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 CT_NESTING_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
11
12 enum ctx_state {
13 CT_STATE_DISABLED = -1, /* returned by ct_state() if unknown */
14 CT_STATE_KERNEL = 0,
15 CT_STATE_IDLE = 1,
16 CT_STATE_USER = 2,
17 CT_STATE_GUEST = 3,
18 CT_STATE_MAX = 4,
19 };
20
21 /* Odd value for watching, else even. */
22 #define CT_RCU_WATCHING CT_STATE_MAX
23
24 #define CT_STATE_MASK (CT_STATE_MAX - 1)
25 #define CT_RCU_WATCHING_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 nesting; /* Track process nesting level. */
43 long 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 #endif
50
51 #ifdef CONFIG_CONTEXT_TRACKING_USER
__ct_state(void)52 static __always_inline int __ct_state(void)
53 {
54 return raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
55 }
56 #endif
57
58 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
ct_rcu_watching(void)59 static __always_inline int ct_rcu_watching(void)
60 {
61 return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING_MASK;
62 }
63
ct_rcu_watching_cpu(int cpu)64 static __always_inline int ct_rcu_watching_cpu(int cpu)
65 {
66 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
67
68 return atomic_read(&ct->state) & CT_RCU_WATCHING_MASK;
69 }
70
ct_rcu_watching_cpu_acquire(int cpu)71 static __always_inline int ct_rcu_watching_cpu_acquire(int cpu)
72 {
73 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
74
75 return atomic_read_acquire(&ct->state) & CT_RCU_WATCHING_MASK;
76 }
77
ct_nesting(void)78 static __always_inline long ct_nesting(void)
79 {
80 return __this_cpu_read(context_tracking.nesting);
81 }
82
ct_nesting_cpu(int cpu)83 static __always_inline long ct_nesting_cpu(int cpu)
84 {
85 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
86
87 return ct->nesting;
88 }
89
ct_nmi_nesting(void)90 static __always_inline long ct_nmi_nesting(void)
91 {
92 return __this_cpu_read(context_tracking.nmi_nesting);
93 }
94
ct_nmi_nesting_cpu(int cpu)95 static __always_inline long ct_nmi_nesting_cpu(int cpu)
96 {
97 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
98
99 return ct->nmi_nesting;
100 }
101 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
102
103 #ifdef CONFIG_CONTEXT_TRACKING_USER
104 extern struct static_key_false context_tracking_key;
105
context_tracking_enabled(void)106 static __always_inline bool context_tracking_enabled(void)
107 {
108 return static_branch_unlikely(&context_tracking_key);
109 }
110
context_tracking_enabled_cpu(int cpu)111 static __always_inline bool context_tracking_enabled_cpu(int cpu)
112 {
113 return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
114 }
115
context_tracking_enabled_this_cpu(void)116 static __always_inline bool context_tracking_enabled_this_cpu(void)
117 {
118 return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
119 }
120
121 /**
122 * ct_state() - return the current context tracking state if known
123 *
124 * Returns the current cpu's context tracking state if context tracking
125 * is enabled. If context tracking is disabled, returns
126 * CT_STATE_DISABLED. This should be used primarily for debugging.
127 */
ct_state(void)128 static __always_inline int ct_state(void)
129 {
130 int ret;
131
132 if (!context_tracking_enabled())
133 return CT_STATE_DISABLED;
134
135 preempt_disable();
136 ret = __ct_state();
137 preempt_enable();
138
139 return ret;
140 }
141
142 #else
context_tracking_enabled(void)143 static __always_inline bool context_tracking_enabled(void) { return false; }
context_tracking_enabled_cpu(int cpu)144 static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
context_tracking_enabled_this_cpu(void)145 static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
146 #endif /* CONFIG_CONTEXT_TRACKING_USER */
147
148 #endif
149