/* Sort array of link maps according to dependencies.

   Copyright (C) 2017-2018 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

   <http://www.gnu.org/licenses/>.  */

#include <ldsodefs.h>

/* Sort array MAPS according to dependencies of the contained objects.

   Array USED, if non-NULL, is permutated along MAPS.  If FOR_FINI this is

   called for finishing an object.  */

void

_dl_sort_maps (struct link_map **maps, unsigned int nmaps, char *used,

	       bool for_fini)

{

  /* A list of one element need not be sorted.  */

  if (nmaps <= 1)

    return;

  unsigned int i = 0;

  uint16_t seen[nmaps];

  memset (seen, 0, nmaps * sizeof (seen[0]));

  while (1)

    {

      /* Keep track of which object we looked at this round.  */

      ++seen[i];

      struct link_map *thisp = maps[i];

      if (__glibc_unlikely (for_fini))

	{

	  /* Do not handle ld.so in secondary namespaces and objects which

	     are not removed.  */

	  if (thisp != thisp->l_real || thisp->l_idx == -1)

	    goto skip;

	}

      /* Find the last object in the list for which the current one is

	 a dependency and move the current object behind the object

	 with the dependency.  */

      unsigned int k = nmaps - 1;

      while (k > i)

	{

	  struct link_map **runp = maps[k]->l_initfini;

	  if (runp != NULL)

	    /* Look through the dependencies of the object.  */

	    while (*runp != NULL)

	      if (__glibc_unlikely (*runp++ == thisp))

		{

		move:

		  /* Move the current object to the back past the last

		     object with it as the dependency.  */

		  memmove (&maps[i], &maps[i + 1],

			   (k - i) * sizeof (maps[0]));

		  maps[k] = thisp;

		  if (used != NULL)

		    {

		      char here_used = used[i];

		      memmove (&used[i], &used[i + 1],

			       (k - i) * sizeof (used[0]));

		      used[k] = here_used;

		    }

		  if (seen[i + 1] > nmaps - i)

		    {

		      ++i;

		      goto next_clear;

		    }

		  uint16_t this_seen = seen[i];

		  memmove (&seen[i], &seen[i + 1], (k - i) * sizeof (seen[0]));

		  seen[k] = this_seen;

		  goto next;

		}

	  if (__glibc_unlikely (for_fini && maps[k]->l_reldeps != NULL))

	    {

	      unsigned int m = maps[k]->l_reldeps->act;

	      struct link_map **relmaps = &maps[k]->l_reldeps->list[0];

	      /* Look through the relocation dependencies of the object.  */

	      while (m-- > 0)

		if (__glibc_unlikely (relmaps[m] == thisp))

		  {

		    /* If a cycle exists with a link time dependency,

		       preserve the latter.  */

		    struct link_map **runp = thisp->l_initfini;

		    if (runp != NULL)

		      while (*runp != NULL)

			if (__glibc_unlikely (*runp++ == maps[k]))

			  goto ignore;

		    goto move;

		  }

	    ignore:;

	    }

	  --k;

	}

    skip:

      if (++i == nmaps)

	break;

    next_clear:

      memset (&seen[i], 0, (nmaps - i) * sizeof (seen[0]));

    next:;

    }

}