kcsan: Improve various small stylistic details

Tidy up a few bits:

  - Fix typos and grammar, improve wording.

  - Remove spurious newlines that are col80 warning artifacts where the
    resulting line-break is worse than the disease it's curing.

  - Use core kernel coding style to improve readability and reduce
    spurious code pattern variations.

  - Use better vertical alignment for structure definitions and initialization
    sequences.

  - Misc other small details.

No change in functionality intended.

Cc: [email protected]
Cc: Marco Elver <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

arch/x86/Kconfig

@@ -226,7 +226,7 @@ config X86
 	select VIRT_TO_BUS
 	select X86_FEATURE_NAMES		if PROC_FS
 	select PROC_PID_ARCH_STATUS		if PROC_FS
-	select HAVE_ARCH_KCSAN if X86_64
+	select HAVE_ARCH_KCSAN			if X86_64
 
 config INSTRUCTION_DECODER
 	def_bool y

include/linux/compiler-clang.h

@@ -16,7 +16,7 @@
 #define KASAN_ABI_VERSION 5
 
 #if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
-/* emulate gcc's __SANITIZE_ADDRESS__ flag */
+/* Emulate GCC's __SANITIZE_ADDRESS__ flag */
 #define __SANITIZE_ADDRESS__
 #define __no_sanitize_address \
 		__attribute__((no_sanitize("address", "hwaddress")))

include/linux/compiler.h

@@ -313,7 +313,7 @@ unsigned long read_word_at_a_time(const void *addr)
 #include <linux/kcsan.h>
 
 /*
- * data_race: macro to document that accesses in an expression may conflict with
+ * data_race(): macro to document that accesses in an expression may conflict with
  * other concurrent accesses resulting in data races, but the resulting
  * behaviour is deemed safe regardless.
  *

include/linux/kcsan-checks.h

@@ -8,17 +8,17 @@
 /*
  * Access type modifiers.
  */
-#define KCSAN_ACCESS_WRITE 0x1
+#define KCSAN_ACCESS_WRITE  0x1
 #define KCSAN_ACCESS_ATOMIC 0x2
 
 /*
- * __kcsan_*: Always calls into runtime when KCSAN is enabled. This may be used
+ * __kcsan_*: Always calls into the runtime when KCSAN is enabled. This may be used
  * even in compilation units that selectively disable KCSAN, but must use KCSAN
- * to validate access to an address.   Never use these in header files!
+ * to validate access to an address. Never use these in header files!
  */
 #ifdef CONFIG_KCSAN
 /**
- * __kcsan_check_access - check generic access for data race
+ * __kcsan_check_access - check generic access for data races
  *
  * @ptr address of access
  * @size size of access
@@ -32,7 +32,7 @@ static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
 #endif
 
 /*
- * kcsan_*: Only calls into runtime when the particular compilation unit has
+ * kcsan_*: Only calls into the runtime when the particular compilation unit has
  * KCSAN instrumentation enabled. May be used in header files.
  */
 #ifdef __SANITIZE_THREAD__
@@ -77,16 +77,12 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size,
 	kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE)
 
 /*
- * Check for atomic accesses: if atomic access are not ignored, this simply
- * aliases to kcsan_check_access, otherwise becomes a no-op.
+ * Check for atomic accesses: if atomic accesses are not ignored, this simply
+ * aliases to kcsan_check_access(), otherwise becomes a no-op.
  */
 #ifdef CONFIG_KCSAN_IGNORE_ATOMICS
-#define kcsan_check_atomic_read(...)                                           \
-	do {                                                                   \
-	} while (0)
-#define kcsan_check_atomic_write(...)                                          \
-	do {                                                                   \
-	} while (0)
+#define kcsan_check_atomic_read(...)	do { } while (0)
+#define kcsan_check_atomic_write(...)	do { } while (0)
 #else
 #define kcsan_check_atomic_read(ptr, size)                                     \
 	kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC)

include/linux/kcsan.h

@@ -94,21 +94,14 @@ void kcsan_atomic_next(int n);
 
