samples/ftrace/ftrace-direct.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/module.h>
   3
   4 #include <linux/sched.h> /* for wake_up_process() */
   5 #include <linux/ftrace.h>
   6 #include <asm/asm-offsets.h>
   7
   8 extern void my_direct_func(struct task_struct *p);
   9
  10 void my_direct_func(struct task_struct *p)
  11 {
  12         trace_printk("waking up %s-%d\n", p->comm, p->pid);
  13 }
  14
  15 extern void my_tramp(void *);
  16
  17 #ifdef CONFIG_X86_64
  18
  19 #include <asm/ibt.h>
  20 #include <asm/nospec-branch.h>
  21
  22 asm (
  23 "       .pushsection    .text, \"ax\", @progbits\n"
  24 "       .type           my_tramp, @function\n"
  25 "       .globl          my_tramp\n"
  26 "   my_tramp:"
  27         ASM_ENDBR
  28 "       pushq %rbp\n"
  29 "       movq %rsp, %rbp\n"
  30         CALL_DEPTH_ACCOUNT
  31 "       pushq %rdi\n"
  32 "       call my_direct_func\n"
  33 "       popq %rdi\n"
  34 "       leave\n"
  35         ASM_RET
  36 "       .size           my_tramp, .-my_tramp\n"
  37 "       .popsection\n"
  38 );
  39
  40 #endif /* CONFIG_X86_64 */
  41
  42 #ifdef CONFIG_S390
  43
  44 asm (
  45 "       .pushsection    .text, \"ax\", @progbits\n"
  46 "       .type           my_tramp, @function\n"
  47 "       .globl          my_tramp\n"
  48 "   my_tramp:"
  49 "       lgr             %r1,%r15\n"
  50 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  51 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  52 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  53 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  54 "       brasl           %r14,my_direct_func\n"
  55 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  56 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  57 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  58 "       lgr             %r1,%r0\n"
  59 "       br              %r1\n"
  60 "       .size           my_tramp, .-my_tramp\n"
  61 "       .popsection\n"
  62 );
  63
  64 #endif /* CONFIG_S390 */
  65
  66 #ifdef CONFIG_LOONGARCH
  67
  68 asm (
  69 "       .pushsection    .text, \"ax\", @progbits\n"
  70 "       .type           my_tramp, @function\n"
  71 "       .globl          my_tramp\n"
  72 "   my_tramp:\n"
  73 "       addi.d  $sp, $sp, -32\n"
  74 "       st.d    $a0, $sp, 0\n"
  75 "       st.d    $t0, $sp, 8\n"
  76 "       st.d    $ra, $sp, 16\n"
  77 "       bl      my_direct_func\n"
  78 "       ld.d    $a0, $sp, 0\n"
  79 "       ld.d    $t0, $sp, 8\n"
  80 "       ld.d    $ra, $sp, 16\n"
  81 "       addi.d  $sp, $sp, 32\n"
  82 "       jr      $t0\n"
  83 "       .size           my_tramp, .-my_tramp\n"
  84 "       .popsection\n"
  85 );
  86
  87 #endif /* CONFIG_LOONGARCH */
  88
  89 static struct ftrace_ops direct;
  90
  91 static int __init ftrace_direct_init(void)
  92 {
  93         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
  94
  95         return register_ftrace_direct(&direct, (unsigned long) my_tramp);
  96 }
  97
  98 static void __exit ftrace_direct_exit(void)
  99 {
 100         unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
 101 }
 102
 103 module_init(ftrace_direct_init);
 104 module_exit(ftrace_direct_exit);
 105
 106 MODULE_AUTHOR("Steven Rostedt");
 107 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
 108 MODULE_LICENSE("GPL");