path: root/elf/dl-close.c

/* Close a shared object opened by `_dl_open'.
   Copyright (C) 1996-2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <dlfcn.h>
#include <errno.h>
#include <libintl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <libc-lock.h>
#include <ldsodefs.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sysdep-cancel.h>
#include <tls.h>
#include <stap-probe.h>
#include <dl-find_object.h>

#include <dl-unmap-segments.h>

/* Special l_idx value used to indicate which objects remain loaded.  */
#define IDX_STILL_USED -1


/* Returns true we an non-empty was found.  */
static bool
remove_slotinfo (size_t idx, struct dtv_slotinfo_list *listp, size_t disp,
		 bool should_be_there)
{
  if (idx - disp >= listp->len)
    {
      if (listp->next == NULL)
	{
	  /* The index is not actually valid in the slotinfo list,
	     because this object was closed before it was fully set
	     up due to some error.  */
	  assert (! should_be_there);
	}
      else
	{
	  if (remove_slotinfo (idx, listp->next, disp + listp->len,
			       should_be_there))
	    return true;

	  /* No non-empty entry.  Search from the end of this element's
	     slotinfo array.  */
	  idx = disp + listp->len;
	}
    }
  else
    {
      struct link_map *old_map = listp->slotinfo[idx - disp].map;

      /* The entry might still be in its unused state if we are closing an
	 object that wasn't fully set up.  */
      if (__glibc_likely (old_map != NULL))
	{
	  /* Mark the entry as unused.  These can be read concurrently.  */
	  atomic_store_relaxed (&listp->slotinfo[idx - disp].gen,
				GL(dl_tls_generation) + 1);
	  atomic_store_relaxed (&listp->slotinfo[idx - disp].map, NULL);
	}

      /* If this is not the last currently used entry no need to look
	 further.  */
      if (idx != GL(dl_tls_max_dtv_idx))
	{
	  /* There is an unused dtv entry in the middle.  */
	  GL(dl_tls_dtv_gaps) = true;
	  return true;
	}
    }

  while (idx -