glibc/elf/dl-open.c

/* Load a shared object at runtime, relocate it, and run its initializer.
   Copyright (C) 1996, 1997, 1998, 1999 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <assert.h>
#include <dlfcn.h>
#include <errno.h>
#include <libintl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>		/* Check whether MAP_COPY is defined.  */
#include <sys/param.h>
#include <bits/libc-lock.h>
#include <elf/ldsodefs.h>

#include <dl-dst.h>


extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
				    void (*dl_main) (const ElfW(Phdr) *phdr,
						     ElfW(Word) phnum,
						     ElfW(Addr) *user_entry));
weak_extern (_dl_sysdep_start)

/* This function is used to unload the cache file if necessary.  */
extern void _dl_unload_cache (void);

extern int __libc_multiple_libcs;	/* Defined in init-first.c.  */

extern int __libc_argc;
extern char **__libc_argv;

extern char **__environ;

extern int _dl_lazy;			/* Do we do lazy relocations?  */

/* Undefine the following for debugging.  */
/* #define SCOPE_DEBUG 1 */
#ifdef SCOPE_DEBUG
static void show_scope (struct link_map *new);
#endif

/* During the program run we must not modify the global data of
   loaded shared object simultanously in two threads.  Therefore we
   protect `_dl_open' and `_dl_close' in dl-close.c.

   This must be a recursive lock since the initializer function of
   the loaded object might as well require a call to this function.
   At this time it is not anymore a problem to modify the tables.  */
__libc_lock_define_initialized_recursive (, _dl_load_lock)

extern size_t _dl_platformlen;

/* We must be carefull not to leave us in an inconsistent state.  Thus we
   catch any error and re-raise it after cleaning up.  */

struct dl_open_args
{
  const char *file;
  int mode;
  const void *caller;
  struct link_map *map;
};

static void
dl_open_worker (void *a)
{
  struct dl_open_args *args = a;
  const char *file = args->file;
  int mode = args->mode;
  struct link_map *new, *l;
  ElfW(Addr) init;
  struct r_debug *r;
  unsigned int global_add;
  const char *dst;
  int lazy;

  /* Maybe we have to expand a DST.  */
  dst = strchr (file, '$');
  if (dst != NULL)
    {
      const void *caller = args->caller;
      size_t len = strlen (file);
      size_t required;
      struct link_map *call_map;
      char *new_file;

      /* DSTs must not appear in SUID/SGID programs.  */
      if (__libc_enable_secure)
	/* This is an error.  */
	_dl_signal_error (0, "dlopen",
			  "DST not allowed in SUID/SGID programs");

      /* We have to find out from which object the caller is calling.
	 Find the highest-addressed object that ADDRESS is not below.  */
      call_map = NULL;
      for (l = _dl_loaded; l; l = l->l_next)
	if (l->l_addr != 0 /* Make sure we do not currently set this map up
			      in this moment.  */
	    && caller >= (const void *) l->l_addr
	    && (call_map == NULL || call_map->l_addr < l->l_addr))
	  call_map = l;

      if (call_map == NULL)
	/* In this case we assume this is the main application.  */
	call_map = _dl_loaded;

      /* Determine how much space we need.  We have to allocate the
	 memory locally.  */
      required = DL_DST_REQUIRED (call_map, file, len, _dl_dst_count (dst, 0));

      /* Get space for the new file name.  */
      new_file = (char *) alloca (required + 1);

      /* Generate the new file name.  */
      DL_DST_SUBSTITUTE (call_map, file, new_file, 0);

      /* If the substitution failed don't try to load.  */
      if (*new_file == '\0')
	_dl_signal_error (0, "dlopen",
			  "empty dynamic string token substitution");

      /* Now we have a new file name.  */
      file = new_file;
    }

  /* Load the named object.  */
  args->map = new = _dl_map_object (NULL, file, 0, lt_loaded, 0);
  if (new->l_searchlist.r_list)
    /* It was already open.  */
    return;

  /* Load that object's dependencies.  */
  global_add = _dl_map_object_deps (new, NULL, 0, 0, mode & RTLD_GLOBAL);

  /* So far, so good.  Now check the versions.  */
  (void) _dl_check_all_versions (new, 0);

