Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu
[sfrench/cifs-2.6.git] / lib / test_stackinit.c
1 // SPDX-Licenses: GPLv2
2 /*
3  * Test cases for compiler-based stack variable zeroing via future
4  * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
5  */
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8 #include <linux/init.h>
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/string.h>
12
13 /* Exfiltration buffer. */
14 #define MAX_VAR_SIZE    128
15 static char check_buf[MAX_VAR_SIZE];
16
17 /* Character array to trigger stack protector in all functions. */
18 #define VAR_BUFFER       32
19
20 /* Volatile mask to convince compiler to copy memory with 0xff. */
21 static volatile u8 forced_mask = 0xff;
22
23 /* Location and size tracking to validate fill and test are colocated. */
24 static void *fill_start, *target_start;
25 static size_t fill_size, target_size;
26
27 static bool range_contains(char *haystack_start, size_t haystack_size,
28                            char *needle_start, size_t needle_size)
29 {
30         if (needle_start >= haystack_start &&
31             needle_start + needle_size <= haystack_start + haystack_size)
32                 return true;
33         return false;
34 }
35
36 #define DO_NOTHING_TYPE_SCALAR(var_type)        var_type
37 #define DO_NOTHING_TYPE_STRING(var_type)        void
38 #define DO_NOTHING_TYPE_STRUCT(var_type)        void
39
40 #define DO_NOTHING_RETURN_SCALAR(ptr)           *(ptr)
41 #define DO_NOTHING_RETURN_STRING(ptr)           /**/
42 #define DO_NOTHING_RETURN_STRUCT(ptr)           /**/
43
44 #define DO_NOTHING_CALL_SCALAR(var, name)                       \
45                 (var) = do_nothing_ ## name(&(var))
46 #define DO_NOTHING_CALL_STRING(var, name)                       \
47                 do_nothing_ ## name(var)
48 #define DO_NOTHING_CALL_STRUCT(var, name)                       \
49                 do_nothing_ ## name(&(var))
50
51 #define FETCH_ARG_SCALAR(var)           &var
52 #define FETCH_ARG_STRING(var)           var
53 #define FETCH_ARG_STRUCT(var)           &var
54
55 #define FILL_SIZE_STRING                16
56
57 #define INIT_CLONE_SCALAR               /**/
58 #define INIT_CLONE_STRING               [FILL_SIZE_STRING]
59 #define INIT_CLONE_STRUCT               /**/
60
61 #define INIT_SCALAR_none                /**/
62 #define INIT_SCALAR_zero                = 0
63
64 #define INIT_STRING_none                [FILL_SIZE_STRING] /**/
65 #define INIT_STRING_zero                [FILL_SIZE_STRING] = { }
66
67 #define INIT_STRUCT_none                /**/
68 #define INIT_STRUCT_zero                = { }
69 #define INIT_STRUCT_static_partial      = { .two = 0, }
70 #define INIT_STRUCT_static_all          = { .one = arg->one,            \
71                                             .two = arg->two,            \
72                                             .three = arg->three,        \
73                                             .four = arg->four,          \
74                                         }
75 #define INIT_STRUCT_dynamic_partial     = { .two = arg->two, }
76 #define INIT_STRUCT_dynamic_all         = { .one = arg->one,            \
77                                             .two = arg->two,            \
78                                             .three = arg->three,        \
79                                             .four = arg->four,          \
80                                         }
81 #define INIT_STRUCT_runtime_partial     ;                               \
82                                         var.two = 0
83 #define INIT_STRUCT_runtime_all         ;                               \
84                                         var.one = 0;                    \
85                                         var.two = 0;                    \
86                                         var.three = 0;                  \
87                                         memset(&var.four, 0,            \
88                                                sizeof(var.four))
89
90 /*
91  * @name: unique string name for the test
92  * @var_type: type to be tested for zeroing initialization
93  * @which: is this a SCALAR, STRING, or STRUCT type?
