text: // SPDX-License-Identifier: GPL-2.0-only
  #include <linux/module.h>
  
  #include <linux/mm.h> /* for handle_mm_fault() */
  #include <linux/ftrace.h>
  #include <asm/asm-offsets.h>
  
  extern void my_direct_func(struct vm_area_struct *vma,
  			   unsigned long address, unsigned int flags);
  
  void my_direct_func(struct vm_area_struct *vma,
  			unsigned long address, unsigned int flags)
  {
  	trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",
  		     vma, address, flags);
  }
  
  extern void my_tramp(void *);
  
  #ifdef CONFIG_X86_64
  
  #include <asm/ibt.h>
  
  asm (
  "	.pushsection    .text, \"ax\", @progbits\n"
  "	.type		my_tramp, @function\n"
  "	.globl		my_tramp\n"
  "   my_tramp:"
  	ASM_ENDBR
  "	pushq %rbp\n"
  "	movq %rsp, %rbp\n"
  "	pushq %rdi\n"
  "	pushq %rsi\n"
  "	pushq %rdx\n"
  "	call my_direct_func\n"
  "	popq %rdx\n"
  "	popq %rsi\n"
  "	popq %rdi\n"
  "	leave\n"
  	ASM_RET
  "	.size		my_tramp, .-my_tramp\n"
  "	.popsection\n"
  );
  
  #endif /* CONFIG_X86_64 */
  
  #ifdef CONFIG_S390
  
  asm (
  "	.pushsection	.text, \"ax\", @progbits\n"
  "	.type		my_tramp, @function\n"
  "	.globl		my_tramp\n"
  "   my_tramp:"
  "	lgr		%r1,%r15\n"
  "	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  "	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  "	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  "	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  "	brasl		%r14,my_direct_func\n"
  "	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  "	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  "	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  "	lgr		%r1,%r0\n"
  "	br		%r1\n"
  "	.size		my_tramp, .-my_tramp\n"
  "	.popsection\n"
  );
  
  #endif /* CONFIG_S390 */
  
  static int __init ftrace_direct_init(void)
  {
  	return register_ftrace_direct((unsigned long)handle_mm_fault,
  				     (unsigned long)my_tramp);
  }
  
  static void __exit ftrace_direct_exit(void)
  {
  	unregister_ftrace_direct((unsigned long)handle_mm_fault,
  				 (unsigned long)my_tramp);
  }
  
  module_init(ftrace_direct_init);
  module_exit(ftrace_direct_exit);
  
  MODULE_AUTHOR("Steven Rostedt");
  MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
  MODULE_LICENSE("GPL");
  