tests/kernel/probe-example.c

   1 /* probe-example.c
   2  *
   3  * Connects a 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 #define NUM_PROBES (sizeof(probe_array) / sizeof(struct probe_data))
  18
  19 struct probe_data {
  20         const char *name;
  21         const char *format;
  22         marker_probe_func *probe_func;
  23 };
  24
  25 void probe_subsystem_event(const struct __mark_marker_c *mdata,
  26                 const char *format, ...)
  27 {
  28         va_list ap;
  29         /* Declare args */
  30         unsigned int value;
  31         const char *mystr;
  32
  33         /* Assign args */
  34         va_start(ap, format);
  35         value = va_arg(ap, typeof(value));
  36         mystr = va_arg(ap, typeof(mystr));
  37
  38         /* Call printk */
  39         printk("Value %u, string %s\n", value, mystr);
  40
  41         /* or count, check rights, serialize data in a buffer */
  42
  43         va_end(ap);
  44 }
  45
  46 atomic_t eventb_count = ATOMIC_INIT(0);
  47
  48 void probe_subsystem_eventb(const struct __mark_marker_c *mdata,
  49         const char *format, ...)
  50 {
  51         /* Increment counter */
  52         atomic_inc(&eventb_count);
  53 }
  54
  55 static struct probe_data probe_array[] =
  56 {
  57         {       .name = "subsystem_event",
  58                 .format = "%d %s",
  59                 .probe_func = probe_subsystem_event },
  60         {       .name = "subsystem_eventb",
  61                 .format = MARK_NOARGS,
  62                 .probe_func = probe_subsystem_eventb },
  63 };
  64
  65 static int __init probe_init(void)
  66 {
  67         int result;
  68         uint8_t eID;
  69
  70         for (eID = 0; eID < NUM_PROBES; eID++) {
  71                 result = marker_set_probe(probe_array[eID].name,
  72                                 probe_array[eID].format,
  73                                 probe_array[eID].probe_func, &probe_array[eID]);
  74                 if (!result)
  75                         printk(KERN_INFO "Unable to register probe %s\n",
  76                                 probe_array[eID].name);
  77         }
  78         return 0;
  79 }
  80
  81 static void __exit probe_fini(void)
  82 {
  83         uint8_t eID;
  84
  85         for (eID = 0; eID < NUM_PROBES; eID++) {
  86                 marker_remove_probe(probe_array[eID].name);
  87         }
  88         synchronize_sched();    /* Wait for probes to finish */
  89         printk("Number of event b : %u\n", atomic_read(&eventb_count));
  90 }
  91
  92 module_init(probe_init);
  93 module_exit(probe_fini);
  94
  95 MODULE_LICENSE("GPL");
  96 MODULE_AUTHOR("Mathieu Desnoyers");
  97 MODULE_DESCRIPTION("SUBSYSTEM Probe");