Merge tag 'pstore-v4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees...
[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  *
20  * Usage:
21  * $ # for 4.5/4.6/C based 4.7
22  * $ 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
23  * $ # for C++ based 4.7/4.8+
24  * $ 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
25  * $ gcc -fplugin=./structleak_plugin.so test.c -O2
26  *
27  * TODO: eliminate redundant initializers
28  *       increase type coverage
29  */
30
31 #include "gcc-common.h"
32
33 /* unused C type flag in all versions 4.5-6 */
34 #define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE)
35
36 __visible int plugin_is_GPL_compatible;
37
38 static struct plugin_info structleak_plugin_info = {
39         .version        = "201607271510vanilla",
40         .help           = "disable\tdo not activate plugin\n"
41                            "verbose\tprint all initialized variables\n",
42 };
43
44 static bool verbose;
45
46 static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
47 {
48         *no_add_attrs = true;
49
50         /* check for types? for now accept everything linux has to offer */
51         if (TREE_CODE(*node) != FIELD_DECL)
52                 return NULL_TREE;
53
54         *no_add_attrs = false;
55         return NULL_TREE;
56 }
57
58 static struct attribute_spec user_attr = {
59         .name                   = "user",
60         .min_length             = 0,
61         .max_length             = 0,
62         .decl_required          = false,
63         .type_required          = false,
64         .function_type_required = false,
65         .handler                = handle_user_attribute,
66 #if BUILDING_GCC_VERSION >= 4007
67         .affects_type_identity  = true
68 #endif
69 };
70
71 static void register_attributes(void *event_data, void *data)
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 BUILDING_GCC_VERSION >= 5000
107         if (TREE_CODE(type) == ENUMERAL_TYPE)
108                 return;
109 #endif
110
111         if (TYPE_USERSPACE(type))
112                 return;
113
114         if (is_userspace_type(type))
115                 TYPE_USERSPACE(type) = 1;
116 }
117
118 static void initialize(tree var)
119 {
120         basic_block bb;
121         gimple_stmt_iterator gsi;
122         tree initializer;
123         gimple init_stmt;
124
125         /* this is the original entry bb before the forced split */
126         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
127
128         /* first check if variable is already initialized, warn otherwise */
129         for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
130                 gimple stmt = gsi_stmt(gsi);
131                 tree rhs1;
132
133                 /* we're looking for an assignment of a single rhs... */
134                 if (!gimple_assign_single_p(stmt))
135                         continue;
136                 rhs1 = gimple_assign_rhs1(stmt);
137 #if BUILDING_GCC_VERSION >= 4007
138                 /* ... of a non-clobbering expression... */
139                 if (TREE_CLOBBER_P(rhs1))
140                         continue;
141 #endif
142                 /* ... to our variable... */
143                 if (gimple_get_lhs(stmt) != var)
144                         continue;
145                 /* if it's an initializer then we're good */
146                 if (TREE_CODE(rhs1) == CONSTRUCTOR)
147                         return;
148         }
149
150         /* these aren't the 0days you're looking for */
151         if (verbose)
152                 inform(DECL_SOURCE_LOCATION(var),
153                         "userspace variable will be forcibly initialized");
154
155         /* build the initializer expression */
156         initializer = build_constructor(TREE_TYPE(var), NULL);
157
158         /* build the initializer stmt */
159         init_stmt = gimple_build_assign(var, initializer);
160         gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
161         gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
162         update_stmt(init_stmt);
163 }
164
165 static unsigned int structleak_execute(void)
166 {
167         basic_block bb;
168         unsigned int ret = 0;
169         tree var;
170         unsigned int i;
171
172         /* split the first bb where we can put the forced initializers */
173         gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
174         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
175         if (!single_pred_p(bb)) {
176                 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
177                 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
178         }
179
180         /* enumerate all local variables and forcibly initialize our targets */
181         FOR_EACH_LOCAL_DECL(cfun, i, var) {
182                 tree type = TREE_TYPE(var);
183
184                 gcc_assert(DECL_P(var));
185                 if (!auto_var_in_fn_p(var, current_function_decl))
186                         continue;
187
188                 /* only care about structure types */
189                 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
190                         continue;
191
192                 /* if the type is of interest, examine the variable */
193                 if (TYPE_USERSPACE(type))
194                         initialize(var);
195         }
196
197         return ret;
198 }
199
200 #define PASS_NAME structleak
201 #define NO_GATE
202 #define PROPERTIES_REQUIRED PROP_cfg
203 #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
204 #include "gcc-generate-gimple-pass.h"
205
206 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
207 {
208         int i;
209         const char * const plugin_name = plugin_info->base_name;
210         const int argc = plugin_info->argc;
211         const struct plugin_argument * const argv = plugin_info->argv;
212         bool enable = true;
213
214         PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
215
216         if (!plugin_default_version_check(version, &gcc_version)) {
217                 error(G_("incompatible gcc/plugin versions"));
218                 return 1;
219         }
220
221         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
222                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
223                 enable = false;
224         }
225
226         for (i = 0; i < argc; ++i) {
227                 if (!strcmp(argv[i].key, "disable")) {
228                         enable = false;
229                         continue;
230                 }
231                 if (!strcmp(argv[i].key, "verbose")) {
232                         verbose = true;
233                         continue;
234                 }
235                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
236         }
237
238         register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
239         if (enable) {
240                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
241                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
242         }
243         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
244
245         return 0;
246 }