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✏️ Editing: dlopen.c

/* loader-dlopen.c --  dynamic linking with dlopen/dlsym

NOTE: The canonical source of this file is maintained with the
   GNU Libtool package.  Report bugs to bug-libtool@gnu.org.

GNU Libltdl 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 of the License, or (at your option) any later version.

As a special exception to the GNU Lesser General Public License,
if you distribute this file as part of a program or library that
is built using GNU Libtool, you may include this file under the
same distribution terms that you use for the rest of that program.

GNU Libltdl 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 GNU Libltdl; see the file COPYING.LIB.  If not, a
copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
or obtained by writing to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

#include "lt__private.h"
#include "lt_dlloader.h"

/* Use the preprocessor to rename non-static symbols to avoid namespace
   collisions when the loader code is statically linked into libltdl.
   Use the "<module_name>_LTX_" prefix so that the symbol addresses can
   be fetched from the preloaded symbol list by lt_dlsym():  */
#define get_vtable	dlopen_LTX_get_vtable

LT_BEGIN_C_DECLS
LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
LT_END_C_DECLS

/* Boilerplate code to set up the vtable for hooking this loader into
   libltdl's loader list:  */
static int	 vl_exit  (lt_user_data loader_data);
static lt_module vm_open  (lt_user_data loader_data, const char *filename,
                           lt_dladvise advise);
static int	 vm_close (lt_user_data loader_data, lt_module module);
static void *	 vm_sym   (lt_user_data loader_data, lt_module module,
			  const char *symbolname);

static lt_dlvtable *vtable = 0;

/* Return the vtable for this loader, only the name and sym_prefix
   attributes (plus the virtual function implementations, obviously)
   change between loaders.  */
lt_dlvtable *
get_vtable (lt_user_data loader_data)
{
  if (!vtable)
    {
      vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
    }

if (vtable && !vtable->name)
    {
      vtable->name		= "lt_dlopen";
#if defined DLSYM_USCORE
      vtable->sym_prefix	= "_";
#endif
      vtable->module_open	= vm_open;
      vtable->module_close	= vm_close;
      vtable->find_sym		= vm_sym;
      vtable->dlloader_exit	= vl_exit;
      vtable->dlloader_data	= loader_data;
      vtable->priority		= LT_DLLOADER_PREPEND;
    }

if (vtable && (vtable->dlloader_data != loader_data))
    {
      LT__SETERROR (INIT_LOADER);
      return 0;
    }

return vtable;
}

/* --- IMPLEMENTATION --- */

#if defined HAVE_DLFCN_H
#  include <dlfcn.h>
#endif

#if defined HAVE_SYS_DL_H
#  include <sys/dl.h>
#endif

/* We may have to define LT_LAZY_OR_NOW in the command line if we
   find out it does not work in some platform. */
#if !defined LT_LAZY_OR_NOW
#  if defined RTLD_LAZY
#    define LT_LAZY_OR_NOW	RTLD_LAZY
#  else
#    if defined DL_LAZY
#      define LT_LAZY_OR_NOW	DL_LAZY
#    endif
#  endif /* !RTLD_LAZY */
#endif
#if !defined LT_LAZY_OR_NOW
#  if defined RTLD_NOW
#    define LT_LAZY_OR_NOW	RTLD_NOW
#  else
#    if defined DL_NOW
#      define LT_LAZY_OR_NOW	DL_NOW
#    endif
#  endif /* !RTLD_NOW */
#endif
#if !defined LT_LAZY_OR_NOW
#  define LT_LAZY_OR_NOW	0
#endif /* !LT_LAZY_OR_NOW */

/* We only support local and global symbols from modules for loaders
   that provide such a thing, otherwise the system default is used.  */
#if !defined RTLD_GLOBAL
#  if defined DL_GLOBAL
#    define RTLD_GLOBAL		DL_GLOBAL
#  endif
#endif /* !RTLD_GLOBAL */
#if !defined RTLD_LOCAL
#  if defined DL_LOCAL
#    define RTLD_LOCAL		DL_LOCAL
#  endif
#endif /* !RTLD_LOCAL */

#if defined HAVE_DLERROR
#  define DLERROR(arg)	dlerror ()
#else
#  define DLERROR(arg)	LT__STRERROR (arg)
#endif

#define DL__SETERROR(errorcode) \
	LT__SETERRORSTR (DLERROR (errorcode))

/* A function called through the vtable when this loader is no
   longer needed by the application.  */
static int
vl_exit (lt_user_data loader_data LT__UNUSED)
{
  vtable = NULL;
  return 0;
}

/* A function called through the vtable to open a module with this
   loader.  Returns an opaque representation of the newly opened
   module for processing with this loader's other vtable functions.  */
static lt_module
vm_open (lt_user_data loader_data LT__UNUSED, const char *filename,
         lt_dladvise advise)
{
  int		module_flags = LT_LAZY_OR_NOW;
  lt_module	module;
#ifdef RTLD_MEMBER
  int		len = LT_STRLEN (filename);
#endif

if (advise)
    {
#ifdef RTLD_GLOBAL
      /* If there is some means of asking for global symbol resolution,
         do so.  */
      if (advise->is_symglobal)
        module_flags |= RTLD_GLOBAL;
#else
      /* Otherwise, reset that bit so the caller can tell it wasn't
         acted on.  */
      advise->is_symglobal = 0;
#endif

/* And similarly for local only symbol resolution.  */
#ifdef RTLD_LOCAL
      if (advise->is_symlocal)
        module_flags |= RTLD_LOCAL;
#else
      advise->is_symlocal = 0;
#endif
    }

#ifdef RTLD_MEMBER /* AIX */
  if (len >= 4) /* at least "l(m)" */
    {
      /* Advise loading an archive member only if the filename really
	 contains both the opening and closing parent, and a member. */
      if (filename[len-1] == ')')
	{
	  const char *opening = strrchr(filename, '(');
	  if (opening && opening < (filename+len-2) && strchr(opening+1, '/') == NULL)
	    module_flags |= RTLD_MEMBER;
	}
    }
#endif

module = dlopen (filename, module_flags);

#if defined RTLD_MEMBER && defined LT_SHARED_LIB_MEMBER
  if (!module && len && !(module_flags & RTLD_MEMBER) && errno == ENOEXEC)
    {
      /* Loading without a member specified failed with "Exec format error".
	 So the file is there, but either has wrong bitwidth, or is an
	 archive eventually containing the default shared archive member.
	 Retry with default member, getting same error in worst case. */
      const char *member = LT_SHARED_LIB_MEMBER;

char *attempt = MALLOC (char, len + strlen (member) + 1);
      if (!attempt)
	{
	  LT__SETERROR (NO_MEMORY);
	  return module;
	}

sprintf (attempt, "%s%s", filename, member);
      module = vm_open (loader_data, attempt, advise);
      FREE (attempt);
      return module;
    }
#endif

if (!module)
    {
      DL__SETERROR (CANNOT_OPEN);
    }

return module;
}

/* A function called through the vtable when a particular module
   should be unloaded.  */
static int
vm_close (lt_user_data loader_data LT__UNUSED, lt_module module)
{
  int errors = 0;

if (dlclose (module) != 0)
    {
      DL__SETERROR (CANNOT_CLOSE);
      ++errors;
    }

return errors;
}

/* A function called through the vtable to get the address of
   a symbol loaded from a particular module.  */
static void *
vm_sym (lt_user_data loader_data LT__UNUSED, lt_module module, const char *name)
{
  void *address = dlsym (module, name);

if (!address)
    {
      DL__SETERROR (SYMBOL_NOT_FOUND);
    }

return address;
}

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