1 files changed, 638 insertions, 0 deletions

diff --git a/scripts/gcc-plugins/latent_entropy_plugin.c b/scripts/gcc-plugins/latent_entropy_plugin.c
new file mode 100644
index 000000000..c84bef1d2
--- /dev/null
+++ b/scripts/gcc-plugins/latent_entropy_plugin.c
@@ -0,0 +1,638 @@
+/*
+ * Copyright 2012-2016 by the PaX Team <pageexec@freemail.hu>
+ * Copyright 2016 by Emese Revfy <re.emese@gmail.com>
+ * 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
+ *
+ * This gcc plugin helps generate a little bit of entropy from program state,
+ * used throughout the uptime of the kernel. Here is an instrumentation example:
+ *
+ * before:
+ * void __latent_entropy test(int argc, char *argv[])
+ * {
+ *	if (argc <= 1)
+ *		printf("%s: no command arguments :(\n", *argv);
+ *	else
+ *		printf("%s: %d command arguments!\n", *argv, args - 1);
+ * }
+ *
+ * after:
+ * void __latent_entropy test(int argc, char *argv[])
+ * {
+ *	// latent_entropy_execute() 1.
+ *	unsigned long local_entropy;
+ *	// init_local_entropy() 1.
+ *	void *local_entropy_frameaddr;
+ *	// init_local_entropy() 3.
+ *	unsigned long tmp_latent_entropy;
+ *
+ *	// init_local_entropy() 2.
+ *	local_entropy_frameaddr = __builtin_frame_address(0);
+ *	local_entropy = (unsigned long) local_entropy_frameaddr;
+ *
+ *	// init_local_entropy() 4.
+ *	tmp_latent_entropy = latent_entropy;
+ *	// init_local_entropy() 5.
+ *	local_entropy ^= tmp_latent_entropy;
+ *
+ *	// latent_entropy_execute() 3.
+ *	if (argc <= 1) {
+ *		// perturb_local_entropy()
+ *		local_entropy += 4623067384293424948;
+ *		printf("%s: no command arguments :(\n", *argv);
+ *		// perturb_local_entropy()
+ *	} else {
+ *		local_entropy ^= 3896280633962944730;
+ *		printf("%s: %d command arguments!\n", *argv, args - 1);
+ *	}
+ *
+ *	// latent_entropy_execute() 4.
+ *	tmp_latent_entropy = rol(tmp_latent_entropy, local_entropy);
+ *	latent_entropy = tmp_latent_entropy;
+ * }
+ *
+ * TODO:
+ * - add ipa pass to identify not explicitly marked candidate functions
+ * - mix in more program state (function arguments/return values,
+ *   loop variables, etc)
+ * - more instrumentation control via attribute parameters
+ *
+ * BUGS:
+ * - none known
+ *
+ * Options:
+ * -fplugin-arg-latent_entropy_plugin-disable
+ *
+ * Attribute: __attribute__((latent_entropy))
+ *  The latent_entropy gcc attribute can be only on functions and variables.
+ *  If it is on a function then the plugin will instrument it. If the attribute
+ *  is on a variable then the plugin will initialize it with a random value.
+ *  The variable must be an integer, an integer array type or a structure
+ *  with integer fields.
