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 		   struct task_struct *prev, struct task_struct *next)
26 {
27 	int flags;
28 
29 	flags = (RECORD_TGID * !!sched_tgid_ref) +
30 		(RECORD_CMDLINE * !!sched_cmdline_ref);
31 
32 	if (!flags)
33 		return;
34 	tracing_record_taskinfo_sched_switch(prev, next, flags);
35 }
36 
37 static void
38 probe_sched_wakeup(void *ignore, struct task_struct *wakee)
39 {
40 	int flags;
41 
42 	flags = (RECORD_TGID * !!sched_tgid_ref) +
43 		(RECORD_CMDLINE * !!sched_cmdline_ref);
44 
45 	if (!flags)
46 		return;
47 	tracing_record_taskinfo(current, flags);
48 }
49 
50 static int tracing_sched_register(void)
51 {
52 	int ret;
53 
54 	ret = register_trace_sched_wakeup(probe_sched_wakeup, NULL);
55 	if (ret) {
56 		pr_info("wakeup trace: Couldn't activate tracepoint"
57 			" probe to kernel_sched_wakeup\n");
58 		return ret;
59 	}
60 
61 	ret = register_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
62 	if (ret) {
63 		pr_info("wakeup trace: Couldn't activate tracepoint"
64 			" probe to kernel_sched_wakeup_new\n");
65 		goto fail_deprobe;
66 	}
67 
68 	ret = register_trace_sched_switch(probe_sched_switch, NULL);
69 	if (ret) {
70 		pr_info("sched trace: Couldn't activate tracepoint"
71 			" probe to kernel_sched_switch\n");
72 		goto fail_deprobe_wake_new;
73 	}
74 
75 	return ret;
76 fail_deprobe_wake_new:
77 	unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
78 fail_deprobe:
79 	unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
80 	return ret;
81 }
82 
83 static void tracing_sched_unregister(void)
84 {
85 	unregister_trace_sched_switch(probe_sched_switch, NULL);
86 	unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
87 	unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
88 }
89 
90 static void tracing_start_sched_switch(int ops)
91 {
92 	bool sched_register;
93 
94 	mutex_lock(&sched_register_mutex);
95 	sched_register = (!sched_cmdline_ref && !sched_tgid_ref);
96 
97 	switch (ops) {
98 	case RECORD_CMDLINE:
99 		sched_cmdline_ref++;
100 		break;
101 
102 	case RECORD_TGID:
103 		sched_tgid_ref++;
104 		break;
105 	}
106 
107 	if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
108 		tracing_sched_register();
109 	mutex_unlock(&sched_register_mutex);
110 }
111 
112 static void tracing_stop_sched_switch(int ops)
113 {
114 	mutex_lock(&sched_register_mutex);
115 
116 	switch (ops) {
117 	case RECORD_CMDLINE:
118 		sched_cmdline_ref--;
119 		break;
120 
121 	case RECORD_TGID:
122 		sched_tgid_ref--;
123 		break;
124 	}
125 
126 	if (!sched_cmdline_ref && !sched_tgid_ref)
127 		tracing_sched_unregister();
128 	mutex_unlock(&sched_register_mutex);
129 }
130 
131 void tracing_start_cmdline_record(void)
132 {
133 	tracing_start_sched_switch(RECORD_CMDLINE);
134 }
135 
136 void tracing_stop_cmdline_record(void)
137 {
138 	tracing_stop_sched_switch(RECORD_CMDLINE);
139 }
140 
141 void tracing_start_tgid_record(void)
142 {
143 	tracing_start_sched_switch(RECORD_TGID);
144 }
145 
146 void tracing_stop_tgid_record(void)
147 {
148 	tracing_stop_sched_switch(RECORD_TGID);
149 }
150