94  * @init_level: what kind of initialization is performed
95  */
96 #define DEFINE_TEST_DRIVER(name, var_type, which)               \
97 /* Returns 0 on success, 1 on failure. */                       \
98 static noinline __init int test_ ## name (void)                 \
99 {                                                               \
100         var_type zero INIT_CLONE_ ## which;                     \
101         int ignored;                                            \
102         u8 sum = 0, i;                                          \
103                                                                 \
104         /* Notice when a new test is larger than expected. */   \
105         BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);              \
106                                                                 \
107         /* Fill clone type with zero for per-field init. */     \
108         memset(&zero, 0x00, sizeof(zero));                      \
109         /* Fill stack with 0xFF. */                             \
110         ignored = leaf_ ##name((unsigned long)&ignored, 1,      \
111                                 FETCH_ARG_ ## which(zero));     \
112         /* Clear entire check buffer for later bit tests. */    \
113         memset(check_buf, 0x00, sizeof(check_buf));             \
114         /* Extract stack-defined variable contents. */          \
115         ignored = leaf_ ##name((unsigned long)&ignored, 0,      \
116                                 FETCH_ARG_ ## which(zero));     \
117                                                                 \
118         /* Validate that compiler lined up fill and target. */  \
119         if (!range_contains(fill_start, fill_size,              \
120                             target_start, target_size)) {       \
121                 pr_err(#name ": stack fill missed target!?\n"); \
122                 pr_err(#name ": fill %zu wide\n", fill_size);   \
123                 pr_err(#name ": target offset by %d\n", \
124                         (int)((ssize_t)(uintptr_t)fill_start -  \
125                         (ssize_t)(uintptr_t)target_start));     \
126                 return 1;                                       \
127         }                                                       \
128                                                                 \
129         /* Look for any set bits in the check region. */        \
130         for (i = 0; i < sizeof(check_buf); i++)                 \
131                 sum += (check_buf[i] != 0);                     \
132                                                                 \
133         if (sum == 0)                                           \
134                 pr_info(#name " ok\n");                         \
135         else                                                    \
136                 pr_warn(#name " FAIL (uninit bytes: %d)\n",     \
137                         sum);                                   \
138                                                                 \
139         return (sum != 0);                                      \
140 }
141 #define DEFINE_TEST(name, var_type, which, init_level)          \
142 /* no-op to force compiler into ignoring "uninitialized" vars */\
143 static noinline __init DO_NOTHING_TYPE_ ## which(var_type)      \
144 do_nothing_ ## name(var_type *ptr)                              \
145 {                                                               \
146         /* Will always be true, but compiler doesn't know. */   \
147         if ((unsigned long)ptr > 0x2)                           \
148                 return DO_NOTHING_RETURN_ ## which(ptr);        \
149         else                                                    \
150                 return DO_NOTHING_RETURN_ ## which(ptr + 1);    \
151 }                                                               \
152 static noinline __init int leaf_ ## name(unsigned long sp,      \
153                                          bool fill,             \
154                                          var_type *arg)         \
155 {                                                               \
156         char buf[VAR_BUFFER];                                   \
157         var_type var INIT_ ## which ## _ ## init_level;         \
158                                                                 \
159         target_start = &var;                                    \
160         target_size = sizeof(var);                              \
161         /*                                                      \
162          * Keep this buffer around to make sure we've got a     \
163          * stack frame of SOME kind...                          \
164          */                                                     \
165         memset(buf, (char)(sp && 0xff), sizeof(buf));           \
166         /* Fill variable with 0xFF. */                          \
167         if (fill) {                                             \
168                 fill_start = &var;                              \
169                 fill_size = sizeof(var);                        \
170                 memset(fill_start,                              \
171                        (char)((sp && 0xff) | forced_mask),      \
172                        fill_size);                              \
173         }                                                       \
174                                                                 \
175         /* Silence "never initialized" warnings. */             \
176         DO_NOTHING_CALL_ ## which(var, name);                   \
177                                                                 \
178         /* Exfiltrate "var". */                                 \
179         memcpy(check_buf, target_start, target_size);           \
180                                                                 \
181         return (int)buf[0] | (int)buf[sizeof(buf) - 1];         \
182 }                                                               \
183 DEFINE_TEST_DRIVER(name, var_type, which)
184
185 /* Structure with no padding. */
186 struct test_packed {
187         unsigned long one;
188         unsigned long two;
189         unsigned long three;
190         unsigned long four;
191 };
192
193 /* Simple structure with padding likely to be covered by compiler. */
194 struct test_small_hole {
195         size_t one;
196         char two;
197         /* 3 byte padding hole here. */
198         int three;
199         unsigned long four;
200 };
201
202 /* Try to trigger unhandled padding in a structure. */
