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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 | * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston | |
31 | * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi | |
32 | * <prasanna@in.ibm.com> added function-return probes. | |
33 | */ | |
34 | #include <linux/kprobes.h> | |
35 | #include <linux/hash.h> | |
36 | #include <linux/init.h> | |
37 | #include <linux/slab.h> | |
38 | #include <linux/stddef.h> | |
39 | #include <linux/module.h> | |
40 | #include <linux/moduleloader.h> | |
41 | #include <linux/kallsyms.h> | |
42 | #include <linux/freezer.h> | |
43 | #include <linux/seq_file.h> | |
44 | #include <linux/debugfs.h> | |
45 | #include <linux/kdebug.h> | |
46 | ||
47 | #include <asm-generic/sections.h> | |
48 | #include <asm/cacheflush.h> | |
49 | #include <asm/errno.h> | |
50 | #include <asm/uaccess.h> | |
51 | ||
52 | #define KPROBE_HASH_BITS 6 | |
53 | #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) | |
54 | ||
55 | ||
56 | /* | |
57 | * Some oddball architectures like 64bit powerpc have function descriptors | |
58 | * so this must be overridable. | |
59 | */ | |
60 | #ifndef kprobe_lookup_name | |
61 | #define kprobe_lookup_name(name, addr) \ | |
62 | addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name))) | |
63 | #endif | |
64 | ||
65 | static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE]; | |
66 | static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE]; | |
67 | static atomic_t kprobe_count; | |
68 | ||
69 | /* NOTE: change this value only with kprobe_mutex held */ | |
70 | static bool kprobe_enabled; | |
71 | ||
72 | DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */ | |
73 | DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */ | |
74 | static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL; | |
75 | ||
76 | static struct notifier_block kprobe_page_fault_nb = { | |
77 | .notifier_call = kprobe_exceptions_notify, | |
78 | .priority = 0x7fffffff /* we need to notified first */ | |
79 | }; | |
80 | ||
81 | #ifdef __ARCH_WANT_KPROBES_INSN_SLOT | |
82 | /* | |
83 | * kprobe->ainsn.insn points to the copy of the instruction to be | |
84 | * single-stepped. x86_64, POWER4 and above have no-exec support and | |
85 | * stepping on the instruction on a vmalloced/kmalloced/data page | |
86 | * is a recipe for disaster | |
87 | */ | |
88 | #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t))) | |
89 | ||
90 | struct kprobe_insn_page { | |
91 | struct hlist_node hlist; | |
92 | kprobe_opcode_t *insns; /* Page of instruction slots */ | |
93 | char slot_used[INSNS_PER_PAGE]; | |
94 | int nused; | |
95 | int ngarbage; | |
96 | }; | |
97 | ||
98 | enum kprobe_slot_state { | |
99 | SLOT_CLEAN = 0, | |
100 | SLOT_DIRTY = 1, | |
101 | SLOT_USED = 2, | |
102 | }; | |
103 | ||
104 | static struct hlist_head kprobe_insn_pages; | |
105 | static int kprobe_garbage_slots; | |
106 | static int collect_garbage_slots(void); | |
107 | ||
108 | static int __kprobes check_safety(void) | |
109 | { | |
110 | int ret = 0; | |
111 | #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM) | |
112 | ret = freeze_processes(); | |
113 | if (ret == 0) { | |
114 | struct task_struct *p, *q; | |
115 | do_each_thread(p, q) { | |
116 | if (p != current && p->state == TASK_RUNNING && | |
117 | p->pid != 0) { | |
118 | printk("Check failed: %s is running\n",p->comm); | |
119 | ret = -1; | |
120 | goto loop_end; | |
121 | } | |
122 | } while_each_thread(p, q); | |
123 | } | |
124 | loop_end: | |
125 | thaw_processes(); | |
126 | #else | |
127 | synchronize_sched(); | |
128 | #endif | |
129 | return ret; | |
130 | } | |
131 | ||
132 | /** | |
133 | * get_insn_slot() - Find a slot on an executable page for an instruction. | |
134 | * We allocate an executable page if there's no room on existing ones. | |
135 | */ | |
136 | kprobe_opcode_t __kprobes *get_insn_slot(void) | |
137 | { | |
138 | struct kprobe_insn_page *kip; | |
139 | struct hlist_node *pos; | |
140 | ||
141 | retry: | |
142 | hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) { | |
