marker-loader/marker-loader.c

   1 /* marker-loader.c
   2  *
   3  * Marker Loader
   4  *
   5  * Loads a function at a marker call site.
   6  *
   7  * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
   8  *
   9  * This file is released under the GPLv2.
  10  * See the file COPYING for more details.
  11  */
  12
  13 #include <linux/marker.h>
  14 #include <linux/module.h>
  15 #include <linux/kallsyms.h>
  16
  17 /* function to install */
  18 void do_mark1(const char *format, int value)
  19 {
  20         printk("value is %d\n", value);
  21 }
  22
  23
  24 //#define CALL __mark_subsys_mark1_call
  25 //#define JUMP_OVER __mark_subsys_mark1_jump_over
  26 //#define JUMP_CALL __mark_subsys_mark1_jump_call
  27 //#define JUMP_INLINE __mark_subsys_mark1_jump_inline
  28
  29 static void *saved_over;
  30
  31 static void **target_mark_call;
  32 static void **target_mark_jump_over;
  33 static void **target_mark_jump_call;
  34 static void **target_mark_jump_inline;
  35
  36 void show_symbol_pointers(void)
  37 {
  38         printk("Marker loader : Loading symbols...\n");
  39         printk("  %s %p %p\n", __stringify(CALL), target_mark_call,
  40                 target_mark_call?*target_mark_call:0x0);
  41         printk("  %s %p %p\n", __stringify(JUMP_OVER), target_mark_jump_over,
  42                 target_mark_jump_over?*target_mark_jump_over:0x0);
  43         printk("  %s %p %p\n", __stringify(JUMP_CALL), target_mark_jump_call,
  44                 target_mark_jump_call?*target_mark_jump_call:0x0);
  45         printk("  %s %p %p\n", __stringify(JUMP_INLINE), target_mark_jump_inline,
  46                 target_mark_jump_inline?*target_mark_jump_inline:0x0);
  47 }
  48
  49 int mark_install_hook(void)
  50 {
  51         target_mark_call = (void**)kallsyms_lookup_name(__stringify(CALL));
  52         target_mark_jump_over = (void**)kallsyms_lookup_name(__stringify(JUMP_OVER));
  53         target_mark_jump_call = (void**)kallsyms_lookup_name(__stringify(JUMP_CALL));
  54         target_mark_jump_inline = (void**)kallsyms_lookup_name(__stringify(JUMP_INLINE));
  55
  56         show_symbol_pointers();
  57
  58         if(!(target_mark_call && target_mark_jump_over && target_mark_jump_call &&
  59                 target_mark_jump_inline)) {
  60                 printk("Target symbols missing in kallsyms.\n");
  61                 return -EPERM;
  62         }
  63
  64         printk("Installing hook\n");
  65         *target_mark_call = (void*)do_mark1;
  66         saved_over = *target_mark_jump_over;
  67         *target_mark_jump_over = *target_mark_jump_call;
  68
  69         return 0;
  70 }
  71
  72 int init_module(void)
  73 {
  74         return mark_install_hook();
  75 }
  76
  77 void cleanup_module(void)
  78 {
  79         printk("Removing hook\n");
  80         *target_mark_jump_over = saved_over;
  81         *target_mark_call = __mark_empty_function;
  82
  83         /* Wait for instrumentation functions to return before quitting */
  84         synchronize_sched();
  85 }
  86
  87 MODULE_LICENSE("GPL");
  88 MODULE_AUTHOR("Mathieu Desnoyers");
  89 MODULE_DESCRIPTION("Marker Loader");
  90