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 #ifndef CONFIG_ARM64
   7 #include <asm/asm-offsets.h>
   8 #endif
   9
  10 extern void my_direct_func(struct task_struct *p);
  11
  12 void my_direct_func(struct task_struct *p)
  13 {
  14         trace_printk("waking up %s-%d\n", p->comm, p->pid);
  15 }
  16
  17 extern void my_tramp(void *);
  18
  19 #ifdef CONFIG_X86_64
  20
  21 #include <asm/ibt.h>
  22 #include <asm/nospec-branch.h>
  23
  24 asm (
  25 "       .pushsection    .text, \"ax\", @progbits\n"
  26 "       .type           my_tramp, @function\n"
  27 "       .globl          my_tramp\n"
  28 "   my_tramp:"
  29         ASM_ENDBR
  30 "       pushq %rbp\n"
  31 "       movq %rsp, %rbp\n"
  32         CALL_DEPTH_ACCOUNT
  33 "       pushq %rdi\n"
  34 "       call my_direct_func\n"
  35 "       popq %rdi\n"
  36 "       leave\n"
  37         ASM_RET
  38 "       .size           my_tramp, .-my_tramp\n"
  39 "       .popsection\n"
  40 );
  41
  42 #endif /* CONFIG_X86_64 */
  43
  44 #ifdef CONFIG_S390
  45
  46 asm (
  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
  68 #ifdef CONFIG_ARM64
  69
  70 asm (
  71 "       .pushsection    .text, \"ax\", @progbits\n"
  72 "       .type           my_tramp, @function\n"
  73 "       .globl          my_tramp\n"
  74 "   my_tramp:"
  75 "       hint    34\n" // bti    c
  76 "       sub     sp, sp, #32\n"
  77 "       stp     x9, x30, [sp]\n"
  78 "       str     x0, [sp, #16]\n"
  79 "       bl      my_direct_func\n"
  80 "       ldp     x30, x9, [sp]\n"
  81 "       ldr     x0, [sp, #16]\n"
  82 "       add     sp, sp, #32\n"
  83 "       ret     x9\n"
  84 "       .size           my_tramp, .-my_tramp\n"
  85 "       .popsection\n"
  86 );
  87
  88 #endif /* CONFIG_ARM64 */
  89
  90 #ifdef CONFIG_LOONGARCH
  91
  92 asm (
  93 "       .pushsection    .text, \"ax\", @progbits\n"
  94 "       .type           my_tramp, @function\n"
  95 "       .globl          my_tramp\n"
  96 "   my_tramp:\n"
  97 "       addi.d  $sp, $sp, -32\n"
  98 "       st.d    $a0, $sp, 0\n"
  99 "       st.d    $t0, $sp, 8\n"
 100 "       st.d    $ra, $sp, 16\n"
 101 "       bl      my_direct_func\n"
 102 "       ld.d    $a0, $sp, 0\n"
 103 "       ld.d    $t0, $sp, 8\n"
 104 "       ld.d    $ra, $sp, 16\n"
 105 "       addi.d  $sp, $sp, 32\n"
 106 "       jr      $t0\n"
 107 "       .size           my_tramp, .-my_tramp\n"
 108 "       .popsection\n"
 109 );
 110
 111 #endif /* CONFIG_LOONGARCH */
 112
 113 static struct ftrace_ops direct;
 114
 115 static int __init ftrace_direct_init(void)
 116 {
 117         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 118
 119         return register_ftrace_direct(&direct, (unsigned long) my_tramp);
 120 }
 121
 122 static void __exit ftrace_direct_exit(void)
 123 {
 124         unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
 125 }
 126
 127 module_init(ftrace_direct_init);
 128 module_exit(ftrace_direct_exit);
 129
 130 MODULE_AUTHOR("Steven Rostedt");
 131 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
 132 MODULE_LICENSE("GPL");