1 files changed, 46 insertions, 0 deletions

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
new file mode 100644
index 000000000000..b28d161c1091
--- /dev/null
+++ b/include/linux/context_tracking.h
@@ -0,0 +1,46 @@
+#ifndef _LINUX_CONTEXT_TRACKING_H
+#define _LINUX_CONTEXT_TRACKING_H
+
+#ifdef CONFIG_CONTEXT_TRACKING
+#include <linux/sched.h>
+#include <linux/percpu.h>
+
+struct context_tracking {
+        /*
+         * When active is false, probes are unset in order
+         * to minimize overhead: TIF flags are cleared
+         * and calls to user_enter/exit are ignored. This
+         * may be further optimized using static keys.
+         */
+        bool active;
+        enum {
+                IN_KERNEL = 0,
+                IN_USER,
+        } state;
+};
+
+DECLARE_PER_CPU(struct context_tracking, context_tracking);
+
+static inline bool context_tracking_in_user(void)
+{
+        return __this_cpu_read(context_tracking.state) == IN_USER;
+}
+
+static inline bool context_tracking_active(void)
+{
+        return __this_cpu_read(context_tracking.active);
+}
+
+extern void user_enter(void);
+extern void user_exit(void);
+extern void context_tracking_task_switch(struct task_struct *prev,
+                                         struct task_struct *next);
+#else
+static inline bool context_tracking_in_user(void) { return false; }
+static inline void user_enter(void) { }
+static inline void user_exit(void) { }
+static inline void context_tracking_task_switch(struct task_struct *prev,
+                                                struct task_struct *next) { }
+#endif /* !CONFIG_CONTEXT_TRACKING */
+
+#endif