[PATCH v1 1/2] Add the initify gcc plugin

[Emese Revfy]

The kernel already has a mechanism to free up code and data memory that
is only used during kernel or module initialization.
This plugin will teach the compiler to find more such code and data that
can be freed after initialization.
It has two passes. The first one tries to find all functions that
can be become __init/__exit. The second one moves string constants
(local variables and function string arguments marked by
the nocapture attribute) only referenced in __init/__exit functions
to the __initconst/__exitconst sections.
It reduces memory usage. This plugin can be useful for embedded systems.

The instrumentation pass of the latent_entropy plugin must run after
the initify plugin to increase coverage.

Signed-off-by: Emese Revfy <re.emese@xxxxxxxxx>
---
 arch/Kconfig                         |   23 +
 include/asm-generic/vmlinux.lds.h    |    2 +
 scripts/Makefile.gcc-plugins         |    4 +
 scripts/gcc-plugins/initify_plugin.c | 1147 ++++++++++++++++++++++++++++++++++
 4 files changed, 1176 insertions(+)
 create mode 100644 scripts/gcc-plugins/initify_plugin.c

diff --git a/arch/Kconfig b/arch/Kconfig
index 9f8c6ee..35b01a4 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -417,6 +417,29 @@ config GCC_PLUGIN_LATENT_ENTROPY
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/
 
+config GCC_PLUGIN_INITIFY
+	bool "Free more kernel memory after init"
+	depends on GCC_PLUGINS
+	help
+	  The kernel has a mechanism to free up code and data memory that is
+	  only used during kernel or module initialization.  Enabling this
+	  feature will teach the compiler to find more such code and data
+	  that can be freed after initialization.
+
+	  This plugin is the part of grsecurity/PaX. More information at:
+	   * https://grsecurity.net/
+	   * https://pax.grsecurity.net/
+
+config GCC_PLUGIN_INITIFY_VERBOSE
+	bool "Verbose"
+	depends on GCC_PLUGIN_INITIFY
+	help
+	  Print all initified strings and all functions which should be
+	  __init/__exit.
+	  Note that the candidates identified for __init/__exit markings
+	  depend on the current kernel configuration and thus should be verified
+	  manually before the source code is patched.
+
 config HAVE_CC_STACKPROTECTOR
 	bool
 	help
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 6a67ab9..651980b 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -523,6 +523,7 @@
 	MEM_DISCARD(init.data)						\
 	KERNEL_CTORS()							\
 	MCOUNT_REC()							\
+	*(.init.rodata.str)						\
 	*(.init.rodata)							\
 	FTRACE_EVENTS()							\
 	TRACE_SYSCALLS()						\
@@ -547,6 +548,7 @@
 #define EXIT_DATA							\
 	*(.exit.data)							\
 	MEM_DISCARD(exit.data)						\
+	*(.exit.rodata.str)						\
 	MEM_DISCARD(exit.rodata)
 
 #define EXIT_TEXT							\
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 1f922df..0ce8392 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -12,6 +12,10 @@ ifdef CONFIG_GCC_PLUGINS
     DISABLE_LATENT_ENTROPY_PLUGIN			+= -fplugin-arg-latent_entropy_plugin-disable
   endif
 
+  gcc-plugin-$(CONFIG_GCC_PLUGIN_INITIFY)		+= initify_plugin.so
+  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_INITIFY)	+= -DINITIFY_PLUGIN -fplugin-arg-initify_plugin-search_init_exit_functions
+  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_INITIFY_VERBOSE)+= -fplugin-arg-initify_plugin-verbose
+
   ifdef CONFIG_GCC_PLUGIN_SANCOV
     ifeq ($(CFLAGS_KCOV),)
       # It is needed because of the gcc-plugin.sh and gcc version checks.
diff --git a/scripts/gcc-plugins/initify_plugin.c b/scripts/gcc-plugins/initify_plugin.c
new file mode 100644
index 0000000..d5dfce5
--- /dev/null
+++ b/scripts/gcc-plugins/initify_plugin.c
@@ -0,0 +1,1147 @@
+/*
+ * Copyright 2015-2016 by Emese Revfy <re.emese@xxxxxxxxx>
+ * Licensed under the GPL v2
+ *
+ * Homepage:
+ * https://github.com/ephox-gcc-plugins/initify
+ *
+ * This plugin has two passes. The first one tries to find all functions that
+ * can be become __init/__exit. The second one moves string constants
+ * (local variables and function string arguments marked by
+ * the nocapture attribute) only referenced in __init/__exit functions
+ * to __initconst/__exitconst sections.
+ * Based on an idea from Mathias Krause <minipli@xxxxxxxxxxx>.
+ *
+ * The instrumentation pass of the latent_entropy plugin must run after
+ * the initify plugin to increase coverage.
+ *
+ * Options:
+ * -fplugin-arg-initify_plugin-disable
+ * -fplugin-arg-initify_plugin-verbose
+ * -fplugin-arg-initify_plugin-print_missing_attr
+ * -fplugin-arg-initify_plugin-search_init_exit_functions
+ *
+ * Attribute: __attribute__((nocapture(x, y ...)))
+ *  The nocapture gcc attribute can be on functions only.
