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 #include <asm/asm-offsets.h> 7 8 extern void my_direct_func(struct vm_area_struct *vma, 9 unsigned long address, unsigned int flags); 10 11 void my_direct_func(struct vm_area_struct *vma, 12 unsigned long address, unsigned int flags) 13 { 14 trace_printk("handle mm fault vma=%p address=%lx flags=%x\n", 15 vma, address, flags); 16 } 17 18 extern void my_tramp(void *); 19 20 #ifdef CONFIG_X86_64 21 22 #include <asm/ibt.h> 23 24 asm ( 25 " .pushsection .text, \"ax\", @progbits\n" 26 " .type my_tramp, @function\n" 27 " .globl my_tramp\n" 28 " my_tramp:" 29 ASM_ENDBR 30 " pushq %rbp\n" 31 " movq %rsp, %rbp\n" 32 " pushq %rdi\n" 33 " pushq %rsi\n" 34 " pushq %rdx\n" 35 " call my_direct_func\n" 36 " popq %rdx\n" 37 " popq %rsi\n" 38 " popq %rdi\n" 39 " leave\n" 40 ASM_RET 41 " .size my_tramp, .-my_tramp\n" 42 " .popsection\n" 43 ); 44 45 #endif /* CONFIG_X86_64 */ 46 47 #ifdef CONFIG_S390 48 49 asm ( 50 " .pushsection .text, \"ax\", @progbits\n" 51 " .type my_tramp, @function\n" 52 " .globl my_tramp\n" 53 " my_tramp:" 54 " lgr %r1,%r15\n" 55 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 56 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 57 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 58 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 59 " brasl %r14,my_direct_func\n" 60 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 61 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 62 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 63 " lgr %r1,%r0\n" 64 " br %r1\n" 65 " .size my_tramp, .-my_tramp\n" 66 " .popsection\n" 67 ); 68 69 #endif /* CONFIG_S390 */ 70 71 static int __init ftrace_direct_init(void) 72 { 73 return register_ftrace_direct((unsigned long)handle_mm_fault, 74 (unsigned long)my_tramp); 75 } 76 77 static void __exit ftrace_direct_exit(void) 78 { 79 unregister_ftrace_direct((unsigned long)handle_mm_fault, 80 (unsigned long)my_tramp); 81 } 82 83 module_init(ftrace_direct_init); 84 module_exit(ftrace_direct_exit); 85 86 MODULE_AUTHOR("Steven Rostedt"); 87 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()"); 88 MODULE_LICENSE("GPL"); 89