tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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#ifndef CONFIG_ARM64
7#include <asm/asm-offsets.h>
8#endif
9
10extern void my_direct_func(struct task_struct *p);
11
12void my_direct_func(struct task_struct *p)
13{
14 trace_printk("waking up %s-%d\n", p->comm, p->pid);
15}
16
17extern void my_tramp(void *);
18
19#ifdef CONFIG_X86_64
20
21#include <asm/ibt.h>
22#include <asm/nospec-branch.h>
23
24asm (
25" .pushsection .text, \"ax\", @progbits\n"
26" .type my_tramp, @function\n"
27" .globl my_tramp\n"
28" my_tramp:"
29 ASM_ENDBR
30" pushq %rbp\n"
31" movq %rsp, %rbp\n"
32 CALL_DEPTH_ACCOUNT
33" pushq %rdi\n"
34" call my_direct_func\n"
35" popq %rdi\n"
36" leave\n"
37 ASM_RET
38" .size my_tramp, .-my_tramp\n"
39" .popsection\n"
40);
41
42#endif /* CONFIG_X86_64 */
43
44#ifdef CONFIG_S390
45
46asm (
47" .pushsection .text, \"ax\", @progbits\n"
48" .type my_tramp, @function\n"
49" .globl my_tramp\n"
50" my_tramp:"
51" lgr %r1,%r15\n"
52" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
53" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
54" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
55" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
56" brasl %r14,my_direct_func\n"
57" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
58" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
59" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
60" lgr %r1,%r0\n"
61" br %r1\n"
62" .size my_tramp, .-my_tramp\n"
63" .popsection\n"
64);
65
66#endif /* CONFIG_S390 */
67
68#ifdef CONFIG_ARM64
69
70asm (
71" .pushsection .text, \"ax\", @progbits\n"
72" .type my_tramp, @function\n"
73" .globl my_tramp\n"
74" my_tramp:"
75" hint 34\n" // bti c
76" sub sp, sp, #32\n"
77" stp x9, x30, [sp]\n"
78" str x0, [sp, #16]\n"
79" bl my_direct_func\n"
80" ldp x30, x9, [sp]\n"
81" ldr x0, [sp, #16]\n"
82" add sp, sp, #32\n"
83" ret x9\n"
84" .size my_tramp, .-my_tramp\n"
85" .popsection\n"
86);
87
88#endif /* CONFIG_ARM64 */
89
90#ifdef CONFIG_LOONGARCH
91
92asm (
93" .pushsection .text, \"ax\", @progbits\n"
94" .type my_tramp, @function\n"
95" .globl my_tramp\n"
96" my_tramp:\n"
97" addi.d $sp, $sp, -32\n"
98" st.d $a0, $sp, 0\n"
99" st.d $t0, $sp, 8\n"
100" st.d $ra, $sp, 16\n"
101" bl my_direct_func\n"
102" ld.d $a0, $sp, 0\n"
103" ld.d $t0, $sp, 8\n"
104" ld.d $ra, $sp, 16\n"
105" addi.d $sp, $sp, 32\n"
106" jr $t0\n"
107" .size my_tramp, .-my_tramp\n"
108" .popsection\n"
109);
110
111#endif /* CONFIG_LOONGARCH */
112
113static struct ftrace_ops direct;
114
115static int __init ftrace_direct_init(void)
116{
117 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
118
119 return register_ftrace_direct(&direct, (unsigned long) my_tramp);
120}
121
122static void __exit ftrace_direct_exit(void)
123{
124 unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
125}
126
127module_init(ftrace_direct_init);
128module_exit(ftrace_direct_exit);
129
130MODULE_AUTHOR("Steven Rostedt");
131MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
132MODULE_LICENSE("GPL");