/* * Copyright 2013-2017 by PaX Team <pageexec@freemail.hu> * Licensed under the GPL v2 * * Note: the choice of the license means that the compilation process is *       NOT 'eligible' as defined by gcc's library exception to the GPL v3, *       but for the kernel it doesn't matter since it doesn't link against *       any of the gcc libraries * * gcc plugin to forcibly initialize certain local variables that could * otherwise leak kernel stack to userland if they aren't properly initialized * by later code * * Homepage: http://pax.grsecurity.net/ * * Options: * -fplugin-arg-structleak_plugin-disable * -fplugin-arg-structleak_plugin-verbose * * Usage: * $ # for 4.5/4.6/C based 4.7 * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o structleak_plugin.so structleak_plugin.c * $ # for C++ based 4.7/4.8+ * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o structleak_plugin.so structleak_plugin.c * $ gcc -fplugin=./structleak_plugin.so test.c -O2 * * TODO: eliminate redundant initializers *       increase type coverage */ #include "gcc-common.h" /* unused C type flag in all versions 4.5-6 */#define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE) __visible int plugin_is_GPL_compatible; static struct plugin_info structleak_plugin_info = {	.version	= "201607271510vanilla",	.help		= "disable\tdo not activate plugin\n"			   "verbose\tprint all initialized variables\n",}; static bool verbose; static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs){	*no_add_attrs = true; 	/* check for types? for now accept everything linux has to offer */	if (TREE_CODE(*node) != FIELD_DECL)		return NULL_TREE; 	*no_add_attrs = false;	return NULL_TREE;} static struct attribute_spec user_attr = {	.name			= "user",	.min_length		= 0,	.max_length		= 0,	.decl_required		= false,	.type_required		= false,	.function_type_required	= false,	.handler		= handle_user_attribute,#if BUILDING_GCC_VERSION >= 4007	.affects_type_identity	= true#endif}; static void register_attributes(void *event_data, void *data){	register_attribute(&user_attr);} static tree get_field_type(tree field){	return strip_array_types(TREE_TYPE(field));} static bool is_userspace_type(tree type){	tree field; 	for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) {		tree fieldtype = get_field_type(field);		enum tree_code code = TREE_CODE(fieldtype); 		if (code == RECORD_TYPE || code == UNION_TYPE)			if (is_userspace_type(fieldtype))				return true; 		if (lookup_attribute("user", DECL_ATTRIBUTES(field)))			return true;	}	return false;} static void finish_type(void *event_data, void *data){	tree type = (tree)event_data; 	if (type == NULL_TREE || type == error_mark_node)		return; #if BUILDING_GCC_VERSION >= 5000	if (TREE_CODE(type) == ENUMERAL_TYPE)		return;#endif 	if (TYPE_USERSPACE(type))		return; 	if (is_userspace_type(type))		TYPE_USERSPACE(type) = 1;} static void initialize(tree var){	basic_block bb;	gimple_stmt_iterator gsi;	tree initializer;	gimple init_stmt; 	/* this is the original entry bb before the forced split */	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); 	/* first check if variable is already initialized, warn otherwise */	for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {		gimple stmt = gsi_stmt(gsi);		tree rhs1; 		/* we're looking for an assignment of a single rhs... */		if (!gimple_assign_single_p(stmt))			continue;		rhs1 = gimple_assign_rhs1(stmt);#if BUILDING_GCC_VERSION >= 4007		/* ... of a non-clobbering expression... */		if (TREE_CLOBBER_P(rhs1))			continue;#endif		/* ... to our variable... */		if (gimple_get_lhs(stmt) != var)			continue;		/* if it's an initializer then we're good */		if (TREE_CODE(rhs1) == CONSTRUCTOR)			return;	} 	/* these aren't the 0days you're looking for */	if (verbose)		inform(DECL_SOURCE_LOCATION(var),			"userspace variable will be forcibly initialized"); 	/* build the initializer expression */	initializer = build_constructor(TREE_TYPE(var), NULL); 	/* build the initializer stmt */	init_stmt = gimple_build_assign(var, initializer);	gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));	gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);	update_stmt(init_stmt);} static unsigned int structleak_execute(void){	basic_block bb;	unsigned int ret = 0;	tree var;	unsigned int i; 	/* split the first bb where we can put the forced initializers */	gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));	if (!single_pred_p(bb)) {		split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));		gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));	} 	/* enumerate all local variables and forcibly initialize our targets */	FOR_EACH_LOCAL_DECL(cfun, i, var) {		tree type = TREE_TYPE(var); 		gcc_assert(DECL_P(var));		if (!auto_var_in_fn_p(var, current_function_decl))			continue; 		/* only care about structure types */		if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)			continue; 		/* if the type is of interest, examine the variable */		if (TYPE_USERSPACE(type))			initialize(var);	} 	return ret;} #define PASS_NAME structleak#define NO_GATE#define PROPERTIES_REQUIRED PROP_cfg#define TODO_FLAGS_FINISH TODO_verify_il | TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func | TODO_remove_unused_locals | TODO_update_ssa | TODO_ggc_collect | TODO_verify_flow#include "gcc-generate-gimple-pass.h" __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version){	int i;	const char * const plugin_name = plugin_info->base_name;	const int argc = plugin_info->argc;	const struct plugin_argument * const argv = plugin_info->argv;	bool enable = true; 	PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE); 	if (!plugin_default_version_check(version, &gcc_version)) {		error(G_("incompatible gcc/plugin versions"));		return 1;	} 	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {		inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);		enable = false;	} 	for (i = 0; i < argc; ++i) {		if (!strcmp(argv[i].key, "disable")) {			enable = false;			continue;		}		if (!strcmp(argv[i].key, "verbose")) {			verbose = true;			continue;		}		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);	} 	register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);	if (enable) {		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);		register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);	}	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); 	return 0;}