loader: support for permanent dlopen()

Asterisk assumes that dlopen() will always run the constructor of a
shared library and every dlclose() will run its destructor. But dlopen()
may be permanent, meaning the constructor will only be run once, as is
the case with musl libc.

With a permanent dlopen() the Asterisk module loader does not work
correctly, because it's expectations regarding when the constructors and
destructors are run are not met. In fact a segmentation fault will occur
when the first module is "re-opened" that has AST_MODFLAG_GLOBAL_SYMBOLS
set (the dlopen() does not call the constructor, resource_being_loaded
is not set to NULL, then strlen is called with NULL instead of a string,
see issue ASTERISK-28319).

This commit adds code to the loader that will manually run the
constructors/destructors of the (non-builtin) modules where needed. To
achieve this a new ao2 container (linked list) is started and filled
with objects that contain the names of the modules and the pointers to
their respective info structs.

This behavior can be activated when configuring Asterisk
(--enable-permanent-dlopen). By default this is disabled, of course.

ASTERISK-28319 #close

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>
Change-Id: I86693a0ecf25d5ba81c73773a03df4abc3426875

configure

@@ -702,6 +702,7 @@ PBX_DYNAMIC_LIST
 POW_LIB
 PBX_WORKING_FORK
 LIBOBJS
+PERMANENT_DLOPEN
 DISABLE_XMLDOC
 CONFIG_LIBXML2
 JANSSON_LIBS
@@ -1345,7 +1346,6 @@ infodir
 docdir
 oldincludedir
 includedir
-runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -1454,6 +1454,7 @@ with_vpb
 with_x11
 with_z
 enable_xmldoc
+enable_permanent_dlopen
 enable_largefile
 enable_internal_poll
 enable_asteriskssl
@@ -1533,7 +1534,6 @@ datadir='${datarootdir}'
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
-runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -1786,15 +1786,6 @@ do
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
-  -runstatedir | --runstatedir | --runstatedi | --runstated \
-  | --runstate | --runstat | --runsta | --runst | --runs \
-  | --run | --ru | --r)
-    ac_prev=runstatedir ;;
-  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
-  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
-  | --run=* | --ru=* | --r=*)
-    runstatedir=$ac_optarg ;;
-
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1932,7 +1923,7 @@ fi
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir runstatedir
+		libdir localedir mandir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -2085,7 +2076,6 @@ Fine tuning of the installation directories:
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
-  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]
@@ -2124,6 +2114,9 @@ Optional Features:
   --enable-dev-mode       Turn on developer mode
   --enable-coverage       Turn on code coverage tracking (for gcov)
   --disable-xmldoc        Explicitly disable XML documentation
+  --enable-permanent-dlopen
+                          Enable when your libc has a permanent dlopen like
+                          musl
   --disable-largefile     omit support for large files
   --enable-internal-poll  Use Asterisk's poll implementation
   --disable-asteriskssl   Disable Asterisk's SSL wrapper library
@@ -14852,6 +14845,25 @@ fi
 
 
 
+fi
+
+# Check whether --enable-permanent-dlopen was given.
+if test "${enable_permanent_dlopen+set}" = set; then :
+  enableval=$enable_permanent_dlopen; case "${enableval}" in
+		y|ye|yes) PERMANENT_DLOPEN=yes ;;
+		n|no)  PERMANENT_DLOPEN=no ;;
+		*) as_fn_error $? "bad value ${enableval} for --enable-permanent-dlopen" "$LINENO" 5  ;;
+	esac
+else
+  PERMANENT_DLOPEN=no
+fi
+
+
+
+if test "${PERMANENT_DLOPEN}" == "yes"; then
+
+$as_echo "#define HAVE_PERMANENT_DLOPEN 1" >>confdefs.h
+
 fi
 
