glibc/elf/dl-version.c

/* Handle symbol and library versioning.
   Copyright (C) 1997-2021 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 <elf.h>
#include <errno.h>
#include <libintl.h>
#include <stdlib.h>
#include <string.h>
#include <ldsodefs.h>
#include <_itoa.h>

#include <assert.h>

static inline struct link_map *
__attribute ((always_inline))
find_needed (const char *name, struct link_map *map)
{
  struct link_map *tmap;
  unsigned int n;

  for (tmap = GL(dl_ns)[map->l_ns]._ns_loaded; tmap != NULL;
       tmap = tmap->l_next)
    if (_dl_name_match_p (name, tmap))
      return tmap;

  /* The required object is not in the global scope, look to see if it is
     a dependency of the current object.  */
  for (n = 0; n < map->l_searchlist.r_nlist; n++)
    if (_dl_name_match_p (name, map->l_searchlist.r_list[n]))
      return map->l_searchlist.r_list[n];

  /* Should never happen.  */
  return NULL;
}


static int
match_symbol (const char *name, Lmid_t ns, ElfW(Word) hash, const char *string,
	      struct link_map *map, int verbose, int weak)
{
  const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
  ElfW(Addr) def_offset;
  ElfW(Verdef) *def;
  /* Initialize to make the compiler happy.  */
  int result = 0;
  struct dl_exception exception;

  /* Display information about what we are doing while debugging.  */
  if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_VERSIONS))
    _dl_debug_printf ("\
checking for version `%s' in file %s [%lu] required by file %s [%lu]\n",
		      string, DSO_FILENAME (map->l_name),
		      map->l_ns, name, ns);

  if (__glibc_unlikely (map->l_info[VERSYMIDX (DT_VERDEF)] == NULL))
    {
      /* The file has no symbol versioning.  I.e., the dependent
	 object was linked against another version of this file.  We
	 only print a message if verbose output is requested.  */
      if (verbose)
	{
	  /* XXX We cannot translate the messages.  */
	  _dl_exception_create_format
	    (&exception, DSO_FILENAME (map->l_name),
	     "no version information available (required by %s)", name);
	  goto call_cerror;
	}
      return 0;
    }

  def_offset = map->l_info[VERSYMIDX (DT_VERDEF)]->d_un.d_ptr;
  assert (def_offset != 0);

  def = (ElfW(Verdef) *) ((char *) map->l_addr + def_offset);
  while (1)
    {
      /* Currently the version number of the definition entry is 1.
	 Make sure all we see is this version.  */
      if (__builtin_expect (def->vd_version, 1) != 1)
	{
	  char buf[20];
	  buf[sizeof (buf) - 1] = '\0';
	  /* XXX We cannot translate the message.  */
	  _dl_exception_create_format
	    (&exception, DSO_FILENAME (map->l_name),
	     "unsupported version %s of Verdef record",
	     _itoa (def->vd_version, &buf[sizeof (buf) - 1], 10, 0));
	  result = 1;
	  goto call_cerror;
	}

      /* Compare the hash values.  */
      if (hash == def->vd_hash)
	{
	  ElfW(Verdaux) *aux = (ElfW(Verdaux) *) ((char *) def + def->vd_aux);

	  /* To be safe, compare the string as well.  */
	  if (__builtin_expect (strcmp (string, strtab + aux->vda_name), 0)
	      == 0)
	    /* Bingo!  */
	    return 0;
	}

      /* If no more definitions we failed to find what we want.  */
      if (def->vd_next == 0)
	break;

      /* Next definition.  */
      def = (ElfW(Verdef) *) ((char *) def + def->vd_next);
    }

  /* Symbol not found.  If it was a weak reference it is not fatal.  */
  if (__glibc_likely (weak))
    {
      if (verbose)
	{
	  /* XXX We cannot translate the message.  */
	  _dl_exception_create_format
	    (&exception, DSO_FILENAME (map->l_name),
	     "weak version `%s' not found (required by %s)", string, name);
	  goto call_cerror;
	}
      return 0;
    }

