Merge branch 'merge/randstruct' into for-next/gcc-plugins

6 files changed, 1061 insertions, 0 deletions

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 82335533620e..2e0e2eaa397f 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -29,6 +29,10 @@ ifdef CONFIG_GCC_PLUGINS
   gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)	+= -fplugin-arg-structleak_plugin-verbose
   gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= -DSTRUCTLEAK_PLUGIN
 
+  gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= randomize_layout_plugin.so
+  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= -DRANDSTRUCT_PLUGIN
+  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE)	+= -fplugin-arg-randomize_layout_plugin-performance-mode
+
   GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
 
   export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR
diff --git a/scripts/gcc-plugins/.gitignore b/scripts/gcc-plugins/.gitignore
new file mode 100644
index 000000000000..de92ed9e3d83
--- /dev/null
+++ b/scripts/gcc-plugins/.gitignore
@@ -0,0 +1 @@
+randomize_layout_seed.h
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index 8b29dc17c73c..214eb2335c31 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -18,6 +18,14 @@ endif
 
 export HOSTLIBS
 
+$(obj)/randomize_layout_plugin.o: $(objtree)/$(obj)/randomize_layout_seed.h
+quiet_cmd_create_randomize_layout_seed = GENSEED $@
+cmd_create_randomize_layout_seed = \
+  $(CONFIG_SHELL) $(srctree)/$(src)/gen-random-seed.sh $@ $(objtree)/include/generated/randomize_layout_hash.h
+$(objtree)/$(obj)/randomize_layout_seed.h: FORCE
+	$(call if_changed,create_randomize_layout_seed)
+targets = randomize_layout_seed.h randomize_layout_hash.h
+
 $(HOSTLIBS)-y := $(foreach p,$(GCC_PLUGIN),$(if $(findstring /,$(p)),,$(p)))
 always := $($(HOSTLIBS)-y)
 
diff --git a/scripts/gcc-plugins/gcc-common.h b/scripts/gcc-plugins/gcc-common.h
index b232ab15624c..6948898b3cdf 100644
--- a/scripts/gcc-plugins/gcc-common.h
+++ b/scripts/gcc-plugins/gcc-common.h
@@ -63,6 +63,13 @@
 #endif
 
 #if BUILDING_GCC_VERSION >= 4006
+/*
+ * The c-family headers were moved into a subdirectory in GCC version
+ * 4.7, but most plugin-building users of GCC 4.6 are using the Debian
+ * or Ubuntu package, which has an out-of-tree patch to move this to the
+ * same location as found in 4.7 and later:
+ * https://sources.debian.net/src/gcc-4.6/4.6.3-14/debian/patches/pr45078.diff/
+ */
 #include "c-family/c-common.h"
 #else
 #include "c-common.h"
@@ -946,4 +953,9 @@ static inline void debug_gimple_stmt(const_gimple s)
 	get_inner_reference(exp, pbitsize, pbitpos, poffset, pmode, punsignedp, preversep, pvolatilep)
 #endif
 
+#if BUILDING_GCC_VERSION < 7000
+#define SET_DECL_ALIGN(decl, align)	DECL_ALIGN(decl) = (align)
+#define SET_DECL_MODE(decl, mode)	DECL_MODE(decl) = (mode)
+#endif
+
 #endif
diff --git a/scripts/gcc-plugins/gen-random-seed.sh b/scripts/gcc-plugins/gen-random-seed.sh
new file mode 100644
index 000000000000..7514850f4815
--- /dev/null
+++ b/scripts/gcc-plugins/gen-random-seed.sh
@@ -0,0 +1,8 @@
+#!/bin/sh
+
+if [ ! -f "$1" ]; then
+	SEED=`od -A n -t x8 -N 32 /dev/urandom | tr -d ' \n'`
+	echo "const char *randstruct_seed = \"$SEED\";" > "$1"
+	HASH=`echo -n "$SEED" | sha256sum | cut -d" " -f1 | tr -d ' \n'`
+	echo "#define RANDSTRUCT_HASHED_SEED \"$HASH\"" > "$2"
+fi
diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
new file mode 100644
index 000000000000..cdaac8c66734
--- /dev/null
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -0,0 +1,1028 @@
+/*
+ * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
+ *                   and 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
+ *
+ * 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 randomize_layout_plugin.so randomize_layout_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 randomize_layout_plugin.so randomize_layout_plugin.c
+ * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
+ */
+
+#include "gcc-common.h"
+#include "randomize_layout_seed.h"
+
+#if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
