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_RISCV
20#include <asm/asm.h>
21
22asm (
23" .pushsection .text, \"ax\", @progbits\n"
24" .type my_tramp, @function\n"
25" .globl my_tramp\n"
26" my_tramp:\n"
27" addi sp,sp,-3*"SZREG"\n"
28" "REG_S" a0,0*"SZREG"(sp)\n"
29" "REG_S" t0,1*"SZREG"(sp)\n"
30" "REG_S" ra,2*"SZREG"(sp)\n"
31" call my_direct_func\n"
32" "REG_L" a0,0*"SZREG"(sp)\n"
33" "REG_L" t0,1*"SZREG"(sp)\n"
34" "REG_L" ra,2*"SZREG"(sp)\n"
35" addi sp,sp,3*"SZREG"\n"
36" jr t0\n"
37" .size my_tramp, .-my_tramp\n"
38" .popsection\n"
39);
40
41#endif /* CONFIG_RISCV */
42
43#ifdef CONFIG_X86_64
44
45#include <asm/ibt.h>
46#include <asm/nospec-branch.h>
47
48asm (
49" .pushsection .text, \"ax\", @progbits\n"
50" .type my_tramp, @function\n"
51" .globl my_tramp\n"
52" my_tramp:"
53 ASM_ENDBR
54" pushq %rbp\n"
55" movq %rsp, %rbp\n"
56 CALL_DEPTH_ACCOUNT
57" pushq %rdi\n"
58" call my_direct_func\n"
59" popq %rdi\n"
60" leave\n"
61 ASM_RET
62" .size my_tramp, .-my_tramp\n"
63" .popsection\n"
64);
65
66#endif /* CONFIG_X86_64 */
67
68#ifdef CONFIG_S390
69
70asm (
71" .pushsection .text, \"ax\", @progbits\n"
72" .type my_tramp, @function\n"
73" .globl my_tramp\n"
74" my_tramp:"
75" lgr %r1,%r15\n"
76" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
77" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
78" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
79" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
80" brasl %r14,my_direct_func\n"
81" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
82" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
83" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
84" lgr %r1,%r0\n"
85" br %r1\n"
86" .size my_tramp, .-my_tramp\n"
87" .popsection\n"
88);
89
90#endif /* CONFIG_S390 */
91
92#ifdef CONFIG_ARM64
93
94asm (
95" .pushsection .text, \"ax\", @progbits\n"
96" .type my_tramp, @function\n"
97" .globl my_tramp\n"
98" my_tramp:"
99" hint 34\n" // bti c
100" sub sp, sp, #32\n"
101" stp x9, x30, [sp]\n"
102" str x0, [sp, #16]\n"
103" bl my_direct_func\n"
104" ldp x30, x9, [sp]\n"
105" ldr x0, [sp, #16]\n"
106" add sp, sp, #32\n"
107" ret x9\n"
108" .size my_tramp, .-my_tramp\n"
109" .popsection\n"
110);
111
112#endif /* CONFIG_ARM64 */
113
114#ifdef CONFIG_LOONGARCH
115
116asm (
117" .pushsection .text, \"ax\", @progbits\n"
118" .type my_tramp, @function\n"
119" .globl my_tramp\n"
120" my_tramp:\n"
121" addi.d $sp, $sp, -32\n"
122" st.d $a0, $sp, 0\n"
123" st.d $t0, $sp, 8\n"
124" st.d $ra, $sp, 16\n"
125" bl my_direct_func\n"
126" ld.d $a0, $sp, 0\n"
127" ld.d $t0, $sp, 8\n"
128" ld.d $ra, $sp, 16\n"
129" addi.d $sp, $sp, 32\n"
130" jr $t0\n"
131" .size my_tramp, .-my_tramp\n"
132" .popsection\n"
133);
134
135#endif /* CONFIG_LOONGARCH */
136
137static struct ftrace_ops direct;
138
139static int __init ftrace_direct_init(void)
140{
141 ftrace_set_filter_ip(ops: &direct, ip: (unsigned long) wake_up_process, remove: 0, reset: 0);
142
143 return register_ftrace_direct(ops: &direct, addr: (unsigned long) my_tramp);
144}
145
146static void __exit ftrace_direct_exit(void)
147{
148 unregister_ftrace_direct(ops: &direct, addr: (unsigned long)my_tramp, free_filters: true);
149}
150
151module_init(ftrace_direct_init);
152module_exit(ftrace_direct_exit);
153
154MODULE_AUTHOR("Steven Rostedt");
155MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
156MODULE_LICENSE("GPL");
157

source code of linux/samples/ftrace/ftrace-direct.c