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dfd402a4 ME |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | ||
3 | #ifndef _LINUX_KCSAN_CHECKS_H | |
4 | #define _LINUX_KCSAN_CHECKS_H | |
5 | ||
757a4cef ME |
6 | /* Note: Only include what is already included by compiler.h. */ |
7 | #include <linux/compiler_attributes.h> | |
dfd402a4 ME |
8 | #include <linux/types.h> |
9 | ||
10 | /* | |
d591ec3d ME |
11 | * ACCESS TYPE MODIFIERS |
12 | * | |
13 | * <none>: normal read access; | |
14 | * WRITE : write access; | |
15 | * ATOMIC: access is atomic; | |
16 | * ASSERT: access is not a regular access, but an assertion; | |
757a4cef | 17 | * SCOPED: access is a scoped access; |
dfd402a4 | 18 | */ |
5cbaefe9 | 19 | #define KCSAN_ACCESS_WRITE 0x1 |
dfd402a4 | 20 | #define KCSAN_ACCESS_ATOMIC 0x2 |
d591ec3d | 21 | #define KCSAN_ACCESS_ASSERT 0x4 |
757a4cef | 22 | #define KCSAN_ACCESS_SCOPED 0x8 |
dfd402a4 ME |
23 | |
24 | /* | |
5cbaefe9 | 25 | * __kcsan_*: Always calls into the runtime when KCSAN is enabled. This may be used |
dfd402a4 | 26 | * even in compilation units that selectively disable KCSAN, but must use KCSAN |
5cbaefe9 | 27 | * to validate access to an address. Never use these in header files! |
dfd402a4 ME |
28 | */ |
29 | #ifdef CONFIG_KCSAN | |
30 | /** | |
d591ec3d | 31 | * __kcsan_check_access - check generic access for races |
dfd402a4 | 32 | * |
1443b8c9 ME |
33 | * @ptr: address of access |
34 | * @size: size of access | |
35 | * @type: access type modifier | |
dfd402a4 ME |
36 | */ |
37 | void __kcsan_check_access(const volatile void *ptr, size_t size, int type); | |
38 | ||
01b4ff58 ME |
39 | /** |
40 | * kcsan_disable_current - disable KCSAN for the current context | |
41 | * | |
42 | * Supports nesting. | |
43 | */ | |
44 | void kcsan_disable_current(void); | |
45 | ||
46 | /** | |
47 | * kcsan_enable_current - re-enable KCSAN for the current context | |
48 | * | |
49 | * Supports nesting. | |
50 | */ | |
51 | void kcsan_enable_current(void); | |
19acd03d | 52 | void kcsan_enable_current_nowarn(void); /* Safe in uaccess regions. */ |
01b4ff58 | 53 | |
f0f6928c ME |
54 | /** |
55 | * kcsan_nestable_atomic_begin - begin nestable atomic region | |
56 | * | |
57 | * Accesses within the atomic region may appear to race with other accesses but | |
58 | * should be considered atomic. | |
59 | */ | |
60 | void kcsan_nestable_atomic_begin(void); | |
61 | ||
62 | /** | |
63 | * kcsan_nestable_atomic_end - end nestable atomic region | |
64 | */ | |
65 | void kcsan_nestable_atomic_end(void); | |
66 | ||
67 | /** | |
68 | * kcsan_flat_atomic_begin - begin flat atomic region | |
69 | * | |
70 | * Accesses within the atomic region may appear to race with other accesses but | |
71 | * should be considered atomic. | |
72 | */ | |
73 | void kcsan_flat_atomic_begin(void); | |
74 | ||
75 | /** | |
76 | * kcsan_flat_atomic_end - end flat atomic region | |
77 | */ | |
78 | void kcsan_flat_atomic_end(void); | |
79 | ||
80 | /** | |
81 | * kcsan_atomic_next - consider following accesses as atomic | |
82 | * | |
83 | * Force treating the next n memory accesses for the current context as atomic | |
84 | * operations. | |
85 | * | |
1443b8c9 | 86 | * @n: number of following memory accesses to treat as atomic. |
