The KCSAN_ACCESS_ASSERT access type may be used to introduce dummy reads and writes to assert certain properties of concurrent code, where bugs could not be detected as normal data races. For example, a variable that is only meant to be written by a single CPU, but may be read (without locking) by other CPUs must still be marked properly to avoid data races. However, concurrent writes, regardless if WRITE_ONCE() or not, would be a bug. Using kcsan_check_access(&x, sizeof(x), KCSAN_ACCESS_ASSERT) would allow catching such bugs. To support KCSAN_ACCESS_ASSERT the following notable changes were made: * If an access is of type KCSAN_ASSERT_ACCESS, disable various filters that only apply to data races, so that all races that KCSAN observes are reported. * Bug reports that involve an ASSERT access type will be reported as "KCSAN: assert: race in ..." instead of "data-race"; this will help more easily distinguish them. * Update a few comments to just mention 'races' where we do not always mean pure data races.
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| @@ -6,10 +6,16 @@ · 5 unmodified lines | ||
| 6 | 6 | #include <linux/types.h> |
| 7 | 7 | |
| 8 | 8 | /* |
| 9 | − * Access type modifiers. | |
| 9 | + * ACCESS TYPE MODIFIERS | |
| 10 | + * | |
| 11 | + * <none>: normal read access; | |
| 12 | + * WRITE : write access; | |
| 13 | + * ATOMIC: access is atomic; | |
| 14 | + * ASSERT: access is not a regular access, but an assertion; | |
| 10 | 15 | */ |
| 11 | 16 | #define KCSAN_ACCESS_WRITE 0x1 |
| 12 | 17 | #define KCSAN_ACCESS_ATOMIC 0x2 |
| 18 | +#define KCSAN_ACCESS_ASSERT 0x4 | |
| 13 | 19 | |
| 14 | 20 | /* |
| 15 | 21 | * __kcsan_*: Always calls into the runtime when KCSAN is enabled. This may be used |
| @@ -18,7 +24,7 @@ · 2 unmodified lines | ||
| 18 | 24 | */ |
| 19 | 25 | #ifdef CONFIG_KCSAN |
| 20 | 26 | /** |
| 21 | − * __kcsan_check_access - check generic access for data races | |
| 27 | + * __kcsan_check_access - check generic access for races | |
| 22 | 28 | * |
| 23 | 29 | * @ptr address of access |
| 24 | 30 | * @size size of access |
| @@ -43,7 +49,7 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size, · 18 unmodified lines | ||
| 43 | 49 | #endif |
| 44 | 50 | |
| 45 | 51 | /** |
| 46 | − * __kcsan_check_read - check regular read access for data races | |
| 52 | + * __kcsan_check_read - check regular read access for races | |
| 47 | 53 | * |
| 48 | 54 | * @ptr address of access |
| 49 | 55 | * @size size of access |
| @@ -51,7 +57,7 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size, · 1 unmodified line | ||
| 51 | 57 | #define __kcsan_check_read(ptr, size) __kcsan_check_access(ptr, size, 0) |
| 52 | 58 | |
| 53 | 59 | /** |
| 54 | − * __kcsan_check_write - check regular write access for data races | |
| 60 | + * __kcsan_check_write - check regular write access for races | |
| 55 | 61 | * |
| 56 | 62 | * @ptr address of access |
| 57 | 63 | * @size size of access |
| @@ -60,7 +66,7 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size, · 2 unmodified lines | ||
| 60 | 66 | __kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE) |
| 61 | 67 | |
| 62 | 68 | /** |
| 63 | − * kcsan_check_read - check regular read access for data races | |
| 69 | + * kcsan_check_read - check regular read access for races | |
| 64 | 70 | * |
| 65 | 71 | * @ptr address of access |
| 66 | 72 | * @size size of access |
| @@ -68,7 +74,7 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size, · 1 unmodified line | ||
| 68 | 74 | #define kcsan_check_read(ptr, size) kcsan_check_access(ptr, size, 0) |
| 69 | 75 | |
| 70 | 76 | /** |
| 71 | − * kcsan_check_write - check regular write access for data races | |
| 77 | + * kcsan_check_write - check regular write access for races | |
| 72 | 78 | * |
| 73 | 79 | * @ptr address of access |
| 74 | 80 | * @size size of access |