+ */
+
+#include "gcc-common.h"
+
+__visible int plugin_is_GPL_compatible;
+
+static GTY(()) tree latent_entropy_decl;
+
+static struct plugin_info latent_entropy_plugin_info = {
+	.version	= "201606141920vanilla",
+	.help		= "disable\tturn off latent entropy instrumentation\n",
+};
+
+static unsigned HOST_WIDE_INT deterministic_seed;
+static unsigned HOST_WIDE_INT rnd_buf[32];
+static size_t rnd_idx = ARRAY_SIZE(rnd_buf);
+static int urandom_fd = -1;
+
+static unsigned HOST_WIDE_INT get_random_const(void)
+{
+	if (deterministic_seed) {
+		unsigned HOST_WIDE_INT w = deterministic_seed;
+		w ^= w << 13;
+		w ^= w >> 7;
+		w ^= w << 17;
+		deterministic_seed = w;
+		return deterministic_seed;
+	}
+
+	if (urandom_fd < 0) {
+		urandom_fd = open("/dev/urandom", O_RDONLY);
+		gcc_assert(urandom_fd >= 0);
+	}
+	if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {
+		gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));
+		rnd_idx = 0;
+	}
+	return rnd_buf[rnd_idx++];
+}
+
+static tree tree_get_random_const(tree type)
+{
+	unsigned long long mask;
+
+	mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(type)) - 1);
+	mask = 2 * (mask - 1) + 1;
+
+	if (TYPE_UNSIGNED(type))
+		return build_int_cstu(type, mask & get_random_const());
+	return build_int_cst(type, mask & get_random_const());
+}
+
+static tree handle_latent_entropy_attribute(tree *node, tree name,
+						tree args __unused,
+						int flags __unused,
+						bool *no_add_attrs)
+{
+	tree type;
+#if BUILDING_GCC_VERSION <= 4007
+	VEC(constructor_elt, gc) *vals;
+#else
+	vec<constructor_elt, va_gc> *vals;
+#endif
+
+	switch (TREE_CODE(*node)) {
+	default:
+		*no_add_attrs = true;
+		error("%qE attribute only applies to functions and variables",
+			name);
+		break;
+
+	case VAR_DECL:
+		if (DECL_INITIAL(*node)) {
+			*no_add_attrs = true;
+			error("variable %qD with %qE attribute must not be initialized",
+				*node, name);
+			break;
+		}
+
+		if (!TREE_STATIC(*node)) {
+			*no_add_attrs = true;
+			error("variable %qD with %qE attribute must not be local",
+				*node, name);
+			break;
+		}
+
+		type = TREE_TYPE(*node);
+		switch (TREE_CODE(type)) {
+		default:
+			*no_add_attrs = true;
+			error("variable %qD with %qE attribute must be an integer or a fixed length integer array type or a fixed sized structure with integer fields",
+				*node, name);
+			break;
+
+		case RECORD_TYPE: {
+			tree fld, lst = TYPE_FIELDS(type);
+			unsigned int nelt = 0;
+
+			for (fld = lst; fld; nelt++, fld = TREE_CHAIN(fld)) {
+				tree fieldtype;
+
+				fieldtype = TREE_TYPE(fld);
+				if (TREE_CODE(fieldtype) == INTEGER_TYPE)
+					continue;
+
+				*no_add_attrs = true;
+				error("structure variable %qD with %qE attribute has a non-integer field %qE",
+					*node, name, fld);
+				break;
+			}
+
+			if (fld)
+				break;
+
+#if BUILDING_GCC_VERSION <= 4007
+			vals = VEC_alloc(constructor_elt, gc, nelt);
+#else
+			vec_alloc(vals, nelt);
+#endif
+
+			for (fld = lst; fld; fld = TREE_CHAIN(fld)) {
+				tree random_const, fld_t = TREE_TYPE(fld);
+
+				random_const = tree_get_random_const(fld_t);
+				CONSTRUCTOR_APPEND_ELT(vals, fld, random_const);
+			}
+
+			/* Initialize the fields with random constants */
+			DECL_INITIAL(*node) = build_constructor(type, vals);
+			break;
+		}
+
+		/* Initialize the variable with a random constant */
+		case INTEGER_TYPE:
+			DECL_INITIAL(*node) = tree_get_random_const(type);
+			break;
+
+		case ARRAY_TYPE: {
+			tree elt_type, array_size, elt_size;
+			unsigned int i, nelt;
+			HOST_WIDE_INT array_size_int, elt_size_int;
+
+			elt_type = TREE_TYPE(type);
+			elt_size = TYPE_SIZE_UNIT(TREE_TYPE(type));
+			array_size = TYPE_SIZE_UNIT(type);
+
+			if (TREE_CODE(elt_type) != INTEGER_TYPE || !array_size