+#error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
+#endif
+
+#define ORIG_TYPE_NAME(node) \
+	(TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
+
+#define INFORM(loc, msg, ...)	inform(loc, "randstruct: " msg, ##__VA_ARGS__)
+#define MISMATCH(loc, how, ...)	INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)
+
+__visible int plugin_is_GPL_compatible;
+
+static int performance_mode;
+
+static struct plugin_info randomize_layout_plugin_info = {
+	.version	= "201402201816vanilla",
+	.help		= "disable\t\t\tdo not activate plugin\n"
+			  "performance-mode\tenable cacheline-aware layout randomization\n"
+};
+
+struct whitelist_entry {
+	const char *pathname;
+	const char *lhs;
+	const char *rhs;
+};
+
+static const struct whitelist_entry whitelist[] = {
+	/* NIU overloads mapping with page struct */
+	{ "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
+	/* unix_skb_parms via UNIXCB() buffer */
+	{ "net/unix/af_unix.c", "unix_skb_parms", "char" },
+	/* big_key payload.data struct splashing */
+	{ "security/keys/big_key.c", "path", "void *" },
+	/* walk struct security_hook_heads as an array of struct list_head */
+	{ "security/security.c", "list_head", "security_hook_heads" },
+	{ }
+};
+
+/* from old Linux dcache.h */
+static inline unsigned long
+partial_name_hash(unsigned long c, unsigned long prevhash)
+{
+	return (prevhash + (c << 4) + (c >> 4)) * 11;
+}
+static inline unsigned int
+name_hash(const unsigned char *name)
+{
+	unsigned long hash = 0;
+	unsigned int len = strlen((const char *)name);
+	while (len--)
+		hash = partial_name_hash(*name++, hash);
+	return (unsigned int)hash;
+}
+
+static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
+{
+	tree type;
+
+	*no_add_attrs = true;
+	if (TREE_CODE(*node) == FUNCTION_DECL) {
+		error("%qE attribute does not apply to functions (%qF)", name, *node);
+		return NULL_TREE;
+	}
+
+	if (TREE_CODE(*node) == PARM_DECL) {
+		error("%qE attribute does not apply to function parameters (%qD)", name, *node);
+		return NULL_TREE;
+	}
+
+	if (TREE_CODE(*node) == VAR_DECL) {
+		error("%qE attribute does not apply to variables (%qD)", name, *node);
+		return NULL_TREE;
+	}
+
+	if (TYPE_P(*node)) {
+		type = *node;
+	} else {
+		gcc_assert(TREE_CODE(*node) == TYPE_DECL);
+		type = TREE_TYPE(*node);
+	}
+
+	if (TREE_CODE(type) != RECORD_TYPE) {
+		error("%qE attribute used on %qT applies to struct types only", name, type);
+		return NULL_TREE;
+	}
+
+	if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
+		error("%qE attribute is already applied to the type %qT", name, type);
+		return NULL_TREE;
+	}
+
+	*no_add_attrs = false;
+
+	return NULL_TREE;
+}
+
+/* set on complete types that we don't need to inspect further at all */
+static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
+{
+	*no_add_attrs = false;
+	return NULL_TREE;
+}
+
+/*
+ * set on types that we've performed a shuffle on, to prevent re-shuffling
+ * this does not preclude us from inspecting its fields for potential shuffles
+ */
+static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
+{
+	*no_add_attrs = false;
+	return NULL_TREE;
+}
+
+/*
+ * 64bit variant of Bob Jenkins' public domain PRNG
+ * 256 bits of internal state
+ */
+
+typedef unsigned long long u64;
+
+typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
+
+#define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
+static u64 ranval(ranctx *x) {
+	u64 e = x->a - rot(x->b, 7);
+	x->a = x->b ^ rot(x->c, 13);
+	x->b = x->c + rot(x->d, 37);
+	x->c = x->d + e;
+	x->d = e + x->a;
+	return x->d;
+}
+
+static void raninit(ranctx *x, u64 *seed) {
+	int i;
+
+	x->a = seed[0];
+	x->b = seed[1];
+	x->c = seed[2];
+	x->d = seed[3];
+
+	for (i=0; i < 30; ++i)
+		(void)ranval(x);
+}
+
+static u64 shuffle_seed[4];
+
+struct partition_group {
+	tree tree_start;
+	unsigned long start;
+	unsigned long length;
+};
+
+static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
+{
+	unsigned long i;
+	unsigned long accum_size = 0;
+	unsigned long accum_length = 0;
+	unsigned long group_idx = 0;
+
+	gcc_assert(length < INT_MAX);
+
+	memset(size_groups, 0, sizeof(struct partition_group) * length);
