diff options
Diffstat (limited to 'kernel/kcsan/core.c')
| -rw-r--r-- | kernel/kcsan/core.c | 43 |
1 files changed, 39 insertions, 4 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 3f89801161d3..589b1e7f0f25 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -39,6 +39,7 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = { .atomic_next = 0, .atomic_nest_count = 0, .in_flat_atomic = false, + .access_mask = 0, }; /* @@ -298,6 +299,15 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr, if (!kcsan_is_enabled()) return; + + /* + * The access_mask check relies on value-change comparison. To avoid + * reporting a race where e.g. the writer set up the watchpoint, but the + * reader has access_mask!=0, we have to ignore the found watchpoint. + */ + if (get_ctx()->access_mask != 0) + return; + /* * Consume the watchpoint as soon as possible, to minimize the chances * of !consumed. Consuming the watchpoint must always be guarded by @@ -341,6 +351,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) u32 _4; u64 _8; } expect_value; + unsigned long access_mask; enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE; unsigned long ua_flags = user_access_save(); unsigned long irq_flags; @@ -435,18 +446,27 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) * Re-read value, and check if it is as expected; if not, we infer a * racy access. */ + access_mask = get_ctx()->access_mask; switch (size) { case 1: expect_value._1 ^= READ_ONCE(*(const u8 *)ptr); + if (access_mask) + expect_value._1 &= (u8)access_mask; break; case 2: expect_value._2 ^= READ_ONCE(*(const u16 *)ptr); + if (access_mask) + expect_value._2 &= (u16)access_mask; break; case 4: expect_value._4 ^= READ_ONCE(*(const u32 *)ptr); + if (access_mask) + expect_value._4 &= (u32)access_mask; break; case 8: expect_value._8 ^= READ_ONCE(*(const u64 *)ptr); + if (access_mask) + expect_value._8 &= (u64)access_mask; break; default: break; /* ignore; we do not diff the values */ @@ -460,11 +480,20 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (!remove_watchpoint(watchpoint)) { /* * Depending on the access type, map a value_change of MAYBE to - * TRUE (require reporting). + * TRUE (always report) or FALSE (never report). */ - if (value_change == KCSAN_VALUE_CHANGE_MAYBE && (size > 8 || is_assert)) { - /* Always assume a value-change. */ - value_change = KCSAN_VALUE_CHANGE_TRUE; + if (value_change == KCSAN_VALUE_CHANGE_MAYBE) { + if (access_mask != 0) { + /* + * For access with access_mask, we require a + * value-change, as it is likely that races on + * ~access_mask bits are expected. + */ + value_change = KCSAN_VALUE_CHANGE_FALSE; + } else if (size > 8 || is_assert) { + /* Always assume a value-change. */ + value_change = KCSAN_VALUE_CHANGE_TRUE; + } } /* @@ -622,6 +651,12 @@ void kcsan_atomic_next(int n) } EXPORT_SYMBOL(kcsan_atomic_next); +void kcsan_set_access_mask(unsigned long mask) +{ + get_ctx()->access_mask = mask; +} +EXPORT_SYMBOL(kcsan_set_access_mask); + void __kcsan_check_access(const volatile void *ptr, size_t size, int type) { check_access(ptr, size, type); |