 #else /* CONFIG_KCSAN */
 
-static inline void kcsan_init(void) { }
-
-static inline void kcsan_disable_current(void) { }
-
-static inline void kcsan_enable_current(void) { }
-
-static inline void kcsan_nestable_atomic_begin(void) { }
-
-static inline void kcsan_nestable_atomic_end(void) { }
-
-static inline void kcsan_flat_atomic_begin(void) { }
-
-static inline void kcsan_flat_atomic_end(void) { }
-
-static inline void kcsan_atomic_next(int n) { }
+static inline void kcsan_init(void)			{ }
+static inline void kcsan_disable_current(void)		{ }
+static inline void kcsan_enable_current(void)		{ }
+static inline void kcsan_nestable_atomic_begin(void)	{ }
+static inline void kcsan_nestable_atomic_end(void)	{ }
+static inline void kcsan_flat_atomic_begin(void)	{ }
+static inline void kcsan_flat_atomic_end(void)		{ }
+static inline void kcsan_atomic_next(int n)		{ }
 
 #endif /* CONFIG_KCSAN */
 

include/linux/seqlock.h

@@ -48,7 +48,7 @@
  *
  * As a consequence, we take the following best-effort approach for raw usage
  * via seqcount_t under KCSAN: upon beginning a seq-reader critical section,
- * pessimistically mark then next KCSAN_SEQLOCK_REGION_MAX memory accesses as
+ * pessimistically mark the next KCSAN_SEQLOCK_REGION_MAX memory accesses as
  * atomics; if there is a matching read_seqcount_retry() call, no following
  * memory operations are considered atomic. Usage of seqlocks via seqlock_t
  * interface is not affected.
@@ -265,7 +265,7 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
  * usual consistency guarantee. It is one wmb cheaper, because we can
  * collapse the two back-to-back wmb()s.
  *
- * Note that, writes surrounding the barrier should be declared atomic (e.g.
+ * Note that writes surrounding the barrier should be declared atomic (e.g.
  * via WRITE_ONCE): a) to ensure the writes become visible to other threads
  * atomically, avoiding compiler optimizations; b) to document which writes are
  * meant to propagate to the reader critical section. This is necessary because
@@ -465,15 +465,15 @@ static inline unsigned read_seqbegin(const seqlock_t *sl)
 {
 	unsigned ret = read_seqcount_begin(&sl->seqcount);
 
-	kcsan_atomic_next(0);  /* non-raw usage, assume closing read_seqretry */
+	kcsan_atomic_next(0);  /* non-raw usage, assume closing read_seqretry() */
 	kcsan_flat_atomic_begin();
 	return ret;
 }
 
 static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
 {
 	/*
-	 * Assume not nested: read_seqretry may be called multiple times when
+	 * Assume not nested: read_seqretry() may be called multiple times when
 	 * completing read critical section.
 	 */
 	kcsan_flat_atomic_end();

kernel/kcsan/atomic.h

@@ -6,7 +6,7 @@
 #include <linux/jiffies.h>
 
 /*
- * Helper that returns true if access to ptr should be considered as an atomic
+ * Helper that returns true if access to @ptr should be considered an atomic
  * access, even though it is not explicitly atomic.
  *
  * List all volatile globals that have been observed in races, to suppress

kernel/kcsan/core.c

@@ -19,10 +19,10 @@ bool kcsan_enabled;
 
 /* Per-CPU kcsan_ctx for interrupts */
 static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
-	.disable_count = 0,
-	.atomic_next = 0,
-	.atomic_nest_count = 0,
-	.in_flat_atomic = false,
+	.disable_count		= 0,
+	.atomic_next		= 0,
+	.atomic_nest_count	= 0,
+	.in_flat_atomic		= false,
 };
 
 /*
@@ -50,11 +50,11 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
  *   slot=9:  [10, 11,  9]
  *   slot=63: [64, 65, 63]
  */
-#define NUM_SLOTS (1 + 2 * KCSAN_CHECK_ADJACENT)
+#define NUM_SLOTS (1 + 2*KCSAN_CHECK_ADJACENT)
 #define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
 
 /*
- * SLOT_IDX_FAST is used in fast-path. Not first checking the address's primary
+ * SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
  * slot (middle) is fine if we assume that data races occur rarely. The set of
  * indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
  * {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
@@ -68,17 +68,18 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
  * zero-initialized state matches INVALID_WATCHPOINT.
  *
  * Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
- * use more complicated SLOT_IDX_FAST calculation with modulo in fast-path.
+ * use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
  */
-static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS - 1];
+static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
 