+				|| TREE_CODE(array_size) != INTEGER_CST) {
+				*no_add_attrs = true;
+				error("array variable %qD with %qE attribute must be a fixed length integer array type",
+					*node, name);
+				break;
+			}
+
+			array_size_int = TREE_INT_CST_LOW(array_size);
+			elt_size_int = TREE_INT_CST_LOW(elt_size);
+			nelt = array_size_int / elt_size_int;
+
+#if BUILDING_GCC_VERSION <= 4007
+			vals = VEC_alloc(constructor_elt, gc, nelt);
+#else
+			vec_alloc(vals, nelt);
+#endif
+
+			for (i = 0; i < nelt; i++) {
+				tree cst = size_int(i);
+				tree rand_cst = tree_get_random_const(elt_type);
+
+				CONSTRUCTOR_APPEND_ELT(vals, cst, rand_cst);
+			}
+
+			/*
+			 * Initialize the elements of the array with random
+			 * constants
+			 */
+			DECL_INITIAL(*node) = build_constructor(type, vals);
+			break;
+		}
+		}
+		break;
+
+	case FUNCTION_DECL:
+		break;
+	}
+
+	return NULL_TREE;
+}
+
+static struct attribute_spec latent_entropy_attr = { };
+
+static void register_attributes(void *event_data __unused, void *data __unused)
+{
+	latent_entropy_attr.name		= "latent_entropy";
+	latent_entropy_attr.decl_required	= true;
+	latent_entropy_attr.handler		= handle_latent_entropy_attribute;
+
+	register_attribute(&latent_entropy_attr);
+}
+
+static bool latent_entropy_gate(void)
+{
+	tree list;
+
+	/* don't bother with noreturn functions for now */
+	if (TREE_THIS_VOLATILE(current_function_decl))
+		return false;
+
+	/* gcc-4.5 doesn't discover some trivial noreturn functions */
+	if (EDGE_COUNT(EXIT_BLOCK_PTR_FOR_FN(cfun)->preds) == 0)
+		return false;
+
+	list = DECL_ATTRIBUTES(current_function_decl);
+	return lookup_attribute("latent_entropy", list) != NULL_TREE;
+}
+
+static tree create_var(tree type, const char *name)
+{
+	tree var;
+
+	var = create_tmp_var(type, name);
+	add_referenced_var(var);
+	mark_sym_for_renaming(var);
+	return var;
+}
+
+/*
+ * Set up the next operation and its constant operand to use in the latent
+ * entropy PRNG. When RHS is specified, the request is for perturbing the
+ * local latent entropy variable, otherwise it is for perturbing the global
+ * latent entropy variable where the two operands are already given by the
+ * local and global latent entropy variables themselves.
+ *
+ * The operation is one of add/xor/rol when instrumenting the local entropy
+ * variable and one of add/xor when perturbing the global entropy variable.
+ * Rotation is not used for the latter case because it would transmit less
+ * entropy to the global variable than the other two operations.
+ */
+static enum tree_code get_op(tree *rhs)
+{
+	static enum tree_code op;
+	unsigned HOST_WIDE_INT random_const;
+
+	random_const = get_random_const();
+
+	switch (op) {
+	case BIT_XOR_EXPR:
+		op = PLUS_EXPR;
+		break;
+
+	case PLUS_EXPR:
+		if (rhs) {
+			op = LROTATE_EXPR;
+			/*
+			 * This code limits the value of random_const to
+			 * the size of a long for the rotation
+			 */
+			random_const %= TYPE_PRECISION(long_unsigned_type_node);
+			break;
+		}
+
+	case LROTATE_EXPR:
+	default:
+		op = BIT_XOR_EXPR;
+		break;
+	}
+	if (rhs)
+		*rhs = build_int_cstu(long_unsigned_type_node, random_const);
+	return op;
+}
+
+static gimple create_assign(enum tree_code code, tree lhs, tree op1,
+				tree op2)
+{
+	return gimple_build_assign_with_ops(code, lhs, op1, op2);
+}
+
+static void perturb_local_entropy(basic_block bb, tree local_entropy)
+{
+	gimple_stmt_iterator gsi;
+	gimple assign;
+	tree rhs;
+	enum tree_code op;
+
+	op = get_op(&rhs);
+	assign = create_assign(op, local_entropy, local_entropy, rhs);
+	gsi = gsi_after_labels(bb);
+	gsi_insert_before(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+}
+
+static void __perturb_latent_entropy(gimple_stmt_iterator *gsi,