#ifdef SCOPE_DEBUG
  show_scope (new);
#endif

  /* Only do lazy relocation if `LD_BIND_NOW' is not set.  */
  lazy = (mode & RTLD_BINDING_MASK) == RTLD_LAZY && _dl_lazy;

  /* Relocate the objects loaded.  We do this in reverse order so that copy
     relocs of earlier objects overwrite the data written by later objects.  */

  l = new;
  while (l->l_next)
    l = l->l_next;
  while (1)
    {
      if (! l->l_relocated)
	{
#ifdef PIC
	  if (_dl_profile != NULL)
	    {
	      /* If this here is the shared object which we want to profile
		 make sure the profile is started.  We can find out whether
	         this is necessary or not by observing the `_dl_profile_map'
	         variable.  If was NULL but is not NULL afterwars we must
		 start the profiling.  */
	      struct link_map *old_profile_map = _dl_profile_map;

	      _dl_relocate_object (l, l->l_scope, 1, 1);

	      if (old_profile_map == NULL && _dl_profile_map != NULL)
		/* We must prepare the profiling.  */
		_dl_start_profile (_dl_profile_map, _dl_profile_output);
	    }
	  else
#endif
	    _dl_relocate_object (l, l->l_scope, lazy, 0);
	}

      if (l == new)
	break;
      l = l->l_prev;
    }

  /* Notify the debugger we have added some objects.  We need to call
     _dl_debug_initialize in a static program in case dynamic linking has
     not been used before.  */
  r = _dl_debug_initialize (0);
  r->r_state = RT_ADD;
  _dl_debug_state ();

  /* Run the initializer functions of new objects.  */
  while ((init = _dl_init_next (&new->l_searchlist)))
    (*(void (*) (int, char **, char **)) init) (__libc_argc, __libc_argv,
						__environ);

  /* Now we can make the new map available in the global scope.  */
  while (global_add-- > 0)
    _dl_main_searchlist->r_list[_dl_main_searchlist->r_nlist++]->l_global = 1;

  if (_dl_sysdep_start == NULL)
    /* We must be the static _dl_open in libc.a.  A static program that
       has loaded a dynamic object now has competition.  */
    __libc_multiple_libcs = 1;
}


void *
internal_function
_dl_open (const char *file, int mode, const void *caller)
{
  struct dl_open_args args;
  char *errstring;
  int errcode;

  if ((mode & RTLD_BINDING_MASK) == 0)
    /* One of the flags must be set.  */
    _dl_signal_error (EINVAL, file, _("invalid mode for dlopen()"));

  /* Make sure we are alone.  */
  __libc_lock_lock (_dl_load_lock);

  args.file = file;
  args.mode = mode;
  args.caller = caller;
  args.map = NULL;
  errcode = _dl_catch_error (&errstring, dl_open_worker, &args);

#ifndef MAP_COPY
  /* We must munmap() the cache file.  */
  _dl_unload_cache ();
#endif

  /* Release the lock.  */
  __libc_lock_unlock (_dl_load_lock);

  if (errstring)
    {
      /* Some error occured during loading.  */
      char *local_errstring;

      /* Remove the object from memory.  It may be in an inconsistent
	 state if relocation failed, for example.  */
      if (args.map)
	_dl_close (args.map);

      /* Make a local copy of the error string so that we can release the
	 memory allocated for it.  */
      local_errstring = strdupa (errstring);
      free (errstring);

      /* Reraise the error.  */
      _dl_signal_error (errcode, NULL, local_errstring);
    }

  return args.map;
}


#ifdef SCOPE_DEBUG
#include <unistd.h>

static void
show_scope (struct link_map *new)
{
  int scope_cnt;

  for (scope_cnt = 0; new->l_scope[scope_cnt] != NULL; ++scope_cnt)
    {
      char numbuf[2];
      unsigned int cnt;

      numbuf[0] = '0' + scope_cnt;
      numbuf[1] = '\0';
      _dl_sysdep_message ("scope ", numbuf, ":", NULL);

      for (cnt = 0; cnt < new->l_scope[scope_cnt]->r_nlist; ++cnt)
	if (*new->l_scope[scope_cnt]->r_list[cnt]->l_name)
	  _dl_sysdep_message (" ",
			      new->l_scope[scope_cnt]->r_list[cnt]->l_name,
			      NULL);
	else
	  _dl_sysdep_message (" <main>", NULL);

      _dl_sysdep_message ("\n", NULL);
    }
}
#endif