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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 | |
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23 | static void *saved_over; |
24 | |
25 | static void **target_mark_call; |
26 | static void **target_mark_jump_over; |
27 | static void **target_mark_jump_call; |
28 | static void **target_mark_jump_inline; |
29 | |
30 | void show_symbol_pointers(void) |
31 | { |
32 | printk("Marker loader : Loading symbols...\n"); |
33 | printk(" %s %p %p\n", __stringify(CALL), target_mark_call, |
34 | target_mark_call?*target_mark_call:0x0); |
35 | printk(" %s %p %p\n", __stringify(JUMP_OVER), target_mark_jump_over, |
36 | target_mark_jump_over?*target_mark_jump_over:0x0); |
37 | printk(" %s %p %p\n", __stringify(JUMP_CALL), target_mark_jump_call, |
38 | target_mark_jump_call?*target_mark_jump_call:0x0); |
39 | printk(" %s %p %p\n", __stringify(JUMP_INLINE), target_mark_jump_inline, |
40 | target_mark_jump_inline?*target_mark_jump_inline:0x0); |
41 | } |
42 | |
43 | int mark_install_hook(void) |
44 | { |
45 | target_mark_call = (void**)kallsyms_lookup_name(__stringify(CALL)); |
46 | target_mark_jump_over = (void**)kallsyms_lookup_name(__stringify(JUMP_OVER)); |
47 | target_mark_jump_call = (void**)kallsyms_lookup_name(__stringify(JUMP_CALL)); |
48 | target_mark_jump_inline = (void**)kallsyms_lookup_name(__stringify(JUMP_INLINE)); |
49 | |
50 | show_symbol_pointers(); |
51 | |
52 | if(!(target_mark_call && target_mark_jump_over && target_mark_jump_call && |
53 | target_mark_jump_inline)) { |
54 | printk("Target symbols missing in kallsyms.\n"); |
55 | return -EPERM; |
56 | } |
57 | |
58 | printk("Installing hook\n"); |
59 | *target_mark_call = (void*)do_mark1; |
60 | saved_over = *target_mark_jump_over; |
61 | *target_mark_jump_over = *target_mark_jump_call; |
62 | |
63 | return 0; |
64 | } |
65 | |
66 | int init_module(void) |
67 | { |
68 | return mark_install_hook(); |
69 | } |
70 | |
71 | void cleanup_module(void) |
72 | { |
73 | printk("Removing hook\n"); |
74 | *target_mark_jump_over = saved_over; |
75 | *target_mark_call = __mark_empty_function; |
76 | |
77 | /* Wait for instrumentation functions to return before quitting */ |
78 | synchronize_sched(); |
79 | } |
80 | |
81 | MODULE_LICENSE("GPL"); |
82 | MODULE_AUTHOR("Mathieu Desnoyers"); |
83 | MODULE_DESCRIPTION("Marker Loader"); |
84 | |