+ *  The attribute takes one or more unsigned integer constants as parameters
+ *  that specify the function argument(s) of const char* type to initify.
+ *  If the marked argument is a vararg then the plugin initifies
+ *  all vararg arguments.
+ *
+ * Usage:
+ * $ make
+ * $ make run
+ */
+
+#include "gcc-common.h"
+
+int plugin_is_GPL_compatible;
+
+static struct plugin_info initify_plugin_info = {
+	.version	=	"20160627vanilla",
+	.help		=	"disable\tturn off the initify plugin\n"
+				 "verbose\tprint all initified strings and all"
+				 " functions which should be __init/__exit\n"
+				 "print_missing_attr\tprint functions which"
+				 " can be marked by nocapture attribute\n"
+				 "search_init_exit_functions\tsearch function"
+				 " which should be marked by __init or __exit"
+				 " attribute\n"
+};
+
+static struct cgraph_2node_hook_list *node_duplication_hook_holder;
+#define ARGNUM_NONE 0
+static bool verbose, print_missing_attr, search_init_exit_functions;
+
+enum section_type {
+	INIT, EXIT, NONE
+};
+
+#if BUILDING_GCC_VERSION >= 5000
+typedef struct hash_set<const_gimple> gimple_set;
+
+static inline bool pointer_set_insert(gimple_set *visited, const_gimple stmt)
+{
+	return visited->add(stmt);
+}
+
+static inline bool pointer_set_contains(gimple_set *visited, const_gimple stmt)
+{
+	return visited->contains(stmt);
+}
+
+static inline gimple_set* pointer_set_create(void)
+{
+	return new hash_set<const_gimple>;
+}
+
+static inline void pointer_set_destroy(gimple_set *visited)
+{
+	delete visited;
+}
+#else
+typedef struct pointer_set_t gimple_set;
+#endif
+
+static void walk_def_stmt(bool *has_str_cst, gimple_set *visited, tree node);
+
+/* nocapture attribute:
+ *  * to mark nocapture function arguments. If used on a vararg argument
+ *    it applies to all of them that have no other uses.
+ *  * attribute value 0 is ignored to allow reusing print attribute arguments
+ */
+static tree handle_nocapture_attribute(tree *node, tree __unused name,
+					tree args, int __unused flags,
+					bool *no_add_attrs)
+{
+	tree orig_attr, arg;
+
+	*no_add_attrs = true;
+	switch (TREE_CODE(*node)) {
+	case FUNCTION_DECL:
+	case FUNCTION_TYPE:
+	case METHOD_TYPE:
+		break;
+
+	case TYPE_DECL: {
+		enum tree_code fn_code;
+		const_tree fntype = TREE_TYPE(*node);
+
+		fn_code = TREE_CODE(fntype);
+		if (fn_code == POINTER_TYPE)
+			fntype = TREE_TYPE(fntype);
+		fn_code = TREE_CODE(fntype);
+		if (fn_code == FUNCTION_TYPE || fn_code == METHOD_TYPE)
+			break;
+		/* FALLTHROUGH */
+	}
+
+	default:
+		debug_tree(*node);
+		error("%s: %qE attribute only applies to functions",
+			__func__, name);
+		return NULL_TREE;
+	}
+
+	for (arg = args; arg; arg = TREE_CHAIN(arg)) {
+		tree position = TREE_VALUE(arg);
+
+		if (TREE_CODE(position) != INTEGER_CST) {
+			error("%qE parameter of the %qE attribute isn't an integer (fn: %qE)",
+				position, name, *node);
+			return NULL_TREE;
+		}
+
+		if (tree_int_cst_lt(position, integer_minus_one_node)) {
+			error("%qE parameter of the %qE attribute less than 0 (fn: %qE)",
+				position, name, *node);
+			return NULL_TREE;
+		}
+	}
+
+	orig_attr = lookup_attribute("nocapture", DECL_ATTRIBUTES(*node));
+	if (orig_attr)
+		chainon(TREE_VALUE(orig_attr), args);
+	else
+		*no_add_attrs = false;
+
+	return NULL_TREE;
+}
+
+static struct attribute_spec nocapture_attr = {
+	.name				= "nocapture",
+	.min_length			= 1,
+	.max_length			= -1,
+	.decl_required			= true,
+	.type_required			= false,
+	.function_type_required		= false,
+	.handler			= handle_nocapture_attribute,
+#if BUILDING_GCC_VERSION >= 4007
+	.affects_type_identity		= false
+#endif
+};
+
+static void register_attributes(void __unused *event_data, void __unused *data)
+{
+	register_attribute(&nocapture_attr);
+}
+
+/* Determine whether the function is in the init or exit sections. */
+static enum section_type get_init_exit_section(const_tree decl)
+{
+	const char *str;
+	const_tree section, attr_value;
+
+	section = lookup_attribute("section", DECL_ATTRIBUTES(decl));
+	if (!section)
+		return NONE;
+
+	attr_value = TREE_VALUE(section);
+	gcc_assert(attr_value != NULL_TREE);
+	gcc_assert(list_length(attr_value) == 1);
+
+	str = TREE_STRING_POINTER(TREE_VALUE(attr_value));
+
+	if (!strncmp(str, ".init.", 6))
+		return INIT;
+	if (!strncmp(str, ".exit.", 6))
+		return EXIT;
+	return NONE;
+}
+
+static tree get_string_cst(tree var)
+{
