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 #include <asm/ibt.h>
26 #include <asm/nospec-branch.h>
27
28 asm (
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
66 asm (
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
106 static unsigned long my_tramp = (unsigned long)my_tramp1;
107 static unsigned long tramps[2] = {
108 (unsigned long)my_tramp1,
109 (unsigned long)my_tramp2,
110 };
111
112 static struct ftrace_ops direct;
113
simple_thread(void * arg)114 static 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
135 static struct task_struct *simple_tsk;
136
ftrace_direct_multi_init(void)137 static 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
ftrace_direct_multi_exit(void)151 static void __exit ftrace_direct_multi_exit(void)
152 {
153 kthread_stop(simple_tsk);
154 unregister_ftrace_direct_multi(&direct, my_tramp);
155 ftrace_free_filter(&direct);
156 }
157
158 module_init(ftrace_direct_multi_init);
159 module_exit(ftrace_direct_multi_exit);
160
161 MODULE_AUTHOR("Jiri Olsa");
162 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
163 MODULE_LICENSE("GPL");
164