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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#include <asm/nospec-branch.h>
7
8extern void my_direct_func1(unsigned long ip);
9extern void my_direct_func2(unsigned long ip);
10
11void my_direct_func1(unsigned long ip)
12{
13 trace_printk("my direct func1 ip %lx\n", ip);
14}
15
16void my_direct_func2(unsigned long ip)
17{
18 trace_printk("my direct func2 ip %lx\n", ip);
19}
20
21extern void my_tramp1(void *);
22extern void my_tramp2(void *);
23
24#ifdef CONFIG_X86_64
25
26#include <asm/ibt.h>
27
28asm (
29" .pushsection .text, \"ax\", @progbits\n"
30" .type my_tramp1, @function\n"
31" .globl my_tramp1\n"
32" my_tramp1:"
33 ASM_ENDBR
34" pushq %rbp\n"
35" movq %rsp, %rbp\n"
36 CALL_DEPTH_ACCOUNT
37" pushq %rdi\n"
38" movq 8(%rbp), %rdi\n"
39" call my_direct_func1\n"
40" popq %rdi\n"
41" leave\n"
42 ASM_RET
43" .size my_tramp1, .-my_tramp1\n"
44
45" .type my_tramp2, @function\n"
46" .globl my_tramp2\n"
47" my_tramp2:"
48 ASM_ENDBR
49" pushq %rbp\n"
50" movq %rsp, %rbp\n"
51 CALL_DEPTH_ACCOUNT
52" pushq %rdi\n"
53" movq 8(%rbp), %rdi\n"
54" call my_direct_func2\n"
55" popq %rdi\n"
56" leave\n"
57 ASM_RET
58" .size my_tramp2, .-my_tramp2\n"
59" .popsection\n"
60);
61
62#endif /* CONFIG_X86_64 */
63
64#ifdef CONFIG_S390
65
66asm (
67" .pushsection .text, \"ax\", @progbits\n"
68" .type my_tramp1, @function\n"
69" .globl my_tramp1\n"
70" my_tramp1:"
71" lgr %r1,%r15\n"
72" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
73" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
74" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
75" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
76" lgr %r2,%r0\n"
77" brasl %r14,my_direct_func1\n"
78" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
79" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
80" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
81" lgr %r1,%r0\n"
82" br %r1\n"
83" .size my_tramp1, .-my_tramp1\n"
84"\n"
85" .type my_tramp2, @function\n"
86" .globl my_tramp2\n"
87" my_tramp2:"
88" lgr %r1,%r15\n"
89" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
90" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
91" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
92" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
93" lgr %r2,%r0\n"
94" brasl %r14,my_direct_func2\n"
95" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
96" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
97" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
98" lgr %r1,%r0\n"
99" br %r1\n"
100" .size my_tramp2, .-my_tramp2\n"
101" .popsection\n"
102);
103
104#endif /* CONFIG_S390 */
105
106static unsigned long my_tramp = (unsigned long)my_tramp1;
107static unsigned long tramps[2] = {
108 (unsigned long)my_tramp1,
109 (unsigned long)my_tramp2,
110};
111
112static struct ftrace_ops direct;
113
114static int simple_thread(void *arg)
115{
116 static int t;
117 int ret = 0;
118
119 while (!kthread_should_stop()) {
120 set_current_state(TASK_INTERRUPTIBLE);
121 schedule_timeout(2 * HZ);
122
123 if (ret)
124 continue;
125 t ^= 1;
126 ret = modify_ftrace_direct_multi(&direct, tramps[t]);
127 if (!ret)
128 my_tramp = tramps[t];
129 WARN_ON_ONCE(ret);
130 }
131
132 return 0;
133}
134
135static struct task_struct *simple_tsk;
136
137static int __init ftrace_direct_multi_init(void)
138{
139 int ret;
140
141 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
142 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
143
144 ret = register_ftrace_direct_multi(&direct, my_tramp);
145
146 if (!ret)
147 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
148 return ret;
149}
150
151static void __exit ftrace_direct_multi_exit(void)
152{
153 kthread_stop(simple_tsk);
154 unregister_ftrace_direct_multi(&direct, my_tramp);
155}
156
157module_init(ftrace_direct_multi_init);
158module_exit(ftrace_direct_multi_exit);
159
160MODULE_AUTHOR("Jiri Olsa");
161MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
162MODULE_LICENSE("GPL");