[linux-block.git] / scripts / gcc-plugins / structleak_plugin.c

/*
 * 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: https://pax.grsecurity.net/
 *
 * Options:
 * -fplugin-arg-structleak_plugin-disable
 * -fplugin-arg-structleak_plugin-verbose
 * -fplugin-arg-structleak_plugin-byref
 * -fplugin-arg-structleak_plugin-byref-all
 *
 * 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
 */

#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	= "20190125vanilla",
	.help		= "disable\tdo not activate plugin\n"
			  "byref\tinit structs passed by reference\n"
			  "byref-all\tinit anything passed by reference\n"
			  "verbose\tprint all initialized variables\n",
};

#define BYREF_STRUCT	1
#define BYREF_ALL	2

static bool verbose;
static int byref;

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 = { };

static void register_attributes(void *event_data, void *data)
{
	user_attr.name			= "user";
	user_attr.handler		= handle_user_attribute;
	user_attr.affects_type_identity	= true;

	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;
	tree type;

	/* 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);
		/* ... of a non-clobbering expression... */
		if (TREE_CLOBBER_P(rhs1))
			continue;
		/* ... 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),
			"%s variable will be forcibly initialized",
			(byref && TREE_ADDRESSABLE(var)) ? "byref"
							 : "userspace");

	/* build the initializer expression */
	type = TREE_TYPE(var);
	if (AGGREGATE_TYPE_P(type))
		initializer = build_constructor(type, NULL);
	else
		initializer = fold_convert(type, integer_zero_node);

	/* 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 unless byref-all */
		if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
			continue;