203 struct test_aligned {
204         u32 internal1;
205         u64 internal2;
206 } __aligned(64);
207
208 struct test_big_hole {
209         u8 one;
210         u8 two;
211         u8 three;
212         /* 61 byte padding hole here. */
213         struct test_aligned four;
214 } __aligned(64);
215
216 struct test_trailing_hole {
217         char *one;
218         char *two;
219         char *three;
220         char four;
221         /* "sizeof(unsigned long) - 1" byte padding hole here. */
222 };
223
224 /* Test if STRUCTLEAK is clearing structs with __user fields. */
225 struct test_user {
226         u8 one;
227         unsigned long two;
228         char __user *three;
229         unsigned long four;
230 };
231
232 #define DEFINE_SCALAR_TEST(name, init)                          \
233                 DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
234
235 #define DEFINE_SCALAR_TESTS(init)                               \
236                 DEFINE_SCALAR_TEST(u8, init);                   \
237                 DEFINE_SCALAR_TEST(u16, init);                  \
238                 DEFINE_SCALAR_TEST(u32, init);                  \
239                 DEFINE_SCALAR_TEST(u64, init);                  \
240                 DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
241
242 #define DEFINE_STRUCT_TEST(name, init)                          \
243                 DEFINE_TEST(name ## _ ## init,                  \
244                             struct test_ ## name, STRUCT, init)
245
246 #define DEFINE_STRUCT_TESTS(init)                               \
247                 DEFINE_STRUCT_TEST(small_hole, init);           \
248                 DEFINE_STRUCT_TEST(big_hole, init);             \
249                 DEFINE_STRUCT_TEST(trailing_hole, init);        \
250                 DEFINE_STRUCT_TEST(packed, init)
251
252 /* These should be fully initialized all the time! */
253 DEFINE_SCALAR_TESTS(zero);
254 DEFINE_STRUCT_TESTS(zero);
255 /* Static initialization: padding may be left uninitialized. */
256 DEFINE_STRUCT_TESTS(static_partial);
257 DEFINE_STRUCT_TESTS(static_all);
258 /* Dynamic initialization: padding may be left uninitialized. */
259 DEFINE_STRUCT_TESTS(dynamic_partial);
260 DEFINE_STRUCT_TESTS(dynamic_all);
261 /* Runtime initialization: padding may be left uninitialized. */
262 DEFINE_STRUCT_TESTS(runtime_partial);
263 DEFINE_STRUCT_TESTS(runtime_all);
264 /* No initialization without compiler instrumentation. */
265 DEFINE_SCALAR_TESTS(none);
266 DEFINE_STRUCT_TESTS(none);
267 DEFINE_TEST(user, struct test_user, STRUCT, none);
268
269 /*
270  * Check two uses through a variable declaration outside either path,
271  * which was noticed as a special case in porting earlier stack init
272  * compiler logic.
273  */
274 static int noinline __leaf_switch_none(int path, bool fill)
275 {
276         switch (path) {
277                 uint64_t var;
278
279         case 1:
280                 target_start = &var;
281                 target_size = sizeof(var);
282                 if (fill) {
283                         fill_start = &var;
284                         fill_size = sizeof(var);
285
286                         memset(fill_start, forced_mask | 0x55, fill_size);
287                 }
288                 memcpy(check_buf, target_start, target_size);
289                 break;
290         case 2:
291                 target_start = &var;
292                 target_size = sizeof(var);
293                 if (fill) {
294                         fill_start = &var;
295                         fill_size = sizeof(var);
296
297                         memset(fill_start, forced_mask | 0xaa, fill_size);
298                 }
299                 memcpy(check_buf, target_start, target_size);
300                 break;
301         default:
302                 var = 5;
303                 return var & forced_mask;
304         }
305         return 0;
306 }
307
308 static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
309                                               uint64_t *arg)
310 {
311         return __leaf_switch_none(1, fill);
312 }
313
314 static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
315                                               uint64_t *arg)
316 {
317         return __leaf_switch_none(2, fill);
318 }
319
320 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);
321 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR);
322
323 static int __init test_stackinit_init(void)
324 {
325         unsigned int failures = 0;
326
327 #define test_scalars(init)      do {                            \
328                 failures += test_u8_ ## init ();                \
329                 failures += test_u16_ ## init ();               \
330                 failures += test_u32_ ## init ();               \
331                 failures += test_u64_ ## init ();               \
332                 failures += test_char_array_ ## init ();        \
333         } while (0)
334
335 #define test_structs(init)      do {                            \
336                 failures += test_small_hole_ ## init ();        \
337                 failures += test_big_hole_ ## init ();          \
338                 failures += test_trailing_hole_ ## init ();     \
339                 failures += test_packed_ ## init ();            \
340         } while (0)
341
342         /* These are explicitly initialized and should always pass. */
343         test_scalars(zero);
344         test_structs(zero);
345         /* Padding here appears to be accidentally always initialized? */
346         test_structs(dynamic_partial);
347         /* Padding initialization depends on compiler behaviors. */
348         test_structs(static_partial);
349         test_structs(static_all);
350         test_structs(dynamic_all);
351         test_structs(runtime_partial);
352         test_structs(runtime_all);
353
354         /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
355         test_scalars(none);
356         failures += test_switch_1_none();
357         failures += test_switch_2_none();
358
359         /* STRUCTLEAK_BYREF should cover from here down. */
360         test_structs(none);
361
362         /* STRUCTLEAK will only cover this. */
363         failures += test_user();
364
365         if (failures == 0)
366                 pr_info("all tests passed!\n");
367         else
368                 pr_err("failures: %u\n", failures);
369
370         return failures ? -EINVAL : 0;
371 }
372 module_init(test_stackinit_init);
373
374 static void __exit test_stackinit_exit(void)
375 { }
376 module_exit(test_stackinit_exit);
377
378 MODULE_LICENSE("GPL");