f0f6928c ME |
87 | */ |
88 | void kcsan_atomic_next(int n); | |
89 | ||
81af89e1 ME |
90 | /** |
91 | * kcsan_set_access_mask - set access mask | |
92 | * | |
93 | * Set the access mask for all accesses for the current context if non-zero. | |
94 | * Only value changes to bits set in the mask will be reported. | |
95 | * | |
1443b8c9 | 96 | * @mask: bitmask |
81af89e1 ME |
97 | */ |
98 | void kcsan_set_access_mask(unsigned long mask); | |
99 | ||
757a4cef ME |
100 | /* Scoped access information. */ |
101 | struct kcsan_scoped_access { | |
102 | struct list_head list; | |
103 | const volatile void *ptr; | |
104 | size_t size; | |
105 | int type; | |
106 | }; | |
107 | /* | |
108 | * Automatically call kcsan_end_scoped_access() when kcsan_scoped_access goes | |
109 | * out of scope; relies on attribute "cleanup", which is supported by all | |
110 | * compilers that support KCSAN. | |
111 | */ | |
112 | #define __kcsan_cleanup_scoped \ | |
113 | __maybe_unused __attribute__((__cleanup__(kcsan_end_scoped_access))) | |
114 | ||
115 | /** | |
116 | * kcsan_begin_scoped_access - begin scoped access | |
117 | * | |
118 | * Begin scoped access and initialize @sa, which will cause KCSAN to | |
119 | * continuously check the memory range in the current thread until | |
120 | * kcsan_end_scoped_access() is called for @sa. | |
121 | * | |
122 | * Scoped accesses are implemented by appending @sa to an internal list for the | |
123 | * current execution context, and then checked on every call into the KCSAN | |
124 | * runtime. | |
125 | * | |
126 | * @ptr: address of access | |
127 | * @size: size of access | |
128 | * @type: access type modifier | |
129 | * @sa: struct kcsan_scoped_access to use for the scope of the access | |
130 | */ | |
131 | struct kcsan_scoped_access * | |
132 | kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type, | |
133 | struct kcsan_scoped_access *sa); | |
134 | ||
135 | /** | |
136 | * kcsan_end_scoped_access - end scoped access | |
137 | * | |
138 | * End a scoped access, which will stop KCSAN checking the memory range. | |
139 | * Requires that kcsan_begin_scoped_access() was previously called once for @sa. | |
140 | * | |
141 | * @sa: a previously initialized struct kcsan_scoped_access | |
142 | */ | |
143 | void kcsan_end_scoped_access(struct kcsan_scoped_access *sa); | |
144 | ||
145 | ||
f0f6928c ME |
146 | #else /* CONFIG_KCSAN */ |
147 | ||
dfd402a4 ME |
148 | static inline void __kcsan_check_access(const volatile void *ptr, size_t size, |
149 | int type) { } | |
f0f6928c | 150 | |
01b4ff58 ME |
151 | static inline void kcsan_disable_current(void) { } |
152 | static inline void kcsan_enable_current(void) { } | |
19acd03d | 153 | static inline void kcsan_enable_current_nowarn(void) { } |
f0f6928c ME |
154 | static inline void kcsan_nestable_atomic_begin(void) { } |
155 | static inline void kcsan_nestable_atomic_end(void) { } | |
156 | static inline void kcsan_flat_atomic_begin(void) { } | |
157 | static inline void kcsan_flat_atomic_end(void) { } | |
158 | static inline void kcsan_atomic_next(int n) { } | |
81af89e1 | 159 | static inline void kcsan_set_access_mask(unsigned long mask) { } |
f0f6928c | 160 | |
