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         int task_size, task_alignment;
  33         struct task_struct *task;
  34
  35         /* Assign args */
  36         va_start(ap, format);
  37         value = va_arg(ap, typeof(value));
  38         mystr = va_arg(ap, typeof(mystr));
  39         task_size = va_arg(ap, typeof(task_size));
  40         task_alignment = va_arg(ap, typeof(task_alignment));
  41         task = va_arg(ap, typeof(task));
  42
  43         /* Call printk */
  44         printk("Value %u, string %s, current ptr %p\n", value, mystr, current);
  45
  46         /* or count, check rights, serialize data in a buffer */
  47
  48         va_end(ap);
  49 }
  50
  51 atomic_t eventb_count = ATOMIC_INIT(0);
  52
  53 void probe_subsystem_eventb(const struct __mark_marker_c *mdata,
  54         const char *format, ...)
  55 {
  56         /* Increment counter */
  57         atomic_inc(&eventb_count);
  58 }
  59
  60 static struct probe_data probe_array[] =
  61 {
  62         {       .name = "subsystem_event",
  63                 .format = "%d %s %*.*r",
  64                 .probe_func = probe_subsystem_event },
  65         {       .name = "subsystem_eventb",
  66                 .format = MARK_NOARGS,
  67                 .probe_func = probe_subsystem_eventb },
  68 };
  69
  70 static int __init probe_init(void)
  71 {
  72         int result;
  73         uint8_t eID;
  74
  75         for (eID = 0; eID < NUM_PROBES; eID++) {
  76                 result = marker_set_probe(probe_array[eID].name,
  77                                 probe_array[eID].format,
  78                                 probe_array[eID].probe_func, &probe_array[eID]);
  79                 if (!result)
  80                         printk(KERN_INFO "Unable to register probe %s\n",
  81                                 probe_array[eID].name);
  82         }
  83         return 0;
  84 }
  85
  86 static void __exit probe_fini(void)
  87 {
  88         uint8_t eID;
  89
  90         for (eID = 0; eID < NUM_PROBES; eID++) {
  91                 marker_remove_probe(probe_array[eID].name);
  92         }
  93         synchronize_sched();    /* Wait for probes to finish */
  94         printk("Number of event b : %u\n", atomic_read(&eventb_count));
  95 }
  96
  97 module_init(probe_init);
  98 module_exit(probe_fini);
  99
 100 MODULE_LICENSE("GPL");
 101 MODULE_AUTHOR("Mathieu Desnoyers");
 102 MODULE_DESCRIPTION("SUBSYSTEM Probe");