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 #include <asm/nospec-branch.h>
21
22 asm (
23 " .pushsection .text, \"ax\", @progbits\n"
24 " .type my_tramp, @function\n"
25 " .globl my_tramp\n"
26 " my_tramp:"
27 ASM_ENDBR
28 " pushq %rbp\n"
29 " movq %rsp, %rbp\n"
30 CALL_DEPTH_ACCOUNT
31 " pushq %rdi\n"
32 " call my_direct_func\n"
33 " popq %rdi\n"
34 " leave\n"
35 ASM_RET
36 " .size my_tramp, .-my_tramp\n"
37 " .popsection\n"
38 );
39
40 #endif /* CONFIG_X86_64 */
41
42 #ifdef CONFIG_S390
43
44 asm (
45 " .pushsection .text, \"ax\", @progbits\n"
46 " .type my_tramp, @function\n"
47 " .globl my_tramp\n"
48 " my_tramp:"
49 " lgr %r1,%r15\n"
50 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
51 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
52 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
53 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
54 " brasl %r14,my_direct_func\n"
55 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
56 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
57 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
58 " lgr %r1,%r0\n"
59 " br %r1\n"
60 " .size my_tramp, .-my_tramp\n"
61 " .popsection\n"
62 );
63
64 #endif /* CONFIG_S390 */
65
ftrace_direct_init(void)66 static int __init ftrace_direct_init(void)
67 {
68 return register_ftrace_direct((unsigned long)wake_up_process,
69 (unsigned long)my_tramp);
70 }
71
ftrace_direct_exit(void)72 static void __exit ftrace_direct_exit(void)
73 {
74 unregister_ftrace_direct((unsigned long)wake_up_process,
75 (unsigned long)my_tramp);
76 }
77
78 module_init(ftrace_direct_init);
79 module_exit(ftrace_direct_exit);
80
81 MODULE_AUTHOR("Steven Rostedt");
82 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
83 MODULE_LICENSE("GPL");
84