1 /*
2 * Kernel Probes (KProbes)
3 * kernel/kprobes.c
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 *
19 * Copyright (C) IBM Corporation, 2002, 2004
20 *
21 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22 * Probes initial implementation (includes suggestions from
23 * Rusty Russell).
24 * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
25 * hlists and exceptions notifier as suggested by Andi Kleen.
26 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
27 * interface to access function arguments.
28 * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
29 * exceptions notifier to be first on the priority list.
30 */
31 #include <linux/kprobes.h>
32 #include <linux/spinlock.h>
33 #include <linux/hash.h>
34 #include <linux/init.h>
35 #include <linux/module.h>
36 #include <asm/cacheflush.h>
37 #include <asm/errno.h>
38 #include <asm/kdebug.h>
39
40 #define KPROBE_HASH_BITS 6
41 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
42
43 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
44
45 unsigned int kprobe_cpu = NR_CPUS;
46 static DEFINE_SPINLOCK(kprobe_lock);
47
48 /* Locks kprobe: irqs must be disabled */
49 void lock_kprobes(void)
50 {
51 spin_lock(&kprobe_lock);
52 kprobe_cpu = smp_processor_id();
53 }
54
55 void unlock_kprobes(void)
56 {
57 kprobe_cpu = NR_CPUS;
58 spin_unlock(&kprobe_lock);
59 }
60
61 /* You have to be holding the kprobe_lock */
62 struct kprobe *get_kprobe(void *addr)
63 {
64 struct hlist_head *head;
65 struct hlist_node *node;
66
67 head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
68 hlist_for_each(node, head) {
69 struct kprobe *p = hlist_entry(node, struct kprobe, hlist);
70 if (p->addr == addr)
71 return p;
72 }
73 return NULL;
74 }
75
76 int register_kprobe(struct kprobe *p)
77 {
78 int ret = 0;
79 unsigned long flags = 0;
80
81 if ((ret = arch_prepare_kprobe(p)) != 0) {
82 goto out;
83 }
84 spin_lock_irqsave(&kprobe_lock, flags);
85 INIT_HLIST_NODE(&p->hlist);
86 if (get_kprobe(p->addr)) {
87 ret = -EEXIST;
88 goto out;
89 }
90 arch_copy_kprobe(p);
91
92 hlist_add_head(&p->hlist,
93 &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
94
95 p->opcode = *p->addr;
96 *p->addr = BREAKPOINT_INSTRUCTION;
97 flush_icache_range((unsigned long) p->addr,
98 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
99 out:
100 spin_unlock_irqrestore(&kprobe_lock, flags);
101 if (ret == -EEXIST)
102 arch_remove_kprobe(p);
103 return ret;
104 }
105
106 void unregister_kprobe(struct kprobe *p)
107 {
108 unsigned long flags;
109 arch_remove_kprobe(p);
110 spin_lock_irqsave(&kprobe_lock, flags);
111 *p->addr = p->opcode;
112 hlist_del(&p->hlist);
113 flush_icache_range((unsigned long) p->addr,
114 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
115 spin_unlock_irqrestore(&kprobe_lock, flags);
116 }
117
118 static struct notifier_block kprobe_exceptions_nb = {
119 .notifier_call = kprobe_exceptions_notify,
120 .priority = 0x7fffffff /* we need to notified first */
121 };
122
123 int register_jprobe(struct jprobe *jp)
124 {
125 /* Todo: Verify probepoint is a function entry point */
126 jp->kp.pre_handler = setjmp_pre_handler;
127 jp->kp.break_handler = longjmp_break_handler;
128
129 return register_kprobe(&jp->kp);
130 }
131
132 void unregister_jprobe(struct jprobe *jp)
133 {
134 unregister_kprobe(&jp->kp);
135 }
136
137 static int __init init_kprobes(void)
138 {
139 int i, err = 0;
140
141 /* FIXME allocate the probe table, currently defined statically */
142 /* initialize all list heads */
143 for (i = 0; i < KPROBE_TABLE_SIZE; i++)
144 INIT_HLIST_HEAD(&kprobe_table[i]);
145
146 err = register_die_notifier(&kprobe_exceptions_nb);
147 return err;
148 }
149
150 __initcall(init_kprobes);
151
152 EXPORT_SYMBOL_GPL(register_kprobe);
153 EXPORT_SYMBOL_GPL(unregister_kprobe);
154 EXPORT_SYMBOL_GPL(register_jprobe);
155 EXPORT_SYMBOL_GPL(unregister_jprobe);
156 EXPORT_SYMBOL_GPL(jprobe_return);
157
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