/* GMODULE - GLIB wrapper code for dynamic module loading

 * Copyright (C) 1998, 2000 Tim Janik

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This 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.

 *

 * This 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 this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/. 

 */

/* 

 * MT safe

 */

#include "config.h"

#include <dlfcn.h>

#include <glib.h>

#ifdef __CYGWIN__

#define CYGWIN_WORKAROUND

#endif

#ifdef CYGWIN_WORKAROUND

#include <sys/cygwin.h>

#include <windows.h>

#include <tlhelp32.h>

#include <errno.h>

#endif

/* Perl includes <nlist.h> and <link.h> instead of <dlfcn.h> on some systems? */

/* dlerror() is not implemented on all systems

 */

#ifndef G_MODULE_HAVE_DLERROR

#  ifdef __NetBSD__

#    define dlerror() g_strerror (errno)

#  else /* !__NetBSD__ */

/* could we rely on errno's state here? */

#    define dlerror() "unknown dl-error"

#  endif /* !__NetBSD__ */

#endif  /* G_MODULE_HAVE_DLERROR */

/* some flags are missing on some systems, so we provide

 * harmless defaults.

 * The Perl sources say, RTLD_LAZY needs to be defined as (1),

 * at least for Solaris 1.

 *

 * Mandatory:

 * RTLD_LAZY   - resolve undefined symbols as code from the dynamic library

 *     is executed.

 * RTLD_NOW    - resolve all undefined symbols before dlopen returns, and fail

 *     if this cannot be done.

 * Optionally:

 * RTLD_GLOBAL - the external symbols defined in the library will be made

 *     available to subsequently loaded libraries.

 */

#ifndef HAVE_RTLD_LAZY

#define RTLD_LAZY 1

#endif  /* RTLD_LAZY */

#ifndef HAVE_RTLD_NOW

#define RTLD_NOW  0

#endif  /* RTLD_NOW */

/* some systems (OSF1 V5.0) have broken RTLD_GLOBAL linkage */

#ifdef G_MODULE_BROKEN_RTLD_GLOBAL

#undef  RTLD_GLOBAL

#undef  HAVE_RTLD_GLOBAL

#endif /* G_MODULE_BROKEN_RTLD_GLOBAL */

#ifndef HAVE_RTLD_GLOBAL

#define RTLD_GLOBAL 0

#endif  /* RTLD_GLOBAL */

/* According to POSIX.1-2001, dlerror() is not necessarily thread-safe

 * (see https://pubs.opengroup.org/onlinepubs/009695399/), and so must be

 * called within the same locked section as the dlopen()/dlsym() call which

 * may have caused an error.

 *

 * However, some libc implementations, such as glibc, implement dlerror() using

 * thread-local storage, so are thread-safe. As of early 2021:

 *  - glibc is thread-safe: https://github.com/bminor/glibc/blob/HEAD/dlfcn/libc_dlerror_result.c

 *  - musl-libc is thread-safe since version 1.1.9 -- released in 2015: https://wiki.musl-libc.org/functional-differences-from-glibc.html#Thread-safety-of-%3Ccode%3Edlerror%3C/code%3E

 *  - uclibc-ng is not thread-safe: https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/ldso/libdl/libdl.c?id=132decd2a043d0ccf799f42bf89f3ae0c11e95d5#n1075

 *  - Other libc implementations have not been checked, and no problems have

 *    been reported with them in 10 years, so default to assuming that they

 *    don’t need additional thread-safety from GLib

 */

#if defined(__UCLIBC__)

G_LOCK_DEFINE_STATIC (errors);

#else

#define DLERROR_IS_THREADSAFE 1

#endif

static void

lock_dlerror (void)

{

#ifndef DLERROR_IS_THREADSAFE

  G_LOCK (errors);

#endif

}

static void

unlock_dlerror (void)

{

#ifndef DLERROR_IS_THREADSAFE

  G_UNLOCK (errors);

#endif

}

/* This should be called with lock_dlerror() held */

static const gchar *

fetch_dlerror (gboolean replace_null)

{

  const gchar *msg = dlerror ();

  /* make sure we always return an error message != NULL, if

   * expected to do so. */

  if (!msg && replace_null)

    return "unknown dl-error";

  return msg;

}

static gpointer

_g_module_open (const gchar *file_name,

    gboolean     bind_lazy,

    gboolean     bind_local,

                GError     **error)

{

  gpointer handle;

  lock_dlerror ();

  handle = dlopen (file_name,

                   (bind_local ? RTLD_LOCAL : RTLD_GLOBAL) | (bind_lazy ? RTLD_LAZY : RTLD_NOW));

  if (!handle)

    {

      const gchar *message = fetch_dlerror (TRUE);

      g_module_set_error (message);

      g_set_error_literal (error, G_MODULE_ERROR, G_MODULE_ERROR_FAILED, message);

    }

  unlock_dlerror ();

  return handle;

}

static gpointer

_g_module_self (void)

{

  gpointer handle;

  /* to query symbols from the program itself, special link options

   * are required on some systems.

