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
10 extern void my_direct_func(struct task_struct *p);
11
12 void my_direct_func(struct task_struct *p)
13 {
14 trace_printk("waking up %s-%d\n", p->comm, p->pid);
15 }
16
17 extern void my_tramp(void *);
18
19 #ifdef CONFIG_RISCV
20 #include <asm/asm.h>
21
22 asm (
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
48 asm (
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
70 asm (
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
94 asm (
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
116 asm (
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
137 static struct ftrace_ops direct;
138
139 static int __init ftrace_direct_init(void)
140 {
141 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
142
143 return register_ftrace_direct(&direct, (unsigned long) my_tramp);
144 }
145
146 static void __exit ftrace_direct_exit(void)
147 {
148 unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
149 }
150
151 module_init(ftrace_direct_init);
152 module_exit(ftrace_direct_exit);
153
154 MODULE_AUTHOR("Steven Rostedt");
155 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
156 MODULE_LICENSE("GPL");
157
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