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
12 void my_direct_func1(void)
13 {
14 trace_printk("my direct func1\n");
15 }
16
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_RISCV
28 #include <asm/asm.h>
29
30 asm (
31 " .pushsection .text, \"ax\", @progbits\n"
32 " .type my_tramp1, @function\n"
33 " .globl my_tramp1\n"
34 " my_tramp1:\n"
35 " addi sp,sp,-2*"SZREG"\n"
36 " "REG_S" t0,0*"SZREG"(sp)\n"
37 " "REG_S" ra,1*"SZREG"(sp)\n"
38 " call my_direct_func1\n"
39 " "REG_L" t0,0*"SZREG"(sp)\n"
40 " "REG_L" ra,1*"SZREG"(sp)\n"
41 " addi sp,sp,2*"SZREG"\n"
42 " jr t0\n"
43 " .size my_tramp1, .-my_tramp1\n"
44 " .type my_tramp2, @function\n"
45 " .globl my_tramp2\n"
46
47 " my_tramp2:\n"
48 " addi sp,sp,-2*"SZREG"\n"
49 " "REG_S" t0,0*"SZREG"(sp)\n"
50 " "REG_S" ra,1*"SZREG"(sp)\n"
51 " call my_direct_func2\n"
52 " "REG_L" t0,0*"SZREG"(sp)\n"
53 " "REG_L" ra,1*"SZREG"(sp)\n"
54 " addi sp,sp,2*"SZREG"\n"
55 " jr t0\n"
56 " .size my_tramp2, .-my_tramp2\n"
57 " .popsection\n"
58 );
59
60 #endif /* CONFIG_RISCV */
61
62 #ifdef CONFIG_X86_64
63
64 #include <asm/ibt.h>
65 #include <asm/nospec-branch.h>
66
67 asm (
68 " .pushsection .text, \"ax\", @progbits\n"
69 " .type my_tramp1, @function\n"
70 " .globl my_tramp1\n"
71 " my_tramp1:"
72 ASM_ENDBR
73 " pushq %rbp\n"
74 " movq %rsp, %rbp\n"
75 CALL_DEPTH_ACCOUNT
76 " call my_direct_func1\n"
77 " leave\n"
78 " .size my_tramp1, .-my_tramp1\n"
79 ASM_RET
80
81 " .type my_tramp2, @function\n"
82 " .globl my_tramp2\n"
83 " my_tramp2:"
84 ASM_ENDBR
85 " pushq %rbp\n"
86 " movq %rsp, %rbp\n"
87 CALL_DEPTH_ACCOUNT
88 " call my_direct_func2\n"
89 " leave\n"
90 ASM_RET
91 " .size my_tramp2, .-my_tramp2\n"
92 " .popsection\n"
93 );
94
95 #endif /* CONFIG_X86_64 */
96
97 #ifdef CONFIG_S390
98
99 asm (
100 " .pushsection .text, \"ax\", @progbits\n"
101 " .type my_tramp1, @function\n"
102 " .globl my_tramp1\n"
103 " my_tramp1:"
104 " lgr %r1,%r15\n"
105 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
106 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
107 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
108 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
109 " brasl %r14,my_direct_func1\n"
110 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
111 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
112 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
113 " lgr %r1,%r0\n"
114 " br %r1\n"
115 " .size my_tramp1, .-my_tramp1\n"
116 " .type my_tramp2, @function\n"
117 " .globl my_tramp2\n"
118 " my_tramp2:"
119 " lgr %r1,%r15\n"
120 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
121 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
122 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
123 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
124 " brasl %r14,my_direct_func2\n"
125 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
126 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
127 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
128 " lgr %r1,%r0\n"