143 | if (kip->nused < INSNS_PER_PAGE) { | |
144 | int i; | |
145 | for (i = 0; i < INSNS_PER_PAGE; i++) { | |
146 | if (kip->slot_used[i] == SLOT_CLEAN) { | |
147 | kip->slot_used[i] = SLOT_USED; | |
148 | kip->nused++; | |
149 | return kip->insns + (i * MAX_INSN_SIZE); | |
150 | } | |
151 | } | |
152 | /* Surprise! No unused slots. Fix kip->nused. */ | |
153 | kip->nused = INSNS_PER_PAGE; | |
154 | } | |
155 | } | |
156 | ||
157 | /* If there are any garbage slots, collect it and try again. */ | |
158 | if (kprobe_garbage_slots && collect_garbage_slots() == 0) { | |
159 | goto retry; | |
160 | } | |
161 | /* All out of space. Need to allocate a new page. Use slot 0. */ | |
162 | kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); | |
163 | if (!kip) | |
164 | return NULL; | |
165 | ||
166 | /* | |
167 | * Use module_alloc so this page is within +/- 2GB of where the | |
168 | * kernel image and loaded module images reside. This is required | |
169 | * so x86_64 can correctly handle the %rip-relative fixups. | |
170 | */ | |
171 | kip->insns = module_alloc(PAGE_SIZE); | |
172 | if (!kip->insns) { | |
173 | kfree(kip); | |
174 | return NULL; | |
175 | } | |
176 | INIT_HLIST_NODE(&kip->hlist); | |
177 | hlist_add_head(&kip->hlist, &kprobe_insn_pages); | |
178 | memset(kip->slot_used, SLOT_CLEAN, INSNS_PER_PAGE); | |
179 | kip->slot_used[0] = SLOT_USED; | |
180 | kip->nused = 1; | |
181 | kip->ngarbage = 0; | |
182 | return kip->insns; | |
183 | } | |
184 | ||
185 | /* Return 1 if all garbages are collected, otherwise 0. */ | |
186 | static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx) | |
187 | { | |
188 | kip->slot_used[idx] = SLOT_CLEAN; | |
189 | kip->nused--; | |
190 | if (kip->nused == 0) { | |
191 | /* | |
192 | * Page is no longer in use. Free it unless | |
193 | * it's the last one. We keep the last one | |
194 | * so as not to have to set it up again the | |
195 | * next time somebody inserts a probe. | |
196 | */ | |
197 | hlist_del(&kip->hlist); | |
198 | if (hlist_empty(&kprobe_insn_pages)) { | |
199 | INIT_HLIST_NODE(&kip->hlist); | |
200 | hlist_add_head(&kip->hlist, | |
201 | &kprobe_insn_pages); | |
202 | } else { | |
203 | module_free(NULL, kip->insns); | |
204 | kfree(kip); | |
205 | } | |
206 | return 1; | |
207 | } | |
208 | return 0; | |
209 | } | |
210 | ||
211 | static int __kprobes collect_garbage_slots(void) | |
212 | { | |
213 | struct kprobe_insn_page *kip; | |
214 | struct hlist_node *pos, *next; | |
215 | ||
216 | /* Ensure no-one is preepmted on the garbages */ | |
217 | if (check_safety() != 0) | |
218 | return -EAGAIN; | |
219 | ||
220 | hlist_for_each_entry_safe(kip, pos, next, &kprobe_insn_pages, hlist) { | |
221 | int i; | |
222 | if (kip->ngarbage == 0) | |
223 | continue; | |
224 | kip->ngarbage = 0; /* we will collect all garbages */ | |
225 | for (i = 0; i < INSNS_PER_PAGE; i++) { | |
226 | if (kip->slot_used[i] == SLOT_DIRTY && | |
227 | collect_one_slot(kip, i)) | |
228 | break; | |
229 | } | |
230 | } | |
231 | kprobe_garbage_slots = 0; | |
232 | return 0; | |
233 | } | |
234 | ||
235 | void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty) | |
236 | { | |
237 | struct kprobe_insn_page *kip; | |
238 | struct hlist_node *pos; | |
239 | ||
240 | hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) { | |
241 | if (kip->insns <= slot && | |
242 | slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) { | |
243 | int i = (slot - kip->insns) / MAX_INSN_SIZE; | |
244 | if (dirty) { | |
245 | kip->slot_used[i] = SLOT_DIRTY; | |
246 | kip->ngarbage++; | |
247 | } else { | |
248 | collect_one_slot(kip, i); | |
249 | } | |
250 | break; | |
251 | } | |
252 | } | |
253 | ||
254 | if (dirty && ++kprobe_garbage_slots > INSNS_PER_PAGE) | |
255 | collect_garbage_slots(); | |
256 | } | |
257 | #endif | |
258 | ||
259 | /* We have preemption disabled.. so it is safe to use __ versions */ | |
260 | static inline void set_kprobe_instance(struct kprobe *kp) | |
261 | { | |
262 | __get_cpu_var(kprobe_instance) = kp; | |
263 | } | |
264 | ||
265 | static inline void reset_kprobe_instance(void) | |