 # some embedded systems omit internationalization (locale) support
@@ -14918,7 +14930,7 @@ else
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
+#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
 		       && LARGE_OFF_T % 2147483647 == 1)
 		      ? 1 : -1];
@@ -14964,7 +14976,7 @@ else
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
+#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
 		       && LARGE_OFF_T % 2147483647 == 1)
 		      ? 1 : -1];
@@ -14988,7 +15000,7 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
+#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
 		       && LARGE_OFF_T % 2147483647 == 1)
 		      ? 1 : -1];
@@ -15033,7 +15045,7 @@ else
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
+#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
 		       && LARGE_OFF_T % 2147483647 == 1)
 		      ? 1 : -1];
@@ -15057,7 +15069,7 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
+#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
 		       && LARGE_OFF_T % 2147483647 == 1)
 		      ? 1 : -1];
@@ -16357,8 +16369,6 @@ main ()
     if (*(data + i) != *(data3 + i))
       return 14;
   close (fd);
-  free (data);
-  free (data3);
   return 0;
 }
 _ACEOF

configure.ac

@@ -729,6 +729,20 @@ if test "${DISABLE_XMLDOC}" != "yes"; then
 
 fi
 
+AC_ARG_ENABLE([permanent-dlopen],
+	[AS_HELP_STRING([--enable-permanent-dlopen],
+		[Enable when your libc has a permanent dlopen like musl])],
+	[case "${enableval}" in
+		y|ye|yes) PERMANENT_DLOPEN=yes ;;
+		n|no)  PERMANENT_DLOPEN=no ;;
+		*) AC_MSG_ERROR(bad value ${enableval} for --enable-permanent-dlopen)  ;;
+	esac], [PERMANENT_DLOPEN=no])
+
+AC_SUBST([PERMANENT_DLOPEN])
+if test "${PERMANENT_DLOPEN}" == "yes"; then
+	AC_DEFINE([HAVE_PERMANENT_DLOPEN], 1, [Define to support libc with permanent dlopen.])
+fi
+
 # some embedded systems omit internationalization (locale) support
 AC_CHECK_HEADERS([xlocale.h])
 

include/asterisk/autoconfig.h.in

@@ -603,6 +603,9 @@
 /* Define to 1 if your system defines the file flag O_SYMLINK in fcntl.h */
 #undef HAVE_O_SYMLINK
 
+/* Define to support libc with permanent dlopen. */
+#undef HAVE_PERMANENT_DLOPEN
+
 /* Define to indicate the PostgreSQL library */
 #undef HAVE_PGSQL
 

main/loader.c

@@ -153,6 +153,117 @@ static unsigned int loader_ready;
 static struct ast_vector_string startup_errors;
 static struct ast_str *startup_error_builder;
 
+#if defined(HAVE_PERMANENT_DLOPEN)
+#define FIRST_DLOPEN 999
+
+struct ao2_container *info_list = NULL;
+
+struct info_list_obj {
+	const struct ast_module_info *info;
+	int dlopened;
+	char name[0];
+};
+
+static struct info_list_obj *info_list_obj_alloc(const char *name,
+	const struct ast_module_info *info)
+{
+	struct info_list_obj *new_entry;
+
+	new_entry = ao2_alloc(sizeof(*new_entry) + strlen(name) + 1, NULL);
+
+	if (!new_entry) {
+		return NULL;
+	}
+
+	strcpy(new_entry->name, name); /* SAFE */
+	new_entry->info = info;
+	new_entry->dlopened = FIRST_DLOPEN;
+
+	return new_entry;
+}
+
+AO2_STRING_FIELD_CMP_FN(info_list_obj, name)
+
+static char *get_name_from_resource(const char *resource)
+{
+	int len;
+	const char *last_three;
+	char *mod_name;
+
+	if (!resource) {
+		return NULL;
+	}
+
+	len = strlen(resource);
+	if (len > 3) {
+		last_three = &resource[len-3];
+		if (!strcasecmp(last_three, ".so")) {
+			mod_name = ast_calloc(1, len - 2);
+			if (mod_name) {
+				ast_copy_string(mod_name, resource, len - 2);
+				return mod_name;
+			} else {
+				/* Unable to allocate memory. */
+				return NULL;
+			}
+		}
+	}
+
+	/* Resource is the name - happens when manually unloading a module. */
+	mod_name = ast_calloc(1, len + 1);
+	if (mod_name) {
+		ast_copy_string(mod_name, resource, len + 1);
+		return mod_name;
+	}
+
+	/* Unable to allocate memory. */
+	return NULL;
+}
+
+static void manual_mod_reg(const void *lib, const char *resource)
+{
+	struct info_list_obj *obj_tmp;
+	char *mod_name;
+
+	if (lib) {
+		mod_name = get_name_from_resource(resource);
+		if (mod_name) {
+			obj_tmp = ao2_find(info_list, mod_name, OBJ_SEARCH_KEY);
+			if (obj_tmp) {
+				if (obj_tmp->dlopened == FIRST_DLOPEN) {
+					obj_tmp->dlopened = 1;
+				} else {
+					ast_module_register(obj_tmp->info);
+				}
+				ao2_ref(obj_tmp, -1);
+			}
+			ast_free(mod_name);
+		}
+	}
+}
+
+static void manual_mod_unreg(const char *resource)
+{
+	struct info_list_obj *obj_tmp;
+	char *mod_name;
+
+	/* When Asterisk shuts down the destructor is called automatically. */
+	if (ast_shutdown_final()) {
+		return;
+	}
+
+	mod_name = get_name_from_resource(resource);
+	if (mod_name) {
+		obj_tmp = ao2_find(info_list, mod_name, OBJ_SEARCH_KEY);
+		if (obj_tmp) {
+			ast_module_unregister(obj_tmp->info);
+			ao2_ref(obj_tmp, -1);
+		}
+		ast_free(mod_name);
+	}
+}
+#endif
+
 static __attribute__((format(printf, 1, 2))) void module_load_error(const char *fmt, ...)
 {
 	char *copy = NULL;
@@ -597,6 +708,23 @@ void ast_module_register(const struct ast_module_info *info)
 
