unwind_info", &info->compact_unwind_section_length);

      if (!info->dwarf_section) {
        info->dwarf_section_length = 0;
      }

      if (!info->compact_unwind_section) {
        info->compact_unwind_section_length = 0;
      }

      return true;
    }
  #endif

#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)

// When statically linked on bare-metal, the symbols for the EH table are looked
// up without going through the dynamic loader.

// The following linker script may be used to produce the necessary sections and symbols.
// Unless the --eh-frame-hdr linker option is provided, the section is not generated
// and does not take space in the output file.
//
//   .eh_frame :
//   {
//       __eh_frame_start = .;
//       KEEP(*(.eh_frame))
//       __eh_frame_end = .;
//   }
//
//   .eh_frame_hdr :
//   {
//       KEEP(*(.eh_frame_hdr))
//   }
//
//   __eh_frame_hdr_start = SIZEOF(.eh_frame_hdr) > 0 ? ADDR(.eh_frame_hdr) : 0;
//   __eh_frame_hdr_end = SIZEOF(.eh_frame_hdr) > 0 ? . : 0;

extern char __eh_frame_start;
extern char __eh_frame_end;

#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
extern char __eh_frame_hdr_start;
extern char __eh_frame_hdr_end;
#endif

#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)

// When statically linked on bare-metal, the symbols for the EH table are looked
// up without going through the dynamic loader.
extern char __exidx_start;
extern char __exidx_end;

#elif defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

// ELF-based systems may use dl_iterate_phdr() to access sections
// containing unwinding information. The ElfW() macro for pointer-size
// independent ELF header traversal is not provided by <link.h> on some
// systems (e.g., FreeBSD). On these systems the data structures are
// just called Elf_XXX. Define ElfW() locally.
#ifndef _WIN32
#include <link.h>
#else
#include <windows.h>
#include <psapi.h>
#endif
#if !defined(ElfW)
#define ElfW(type) Elf_##type
#endif

#endif

namespace libunwind {

/// Used by findUnwindSections() to return info about needed sections.
struct UnwindInfoSections {
#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) || defined(_LIBUNWIND_SUPPORT_DWARF_INDEX) ||       \
    defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
  // No dso_base for ARM EHABI.
  uintptr_t       dso_base;
#endif
#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  uintptr_t       dwarf_section;
  uintptr_t       dwarf_section_length;
#endif
#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
  uintptr_t       dwarf_index_section;
  uintptr_t       dwarf_index_section_length;
#endif
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
  uintptr_t       compact_unwind_section;
  uintptr_t       compact_unwind_section_length;
#endif
#if defined(_LIBUNWIND_ARM_EHABI)
  uintptr_t       arm_section;
  uintptr_t       arm_section_length;
#endif
};


/// LocalAddressSpace is used as a template parameter to UnwindCursor when
/// unwinding a thread in the same process.  The wrappers compile away,
/// making local unwinds fast.
class __attribute__((visibility("hidden"))) LocalAddressSpace {
public:
  typedef uintptr_t pint_t;
  typedef intptr_t  sint_t;
  uint8_t         get8(pint_t addr) {
    uint8_t val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  uint16_t         get16(pint_t addr) {
    uint16_t val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  uint32_t         get32(pint_t addr) {
    uint32_t val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  uint64_t         get64(pint_t addr) {
    uint64_t val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  double           getDouble(pint_t addr) {
    double val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  v128             getVector(pint_t addr) {
    v128 val;
    memcpy(&val, (void *)addr, sizeof(val));
    return val;
  }
  uintptr_t       getP(pint_t addr);
  uint64_t        getRegister(pint_t addr);
  static uint64_t getULEB128(pint_t &addr, pint_t end);
  static int64_t  getSLEB128(pint_t &addr, pint_t end);

  pint_t getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
                     pint_t datarelBase = 0);
  bool findFunctionName(pint_t addr, char *buf, size_t bufLen,
                        unw_word_t *offset);
  bool findUnwindSections(pint_t targetAddr, UnwindInfoSections &info);
  bool findOtherFDE(pint_t targetAddr, pint_t &fde);

  static LocalAddressSpace sThisAddressSpace;
};

inline uintptr_t LocalAddressSpace::getP(pint_t addr) {
#if __SIZEOF_POINTER__ == 8
  return get64(addr);
#else
  return get32(addr);
#endif
}

inline uint64_t LocalAddressSpace::getRegister(pint_t addr) {
#if __SIZEOF_POINTER__ == 8 || defined(__mips64)
  return get64(addr);
#else
  return get32(addr);
#endif
}