+	if (var == NULL_TREE)
+		return NULL_TREE;
+
+	if (TREE_CODE(var) == STRING_CST)
+		return var;
+
+	switch (TREE_CODE_CLASS(TREE_CODE(var))) {
+	case tcc_expression:
+	case tcc_reference: {
+		int i;
+
+		for (i = 0; i < TREE_OPERAND_LENGTH(var); i++) {
+			tree ret = get_string_cst(TREE_OPERAND(var, i));
+			if (ret != NULL_TREE)
+				return ret;
+		}
+		break;
+	}
+
+	default:
+		break;
+	}
+
+	return NULL_TREE;
+}
+
+static bool set_init_exit_section(tree decl)
+{
+	gcc_assert(DECL_P(decl));
+
+	if (get_init_exit_section(decl) != NONE)
+		return false;
+
+	if (get_init_exit_section(current_function_decl) == INIT)
+		set_decl_section_name(decl, ".init.rodata.str");
+	else
+		set_decl_section_name(decl, ".exit.rodata.str");
+	return true;
+}
+
+/* Syscalls are always nocapture functions. */
+static bool is_syscall(const_tree fn)
+{
+	if (!strncmp(DECL_NAME_POINTER(fn), "sys_", 4))
+		return true;
+
+	if (!strncmp(DECL_NAME_POINTER(fn), "sys32_", 6))
+		return true;
+
+	if (!strncmp(DECL_NAME_POINTER(fn), "compat_sys_", 11))
+		return true;
+
+	return false;
+}
+
+static bool is_nocapture_param(const_tree fndecl, int fn_arg_count)
+{
+	const_tree attr, attr_val;
+	int fntype_arg_len;
+
+	if (is_syscall(fndecl))
+		return true;
+
+	fntype_arg_len = type_num_arguments(TREE_TYPE(fndecl));
+	attr = lookup_attribute("nocapture", DECL_ATTRIBUTES(fndecl));
+	if (attr == NULL_TREE)
+		return false;
+
+	for (attr_val = TREE_VALUE(attr); attr_val;
+		attr_val = TREE_CHAIN(attr_val)) {
+		int attr_arg_val = (int)tree_to_shwi(TREE_VALUE(attr_val));
+
+		if (attr_arg_val == -1)
+			return true;
+		if (attr_arg_val == fn_arg_count)
+			return true;
+		if (attr_arg_val > fntype_arg_len &&
+					fn_arg_count >= attr_arg_val)
+			return true;
+	}
+
+	return false;
+}
+
+static bool is_same_vardecl(const_tree op, const_tree vardecl)
+{
+	const_tree decl;
+
+	if (op == vardecl)
+		return true;
+	if (TREE_CODE(op) == SSA_NAME)
+		decl = SSA_NAME_VAR(op);
+	else
+		decl = op;
+	if (decl == NULL_TREE || !DECL_P(decl))
+		return false;
+
+	return DECL_NAME(decl) &&
+		!strcmp(DECL_NAME_POINTER(decl), DECL_NAME_POINTER(vardecl));
+}
+
+static bool search_same_vardecl(const_tree value, const_tree vardecl)
+{
+	int i;
+
+	for (i = 0; i < TREE_OPERAND_LENGTH(value); i++) {
+		const_tree op = TREE_OPERAND(value, i);
+
+		if (op == NULL_TREE)
+			continue;
+		if (is_same_vardecl(op, vardecl))
+			return true;
+		if (search_same_vardecl(op, vardecl))
+			return true;
+	}
+	return false;
+}
+
+static bool check_constructor(const_tree constructor, const_tree vardecl)
+{
+	unsigned HOST_WIDE_INT cnt __unused;
+	tree value;
+
+	FOR_EACH_CONSTRUCTOR_VALUE(CONSTRUCTOR_ELTS(constructor), cnt, value) {
+		if (TREE_CODE(value) == CONSTRUCTOR)
+			return check_constructor(value, vardecl);
+		if (is_gimple_constant(value))
+			continue;
+
+		gcc_assert(TREE_OPERAND_LENGTH(value) > 0);
+		if (search_same_vardecl(value, vardecl))
+			return true;
+	}
+	return false;
+}
+
+static bool compare_ops(const_tree vardecl, tree op)
+{
+	if (TREE_CODE(op) == TREE_LIST)
+		op = TREE_VALUE(op);
+	if (TREE_CODE(op) == SSA_NAME)
+		op = SSA_NAME_VAR(op);
+	if (op == NULL_TREE)
+		return false;
+
+	switch (TREE_CODE_CLASS(TREE_CODE(op))) {
+	case tcc_declaration:
+		return is_same_vardecl(op, vardecl);
+
+	case tcc_exceptional:
+		return check_constructor(op, vardecl);
+
+	case tcc_constant:
+	case tcc_statement:
+	case tcc_comparison:
+		return false;
+
+	default:
+		break;
+	}
+
+	gcc_assert(TREE_OPERAND_LENGTH(op) > 0);
+	return search_same_vardecl(op, vardecl);
+}
+
+static bool search_capture_use(const_tree vardecl, gimple stmt)
+{
+	unsigned int i;
+
+	for (i = 0; i < gimple_num_ops(stmt); i++) {
+		unsigned int arg_count;
+		const_tree fndecl, arg;
+		tree op = *(gimple_op_ptr(stmt, i));
+
+		if (op == NULL_TREE)
+			continue;
+		if (is_gimple_constant(op))
+			continue;
+
+		if (!compare_ops(vardecl, op))
+			continue;
+
+		if (!is_gimple_call(stmt))
+			return true;
+
+		/* return, fndecl */
+		gcc_assert(i >= 3);
+		arg_count = i - 2;
+
+		arg = gimple_call_arg(stmt, arg_count - 1);
+		gcc_assert(TREE_CODE(TREE_TYPE(arg)) == POINTER_TYPE);
+
+		fndecl = gimple_call_fndecl(stmt);
+		if (is_nocapture_param(fndecl, (int)arg_count))
+			continue;
+
+		gcc_assert(fndecl != NULL_TREE);
+
+		/*
+		 * These are potentially nocapture functions that must be
+		 * checked manually.
