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(const struct marker *mdata, void *private,
  24         const char *format, ...)
  25 {
  26         va_list ap;
  27         /* Declare args */
  28         unsigned int value;
  29         const char *mystr;
  30
  31         /* Assign args */
  32         va_start(ap, format);
  33         value = va_arg(ap, typeof(value));
  34         mystr = va_arg(ap, typeof(mystr));
  35
  36         /* Call printk */
  37         printk(KERN_DEBUG "Value %u, string %s\n", value, mystr);
  38
  39         /* or count, check rights, serialize data in a buffer */
  40
  41         va_end(ap);
  42 }
  43
  44 atomic_t eventb_count = ATOMIC_INIT(0);
  45
  46 void probe_subsystem_eventb(const struct marker *mdata, void *private,
  47         const char *format, ...)
  48 {
  49         /* Increment counter */
  50         atomic_inc(&eventb_count);
  51 }
  52
  53 static struct probe_data probe_array[] =
  54 {
  55         {       .name = "subsystem_event",
  56                 .format = "%d %s",
  57                 .probe_func = probe_subsystem_event },
  58         {       .name = "subsystem_eventb",
  59                 .format = MARK_NOARGS,
  60                 .probe_func = probe_subsystem_eventb },
  61 };
  62
  63 static int __init probe_init(void)
  64 {
  65         int result;
  66         int i;
  67
  68         for (i = 0; i < ARRAY_SIZE(probe_array); i++) {
  69                 result = marker_probe_register(probe_array[i].name,
  70                                 probe_array[i].format,
  71                                 probe_array[i].probe_func, &probe_array[i]);
  72                 if (result)
  73                         printk(KERN_INFO "Unable to register probe %s\n",
  74                                 probe_array[i].name);
  75                 result = marker_arm(probe_array[i].name);
  76                 if (result)
  77                         printk(KERN_INFO "Unable to arm probe %s\n",
  78                                 probe_array[i].name);
  79         }
  80         return 0;
  81 }
  82
  83 static void __exit probe_fini(void)
  84 {
  85         int i;
  86
  87         for (i = 0; i < ARRAY_SIZE(probe_array); i++)
  88                 marker_probe_unregister(probe_array[i].name);
  89         printk(KERN_INFO "Number of event b : %u\n",
  90                         atomic_read(&eventb_count));
  91 }
  92
  93 module_init(probe_init);
  94 module_exit(probe_fini);
  95
  96 MODULE_LICENSE("GPL");
  97 MODULE_AUTHOR("Mathieu Desnoyers");
  98 MODULE_DESCRIPTION("SUBSYSTEM Probe");