/// Read a ULEB128 into a 64-bit word.
inline uint64_t LocalAddressSpace::getULEB128(pint_t &addr, pint_t end) {
  const uint8_t *p = (uint8_t *)addr;
  const uint8_t *pend = (uint8_t *)end;
  uint64_t result = 0;
  int bit = 0;
  do {
    uint64_t b;

    if (p == pend)
      _LIBUNWIND_ABORT("truncated uleb128 expression");

    b = *p & 0x7f;

    if (bit >= 64 || b << bit >> bit != b) {
      _LIBUNWIND_ABORT("malformed uleb128 expression");
    } else {
      result |= b << bit;
      bit += 7;
    }
  } while (*p++ >= 0x80);
  addr = (pint_t) p;
  return result;
}

/// Read a SLEB128 into a 64-bit word.
inline int64_t LocalAddressSpace::getSLEB128(pint_t &addr, pint_t end) {
  const uint8_t *p = (uint8_t *)addr;
  const uint8_t *pend = (uint8_t *)end;
  int64_t result = 0;
  int bit = 0;
  uint8_t byte;
  do {
    if (p == pend)
      _LIBUNWIND_ABORT("truncated sleb128 expression");
    byte = *p++;
    result |= ((byte & 0x7f) << bit);
    bit += 7;
  } while (byte & 0x80);
  // sign extend negative numbers
  if ((byte & 0x40) != 0)
    result |= (-1ULL) << bit;
  addr = (pint_t) p;
  return result;
}

inline LocalAddressSpace::pint_t
LocalAddressSpace::getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
                               pint_t datarelBase) {
  pint_t startAddr = addr;
  const uint8_t *p = (uint8_t *)addr;
  pint_t result;

  // first get value
  switch (encoding & 0x0F) {
  case DW_EH_PE_ptr:
    result = getP(addr);
    p += sizeof(pint_t);
    addr = (pint_t) p;
    break;
  case DW_EH_PE_uleb128:
    result = (pint_t)getULEB128(addr, end);
    break;
  case DW_EH_PE_udata2:
    result = get16(addr);
    p += 2;
    addr = (pint_t) p;
    break;
  case DW_EH_PE_udata4:
    result = get32(addr);
    p += 4;
    addr = (pint_t) p;
    break;
  case DW_EH_PE_udata8:
    result = (pint_t)get64(addr);
    p += 8;
    addr = (pint_t) p;
    break;
  case DW_EH_PE_sleb128:
    result = (pint_t)getSLEB128(addr, end);
    break;
  case DW_EH_PE_sdata2:
    // Sign extend from signed 16-bit value.
    result = (pint_t)(int16_t)get16(addr);
    p += 2;
    addr = (pint_t) p;
    break;
  case DW_EH_PE_sdata4:
    // Sign extend from signed 32-bit value.
    result = (pint_t)(int32_t)get32(addr);
    p += 4;
    addr = (pint_t) p;
    break;
  case DW_EH_PE_sdata8:
    result = (pint_t)get64(addr);
    p += 8;
    addr = (pint_t) p;
    break;
  default:
    _LIBUNWIND_ABORT("unknown pointer encoding");
  }