+
+	for (i = 0; i < length; i++) {
+		if (size_groups[group_idx].tree_start == NULL_TREE) {
+			size_groups[group_idx].tree_start = fields[i];
+			size_groups[group_idx].start = i;
+			accum_length = 0;
+			accum_size = 0;
+		}
+		accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
+		accum_length++;
+		if (accum_size >= 64) {
+			size_groups[group_idx].length = accum_length;
+			accum_length = 0;
+			group_idx++;
+		}
+	}
+
+	if (size_groups[group_idx].tree_start != NULL_TREE &&
+	    !size_groups[group_idx].length) {
+		size_groups[group_idx].length = accum_length;
+		group_idx++;
+	}
+
+	*num_groups = group_idx;
+}
+
+static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
+{
+	unsigned long i, x;
+	struct partition_group size_group[length];
+	unsigned long num_groups = 0;
+	unsigned long randnum;
+
+	partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
+	for (i = num_groups - 1; i > 0; i--) {
+		struct partition_group tmp;
+		randnum = ranval(prng_state) % (i + 1);
+		tmp = size_group[i];
+		size_group[i] = size_group[randnum];
+		size_group[randnum] = tmp;
+	}
+
+	for (x = 0; x < num_groups; x++) {
+		for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
+			tree tmp;
+			if (DECL_BIT_FIELD_TYPE(newtree[i]))
+				continue;
+			randnum = ranval(prng_state) % (i + 1);
+			// we could handle this case differently if desired
+			if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
+				continue;
+			tmp = newtree[i];
+			newtree[i] = newtree[randnum];
+			newtree[randnum] = tmp;
+		}
+	}
+}
+
+static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
+{
+	unsigned long i, randnum;
+
+	for (i = length - 1; i > 0; i--) {
+		tree tmp;
+		randnum = ranval(prng_state) % (i + 1);
+		tmp = newtree[i];
+		newtree[i] = newtree[randnum];
+		newtree[randnum] = tmp;
+	}
+}
+
+/* modern in-place Fisher-Yates shuffle */
+static void shuffle(const_tree type, tree *newtree, unsigned long length)
+{
+	unsigned long i;
+	u64 seed[4];
+	ranctx prng_state;
+	const unsigned char *structname;
+
+	if (length == 0)
+		return;
+
+	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
+
+	structname = ORIG_TYPE_NAME(type);
+
+#ifdef __DEBUG_PLUGIN
+	fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
+#ifdef __DEBUG_VERBOSE
+	debug_tree((tree)type);
+#endif
+#endif
+
+	for (i = 0; i < 4; i++) {
+		seed[i] = shuffle_seed[i];
+		seed[i] ^= name_hash(structname);
+	}
+
+	raninit(&prng_state, (u64 *)&seed);
+
+	if (performance_mode)
+		performance_shuffle(newtree, length, &prng_state);
+	else
+		full_shuffle(newtree, length, &prng_state);
+}
+
+static bool is_flexible_array(const_tree field)
+{
+	const_tree fieldtype;
+	const_tree typesize;
+	const_tree elemtype;
+	const_tree elemsize;
+
+	fieldtype = TREE_TYPE(field);
+	typesize = TYPE_SIZE(fieldtype);
+
+	if (TREE_CODE(fieldtype) != ARRAY_TYPE)
+		return false;
+
+	elemtype = TREE_TYPE(fieldtype);
+	elemsize = TYPE_SIZE(elemtype);
+
+	/* size of type is represented in bits */
+
+	if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
+	    TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
+		return true;
+
+	if (typesize != NULL_TREE &&
+	    (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
+	     tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
+		return true;
+
+	return false;
+}
+
+static int relayout_struct(tree type)
+{
+	unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
+	unsigned long shuffle_length = num_fields;
+	tree field;
+	tree newtree[num_fields];
+	unsigned long i;
+	tree list;
+	tree variant;
+	tree main_variant;
+	expanded_location xloc;
+	bool has_flexarray = false;
+
+	if (TYPE_FIELDS(type) == NULL_TREE)
+		return 0;
+
+	if (num_fields < 2)
+		return 0;
+
+	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
+
+	gcc_assert(num_fields < INT_MAX);
+
+	if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
+	    lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
+		return 0;
+
+	/* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
+	if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
