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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 | * If callback is registered to the "global" list, the list | |
20 | * function is called and recursion checks the GLOBAL bits. | |
21 | * then this function calls... | |
22 | * The function callback, which can use the FTRACE bits to | |
23 | * check for recursion. | |
24 | * | |
25 | * Now if the arch does not support a feature, and it calls | |
26 | * the global list function which calls the ftrace callback | |
27 | * all three of these steps will do a recursion protection. | |
28 | * There's no reason to do one if the previous caller already | |
29 | * did. The recursion that we are protecting against will | |
30 | * go through the same steps again. | |
31 | * | |
32 | * To prevent the multiple recursion checks, if a recursion | |
33 | * bit is set that is higher than the MAX bit of the current | |
34 | * check, then we know that the check was made by the previous | |
35 | * caller, and we can skip the current check. | |
36 | */ | |
37 | enum { | |
38 | /* Function recursion bits */ | |
39 | TRACE_FTRACE_BIT, | |
40 | TRACE_FTRACE_NMI_BIT, | |
41 | TRACE_FTRACE_IRQ_BIT, | |
42 | TRACE_FTRACE_SIRQ_BIT, | |
43 | ||
44 | /* INTERNAL_BITs must be greater than FTRACE_BITs */ | |
45 | TRACE_INTERNAL_BIT, | |
46 | TRACE_INTERNAL_NMI_BIT, | |
47 | TRACE_INTERNAL_IRQ_BIT, | |
48 | TRACE_INTERNAL_SIRQ_BIT, | |
49 | ||
50 | TRACE_BRANCH_BIT, | |
51 | /* | |
52 | * Abuse of the trace_recursion. | |
53 | * As we need a way to maintain state if we are tracing the function | |
54 | * graph in irq because we want to trace a particular function that | |
55 | * was called in irq context but we have irq tracing off. Since this | |
56 | * can only be modified by current, we can reuse trace_recursion. | |
57 | */ | |
58 | TRACE_IRQ_BIT, | |
59 | ||
60 | /* Set if the function is in the set_graph_function file */ | |
61 | TRACE_GRAPH_BIT, | |
62 | ||
63 | /* | |
64 | * In the very unlikely case that an interrupt came in | |
65 | * at a start of graph tracing, and we want to trace | |
66 | * the function in that interrupt, the depth can be greater | |
67 | * than zero, because of the preempted start of a previous | |
68 | * trace. In an even more unlikely case, depth could be 2 | |
69 | * if a softirq interrupted the start of graph tracing, | |
70 | * followed by an interrupt preempting a start of graph | |
71 | * tracing in the softirq, and depth can even be 3 | |
72 | * if an NMI came in at the start of an interrupt function | |
73 | * that preempted a softirq start of a function that | |
74 | * preempted normal context!!!! Luckily, it can't be | |
75 | * greater than 3, so the next two bits are a mask | |
76 | * of what the depth is when we set TRACE_GRAPH_BIT | |
77 | */ | |
78 | ||
79 | TRACE_GRAPH_DEPTH_START_BIT, | |
80 | TRACE_GRAPH_DEPTH_END_BIT, | |
81 | ||
82 | /* | |
83 | * To implement set_graph_notrace, if this bit is set, we ignore | |
84 | * function graph tracing of called functions, until the return | |
85 | * function is called to clear it. | |
86 | */ | |
87 | TRACE_GRAPH_NOTRACE_BIT, | |
88 | ||
89 | /* | |
90 | * When transitioning between context, the preempt_count() may | |
91 | * not be correct. Allow for a single recursion to cover this case. | |
92 | */ | |
93 | TRACE_TRANSITION_BIT, | |
773c1670 SRV |
94 | |
95 | /* Used to prevent recursion recording from recursing. */ | |
96 | TRACE_RECORD_RECURSION_BIT, | |
0264c8c9 SRV |
97 | }; |
98 | ||
99 | #define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0) | |
100 | #define trace_recursion_clear(bit) do { (current)->trace_recursion &= ~(1<<(bit)); } while (0) | |
101 | #define trace_recursion_test(bit) ((current)->trace_recursion & (1<<(bit))) | |
102 | ||
103 | #define trace_recursion_depth() \ | |
104 | (((current)->trace_recursion >> TRACE_GRAPH_DEPTH_START_BIT) & 3) | |
105 | #define trace_recursion_set_depth(depth) \ | |
106 | do { \ | |
107 | current->trace_recursion &= \ | |
108 | ~(3 << TRACE_GRAPH_DEPTH_START_BIT); \ | |
109 | current->trace_recursion |= \ | |
110 | ((depth) & 3) << TRACE_GRAPH_DEPTH_START_BIT; \ | |
111 | } while (0) | |
112 | ||
113 | #define TRACE_CONTEXT_BITS 4 | |
114 | ||
115 | #define TRACE_FTRACE_START TRACE_FTRACE_BIT | |