  // then add relative offset
  switch (encoding & 0x70) {
  case DW_EH_PE_absptr:
    // do nothing
    break;
  case DW_EH_PE_pcrel:
    result += startAddr;
    break;
  case DW_EH_PE_textrel:
    _LIBUNWIND_ABORT("DW_EH_PE_textrel pointer encoding not supported");
    break;
  case DW_EH_PE_datarel:
    // DW_EH_PE_datarel is only valid in a few places, so the parameter has a
    // default value of 0, and we abort in the event that someone calls this
    // function with a datarelBase of 0 and DW_EH_PE_datarel encoding.
    if (datarelBase == 0)
      _LIBUNWIND_ABORT("DW_EH_PE_datarel is invalid with a datarelBase of 0");
    result += datarelBase;
    break;
  case DW_EH_PE_funcrel:
    _LIBUNWIND_ABORT("DW_EH_PE_funcrel pointer encoding not supported");
    break;
  case DW_EH_PE_aligned:
    _LIBUNWIND_ABORT("DW_EH_PE_aligned pointer encoding not supported");
    break;
  default:
    _LIBUNWIND_ABORT("unknown pointer encoding");
    break;
  }

  if (encoding & DW_EH_PE_indirect)
    result = getP(result);

  return result;
}

#if defined(STARBOARD)
#if !defined(Elf_Half)
        typedef ElfW(Half) Elf_Half;
#endif
#if !defined(Elf_Phdr)
        typedef ElfW(Phdr) Elf_Phdr;
#endif
#if !defined(Elf_Addr) && defined(__ANDROID__)
        typedef ElfW(Addr) Elf_Addr;
#endif
#endif

#if defined(STARBOARD_IMPLEMENTATION)
int evergreen_dl_iterate_phdr(
                 int (*callback) (struct dl_phdr_info *info,
                                  size_t size, void *data),
                 void *data) {
  bool ret = false;
  EvergreenInfo evergreen_info;
  if(GetEvergreenInfo(&evergreen_info)) {
    struct dl_phdr_info info;
    info.dlpi_addr =  evergreen_info.base_address;
    info.dlpi_name = evergreen_info.file_path_buf;
    info.dlpi_phdr = reinterpret_cast<Elf_Phdr*>(evergreen_info.phdr_table);
    info.dlpi_phnum = evergreen_info.phdr_table_num;
    ret = callback(&info, sizeof(info), data);
  }

  return ret || ::dl_iterate_phdr(callback, data);
}
#endif
inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
                                                  UnwindInfoSections &info) {

#if defined(STARBOARD) && !defined(STARBOARD_IMPLEMENTATION)
  return false;
#endif


#ifdef __APPLE__
  dyld_unwind_sections dyldInfo;
  if (_dyld_find_unwind_sections((void *)targetAddr, &dyldInfo)) {
    info.dso_base                      = (uintptr_t)dyldInfo.mh;
 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
    info.dwarf_section                 = (uintptr_t)dyldInfo.dwarf_section;
    info.dwarf_section_length          = dyldInfo.dwarf_section_length;
 #endif
    info.compact_unwind_section        = (uintptr_t)dyldInfo.compact_unwind_section;
    info.compact_unwind_section_length = dyldInfo.compact_unwind_section_length;
    return true;
  }
#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
  // Bare metal is statically linked, so no need to ask the dynamic loader
  info.dwarf_section_length = (uintptr_t)(&__eh_frame_end - &__eh_frame_start);
  info.dwarf_section =        (uintptr_t)(&__eh_frame_start);
  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
                             (void *)info.dwarf_section, (void *)info.dwarf_section_length);
#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
  info.dwarf_index_section =        (uintptr_t)(&__eh_frame_hdr_start);
  info.dwarf_index_section_length = (uintptr_t)(&__eh_frame_hdr_end - &__eh_frame_hdr_start);
  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: index section %p length %p",
                             (void *)info.dwarf_index_section, (void *)info.dwarf_index_section_length);
#endif
  if (info.dwarf_section_length)
    return true;
#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
  // Bare metal is statically linked, so no need to ask the dynamic loader
  info.arm_section =        (uintptr_t)(&__exidx_start);
  info.arm_section_length = (uintptr_t)(&__exidx_end - &__exidx_start);
  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
                             (void *)info.arm_section, (void *)info.arm_section_length);
  if (info.arm_section && info.arm_section_length)
    return true;
#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_WIN32)
  HMODULE mods[1024];
  HANDLE process = GetCurrentProcess();
  DWORD needed;

