1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_CONTEXT_TRACKING_STATE_H
3 #define _LINUX_CONTEXT_TRACKING_STATE_H
4 
5 #include <linux/percpu.h>
6 #include <linux/static_key.h>
7 #include <linux/context_tracking_irq.h>
8 
9 /* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
10 #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
11 
12 enum ctx_state {
13 	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
14 	CONTEXT_KERNEL		= 0,
15 	CONTEXT_IDLE		= 1,
16 	CONTEXT_USER		= 2,
17 	CONTEXT_GUEST		= 3,
18 	CONTEXT_MAX		= 4,
19 };
20 
21 /* Even value for idle, else odd. */
22 #define RCU_DYNTICKS_IDX CONTEXT_MAX
23 
24 #define CT_STATE_MASK (CONTEXT_MAX - 1)
25 #define CT_DYNTICKS_MASK (~CT_STATE_MASK)
26 
27 struct context_tracking {
28 #ifdef CONFIG_CONTEXT_TRACKING_USER
29 	/*
30 	 * When active is false, probes are unset in order
31 	 * to minimize overhead: TIF flags are cleared
32 	 * and calls to user_enter/exit are ignored. This
33 	 * may be further optimized using static keys.
34 	 */
35 	bool active;
36 	int recursion;
37 #endif
38 #ifdef CONFIG_CONTEXT_TRACKING
39 	atomic_t state;
40 #endif
41 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
42 	long dynticks_nesting;		/* Track process nesting level. */
43 	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
44 #endif
45 };
46 
47 #ifdef CONFIG_CONTEXT_TRACKING
48 DECLARE_PER_CPU(struct context_tracking, context_tracking);
49 
50 static __always_inline int __ct_state(void)
51 {
52 	return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
53 }
54 #endif
55 
56 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
57 static __always_inline int ct_dynticks(void)
58 {
59 	return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_DYNTICKS_MASK;
60 }
61 
62 static __always_inline int ct_dynticks_cpu(int cpu)
63 {
64 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
65 
66 	return atomic_read(&ct->state) & CT_DYNTICKS_MASK;
67 }
68 
69 static __always_inline int ct_dynticks_cpu_acquire(int cpu)
70 {
71 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
72 
73 	return atomic_read_acquire(&ct->state) & CT_DYNTICKS_MASK;
74 }
75 
76 static __always_inline long ct_dynticks_nesting(void)
77 {
78 	return __this_cpu_read(context_tracking.dynticks_nesting);
79 }
80 
81 static __always_inline long ct_dynticks_nesting_cpu(int cpu)
82 {
83 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
84 
85 	return ct->dynticks_nesting;
86 }
87 
88 static __always_inline long ct_dynticks_nmi_nesting(void)
89 {
90 	return __this_cpu_read(context_tracking.dynticks_nmi_nesting);
91 }
92 
93 static __always_inline long ct_dynticks_nmi_nesting_cpu(int cpu)
94 {
95 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
96 
97 	return ct->dynticks_nmi_nesting;
98 }
99 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
100 
101 #ifdef CONFIG_CONTEXT_TRACKING_USER
102 extern struct static_key_false context_tracking_key;
103 
104 static __always_inline bool context_tracking_enabled(void)
105 {
106 	return static_branch_unlikely(&context_tracking_key);
107 }
108 
109 static __always_inline bool context_tracking_enabled_cpu(int cpu)
110 {
111 	return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
112 }
113 
114 static inline bool context_tracking_enabled_this_cpu(void)
115 {
116 	return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
117 }
118 
119 /**
120  * ct_state() - return the current context tracking state if known
121  *
122  * Returns the current cpu's context tracking state if context tracking
123  * is enabled.  If context tracking is disabled, returns
124  * CONTEXT_DISABLED.  This should be used primarily for debugging.
125  */
126 static __always_inline int ct_state(void)
127 {
128 	int ret;
129 
130 	if (!context_tracking_enabled())
131 		return CONTEXT_DISABLED;
132 
133 	preempt_disable();
134 	ret = __ct_state();
135 	preempt_enable();
136 
137 	return ret;
138 }
139 
140 #else
141 static __always_inline bool context_tracking_enabled(void) { return false; }
142 static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
143 static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
144 #endif /* CONFIG_CONTEXT_TRACKING_USER */
145 
146 #endif
147