scripts/gcc-plugins/structleak_plugin.c - third_party/kernel - Git at Google

 /*
  * 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;
 #if BUILDING_GCC_VERSION >= 4007
 	user_attr.affects_type_identity	= true;
 #endif

 	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);
 #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),
 			"%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;
 }
	/*
	* 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;
	#if BUILDING_GCC_VERSION >= 4007
	user_attr.affects_type_identity = true;
	#endif

	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);
	#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),
	"%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;
	}