1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3
4 #include <linux/sched.h> /* for wake_up_process() */
5 #include <linux/ftrace.h>
6 #include <asm/asm-offsets.h>
7
8 extern void my_direct_func(struct task_struct *p);
9
my_direct_func(struct task_struct * p)10 void my_direct_func(struct task_struct *p)
11 {
12 trace_printk("waking up %s-%d\n", p->comm, p->pid);
13 }
14
15 extern void my_tramp(void *);
16
17 #ifdef CONFIG_X86_64
18
19 #include <asm/ibt.h>
20
21 asm (
22 " .pushsection .text, \"ax\", @progbits\n"
23 " .type my_tramp, @function\n"
24 " .globl my_tramp\n"
25 " my_tramp:"
26 ASM_ENDBR
27 " pushq %rbp\n"
28 " movq %rsp, %rbp\n"
29 " pushq %rdi\n"
30 " call my_direct_func\n"
31 " popq %rdi\n"
32 " leave\n"
33 ASM_RET
34 " .size my_tramp, .-my_tramp\n"
35 " .popsection\n"
36 );
37
38 #endif /* CONFIG_X86_64 */
39
40 #ifdef CONFIG_S390
41
42 asm (
43 " .pushsection .text, \"ax\", @progbits\n"
44 " .type my_tramp, @function\n"
45 " .globl my_tramp\n"
46 " my_tramp:"
47 " lgr %r1,%r15\n"
48 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
49 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
50 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
51 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
52 " brasl %r14,my_direct_func\n"
53 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
54 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
55 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
56 " lgr %r1,%r0\n"
57 " br %r1\n"
58 " .size my_tramp, .-my_tramp\n"
59 " .popsection\n"
60 );
61
62 #endif /* CONFIG_S390 */
63
ftrace_direct_init(void)64 static int __init ftrace_direct_init(void)
65 {
66 return register_ftrace_direct((unsigned long)wake_up_process,
67 (unsigned long)my_tramp);
68 }
69
ftrace_direct_exit(void)70 static void __exit ftrace_direct_exit(void)
71 {
72 unregister_ftrace_direct((unsigned long)wake_up_process,
73 (unsigned long)my_tramp);
74 }
75
76 module_init(ftrace_direct_init);
77 module_exit(ftrace_direct_exit);
78
79 MODULE_AUTHOR("Steven Rostedt");
80 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
81 MODULE_LICENSE("GPL");
82
