diff options
Diffstat (limited to 'scripts')
| -rw-r--r-- | scripts/Makefile.gcc-plugins | 9 | ||||
| -rw-r--r-- | scripts/gcc-plugins/latent_entropy_plugin.c | 640 |
2 files changed, 648 insertions, 1 deletions
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 61f0e6db909b..060d2cb373db 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -6,6 +6,12 @@ ifdef CONFIG_GCC_PLUGINS gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) += cyc_complexity_plugin.so + gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += latent_entropy_plugin.so + gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += -DLATENT_ENTROPY_PLUGIN + ifdef CONFIG_PAX_LATENT_ENTROPY + DISABLE_LATENT_ENTROPY_PLUGIN += -fplugin-arg-latent_entropy_plugin-disable + endif + ifdef CONFIG_GCC_PLUGIN_SANCOV ifeq ($(CFLAGS_KCOV),) # It is needed because of the gcc-plugin.sh and gcc version checks. @@ -21,7 +27,8 @@ ifdef CONFIG_GCC_PLUGINS GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) - export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR SANCOV_PLUGIN + export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR + export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN ifneq ($(PLUGINCC),) # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication. diff --git a/scripts/gcc-plugins/latent_entropy_plugin.c b/scripts/gcc-plugins/latent_entropy_plugin.c new file mode 100644 index 000000000000..ff1939b804ae --- /dev/null +++ b/scripts/gcc-plugins/latent_entropy_plugin.c @@ -0,0 +1,640 @@ +/* + * 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" + +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; + + /* 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(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; +} |