--- /dev/null
+/*
+ * 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[])
+ * {
+ * printf("%u %s\n", argc, *argv);
+ * }
+ *
+ * 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.
+ * local_entropy += 4623067384293424948;
+ *
+ * printf("%u %s\n", argc, *argv);
+ *
+ * // latent_entropy_execute() 4.
+ * tmp_latent_entropy = rol(tmp_latent_entropy, local_entropy);
+ * latent_entropy = tmp_latent_entropy;
+ * }
+ *
+ * It would look like this in C:
+ *
+ * unsigned long local_entropy = latent_entropy;
+ * local_entropy ^= 1234567890;
+ * local_entropy ^= (unsigned long)__builtin_frame_address(0);
+ * local_entropy += 9876543210;
+ * latent_entropy = rol(local_entropy, 1234509876);
+ *
+ * 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"
+
+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 seed;
+/*
+ * get_random_seed() (this is a GCC function) generates the seed.
+ * This is a simple random generator without any cryptographic security because
+ * the entropy doesn't come from here.
+ */
+static unsigned HOST_WIDE_INT get_random_const(void)
+{
+ unsigned int i;
+ unsigned HOST_WIDE_INT ret = 0;
+
+ for (i = 0; i < 8 * sizeof(ret); i++) {
+ ret = (ret << 1) | (seed & 1);
+ seed >>= 1;
+ if (ret & 1)
+ seed ^= 0xD800000000000000ULL;
+ }
+
+ return ret;
+}
+
+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 = {
+ .name = "latent_entropy",
+ .min_length = 0,
+ .max_length = 0,
+ .decl_required = true,
+ .type_required = false,
+ .function_type_required = false,
+ .handler = handle_latent_entropy_attribute,
+#if BUILDING_GCC_VERSION >= 4007
+ .affects_type_identity = false
+#endif
+};
+
+static void register_attributes(void *event_data __unused, void *data __unused)
+{
+ 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 wide int for the rotation
+ */
+ random_const &= HOST_BITS_PER_WIDE_INT - 1;
+ break;
+ }
+
+ case LROTATE_EXPR:
+ default:
+ op = BIT_XOR_EXPR;
+ break;
+ }
+ if (rhs)
+ *rhs = build_int_cstu(unsigned_intDI_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(unsigned_intDI_type_node, "tmp_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(unsigned_intDI_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(unsigned_intDI_type_node, "tmp_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(unsigned_intDI_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;
+
+ /* 2. initialize local entropy variable */
+ 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(unsigned_intDI_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;
+
+ seed = get_random_seed(false);
+
+ if (in_lto_p)
+ return;
+
+ /* extern volatile u64 latent_entropy */
+ gcc_assert(TYPE_PRECISION(long_long_unsigned_type_node) == 64);
+ quals = TYPE_QUALS(long_long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
+ type = build_qualified_type(long_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"
+
+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;
+
+ struct register_pass_info latent_entropy_pass_info;
+
+ latent_entropy_pass_info.pass = make_latent_entropy_pass();
+ latent_entropy_pass_info.reference_pass_name = "optimized";
+ latent_entropy_pass_info.ref_pass_instance_number = 1;
+ latent_entropy_pass_info.pos_op = PASS_POS_INSERT_BEFORE;
+ static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
+ {
+ .base = &latent_entropy_decl,
+ .nelt = 1,
+ .stride = sizeof(latent_entropy_decl),
+ .cb = >_ggc_mx_tree_node,
+ .pchw = >_pch_nx_tree_node
+ },
+ LAST_GGC_ROOT_TAB
+ };
+
+ 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_("unkown 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 *)>_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;
+}
projects / deliverable / linux.git / commitdiff
