1
2#include <linux/module.h>
3#include <linux/kthread.h>
4#include <linux/ftrace.h>
5#include <asm/asm-offsets.h>
6
7extern void my_direct_func1(unsigned long ip);
8extern void my_direct_func2(unsigned long ip);
9
10void my_direct_func1(unsigned long ip)
11{
12 trace_printk("my direct func1 ip %lx\n", ip);
13}
14
15void my_direct_func2(unsigned long ip)
16{
17 trace_printk("my direct func2 ip %lx\n", ip);
18}
19
20extern void my_tramp1(void *);
21extern void my_tramp2(void *);
22
23#ifdef CONFIG_X86_64
24
25asm (
26" .pushsection .text, \"ax\", @progbits\n"
27" .type my_tramp1, @function\n"
28" .globl my_tramp1\n"
29" my_tramp1:"
30" pushq %rbp\n"
31" movq %rsp, %rbp\n"
32" pushq %rdi\n"
33" movq 8(%rbp), %rdi\n"
34" call my_direct_func1\n"
35" popq %rdi\n"
36" leave\n"
37" ret\n"
38" .size my_tramp1, .-my_tramp1\n"
39" .type my_tramp2, @function\n"
40"\n"
41" .globl my_tramp2\n"
42" my_tramp2:"
43" pushq %rbp\n"
44" movq %rsp, %rbp\n"
45" pushq %rdi\n"
46" movq 8(%rbp), %rdi\n"
47" call my_direct_func2\n"
48" popq %rdi\n"
49" leave\n"
50" ret\n"
51" .size my_tramp2, .-my_tramp2\n"
52" .popsection\n"
53);
54
55#endif
56
57#ifdef CONFIG_S390
58
59asm (
60" .pushsection .text, \"ax\", @progbits\n"
61" .type my_tramp1, @function\n"
62" .globl my_tramp1\n"
63" my_tramp1:"
64" lgr %r1,%r15\n"
65" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
66" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
67" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
68" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
69" lgr %r2,%r0\n"
70" brasl %r14,my_direct_func1\n"
71" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
72" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
73" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
74" lgr %r1,%r0\n"
75" br %r1\n"
76" .size my_tramp1, .-my_tramp1\n"
77"\n"
78" .type my_tramp2, @function\n"
79" .globl my_tramp2\n"
80" my_tramp2:"
81" lgr %r1,%r15\n"
82" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
83" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
84" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
85" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
86" lgr %r2,%r0\n"
87" brasl %r14,my_direct_func2\n"
88" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
89" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
90" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
91" lgr %r1,%r0\n"
92" br %r1\n"
93" .size my_tramp2, .-my_tramp2\n"
94" .popsection\n"
95);
96
97#endif
98
99static unsigned long my_tramp = (unsigned long)my_tramp1;
100static unsigned long tramps[2] = {
101 (unsigned long)my_tramp1,
102 (unsigned long)my_tramp2,
103};
104
105static struct ftrace_ops direct;
106
107static int simple_thread(void *arg)
108{
109 static int t;
110 int ret = 0;
111
112 while (!kthread_should_stop()) {
113 set_current_state(TASK_INTERRUPTIBLE);
114 schedule_timeout(2 * HZ);
115
116 if (ret)
117 continue;
118 t ^= 1;
119 ret = modify_ftrace_direct_multi(&direct, tramps[t]);
120 if (!ret)
121 my_tramp = tramps[t];
122 WARN_ON_ONCE(ret);
123 }
124
125 return 0;
126}
127
128static struct task_struct *simple_tsk;
129
130static int __init ftrace_direct_multi_init(void)
131{
132 int ret;
133
134 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
135 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
136
137 ret = register_ftrace_direct_multi(&direct, my_tramp);
138
139 if (!ret)
140 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
141 return ret;
142}
143
144static void __exit ftrace_direct_multi_exit(void)
145{
146 kthread_stop(simple_tsk);
147 unregister_ftrace_direct_multi(&direct, my_tramp);
148}
149
150module_init(ftrace_direct_multi_init);
151module_exit(ftrace_direct_multi_exit);
152
153MODULE_AUTHOR("Jiri Olsa");
154MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
155MODULE_LICENSE("GPL");
156