266 | { | |
267 | __get_cpu_var(kprobe_instance) = NULL; | |
268 | } | |
269 | ||
270 | /* | |
271 | * This routine is called either: | |
272 | * - under the kprobe_mutex - during kprobe_[un]register() | |
273 | * OR | |
274 | * - with preemption disabled - from arch/xxx/kernel/kprobes.c | |
275 | */ | |
276 | struct kprobe __kprobes *get_kprobe(void *addr) | |
277 | { | |
278 | struct hlist_head *head; | |
279 | struct hlist_node *node; | |
280 | struct kprobe *p; | |
281 | ||
282 | head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; | |
283 | hlist_for_each_entry_rcu(p, node, head, hlist) { | |
284 | if (p->addr == addr) | |
285 | return p; | |
286 | } | |
287 | return NULL; | |
288 | } | |
289 | ||
290 | /* | |
291 | * Aggregate handlers for multiple kprobes support - these handlers | |
292 | * take care of invoking the individual kprobe handlers on p->list | |
293 | */ | |
294 | static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
295 | { | |
296 | struct kprobe *kp; | |
297 | ||
298 | list_for_each_entry_rcu(kp, &p->list, list) { | |
299 | if (kp->pre_handler) { | |
300 | set_kprobe_instance(kp); | |
301 | if (kp->pre_handler(kp, regs)) | |
302 | return 1; | |
303 | } | |
304 | reset_kprobe_instance(); | |
305 | } | |
306 | return 0; | |
307 | } | |
308 | ||
309 | static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs, | |
310 | unsigned long flags) | |
311 | { | |
312 | struct kprobe *kp; | |
313 | ||
314 | list_for_each_entry_rcu(kp, &p->list, list) { | |
315 | if (kp->post_handler) { | |
316 | set_kprobe_instance(kp); | |
317 | kp->post_handler(kp, regs, flags); | |
318 | reset_kprobe_instance(); | |
319 | } | |
320 | } | |
321 | } | |
322 | ||
323 | static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, | |
324 | int trapnr) | |
325 | { | |
326 | struct kprobe *cur = __get_cpu_var(kprobe_instance); | |
327 | ||
328 | /* | |
329 | * if we faulted "during" the execution of a user specified | |
330 | * probe handler, invoke just that probe's fault handler | |
331 | */ | |
332 | if (cur && cur->fault_handler) { | |
333 | if (cur->fault_handler(cur, regs, trapnr)) | |
334 | return 1; | |
335 | } | |
336 | return 0; | |
337 | } | |
338 | ||
339 | static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs) | |
340 | { | |
341 | struct kprobe *cur = __get_cpu_var(kprobe_instance); | |
342 | int ret = 0; | |
343 | ||
344 | if (cur && cur->break_handler) { | |
345 | if (cur->break_handler(cur, regs)) | |
346 | ret = 1; | |
347 | } | |
348 | reset_kprobe_instance(); | |
349 | return ret; | |
350 | } | |
351 | ||
352 | /* Walks the list and increments nmissed count for multiprobe case */ | |
353 | void __kprobes kprobes_inc_nmissed_count(struct kprobe *p) | |
354 | { | |
355 | struct kprobe *kp; | |
356 | if (p->pre_handler != aggr_pre_handler) { | |
357 | p->nmissed++; | |
358 | } else { | |
359 | list_for_each_entry_rcu(kp, &p->list, list) | |
360 | kp->nmissed++; | |
361 | } | |
362 | return; | |
363 | } | |
364 | ||
365 | /* Called with kretprobe_lock held */ | |
366 | void __kprobes recycle_rp_inst(struct kretprobe_instance *ri, | |
367 | struct hlist_head *head) | |
368 | { | |
369 | /* remove rp inst off the rprobe_inst_table */ | |
370 | hlist_del(&ri->hlist); | |
371 | if (ri->rp) { | |
372 | /* remove rp inst off the used list */ | |
373 | hlist_del(&ri->uflist); | |
374 | /* put rp inst back onto the free list */ | |
375 | INIT_HLIST_NODE(&ri->uflist); | |
376 | hlist_add_head(&ri->uflist, &ri->rp->free_instances); | |
377 | } else | |
378 | /* Unregistering */ | |
379 | hlist_add_head(&ri->hlist, head); | |
380 | } | |
381 | ||
382 | struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk) | |
383 | { | |
384 | return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)]; | |
385 | } | |
386 | ||
387 | /* | |
388 | * This function is called from finish_task_switch when task tk becomes dead, | |
389 | * so that we can recycle any function-return probe instances associated | |
390 | * with this task. These left over instances represent probed functions | |