129 " br %r1\n"
130 " .size my_tramp2, .-my_tramp2\n"
131 " .popsection\n"
132 );
133
134 #endif /* CONFIG_S390 */
135
136 #ifdef CONFIG_ARM64
137
138 asm (
139 " .pushsection .text, \"ax\", @progbits\n"
140 " .type my_tramp1, @function\n"
141 " .globl my_tramp1\n"
142 " my_tramp1:"
143 " hint 34\n" // bti c
144 " sub sp, sp, #16\n"
145 " stp x9, x30, [sp]\n"
146 " bl my_direct_func1\n"
147 " ldp x30, x9, [sp]\n"
148 " add sp, sp, #16\n"
149 " ret x9\n"
150 " .size my_tramp1, .-my_tramp1\n"
151
152 " .type my_tramp2, @function\n"
153 " .globl my_tramp2\n"
154 " my_tramp2:"
155 " hint 34\n" // bti c
156 " sub sp, sp, #16\n"
157 " stp x9, x30, [sp]\n"
158 " bl my_direct_func2\n"
159 " ldp x30, x9, [sp]\n"
160 " add sp, sp, #16\n"
161 " ret x9\n"
162 " .size my_tramp2, .-my_tramp2\n"
163 " .popsection\n"
164 );
165
166 #endif /* CONFIG_ARM64 */
167
168 #ifdef CONFIG_LOONGARCH
169
170 asm (
171 " .pushsection .text, \"ax\", @progbits\n"
172 " .type my_tramp1, @function\n"
173 " .globl my_tramp1\n"
174 " my_tramp1:\n"
175 " addi.d $sp, $sp, -16\n"
176 " st.d $t0, $sp, 0\n"
177 " st.d $ra, $sp, 8\n"
178 " bl my_direct_func1\n"
179 " ld.d $t0, $sp, 0\n"
180 " ld.d $ra, $sp, 8\n"
181 " addi.d $sp, $sp, 16\n"
182 " jr $t0\n"
183 " .size my_tramp1, .-my_tramp1\n"
184
185 " .type my_tramp2, @function\n"
186 " .globl my_tramp2\n"
187 " my_tramp2:\n"
188 " addi.d $sp, $sp, -16\n"
189 " st.d $t0, $sp, 0\n"
190 " st.d $ra, $sp, 8\n"
191 " bl my_direct_func2\n"
192 " ld.d $t0, $sp, 0\n"
193 " ld.d $ra, $sp, 8\n"
194 " addi.d $sp, $sp, 16\n"
195 " jr $t0\n"
196 " .size my_tramp2, .-my_tramp2\n"
197 " .popsection\n"
198 );
199
200 #endif /* CONFIG_LOONGARCH */
201
202 static struct ftrace_ops direct;
203
204 static unsigned long my_tramp = (unsigned long)my_tramp1;
205 static unsigned long tramps[2] = {
206 (unsigned long)my_tramp1,
207 (unsigned long)my_tramp2,
208 };
209
210 static int simple_thread(void *arg)
211 {
212 static int t;
213 int ret = 0;
214
215 while (!kthread_should_stop()) {
216 set_current_state(TASK_INTERRUPTIBLE);
217 schedule_timeout(2 * HZ);
218
219 if (ret)
220 continue;
221 t ^= 1;
222 ret = modify_ftrace_direct(&direct, tramps[t]);
223 if (!ret)
224 my_tramp = tramps[t];
225 WARN_ON_ONCE(ret);
226 }
227
228 return 0;
229 }
230
231 static struct task_struct *simple_tsk;
232
233 static int __init ftrace_direct_init(void)
234 {
235 int ret;
236
237 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
238 ret = register_ftrace_direct(&direct, my_tramp);
239
240 if (!ret)
241 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
242 return ret;
243 }
244
245 static void __exit ftrace_direct_exit(void)
246 {
247 kthread_stop(simple_tsk);
248 unregister_ftrace_direct(&direct, my_tramp, true);
249 }
250
251 module_init(ftrace_direct_init);
252 module_exit(ftrace_direct_exit);
253
254 MODULE_AUTHOR("Steven Rostedt");
255 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
256 MODULE_LICENSE("GPL");
257
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