757a4cef ME |
161 | struct kcsan_scoped_access { }; |
162 | #define __kcsan_cleanup_scoped __maybe_unused | |
163 | static inline struct kcsan_scoped_access * | |
164 | kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type, | |
165 | struct kcsan_scoped_access *sa) { return sa; } | |
166 | static inline void kcsan_end_scoped_access(struct kcsan_scoped_access *sa) { } | |
167 | ||
f0f6928c | 168 | #endif /* CONFIG_KCSAN */ |
dfd402a4 | 169 | |
19acd03d | 170 | #ifdef __SANITIZE_THREAD__ |
dfd402a4 | 171 | /* |
19acd03d ME |
172 | * Only calls into the runtime when the particular compilation unit has KCSAN |
173 | * instrumentation enabled. May be used in header files. | |
dfd402a4 | 174 | */ |
dfd402a4 | 175 | #define kcsan_check_access __kcsan_check_access |
19acd03d ME |
176 | |
177 | /* | |
178 | * Only use these to disable KCSAN for accesses in the current compilation unit; | |
179 | * calls into libraries may still perform KCSAN checks. | |
180 | */ | |
181 | #define __kcsan_disable_current kcsan_disable_current | |
182 | #define __kcsan_enable_current kcsan_enable_current_nowarn | |
dfd402a4 ME |
183 | #else |
184 | static inline void kcsan_check_access(const volatile void *ptr, size_t size, | |
185 | int type) { } | |
19acd03d ME |
186 | static inline void __kcsan_enable_current(void) { } |
187 | static inline void __kcsan_disable_current(void) { } | |
dfd402a4 ME |
188 | #endif |
189 | ||
190 | /** | |
d591ec3d | 191 | * __kcsan_check_read - check regular read access for races |
dfd402a4 | 192 | * |
1443b8c9 ME |
193 | * @ptr: address of access |
194 | * @size: size of access | |
dfd402a4 ME |
195 | */ |
196 | #define __kcsan_check_read(ptr, size) __kcsan_check_access(ptr, size, 0) | |
197 | ||
198 | /** | |
d591ec3d | 199 | * __kcsan_check_write - check regular write access for races |
dfd402a4 | 200 | * |
1443b8c9 ME |
201 | * @ptr: address of access |
202 | * @size: size of access | |
dfd402a4 ME |
203 | */ |
204 | #define __kcsan_check_write(ptr, size) \ | |
205 | __kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE) | |
206 | ||
207 | /** | |
d591ec3d | 208 | * kcsan_check_read - check regular read access for races |
dfd402a4 | 209 | * |
1443b8c9 ME |
210 | * @ptr: address of access |
211 | * @size: size of access | |
dfd402a4 ME |
212 | */ |
213 | #define kcsan_check_read(ptr, size) kcsan_check_access(ptr, size, 0) | |
214 | ||
215 | /** | |
d591ec3d | 216 | * kcsan_check_write - check regular write access for races |
dfd402a4 | 217 | * |
1443b8c9 ME |
218 | * @ptr: address of access |
219 | * @size: size of access | |
dfd402a4 ME |
220 | */ |
221 | #define kcsan_check_write(ptr, size) \ | |
222 | kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE) | |
223 | ||
224 | /* | |
5cbaefe9 IM |
225 | * Check for atomic accesses: if atomic accesses are not ignored, this simply |
226 | * aliases to kcsan_check_access(), otherwise becomes a no-op. | |
dfd402a4 ME |
227 | */ |
228 | #ifdef CONFIG_KCSAN_IGNORE_ATOMICS | |
5cbaefe9 IM |
229 | #define kcsan_check_atomic_read(...) do { } while (0) |
230 | #define kcsan_check_atomic_write(...) do { } while (0) | |
dfd402a4 ME |
231 | #else |
232 | #define kcsan_check_atomic_read(ptr, size) \ | |
