/* Handle loading and unloading shared objects for internal libc purposes.

   Copyright (C) 1999-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Zack Weinberg <zack@rabi.columbia.edu>, 1999.

   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 <dlfcn.h>

#include <stdlib.h>

#include <ldsodefs.h>

#include <dl-hash.h>

extern int __libc_argc attribute_hidden;

extern char **__libc_argv attribute_hidden;

extern char **__environ;

/* The purpose of this file is to provide wrappers around the dynamic

   linker error mechanism (similar to dlopen() et al in libdl) which

   are usable from within libc.  Generally we want to throw away the

   string that dlerror() would return and just pass back a null pointer

   for errors.  This also lets the rest of libc not know about the error

   handling mechanism.

   Much of this code came from gconv_dl.c with slight modifications. */

static int

dlerror_run (void (*operate) (void *), void *args)

{

  const char *objname;

  const char *last_errstring = NULL;

  bool malloced;

  int result = (_dl_catch_error (&objname, &last_errstring, &malloced,

				operate, args)

		?: last_errstring != NULL);

  if (result && malloced)

    free ((char *) last_errstring);

  return result;

}

/* These functions are called by dlerror_run... */

struct do_dlopen_args

{

  /* Argument to do_dlopen.  */

  const char *name;

  /* Opening mode.  */

  int mode;

  /* This is the caller of the dlopen() function.  */

  const void *caller_dlopen;

  /* Return from do_dlopen.  */

  struct link_map *map;

};

struct do_dlsym_args

{

  /* Arguments to do_dlsym.  */

  struct link_map *map;

  const char *name;

  /* Return values of do_dlsym.  */

  lookup_t loadbase;

  const ElfW(Sym) *ref;

};

struct do_dlvsym_args

{

  /* dlvsym is like dlsym.  */

  struct do_dlsym_args dlsym;

  /* But dlvsym needs a version  as well.  */

  struct r_found_version version;

};

static void

do_dlopen (void *ptr)

{

  struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;

  /* Open and relocate the shared object.  */

  args->map = GLRO(dl_open) (args->name, args->mode, args->caller_dlopen,

			     __LM_ID_CALLER, __libc_argc, __libc_argv,

			     __environ);

}

static void

do_dlsym (void *ptr)

{

  struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;

  args->ref = NULL;

  args->loadbase = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,

					     args->map->l_local_scope, NULL, 0,

					     DL_LOOKUP_RETURN_NEWEST, NULL);

}

static void

do_dlvsym (void *ptr)

{

  struct do_dlvsym_args *args = ptr;

  args->dlsym.ref = NULL;

  args->dlsym.loadbase

    = GLRO(dl_lookup_symbol_x) (args->dlsym.name, args->dlsym.map,

				&args->dlsym.ref,

				args->dlsym.map->l_local_scope,

				&args->version, 0, 0, NULL);

}

static void

do_dlclose (void *ptr)

{

  GLRO(dl_close) ((struct link_map *) ptr);

}

/* This code is to support __libc_dlopen from __libc_dlopen'ed shared

   libraries.  We need to ensure the statically linked __libc_dlopen

   etc. functions are used instead of the dynamically loaded.  */

struct dl_open_hook

{

  void *(*dlopen_mode) (const char *name, int mode);

  void *(*dlsym) (void *map, const char *name);

  int (*dlclose) (void *map);

  void *(*dlvsym) (void *map, const char *name, const char *version);

};

#ifdef SHARED

extern struct dl_open_hook *_dl_open_hook;

libc_hidden_proto (_dl_open_hook);

struct dl_open_hook *_dl_open_hook __attribute__ ((nocommon));

libc_hidden_data_def (_dl_open_hook);

/* The dlvsym member was added retroactively to struct dl_open_hook.

   Static applications which have it will set _dl_open_hook2 in

   addition to _dl_open_hook.  */

extern struct dl_open_hook *_dl_open_hook2;

libc_hidden_proto (_dl_open_hook2);

struct dl_open_hook *_dl_open_hook2 __attribute__ ((nocommon));

libc_hidden_data_def (_dl_open_hook2);

#else

static void

do_dlsym_private (void *ptr)

{

  lookup_t l;

  struct r_found_version vers;

  vers.name = "GLIBC_PRIVATE";

  vers.hidden = 1;

  /* vers.hash = _dl_elf_hash (vers.name);  */

  vers.hash = 0x0963cf85;

  vers.filename = NULL;

  struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;

  args->ref = NULL;

  l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,

				args->map->l_scope, &vers, 0, 0, NULL);

  args->loadbase = l;

}

static struct dl_open_hook _dl_open_hook =

  {

    .dlopen_mode = __libc_dlopen_mode,

    .dlsym = __libc_dlsym,

    .dlclose = __libc_dlclose,

    .dlvsym = __libc_dlvsym,

  };

#endif

/* ... and these functions call dlerror_run. */

void *

__libc_dlopen_mode (const char *name, int mode)

{

  struct do_dlopen_args args;

  args.name = name;

  args.mode = mode;

  args.caller_dlopen = RETURN_ADDRESS (0);

#ifdef SHARED

  if (!rtld_active ())

    return _dl_open_hook->dlopen_mode (name, mode);

  return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);

#else

  if (dlerror_run (do_dlopen, &args))

    return NULL;

  __libc_register_dl_open_hook (args.map);

  __libc_register_dlfcn_hook (args.map);

  return (void *) args.map;

#endif

}

libc_hidden_def (__libc_dlopen_mode)

#ifndef SHARED

void *

__libc_dlsym_private (struct link_map *map, const char *name)

{

  struct do_dlsym_args sargs;

  sargs.map = map;

  sargs.name = name;

  if (! dlerror_run (do_dlsym_private, &sargs))

    return DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref);

  return NULL;