  if (!EnumProcessModules(process, mods, sizeof(mods), &needed))
    return false;

  for (unsigned i = 0; i < (needed / sizeof(HMODULE)); i++) {
    PIMAGE_DOS_HEADER pidh = (PIMAGE_DOS_HEADER)mods[i];
    PIMAGE_NT_HEADERS pinh = (PIMAGE_NT_HEADERS)((BYTE *)pidh + pidh->e_lfanew);
    PIMAGE_FILE_HEADER pifh = (PIMAGE_FILE_HEADER)&pinh->FileHeader;
    PIMAGE_SECTION_HEADER pish = IMAGE_FIRST_SECTION(pinh);
    bool found_obj = false;
    bool found_hdr = false;

    info.dso_base = (uintptr_t)mods[i];
    for (unsigned j = 0; j < pifh->NumberOfSections; j++, pish++) {
      uintptr_t begin = pish->VirtualAddress + (uintptr_t)mods[i];
      uintptr_t end = begin + pish->Misc.VirtualSize;
      if (!strncmp((const char *)pish->Name, ".text",
                   IMAGE_SIZEOF_SHORT_NAME)) {
        if (targetAddr >= begin && targetAddr < end)
          found_obj = true;
      } else if (!strncmp((const char *)pish->Name, ".eh_frame",
                          IMAGE_SIZEOF_SHORT_NAME)) {
        info.dwarf_section = begin;
        info.dwarf_section_length = pish->Misc.VirtualSize;
        found_hdr = true;
      }
      if (found_obj && found_hdr)
        return true;
    }
  }
  return false;
#elif defined(_LIBUNWIND_ARM_EHABI) && defined(__BIONIC__) &&                  \
    (__ANDROID_API__ < 21)
  int length = 0;
  info.arm_section =
      (uintptr_t)dl_unwind_find_exidx((_Unwind_Ptr)targetAddr, &length);
  info.arm_section_length = (uintptr_t)length;
  if (info.arm_section && info.arm_section_length)
    return true;
#elif defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  struct dl_iterate_cb_data {
    LocalAddressSpace *addressSpace;
    UnwindInfoSections *sects;
    uintptr_t targetAddr;
  };

  dl_iterate_cb_data cb_data = {this, &info, targetAddr};
#if defined(STARBOARD_IMPLEMENTATION)
  int found = evergreen_dl_iterate_phdr(
#else
  int found = dl_iterate_phdr(
#endif
      [](struct dl_phdr_info *pinfo, size_t, void *data) -> int {
        auto cbdata = static_cast<dl_iterate_cb_data *>(data);
        bool found_obj = false;
        bool found_hdr = false;

        assert(cbdata);
        assert(cbdata->sects);

        if (cbdata->targetAddr < pinfo->dlpi_addr) {
          return false;
        }
#if !defined(STARBOARD)
#if !defined(Elf_Half)
        typedef ElfW(Half) Elf_Half;
#endif
#if !defined(Elf_Phdr)
        typedef ElfW(Phdr) Elf_Phdr;
#endif
#if !defined(Elf_Addr) && defined(__ANDROID__)
        typedef ElfW(Addr) Elf_Addr;
#endif
#endif

 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  #if !defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
   #error "_LIBUNWIND_SUPPORT_DWARF_UNWIND requires _LIBUNWIND_SUPPORT_DWARF_INDEX on this platform."
  #endif
        size_t object_length;
#if defined(__ANDROID__)
        Elf_Addr image_base =
            pinfo->dlpi_phnum
                ? reinterpret_cast<Elf_Addr>(pinfo->dlpi_phdr) -
                      reinterpret_cast<const Elf_Phdr *>(pinfo->dlpi_phdr)
                          ->p_offset
                : 0;
#endif

