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 #include <asm/nospec-branch.h> 8 9 extern void my_direct_func(struct vm_area_struct *vma, 10 unsigned long address, unsigned int flags); 11 12 void my_direct_func(struct vm_area_struct *vma, 13 unsigned long address, unsigned int flags) 14 { 15 trace_printk("handle mm fault vma=%p address=%lx flags=%x\n", 16 vma, address, flags); 17 } 18 19 extern void my_tramp(void *); 20 21 #ifdef CONFIG_X86_64 22 23 #include <asm/ibt.h> 24 25 asm ( 26 " .pushsection .text, \"ax\", @progbits\n" 27 " .type my_tramp, @function\n" 28 " .globl my_tramp\n" 29 " my_tramp:" 30 ASM_ENDBR 31 " pushq %rbp\n" 32 " movq %rsp, %rbp\n" 33 CALL_DEPTH_ACCOUNT 34 " pushq %rdi\n" 35 " pushq %rsi\n" 36 " pushq %rdx\n" 37 " call my_direct_func\n" 38 " popq %rdx\n" 39 " popq %rsi\n" 40 " popq %rdi\n" 41 " leave\n" 42 ASM_RET 43 " .size my_tramp, .-my_tramp\n" 44 " .popsection\n" 45 ); 46 47 #endif /* CONFIG_X86_64 */ 48 49 #ifdef CONFIG_S390 50 51 asm ( 52 " .pushsection .text, \"ax\", @progbits\n" 53 " .type my_tramp, @function\n" 54 " .globl my_tramp\n" 55 " my_tramp:" 56 " lgr %r1,%r15\n" 57 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 58 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 59 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 60 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 61 " brasl %r14,my_direct_func\n" 62 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 63 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 64 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 65 " lgr %r1,%r0\n" 66 " br %r1\n" 67 " .size my_tramp, .-my_tramp\n" 68 " .popsection\n" 69 ); 70 71 #endif /* CONFIG_S390 */ 72 73 static int __init ftrace_direct_init(void) 74 { 75 return register_ftrace_direct((unsigned long)handle_mm_fault, 76 (unsigned long)my_tramp); 77 } 78 79 static void __exit ftrace_direct_exit(void) 80 { 81 unregister_ftrace_direct((unsigned long)handle_mm_fault, 82 (unsigned long)my_tramp); 83 } 84 85 module_init(ftrace_direct_init); 86 module_exit(ftrace_direct_exit); 87 88 MODULE_AUTHOR("Steven Rostedt"); 89 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()"); 90 MODULE_LICENSE("GPL"); 91