}

void

__libc_register_dl_open_hook (struct link_map *map)

{

  struct dl_open_hook **hook;

  hook = (struct dl_open_hook **) __libc_dlsym_private (map, "_dl_open_hook");

  if (hook != NULL)

    *hook = &_dl_open_hook;

  /* For dlvsym support.  */

  hook = (struct dl_open_hook **) __libc_dlsym_private (map, "_dl_open_hook2");

  if (hook != NULL)

    *hook = &_dl_open_hook;

}

#endif

void *

__libc_dlsym (void *map, const char *name)

{

  struct do_dlsym_args args;

  args.map = map;

  args.name = name;

#ifdef SHARED

  if (!rtld_active ())

    return _dl_open_hook->dlsym (map, name);

#endif

  return (dlerror_run (do_dlsym, &args) ? NULL

	  : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));

}

libc_hidden_def (__libc_dlsym)

/* Replacement for dlvsym.  MAP must be a real map.  This function

   returns NULL without setting the dlerror value in case of static

   dlopen from an old binary.  */

void *

__libc_dlvsym (void *map, const char *name, const char *version)

{

#ifdef SHARED

  if (!rtld_active ())

    {

      /* The static application is too old and does not provide the

	 dlvsym hook.  */

      if (_dl_open_hook2 == NULL)

	return NULL;

      return _dl_open_hook2->dlvsym (map, name, version);

    }

#endif

  struct do_dlvsym_args args;

  args.dlsym.map = map;

  args.dlsym.name = name;

  /* See _dl_vsym in dl-sym.c.  */

  args.version.name = version;

  args.version.hidden = 1;

  args.version.hash = _dl_elf_hash (version);

  args.version.filename = NULL;

  return (dlerror_run (do_dlvsym, &args) ? NULL

	  : (void *) (DL_SYMBOL_ADDRESS (args.dlsym.loadbase,

					 args.dlsym.ref)));

}

libc_hidden_def (__libc_dlvsym)

int

__libc_dlclose (void *map)

{

#ifdef SHARED

  if (!rtld_active ())

    return _dl_open_hook->dlclose (map);

#endif

  return dlerror_run (do_dlclose, map);

}

libc_hidden_def (__libc_dlclose)

static bool __libc_freeres_fn_section

free_slotinfo (struct dtv_slotinfo_list **elemp)

{

  size_t cnt;

  if (*elemp == NULL)

    /* Nothing here, all is removed (or there never was anything).  */

    return true;

  if (!free_slotinfo (&(*elemp)->next))

    /* We cannot free the entry.  */

    return false;

  /* That cleared our next pointer for us.  */

  for (cnt = 0; cnt < (*elemp)->len; ++cnt)

    if ((*elemp)->slotinfo[cnt].map != NULL)

      /* Still used.  */

      return false;

  /* We can remove the list element.  */

  free (*elemp);

  *elemp = NULL;

  return true;

}

libc_freeres_fn (free_mem)

{

  struct link_map *l;

  struct r_search_path_elem *d;

  /* Remove all search directories.  */

  d = GL(dl_all_dirs);

  while (d != GLRO(dl_init_all_dirs))

    {

      struct r_search_path_elem *old = d;

      d = d->next;

      free (old);

    }

  for (Lmid_t ns = 0; ns < GL(dl_nns); ++ns)

    {

      for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)

	{

	  struct libname_list *lnp = l->l_libname->next;

	  l->l_libname->next = NULL;

	  /* Remove all additional names added to the objects.  */

	  while (lnp != NULL)

	    {

	      struct libname_list *old = lnp;

	      lnp = lnp->next;

	      if (! old->dont_free)

		free (old);

	    }

	  /* Free the initfini dependency list.  */

	  if (l->l_free_initfini)

	    free (l->l_initfini);

	  l->l_initfini = NULL;

	}

      if (__builtin_expect (GL(dl_ns)[ns]._ns_global_scope_alloc, 0) != 0

	  && (GL(dl_ns)[ns]._ns_main_searchlist->r_nlist

	      // XXX Check whether we need NS-specific initial_searchlist

	      == GLRO(dl_initial_searchlist).r_nlist))

	{

	  /* All object dynamically loaded by the program are unloaded.  Free

	     the memory allocated for the global scope variable.  */

	  struct link_map **old = GL(dl_ns)[ns]._ns_main_searchlist->r_list;

	  /* Put the old map in.  */

	  GL(dl_ns)[ns]._ns_main_searchlist->r_list

	    // XXX Check whether we need NS-specific initial_searchlist

	    = GLRO(dl_initial_searchlist).r_list;

	  /* Signal that the original map is used.  */

	  GL(dl_ns)[ns]._ns_global_scope_alloc = 0;

	  /* Now free the old map.  */

	  free (old);

	}

    }

  /* Free the memory allocated for the dtv slotinfo array.  We can do

     this only if all modules which used this memory are unloaded.  */

#ifdef SHARED

  if (GL(dl_initial_dtv) == NULL)

    /* There was no initial TLS setup, it was set up later when

       it used the normal malloc.  */

    free_slotinfo (&GL(dl_tls_dtv_slotinfo_list));

  else

#endif

    /* The first element of the list does not have to be deallocated.

       It was allocated in the dynamic linker (i.e., with a different

       malloc), and in the static library it's in .bss space.  */

    free_slotinfo (&GL(dl_tls_dtv_slotinfo_list)->next);

  void *scope_free_list = GL(dl_scope_free_list);

  GL(dl_scope_free_list) = NULL;

  free (scope_free_list);

}