 /*
  * Instructions to skip watching counter, used in should_watch(). We use a
  * per-CPU counter to avoid excessive contention.
  */
 static DEFINE_PER_CPU(long, kcsan_skip);
 
-static inline atomic_long_t *find_watchpoint(unsigned long addr, size_t size,
+static inline atomic_long_t *find_watchpoint(unsigned long addr,
+					     size_t size,
 					     bool expect_write,
 					     long *encoded_watchpoint)
 {
@@ -110,8 +111,8 @@ static inline atomic_long_t *find_watchpoint(unsigned long addr, size_t size,
 	return NULL;
 }
 
-static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
-					       bool is_write)
+static inline atomic_long_t *
+insert_watchpoint(unsigned long addr, size_t size, bool is_write)
 {
 	const int slot = watchpoint_slot(addr);
 	const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
@@ -120,21 +121,16 @@ static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
 
 	/* Check slot index logic, ensuring we stay within array bounds. */
 	BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
-	BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT + 1) != 0);
-	BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
-			      KCSAN_CHECK_ADJACENT) !=
-		     ARRAY_SIZE(watchpoints) - 1);
-	BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
-			      KCSAN_CHECK_ADJACENT + 1) !=
-		     ARRAY_SIZE(watchpoints) - NUM_SLOTS);
+	BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
+	BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
+	BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
 
 	for (i = 0; i < NUM_SLOTS; ++i) {
 		long expect_val = INVALID_WATCHPOINT;
 
 		/* Try to acquire this slot. */
 		watchpoint = &watchpoints[SLOT_IDX(slot, i)];
-		if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val,
-						    encoded_watchpoint))
+		if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
 			return watchpoint;
 	}
 
@@ -150,26 +146,24 @@ static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
  *	2. the thread that set up the watchpoint already removed it;
  *	3. the watchpoint was removed and then re-used.
  */
-static inline bool try_consume_watchpoint(atomic_long_t *watchpoint,
-					  long encoded_watchpoint)
+static inline bool
+try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
 {
-	return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint,
-					       CONSUMED_WATCHPOINT);
+	return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
 }
 
 /*
  * Return true if watchpoint was not touched, false if consumed.
  */
 static inline bool remove_watchpoint(atomic_long_t *watchpoint)
 {
-	return atomic_long_xchg_relaxed(watchpoint, INVALID_WATCHPOINT) !=
-	       CONSUMED_WATCHPOINT;
+	return atomic_long_xchg_relaxed(watchpoint, INVALID_WATCHPOINT) != CONSUMED_WATCHPOINT;
 }
 
 static inline struct kcsan_ctx *get_ctx(void)
 {
 	/*
-	 * In interrupt, use raw_cpu_ptr to avoid unnecessary checks, that would
+	 * In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
 	 * also result in calls that generate warnings in uaccess regions.
 	 */
 	return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
@@ -260,7 +254,8 @@ static inline unsigned int get_delay(void)
  */
 
 static noinline void kcsan_found_watchpoint(const volatile void *ptr,
-					    size_t size, bool is_write,
+					    size_t size,
+					    bool is_write,
 					    atomic_long_t *watchpoint,
 					    long encoded_watchpoint)
 {
@@ -296,8 +291,8 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 	user_access_restore(flags);
 }
 
-static noinline void kcsan_setup_watchpoint(const volatile void *ptr,
-					    size_t size, bool is_write)
+static noinline void
+kcsan_setup_watchpoint(const volatile void *ptr, size_t size, bool is_write)
 {
 	atomic_long_t *watchpoint;
 	union {
@@ -346,8 +341,8 @@ static noinline void kcsan_setup_watchpoint(const volatile void *ptr,
 	watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
 	if (watchpoint == NULL) {
 		/*
-		 * Out of capacity: the size of `watchpoints`, and the frequency
-		 * with which `should_watch()` returns true should be tweaked so
+		 * Out of capacity: the size of 'watchpoints', and the frequency
+		 * with which should_watch() returns true should be tweaked so
 		 * that this case happens very rarely.
 		 */
 		kcsan_counter_inc(KCSAN_COUNTER_NO_CAPACITY);