Merge tag 'gcc-plugins-v4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...
[sfrench/cifs-2.6.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: http://pax.grsecurity.net/
15  *
16  * Options:
17  * -fplugin-arg-structleak_plugin-disable
18  * -fplugin-arg-structleak_plugin-verbose
19  * -fplugin-arg-structleak_plugin-byref-all
20  *
21  * Usage:
22  * $ # for 4.5/4.6/C based 4.7
23  * $ 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
24  * $ # for C++ based 4.7/4.8+
25  * $ 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
26  * $ gcc -fplugin=./structleak_plugin.so test.c -O2
27  *
28  * TODO: eliminate redundant initializers
29  *       increase type coverage
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        = "201607271510vanilla",
41         .help           = "disable\tdo not activate plugin\n"
42                            "verbose\tprint all initialized variables\n",
43 };
44
45 static bool verbose;
46 static bool byref_all;
47
48 static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
49 {
50         *no_add_attrs = true;
51
52         /* check for types? for now accept everything linux has to offer */
53         if (TREE_CODE(*node) != FIELD_DECL)
54                 return NULL_TREE;
55
56         *no_add_attrs = false;
57         return NULL_TREE;
58 }
59
60 static struct attribute_spec user_attr = {
61         .name                   = "user",
62         .min_length             = 0,
63         .max_length             = 0,
64         .decl_required          = false,
65         .type_required          = false,
66         .function_type_required = false,
67         .handler                = handle_user_attribute,
68 #if BUILDING_GCC_VERSION >= 4007
69         .affects_type_identity  = true
70 #endif
71 };
72
73 static void register_attributes(void *event_data, void *data)
74 {
75         register_attribute(&user_attr);
76 }
77
78 static tree get_field_type(tree field)
79 {
80         return strip_array_types(TREE_TYPE(field));
81 }
82
83 static bool is_userspace_type(tree type)
84 {
85         tree field;
86
87         for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) {
88                 tree fieldtype = get_field_type(field);
89                 enum tree_code code = TREE_CODE(fieldtype);
90
91                 if (code == RECORD_TYPE || code == UNION_TYPE)
92                         if (is_userspace_type(fieldtype))
93                                 return true;
94
95                 if (lookup_attribute("user", DECL_ATTRIBUTES(field)))
96                         return true;
97         }
98         return false;
99 }
100
101 static void finish_type(void *event_data, void *data)
102 {
103         tree type = (tree)event_data;
104
105         if (type == NULL_TREE || type == error_mark_node)
106                 return;
107
108 #if BUILDING_GCC_VERSION >= 5000
109         if (TREE_CODE(type) == ENUMERAL_TYPE)
110                 return;
111 #endif
112
113         if (TYPE_USERSPACE(type))
114                 return;
115
116         if (is_userspace_type(type))
117                 TYPE_USERSPACE(type) = 1;
118 }
119
120 static void initialize(tree var)
121 {
122         basic_block bb;
123         gimple_stmt_iterator gsi;
124         tree initializer;
125         gimple init_stmt;
126
127         /* this is the original entry bb before the forced split */
128         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
129
130         /* first check if variable is already initialized, warn otherwise */
131         for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
132                 gimple stmt = gsi_stmt(gsi);
133                 tree rhs1;
134
135                 /* we're looking for an assignment of a single rhs... */
136                 if (!gimple_assign_single_p(stmt))
137                         continue;
138                 rhs1 = gimple_assign_rhs1(stmt);
139 #if BUILDING_GCC_VERSION >= 4007
140                 /* ... of a non-clobbering expression... */
141                 if (TREE_CLOBBER_P(rhs1))
142                         continue;
143 #endif
144                 /* ... to our variable... */
145                 if (gimple_get_lhs(stmt) != var)
146                         continue;
147                 /* if it's an initializer then we're good */
148                 if (TREE_CODE(rhs1) == CONSTRUCTOR)
149                         return;
150         }
151
152         /* these aren't the 0days you're looking for */
153         if (verbose)
154                 inform(DECL_SOURCE_LOCATION(var),
155                         "%s variable will be forcibly initialized",
156                         (byref_all && TREE_ADDRESSABLE(var)) ? "byref"
157                                                              : "userspace");
158
159         /* build the initializer expression */
160         initializer = build_constructor(TREE_TYPE(var), NULL);
161
162         /* build the initializer stmt */
163         init_stmt = gimple_build_assign(var, initializer);
164         gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
165         gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
166         update_stmt(init_stmt);
167 }
168
169 static unsigned int structleak_execute(void)
170 {
171         basic_block bb;
172         unsigned int ret = 0;
173         tree var;
174         unsigned int i;
175
176         /* split the first bb where we can put the forced initializers */
177         gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
178         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
179         if (!single_pred_p(bb)) {
180                 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
181                 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
182         }
183
184         /* enumerate all local variables and forcibly initialize our targets */
185         FOR_EACH_LOCAL_DECL(cfun, i, var) {
186                 tree type = TREE_TYPE(var);
187
188                 gcc_assert(DECL_P(var));
189                 if (!auto_var_in_fn_p(var, current_function_decl))
190                         continue;
191
192                 /* only care about structure types */
193                 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
194                         continue;
195
196                 /* if the type is of interest, examine the variable */
197                 if (TYPE_USERSPACE(type) ||
198                     (byref_all && TREE_ADDRESSABLE(var)))
199                         initialize(var);
200         }
201
202         return ret;
203 }
204
205 #define PASS_NAME structleak
206 #define NO_GATE
207 #define PROPERTIES_REQUIRED PROP_cfg
208 #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
209 #include "gcc-generate-gimple-pass.h"
210
211 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
212 {
213         int i;
214         const char * const plugin_name = plugin_info->base_name;
215         const int argc = plugin_info->argc;
216         const struct plugin_argument * const argv = plugin_info->argv;
217         bool enable = true;
218
219         PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
220
221         if (!plugin_default_version_check(version, &gcc_version)) {
222                 error(G_("incompatible gcc/plugin versions"));
223                 return 1;
224         }
225
226         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
227                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
228                 enable = false;
229         }
230
231         for (i = 0; i < argc; ++i) {
232                 if (!strcmp(argv[i].key, "disable")) {
233                         enable = false;
234                         continue;
235                 }
236                 if (!strcmp(argv[i].key, "verbose")) {
237                         verbose = true;
238                         continue;
239                 }
240                 if (!strcmp(argv[i].key, "byref-all")) {
241                         byref_all = true;
242                         continue;
243                 }
244                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
245         }
246
247         register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
248         if (enable) {
249                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
250                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
251         }
252         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
253
254         return 0;
255 }