		/* if the type is of interest, examine the variable */
		if (TYPE_USERSPACE(type) ||
		    (byref && TREE_ADDRESSABLE(var)))
			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;
		}
		if (!strcmp(argv[i].key, "byref")) {
			byref = BYREF_STRUCT;
			continue;
		}
		if (!strcmp(argv[i].key, "byref-all")) {
			byref = BYREF_ALL;
			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;
}
Commit	Line	Data
c61f13ea KC	1	/*
	2	* Copyright 2013-2017 by PaX Team <pageexec@freemail.hu>
	3	* Licensed under the GPL v2
	4	*
	5	* Note: the choice of the license means that the compilation process is
	6	* NOT 'eligible' as defined by gcc's library exception to the GPL v3,
	7	* but for the kernel it doesn't matter since it doesn't link against
	8	* any of the gcc libraries
	9	*
	10	* gcc plugin to forcibly initialize certain local variables that could
	11	* otherwise leak kernel stack to userland if they aren't properly initialized
	12	* by later code
	13	*
496b24ec	14	* Homepage: https://pax.grsecurity.net/
c61f13ea KC	15	*
	16	* Options:
	17	* -fplugin-arg-structleak_plugin-disable
	18	* -fplugin-arg-structleak_plugin-verbose
81a56f6d	19	* -fplugin-arg-structleak_plugin-byref
f7dd2507	20	* -fplugin-arg-structleak_plugin-byref-all
c61f13ea KC	21	*
	22	* Usage:
	23	* $ # for 4.5/4.6/C based 4.7
	24	* $ 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
	25	* $ # for C++ based 4.7/4.8+
	26	* $ 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
	27	* $ gcc -fplugin=./structleak_plugin.so test.c -O2
	28	*
	29	* TODO: eliminate redundant initializers
c61f13ea KC	30	*/
	31
	32	#include "gcc-common.h"
	33
	34	/* unused C type flag in all versions 4.5-6 */
	35	#define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE)
	36
	37	__visible int plugin_is_GPL_compatible;
	38
	39	static struct plugin_info structleak_plugin_info = {
81a56f6d	40	.version = "20190125vanilla",
c61f13ea	41	.help = "disable\tdo not activate plugin\n"
81a56f6d KC	42	"byref\tinit structs passed by reference\n"
	43	"byref-all\tinit anything passed by reference\n"
	44	"verbose\tprint all initialized variables\n",
c61f13ea KC	45	};
c61f13ea KC	46
81a56f6d KC	47	#define BYREF_STRUCT 1
	48	#define BYREF_ALL 2
	49
c61f13ea	50	static bool verbose;
81a56f6d	51	static int byref;
c61f13ea KC	52
	53	static tree handle_user_attribute(tree node, tree name, tree args, int flags, bool no_add_attrs)
	54	{
	55	*no_add_attrs = true;
	56
	57	/* check for types? for now accept everything linux has to offer */
	58	if (TREE_CODE(*node) != FIELD_DECL)
	59	return NULL_TREE;
	60
	61	*no_add_attrs = false;
	62	return NULL_TREE;
	63	}
	64
b8672910	65	static struct attribute_spec user_attr = { };
c61f13ea KC	66
	67	static void register_attributes(void event_data, void data)
	68	{
b8672910 KC	69	user_attr.name = "user";
b8672910 KC	70	user_attr.handler = handle_user_attribute;
b8672910	71	user_attr.affects_type_identity = true;
b8672910	72
c61f13ea KC	73	register_attribute(&user_attr);
	74	}
	75
	76	static tree get_field_type(tree field)
	77	{
	78	return strip_array_types(TREE_TYPE(field));
	79	}
	80
	81	static bool is_userspace_type(tree type)
	82	{
	83	tree field;
	84
	85	for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) {
	86	tree fieldtype = get_field_type(field);
	87	enum tree_code code = TREE_CODE(fieldtype);
	88
	89	if (code == RECORD_TYPE \|\| code == UNION_TYPE)
	90	if (is_userspace_type(fieldtype))
	91	return true;
	92
	93	if (lookup_attribute("user", DECL_ATTRIBUTES(field)))
	94	return true;
	95	}
	96	return false;
	97	}
	98
	99	static void finish_type(void event_data, void data)
	100	{
	101	tree type = (tree)event_data;
	102
	103	if (type == NULL_TREE \|\| type == error_mark_node)
	104	return;
	105
	106	#if BUILDING_GCC_VERSION >= 5000
	107	if (TREE_CODE(type) == ENUMERAL_TYPE)
	108	return;
	109	#endif
	110
	111	if (TYPE_USERSPACE(type))
	112	return;
	113
	114	if (is_userspace_type(type))
	115	TYPE_USERSPACE(type) = 1;
	116	}
	117
	118	static void initialize(tree var)
	119	{
	120	basic_block bb;
	121	gimple_stmt_iterator gsi;
	122	tree initializer;
	123	gimple init_stmt;
81a56f6d	124	tree type;
c61f13ea KC	125
	126	/* this is the original entry bb before the forced split */
	127	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
	128
	129	/* first check if variable is already initialized, warn otherwise */
	130	for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
	131	gimple stmt = gsi_stmt(gsi);
	132	tree rhs1;
	133
	134	/* we're looking for an assignment of a single rhs... */
	135	if (!gimple_assign_single_p(stmt))
	136	continue;
	137	rhs1 = gimple_assign_rhs1(stmt);
c61f13ea KC	138	/* ... of a non-clobbering expression... */
	139	if (TREE_CLOBBER_P(rhs1))
	140	continue;
c61f13ea KC	141	/* ... to our variable... */
	142	if (gimple_get_lhs(stmt) != var)
	143	continue;
	144	/* if it's an initializer then we're good */
	145	if (TREE_CODE(rhs1) == CONSTRUCTOR)
	146	return;
	147	}
	148
	149	/* these aren't the 0days you're looking for */
	150	if (verbose)
	151	inform(DECL_SOURCE_LOCATION(var),
f7dd2507	152	"%s variable will be forcibly initialized",
81a56f6d KC	153	(byref && TREE_ADDRESSABLE(var)) ? "byref"
81a56f6d KC	154	: "userspace");
c61f13ea KC	155
c61f13ea KC	156	/* build the initializer expression */
81a56f6d KC	157	type = TREE_TYPE(var);
	158	if (AGGREGATE_TYPE_P(type))
	159	initializer = build_constructor(type, NULL);
	160	else
	161	initializer = fold_convert(type, integer_zero_node);
c61f13ea KC	162
	163	/* build the initializer stmt */
	164	init_stmt = gimple_build_assign(var, initializer);
	165	gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
	166	gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
	167	update_stmt(init_stmt);
	168	}
	169
	170	static unsigned int structleak_execute(void)
	171	{
	172	basic_block bb;
	173	unsigned int ret = 0;
	174	tree var;
	175	unsigned int i;
	176
	177	/* split the first bb where we can put the forced initializers */
	178	gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
	179	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
	180	if (!single_pred_p(bb)) {
	181	split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
	182	gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
	183	}
	184
	185	/* enumerate all local variables and forcibly initialize our targets */
	186	FOR_EACH_LOCAL_DECL(cfun, i, var) {
	187	tree type = TREE_TYPE(var);
	188
	189	gcc_assert(DECL_P(var));
	190	if (!auto_var_in_fn_p(var, current_function_decl))
	191	continue;
	192
81a56f6d KC	193	/* only care about structure types unless byref-all */
81a56f6d KC	194	if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
c61f13ea KC	195	continue;
	196
	197	/* if the type is of interest, examine the variable */
f7dd2507	198	if (TYPE_USERSPACE(type) \|\|
81a56f6d	199	(byref && TREE_ADDRESSABLE(var)))
c61f13ea KC	200	initialize(var);
	201	}
	202
	203	return ret;
	204	}
	205
	206	#define PASS_NAME structleak
	207	#define NO_GATE
	208	#define PROPERTIES_REQUIRED PROP_cfg
	209	#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
	210	#include "gcc-generate-gimple-pass.h"
	211
	212	__visible int plugin_init(struct plugin_name_args plugin_info, struct plugin_gcc_version version)
	213	{
	214	int i;
	215	const char * const plugin_name = plugin_info->base_name;
	216	const int argc = plugin_info->argc;
	217	const struct plugin_argument * const argv = plugin_info->argv;
	218	bool enable = true;
	219
	220	PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
	221
	222	if (!plugin_default_version_check(version, &gcc_version)) {
	223	error(G_("incompatible gcc/plugin versions"));
	224	return 1;
	225	}
	226
	227	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
	228	inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
	229	enable = false;
	230	}
	231
	232	for (i = 0; i < argc; ++i) {
	233	if (!strcmp(argv[i].key, "disable")) {
	234	enable = false;
	235	continue;
	236	}
	237	if (!strcmp(argv[i].key, "verbose")) {
	238	verbose = true;
	239	continue;
	240	}
81a56f6d KC	241	if (!strcmp(argv[i].key, "byref")) {
	242	byref = BYREF_STRUCT;
	243	continue;
	244	}
f7dd2507	245	if (!strcmp(argv[i].key, "byref-all")) {
81a56f6d	246	byref = BYREF_ALL;
f7dd2507 AB	247	continue;
f7dd2507 AB	248	}
c61f13ea KC	249	error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
	250	}
	251
	252	register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
	253	if (enable) {
	254	register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
	255	register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
	256	}
	257	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
	258
	259	return 0;
	260	}