1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_TRACE_RECURSION_H
3#define _LINUX_TRACE_RECURSION_H
4
5#include <linux/interrupt.h>
6#include <linux/sched.h>
7
8#ifdef CONFIG_TRACING
9
10/* Only current can touch trace_recursion */
11
12/*
13 * For function tracing recursion:
14 * The order of these bits are important.
15 *
16 * When function tracing occurs, the following steps are made:
17 * If arch does not support a ftrace feature:
18 * call internal function (uses INTERNAL bits) which calls...
19 * The function callback, which can use the FTRACE bits to
20 * check for recursion.
21 */
22enum {
23 /* Function recursion bits */
24 TRACE_FTRACE_BIT,
25 TRACE_FTRACE_NMI_BIT,
26 TRACE_FTRACE_IRQ_BIT,
27 TRACE_FTRACE_SIRQ_BIT,
28 TRACE_FTRACE_TRANSITION_BIT,
29
30 /* Internal use recursion bits */
31 TRACE_INTERNAL_BIT,
32 TRACE_INTERNAL_NMI_BIT,
33 TRACE_INTERNAL_IRQ_BIT,
34 TRACE_INTERNAL_SIRQ_BIT,
35 TRACE_INTERNAL_TRANSITION_BIT,
36
37 TRACE_BRANCH_BIT,
38/*
39 * Abuse of the trace_recursion.
40 * As we need a way to maintain state if we are tracing the function
41 * graph in irq because we want to trace a particular function that
42 * was called in irq context but we have irq tracing off. Since this
43 * can only be modified by current, we can reuse trace_recursion.
44 */
45 TRACE_IRQ_BIT,
46
47 /* Used to prevent recursion recording from recursing. */
48 TRACE_RECORD_RECURSION_BIT,
49};
50
51#define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0)
52#define trace_recursion_clear(bit) do { (current)->trace_recursion &= ~(1<<(bit)); } while (0)
53#define trace_recursion_test(bit) ((current)->trace_recursion & (1<<(bit)))
54
55#define TRACE_CONTEXT_BITS 4
56
57#define TRACE_FTRACE_START TRACE_FTRACE_BIT
58
59#define TRACE_LIST_START TRACE_INTERNAL_BIT
60
61#define TRACE_CONTEXT_MASK ((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
62
63/*
64 * Used for setting context
65 * NMI = 0
66 * IRQ = 1
67 * SOFTIRQ = 2
68 * NORMAL = 3
69 */
70enum {
71 TRACE_CTX_NMI,
72 TRACE_CTX_IRQ,
73 TRACE_CTX_SOFTIRQ,
74 TRACE_CTX_NORMAL,
75 TRACE_CTX_TRANSITION,
76};
77
78static __always_inline int trace_get_context_bit(void)
79{
80 unsigned char bit = interrupt_context_level();
81
82 return TRACE_CTX_NORMAL - bit;
83}
84
85#ifdef CONFIG_FTRACE_RECORD_RECURSION
86extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
87# define do_ftrace_record_recursion(ip, pip) \
88 do { \
89 if (!trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \
90 trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
91 ftrace_record_recursion(ip, pip); \
92 trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
93 } \
94 } while (0)
95#else
96# define do_ftrace_record_recursion(ip, pip) do { } while (0)
97#endif
98
99#ifdef CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING
100# define trace_warn_on_no_rcu(ip) \
101 ({ \
102 bool __ret = !rcu_is_watching(); \
103 if (__ret && !trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \
104 trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
105 WARN_ONCE(true, "RCU not on for: %pS\n", (void *)ip); \
106 trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
107 } \
108 __ret; \
109 })
110#else
111# define trace_warn_on_no_rcu(ip) false
112#endif
113
114/*
115 * Preemption is promised to be disabled when return bit >= 0.
116 */
117static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
118 int start)
119{
120 unsigned int val = READ_ONCE(current->trace_recursion);
121 int bit;
122
123 if (trace_warn_on_no_rcu(ip))
124 return -1;
125
126 bit = trace_get_context_bit() + start;
127 if (unlikely(val & (1 << bit))) {
128 /*
129 * If an interrupt occurs during a trace, and another trace
130 * happens in that interrupt but before the preempt_count is
131 * updated to reflect the new interrupt context, then this
132 * will think a recursion occurred, and the event will be dropped.
133 * Let a single instance happen via the TRANSITION_BIT to
134 * not drop those events.
135 */
136 bit = TRACE_CTX_TRANSITION + start;
137 if (val & (1 << bit)) {
138 do_ftrace_record_recursion(ip, pip);
139 return -1;
140 }
141 }
142
143 val |= 1 << bit;
144 current->trace_recursion = val;
145 barrier();
146
147 preempt_disable_notrace();
148
149 return bit;
150}
151
152/*
153 * Preemption will be enabled (if it was previously enabled).
154 */
155static __always_inline void trace_clear_recursion(int bit)
156{
157 preempt_enable_notrace();
158 barrier();
159 trace_recursion_clear(bit);
160}
161
162/**
163 * ftrace_test_recursion_trylock - tests for recursion in same context
164 *
165 * Use this for ftrace callbacks. This will detect if the function
166 * tracing recursed in the same context (normal vs interrupt),
167 *
168 * Returns: -1 if a recursion happened.
169 * >= 0 if no recursion.
170 */
171static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
172 unsigned long parent_ip)
173{
174 return trace_test_and_set_recursion(ip, pip: parent_ip, TRACE_FTRACE_START);
175}
176
177/**
178 * ftrace_test_recursion_unlock - called when function callback is complete
179 * @bit: The return of a successful ftrace_test_recursion_trylock()
180 *
181 * This is used at the end of a ftrace callback.
182 */
183static __always_inline void ftrace_test_recursion_unlock(int bit)
184{
185 trace_clear_recursion(bit);
186}
187
188#endif /* CONFIG_TRACING */
189#endif /* _LINUX_TRACE_RECURSION_H */
190