diff mbox series

[v2,01/23] kcsan: Refactor reading of instrumented memory

Message ID 20211118081027.3175699-2-elver@google.com (mailing list archive)
State New
Headers show
Series kcsan: Support detecting a subset of missing memory barriers | expand

Commit Message

Marco Elver Nov. 18, 2021, 8:10 a.m. UTC
Factor out the switch statement reading instrumented memory into a
helper read_instrumented_memory().

No functional change.

Signed-off-by: Marco Elver <elver@google.com>
---
 kernel/kcsan/core.c | 51 +++++++++++++++------------------------------
 1 file changed, 17 insertions(+), 34 deletions(-)

Comments

Mark Rutland Nov. 18, 2021, 11:08 a.m. UTC | #1
On Thu, Nov 18, 2021 at 09:10:05AM +0100, Marco Elver wrote:
> Factor out the switch statement reading instrumented memory into a
> helper read_instrumented_memory().
> 
> No functional change.
> 
> Signed-off-by: Marco Elver <elver@google.com>

Nice cleanup!

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  kernel/kcsan/core.c | 51 +++++++++++++++------------------------------
>  1 file changed, 17 insertions(+), 34 deletions(-)
> 
> diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> index 4b84c8e7884b..6bfd3040f46b 100644
> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -325,6 +325,21 @@ static void delay_access(int type)
>  	udelay(delay);
>  }
>  
> +/*
> + * Reads the instrumented memory for value change detection; value change
> + * detection is currently done for accesses up to a size of 8 bytes.
> + */
> +static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
> +{
> +	switch (size) {
> +	case 1:  return READ_ONCE(*(const u8 *)ptr);
> +	case 2:  return READ_ONCE(*(const u16 *)ptr);
> +	case 4:  return READ_ONCE(*(const u32 *)ptr);
> +	case 8:  return READ_ONCE(*(const u64 *)ptr);
> +	default: return 0; /* Ignore; we do not diff the values. */
> +	}
> +}
> +
>  void kcsan_save_irqtrace(struct task_struct *task)
>  {
>  #ifdef CONFIG_TRACE_IRQFLAGS
> @@ -482,23 +497,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
>  	 * Read the current value, to later check and infer a race if the data
>  	 * was modified via a non-instrumented access, e.g. from a device.
>  	 */
> -	old = 0;
> -	switch (size) {
> -	case 1:
> -		old = READ_ONCE(*(const u8 *)ptr);
> -		break;
> -	case 2:
> -		old = READ_ONCE(*(const u16 *)ptr);
> -		break;
> -	case 4:
> -		old = READ_ONCE(*(const u32 *)ptr);
> -		break;
> -	case 8:
> -		old = READ_ONCE(*(const u64 *)ptr);
> -		break;
> -	default:
> -		break; /* ignore; we do not diff the values */
> -	}
> +	old = read_instrumented_memory(ptr, size);
>  
>  	/*
>  	 * Delay this thread, to increase probability of observing a racy
> @@ -511,23 +510,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
>  	 * racy access.
>  	 */
>  	access_mask = ctx->access_mask;
> -	new = 0;
> -	switch (size) {
> -	case 1:
> -		new = READ_ONCE(*(const u8 *)ptr);
> -		break;
> -	case 2:
> -		new = READ_ONCE(*(const u16 *)ptr);
> -		break;
> -	case 4:
> -		new = READ_ONCE(*(const u32 *)ptr);
> -		break;
> -	case 8:
> -		new = READ_ONCE(*(const u64 *)ptr);
> -		break;
> -	default:
> -		break; /* ignore; we do not diff the values */
> -	}
> +	new = read_instrumented_memory(ptr, size);
>  
>  	diff = old ^ new;
>  	if (access_mask)
> -- 
> 2.34.0.rc2.393.gf8c9666880-goog
>
diff mbox series

Patch

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 4b84c8e7884b..6bfd3040f46b 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -325,6 +325,21 @@  static void delay_access(int type)
 	udelay(delay);
 }
 
+/*
+ * Reads the instrumented memory for value change detection; value change
+ * detection is currently done for accesses up to a size of 8 bytes.
+ */
+static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
+{
+	switch (size) {
+	case 1:  return READ_ONCE(*(const u8 *)ptr);
+	case 2:  return READ_ONCE(*(const u16 *)ptr);
+	case 4:  return READ_ONCE(*(const u32 *)ptr);
+	case 8:  return READ_ONCE(*(const u64 *)ptr);
+	default: return 0; /* Ignore; we do not diff the values. */
+	}
+}
+
 void kcsan_save_irqtrace(struct task_struct *task)
 {
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -482,23 +497,7 @@  kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
 	 * Read the current value, to later check and infer a race if the data
 	 * was modified via a non-instrumented access, e.g. from a device.
 	 */
-	old = 0;
-	switch (size) {
-	case 1:
-		old = READ_ONCE(*(const u8 *)ptr);
-		break;
-	case 2:
-		old = READ_ONCE(*(const u16 *)ptr);
-		break;
-	case 4:
-		old = READ_ONCE(*(const u32 *)ptr);
-		break;
-	case 8:
-		old = READ_ONCE(*(const u64 *)ptr);
-		break;
-	default:
-		break; /* ignore; we do not diff the values */
-	}
+	old = read_instrumented_memory(ptr, size);
 
 	/*
 	 * Delay this thread, to increase probability of observing a racy
@@ -511,23 +510,7 @@  kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
 	 * racy access.
 	 */
 	access_mask = ctx->access_mask;
-	new = 0;
-	switch (size) {
-	case 1:
-		new = READ_ONCE(*(const u8 *)ptr);
-		break;
-	case 2:
-		new = READ_ONCE(*(const u16 *)ptr);
-		break;
-	case 4:
-		new = READ_ONCE(*(const u32 *)ptr);
-		break;
-	case 8:
-		new = READ_ONCE(*(const u64 *)ptr);
-		break;
-	default:
-		break; /* ignore; we do not diff the values */
-	}
+	new = read_instrumented_memory(ptr, size);
 
 	diff = old ^ new;
 	if (access_mask)