233 | kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC) | |
234 | #define kcsan_check_atomic_write(ptr, size) \ | |
235 | kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC | KCSAN_ACCESS_WRITE) | |
236 | #endif | |
237 | ||
f97f713d | 238 | /** |
703b3215 | 239 | * ASSERT_EXCLUSIVE_WRITER - assert no concurrent writes to @var |
f97f713d | 240 | * |
703b3215 | 241 | * Assert that there are no concurrent writes to @var; other readers are |
f97f713d ME |
242 | * allowed. This assertion can be used to specify properties of concurrent code, |
243 | * where violation cannot be detected as a normal data race. | |
244 | * | |
1443b8c9 ME |
245 | * For example, if we only have a single writer, but multiple concurrent |
246 | * readers, to avoid data races, all these accesses must be marked; even | |
247 | * concurrent marked writes racing with the single writer are bugs. | |
248 | * Unfortunately, due to being marked, they are no longer data races. For cases | |
249 | * like these, we can use the macro as follows: | |
f97f713d | 250 | * |
1443b8c9 ME |
251 | * .. code-block:: c |
252 | * | |
253 | * void writer(void) { | |
254 | * spin_lock(&update_foo_lock); | |
255 | * ASSERT_EXCLUSIVE_WRITER(shared_foo); | |
256 | * WRITE_ONCE(shared_foo, ...); | |
257 | * spin_unlock(&update_foo_lock); | |
258 | * } | |
259 | * void reader(void) { | |
260 | * // update_foo_lock does not need to be held! | |
261 | * ... = READ_ONCE(shared_foo); | |
262 | * } | |
263 | * | |
d8949ef1 ME |
264 | * Note: ASSERT_EXCLUSIVE_WRITER_SCOPED(), if applicable, performs more thorough |
265 | * checking if a clear scope where no concurrent writes are expected exists. | |
266 | * | |
1443b8c9 | 267 | * @var: variable to assert on |
f97f713d ME |
268 | */ |
269 | #define ASSERT_EXCLUSIVE_WRITER(var) \ | |
270 | __kcsan_check_access(&(var), sizeof(var), KCSAN_ACCESS_ASSERT) | |
271 | ||
d8949ef1 ME |
272 | /* |
273 | * Helper macros for implementation of for ASSERT_EXCLUSIVE_*_SCOPED(). @id is | |
274 | * expected to be unique for the scope in which instances of kcsan_scoped_access | |
275 | * are declared. | |
276 | */ | |
277 | #define __kcsan_scoped_name(c, suffix) __kcsan_scoped_##c##suffix | |
278 | #define __ASSERT_EXCLUSIVE_SCOPED(var, type, id) \ | |
279 | struct kcsan_scoped_access __kcsan_scoped_name(id, _) \ | |
280 | __kcsan_cleanup_scoped; \ | |
281 | struct kcsan_scoped_access *__kcsan_scoped_name(id, _dummy_p) \ | |
282 | __maybe_unused = kcsan_begin_scoped_access( \ | |
283 | &(var), sizeof(var), KCSAN_ACCESS_SCOPED | (type), \ | |
284 | &__kcsan_scoped_name(id, _)) | |
285 | ||
286 | /** | |
287 | * ASSERT_EXCLUSIVE_WRITER_SCOPED - assert no concurrent writes to @var in scope | |
288 | * | |
289 | * Scoped variant of ASSERT_EXCLUSIVE_WRITER(). | |
290 | * | |
291 | * Assert that there are no concurrent writes to @var for the duration of the | |
292 | * scope in which it is introduced. This provides a better way to fully cover | |
293 | * the enclosing scope, compared to multiple ASSERT_EXCLUSIVE_WRITER(), and | |
294 | * increases the likelihood for KCSAN to detect racing accesses. | |
295 | * | |
296 | * For example, it allows finding race-condition bugs that only occur due to | |
