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1da177e4 LT |
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); | |
64f562c6 | 47 | static struct kprobe *curr_kprobe; |
1da177e4 LT |
48 | |
49 | /* Locks kprobe: irqs must be disabled */ | |
50 | void lock_kprobes(void) | |
51 | { | |
52 | spin_lock(&kprobe_lock); | |
53 | kprobe_cpu = smp_processor_id(); | |
54 | } | |
55 | ||
56 | void unlock_kprobes(void) | |
57 | { | |
58 | kprobe_cpu = NR_CPUS; | |
59 | spin_unlock(&kprobe_lock); | |
60 | } | |
61 | ||
62 | /* You have to be holding the kprobe_lock */ | |
63 | struct kprobe *get_kprobe(void *addr) | |
64 | { | |
65 | struct hlist_head *head; | |
66 | struct hlist_node *node; | |
67 | ||
68 | head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; | |
69 | hlist_for_each(node, head) { | |
70 | struct kprobe *p = hlist_entry(node, struct kprobe, hlist); | |
71 | if (p->addr == addr) | |
72 | return p; | |
73 | } | |
74 | return NULL; | |
75 | } | |
76 | ||
64f562c6 AM |
77 | /* |
78 | * Aggregate handlers for multiple kprobes support - these handlers | |
79 | * take care of invoking the individual kprobe handlers on p->list | |
80 | */ | |
81 | int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
82 | { | |
83 | struct kprobe *kp; | |
84 | ||
85 | list_for_each_entry(kp, &p->list, list) { | |
86 | if (kp->pre_handler) { | |
87 | curr_kprobe = kp; | |
88 | kp->pre_handler(kp, regs); | |
89 | curr_kprobe = NULL; | |
90 | } | |
91 | } | |
92 | return 0; | |
93 | } | |
94 | ||
95 | void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, | |
96 | unsigned long flags) | |
97 | { | |
98 | struct kprobe *kp; | |
99 | ||
100 | list_for_each_entry(kp, &p->list, list) { | |
101 | if (kp->post_handler) { | |
102 | curr_kprobe = kp; | |
103 | kp->post_handler(kp, regs, flags); | |
104 | curr_kprobe = NULL; | |
105 | } | |
106 | } | |
107 | return; | |
108 | } | |
109 | ||
110 | int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr) | |
111 | { | |
112 | /* | |
113 | * if we faulted "during" the execution of a user specified | |
114 | * probe handler, invoke just that probe's fault handler | |
115 | */ | |
116 | if (curr_kprobe && curr_kprobe->fault_handler) { | |
117 | if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr)) | |
118 | return 1; | |
119 | } | |
120 | return 0; | |
121 | } | |
122 | ||
123 | /* | |
124 | * Fill in the required fields of the "manager kprobe". Replace the | |
125 | * earlier kprobe in the hlist with the manager kprobe | |
126 | */ | |
127 | static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p) | |
128 | { | |
129 | ap->addr = p->addr; | |
130 | ap->opcode = p->opcode; | |
131 | memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn)); | |
132 | ||
133 | ap->pre_handler = aggr_pre_handler; | |
134 | ap->post_handler = aggr_post_handler; | |
135 | ap->fault_handler = aggr_fault_handler; | |
136 | ||
137 | INIT_LIST_HEAD(&ap->list); | |
138 | list_add(&p->list, &ap->list); | |
139 | ||
140 | INIT_HLIST_NODE(&ap->hlist); | |
141 | hlist_del(&p->hlist); | |
142 | hlist_add_head(&ap->hlist, | |
143 | &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]); | |
144 | } | |
145 | ||
146 | /* | |
147 | * This is the second or subsequent kprobe at the address - handle | |
148 | * the intricacies | |
149 | * TODO: Move kcalloc outside the spinlock | |
150 | */ | |
151 | static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p) | |
152 | { | |
153 | int ret = 0; | |
154 | struct kprobe *ap; | |
155 | ||
156 | if (old_p->break_handler || p->break_handler) { | |
157 | ret = -EEXIST; /* kprobe and jprobe can't (yet) coexist */ | |
158 | } else if (old_p->pre_handler == aggr_pre_handler) { | |
159 | list_add(&p->list, &old_p->list); | |
160 | } else { | |
161 | ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC); | |
162 | if (!ap) | |
163 | return -ENOMEM; | |
