5686c21052f49974c86e86253748b39f8ae8d40b
[lttv.git] / 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 PROBE_NAME subsys_mark1
25
26 #define CALL __mark_subsys_mark1_call
27 #define JUMP_OVER __mark_subsys_mark1_jump_over
28 #define JUMP_CALL __mark_subsys_mark1_jump_call
29 #define JUMP_INLINE __mark_subsys_mark1_jump_inline
30
31 static void *saved_over;
32
33 static void **target_mark_call;
34 static void **target_mark_jump_over;
35 static void **target_mark_jump_call;
36 static void **target_mark_jump_inline;
37
38 void show_symbol_pointers(void)
39 {
40 printk("Marker loader : Loading symbols...\n");
41 printk(" %s %p %p\n", __stringify(CALL), target_mark_call,
42 target_mark_call?*target_mark_call:0x0);
43 printk(" %s %p %p\n", __stringify(JUMP_OVER), target_mark_jump_over,
44 target_mark_jump_over?*target_mark_jump_over:0x0);
45 printk(" %s %p %p\n", __stringify(JUMP_CALL), target_mark_jump_call,
46 target_mark_jump_call?*target_mark_jump_call:0x0);
47 printk(" %s %p %p\n", __stringify(JUMP_INLINE), target_mark_jump_inline,
48 target_mark_jump_inline?*target_mark_jump_inline:0x0);
49 }
50
51 int mark_install_hook(void)
52 {
53 target_mark_call = (void**)kallsyms_lookup_name(__stringify(CALL));
54 target_mark_jump_over = (void**)kallsyms_lookup_name(__stringify(JUMP_OVER));
55 target_mark_jump_call = (void**)kallsyms_lookup_name(__stringify(JUMP_CALL));
56 target_mark_jump_inline = (void**)kallsyms_lookup_name(__stringify(JUMP_INLINE));
57
58 show_symbol_pointers();
59
60 if(!(target_mark_call && target_mark_jump_over && target_mark_jump_call &&
61 target_mark_jump_inline)) {
62 printk("Target symbols missing in kallsyms.\n");
63 return -EPERM;
64 }
65
66 printk("Installing hook\n");
67 *target_mark_call = (void*)do_mark1;
68 saved_over = *target_mark_jump_over;
69 *target_mark_jump_over = *target_mark_jump_call;
70
71 return 0;
72 }
73
74 int init_module(void)
75 {
76 return mark_install_hook();
77 }
78
79 void cleanup_module(void)
80 {
81 printk("Removing hook\n");
82 *target_mark_jump_over = saved_over;
83 *target_mark_call = __mark_empty_function;
84
85 /* Wait for instrumentation functions to return before quitting */
86 synchronize_sched();
87 }
88
89 MODULE_LICENSE("GPL");
90 MODULE_AUTHOR("Mathieu Desnoyers");
91 MODULE_DESCRIPTION("Marker Loader");
92
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