116 | #define TRACE_FTRACE_MAX ((1 << (TRACE_FTRACE_START + TRACE_CONTEXT_BITS)) - 1) | |
117 | ||
118 | #define TRACE_LIST_START TRACE_INTERNAL_BIT | |
119 | #define TRACE_LIST_MAX ((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1) | |
120 | ||
121 | #define TRACE_CONTEXT_MASK TRACE_LIST_MAX | |
122 | ||
da5afbeb SRV |
123 | /* |
124 | * Used for setting context | |
125 | * NMI = 0 | |
126 | * IRQ = 1 | |
127 | * SOFTIRQ = 2 | |
128 | * NORMAL = 3 | |
129 | */ | |
130 | enum { | |
131 | TRACE_CTX_NMI, | |
132 | TRACE_CTX_IRQ, | |
133 | TRACE_CTX_SOFTIRQ, | |
134 | TRACE_CTX_NORMAL, | |
135 | }; | |
136 | ||
0264c8c9 SRV |
137 | static __always_inline int trace_get_context_bit(void) |
138 | { | |
da5afbeb | 139 | unsigned long pc = preempt_count(); |
0264c8c9 | 140 | |
da5afbeb SRV |
141 | if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
142 | return TRACE_CTX_NORMAL; | |
143 | else | |
144 | return pc & NMI_MASK ? TRACE_CTX_NMI : | |
145 | pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ; | |
0264c8c9 SRV |
146 | } |
147 | ||
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148 | #ifdef CONFIG_FTRACE_RECORD_RECURSION |
149 | extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip); | |
150 | # define do_ftrace_record_recursion(ip, pip) \ | |
151 | do { \ | |
152 | if (!trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \ | |
153 | trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \ | |
154 | ftrace_record_recursion(ip, pip); \ | |
155 | trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \ | |
156 | } \ | |
157 | } while (0) | |
158 | #else | |
159 | # define do_ftrace_record_recursion(ip, pip) do { } while (0) | |
160 | #endif | |
161 | ||
162 | static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip, | |
163 | int start, int max) | |
0264c8c9 | 164 | { |
7b68621f | 165 | unsigned int val = READ_ONCE(current->trace_recursion); |
0264c8c9 SRV |
166 | int bit; |
167 | ||
168 | /* A previous recursion check was made */ | |
169 | if ((val & TRACE_CONTEXT_MASK) > max) | |
170 | return 0; | |
171 | ||
172 | bit = trace_get_context_bit() + start; | |
173 | if (unlikely(val & (1 << bit))) { | |
174 | /* | |
175 | * It could be that preempt_count has not been updated during | |
176 | * a switch between contexts. Allow for a single recursion. | |
177 | */ | |
178 | bit = TRACE_TRANSITION_BIT; | |
7b68621f | 179 | if (val & (1 << bit)) { |
773c1670 | 180 | do_ftrace_record_recursion(ip, pip); |
0264c8c9 | 181 | return -1; |
773c1670 | 182 | } |
7b68621f SRV |
183 | } else { |
184 | /* Normal check passed, clear the transition to allow it again */ | |
185 | val &= ~(1 << TRACE_TRANSITION_BIT); | |
0264c8c9 SRV |
186 | } |
187 | ||
0264c8c9 SRV |
188 | val |= 1 << bit; |
189 | current->trace_recursion = val; | |
190 | barrier(); | |
191 | ||
192 | return bit + 1; | |
193 | } | |
194 | ||
195 | static __always_inline void trace_clear_recursion(int bit) | |
196 | { | |
0264c8c9 SRV |
197 | if (!bit) |
198 | return; | |
199 | ||
0264c8c9 | 200 | barrier(); |
7b68621f SRV |
201 | bit--; |
202 | trace_recursion_clear(bit); | |
0264c8c9 SRV |
203 | } |
204 | ||
6e4eb9cb SRV |
205 | /** |
206 | * ftrace_test_recursion_trylock - tests for recursion in same context | |
207 | * | |
208 | * Use this for ftrace callbacks. This will detect if the function | |
209 | * tracing recursed in the same context (normal vs interrupt), | |
210 | * | |
211 | * Returns: -1 if a recursion happened. | |
212 | * >= 0 if no recursion | |
213 | */ | |
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214 | static __always_inline int ftrace_test_recursion_trylock(unsigned long ip, |
215 | unsigned long parent_ip) | |
6e4eb9cb | 216 | { |
773c1670 | 217 | return trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX); |
6e4eb9cb SRV |
218 | } |
219 | ||
220 | /** | |
221 | * ftrace_test_recursion_unlock - called when function callback is complete | |
222 | * @bit: The return of a successful ftrace_test_recursion_trylock() | |
223 | * | |
224 | * This is used at the end of a ftrace callback. | |
225 | */ | |
226 | static __always_inline void ftrace_test_recursion_unlock(int bit) | |
227 | { | |
228 | trace_clear_recursion(bit); | |
229 | } | |
230 | ||
0264c8c9 SRV |
231 | #endif /* CONFIG_TRACING */ |
232 | #endif /* _LINUX_TRACE_RECURSION_H */ |