        for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
          const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
          if (phdr->p_type == PT_LOAD) {
            uintptr_t begin = pinfo->dlpi_addr + phdr->p_vaddr;
#if defined(__ANDROID__)
            if (pinfo->dlpi_addr == 0 && phdr->p_vaddr < image_base)
              begin = begin + image_base;
#endif
            uintptr_t end = begin + phdr->p_memsz;
            if (cbdata->targetAddr >= begin && cbdata->targetAddr < end) {
              cbdata->sects->dso_base = begin;
              object_length = phdr->p_memsz;
              found_obj = true;
            }
          } else if (phdr->p_type == PT_GNU_EH_FRAME) {
            EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
            uintptr_t eh_frame_hdr_start = pinfo->dlpi_addr + phdr->p_vaddr;
#if defined(__ANDROID__)
            if (pinfo->dlpi_addr == 0 && phdr->p_vaddr < image_base)
              eh_frame_hdr_start = eh_frame_hdr_start + image_base;
#endif
            cbdata->sects->dwarf_index_section = eh_frame_hdr_start;
            cbdata->sects->dwarf_index_section_length = phdr->p_memsz;
            found_hdr = EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
                *cbdata->addressSpace, eh_frame_hdr_start, phdr->p_memsz,
                hdrInfo);
            if (found_hdr)
              cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
          }
        }

        if (found_obj && found_hdr) {
          cbdata->sects->dwarf_section_length = object_length;
          return true;
        } else {
          return false;
        }
 #else // defined(_LIBUNWIND_ARM_EHABI)
        for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
          const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
          if (phdr->p_type == PT_LOAD) {
            uintptr_t begin = pinfo->dlpi_addr + phdr->p_vaddr;
            uintptr_t end = begin + phdr->p_memsz;
            if (cbdata->targetAddr >= begin && cbdata->targetAddr < end)
              found_obj = true;
          } else if (phdr->p_type == PT_ARM_EXIDX) {
            uintptr_t exidx_start = pinfo->dlpi_addr + phdr->p_vaddr;
            cbdata->sects->arm_section = exidx_start;
            cbdata->sects->arm_section_length = phdr->p_memsz;
            found_hdr = true;
          }
        }
        return found_obj && found_hdr;
 #endif
      },
      &cb_data);
  return static_cast<bool>(found);
#endif

  return false;
}


inline bool LocalAddressSpace::findOtherFDE(pint_t targetAddr, pint_t &fde) {
#ifdef __APPLE__
  return checkKeyMgrRegisteredFDEs(targetAddr, *((void**)&fde));
#else
  // TO DO: if OS has way to dynamically register FDEs, check that.
  (void)targetAddr;
  (void)fde;
  return false;
#endif
}

inline bool LocalAddressSpace::findFunctionName(pint_t addr, char *buf,
                                                size_t bufLen,
                                                unw_word_t *offset) {
#if !defined(STARBOARD)
#if _LIBUNWIND_USE_DLADDR
  Dl_info dyldInfo;
  if (dladdr((void *)addr, &dyldInfo)) {
    if (dyldInfo.dli_sname != NULL) {
      snprintf(buf, bufLen, "%s", dyldInfo.dli_sname);
      *offset = (addr - (pint_t) dyldInfo.dli_saddr);
      return true;
    }
  }
#endif
#endif
  return false;
}


#ifdef UNW_REMOTE

/// RemoteAddressSpace is used as a template parameter to UnwindCursor when
/// unwinding a thread in the another process.  The other process can be a
/// different endianness and a different pointer size which is handled by
/// the P template parameter.
template <typename P>
class RemoteAddressSpace {
public:
  RemoteAddressSpace(task_t task) : fTask(task) {}

  typedef typename P::uint_t pint_t;

  uint8_t   get8(pint_t addr);
  uint16_t  get16(pint_t addr);
  uint32_t  get32(pint_t addr);
  uint64_t  get64(pint_t addr);
  pint_t    getP(pint_t addr);
  uint64_t  getRegister(pint_t addr);
  uint64_t  getULEB128(pint_t &addr, pint_t end);
  int64_t   getSLEB128(pint_t &addr, pint_t end);
  pint_t    getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
                        pint_t datarelBase = 0);
  bool      findFunctionName(pint_t addr, char *buf, size_t bufLen,
                        unw_word_t *offset);
  bool      findUnwindSections(pint_t targetAddr, UnwindInfoSections &info);
  bool      findOtherFDE(pint_t targetAddr, pint_t &fde);
private:
  void *localCopy(pint_t addr);