 	/* give the module a copy of its own handle, for later use in registrations and the like */
 	*((struct ast_module **) &(info->self)) = mod;
+
+#if defined(HAVE_PERMANENT_DLOPEN)
+	if (mod->flags.builtin != 1) {
+		struct info_list_obj *obj_tmp = ao2_find(info_list, info->name,
+			OBJ_SEARCH_KEY);
+
+		if (!obj_tmp) {
+			obj_tmp = info_list_obj_alloc(info->name, info);
+			if (obj_tmp) {
+				ao2_link(info_list, obj_tmp);
+				ao2_ref(obj_tmp, -1);
+			}
+		} else {
+			ao2_ref(obj_tmp, -1);
+		}
+	}
+#endif
 }
 
 static int module_post_register(struct ast_module *mod)
@@ -843,6 +971,10 @@ static void logged_dlclose(const char *name, void *lib)
 		error = dlerror();
 		ast_log(AST_LOG_ERROR, "Failure in dlclose for module '%s': %s\n",
 			S_OR(name, "unknown"), S_OR(error, "Unknown error"));
+#if defined(HAVE_PERMANENT_DLOPEN)
+	} else {
+		manual_mod_unreg(name);
+#endif
 	}
 }
 
@@ -949,6 +1081,9 @@ static struct ast_module *load_dlopen(const char *resource_in, const char *so_ex
 
 	resource_being_loaded = mod;
 	mod->lib = dlopen(filename, flags);
+#if defined(HAVE_PERMANENT_DLOPEN)
+	manual_mod_reg(mod->lib, mod->resource);
+#endif
 	if (resource_being_loaded) {
 		struct ast_str *list;
 		int c = 0;
@@ -968,6 +1103,9 @@ static struct ast_module *load_dlopen(const char *resource_in, const char *so_ex
 
 		resource_being_loaded = mod;
 		mod->lib = dlopen(filename, RTLD_LAZY | RTLD_LOCAL);
+#if defined(HAVE_PERMANENT_DLOPEN)
+		manual_mod_reg(mod->lib, mod->resource);
+#endif
 		if (resource_being_loaded) {
 			resource_being_loaded = NULL;
 
@@ -2206,6 +2344,15 @@ int load_modules(void)
 
 	ast_verb(1, "Asterisk Dynamic Loader Starting:\n");
 
+#if defined(HAVE_PERMANENT_DLOPEN)
+	info_list = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_NOLOCK, 0, NULL,
+		info_list_obj_cmp_fn); /* must not be cleaned at shutdown */
+	if (!info_list) {
+		fprintf(stderr, "Module info list allocation failure.\n");
+		return 1;
+	}
+#endif
+
 	AST_LIST_HEAD_INIT_NOLOCK(&load_order);
 	AST_DLLIST_LOCK(&module_list);