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author | 2020-02-25 15:32:58 +0100 | |
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committer | 2020-03-25 09:56:00 -0700 | |
commit | 44656d3dc4f0dc20010d054f27397a4a1469fabf (patch) | |
tree | 3cc0c8938304bb29992524788e001270d1afb4ca /kernel/kcsan/core.c | |
parent | kcsan: Add option for verbose reporting (diff) | |
download | linux-44656d3dc4f0dc20010d054f27397a4a1469fabf.tar.gz linux-44656d3dc4f0dc20010d054f27397a4a1469fabf.tar.bz2 linux-44656d3dc4f0dc20010d054f27397a4a1469fabf.zip |
kcsan: Add current->state to implicitly atomic accesses
Add volatile current->state to list of implicitly atomic accesses. This
is in preparation to eventually enable KCSAN on kernel/sched (which
currently still has KCSAN_SANITIZE := n).
Since accesses that match the special check in atomic.h are rare, it
makes more sense to move this check to the slow-path, avoiding the
additional compare in the fast-path. With the microbenchmark, a speedup
of ~6% is measured.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/kcsan/core.c')
-rw-r--r-- | kernel/kcsan/core.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 065615df88ea..eb30ecdc8c00 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -188,12 +188,13 @@ static __always_inline struct kcsan_ctx *get_ctx(void) return in_task() ? ¤t->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx); } +/* Rules for generic atomic accesses. Called from fast-path. */ static __always_inline bool is_atomic(const volatile void *ptr, size_t size, int type) { struct kcsan_ctx *ctx; - if ((type & KCSAN_ACCESS_ATOMIC) != 0) + if (type & KCSAN_ACCESS_ATOMIC) return true; /* @@ -201,16 +202,16 @@ is_atomic(const volatile void *ptr, size_t size, int type) * as atomic. This allows using them also in atomic regions, such as * seqlocks, without implicitly changing their semantics. */ - if ((type & KCSAN_ACCESS_ASSERT) != 0) + if (type & KCSAN_ACCESS_ASSERT) return false; if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) && - (type & KCSAN_ACCESS_WRITE) != 0 && size <= sizeof(long) && + (type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) && IS_ALIGNED((unsigned long)ptr, size)) return true; /* Assume aligned writes up to word size are atomic. */ ctx = get_ctx(); - if (unlikely(ctx->atomic_next > 0)) { + if (ctx->atomic_next > 0) { /* * Because we do not have separate contexts for nested * interrupts, in case atomic_next is set, we simply assume that @@ -224,10 +225,8 @@ is_atomic(const volatile void *ptr, size_t size, int type) --ctx->atomic_next; /* in task, or outer interrupt */ return true; } - if (unlikely(ctx->atomic_nest_count > 0 || ctx->in_flat_atomic)) - return true; - return kcsan_is_atomic(ptr); + return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic; } static __always_inline bool @@ -367,6 +366,15 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (!kcsan_is_enabled()) goto out; + /* + * Special atomic rules: unlikely to be true, so we check them here in + * the slow-path, and not in the fast-path in is_atomic(). Call after + * kcsan_is_enabled(), as we may access memory that is not yet + * initialized during early boot. + */ + if (!is_assert && kcsan_is_atomic_special(ptr)) + goto out; + if (!check_encodable((unsigned long)ptr, size)) { kcsan_counter_inc(KCSAN_COUNTER_UNENCODABLE_ACCESSES); goto out; |