164 | add_aggr_kprobe(ap, old_p); | |
165 | list_add(&p->list, &ap->list); | |
166 | } | |
167 | return ret; | |
168 | } | |
169 | ||
170 | /* kprobe removal house-keeping routines */ | |
171 | static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags) | |
172 | { | |
173 | *p->addr = p->opcode; | |
174 | hlist_del(&p->hlist); | |
175 | flush_icache_range((unsigned long) p->addr, | |
176 | (unsigned long) p->addr + sizeof(kprobe_opcode_t)); | |
177 | spin_unlock_irqrestore(&kprobe_lock, flags); | |
178 | arch_remove_kprobe(p); | |
179 | } | |
180 | ||
181 | static inline void cleanup_aggr_kprobe(struct kprobe *old_p, | |
182 | struct kprobe *p, unsigned long flags) | |
183 | { | |
184 | list_del(&p->list); | |
185 | if (list_empty(&old_p->list)) { | |
186 | cleanup_kprobe(old_p, flags); | |
187 | kfree(old_p); | |
188 | } else | |
189 | spin_unlock_irqrestore(&kprobe_lock, flags); | |
190 | } | |
191 | ||
1da177e4 LT |
192 | int register_kprobe(struct kprobe *p) |
193 | { | |
194 | int ret = 0; | |
195 | unsigned long flags = 0; | |
64f562c6 | 196 | struct kprobe *old_p; |
1da177e4 LT |
197 | |
198 | if ((ret = arch_prepare_kprobe(p)) != 0) { | |
199 | goto rm_kprobe; | |
200 | } | |
201 | spin_lock_irqsave(&kprobe_lock, flags); | |
64f562c6 AM |
202 | old_p = get_kprobe(p->addr); |
203 | if (old_p) { | |
204 | ret = register_aggr_kprobe(old_p, p); | |
1da177e4 LT |
205 | goto out; |
206 | } | |
1da177e4 | 207 | |
64f562c6 AM |
208 | arch_copy_kprobe(p); |
209 | INIT_HLIST_NODE(&p->hlist); | |
1da177e4 LT |
210 | hlist_add_head(&p->hlist, |
211 | &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); | |
212 | ||
213 | p->opcode = *p->addr; | |
214 | *p->addr = BREAKPOINT_INSTRUCTION; | |
215 | flush_icache_range((unsigned long) p->addr, | |
216 | (unsigned long) p->addr + sizeof(kprobe_opcode_t)); | |
217 | out: | |
218 | spin_unlock_irqrestore(&kprobe_lock, flags); | |
219 | rm_kprobe: | |
220 | if (ret == -EEXIST) | |
221 | arch_remove_kprobe(p); | |
222 | return ret; | |
223 | } | |
224 | ||
225 | void unregister_kprobe(struct kprobe *p) | |
226 | { | |
227 | unsigned long flags; | |
64f562c6 AM |
228 | struct kprobe *old_p; |
229 | ||
1da177e4 | 230 | spin_lock_irqsave(&kprobe_lock, flags); |
64f562c6 AM |
231 | old_p = get_kprobe(p->addr); |
232 | if (old_p) { | |
233 | if (old_p->pre_handler == aggr_pre_handler) | |
234 | cleanup_aggr_kprobe(old_p, p, flags); | |
235 | else | |
236 | cleanup_kprobe(p, flags); | |
237 | } else | |
04dea5f9 | 238 | spin_unlock_irqrestore(&kprobe_lock, flags); |
1da177e4 LT |
239 | } |
240 | ||
241 | static struct notifier_block kprobe_exceptions_nb = { | |
242 | .notifier_call = kprobe_exceptions_notify, | |
243 | .priority = 0x7fffffff /* we need to notified first */ | |
244 | }; | |
245 | ||
246 | int register_jprobe(struct jprobe *jp) | |
247 | { | |
248 | /* Todo: Verify probepoint is a function entry point */ | |
249 | jp->kp.pre_handler = setjmp_pre_handler; | |
250 | jp->kp.break_handler = longjmp_break_handler; | |
251 | ||
252 | return register_kprobe(&jp->kp); | |
253 | } | |
254 | ||
255 | void unregister_jprobe(struct jprobe *jp) | |
256 | { | |
257 | unregister_kprobe(&jp->kp); | |
258 | } | |
259 | ||
260 | static int __init init_kprobes(void) | |
261 | { | |
262 | int i, err = 0; | |
263 | ||
264 | /* FIXME allocate the probe table, currently defined statically */ | |
265 | /* initialize all list heads */ | |
266 | for (i = 0; i < KPROBE_TABLE_SIZE; i++) | |
267 | INIT_HLIST_HEAD(&kprobe_table[i]); | |
268 | ||
269 | err = register_die_notifier(&kprobe_exceptions_nb); | |
270 | return err; | |
271 | } | |
272 | ||
273 | __initcall(init_kprobes); | |
274 | ||
275 | EXPORT_SYMBOL_GPL(register_kprobe); | |
276 | EXPORT_SYMBOL_GPL(unregister_kprobe); | |
277 | EXPORT_SYMBOL_GPL(register_jprobe); | |
278 | EXPORT_SYMBOL_GPL(unregister_jprobe); | |
279 | EXPORT_SYMBOL_GPL(jprobe_return); |