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deps/libffi/src/closures.c  view on Meta::CPAN

#ifdef HAVE_MNTENT
  { open_temp_exec_file_mnt, "/etc/mtab", 1 },
  { open_temp_exec_file_mnt, "/proc/mounts", 1 },
#endif /* HAVE_MNTENT */
};

/* Current index into open_temp_exec_file_opts.  */
static int open_temp_exec_file_opts_idx = 0;

/* Reset a current multi-call func, then advances to the next entry.
   If we're at the last, go back to the first and return nonzero,
   otherwise return zero.  */
static int
open_temp_exec_file_opts_next (void)
{
  if (open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat)
    open_temp_exec_file_opts[open_temp_exec_file_opts_idx].func (NULL);

  open_temp_exec_file_opts_idx++;
  if (open_temp_exec_file_opts_idx
      == (sizeof (open_temp_exec_file_opts)
	  / sizeof (*open_temp_exec_file_opts)))
    {
      open_temp_exec_file_opts_idx = 0;
      return 1;
    }

  return 0;
}

/* Return a file descriptor of a temporary zero-sized file in a
   writable and executable filesystem.  */
static int
open_temp_exec_file (void)
{
  int fd;

  do
    {
      fd = open_temp_exec_file_opts[open_temp_exec_file_opts_idx].func
	(open_temp_exec_file_opts[open_temp_exec_file_opts_idx].arg);

      if (!open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat
	  || fd == -1)
	{
	  if (open_temp_exec_file_opts_next ())
	    break;
	}
    }
  while (fd == -1);

  return fd;
}

/* Map in a chunk of memory from the temporary exec file into separate
   locations in the virtual memory address space, one writable and one
   executable.  Returns the address of the writable portion, after
   storing an offset to the corresponding executable portion at the
   last word of the requested chunk.  */
static void *
dlmmap_locked (void *start, size_t length, int prot, int flags, off_t offset)
{
  void *ptr;

  if (execfd == -1)
    {
      open_temp_exec_file_opts_idx = 0;
    retry_open:
      execfd = open_temp_exec_file ();
      if (execfd == -1)
	return MFAIL;
    }

  offset = execsize;

  if (ftruncate (execfd, offset + length))
    return MFAIL;

  flags &= ~(MAP_PRIVATE | MAP_ANONYMOUS);
  flags |= MAP_SHARED;

  ptr = mmap (NULL, length, (prot & ~PROT_WRITE) | PROT_EXEC,
	      flags, execfd, offset);
  if (ptr == MFAIL)
    {
      if (!offset)
	{
	  close (execfd);
	  goto retry_open;
	}
      ftruncate (execfd, offset);
      return MFAIL;
    }
  else if (!offset
	   && open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat)
    open_temp_exec_file_opts_next ();

  start = mmap (start, length, prot, flags, execfd, offset);

  if (start == MFAIL)
    {
      munmap (ptr, length);
      ftruncate (execfd, offset);
      return start;
    }

  mmap_exec_offset ((char *)start, length) = (char*)ptr - (char*)start;

  execsize += length;

  return start;
}

/* Map in a writable and executable chunk of memory if possible.
   Failing that, fall back to dlmmap_locked.  */
static void *
dlmmap (void *start, size_t length, int prot,
	int flags, int fd, off_t offset)
{
  void *ptr;

  assert (start == NULL && length % malloc_getpagesize == 0
	  && prot == (PROT_READ | PROT_WRITE)
	  && flags == (MAP_PRIVATE | MAP_ANONYMOUS)
	  && fd == -1 && offset == 0);

#if FFI_CLOSURE_TEST
  printf ("mapping in %zi\n", length);
#endif

  if (execfd == -1 && is_emutramp_enabled ())
    {
      ptr = mmap (start, length, prot & ~PROT_EXEC, flags, fd, offset);
      return ptr;
    }

  if (execfd == -1 && !is_selinux_enabled ())
    {
      ptr = mmap (start, length, prot | PROT_EXEC, flags, fd, offset);

      if (ptr != MFAIL || (errno != EPERM && errno != EACCES))
	/* Cool, no need to mess with separate segments.  */
	return ptr;

      /* If MREMAP_DUP is ever introduced and implemented, try mmap
	 with ((prot & ~PROT_WRITE) | PROT_EXEC) and mremap with
	 MREMAP_DUP and prot at this point.  */
    }

  if (execsize == 0 || execfd == -1)
    {
      pthread_mutex_lock (&open_temp_exec_file_mutex);
      ptr = dlmmap_locked (start, length, prot, flags, offset);
      pthread_mutex_unlock (&open_temp_exec_file_mutex);

      return ptr;
    }

  return dlmmap_locked (start, length, prot, flags, offset);
}

/* Release memory at the given address, as well as the corresponding
   executable page if it's separate.  */
static int
dlmunmap (void *start, size_t length)
{
  /* We don't bother decreasing execsize or truncating the file, since
     we can't quite tell whether we're unmapping the end of the file.
     We don't expect frequent deallocation anyway.  If we did, we
     could locate pages in the file by writing to the pages being
     deallocated and checking that the file contents change.
     Yuck.  */
  msegmentptr seg = segment_holding (gm, start);
  void *code;

#if FFI_CLOSURE_TEST
  printf ("unmapping %zi\n", length);
#endif

  if (seg && (code = add_segment_exec_offset (start, seg)) != start)
    {
      int ret = munmap (code, length);
      if (ret)
	return ret;
    }

  return munmap (start, length);
}

#if FFI_CLOSURE_FREE_CODE
/* Return segment holding given code address.  */
static msegmentptr
segment_holding_code (mstate m, char* addr)
{
  msegmentptr sp = &m->seg;
  for (;;) {
    if (addr >= add_segment_exec_offset (sp->base, sp)
	&& addr < add_segment_exec_offset (sp->base, sp) + sp->size)
      return sp;
    if ((sp = sp->next) == 0)
      return 0;
  }
}
#endif

#endif /* !(defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)) || defined (__CYGWIN__) || defined(__INTERIX) */

/* Allocate a chunk of memory with the given size.  Returns a pointer
   to the writable address, and sets *CODE to the executable
   corresponding virtual address.  */
void *
ffi_closure_alloc (size_t size, void **code)
{
  void *ptr;

  if (!code)
    return NULL;

  ptr = dlmalloc (size);