+		 */
+		if (print_missing_attr)
+			inform(gimple_location(stmt), "nocapture attribute is missing (fn: %E, arg: %u)\n",
+							fndecl, arg_count);
+		return true;
+
+	}
+	return false;
+}
+
+static bool is_in_capture_init(const_tree vardecl)
+{
+	unsigned int i __unused;
+	tree var;
+
+	FOR_EACH_LOCAL_DECL(cfun, i, var) {
+		const_tree initial = DECL_INITIAL(var);
+
+		if (DECL_EXTERNAL(var))
+			continue;
+		if (initial == NULL_TREE)
+			continue;
+		if (TREE_CODE(initial) != CONSTRUCTOR)
+			continue;
+
+		gcc_assert(TREE_CODE(TREE_TYPE(var)) == RECORD_TYPE ||
+								DECL_P(var));
+		if (check_constructor(initial, vardecl))
+			return true;
+	}
+	return false;
+}
+
+static bool has_capture_use_local_var(const_tree vardecl)
+{
+	basic_block bb;
+
+	if (is_in_capture_init(vardecl))
+		return true;
+
+	FOR_EACH_BB_FN(bb, cfun) {
+		gimple_stmt_iterator gsi;
+
+		for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
+			if (search_capture_use(vardecl, gsi_stmt(gsi)))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+/* Search local variables that have only nocapture uses. */
+static void find_local_str(void)
+{
+	unsigned int i __unused;
+	tree var;
+
+	FOR_EACH_LOCAL_DECL(cfun, i, var) {
+		tree str, init_val;
+
+		if (TREE_CODE(TREE_TYPE(var)) != ARRAY_TYPE)
+			continue;
+
+		init_val = DECL_INITIAL(var);
+		if (init_val == NULL_TREE || init_val == error_mark_node)
+			continue;
+		if (TREE_CODE(init_val) != STRING_CST)
+			continue;
+
+		if (has_capture_use_local_var(var))
+			continue;
+
+		str = get_string_cst(init_val);
+		gcc_assert(str);
+
+		if (set_init_exit_section(var) && verbose)
+			inform(DECL_SOURCE_LOCATION(var), "initified local var: %s: %s",
+				DECL_NAME_POINTER(current_function_decl),
+				TREE_STRING_POINTER(str));
+	}
+}
+
+static tree create_decl(tree node)
+{
+	tree str, decl, type, name;
+	location_t loc = DECL_SOURCE_LOCATION(current_function_decl);
+
+	str = get_string_cst(node);
+	type = TREE_TYPE(str);
+	gcc_assert(TREE_CODE(type) == ARRAY_TYPE);
+	gcc_assert(TREE_TYPE(type) != NULL_TREE &&
+			TREE_CODE(TREE_TYPE(type)) == INTEGER_TYPE);
+	name = create_tmp_var_name("initify");
+	decl = build_decl(loc, VAR_DECL, name, type);
+
+	DECL_INITIAL(decl) = str;
+	DECL_CONTEXT(decl) = current_function_decl;
+	DECL_ARTIFICIAL(decl) = 1;
+
+	TREE_STATIC(decl) = 1;
+	TREE_READONLY(decl) = 1;
+	TYPE_READONLY(TREE_TYPE(TREE_TYPE(decl))) = 1;
+	TREE_ADDRESSABLE(decl) = 1;
+	TREE_USED(decl) = 1;
+
+	add_referenced_var(decl);
+	add_local_decl(cfun, decl);
+
+	varpool_add_new_variable(decl);
+	varpool_mark_needed_node(varpool_node(decl));
+
+	DECL_CHAIN(decl) = BLOCK_VARS(DECL_INITIAL(current_function_decl));
+	BLOCK_VARS(DECL_INITIAL(current_function_decl)) = decl;
+
+	return build_fold_addr_expr_loc(loc, decl);
+}
+
+static void set_section_call_assign(gimple stmt, tree node, unsigned int num)
+{
+	tree decl;
+
+	decl = create_decl(node);
+
+	switch (gimple_code(stmt)) {
+	case GIMPLE_ASSIGN:
+		gcc_assert(gimple_num_ops(stmt) == 2);
+		gimple_assign_set_rhs1(stmt, decl);
+		break;
+
+	case GIMPLE_CALL:
+		gimple_call_set_arg(stmt, num, decl);
+		break;
+
+	default:
+		debug_gimple_stmt(stmt);
+		error("%s: unknown gimple code", __func__);
+		gcc_unreachable();
+	}
+
+	update_stmt(stmt);
+
+	if (set_init_exit_section(TREE_OPERAND(decl, 0)) && verbose)
+		inform(gimple_location(stmt), "initified function arg: %E: [%E]",
+				current_function_decl, get_string_cst(node));
+}
+
