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(unsigned long ip);
10 extern void my_direct_func2(unsigned long ip);
11
12 void my_direct_func1(unsigned long ip)
13 {
14 trace_printk("my direct func1 ip %lx\n", ip);
15 }
16
17 void my_direct_func2(unsigned long ip)
18 {
19 trace_printk("my direct func2 ip %lx\n", ip);
20 }
21
22 extern void my_tramp1(void *);
23 extern void my_tramp2(void *);
24
25 #ifdef CONFIG_RISCV
26 #include <asm/asm.h>
27
28 asm (
29 " .pushsection .text, \"ax\", @progbits\n"
30 " .type my_tramp1, @function\n"
31 " .globl my_tramp1\n"
32 " my_tramp1:\n"
33 " addi sp,sp,-3*"SZREG"\n"
34 " "REG_S" a0,0*"SZREG"(sp)\n"
35 " "REG_S" t0,1*"SZREG"(sp)\n"
36 " "REG_S" ra,2*"SZREG"(sp)\n"
37 " mv a0,t0\n"
38 " call my_direct_func1\n"
39 " "REG_L" a0,0*"SZREG"(sp)\n"
40 " "REG_L" t0,1*"SZREG"(sp)\n"
41 " "REG_L" ra,2*"SZREG"(sp)\n"
42 " addi sp,sp,3*"SZREG"\n"
43 " jr t0\n"
44 " .size my_tramp1, .-my_tramp1\n"
45
46 " .type my_tramp2, @function\n"
47 " .globl my_tramp2\n"
48 " my_tramp2:\n"
49 " addi sp,sp,-3*"SZREG"\n"
50 " "REG_S" a0,0*"SZREG"(sp)\n"
51 " "REG_S" t0,1*"SZREG"(sp)\n"
52 " "REG_S" ra,2*"SZREG"(sp)\n"
53 " mv a0,t0\n"
54 " call my_direct_func2\n"
55 " "REG_L" a0,0*"SZREG"(sp)\n"
56 " "REG_L" t0,1*"SZREG"(sp)\n"
57 " "REG_L" ra,2*"SZREG"(sp)\n"
58 " addi sp,sp,3*"SZREG"\n"
59 " jr t0\n"
60 " .size my_tramp2, .-my_tramp2\n"
61 " .popsection\n"
62 );
63
64 #endif /* CONFIG_RISCV */
65
66 #ifdef CONFIG_X86_64
67
68 #include <asm/ibt.h>
69 #include <asm/nospec-branch.h>
70
71 asm (
72 " .pushsection .text, \"ax\", @progbits\n"
73 " .type my_tramp1, @function\n"
74 " .globl my_tramp1\n"
75 " my_tramp1:"
76 ASM_ENDBR
77 " pushq %rbp\n"
78 " movq %rsp, %rbp\n"
79 CALL_DEPTH_ACCOUNT
80 " pushq %rdi\n"
81 " movq 8(%rbp), %rdi\n"
82 " call my_direct_func1\n"
83 " popq %rdi\n"
84 " leave\n"
85 ASM_RET
86 " .size my_tramp1, .-my_tramp1\n"
87
88 " .type my_tramp2, @function\n"
89 " .globl my_tramp2\n"
90 " my_tramp2:"
91 ASM_ENDBR
92 " pushq %rbp\n"
93 " movq %rsp, %rbp\n"
94 CALL_DEPTH_ACCOUNT
95 " pushq %rdi\n"
96 " movq 8(%rbp), %rdi\n"
97 " call my_direct_func2\n"
98 " popq %rdi\n"
99 " leave\n"
100 ASM_RET
101 " .size my_tramp2, .-my_tramp2\n"
102 " .popsection\n"
103 );
104
105 #endif /* CONFIG_X86_64 */
106
107 #ifdef CONFIG_S390
108
109 asm (
110 " .pushsection .text, \"ax\", @progbits\n"
111 " .type my_tramp1, @function\n"
112 " .globl my_tramp1\n"
113 " my_tramp1:"
114 " lgr %r1,%r15\n"
115 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
116 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
117 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
118 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
119 " lgr %r2,%r0\n"
120 " brasl %r14,my_direct_func1\n"
121 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
122 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
123 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
124 " lgr %r1,%r0\n"
125 " br %r1\n"
126 " .size my_tramp1, .-my_tramp1\n"
127 "\n"
128 " .type my_tramp2, @function\n"
129 " .globl my_tramp2\n"
130 " my_tramp2:"
131 " lgr %r1,%r15\n"
132 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
133 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
134 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
135 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
136 " lgr %r2,%r0\n"
137 " brasl %r14,my_direct_func2\n"
138 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
139 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
