context_tracking: Fix noinstr vs KASAN

Low level noinstr context-tracking code is calling out to instrumented
code on KASAN:

  vmlinux.o: warning: objtool: __ct_user_enter+0x72: call to __kasan_check_write() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __ct_user_exit+0x47: call to __kasan_check_write() leaves .noinstr.text section

Use even lower level atomic methods to avoid the instrumentation.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.458034262@infradead.org

diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 77978e3..a09f1c1 100644 (file)
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -510,7 +510,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
                         * In this we case we don't care about any concurrency/ordering.
                         */
                        if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
-                               atomic_set(&ct->state, state);
+                               arch_atomic_set(&ct->state, state);
                } else {
                        /*
                         * Even if context tracking is disabled on this CPU, because it's outside
@@ -527,7 +527,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
                         */
                        if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
                                /* Tracking for vtime only, no concurrent RCU EQS accounting */
-                               atomic_set(&ct->state, state);
+                               arch_atomic_set(&ct->state, state);
                        } else {
                                /*
                                 * Tracking for vtime and RCU EQS. Make sure we don't race
@@ -535,7 +535,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
                                 * RCU only requires RCU_DYNTICKS_IDX increments to be fully
                                 * ordered.
                                 */
-                               atomic_add(state, &ct->state);
+                               arch_atomic_add(state, &ct->state);
                        }
                }
        }
@@ -630,12 +630,12 @@ void noinstr __ct_user_exit(enum ctx_state state)
                         * In this we case we don't care about any concurrency/ordering.
                         */
                        if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
-                               atomic_set(&ct->state, CONTEXT_KERNEL);
+                               arch_atomic_set(&ct->state, CONTEXT_KERNEL);
 
                } else {
                        if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
                                /* Tracking for vtime only, no concurrent RCU EQS accounting */
-                               atomic_set(&ct->state, CONTEXT_KERNEL);
+                               arch_atomic_set(&ct->state, CONTEXT_KERNEL);
                        } else {
                                /*
                                 * Tracking for vtime and RCU EQS. Make sure we don't race
@@ -643,7 +643,7 @@ void noinstr __ct_user_exit(enum ctx_state state)
                                 * RCU only requires RCU_DYNTICKS_IDX increments to be fully
                                 * ordered.
                                 */
-                               atomic_sub(state, &ct->state);
+                               arch_atomic_sub(state, &ct->state);
                        }
                }
        }