+static tree initify_create_new_var(tree type)
+{
+	tree new_var = create_tmp_var(type, "initify");
+
+	add_referenced_var(new_var);
+	mark_sym_for_renaming(new_var);
+	return new_var;
+}
+
+static void initify_create_new_phi_arg(tree ssa_var, gphi *stmt, unsigned int i)
+{
+	gassign *assign;
+	gimple_stmt_iterator gsi;
+	basic_block arg_bb;
+	tree decl, arg;
+
+	arg = gimple_phi_arg_def(stmt, i);
+	decl = create_decl(arg);
+
+	assign = gimple_build_assign(ssa_var, decl);
+
+	arg_bb = gimple_phi_arg_edge(stmt, i)->src;
+	gcc_assert(arg_bb->index != 0);
+
+	gsi = gsi_after_labels(arg_bb);
+	gsi_insert_before(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	if (set_init_exit_section(TREE_OPERAND(decl, 0)) && verbose)
+		inform(gimple_location(stmt), "initified local var, phi arg: %E: [%E]",
+			current_function_decl, get_string_cst(arg));
+}
+
+static void set_section_phi(bool *has_str_cst, gimple_set *visited, gphi *stmt)
+{
+	tree result, ssa_var;
+	unsigned int i;
+
+	result = gimple_phi_result(stmt);
+	ssa_var = initify_create_new_var(TREE_TYPE(result));
+
+	for (i = 0; i < gimple_phi_num_args(stmt); i++) {
+		tree arg = gimple_phi_arg_def(stmt, i);
+
+		if (get_string_cst(arg) == NULL_TREE)
+			walk_def_stmt(has_str_cst, visited, arg);
+		else
+			initify_create_new_phi_arg(ssa_var, stmt, i);
+	}
+}
+
+static void walk_def_stmt(bool *has_str_cst, gimple_set *visited, tree node)
+{
+	gimple def_stmt;
+	const_tree parm_decl;
+
+	if (!*has_str_cst)
+		return;
+
+	if (TREE_CODE(node) != SSA_NAME) {
+		*has_str_cst = false;
+		return;
+	}
+
+	parm_decl = SSA_NAME_VAR(node);
+	if (parm_decl != NULL_TREE && TREE_CODE(parm_decl) == PARM_DECL) {
+		*has_str_cst = false;
+		return;
+	}
+
+	def_stmt = SSA_NAME_DEF_STMT(node);
+	if (pointer_set_insert(visited, def_stmt))
+		return;
+
+	switch (gimple_code(def_stmt)) {
+	case GIMPLE_NOP:
+	case GIMPLE_CALL:
+	case GIMPLE_ASM:
+	case GIMPLE_RETURN:
+		*has_str_cst = false;
+		return;
+
+	case GIMPLE_PHI:
+		set_section_phi(has_str_cst, visited, as_a_gphi(def_stmt));
+		return;
+
+	case GIMPLE_ASSIGN: {
+		tree rhs1, str;
+
+		if (gimple_num_ops(def_stmt) != 2)
+			return;
+
+		rhs1 = gimple_assign_rhs1(def_stmt);
+		walk_def_stmt(has_str_cst, visited, rhs1);
+		if (!*has_str_cst)
+			return;
+		str = get_string_cst(rhs1);
+		if (str != NULL_TREE)
+			set_section_call_assign(def_stmt, rhs1, 0);
+		return;
+	}
+
+	default:
+		debug_gimple_stmt(def_stmt);
+		error("%s: unknown gimple code", __func__);
+		gcc_unreachable();
+	}
+}
+
+/* Search constant strings assigned to variables. */
+static void search_var_param(gcall *stmt)
+{
+	unsigned int num;
+
+	for (num = 0; num < gimple_call_num_args(stmt); num++) {
+		gimple_set *visited;
+		const_tree type, fndecl;
+		bool has_str_cst = true;
+		tree str, arg = gimple_call_arg(stmt, num);
+
+		str = get_string_cst(arg);
+		if (str != NULL_TREE)
+			continue;
+
+		if (TREE_CODE(TREE_TYPE(arg)) != POINTER_TYPE)
+			continue;
+		type = TREE_TYPE(TREE_TYPE(arg));
+		if (!TYPE_STRING_FLAG(type))
+			continue;
+		fndecl = gimple_call_fndecl(stmt);
+		if (!is_nocapture_param(fndecl, num + 1))
+			continue;
+
+		visited = pointer_set_create();
+		walk_def_stmt(&has_str_cst, visited, arg);
+		pointer_set_destroy(visited);
+	}
+}
+
+/* Search constant strings passed as arguments. */
+static void search_str_param(gcall *stmt)
+{
+	unsigned int num;
+
+	for (num = 0; num < gimple_call_num_args(stmt); num++) {
+		const_tree fndecl;
