1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | #include <linux/module.h> |
3 | #include <linux/kthread.h> |
4 | #include <linux/trace.h> |
5 | #include <linux/trace_events.h> |
6 | #include <linux/timer.h> |
7 | #include <linux/err.h> |
8 | #include <linux/jiffies.h> |
9 | #include <linux/workqueue.h> |
10 | |
11 | /* |
12 | * Any file that uses trace points, must include the header. |
13 | * But only one file, must include the header by defining |
14 | * CREATE_TRACE_POINTS first. This will make the C code that |
15 | * creates the handles for the trace points. |
16 | */ |
17 | #define CREATE_TRACE_POINTS |
18 | #include "sample-trace-array.h" |
19 | |
20 | struct trace_array *tr; |
21 | static void mytimer_handler(struct timer_list *unused); |
22 | static struct task_struct *simple_tsk; |
23 | |
24 | static void trace_work_fn(struct work_struct *work) |
25 | { |
26 | /* |
27 | * Disable tracing for event "sample_event". |
28 | */ |
29 | trace_array_set_clr_event(tr, system: "sample-subsystem" , event: "sample_event" , |
30 | enable: false); |
31 | } |
32 | static DECLARE_WORK(trace_work, trace_work_fn); |
33 | |
34 | /* |
35 | * mytimer: Timer setup to disable tracing for event "sample_event". This |
36 | * timer is only for the purposes of the sample module to demonstrate access of |
37 | * Ftrace instances from within kernel. |
38 | */ |
39 | static DEFINE_TIMER(mytimer, mytimer_handler); |
40 | |
41 | static void mytimer_handler(struct timer_list *unused) |
42 | { |
43 | schedule_work(work: &trace_work); |
44 | } |
45 | |
46 | static void simple_thread_func(int count) |
47 | { |
48 | set_current_state(TASK_INTERRUPTIBLE); |
49 | schedule_timeout(HZ); |
50 | |
51 | /* |
52 | * Printing count value using trace_array_printk() - trace_printk() |
53 | * equivalent for the instance buffers. |
54 | */ |
55 | trace_array_printk(tr, _THIS_IP_, fmt: "trace_array_printk: count=%d\n" , |
56 | count); |
57 | /* |
58 | * Tracepoint for event "sample_event". This will print the |
59 | * current value of count and current jiffies. |
60 | */ |
61 | trace_sample_event(count, time: jiffies); |
62 | } |
63 | |
64 | static int simple_thread(void *arg) |
65 | { |
66 | int count = 0; |
67 | unsigned long delay = msecs_to_jiffies(m: 5000); |
68 | |
69 | /* |
70 | * Enable tracing for "sample_event". |
71 | */ |
72 | trace_array_set_clr_event(tr, system: "sample-subsystem" , event: "sample_event" , enable: true); |
73 | |
74 | /* |
75 | * Adding timer - mytimer. This timer will disable tracing after |
76 | * delay seconds. |
77 | * |
78 | */ |
79 | add_timer(timer: &mytimer); |
80 | mod_timer(timer: &mytimer, expires: jiffies+delay); |
81 | |
82 | while (!kthread_should_stop()) |
83 | simple_thread_func(count: count++); |
84 | |
85 | del_timer(timer: &mytimer); |
86 | cancel_work_sync(work: &trace_work); |
87 | |
88 | /* |
89 | * trace_array_put() decrements the reference counter associated with |
90 | * the trace array - "tr". We are done using the trace array, hence |
91 | * decrement the reference counter so that it can be destroyed using |
92 | * trace_array_destroy(). |
93 | */ |
94 | trace_array_put(tr); |
95 | |
96 | return 0; |
97 | } |
98 | |
99 | static int __init sample_trace_array_init(void) |
100 | { |
101 | /* |
102 | * Return a pointer to the trace array with name "sample-instance" if it |
103 | * exists, else create a new trace array. |
104 | * |
105 | * NOTE: This function increments the reference counter |
106 | * associated with the trace array - "tr". |
107 | */ |
108 | tr = trace_array_get_by_name(name: "sample-instance" , systems: "sched,timer,kprobes" ); |
109 | |
110 | if (!tr) |
111 | return -1; |
112 | /* |
113 | * If context specific per-cpu buffers havent already been allocated. |
114 | */ |
115 | trace_printk_init_buffers(); |
116 | |
117 | simple_tsk = kthread_run(simple_thread, NULL, "sample-instance" ); |
118 | if (IS_ERR(ptr: simple_tsk)) { |
119 | trace_array_put(tr); |
120 | trace_array_destroy(tr); |
121 | return -1; |
122 | } |
123 | |
124 | return 0; |
125 | } |
126 | |
127 | static void __exit sample_trace_array_exit(void) |
128 | { |
129 | kthread_stop(k: simple_tsk); |
130 | |
131 | /* |
132 | * We are unloading our module and no longer require the trace array. |
133 | * Remove/destroy "tr" using trace_array_destroy() |
134 | */ |
135 | trace_array_destroy(tr); |
136 | } |
137 | |
138 | module_init(sample_trace_array_init); |
139 | module_exit(sample_trace_array_exit); |
140 | |
141 | MODULE_AUTHOR("Divya Indi" ); |
142 | MODULE_DESCRIPTION("Sample module for kernel access to Ftrace instances" ); |
143 | MODULE_LICENSE("GPL" ); |
144 | |