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