Commit 0e26e1de authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.458034262@infradead.org
parent 0e985e9d

kernel/context_tracking.c

+6 −6
Original line number Diff line number Diff line
@@ -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);

			}

		}

	}