297 | * state changes within the scope itself: | |
298 | * | |
299 | * .. code-block:: c | |
300 | * | |
301 | * void writer(void) { | |
302 | * spin_lock(&update_foo_lock); | |
303 | * { | |
304 | * ASSERT_EXCLUSIVE_WRITER_SCOPED(shared_foo); | |
305 | * WRITE_ONCE(shared_foo, 42); | |
306 | * ... | |
307 | * // shared_foo should still be 42 here! | |
308 | * } | |
309 | * spin_unlock(&update_foo_lock); | |
310 | * } | |
311 | * void buggy(void) { | |
312 | * if (READ_ONCE(shared_foo) == 42) | |
313 | * WRITE_ONCE(shared_foo, 1); // bug! | |
314 | * } | |
315 | * | |
316 | * @var: variable to assert on | |
317 | */ | |
318 | #define ASSERT_EXCLUSIVE_WRITER_SCOPED(var) \ | |
319 | __ASSERT_EXCLUSIVE_SCOPED(var, KCSAN_ACCESS_ASSERT, __COUNTER__) | |
320 | ||
f97f713d | 321 | /** |
703b3215 | 322 | * ASSERT_EXCLUSIVE_ACCESS - assert no concurrent accesses to @var |
f97f713d | 323 | * |
703b3215 ME |
324 | * Assert that there are no concurrent accesses to @var (no readers nor |
325 | * writers). This assertion can be used to specify properties of concurrent | |
326 | * code, where violation cannot be detected as a normal data race. | |
f97f713d | 327 | * |
1443b8c9 ME |
328 | * For example, where exclusive access is expected after determining no other |
329 | * users of an object are left, but the object is not actually freed. We can | |
330 | * check that this property actually holds as follows: | |
331 | * | |
332 | * .. code-block:: c | |
f97f713d ME |
333 | * |
334 | * if (refcount_dec_and_test(&obj->refcnt)) { | |
335 | * ASSERT_EXCLUSIVE_ACCESS(*obj); | |
1443b8c9 ME |
336 | * do_some_cleanup(obj); |
337 | * release_for_reuse(obj); | |
f97f713d ME |
338 | * } |
339 | * | |
d8949ef1 ME |
340 | * Note: ASSERT_EXCLUSIVE_ACCESS_SCOPED(), if applicable, performs more thorough |
341 | * checking if a clear scope where no concurrent accesses are expected exists. | |
342 | * | |
1443b8c9 ME |
343 | * Note: For cases where the object is freed, `KASAN <kasan.html>`_ is a better |
344 | * fit to detect use-after-free bugs. | |
345 | * | |
346 | * @var: variable to assert on | |
f97f713d ME |
347 | */ |
348 | #define ASSERT_EXCLUSIVE_ACCESS(var) \ | |
349 | __kcsan_check_access(&(var), sizeof(var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT) | |
350 | ||
d8949ef1 ME |
351 | /** |
352 | * ASSERT_EXCLUSIVE_ACCESS_SCOPED - assert no concurrent accesses to @var in scope | |
353 | * | |
354 | * Scoped variant of ASSERT_EXCLUSIVE_ACCESS(). | |
355 | * | |
356 | * Assert that there are no concurrent accesses to @var (no readers nor writers) | |
357 | * for the entire duration of the scope in which it is introduced. This provides | |
358 | * a better way to fully cover the enclosing scope, compared to multiple | |
359 | * ASSERT_EXCLUSIVE_ACCESS(), and increases the likelihood for KCSAN to detect | |
360 | * racing accesses. | |
361 | * | |
362 | * @var: variable to assert on | |
363 | */ | |
364 | #define ASSERT_EXCLUSIVE_ACCESS_SCOPED(var) \ | |
365 | __ASSERT_EXCLUSIVE_SCOPED(var, KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT, __COUNTER__) | |
366 | ||
703b3215 ME |
367 | /** |
368 | * ASSERT_EXCLUSIVE_BITS - assert no concurrent writes to subset of bits in @var | |
369 | * | |
