| /* |
| * 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 = PLUGIN_VERSION, |
| .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; |
| user_attr.affects_type_identity = true; |
| |
| register_attribute(&user_attr); |
| } |
| |
| static tree get_field_type(tree field) |
| { |
| return strip_array_types(TREE_TYPE(field)); |
| } |
| |
| static bool is_userspace_type(tree type) |
| { |
| tree field; |
| |
| for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) { |
| tree fieldtype = get_field_type(field); |
| enum tree_code code = TREE_CODE(fieldtype); |
| |
| if (code == RECORD_TYPE || code == UNION_TYPE) |
| if (is_userspace_type(fieldtype)) |
| return true; |
| |
| if (lookup_attribute("user", DECL_ATTRIBUTES(field))) |
| return true; |
| } |
| return false; |
| } |
| |
| 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) == ENUMERAL_TYPE) |
| return; |
| |
| if (TYPE_USERSPACE(type)) |
| return; |
| |
| if (is_userspace_type(type)) |
| TYPE_USERSPACE(type) = 1; |
| } |
| |
| static void initialize(tree var) |
| { |
| basic_block bb; |
| gimple_stmt_iterator gsi; |
| tree initializer; |
| gimple init_stmt; |
| tree type; |
| |
| /* this is the original entry bb before the forced split */ |
| bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); |
| |
| /* first check if variable is already initialized, warn otherwise */ |
| for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { |
| gimple stmt = gsi_stmt(gsi); |
| tree rhs1; |
| |
| /* we're looking for an assignment of a single rhs... */ |
| if (!gimple_assign_single_p(stmt)) |
| continue; |
| rhs1 = gimple_assign_rhs1(stmt); |
| /* ... of a non-clobbering expression... */ |
| if (TREE_CLOBBER_P(rhs1)) |
| continue; |
| /* ... to our variable... */ |
| if (gimple_get_lhs(stmt) != var) |
| continue; |
| /* if it's an initializer then we're good */ |
| if (TREE_CODE(rhs1) == CONSTRUCTOR) |
| return; |
| } |
| |
| /* these aren't the 0days you're looking for */ |
| if (verbose) |
| inform(DECL_SOURCE_LOCATION(var), |
| "%s variable will be forcibly initialized", |
| (byref && TREE_ADDRESSABLE(var)) ? "byref" |
| : "userspace"); |
| |
| /* build the initializer expression */ |
| type = TREE_TYPE(var); |
| if (AGGREGATE_TYPE_P(type)) |
| initializer = build_constructor(type, NULL); |
| else |
| initializer = fold_convert(type, integer_zero_node); |
| |
| /* build the initializer stmt */ |
| init_stmt = gimple_build_assign(var, initializer); |
| gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
| gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT); |
| update_stmt(init_stmt); |
| } |
| |
| static unsigned int structleak_execute(void) |
| { |
| basic_block bb; |
| tree var; |
| unsigned int i; |
| |
| /* split the first bb where we can put the forced initializers */ |
| 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))); |
| } |
| |
| /* enumerate all local variables and forcibly initialize our targets */ |
| FOR_EACH_LOCAL_DECL(cfun, i, var) { |
| tree type = TREE_TYPE(var); |
| |
| gcc_assert(DECL_P(var)); |
| if (!auto_var_in_fn_p(var, current_function_decl)) |
| continue; |
| |
| /* only care about structure types unless byref-all */ |
| if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) |
| continue; |
| |
| /* if the type is of interest, examine the variable */ |
| if (TYPE_USERSPACE(type) || |
| (byref && TREE_ADDRESSABLE(var))) |
| initialize(var); |
| } |
| |
| return 0; |
| } |
| |
| #define PASS_NAME structleak |
| #define NO_GATE |
| #define PROPERTIES_REQUIRED PROP_cfg |
| #define TODO_FLAGS_FINISH TODO_verify_il | TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func | TODO_remove_unused_locals | TODO_update_ssa | TODO_ggc_collect | TODO_verify_flow |
| #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; |
| |
| PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE); |
| |
| 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, "verbose")) { |
| verbose = true; |
| continue; |
| } |
| if (!strcmp(argv[i].key, "byref")) { |
| byref = BYREF_STRUCT; |
| continue; |
| } |
| if (!strcmp(argv[i].key, "byref-all")) { |
| byref = BYREF_ALL; |
| continue; |
| } |
| error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); |
| } |
| |
| register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info); |
| if (enable) { |
| register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info); |
| register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL); |
| } |
| register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); |
| |
| return 0; |
| } |