kcsan: Refactor reading of instrumented memory

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>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 4b84c8e..6bfd304 100644 (file)
--- 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)