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 asm ( 23 " .pushsection .text, \"ax\", @progbits\n" 24 " .type my_tramp, @function\n" 25 " .globl my_tramp\n" 26 " my_tramp:" 27 " pushq %rbp\n" 28 " movq %rsp, %rbp\n" 29 " pushq %rdi\n" 30 " pushq %rsi\n" 31 " pushq %rdx\n" 32 " call my_direct_func\n" 33 " popq %rdx\n" 34 " popq %rsi\n" 35 " popq %rdi\n" 36 " leave\n" 37 ASM_RET 38 " .size my_tramp, .-my_tramp\n" 39 " .popsection\n" 40 ); 41 42 #endif /* CONFIG_X86_64 */ 43 44 #ifdef CONFIG_S390 45 46 asm ( 47 " .pushsection .text, \"ax\", @progbits\n" 48 " .type my_tramp, @function\n" 49 " .globl my_tramp\n" 50 " my_tramp:" 51 " lgr %r1,%r15\n" 52 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 53 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 54 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 55 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 56 " brasl %r14,my_direct_func\n" 57 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 58 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 59 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 60 " lgr %r1,%r0\n" 61 " br %r1\n" 62 " .size my_tramp, .-my_tramp\n" 63 " .popsection\n" 64 ); 65 66 #endif /* CONFIG_S390 */ 67 68 static int __init ftrace_direct_init(void) 69 { 70 return register_ftrace_direct((unsigned long)handle_mm_fault, 71 (unsigned long)my_tramp); 72 } 73 74 static void __exit ftrace_direct_exit(void) 75 { 76 unregister_ftrace_direct((unsigned long)handle_mm_fault, 77 (unsigned long)my_tramp); 78 } 79 80 module_init(ftrace_direct_init); 81 module_exit(ftrace_direct_exit); 82 83 MODULE_AUTHOR("Steven Rostedt"); 84 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()"); 85 MODULE_LICENSE("GPL"); 86