Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel...
[platform/kernel/linux-starfive.git] / scripts / gcc-plugins / structleak_plugin.c
1 /*
2  * Copyright 2013-2017 by PaX Team <pageexec@freemail.hu>
3  * Licensed under the GPL v2
4  *
5  * Note: the choice of the license means that the compilation process is
6  *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
7  *       but for the kernel it doesn't matter since it doesn't link against
8  *       any of the gcc libraries
9  *
10  * gcc plugin to forcibly initialize certain local variables that could
11  * otherwise leak kernel stack to userland if they aren't properly initialized
12  * by later code
13  *
14  * Homepage: https://pax.grsecurity.net/
15  *
16  * Options:
17  * -fplugin-arg-structleak_plugin-disable
18  * -fplugin-arg-structleak_plugin-verbose
19  * -fplugin-arg-structleak_plugin-byref
20  * -fplugin-arg-structleak_plugin-byref-all
21  *
22  * Usage:
23  * $ # for 4.5/4.6/C based 4.7
24  * $ 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
25  * $ # for C++ based 4.7/4.8+
26  * $ 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
27  * $ gcc -fplugin=./structleak_plugin.so test.c -O2
28  *
29  * TODO: eliminate redundant initializers
30  */
31
32 #include "gcc-common.h"
33
34 /* unused C type flag in all versions 4.5-6 */
35 #define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE)
36
37 __visible int plugin_is_GPL_compatible;
38
39 static struct plugin_info structleak_plugin_info = {
40         .version        = PLUGIN_VERSION,
41         .help           = "disable\tdo not activate plugin\n"
42                           "byref\tinit structs passed by reference\n"
43                           "byref-all\tinit anything passed by reference\n"
44                           "verbose\tprint all initialized variables\n",
45 };
46
47 #define BYREF_STRUCT    1
48 #define BYREF_ALL       2
49
50 static bool verbose;
51 static int byref;
52
53 static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
54 {
55         *no_add_attrs = true;
56
57         /* check for types? for now accept everything linux has to offer */
58         if (TREE_CODE(*node) != FIELD_DECL)
59                 return NULL_TREE;
60
61         *no_add_attrs = false;
62         return NULL_TREE;
63 }
64
65 static struct attribute_spec user_attr = { };
66
67 static void register_attributes(void *event_data, void *data)
68 {
69         user_attr.name                  = "user";
70         user_attr.handler               = handle_user_attribute;
71         user_attr.affects_type_identity = true;
72
73         register_attribute(&user_attr);
74 }
75
76 static tree get_field_type(tree field)
77 {
78         return strip_array_types(TREE_TYPE(field));
79 }
80
81 static bool is_userspace_type(tree type)
82 {
83         tree field;
84
85         for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) {
86                 tree fieldtype = get_field_type(field);
87                 enum tree_code code = TREE_CODE(fieldtype);
88
89                 if (code == RECORD_TYPE || code == UNION_TYPE)
90                         if (is_userspace_type(fieldtype))
91                                 return true;
92
93                 if (lookup_attribute("user", DECL_ATTRIBUTES(field)))
94                         return true;
95         }
96         return false;
97 }
98
99 static void finish_type(void *event_data, void *data)
100 {
101         tree type = (tree)event_data;
102
103         if (type == NULL_TREE || type == error_mark_node)
104                 return;
105
106         if (TREE_CODE(type) == ENUMERAL_TYPE)
107                 return;
108
109         if (TYPE_USERSPACE(type))
110                 return;
111
112         if (is_userspace_type(type))
113                 TYPE_USERSPACE(type) = 1;
114 }
115
116 static void initialize(tree var)
117 {
118         basic_block bb;
119         gimple_stmt_iterator gsi;
120         tree initializer;
121         gimple init_stmt;
122         tree type;
123
124         /* this is the original entry bb before the forced split */
125         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
126
127         /* first check if variable is already initialized, warn otherwise */
128         for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
129                 gimple stmt = gsi_stmt(gsi);
130                 tree rhs1;
131
132                 /* we're looking for an assignment of a single rhs... */
133                 if (!gimple_assign_single_p(stmt))
134                         continue;
135                 rhs1 = gimple_assign_rhs1(stmt);
136                 /* ... of a non-clobbering expression... */
137                 if (TREE_CLOBBER_P(rhs1))
138                         continue;
139                 /* ... to our variable... */
140                 if (gimple_get_lhs(stmt) != var)
141                         continue;
142                 /* if it's an initializer then we're good */
143                 if (TREE_CODE(rhs1) == CONSTRUCTOR)
144                         return;
145         }
146
147         /* these aren't the 0days you're looking for */
148         if (verbose)
149                 inform(DECL_SOURCE_LOCATION(var),
150                         "%s variable will be forcibly initialized",
151                         (byref && TREE_ADDRESSABLE(var)) ? "byref"
152                                                          : "userspace");
153
154         /* build the initializer expression */
155         type = TREE_TYPE(var);
156         if (AGGREGATE_TYPE_P(type))
157                 initializer = build_constructor(type, NULL);
158         else
159                 initializer = fold_convert(type, integer_zero_node);
160
161         /* build the initializer stmt */
162         init_stmt = gimple_build_assign(var, initializer);
163         gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
164         gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
165         update_stmt(init_stmt);
166 }
167
168 static unsigned int structleak_execute(void)
169 {
170         basic_block bb;
171         tree var;
172         unsigned int i;
173
174         /* split the first bb where we can put the forced initializers */
175         gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
176         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
177         if (!single_pred_p(bb)) {
178                 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
179                 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
180         }
181
182         /* enumerate all local variables and forcibly initialize our targets */
183         FOR_EACH_LOCAL_DECL(cfun, i, var) {
184                 tree type = TREE_TYPE(var);
185
186                 gcc_assert(DECL_P(var));
187                 if (!auto_var_in_fn_p(var, current_function_decl))
188                         continue;
189
190                 /* only care about structure types unless byref-all */
191                 if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
192                         continue;
193
194                 /* if the type is of interest, examine the variable */
195                 if (TYPE_USERSPACE(type) ||
196                     (byref && TREE_ADDRESSABLE(var)))
197                         initialize(var);
198         }
199
200         return 0;
201 }
202
203 #define PASS_NAME structleak
204 #define NO_GATE
205 #define PROPERTIES_REQUIRED PROP_cfg
206 #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
207 #include "gcc-generate-gimple-pass.h"
208
209 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
210 {
211         int i;
212         const char * const plugin_name = plugin_info->base_name;
213         const int argc = plugin_info->argc;
214         const struct plugin_argument * const argv = plugin_info->argv;
215         bool enable = true;
216
217         PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
218
219         if (!plugin_default_version_check(version, &gcc_version)) {
220                 error(G_("incompatible gcc/plugin versions"));
221                 return 1;
222         }
223
224         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
225                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
226                 enable = false;
227         }
228
229         for (i = 0; i < argc; ++i) {
230                 if (!strcmp(argv[i].key, "disable")) {
231                         enable = false;
232                         continue;
233                 }
234                 if (!strcmp(argv[i].key, "verbose")) {
235                         verbose = true;
236                         continue;
237                 }
238                 if (!strcmp(argv[i].key, "byref")) {
239                         byref = BYREF_STRUCT;
240                         continue;
241                 }
242                 if (!strcmp(argv[i].key, "byref-all")) {
243                         byref = BYREF_ALL;
244                         continue;
245                 }
246                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
247         }
248
249         register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
250         if (enable) {
251                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
252                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
253         }
254         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
255
256         return 0;
257 }