+		tree str, arg = gimple_call_arg(stmt, num);
+
+		str = get_string_cst(arg);
+		if (str == NULL_TREE)
+			continue;
+
+		fndecl = gimple_call_fndecl(stmt);
+		if (is_nocapture_param(fndecl, num + 1))
+			set_section_call_assign(stmt, arg, num);
+	}
+}
+
+static bool has_nocapture_param(const_tree fndecl)
+{
+	const_tree attr;
+
+	if (fndecl == NULL_TREE)
+		return false;
+
+	if (is_syscall(fndecl))
+		return true;
+
+	attr = lookup_attribute("nocapture", DECL_ATTRIBUTES(fndecl));
+	return attr != NULL_TREE;
+}
+
+/* Search constant strings in arguments of nocapture functions. */
+static void search_const_strs(void)
+{
+	basic_block bb;
+
+	FOR_EACH_BB_FN(bb, cfun) {
+		gimple_stmt_iterator gsi;
+
+		for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
+			gcall *call_stmt;
+			gimple stmt = gsi_stmt(gsi);
+
+			if (!is_gimple_call(stmt))
+				continue;
+
+			call_stmt = as_a_gcall(stmt);
+			if (!has_nocapture_param(gimple_call_fndecl(call_stmt)))
+				continue;
+			search_str_param(call_stmt);
+			search_var_param(call_stmt);
+		}
+	}
+}
+
+/*
+ * Find and move constant strings to the proper init or exit read-only
+ * data section.
+ */
+static unsigned int initify_execute(void)
+{
+	if (get_init_exit_section(current_function_decl) == NONE)
+		return 0;
+
+	find_local_str();
+	search_const_strs();
+
+	return 0;
+}
+
+#define PASS_NAME initify
+#define NO_GATE
+#define TODO_FLAGS_FINISH	TODO_dump_func | TODO_verify_ssa | \
+				TODO_verify_stmts | \
+				TODO_remove_unused_locals | \
+				TODO_cleanup_cfg | TODO_ggc_collect | \
+				TODO_verify_flow | TODO_update_ssa
+
+#include "gcc-generate-gimple-pass.h"
+
+static bool search_init_functions_gate(void)
+{
+	return search_init_exit_functions;
+}
+
+/*
+ * If the function is called by only __init/__exit functions then it can become
+ * an __init/__exit function as well.
+ */
+static bool should_init_exit(struct cgraph_node *callee)
+{
+	struct cgraph_edge *e;
+	bool only_init_callers;
+	const_tree callee_decl = NODE_DECL(callee);
+
+	if (NODE_SYMBOL(callee)->aux != (void *)NONE)
+		return false;
+	if (get_init_exit_section(callee_decl) != NONE)
+		return false;
+
+	/* If gcc isn't in LTO mode then we can handle only static functions. */
+	if (!in_lto_p && TREE_PUBLIC(callee_decl))
+		return false;
+
+	if (NODE_SYMBOL(callee)->address_taken)
+		return false;
+
+	e = callee->callers;
+	if (!e)
+		return false;
+
+	only_init_callers = true;
+	for (; e; e = e->next_caller) {
+		enum section_type caller_section;
+		struct cgraph_node *caller = e->caller;
+
+		caller_section = get_init_exit_section(NODE_DECL(caller));
+		if (caller_section == NONE &&
+			NODE_SYMBOL(caller)->aux == (void *)NONE)
+			only_init_callers = false;
+	}
+
+	return only_init_callers;
+}
+
+static bool inherit_section(struct cgraph_node *callee,
+				struct cgraph_node *caller,
+				enum section_type curfn_section)
+{
+	if (curfn_section == NONE)
+		curfn_section = (enum section_type)(unsigned long)
+					NODE_SYMBOL(caller)->aux;
+
+	if (curfn_section == EXIT && NODE_SYMBOL(callee)->aux == (void *)INIT)
+		goto set_section;
+
+	if (!should_init_exit(callee))
+		return false;
+
+	gcc_assert(NODE_SYMBOL(callee)->aux == (void *)NONE);
+
+set_section:
+	NODE_SYMBOL(callee)->aux = (void *)curfn_section;
+	return true;
+}
+
+/*
+ * Try to propagate __init/__exit to callees in __init/__exit functions.
+ * If a function is called by __init and __exit functions as well then it can be
+ * an __exit function at most.
