[RFC PATCH 3/3] stop_machine: mask sdei before running the callback

[Xiongfeng Wang]

Kprobes use 'stop_machine' to modify code which could be run in the
sdei event handler at the same time. This patch mask sdei before running
the stop_machine callback to avoid this race condition.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
---
 kernel/stop_machine.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 067cb83..7b95632 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -22,6 +22,9 @@
 #include <linux/atomic.h>
 #include <linux/nmi.h>
 #include <linux/sched/wake_q.h>
+#ifdef CONFIG_ARM64
+#include <linux/arm_sdei.h>
+#endif
 
 /*
  * Structure to determine completion condition and record errors.  May
@@ -208,6 +211,9 @@ static int multi_cpu_stop(void *data)
 			case MULTI_STOP_DISABLE_IRQ:
 				local_irq_disable();
 				hard_irq_disable();
+#ifdef CONFIG_ARM64
+				sdei_mask_local_cpu();
+#endif
 				break;
 			case MULTI_STOP_RUN:
 				if (is_active)
@@ -227,6 +233,9 @@ static int multi_cpu_stop(void *data)
 		}
 	} while (curstate != MULTI_STOP_EXIT);
 
+#ifdef CONFIG_ARM64
+	sdei_unmask_local_cpu();
+#endif
 	local_irq_restore(flags);
 	return err;
 }
-- 
1.7.12.4