LXR linux/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
   8extern void my_direct_func(struct vm_area_struct *vma,
   9                           unsigned long address, unsigned int flags);
  10
  11void 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
  18extern void my_tramp(void *);
  19
  20#ifdef CONFIG_X86_64
  21
  22asm (
  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"       ret\n"
  38"       .size           my_tramp, .-my_tramp\n"
  39"       .popsection\n"
  40);
  41
  42#endif /* CONFIG_X86_64 */
  43
  44#ifdef CONFIG_S390
  45
  46asm (
  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
  68static int __init ftrace_direct_init(void)
  69{
  70        return register_ftrace_direct((unsigned long)handle_mm_fault,
  71                                     (unsigned long)my_tramp);
  72}
  73
  74static void __exit ftrace_direct_exit(void)
  75{
  76        unregister_ftrace_direct((unsigned long)handle_mm_fault,
  77                                 (unsigned long)my_tramp);
  78}
  79
  80module_init(ftrace_direct_init);
  81module_exit(ftrace_direct_exit);
  82
  83MODULE_AUTHOR("Steven Rostedt");
  84MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
  85MODULE_LICENSE("GPL");
  86