   */

  /* On Android 32 bit (i.e. not __LP64__), dlopen(NULL)

   * does not work reliable and generally no symbols are found

   * at all. RTLD_DEFAULT works though.

   * On Android 64 bit, dlopen(NULL) seems to work but dlsym(handle)

   * always returns 'undefined symbol'. Only if RTLD_DEFAULT or 

   * NULL is given, dlsym returns an appropriate pointer.

   */

  lock_dlerror ();

#if defined(__ANDROID__) || defined(__NetBSD__)

  handle = RTLD_DEFAULT;

#else

  handle = dlopen (NULL, RTLD_GLOBAL | RTLD_LAZY);

#endif

  if (!handle)

    g_module_set_error (fetch_dlerror (TRUE));

  unlock_dlerror ();

  return handle;

}

static void

_g_module_close (gpointer handle)

{

#if defined(__ANDROID__) || defined(__NetBSD__)

  if (handle != RTLD_DEFAULT)

#endif

    {

      lock_dlerror ();

      if (dlclose (handle) != 0)

        g_module_set_error (fetch_dlerror (TRUE));

      unlock_dlerror ();

    }

}

#ifdef CYGWIN_WORKAROUND

static gpointer

find_in_any_module_cygwin (const char *symbol_name)

{

  HANDLE snapshot;

  MODULEENTRY32 entry = {

    .dwSize = sizeof (entry),

  };

  gpointer p = NULL;

retry:

  snapshot = CreateToolhelp32Snapshot (TH32CS_SNAPMODULE, 0);

  if (snapshot == INVALID_HANDLE_VALUE)

    {

      DWORD code = GetLastError ();

      if (code == ERROR_BAD_LENGTH)

        {

          /* Probably only happens when inspecting other processes */

          g_thread_yield ();

          goto retry;

        }

      else

        {

          g_warning ("%s failed with error code %u",

                     "CreateToolhelp32Snapshot",

                     (unsigned int) code);

          return NULL;

        }

    }

  if (Module32First (snapshot, &entry))

    {

      do

        {

          if ((p = GetProcAddress (entry.hModule, symbol_name)) != NULL)

            {

              ssize_t size = 0;

              char *posix_path;

              G_STATIC_ASSERT (G_N_ELEMENTS (entry.szExePath) <= MAX_PATH);

              do

                {

                  posix_path = (size > 0) ? g_alloca ((long unsigned int) size) : NULL;

                  size = cygwin_conv_path (CCP_WIN_W_TO_POSIX, entry.szExePath, posix_path, (size_t) size);

                }

              while (size > 0);

              if (size < 0)

                {

                  g_warning ("%s failed with errno %d", "cygwin_conv_path", errno);

                  break;

                }

              if (g_str_has_prefix (posix_path, "/usr/lib") ||

                  g_str_has_prefix (posix_path, "/usr/local/lib"))

                {

                  p = NULL;

                }

              else

                break;

            }

        }

      while (Module32Next (snapshot, &entry));

    }

  CloseHandle (snapshot);

  return p;

}

#endif

static gpointer

_g_module_symbol (gpointer     handle,

      const gchar *symbol_name)

{

  gpointer p;

  const gchar *msg;

  lock_dlerror ();

  fetch_dlerror (FALSE);

  p = dlsym (handle, symbol_name);

  msg = fetch_dlerror (FALSE);

#ifndef CYGWIN_WORKAROUND

  if (msg)

    g_module_set_error (msg);

  unlock_dlerror ();

#else

  if (msg)

    {

      char *msg_copy = g_strdup (msg);

      unlock_dlerror ();

      p = find_in_any_module_cygwin (symbol_name);

      if (!p)

        g_module_set_error_unduped (msg_copy);

      else

        g_free (msg_copy);

    }

#endif

  return p;

}