d8949ef1 | 370 | * Bit-granular variant of ASSERT_EXCLUSIVE_WRITER(). |
703b3215 ME |
371 | * |
372 | * Assert that there are no concurrent writes to a subset of bits in @var; | |
373 | * concurrent readers are permitted. This assertion captures more detailed | |
374 | * bit-level properties, compared to the other (word granularity) assertions. | |
375 | * Only the bits set in @mask are checked for concurrent modifications, while | |
1443b8c9 | 376 | * ignoring the remaining bits, i.e. concurrent writes (or reads) to ~mask bits |
703b3215 ME |
377 | * are ignored. |
378 | * | |
379 | * Use this for variables, where some bits must not be modified concurrently, | |
380 | * yet other bits are expected to be modified concurrently. | |
381 | * | |
382 | * For example, variables where, after initialization, some bits are read-only, | |
383 | * but other bits may still be modified concurrently. A reader may wish to | |
384 | * assert that this is true as follows: | |
385 | * | |
1443b8c9 ME |
386 | * .. code-block:: c |
387 | * | |
703b3215 ME |
388 | * ASSERT_EXCLUSIVE_BITS(flags, READ_ONLY_MASK); |
389 | * foo = (READ_ONCE(flags) & READ_ONLY_MASK) >> READ_ONLY_SHIFT; | |
390 | * | |
1443b8c9 ME |
391 | * Note: The access that immediately follows ASSERT_EXCLUSIVE_BITS() is assumed |
392 | * to access the masked bits only, and KCSAN optimistically assumes it is | |
393 | * therefore safe, even in the presence of data races, and marking it with | |
394 | * READ_ONCE() is optional from KCSAN's point-of-view. We caution, however, that | |
395 | * it may still be advisable to do so, since we cannot reason about all compiler | |
396 | * optimizations when it comes to bit manipulations (on the reader and writer | |
397 | * side). If you are sure nothing can go wrong, we can write the above simply | |
398 | * as: | |
399 | * | |
400 | * .. code-block:: c | |
703b3215 ME |
401 | * |
402 | * ASSERT_EXCLUSIVE_BITS(flags, READ_ONLY_MASK); | |
403 | * foo = (flags & READ_ONLY_MASK) >> READ_ONLY_SHIFT; | |
404 | * | |
405 | * Another example, where this may be used, is when certain bits of @var may | |
406 | * only be modified when holding the appropriate lock, but other bits may still | |
407 | * be modified concurrently. Writers, where other bits may change concurrently, | |
408 | * could use the assertion as follows: | |
409 | * | |
1443b8c9 ME |
410 | * .. code-block:: c |
411 | * | |
703b3215 ME |
412 | * spin_lock(&foo_lock); |
413 | * ASSERT_EXCLUSIVE_BITS(flags, FOO_MASK); | |
1443b8c9 | 414 | * old_flags = flags; |
703b3215 ME |
415 | * new_flags = (old_flags & ~FOO_MASK) | (new_foo << FOO_SHIFT); |
416 | * if (cmpxchg(&flags, old_flags, new_flags) != old_flags) { ... } | |
417 | * spin_unlock(&foo_lock); | |
418 | * | |
1443b8c9 ME |
419 | * @var: variable to assert on |
420 | * @mask: only check for modifications to bits set in @mask | |
703b3215 ME |
421 | */ |
422 | #define ASSERT_EXCLUSIVE_BITS(var, mask) \ | |
423 | do { \ | |
424 | kcsan_set_access_mask(mask); \ | |
425 | __kcsan_check_access(&(var), sizeof(var), KCSAN_ACCESS_ASSERT);\ | |
426 | kcsan_set_access_mask(0); \ | |
427 | kcsan_atomic_next(1); \ | |
428 | } while (0) | |
429 | ||
dfd402a4 | 430 | #endif /* _LINUX_KCSAN_CHECKS_H */ |