+					tree local_entropy)
+{
+	gimple assign;
+	tree temp;
+	enum tree_code op;
+
+	/* 1. create temporary copy of latent_entropy */
+	temp = create_var(long_unsigned_type_node, "temp_latent_entropy");
+
+	/* 2. read... */
+	add_referenced_var(latent_entropy_decl);
+	mark_sym_for_renaming(latent_entropy_decl);
+	assign = gimple_build_assign(temp, latent_entropy_decl);
+	gsi_insert_before(gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	/* 3. ...modify... */
+	op = get_op(NULL);
+	assign = create_assign(op, temp, temp, local_entropy);
+	gsi_insert_after(gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	/* 4. ...write latent_entropy */
+	assign = gimple_build_assign(latent_entropy_decl, temp);
+	gsi_insert_after(gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+}
+
+static bool handle_tail_calls(basic_block bb, tree local_entropy)
+{
+	gimple_stmt_iterator gsi;
+
+	for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
+		gcall *call;
+		gimple stmt = gsi_stmt(gsi);
+
+		if (!is_gimple_call(stmt))
+			continue;
+
+		call = as_a_gcall(stmt);
+		if (!gimple_call_tail_p(call))
+			continue;
+
+		__perturb_latent_entropy(&gsi, local_entropy);
+		return true;
+	}
+
+	return false;
+}
+
+static void perturb_latent_entropy(tree local_entropy)
+{
+	edge_iterator ei;
+	edge e, last_bb_e;
+	basic_block last_bb;
+
+	gcc_assert(single_pred_p(EXIT_BLOCK_PTR_FOR_FN(cfun)));
+	last_bb_e = single_pred_edge(EXIT_BLOCK_PTR_FOR_FN(cfun));
+
+	FOR_EACH_EDGE(e, ei, last_bb_e->src->preds) {
+		if (ENTRY_BLOCK_PTR_FOR_FN(cfun) == e->src)
+			continue;
+		if (EXIT_BLOCK_PTR_FOR_FN(cfun) == e->src)
+			continue;
+
+		handle_tail_calls(e->src, local_entropy);
+	}
+
+	last_bb = single_pred(EXIT_BLOCK_PTR_FOR_FN(cfun));
+	if (!handle_tail_calls(last_bb, local_entropy)) {
+		gimple_stmt_iterator gsi = gsi_last_bb(last_bb);
+
+		__perturb_latent_entropy(&gsi, local_entropy);
+	}
+}
+
+static void init_local_entropy(basic_block bb, tree local_entropy)
+{
+	gimple assign, call;
+	tree frame_addr, rand_const, tmp, fndecl, udi_frame_addr;
+	enum tree_code op;
+	unsigned HOST_WIDE_INT rand_cst;
+	gimple_stmt_iterator gsi = gsi_after_labels(bb);
+
+	/* 1. create local_entropy_frameaddr */
+	frame_addr = create_var(ptr_type_node, "local_entropy_frameaddr");
+
+	/* 2. local_entropy_frameaddr = __builtin_frame_address() */
+	fndecl = builtin_decl_implicit(BUILT_IN_FRAME_ADDRESS);
+	call = gimple_build_call(fndecl, 1, integer_zero_node);
+	gimple_call_set_lhs(call, frame_addr);
+	gsi_insert_before(&gsi, call, GSI_NEW_STMT);
+	update_stmt(call);
+
+	udi_frame_addr = fold_convert(long_unsigned_type_node, frame_addr);
+	assign = gimple_build_assign(local_entropy, udi_frame_addr);
+	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	/* 3. create temporary copy of latent_entropy */
+	tmp = create_var(long_unsigned_type_node, "temp_latent_entropy");
+
+	/* 4. read the global entropy variable into local entropy */
+	add_referenced_var(latent_entropy_decl);
+	mark_sym_for_renaming(latent_entropy_decl);
+	assign = gimple_build_assign(tmp, latent_entropy_decl);
+	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	/* 5. mix local_entropy_frameaddr into local entropy */
+	assign = create_assign(BIT_XOR_EXPR, local_entropy, local_entropy, tmp);
+	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+
+	rand_cst = get_random_const();
+	rand_const = build_int_cstu(long_unsigned_type_node, rand_cst);
+	op = get_op(NULL);
+	assign = create_assign(op, local_entropy, local_entropy, rand_const);
+	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
+	update_stmt(assign);
+}
+
+static bool create_latent_entropy_decl(void)
+{
+	varpool_node_ptr node;
+