+	    !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
+		return 0;
+
+	/* throw out any structs in uapi */
+	xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
+
+	if (strstr(xloc.file, "/uapi/"))
+		error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
+
+	for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
+		gcc_assert(TREE_CODE(field) == FIELD_DECL);
+		newtree[i] = field;
+	}
+
+	/*
+	 * enforce that we don't randomize the layout of the last
+	 * element of a struct if it's a 0 or 1-length array
+	 * or a proper flexible array
+	 */
+	if (is_flexible_array(newtree[num_fields - 1])) {
+		has_flexarray = true;
+		shuffle_length--;
+	}
+
+	shuffle(type, (tree *)newtree, shuffle_length);
+
+	/*
+	 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
+	 * as gcc provides no other way to detect such code
+	 */
+	list = make_node(FIELD_DECL);
+	TREE_CHAIN(list) = newtree[0];
+	TREE_TYPE(list) = void_type_node;
+	DECL_SIZE(list) = bitsize_zero_node;
+	DECL_NONADDRESSABLE_P(list) = 1;
+	DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
+	DECL_SIZE_UNIT(list) = size_zero_node;
+	DECL_FIELD_OFFSET(list) = size_zero_node;
+	DECL_CONTEXT(list) = type;
+	// to satisfy the constify plugin
+	TREE_READONLY(list) = 1;
+
+	for (i = 0; i < num_fields - 1; i++)
+		TREE_CHAIN(newtree[i]) = newtree[i+1];
+	TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
+
+	main_variant = TYPE_MAIN_VARIANT(type);
+	for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
+		TYPE_FIELDS(variant) = list;
+		TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
+		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
+		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
+		if (has_flexarray)
+			TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
+	}
+
+	/*
+	 * force a re-layout of the main variant
+	 * the TYPE_SIZE for all variants will be recomputed
+	 * by finalize_type_size()
+	 */
+	TYPE_SIZE(main_variant) = NULL_TREE;
+	layout_type(main_variant);
+	gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
+
+	return 1;
+}
+
+/* from constify plugin */
+static const_tree get_field_type(const_tree field)
+{
+	return strip_array_types(TREE_TYPE(field));
+}
+
+/* from constify plugin */
+static bool is_fptr(const_tree fieldtype)
+{
+	if (TREE_CODE(fieldtype) != POINTER_TYPE)
+		return false;
+
+	return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
+}
+
+/* derived from constify plugin */
+static int is_pure_ops_struct(const_tree node)
+{
+	const_tree field;
+
+	gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
+
+	/* XXX: Do not apply randomization to all-ftpr structs yet. */
+	return 0;
+
+	for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
+		const_tree fieldtype = get_field_type(field);
+		enum tree_code code = TREE_CODE(fieldtype);
+
+		if (node == fieldtype)
+			continue;
+
+		if (!is_fptr(fieldtype))
+			return 0;
+
+		if (code != RECORD_TYPE && code != UNION_TYPE)
+			continue;
+
+		if (!is_pure_ops_struct(fieldtype))
+			return 0;
+	}
+
+	return 1;
+}
+
+static void randomize_type(tree type)
+{
+	tree variant;
+
+	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
+
+	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
+		return;
+
+	if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
+		relayout_struct(type);
+
+	for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
+		TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
+		TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
+	}
+#ifdef __DEBUG_PLUGIN
+	fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
+#ifdef __DEBUG_VERBOSE
+	debug_tree(type);
+#endif
+#endif
+}
+
+static void update_decl_size(tree decl)
+{
+	tree lastval, lastidx, field, init, type, flexsize;
+	unsigned HOST_WIDE_INT len;
+
+	type = TREE_TYPE(decl);
+
+	if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
+		return;
+
+	init = DECL_INITIAL(decl);
+	if (init == NULL_TREE || init == error_mark_node)
+		return;
+
+	if (TREE_CODE(init) != CONSTRUCTOR)
+		return;
+
+	len = CONSTRUCTOR_NELTS(init);
+        if (!len)
+		return;
+
+	lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