+ */
+static bool search_init_exit_callers(void)
+{
+	struct cgraph_node *node;
+	bool change = false;
+
+	FOR_EACH_FUNCTION(node) {
+		struct cgraph_edge *e;
+		enum section_type section;
+		const_tree cur_fndecl = NODE_DECL(node);
+
+		if (DECL_BUILT_IN(cur_fndecl))
+			continue;
+
+		section = get_init_exit_section(cur_fndecl);
+		if (section == NONE && NODE_SYMBOL(node)->aux == (void *)NONE)
+			continue;
+
+		for (e = node->callees; e; e = e->next_callee) {
+			if (e->callee->global.inlined_to)
+				continue;
+			if (inherit_section(e->callee, node, section))
+				change = true;
+		}
+	}
+	return change;
+}
+
+/* We can't move functions to the init/exit sections from certain sections. */
+static bool can_move_to_init_exit(const_tree fndecl)
+{
+	const char *section_name;
+
+#if BUILDING_GCC_VERSION < 5000
+	const_tree section_tree = DECL_SECTION_NAME(fndecl);
+
+	if (section_tree == NULL_TREE)
+		return true;
+
+	section_name = TREE_STRING_POINTER(section_tree);
+#else
+	section_name = DECL_SECTION_NAME(fndecl);
+	if (!section_name)
+		return true;
+#endif
+
+	if (!strcmp(section_name, ".ref.text\000"))
+		return true;
+
+	if (!strcmp(section_name, ".meminit.text\000"))
+		return false;
+
+	inform(DECL_SOURCE_LOCATION(fndecl), "Section of %qE: %s\n",
+						fndecl, section_name);
+	gcc_unreachable();
+}
+
+static void move_function_to_init_exit_text(struct cgraph_node *node)
+{
+	const char *section_name;
+	tree id, attr;
+	tree section_str, attr_args, fndecl = NODE_DECL(node);
+
+	if (NODE_SYMBOL(node)->aux == (void *)NONE)
+		return;
+
+	if (!can_move_to_init_exit(fndecl))
+		return;
+
+	if (verbose) {
+		const char *attr_name;
+		location_t loc = DECL_SOURCE_LOCATION(fndecl);
+
+		attr_name = NODE_SYMBOL(node)->aux ==
+					(void *)INIT ? "__init" : "__exit";
+
+		if (in_lto_p && TREE_PUBLIC(fndecl))
+			inform(loc, "%s attribute is missing from the %qE function (public)",
+							attr_name, fndecl);
+
+		if (!in_lto_p && !TREE_PUBLIC(fndecl))
+			inform(loc, "%s attribute is missing from the %qE function (static)",
+							attr_name, fndecl);
+	}
+
+	if (in_lto_p)
+		return;
+
+	/* Add the init/exit section attribute to the function declaration. */
+	DECL_ATTRIBUTES(fndecl) = copy_list(DECL_ATTRIBUTES(fndecl));
+
+	section_name = NODE_SYMBOL(node)->aux ==
+				(void *)INIT ? ".init.text" : ".exit.text";
+	section_str = build_string(strlen(section_name) + 1, section_name);
+	TREE_READONLY(section_str) = 1;
+	TREE_STATIC(section_str) = 1;
+	attr_args = build_tree_list(NULL_TREE, section_str);
+
+	id = get_identifier("__section__");
+	attr = DECL_ATTRIBUTES(fndecl);
+	DECL_ATTRIBUTES(fndecl) = tree_cons(id, attr_args, attr);
+
+#if BUILDING_GCC_VERSION < 5000
+	DECL_SECTION_NAME(fndecl) = section_str;
+#endif
+	set_decl_section_name(fndecl, section_name);
+}
+
+/* Find all functions that can become __init/__exit functions */
+static unsigned int search_init_functions_execute(void)
+{
+	struct cgraph_node *node;
+
+	if (flag_lto && !in_lto_p)
+		return 0;
+
+	FOR_EACH_FUNCTION(node)
+		NODE_SYMBOL(node)->aux = (void *)NONE;
+
+	while (search_init_exit_callers()) {};
+
+	FOR_EACH_FUNCTION(node) {
+		move_function_to_init_exit_text(node);
+
+		NODE_SYMBOL(node)->aux = NULL;
+	}
+
+	return 0;
+}
+
+/* Find the specified argument in the clone */
+static unsigned int orig_argnum_on_clone(struct cgraph_node *new_node,
+						unsigned int orig_argnum)
+{
+	bitmap args_to_skip;
+	unsigned int i, new_argnum = orig_argnum;
+
+	gcc_assert(new_node->clone_of && new_node->clone.tree_map);
+	args_to_skip = new_node->clone.args_to_skip;
+	if (bitmap_bit_p(args_to_skip, orig_argnum - 1))
+		return 0;
+
+	for (i = 0; i < orig_argnum; i++) {
+		if (bitmap_bit_p(args_to_skip, i))
+			new_argnum--;
+	}
+	return new_argnum + 1;
+}
+
+/* Determine if a cloned function has all the original arguments */
+static bool unchanged_arglist(struct cgraph_node *new_node,
+				struct cgraph_node *old_node)
+{
+	const_tree new_decl_list, old_decl_list;
+
+	if (new_node->clone_of && new_node->clone.tree_map)
+		return !new_node->clone.args_to_skip;
+
+	new_decl_list = DECL_ARGUMENTS(NODE_DECL(new_node));
+	old_decl_list = DECL_ARGUMENTS(NODE_DECL(old_node));
+	if (new_decl_list != NULL_TREE && old_decl_list != NULL_TREE)
