1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 #include <linux/kthread.h>
4 #include <linux/ftrace.h>
5 #include <asm/asm-offsets.h>
6
7 extern void my_direct_func1(unsigned long ip);
8 extern void my_direct_func2(unsigned long ip);
9
my_direct_func1(unsigned long ip)10 void my_direct_func1(unsigned long ip)
11 {
12 trace_printk("my direct func1 ip %lx\n", ip);
13 }
14
my_direct_func2(unsigned long ip)15 void my_direct_func2(unsigned long ip)
16 {
17 trace_printk("my direct func2 ip %lx\n", ip);
18 }
19
20 extern void my_tramp1(void *);
21 extern void my_tramp2(void *);
22
23 #ifdef CONFIG_X86_64
24
25 asm (
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 /* CONFIG_X86_64 */
56
57 #ifdef CONFIG_S390
58
59 asm (
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 /* CONFIG_S390 */
98
99 static unsigned long my_tramp = (unsigned long)my_tramp1;
100 static unsigned long tramps[2] = {
101 (unsigned long)my_tramp1,
102 (unsigned long)my_tramp2,
103 };
104
105 static struct ftrace_ops direct;
106
simple_thread(void * arg)107 static 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
128 static struct task_struct *simple_tsk;
129
ftrace_direct_multi_init(void)130 static 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
ftrace_direct_multi_exit(void)144 static void __exit ftrace_direct_multi_exit(void)
145 {
146 kthread_stop(simple_tsk);
147 unregister_ftrace_direct_multi(&direct, my_tramp);
148 }
149
150 module_init(ftrace_direct_multi_init);
151 module_exit(ftrace_direct_multi_exit);
152
153 MODULE_AUTHOR("Jiri Olsa");
154 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
155 MODULE_LICENSE("GPL");
156