+	lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
+
+	for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
+		;
+
+	if (lastidx != field)
+		return;
+
+	if (TREE_CODE(lastval) != STRING_CST) {
+		error("Only string constants are supported as initializers "
+		      "for randomized structures with flexible arrays");
+		return;
+	}
+
+	flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
+		tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
+
+	DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
+
+	return;
+}
+
+
+static void randomize_layout_finish_decl(void *event_data, void *data)
+{
+	tree decl = (tree)event_data;
+	tree type;
+
+	if (decl == NULL_TREE || decl == error_mark_node)
+		return;
+
+	type = TREE_TYPE(decl);
+
+	if (TREE_CODE(decl) != VAR_DECL)
+		return;
+
+	if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
+		return;
+
+	if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
+		return;
+
+	DECL_SIZE(decl) = 0;
+	DECL_SIZE_UNIT(decl) = 0;
+	SET_DECL_ALIGN(decl, 0);
+	SET_DECL_MODE (decl, VOIDmode);
+	SET_DECL_RTL(decl, 0);
+	update_decl_size(decl);
+	layout_decl(decl, 0);
+}
+
+static void finish_type(void *event_data, void *data)
+{
+	tree type = (tree)event_data;
+
+	if (type == NULL_TREE || type == error_mark_node)
+		return;
+
+	if (TREE_CODE(type) != RECORD_TYPE)
+		return;
+
+	if (TYPE_FIELDS(type) == NULL_TREE)
+		return;
+
+	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
+		return;
+
+#ifdef __DEBUG_PLUGIN
+	fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
+#endif
+#ifdef __DEBUG_VERBOSE
+	debug_tree(type);
+#endif
+	randomize_type(type);
+
+	return;
+}
+
+static struct attribute_spec randomize_layout_attr = {
+	.name		= "randomize_layout",
+	// related to args
+	.min_length	= 0,
+	.max_length	= 0,
+	.decl_required	= false,
+	// need type declaration
+	.type_required	= true,
+	.function_type_required = false,
+	.handler		= handle_randomize_layout_attr,
+#if BUILDING_GCC_VERSION >= 4007
+	.affects_type_identity  = true
+#endif
+};
+
+static struct attribute_spec no_randomize_layout_attr = {
+	.name		= "no_randomize_layout",
+	// related to args
+	.min_length	= 0,
+	.max_length	= 0,
+	.decl_required	= false,
+	// need type declaration
+	.type_required	= true,
+	.function_type_required = false,
+	.handler		= handle_randomize_layout_attr,
+#if BUILDING_GCC_VERSION >= 4007
+	.affects_type_identity  = true
+#endif
+};
+
+static struct attribute_spec randomize_considered_attr = {
+	.name		= "randomize_considered",
+	// related to args
+	.min_length	= 0,
+	.max_length	= 0,
+	.decl_required	= false,
+	// need type declaration
+	.type_required	= true,
+	.function_type_required = false,
+	.handler		= handle_randomize_considered_attr,
+#if BUILDING_GCC_VERSION >= 4007
+	.affects_type_identity  = false
+#endif
+};
+
+static struct attribute_spec randomize_performed_attr = {
+	.name		= "randomize_performed",
+	// related to args
+	.min_length	= 0,
+	.max_length	= 0,
+	.decl_required	= false,
+	// need type declaration
+	.type_required	= true,
+	.function_type_required = false,
+	.handler		= handle_randomize_performed_attr,
+#if BUILDING_GCC_VERSION >= 4007
+	.affects_type_identity  = false
+#endif
+};
+
+static void register_attributes(void *event_data, void *data)
+{
+	register_attribute(&randomize_layout_attr);
+	register_attribute(&no_randomize_layout_attr);
+	register_attribute(&randomize_considered_attr);
+	register_attribute(&randomize_performed_attr);
+}
+
+static void check_bad_casts_in_constructor(tree var, tree init)
+{
+	unsigned HOST_WIDE_INT idx;
+	tree field, val;
+	tree field_type, val_type;
+
+	FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
+		if (TREE_CODE(val) == CONSTRUCTOR) {
+			check_bad_casts_in_constructor(var, val);
+			continue;
+		}
+
+		/* pipacs' plugin creates franken-arrays that differ from those produced by
+		   normal code which all have valid 'field' trees. work around this */
+		if (field == NULL_TREE)
+			continue;
+		field_type = TREE_TYPE(field);
+		val_type = TREE_TYPE(val);
+
+		if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
+			continue;
