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 extern void my_direct_func(struct vm_area_struct *vma,
   9                            unsigned long address, unsigned int flags);
  10
  11 void 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
  18 extern void my_tramp(void *);
  19
  20 #ifdef CONFIG_X86_64
  21
  22 #include <asm/ibt.h>
  23 #include <asm/nospec-branch.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 struct ftrace_ops direct;
  74
  75 static int __init ftrace_direct_init(void)
  76 {
  77         ftrace_set_filter_ip(&direct, (unsigned long) handle_mm_fault, 0, 0);
  78
  79         return register_ftrace_direct(&direct, (unsigned long) my_tramp);
  80 }
  81
  82 static void __exit ftrace_direct_exit(void)
  83 {
  84         unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
  85 }
  86
  87 module_init(ftrace_direct_init);
  88 module_exit(ftrace_direct_exit);
  89
  90 MODULE_AUTHOR("Steven Rostedt");
  91 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
  92 MODULE_LICENSE("GPL");