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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
21struct context_tracking {
22#ifdef CONFIG_CONTEXT_TRACKING_USER
23 /*
24 * When active is false, probes are unset in order
25 * to minimize overhead: TIF flags are cleared
26 * and calls to user_enter/exit are ignored. This
27 * may be further optimized using static keys.
28 */
29 bool active;
30 int recursion;
31#endif
32#ifdef CONFIG_CONTEXT_TRACKING
33 atomic_t state;
34#endif
35#ifdef CONFIG_CONTEXT_TRACKING_IDLE
36 long nesting; /* Track process nesting level. */
37 long nmi_nesting; /* Track irq/NMI nesting level. */
38#endif
39};
40
41/*
42 * We cram two different things within the same atomic variable:
43 *
44 * CT_RCU_WATCHING_START CT_STATE_START
45 * | |
46 * v v
47 * MSB [ RCU watching counter ][ context_state ] LSB
48 * ^ ^
49 * | |
50 * CT_RCU_WATCHING_END CT_STATE_END
51 *
52 * Bits are used from the LSB upwards, so unused bits (if any) will always be in
53 * upper bits of the variable.
54 */
55#ifdef CONFIG_CONTEXT_TRACKING
56#define CT_SIZE (sizeof(((struct context_tracking *)0)->state) * BITS_PER_BYTE)
57
58#define CT_STATE_WIDTH bits_per(CT_STATE_MAX - 1)
59#define CT_STATE_START 0
60#define CT_STATE_END (CT_STATE_START + CT_STATE_WIDTH - 1)
61
62#define CT_RCU_WATCHING_MAX_WIDTH (CT_SIZE - CT_STATE_WIDTH)
63#define CT_RCU_WATCHING_WIDTH (IS_ENABLED(CONFIG_RCU_DYNTICKS_TORTURE) ? 2 : CT_RCU_WATCHING_MAX_WIDTH)
64#define CT_RCU_WATCHING_START (CT_STATE_END + 1)
65#define CT_RCU_WATCHING_END (CT_RCU_WATCHING_START + CT_RCU_WATCHING_WIDTH - 1)
66#define CT_RCU_WATCHING BIT(CT_RCU_WATCHING_START)
67
68#define CT_STATE_MASK GENMASK(CT_STATE_END, CT_STATE_START)
69#define CT_RCU_WATCHING_MASK GENMASK(CT_RCU_WATCHING_END, CT_RCU_WATCHING_START)
70
71#define CT_UNUSED_WIDTH (CT_RCU_WATCHING_MAX_WIDTH - CT_RCU_WATCHING_WIDTH)
72
73static_assert(CT_STATE_WIDTH +
74 CT_RCU_WATCHING_WIDTH +
75 CT_UNUSED_WIDTH ==
76 CT_SIZE);
77
78DECLARE_PER_CPU(struct context_tracking, context_tracking);
79#endif /* CONFIG_CONTEXT_TRACKING */
80
81#ifdef CONFIG_CONTEXT_TRACKING_USER
82static __always_inline int __ct_state(void)
83{
84 return raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
85}
86#endif
87
88#ifdef CONFIG_CONTEXT_TRACKING_IDLE
89static __always_inline int ct_rcu_watching(void)
90{
91 return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING_MASK;
92}
93
94static __always_inline int ct_rcu_watching_cpu(int cpu)
95{
96 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
97
98 return atomic_read(v: &ct->state) & CT_RCU_WATCHING_MASK;
99}
100
101static __always_inline int ct_rcu_watching_cpu_acquire(int cpu)
102{
103 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
104
105 return atomic_read_acquire(v: &ct->state) & CT_RCU_WATCHING_MASK;
106}
107
108static __always_inline long ct_nesting(void)
109{
110 return __this_cpu_read(context_tracking.nesting);
111}
112
113static __always_inline long ct_nesting_cpu(int cpu)
114{
115 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
116
117 return ct->nesting;
118}
119
120static __always_inline long ct_nmi_nesting(void)
121{
122 return __this_cpu_read(context_tracking.nmi_nesting);
123}
124
125static __always_inline long ct_nmi_nesting_cpu(int cpu)
126{
127 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
128
129 return ct->nmi_nesting;
130}
131#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
132
133#ifdef CONFIG_CONTEXT_TRACKING_USER
134extern struct static_key_false context_tracking_key;
135
136static __always_inline bool context_tracking_enabled(void)
137{
138 return static_branch_unlikely(&context_tracking_key);
139}
140
141static __always_inline bool context_tracking_enabled_cpu(int cpu)
142{
143 return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
144}
145
146static __always_inline bool context_tracking_enabled_this_cpu(void)
147{
148 return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
149}
150
151/**
152 * ct_state() - return the current context tracking state if known
153 *
154 * Returns the current cpu's context tracking state if context tracking
155 * is enabled. If context tracking is disabled, returns
156 * CT_STATE_DISABLED. This should be used primarily for debugging.
157 */
158static __always_inline int ct_state(void)
159{
160 int ret;
161
162 if (!context_tracking_enabled())
163 return CT_STATE_DISABLED;
164
165 preempt_disable();
166 ret = __ct_state();
167 preempt_enable();
168
169 return ret;
170}
171
172#else
173static __always_inline bool context_tracking_enabled(void) { return false; }
174static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
175static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
176#endif /* CONFIG_CONTEXT_TRACKING_USER */
177
178#endif
179

source code of linux/include/linux/context_tracking_state.h