1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/module.h> 3 4 #include <linux/mm.h> /* for handle_mm_fault() */ 5 #include <linux/ftrace.h> 6 7 void my_direct_func(struct vm_area_struct *vma, 8 unsigned long address, unsigned int flags) 9 { 10 trace_printk("handle mm fault vma=%p address=%lx flags=%x\n", 11 vma, address, flags); 12 } 13 14 extern void my_tramp(void *); 15 16 asm ( 17 " .pushsection .text, \"ax\", @progbits\n" 18 " .type my_tramp, @function\n" 19 " .globl my_tramp\n" 20 " my_tramp:" 21 " pushq %rbp\n" 22 " movq %rsp, %rbp\n" 23 " pushq %rdi\n" 24 " pushq %rsi\n" 25 " pushq %rdx\n" 26 " call my_direct_func\n" 27 " popq %rdx\n" 28 " popq %rsi\n" 29 " popq %rdi\n" 30 " leave\n" 31 " ret\n" 32 " .size my_tramp, .-my_tramp\n" 33 " .popsection\n" 34 ); 35 36 37 static int __init ftrace_direct_init(void) 38 { 39 return register_ftrace_direct((unsigned long)handle_mm_fault, 40 (unsigned long)my_tramp); 41 } 42 43 static void __exit ftrace_direct_exit(void) 44 { 45 unregister_ftrace_direct((unsigned long)handle_mm_fault, 46 (unsigned long)my_tramp); 47 } 48 49 module_init(ftrace_direct_init); 50 module_exit(ftrace_direct_exit); 51 52 MODULE_AUTHOR("Steven Rostedt"); 53 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()"); 54 MODULE_LICENSE("GPL"); 55