140 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
141 " lgr %r1,%r0\n"
142 " br %r1\n"
143 " .size my_tramp2, .-my_tramp2\n"
144 " .popsection\n"
145 );
146
147 #endif /* CONFIG_S390 */
148
149 #ifdef CONFIG_ARM64
150
151 asm (
152 " .pushsection .text, \"ax\", @progbits\n"
153 " .type my_tramp1, @function\n"
154 " .globl my_tramp1\n"
155 " my_tramp1:"
156 " hint 34\n" // bti c
157 " sub sp, sp, #32\n"
158 " stp x9, x30, [sp]\n"
159 " str x0, [sp, #16]\n"
160 " mov x0, x30\n"
161 " bl my_direct_func1\n"
162 " ldp x30, x9, [sp]\n"
163 " ldr x0, [sp, #16]\n"
164 " add sp, sp, #32\n"
165 " ret x9\n"
166 " .size my_tramp1, .-my_tramp1\n"
167
168 " .type my_tramp2, @function\n"
169 " .globl my_tramp2\n"
170 " my_tramp2:"
171 " hint 34\n" // bti c
172 " sub sp, sp, #32\n"
173 " stp x9, x30, [sp]\n"
174 " str x0, [sp, #16]\n"
175 " mov x0, x30\n"
176 " bl my_direct_func2\n"
177 " ldp x30, x9, [sp]\n"
178 " ldr x0, [sp, #16]\n"
179 " add sp, sp, #32\n"
180 " ret x9\n"
181 " .size my_tramp2, .-my_tramp2\n"
182 " .popsection\n"
183 );
184
185 #endif /* CONFIG_ARM64 */
186
187 #ifdef CONFIG_LOONGARCH
188 #include <asm/asm.h>
189
190 asm (
191 " .pushsection .text, \"ax\", @progbits\n"
192 " .type my_tramp1, @function\n"
193 " .globl my_tramp1\n"
194 " my_tramp1:\n"
195 " addi.d $sp, $sp, -32\n"
196 " st.d $a0, $sp, 0\n"
197 " st.d $t0, $sp, 8\n"
198 " st.d $ra, $sp, 16\n"
199 " move $a0, $t0\n"
200 " bl my_direct_func1\n"
201 " ld.d $a0, $sp, 0\n"
202 " ld.d $t0, $sp, 8\n"
203 " ld.d $ra, $sp, 16\n"
204 " addi.d $sp, $sp, 32\n"
205 " jr $t0\n"
206 " .size my_tramp1, .-my_tramp1\n"
207
208 " .type my_tramp2, @function\n"
209 " .globl my_tramp2\n"
210 " my_tramp2:\n"
211 " addi.d $sp, $sp, -32\n"
212 " st.d $a0, $sp, 0\n"
213 " st.d $t0, $sp, 8\n"
214 " st.d $ra, $sp, 16\n"
215 " move $a0, $t0\n"
216 " bl my_direct_func2\n"
217 " ld.d $a0, $sp, 0\n"
218 " ld.d $t0, $sp, 8\n"
219 " ld.d $ra, $sp, 16\n"
220 " addi.d $sp, $sp, 32\n"
221 " jr $t0\n"
222 " .size my_tramp2, .-my_tramp2\n"
223 " .popsection\n"
224 );
225
226 #endif /* CONFIG_LOONGARCH */
227
228 static unsigned long my_tramp = (unsigned long)my_tramp1;
229 static unsigned long tramps[2] = {
230 (unsigned long)my_tramp1,
231 (unsigned long)my_tramp2,
232 };
233
234 static struct ftrace_ops direct;
235
236 static int simple_thread(void *arg)
237 {
238 static int t;
239 int ret = 0;
240
241 while (!kthread_should_stop()) {
242 set_current_state(TASK_INTERRUPTIBLE);
243 schedule_timeout(2 * HZ);
244
245 if (ret)
246 continue;
247 t ^= 1;
248 ret = modify_ftrace_direct(&direct, tramps[t]);
249 if (!ret)
250 my_tramp = tramps[t];
251 WARN_ON_ONCE(ret);
252 }
253
254 return 0;
255 }
256
257 static struct task_struct *simple_tsk;
258
259 static int __init ftrace_direct_multi_init(void)
260 {
261 int ret;
262
263 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
264 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
265
266 ret = register_ftrace_direct(&direct, my_tramp);
267
268 if (!ret)
269 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
270 return ret;
271 }
272
273 static void __exit ftrace_direct_multi_exit(void)
274 {
275 kthread_stop(simple_tsk);
276 unregister_ftrace_direct(&direct, my_tramp, true);
277 }
278
279 module_init(ftrace_direct_multi_init);
280 module_exit(ftrace_direct_multi_exit);
281
282 MODULE_AUTHOR("Jiri Olsa");
283 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
284 MODULE_LICENSE("GPL");
285
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