samples/ftrace/ftrace-direct-too.c

   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");