1 #ifndef _LINUX_CONTEXT_TRACKING_H
2 #define _LINUX_CONTEXT_TRACKING_H
3 
4 #include <linux/sched.h>
5 #include <linux/percpu.h>
6 #include <linux/vtime.h>
7 #include <asm/ptrace.h>
8 
9 struct context_tracking {
10 	/*
11 	 * When active is false, probes are unset in order
12 	 * to minimize overhead: TIF flags are cleared
13 	 * and calls to user_enter/exit are ignored. This
14 	 * may be further optimized using static keys.
15 	 */
16 	bool active;
17 	enum ctx_state {
18 		IN_KERNEL = 0,
19 		IN_USER,
20 	} state;
21 };
22 
23 static inline void __guest_enter(void)
24 {
25 	/*
26 	 * This is running in ioctl context so we can avoid
27 	 * the call to vtime_account() with its unnecessary idle check.
28 	 */
29 	vtime_account_system(current);
30 	current->flags |= PF_VCPU;
31 }
32 
33 static inline void __guest_exit(void)
34 {
35 	/*
36 	 * This is running in ioctl context so we can avoid
37 	 * the call to vtime_account() with its unnecessary idle check.
38 	 */
39 	vtime_account_system(current);
40 	current->flags &= ~PF_VCPU;
41 }
42 
43 #ifdef CONFIG_CONTEXT_TRACKING
44 DECLARE_PER_CPU(struct context_tracking, context_tracking);
45 
46 static inline bool context_tracking_in_user(void)
47 {
48 	return __this_cpu_read(context_tracking.state) == IN_USER;
49 }
50 
51 static inline bool context_tracking_active(void)
52 {
53 	return __this_cpu_read(context_tracking.active);
54 }
55 
56 extern void user_enter(void);
57 extern void user_exit(void);
58 
59 extern void guest_enter(void);
60 extern void guest_exit(void);
61 
62 static inline enum ctx_state exception_enter(void)
63 {
64 	enum ctx_state prev_ctx;
65 
66 	prev_ctx = this_cpu_read(context_tracking.state);
67 	user_exit();
68 
69 	return prev_ctx;
70 }
71 
72 static inline void exception_exit(enum ctx_state prev_ctx)
73 {
74 	if (prev_ctx == IN_USER)
75 		user_enter();
76 }
77 
78 extern void context_tracking_task_switch(struct task_struct *prev,
79 					 struct task_struct *next);
80 #else
81 static inline bool context_tracking_in_user(void) { return false; }
82 static inline void user_enter(void) { }
83 static inline void user_exit(void) { }
84 
85 static inline void guest_enter(void)
86 {
87 	__guest_enter();
88 }
89 
90 static inline void guest_exit(void)
91 {
92 	__guest_exit();
93 }
94 
95 static inline enum ctx_state exception_enter(void) { return 0; }
96 static inline void exception_exit(enum ctx_state prev_ctx) { }
97 static inline void context_tracking_task_switch(struct task_struct *prev,
98 						struct task_struct *next) { }
99 #endif /* !CONFIG_CONTEXT_TRACKING */
100 
101 #endif
102