+
+		if (field_type == val_type)
+			continue;
+
+		field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
+		val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
+
+		if (field_type == void_type_node)
+			continue;
+		if (field_type == val_type)
+			continue;
+		if (TREE_CODE(val_type) != RECORD_TYPE)
+			continue;
+
+		if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
+			continue;
+		MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
+	}
+}
+
+/* derived from the constify plugin */
+static void check_global_variables(void *event_data, void *data)
+{
+	struct varpool_node *node;
+	tree init;
+
+	FOR_EACH_VARIABLE(node) {
+		tree var = NODE_DECL(node);
+		init = DECL_INITIAL(var);
+		if (init == NULL_TREE)
+			continue;
+
+		if (TREE_CODE(init) != CONSTRUCTOR)
+			continue;
+
+		check_bad_casts_in_constructor(var, init);
+	}
+}
+
+static bool dominated_by_is_err(const_tree rhs, basic_block bb)
+{
+	basic_block dom;
+	gimple dom_stmt;
+	gimple call_stmt;
+	const_tree dom_lhs;
+	const_tree poss_is_err_cond;
+	const_tree poss_is_err_func;
+	const_tree is_err_arg;
+
+	dom = get_immediate_dominator(CDI_DOMINATORS, bb);
+	if (!dom)
+		return false;
+
+	dom_stmt = last_stmt(dom);
+	if (!dom_stmt)
+		return false;
+
+	if (gimple_code(dom_stmt) != GIMPLE_COND)
+		return false;
+
+	if (gimple_cond_code(dom_stmt) != NE_EXPR)
+		return false;
+
+	if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
+		return false;
+
+	poss_is_err_cond = gimple_cond_lhs(dom_stmt);
+
+	if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
+		return false;
+
+	call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
+
+	if (gimple_code(call_stmt) != GIMPLE_CALL)
+		return false;
+
+	dom_lhs = gimple_get_lhs(call_stmt);
+	poss_is_err_func = gimple_call_fndecl(call_stmt);
+	if (!poss_is_err_func)
+		return false;
+	if (dom_lhs != poss_is_err_cond)
+		return false;
+	if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
+		return false;
+
+	is_err_arg = gimple_call_arg(call_stmt, 0);
+	if (!is_err_arg)
+		return false;
+
+	if (is_err_arg != rhs)
+		return false;
+
+	return true;
+}
+
+static void handle_local_var_initializers(void)
+{
+	tree var;
+	unsigned int i;
+
+	FOR_EACH_LOCAL_DECL(cfun, i, var) {
+		tree init = DECL_INITIAL(var);
+		if (!init)
+			continue;
+		if (TREE_CODE(init) != CONSTRUCTOR)
+			continue;
+		check_bad_casts_in_constructor(var, init);
+	}
+}
+
+static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
+{
+	const char *type_name;
+
+	if (type_tree == NULL_TREE)
+		return false;
+
+	switch (TREE_CODE(type_tree)) {
+	case RECORD_TYPE:
+		type_name = TYPE_NAME_POINTER(type_tree);
+		break;
+	case INTEGER_TYPE:
+		if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
+			type_name = "char";
+		else {
+			INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
+			debug_tree(type_tree);
+			return false;
+		}
+		break;
+	case POINTER_TYPE:
+		if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
+			type_name = "void *";
+			break;
+		} else {
+			INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
+			debug_tree(type_tree);
+			return false;
+		}
+	default:
+		INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
+		debug_tree(type_tree);
+		return false;
+	}
+
+	return strcmp(type_name, wanted_name) == 0;
+}
+
+static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
+{
+	const struct whitelist_entry *entry;
+	expanded_location xloc = expand_location(gimple_location(stmt));
+
+	for (entry = whitelist; entry->pathname; entry++) {
+		if (!strstr(xloc.file, entry->pathname))
+			continue;
+
+		if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * iterate over all statements to find "bad" casts:
+ * those where the address of the start of a structure is cast
+ * to a pointer of a structure of a different type, or a
+ * structure pointer type is cast to a different structure pointer type
+ */
+static unsigned int find_bad_casts_execute(void)
+{
+	basic_block bb;
+
+	handle_local_var_initializers();
+
+	FOR_EACH_BB_FN(bb, cfun) {
+		gimple_stmt_iterator gsi;
+
+		for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
