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;