+	if (latent_entropy_decl != NULL_TREE)
+		return true;
+
+	FOR_EACH_VARIABLE(node) {
+		tree name, var = NODE_DECL(node);
+
+		if (DECL_NAME_LENGTH(var) < sizeof("latent_entropy") - 1)
+			continue;
+
+		name = DECL_NAME(var);
+		if (strcmp(IDENTIFIER_POINTER(name), "latent_entropy"))
+			continue;
+
+		latent_entropy_decl = var;
+		break;
+	}
+
+	return latent_entropy_decl != NULL_TREE;
+}
+
+static unsigned int latent_entropy_execute(void)
+{
+	basic_block bb;
+	tree local_entropy;
+
+	if (!create_latent_entropy_decl())
+		return 0;
+
+	/* prepare for step 2 below */
+	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)));
+		bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
+	}
+
+	/* 1. create the local entropy variable */
+	local_entropy = create_var(long_unsigned_type_node, "local_entropy");
+
+	/* 2. initialize the local entropy variable */
+	init_local_entropy(bb, local_entropy);
+
+	bb = bb->next_bb;
+
+	/*
+	 * 3. instrument each BB with an operation on the
+	 *    local entropy variable
+	 */
+	while (bb != EXIT_BLOCK_PTR_FOR_FN(cfun)) {
+		perturb_local_entropy(bb, local_entropy);
+		bb = bb->next_bb;
+	};
+
+	/* 4. mix local entropy into the global entropy variable */
+	perturb_latent_entropy(local_entropy);
+	return 0;
+}
+
+static void latent_entropy_start_unit(void *gcc_data __unused,
+					void *user_data __unused)
+{
+	tree type, id;
+	int quals;
+
+	if (in_lto_p)
+		return;
+
+	/* extern volatile unsigned long latent_entropy */
+	quals = TYPE_QUALS(long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
+	type = build_qualified_type(long_unsigned_type_node, quals);
+	id = get_identifier("latent_entropy");
+	latent_entropy_decl = build_decl(UNKNOWN_LOCATION, VAR_DECL, id, type);
+
+	TREE_STATIC(latent_entropy_decl) = 1;
+	TREE_PUBLIC(latent_entropy_decl) = 1;
+	TREE_USED(latent_entropy_decl) = 1;
+	DECL_PRESERVE_P(latent_entropy_decl) = 1;
+	TREE_THIS_VOLATILE(latent_entropy_decl) = 1;
+	DECL_EXTERNAL(latent_entropy_decl) = 1;
+	DECL_ARTIFICIAL(latent_entropy_decl) = 1;
+	lang_hooks.decls.pushdecl(latent_entropy_decl);
+}
+
+#define PASS_NAME latent_entropy
+#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
+#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
+	| TODO_update_ssa
+#include "gcc-generate-gimple-pass.h"
+
+__visible int plugin_init(struct plugin_name_args *plugin_info,
+			  struct plugin_gcc_version *version)
+{
+	bool enabled = true;
+	const char * const plugin_name = plugin_info->base_name;
+	const int argc = plugin_info->argc;
+	const struct plugin_argument * const argv = plugin_info->argv;
+	int i;
+
+	/*
+	 * Call get_random_seed() with noinit=true, so that this returns
+	 * 0 in the case where no seed has been passed via -frandom-seed.
+	 */
+	deterministic_seed = get_random_seed(true);
+
+	static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
+		{
+			.base = &latent_entropy_decl,
+			.nelt = 1,
+			.stride = sizeof(latent_entropy_decl),
+			.cb = &gt_ggc_mx_tree_node,
+			.pchw = &gt_pch_nx_tree_node
+		},
+		LAST_GGC_ROOT_TAB
+	};
+
+	PASS_INFO(latent_entropy, "optimized", 1, PASS_POS_INSERT_BEFORE);
+
+	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;
+		}
+		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
+	}
+
+	register_callback(plugin_name, PLUGIN_INFO, NULL,
+				&latent_entropy_plugin_info);
+	if (enabled) {
+		register_callback(plugin_name, PLUGIN_START_UNIT,
+					&latent_entropy_start_unit, NULL);
+		register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS,
+				  NULL, (void *)&gt_ggc_r_gt_latent_entropy);
+		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
+					&latent_entropy_pass_info);
+	}
+	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes,
+				NULL);
+
+	return 0;
+}