1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 #include <linux/kthread.h>
4 #include <linux/ftrace.h>
5 #ifndef CONFIG_ARM64
6 #include <asm/asm-offsets.h>
7 #endif
8
9 extern void my_direct_func1(void);
10 extern void my_direct_func2(void);
11
my_direct_func1(void)12 void my_direct_func1(void)
13 {
14 trace_printk("my direct func1\n");
15 }
16
my_direct_func2(void)17 void my_direct_func2(void)
18 {
19 trace_printk("my direct func2\n");
20 }
21
22 extern void my_tramp1(void *);
23 extern void my_tramp2(void *);
24
25 static unsigned long my_ip = (unsigned long)schedule;
26
27 #ifdef CONFIG_X86_64
28
29 #include <asm/ibt.h>
30 #include <asm/nospec-branch.h>
31
32 asm (
33 " .pushsection .text, \"ax\", @progbits\n"
34 " .type my_tramp1, @function\n"
35 " .globl my_tramp1\n"
36 " my_tramp1:"
37 ASM_ENDBR
38 " pushq %rbp\n"
39 " movq %rsp, %rbp\n"
40 CALL_DEPTH_ACCOUNT
41 " call my_direct_func1\n"
42 " leave\n"
43 " .size my_tramp1, .-my_tramp1\n"
44 ASM_RET
45
46 " .type my_tramp2, @function\n"
47 " .globl my_tramp2\n"
48 " my_tramp2:"
49 ASM_ENDBR
50 " pushq %rbp\n"
51 " movq %rsp, %rbp\n"
52 CALL_DEPTH_ACCOUNT
53 " call my_direct_func2\n"
54 " leave\n"
55 ASM_RET
56 " .size my_tramp2, .-my_tramp2\n"
57 " .popsection\n"
58 );
59
60 #endif /* CONFIG_X86_64 */
61
62 #ifdef CONFIG_S390
63
64 asm (
65 " .pushsection .text, \"ax\", @progbits\n"
66 " .type my_tramp1, @function\n"
67 " .globl my_tramp1\n"
68 " my_tramp1:"
69 " lgr %r1,%r15\n"
70 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
71 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
72 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
73 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
74 " brasl %r14,my_direct_func1\n"
75 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
76 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
77 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
78 " lgr %r1,%r0\n"
79 " br %r1\n"
80 " .size my_tramp1, .-my_tramp1\n"
81 " .type my_tramp2, @function\n"
82 " .globl my_tramp2\n"
83 " my_tramp2:"
84 " lgr %r1,%r15\n"
85 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
86 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
87 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
88 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
89 " brasl %r14,my_direct_func2\n"
90 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
91 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
92 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
93 " lgr %r1,%r0\n"
94 " br %r1\n"
95 " .size my_tramp2, .-my_tramp2\n"
96 " .popsection\n"
97 );
98
99 #endif /* CONFIG_S390 */
100
101 #ifdef CONFIG_ARM64
102
103 asm (
104 " .pushsection .text, \"ax\", @progbits\n"
105 " .type my_tramp1, @function\n"
106 " .globl my_tramp1\n"
107 " my_tramp1:"
108 " hint 34\n" // bti c
109 " sub sp, sp, #16\n"
110 " stp x9, x30, [sp]\n"
111 " bl my_direct_func1\n"
112 " ldp x30, x9, [sp]\n"
113 " add sp, sp, #16\n"
114 " ret x9\n"
115 " .size my_tramp1, .-my_tramp1\n"
116
117 " .type my_tramp2, @function\n"
118 " .globl my_tramp2\n"
119 " my_tramp2:"
120 " hint 34\n" // bti c
121 " sub sp, sp, #16\n"
122 " stp x9, x30, [sp]\n"
123 " bl my_direct_func2\n"
124 " ldp x30, x9, [sp]\n"
125 " add sp, sp, #16\n"
126 " ret x9\n"
127 " .size my_tramp2, .-my_tramp2\n"
128 " .popsection\n"
129 );
130
131 #endif /* CONFIG_ARM64 */
132
133 #ifdef CONFIG_LOONGARCH
134
135 asm (
136 " .pushsection .text, \"ax\", @progbits\n"
137 " .type my_tramp1, @function\n"
138 " .globl my_tramp1\n"
139 " my_tramp1:\n"
140 " addi.d $sp, $sp, -16\n"
141 " st.d $t0, $sp, 0\n"
142 " st.d $ra, $sp, 8\n"
143 " bl my_direct_func1\n"
144 " ld.d $t0, $sp, 0\n"
145 " ld.d $ra, $sp, 8\n"
146 " addi.d $sp, $sp, 16\n"
147 " jr $t0\n"
148 " .size my_tramp1, .-my_tramp1\n"
149
150 " .type my_tramp2, @function\n"
151 " .globl my_tramp2\n"
152 " my_tramp2:\n"
153 " addi.d $sp, $sp, -16\n"
154 " st.d $t0, $sp, 0\n"
155 " st.d $ra, $sp, 8\n"
156 " bl my_direct_func2\n"
157 " ld.d $t0, $sp, 0\n"
158 " ld.d $ra, $sp, 8\n"
159 " addi.d $sp, $sp, 16\n"
160 " jr $t0\n"
161 " .size my_tramp2, .-my_tramp2\n"
162 " .popsection\n"
163 );
164
165 #endif /* CONFIG_LOONGARCH */
166
167 static struct ftrace_ops direct;
168
169 static unsigned long my_tramp = (unsigned long)my_tramp1;
170 static unsigned long tramps[2] = {
171 (unsigned long)my_tramp1,
172 (unsigned long)my_tramp2,
173 };
174
simple_thread(void * arg)175 static int simple_thread(void *arg)
176 {
177 static int t;
178 int ret = 0;
179
180 while (!kthread_should_stop()) {
181 set_current_state(TASK_INTERRUPTIBLE);
182 schedule_timeout(2 * HZ);
183
184 if (ret)
185 continue;
186 t ^= 1;
187 ret = modify_ftrace_direct(&direct, tramps[t]);
188 if (!ret)
189 my_tramp = tramps[t];
190 WARN_ON_ONCE(ret);
191 }
192
193 return 0;
194 }
195
196 static struct task_struct *simple_tsk;
197
ftrace_direct_init(void)198 static int __init ftrace_direct_init(void)
199 {
200 int ret;
201
202 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
203 ret = register_ftrace_direct(&direct, my_tramp);
204
205 if (!ret)
206 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
207 return ret;
208 }
209
ftrace_direct_exit(void)210 static void __exit ftrace_direct_exit(void)
211 {
212 kthread_stop(simple_tsk);
213 unregister_ftrace_direct(&direct, my_tramp, true);
214 }
215
216 module_init(ftrace_direct_init);
217 module_exit(ftrace_direct_exit);
218
219 MODULE_AUTHOR("Steven Rostedt");
220 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
221 MODULE_LICENSE("GPL");
222