path: root/system/lib/libcxxabi/src/Unwind/UnwindCursor.hpp

//===------------------------- UnwindCursor.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.
//
//
// C++ interface to lower levels of libuwind
//===----------------------------------------------------------------------===//

#ifndef __UNWINDCURSOR_HPP__
#define __UNWINDCURSOR_HPP__

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

#if __APPLE__
  #include <mach-o/dyld.h>
#endif

#include "libunwind.h"

#include "AddressSpace.hpp"
#include "Registers.hpp"
#include "DwarfInstructions.hpp"
#include "CompactUnwinder.hpp"
#include "config.h"

namespace libunwind {

#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
/// Cache of recently found FDEs.
template <typename A>
class _LIBUNWIND_HIDDEN DwarfFDECache {
  typedef typename A::pint_t pint_t;
public:
  static pint_t findFDE(pint_t mh, pint_t pc);
  static void add(pint_t mh, pint_t ip_start, pint_t ip_end, pint_t fde);
  static void removeAllIn(pint_t mh);
  static void iterateCacheEntries(void (*func)(unw_word_t ip_start,
                                               unw_word_t ip_end,
                                               unw_word_t fde, unw_word_t mh));

private:

  struct entry {
    pint_t mh;
    pint_t ip_start;
    pint_t ip_end;
    pint_t fde;
  };

  // These fields are all static to avoid needing an initializer.
  // There is only one instance of this class per process.
  static pthread_rwlock_t _lock;
#if __APPLE__
  static void dyldUnloadHook(const struct mach_header *mh, intptr_t slide);
  static bool _registeredForDyldUnloads;
#endif
  // Can't use std::vector<> here because this code is below libc++.
  static entry *_buffer;
  static entry *_bufferUsed;
  static entry *_bufferEnd;
  static entry _initialBuffer[64];
};

template <typename A>
typename DwarfFDECache<A>::entry *
DwarfFDECache<A>::_buffer = _initialBuffer;

template <typename A>
typename DwarfFDECache<A>::entry *
DwarfFDECache<A>::_bufferUsed = _initialBuffer;

template <typename A>
typename DwarfFDECache<A>::entry *
DwarfFDECache<A>::_bufferEnd = &_initialBuffer[64];

template <typename A>
typename DwarfFDECache<A>::entry DwarfFDECache<A>::_initialBuffer[64];

template <typename A>
pthread_rwlock_t DwarfFDECache<A>::_lock = PTHREAD_RWLOCK_INITIALIZER;

#if __APPLE__
template <typename A>
bool DwarfFDECache<A>::_registeredForDyldUnloads = false;
#endif

template <typename A>
typename A::pint_t DwarfFDECache<A>::findFDE(pint_t mh, pint_t pc) {
  pint_t result = 0;
  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_rdlock(&_lock));
  for (entry *p = _buffer; p < _bufferUsed; ++p) {
    if ((mh == p->mh) || (mh == 0)) {
      if ((p->ip_start <= pc) && (pc < p->ip_end)) {
        result = p->fde;
        break;
      }
    }
  }
  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_unlock(&_lock));
  return result;
}

template <typename A>
void DwarfFDECache<A>::add(pint_t mh, pint_t ip_start, pint_t ip_end,
                           pint_t fde) {
  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_wrlock(&_lock));
  if (_bufferUsed >= _bufferEnd) {
    size_t oldSize = (size_t)(_bufferEnd - _buffer);
    size_t newSize = oldSize * 4;
    // Can't use operator new (we are below it).
    entry *newBuffer = (entry *)malloc(newSize * sizeof(entry));
    memcpy(newBuffer, _buffer, oldSize * sizeof(entry));
    if (_buffer != _initialBuffer)
      free(_buffer);
    _buffer = newBuffer;
    _bufferUsed = &newBuffer[oldSize];
    _bufferEnd = &newBuffer[newSize];
  }