  task_t fTask;
};

template <typename P> uint8_t RemoteAddressSpace<P>::get8(pint_t addr) {
  return *((uint8_t *)localCopy(addr));
}

template <typename P> uint16_t RemoteAddressSpace<P>::get16(pint_t addr) {
  return P::E::get16(*(uint16_t *)localCopy(addr));
}

template <typename P> uint32_t RemoteAddressSpace<P>::get32(pint_t addr) {
  return P::E::get32(*(uint32_t *)localCopy(addr));
}

template <typename P> uint64_t RemoteAddressSpace<P>::get64(pint_t addr) {
  return P::E::get64(*(uint64_t *)localCopy(addr));
}

template <typename P>
typename P::uint_t RemoteAddressSpace<P>::getP(pint_t addr) {
  return P::getP(*(uint64_t *)localCopy(addr));
}

template <typename P>
typename P::uint_t OtherAddressSpace<P>::getRegister(pint_t addr) {
  return P::getRegister(*(uint64_t *)localCopy(addr));
}

template <typename P>
uint64_t OtherAddressSpace<P>::getULEB128(pint_t &addr, pint_t end) {
  uintptr_t size = (end - addr);
  LocalAddressSpace::pint_t laddr = (LocalAddressSpace::pint_t) localCopy(addr);
  LocalAddressSpace::pint_t sladdr = laddr;
  uint64_t result = LocalAddressSpace::getULEB128(laddr, laddr + size);
  addr += (laddr - sladdr);
  return result;
}

template <typename P>
int64_t RemoteAddressSpace<P>::getSLEB128(pint_t &addr, pint_t end) {
  uintptr_t size = (end - addr);
  LocalAddressSpace::pint_t laddr = (LocalAddressSpace::pint_t) localCopy(addr);
  LocalAddressSpace::pint_t sladdr = laddr;
  uint64_t result = LocalAddressSpace::getSLEB128(laddr, laddr + size);
  addr += (laddr - sladdr);
  return result;
}

template <typename P> void *RemoteAddressSpace<P>::localCopy(pint_t addr) {
  // FIX ME
}

template <typename P>
bool RemoteAddressSpace<P>::findFunctionName(pint_t addr, char *buf,
                                             size_t bufLen,
                                             unw_word_t *offset) {
  // FIX ME
}

/// unw_addr_space is the base class that abstract unw_addr_space_t type in
/// libunwind.h points to.
struct unw_addr_space {
  cpu_type_t cpuType;
  task_t taskPort;
};

/// unw_addr_space_i386 is the concrete instance that a unw_addr_space_t points
/// to when examining
/// a 32-bit intel process.
struct unw_addr_space_i386 : public unw_addr_space {
  unw_addr_space_i386(task_t task) : oas(task) {}
  RemoteAddressSpace<Pointer32<LittleEndian>> oas;
};

/// unw_addr_space_x86_64 is the concrete instance that a unw_addr_space_t
/// points to when examining
/// a 64-bit intel process.
struct unw_addr_space_x86_64 : public unw_addr_space {
  unw_addr_space_x86_64(task_t task) : oas(task) {}
  RemoteAddressSpace<Pointer64<LittleEndian>> oas;
};

/// unw_addr_space_ppc is the concrete instance that a unw_addr_space_t points
/// to when examining
/// a 32-bit PowerPC process.
struct unw_addr_space_ppc : public unw_addr_space {
  unw_addr_space_ppc(task_t task) : oas(task) {}
  RemoteAddressSpace<Pointer32<BigEndian>> oas;
};

/// unw_addr_space_ppc is the concrete instance that a unw_addr_space_t points
/// to when examining a 64-bit PowerPC process.
struct unw_addr_space_ppc64 : public unw_addr_space {
  unw_addr_space_ppc64(task_t task) : oas(task) {}
  RemoteAddressSpace<Pointer64<LittleEndian>> oas;
};

#endif // UNW_REMOTE

} // namespace libunwind

#endif // __ADDRESSSPACE_HPP__