  /* XXX We cannot translate the message.  */
  _dl_exception_create_format
    (&exception, DSO_FILENAME (map->l_name),
     "version `%s' not found (required by %s)", string, name);
  result = 1;
 call_cerror:
  _dl_signal_cexception (0, &exception, N_("version lookup error"));
  _dl_exception_free (&exception);
  return result;
}


int
_dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
{
  int result = 0;
  const char *strtab;
  /* Pointer to section with needed versions.  */
  ElfW(Dyn) *dyn;
  /* Pointer to dynamic section with definitions.  */
  ElfW(Dyn) *def;
  /* We need to find out which is the highest version index used
    in a dependecy.  */
  unsigned int ndx_high = 0;
  struct dl_exception exception;
  /* Initialize to make the compiler happy.  */
  int errval = 0;

  /* If we don't have a string table, we must be ok.  */
  if (map->l_info[DT_STRTAB] == NULL)
    return 0;
  strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);

  dyn = map->l_info[VERSYMIDX (DT_VERNEED)];
  def = map->l_info[VERSYMIDX (DT_VERDEF)];

  if (dyn != NULL)
    {
      /* This file requires special versions from its dependencies.  */
      ElfW(Verneed) *ent = (ElfW(Verneed) *) (map->l_addr + dyn->d_un.d_ptr);

      /* Currently the version number of the needed entry is 1.
	 Make sure all we see is this version.  */
      if (__builtin_expect (ent->vn_version, 1) != 1)
	{
	  char buf[20];
	  buf[sizeof (buf) - 1] = '\0';
	  /* XXX We cannot translate the message.  */
	  _dl_exception_create_format
	    (&exception, DSO_FILENAME (map->l_name),
	     "unsupported version %s of Verneed record",
	     _itoa (ent->vn_version, &buf[sizeof (buf) - 1], 10, 0));
	call_error:
	  _dl_signal_exception (errval, &exception, NULL);
	}

      while (1)
	{
	  ElfW(Vernaux) *aux;
	  struct link_map *needed = find_needed (strtab + ent->vn_file, map);

	  /* If NEEDED is NULL this means a dependency was not found
	     and no stub entry was created.  This should never happen.  */
	  assert (needed != NULL);

	  /* Make sure this is no stub we created because of a missing
	     dependency.  */
	  if (__builtin_expect (! trace_mode, 1)
	      || ! __builtin_expect (needed->l_faked, 0))
	    {
	      /* NEEDED is the map for the file we need.  Now look for the
		 dependency symbols.  */
	      aux = (ElfW(Vernaux) *) ((char *) ent + ent->vn_aux);
	      while (1)
		{
		  /* Match the symbol.  */
		  result |= match_symbol (DSO_FILENAME (map->l_name),
					  map->l_ns, aux->vna_hash,
					  strtab + aux->vna_name,
					  needed->l_real, verbose,
					  aux->vna_flags & VER_FLG_WEAK);

		  /* Compare the version index.  */
		  if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high)
		    ndx_high = aux->vna_other & 0x7fff;

		  if (aux->vna_next == 0)
		    /* No more symbols.  */
		    break;

		  /* Next symbol.  */
		  aux = (ElfW(Vernaux) *) ((char *) aux + aux->vna_next);
		}
	    }

	  if (ent->vn_next == 0)
	    /* No more dependencies.  */
	    break;

	  /* Next dependency.  */
	  ent = (ElfW(Verneed) *) ((char *) ent + ent->vn_next);
	}
    }

  /* We also must store the names of the defined versions.  Determine
     the maximum index here as well.