+		gcc_assert(list_length(new_decl_list) ==
+						list_length(old_decl_list));
+
+	return true;
+}
+
+static void initify_node_duplication_hook(struct cgraph_node *src,
+						struct cgraph_node *dst,
+						void *data __unused)
+{
+	const_tree orig_fndecl, orig_decl_lst, arg;
+	unsigned int orig_argnum = 0;
+
+	if (unchanged_arglist(dst, src))
+		return;
+
+	orig_fndecl = NODE_DECL(src);
+	if (!has_nocapture_param(orig_fndecl))
+		return;
+
+	orig_decl_lst = DECL_ARGUMENTS(orig_fndecl);
+	gcc_assert(orig_decl_lst != NULL_TREE);
+
+	for (arg = orig_decl_lst; arg; arg = TREE_CHAIN(arg), orig_argnum++) {
+		if (!is_nocapture_param(orig_fndecl, orig_argnum))
+			continue;
+		if (orig_argnum_on_clone(dst, orig_argnum) == 0)
+			continue;
+
+		debug_cgraph_node(dst);
+		debug_cgraph_node(src);
+		gcc_unreachable();
+	}
+}
+
+static void initify_register_hooks(void)
+{
+	static bool init_p = false;
+
+	if (init_p)
+		return;
+	init_p = true;
+
+	node_duplication_hook_holder =
+		cgraph_add_node_duplication_hook(&initify_node_duplication_hook,
+									NULL);
+}
+
+static void search_init_functions_generate_summary(void)
+{
+	initify_register_hooks();
+}
+
+static void search_init_functions_read_summary(void)
+{
+	initify_register_hooks();
+}
+
+#define PASS_NAME search_init_functions
+#define NO_WRITE_SUMMARY
+#define NO_READ_OPTIMIZATION_SUMMARY
+#define NO_WRITE_OPTIMIZATION_SUMMARY
+#define NO_STMT_FIXUP
+#define NO_FUNCTION_TRANSFORM
+#define NO_VARIABLE_TRANSFORM
+
+#include "gcc-generate-ipa-pass.h"
+
+static unsigned int (*old_section_type_flags)(tree decl, const char *name,
+								int reloc);
+
+static unsigned int initify_section_type_flags(tree decl, const char *name,
+								int reloc)
+{
+	if (!strcmp(name, ".init.rodata.str") ||
+					!strcmp(name, ".exit.rodata.str")) {
+		gcc_assert(TREE_CODE(decl) == VAR_DECL);
+		gcc_assert(DECL_INITIAL(decl));
+		gcc_assert(TREE_CODE(DECL_INITIAL(decl)) == STRING_CST);
+
+		return 1 | SECTION_MERGE | SECTION_STRINGS;
+	}
+
+	return old_section_type_flags(decl, name, reloc);
+}
+
+static void initify_start_unit(void __unused *gcc_data,
+						void __unused *user_data)
+{
+	old_section_type_flags = targetm.section_type_flags;
+	targetm.section_type_flags = initify_section_type_flags;
+}
+
+int plugin_init(struct plugin_name_args *plugin_info,
+					struct plugin_gcc_version *version)
+{
+	struct register_pass_info initify_pass_info, search_init_functions_info;
+	int i;
+	const int argc = plugin_info->argc;
+	bool enabled = true;
+	const struct plugin_argument * const argv = plugin_info->argv;
+	const char * const plugin_name = plugin_info->base_name;
+
+	initify_pass_info.pass				= make_initify_pass();
+	initify_pass_info.reference_pass_name		= "nrv";
+	initify_pass_info.ref_pass_instance_number	= 1;
+	initify_pass_info.pos_op			= PASS_POS_INSERT_AFTER;
+
+	search_init_functions_info.pass = make_search_init_functions_pass();
+	search_init_functions_info.reference_pass_name		= "inline";
+	search_init_functions_info.ref_pass_instance_number	= 1;
+	search_init_functions_info.pos_op = PASS_POS_INSERT_AFTER;
+
+	if (!plugin_default_version_check(version, &gcc_version)) {
+		error(G_("incompatible gcc/plugin versions"));
+		return 1;
+	}
+
+	for (i = 0; i < argc; ++i) {
+		if (!(strcmp(argv[i].key, "disable"))) {
+			enabled = false;
+			continue;
+		}
+		if (!strcmp(argv[i].key, "verbose")) {
+			verbose = true;
+			continue;
+		}
+		if (!strcmp(argv[i].key, "print_missing_attr")) {
+			print_missing_attr = true;
+			continue;
+		}
+		if (!strcmp(argv[i].key, "search_init_exit_functions")) {
+			search_init_exit_functions = true;
+			continue;
+		}
+
+		error(G_("unkown option '-fplugin-arg-%s-%s'"), plugin_name,
+								argv[i].key);
+	}
+
+	register_callback(plugin_name, PLUGIN_INFO, NULL, &initify_plugin_info);
+	if (enabled) {
+		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
+							&initify_pass_info);
+		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
+						&search_init_functions_info);
+		register_callback(plugin_name, PLUGIN_START_UNIT,
+						initify_start_unit, NULL);
+	}
+	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes,
+									NULL);
+
+	return 0;
+}
-- 
2.8.1