samples/markers/probe-example.c

   1 /* probe-example.c
   2  *
   3  * Connects two functions to marker call sites.
   4  *
   5  * (C) Copyright 2007 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
   6  *
   7  * This file is released under the GPLv2.
   8  * See the file COPYING for more details.
   9  */
  10
  11 #include <linux/sched.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/marker.h>
  15 #include <asm/atomic.h>
  16
  17 struct probe_data {
  18         const char *name;
  19         const char *format;
  20         marker_probe_func *probe_func;
  21 };
  22
  23 void probe_subsystem_event(void *probe_data, void *call_data,
  24         const char *format, va_list *args)
  25 {
  26         /* Declare args */
  27         unsigned int value;
  28         const char *mystr;
  29
  30         /* Assign args */
  31         value = va_arg(*args, typeof(value));
  32         mystr = va_arg(*args, typeof(mystr));
  33
  34         /* Call printk */
  35         printk(KERN_INFO "Value %u, string %s\n", value, mystr);
  36
  37         /* or count, check rights, serialize data in a buffer */
  38 }
  39
  40 atomic_t eventb_count = ATOMIC_INIT(0);
  41
  42 void probe_subsystem_eventb(void *probe_data, void *call_data,
  43         const char *format, va_list *args)
  44 {
  45         /* Increment counter */
  46         atomic_inc(&eventb_count);
  47 }
  48
  49 static struct probe_data probe_array[] =
  50 {
  51         {       .name = "subsystem_event",
  52                 .format = "integer %d string %s",
  53                 .probe_func = probe_subsystem_event },
  54         {       .name = "subsystem_eventb",
  55                 .format = MARK_NOARGS,
  56                 .probe_func = probe_subsystem_eventb },
  57 };
  58
  59 static int __init probe_init(void)
  60 {
  61         int result;
  62         int i;
  63
  64         for (i = 0; i < ARRAY_SIZE(probe_array); i++) {
  65                 result = marker_probe_register(probe_array[i].name,
  66                                 probe_array[i].format,
  67                                 probe_array[i].probe_func, &probe_array[i]);
  68                 if (result)
  69                         printk(KERN_INFO "Unable to register probe %s\n",
  70                                 probe_array[i].name);
  71         }
  72         return 0;
  73 }
  74
  75 static void __exit probe_fini(void)
  76 {
  77         int i;
  78
  79         for (i = 0; i < ARRAY_SIZE(probe_array); i++)
  80                 marker_probe_unregister(probe_array[i].name,
  81                         probe_array[i].probe_func, &probe_array[i]);
  82         printk(KERN_INFO "Number of event b : %u\n",
  83                         atomic_read(&eventb_count));
  84         marker_synchronize_unregister();
  85 }
  86
  87 module_init(probe_init);
  88 module_exit(probe_fini);
  89
  90 MODULE_LICENSE("GPL");
  91 MODULE_AUTHOR("Mathieu Desnoyers");
  92 MODULE_DESCRIPTION("SUBSYSTEM Probe");