     XXX We could avoid the loop by just taking the number of definitions
     as an upper bound of new indices.  */
  if (def != NULL)
    {
      ElfW(Verdef) *ent;
      ent = (ElfW(Verdef) *) (map->l_addr + def->d_un.d_ptr);
      while (1)
	{
	  if ((unsigned int) (ent->vd_ndx & 0x7fff) > ndx_high)
	    ndx_high = ent->vd_ndx & 0x7fff;

	  if (ent->vd_next == 0)
	    /* No more definitions.  */
	    break;

	  ent = (ElfW(Verdef) *) ((char *) ent + ent->vd_next);
	}
    }

  if (ndx_high > 0)
    {
      /* Now we are ready to build the array with the version names
	 which can be indexed by the version index in the VERSYM
	 section.  */
      map->l_versions = (struct r_found_version *)
	calloc (ndx_high + 1, sizeof (*map->l_versions));
      if (__glibc_unlikely (map->l_versions == NULL))
	{
	  _dl_exception_create
	    (&exception, DSO_FILENAME (map->l_name),
	     N_("cannot allocate version reference table"));
	  errval = ENOMEM;
	  goto call_error;
	}

      /* Store the number of available symbols.  */
      map->l_nversions = ndx_high + 1;

      /* Compute the pointer to the version symbols.  */
      map->l_versyms = (void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);

      if (dyn != NULL)
	{
	  ElfW(Verneed) *ent;
	  ent = (ElfW(Verneed) *) (map->l_addr + dyn->d_un.d_ptr);
	  while (1)
	    {
	      ElfW(Vernaux) *aux;
	      aux = (ElfW(Vernaux) *) ((char *) ent + ent->vn_aux);
	      while (1)
		{
		  ElfW(Half) ndx = aux->vna_other & 0x7fff;
		  /* In trace mode, dependencies may be missing.  */
		  if (__glibc_likely (ndx < map->l_nversions))
		    {
		      map->l_versions[ndx].hash = aux->vna_hash;
		      map->l_versions[ndx].hidden = aux->vna_other & 0x8000;
		      map->l_versions[ndx].name = &strtab[aux->vna_name];
		      map->l_versions[ndx].filename = &strtab[ent->vn_file];
		    }

		  if (aux->vna_next == 0)
		    /* No more symbols.  */
		    break;

		  /* Advance to next symbol.  */
		  aux = (ElfW(Vernaux) *) ((char *) aux + aux->vna_next);
		}

	      if (ent->vn_next == 0)
		/* No more dependencies.  */
		break;

	      /* Advance to next dependency.  */
	      ent = (ElfW(Verneed) *) ((char *) ent + ent->vn_next);
	    }
	}

      /* And insert the defined versions.  */
      if (def != NULL)
	{
	  ElfW(Verdef) *ent;
	  ent = (ElfW(Verdef)  *) (map->l_addr + def->d_un.d_ptr);
	  while (1)
	    {
	      ElfW(Verdaux) *aux;
	      aux = (ElfW(Verdaux) *) ((char *) ent + ent->vd_aux);

	      if ((ent->vd_flags & VER_FLG_BASE) == 0)
		{
		  /* The name of the base version should not be
		     available for matching a versioned symbol.  */
		  ElfW(Half) ndx = ent->vd_ndx & 0x7fff;
		  map->l_versions[ndx].hash = ent->vd_hash;
		  map->l_versions[ndx].name = &strtab[aux->vda_name];
		  map->l_versions[ndx].filename = NULL;
		}

	      if (ent->vd_next == 0)
		/* No more definitions.  */
		break;

	      ent = (ElfW(Verdef) *) ((char *) ent + ent->vd_next);
	    }
	}
    }

  return result;
}


int
_dl_check_all_versions (struct link_map *map, int verbose, int trace_mode)
{
  struct link_map *l;
  int result = 0;

  for (l = map; l != NULL; l = l->l_next)
    result |= (! l->l_faked
	       && _dl_check_map_versions (l, verbose, trace_mode));

  return result;
}