+			gimple stmt;
+			const_tree lhs;
+			const_tree lhs_type;
+			const_tree rhs1;
+			const_tree rhs_type;
+			const_tree ptr_lhs_type;
+			const_tree ptr_rhs_type;
+			const_tree op0;
+			const_tree op0_type;
+			enum tree_code rhs_code;
+
+			stmt = gsi_stmt(gsi);
+
+#ifdef __DEBUG_PLUGIN
+#ifdef __DEBUG_VERBOSE
+			debug_gimple_stmt(stmt);
+			debug_tree(gimple_get_lhs(stmt));
+#endif
+#endif
+
+			if (gimple_code(stmt) != GIMPLE_ASSIGN)
+				continue;
+
+#ifdef __DEBUG_PLUGIN
+#ifdef __DEBUG_VERBOSE
+			debug_tree(gimple_assign_rhs1(stmt));
+#endif
+#endif
+
+
+			rhs_code = gimple_assign_rhs_code(stmt);
+
+			if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
+				continue;
+
+			lhs = gimple_get_lhs(stmt);
+			lhs_type = TREE_TYPE(lhs);
+			rhs1 = gimple_assign_rhs1(stmt);
+			rhs_type = TREE_TYPE(rhs1);
+
+			if (TREE_CODE(rhs_type) != POINTER_TYPE ||
+			    TREE_CODE(lhs_type) != POINTER_TYPE)
+				continue;
+
+			ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
+			ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
+
+			if (ptr_rhs_type == void_type_node)
+				continue;
+
+			if (ptr_lhs_type == void_type_node)
+				continue;
+
+			if (dominated_by_is_err(rhs1, bb))
+				continue;
+
+			if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
+#ifndef __DEBUG_PLUGIN
+				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
+#endif
+				{
+					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
+						MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
+				}
+				continue;
+			}
+
+			if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
+				continue;
+
+			if (rhs_code == ADDR_EXPR) {
+				op0 = TREE_OPERAND(rhs1, 0);
+
+				if (op0 == NULL_TREE)
+					continue;
+
+				if (TREE_CODE(op0) != VAR_DECL)
+					continue;
+
+				op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
+				if (op0_type == ptr_lhs_type)
+					continue;
+
+#ifndef __DEBUG_PLUGIN
+				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
+#endif
+				{
+					if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
+						MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
+				}
+			} else {
+				const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
+				/* skip bogus type casts introduced by container_of */
+				if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 
+				    !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
+					continue;
+#ifndef __DEBUG_PLUGIN
+				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
+#endif
+				{
+					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
+						MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
+				}
+			}
+
+		}
+	}
+	return 0;
+}
+
+#define PASS_NAME find_bad_casts
+#define NO_GATE
+#define TODO_FLAGS_FINISH TODO_dump_func
+#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;
+	int obtained_seed = 0;
+	struct register_pass_info find_bad_casts_pass_info;
+
+	find_bad_casts_pass_info.pass			= make_find_bad_casts_pass();
+	find_bad_casts_pass_info.reference_pass_name	= "ssa";
+	find_bad_casts_pass_info.ref_pass_instance_number	= 1;
+	find_bad_casts_pass_info.pos_op			= PASS_POS_INSERT_AFTER;
+
+	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, "performance-mode")) {
+			performance_mode = 1;
+			continue;
+		}
+		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
+	}
+
+	if (strlen(randstruct_seed) != 64) {
+		error(G_("invalid seed value supplied for %s plugin"), plugin_name);
+		return 1;
+	}
+	obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
+		&shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
+	if (obtained_seed != 4) {
+		error(G_("Invalid seed supplied for %s plugin"), plugin_name);
+		return 1;
+	}
+
+	register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
+	if (enable) {
+		register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
+		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
+		register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
+		register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
+	}
+	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
+
+	return 0;
+}