[mirror_ubuntu-bionic-kernel.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: 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;
}
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	*
	14	* Homepage: http://pax.grsecurity.net/
	15	*
	16	* Options:
	17	* -fplugin-arg-structleak_plugin-disable
	18	* -fplugin-arg-structleak_plugin-verbose
	19	*
	20	* Usage:
	21	* $ # for 4.5/4.6/C based 4.7
	22	* $ 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
	23	* $ # for C++ based 4.7/4.8+
	24	* $ 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
	25	* $ gcc -fplugin=./structleak_plugin.so test.c -O2
	26	*
	27	* TODO: eliminate redundant initializers
	28	* increase type coverage
	29	*/
	30
	31	#include "gcc-common.h"
	32
	33	/* unused C type flag in all versions 4.5-6 */
	34	#define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE)
	35
	36	__visible int plugin_is_GPL_compatible;
	37
	38	static struct plugin_info structleak_plugin_info = {
	39	.version = "201607271510vanilla",
	40	.help = "disable\tdo not activate plugin\n"
	41	"verbose\tprint all initialized variables\n",
	42	};
	43
	44	static bool verbose;
	45
	46	static tree handle_user_attribute(tree node, tree name, tree args, int flags, bool no_add_attrs)
	47	{
	48	*no_add_attrs = true;
	49
	50	/* check for types? for now accept everything linux has to offer */
	51	if (TREE_CODE(*node) != FIELD_DECL)
	52	return NULL_TREE;
	53
	54	*no_add_attrs = false;
	55	return NULL_TREE;
	56	}
	57
	58	static struct attribute_spec user_attr = {
	59	.name = "user",
	60	.min_length = 0,
	61	.max_length = 0,
	62	.decl_required = false,
	63	.type_required = false,
	64	.function_type_required = false,
65	.handler = handle_user_attribute,
66	#if BUILDING_GCC_VERSION >= 4007
67	.affects_type_identity = true
68	#endif
69	};
70
71	static void register_attributes(void event_data, void data)
72	{
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;
124
125	/* this is the original entry bb before the forced split */
126	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
127
128	/* first check if variable is already initialized, warn otherwise */
129	for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
130	gimple stmt = gsi_stmt(gsi);
131	tree rhs1;
132
133	/* we're looking for an assignment of a single rhs... */
134	if (!gimple_assign_single_p(stmt))
135	continue;
136	rhs1 = gimple_assign_rhs1(stmt);
137	#if BUILDING_GCC_VERSION >= 4007
138	/* ... of a non-clobbering expression... */
139	if (TREE_CLOBBER_P(rhs1))
140	continue;
141	#endif
142	/* ... to our variable... */
143	if (gimple_get_lhs(stmt) != var)
144	continue;
145	/* if it's an initializer then we're good */
146	if (TREE_CODE(rhs1) == CONSTRUCTOR)
147	return;
148	}
149
150	/* these aren't the 0days you're looking for */
151	if (verbose)
152	inform(DECL_SOURCE_LOCATION(var),
153	"userspace variable will be forcibly initialized");
154
155	/* build the initializer expression */
156	initializer = build_constructor(TREE_TYPE(var), NULL);
157
158	/* build the initializer stmt */
159	init_stmt = gimple_build_assign(var, initializer);
160	gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
161	gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
162	update_stmt(init_stmt);
163	}
164
165	static unsigned int structleak_execute(void)
166	{
167	basic_block bb;
168	unsigned int ret = 0;
169	tree var;
170	unsigned int i;
171
172	/* split the first bb where we can put the forced initializers */
173	gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
174	bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
175	if (!single_pred_p(bb)) {
176	split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
177	gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
178	}
179
180	/* enumerate all local variables and forcibly initialize our targets */
181	FOR_EACH_LOCAL_DECL(cfun, i, var) {
182	tree type = TREE_TYPE(var);
183
184	gcc_assert(DECL_P(var));
185	if (!auto_var_in_fn_p(var, current_function_decl))
186	continue;
187
188	/* only care about structure types */
189	if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
190	continue;
191
192	/* if the type is of interest, examine the variable */
193	if (TYPE_USERSPACE(type))
194	initialize(var);
195	}
196
197	return ret;
198	}
199
200	#define PASS_NAME structleak
201	#define NO_GATE
202	#define PROPERTIES_REQUIRED PROP_cfg
203	#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
204	#include "gcc-generate-gimple-pass.h"
205
206	__visible int plugin_init(struct plugin_name_args plugin_info, struct plugin_gcc_version version)
207	{
208	int i;
209	const char * const plugin_name = plugin_info->base_name;
210	const int argc = plugin_info->argc;
211	const struct plugin_argument * const argv = plugin_info->argv;
212	bool enable = true;
213
214	PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
215
216	if (!plugin_default_version_check(version, &gcc_version)) {
217	error(G_("incompatible gcc/plugin versions"));
218	return 1;
219	}
220
221	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
222	inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
223	enable = false;
224	}
225
226	for (i = 0; i < argc; ++i) {
227	if (!strcmp(argv[i].key, "disable")) {
228	enable = false;
229	continue;
230	}
231	if (!strcmp(argv[i].key, "verbose")) {
232	verbose = true;
233	continue;
234	}
235	error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
236	}
237
238	register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
239	if (enable) {
240	register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
241	register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
242	}
243	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
244
245	return 0;
246	}