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
12enum 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
27struct 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
48DECLARE_PER_CPU(struct context_tracking, context_tracking);
49#endif
50
51#ifdef CONFIG_CONTEXT_TRACKING_USER
52static __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
59static __always_inline int ct_rcu_watching(void)
60{
61 return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING_MASK;
62}
63
64static __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(v: &ct->state) & CT_RCU_WATCHING_MASK;
69}
70
71static __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(v: &ct->state) & CT_RCU_WATCHING_MASK;
76}
77
78static __always_inline long ct_nesting(void)
79{
80 return __this_cpu_read(context_tracking.nesting);
81}
82
83static __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
90static __always_inline long ct_nmi_nesting(void)
91{
92 return __this_cpu_read(context_tracking.nmi_nesting);
93}
94
95static __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
104extern struct static_key_false context_tracking_key;
105
106static __always_inline bool context_tracking_enabled(void)
107{
108 return static_branch_unlikely(&context_tracking_key);
109}
110
111static __always_inline bool context_tracking_enabled_cpu(int cpu)
112{
113 return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
114}
115
116static __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 */
128static __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
143static __always_inline bool context_tracking_enabled(void) { return false; }
144static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
145static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
146#endif /* CONFIG_CONTEXT_TRACKING_USER */
147
148#endif
149