1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * trace context switch
4  *
5  * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
6  *
7  */
8 #include <linux/module.h>
9 #include <linux/kallsyms.h>
10 #include <linux/uaccess.h>
11 #include <linux/ftrace.h>
12 #include <trace/events/sched.h>
13 
14 #include "trace.h"
15 
16 #define RECORD_CMDLINE	1
17 #define RECORD_TGID	2
18 
19 static int		sched_cmdline_ref;
20 static int		sched_tgid_ref;
21 static DEFINE_MUTEX(sched_register_mutex);
22 
23 static void
24 probe_sched_switch(void *ignore, bool preempt,
25 		   unsigned int prev_state,
26 		   struct task_struct *prev, struct task_struct *next)
27 {
28 	int flags;
29 
30 	flags = (RECORD_TGID * !!sched_tgid_ref) +
31 		(RECORD_CMDLINE * !!sched_cmdline_ref);
32 
33 	if (!flags)
34 		return;
35 	tracing_record_taskinfo_sched_switch(prev, next, flags);
36 }
37 
38 static void
39 probe_sched_wakeup(void *ignore, struct task_struct *wakee)
40 {
41 	int flags;
42 
43 	flags = (RECORD_TGID * !!sched_tgid_ref) +
44 		(RECORD_CMDLINE * !!sched_cmdline_ref);
45 
46 	if (!flags)
47 		return;
48 	tracing_record_taskinfo_sched_switch(current, wakee, flags);
49 }
50 
51 static int tracing_sched_register(void)
52 {
53 	int ret;
54 
55 	ret = register_trace_sched_wakeup(probe_sched_wakeup, NULL);
56 	if (ret) {
57 		pr_info("wakeup trace: Couldn't activate tracepoint"
58 			" probe to kernel_sched_wakeup\n");
59 		return ret;
60 	}
61 
62 	ret = register_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
63 	if (ret) {
64 		pr_info("wakeup trace: Couldn't activate tracepoint"
65 			" probe to kernel_sched_wakeup_new\n");
66 		goto fail_deprobe;
67 	}
68 
69 	ret = register_trace_sched_switch(probe_sched_switch, NULL);
70 	if (ret) {
71 		pr_info("sched trace: Couldn't activate tracepoint"
72 			" probe to kernel_sched_switch\n");
73 		goto fail_deprobe_wake_new;
74 	}
75 
76 	return ret;
77 fail_deprobe_wake_new:
78 	unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
79 fail_deprobe:
80 	unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
81 	return ret;
82 }
83 
84 static void tracing_sched_unregister(void)
85 {
86 	unregister_trace_sched_switch(probe_sched_switch, NULL);
87 	unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
88 	unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
89 }
90 
91 static void tracing_start_sched_switch(int ops)
92 {
93 	bool sched_register;
94 
95 	mutex_lock(&sched_register_mutex);
96 	sched_register = (!sched_cmdline_ref && !sched_tgid_ref);
97 
98 	switch (ops) {
99 	case RECORD_CMDLINE:
100 		sched_cmdline_ref++;
101 		break;
102 
103 	case RECORD_TGID:
104 		sched_tgid_ref++;
105 		break;
106 	}
107 
108 	if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
109 		tracing_sched_register();
110 	mutex_unlock(&sched_register_mutex);
111 }
112 
113 static void tracing_stop_sched_switch(int ops)
114 {
115 	mutex_lock(&sched_register_mutex);
116 
117 	switch (ops) {
118 	case RECORD_CMDLINE:
119 		sched_cmdline_ref--;
120 		break;
121 
122 	case RECORD_TGID:
123 		sched_tgid_ref--;
124 		break;
125 	}
126 
127 	if (!sched_cmdline_ref && !sched_tgid_ref)
128 		tracing_sched_unregister();
129 	mutex_unlock(&sched_register_mutex);
130 }
131 
132 void tracing_start_cmdline_record(void)
133 {
134 	tracing_start_sched_switch(RECORD_CMDLINE);
135 }
136 
137 void tracing_stop_cmdline_record(void)
138 {
139 	tracing_stop_sched_switch(RECORD_CMDLINE);
140 }
141 
142 void tracing_start_tgid_record(void)
143 {
144 	tracing_start_sched_switch(RECORD_TGID);
145 }
146 
147 void tracing_stop_tgid_record(void)
148 {
149 	tracing_stop_sched_switch(RECORD_TGID);
150 }
151