391 | * that have been called but will never return. | |
392 | */ | |
393 | void __kprobes kprobe_flush_task(struct task_struct *tk) | |
394 | { | |
395 | struct kretprobe_instance *ri; | |
396 | struct hlist_head *head, empty_rp; | |
397 | struct hlist_node *node, *tmp; | |
398 | unsigned long flags = 0; | |
399 | ||
400 | INIT_HLIST_HEAD(&empty_rp); | |
401 | spin_lock_irqsave(&kretprobe_lock, flags); | |
402 | head = kretprobe_inst_table_head(tk); | |
403 | hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { | |
404 | if (ri->task == tk) | |
405 | recycle_rp_inst(ri, &empty_rp); | |
406 | } | |
407 | spin_unlock_irqrestore(&kretprobe_lock, flags); | |
408 | ||
409 | hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { | |
410 | hlist_del(&ri->hlist); | |
411 | kfree(ri); | |
412 | } | |
413 | } | |
414 | ||
415 | static inline void free_rp_inst(struct kretprobe *rp) | |
416 | { | |
417 | struct kretprobe_instance *ri; | |
418 | struct hlist_node *pos, *next; | |
419 | ||
420 | hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, uflist) { | |
421 | hlist_del(&ri->uflist); | |
422 | kfree(ri); | |
423 | } | |
424 | } | |
425 | ||
426 | /* | |
427 | * Keep all fields in the kprobe consistent | |
428 | */ | |
429 | static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p) | |
430 | { | |
431 | memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t)); | |
432 | memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn)); | |
433 | } | |
434 | ||
435 | /* | |
436 | * Add the new probe to old_p->list. Fail if this is the | |
437 | * second jprobe at the address - two jprobes can't coexist | |
438 | */ | |
439 | static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p) | |
440 | { | |
441 | if (p->break_handler) { | |
442 | if (old_p->break_handler) | |
443 | return -EEXIST; | |
444 | list_add_tail_rcu(&p->list, &old_p->list); | |
445 | old_p->break_handler = aggr_break_handler; | |
446 | } else | |
447 | list_add_rcu(&p->list, &old_p->list); | |
448 | if (p->post_handler && !old_p->post_handler) | |
449 | old_p->post_handler = aggr_post_handler; | |
450 | return 0; | |
451 | } | |
452 | ||
453 | /* | |
454 | * Fill in the required fields of the "manager kprobe". Replace the | |
455 | * earlier kprobe in the hlist with the manager kprobe | |
456 | */ | |
457 | static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p) | |
458 | { | |
459 | copy_kprobe(p, ap); | |
460 | flush_insn_slot(ap); | |
461 | ap->addr = p->addr; | |
462 | ap->pre_handler = aggr_pre_handler; | |
463 | ap->fault_handler = aggr_fault_handler; | |
464 | if (p->post_handler) | |
465 | ap->post_handler = aggr_post_handler; | |
466 | if (p->break_handler) | |
467 | ap->break_handler = aggr_break_handler; | |
468 | ||
469 | INIT_LIST_HEAD(&ap->list); | |
470 | list_add_rcu(&p->list, &ap->list); | |
471 | ||
472 | hlist_replace_rcu(&p->hlist, &ap->hlist); | |
473 | } | |
474 | ||
475 | /* | |
476 | * This is the second or subsequent kprobe at the address - handle | |
477 | * the intricacies | |
478 | */ | |
479 | static int __kprobes register_aggr_kprobe(struct kprobe *old_p, | |
480 | struct kprobe *p) | |
481 | { | |
482 | int ret = 0; | |
483 | struct kprobe *ap; | |
484 | ||
485 | if (old_p->pre_handler == aggr_pre_handler) { | |
486 | copy_kprobe(old_p, p); | |
487 | ret = add_new_kprobe(old_p, p); | |
488 | } else { | |
489 | ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL); | |
490 | if (!ap) | |
491 | return -ENOMEM; | |
492 | add_aggr_kprobe(ap, old_p); | |
493 | copy_kprobe(ap, p); | |
494 | ret = add_new_kprobe(ap, p); | |
495 | } | |
496 | return ret; | |
497 | } | |
498 | ||
499 | static int __kprobes in_kprobes_functions(unsigned long addr) | |
500 | { | |
501 | if (addr >= (unsigned long)__kprobes_text_start && | |
502 | addr < (unsigned long)__kprobes_text_end) | |
503 | return -EINVAL; | |
504 | return 0; | |
505 | } | |
506 | ||
507 | static int __kprobes __register_kprobe(struct kprobe *p, | |
508 | unsigned long called_from) | |
509 | { | |
510 | int ret = 0; | |
511 | struct kprobe *old_p; | |
512 | struct module *probed_mod; | |
513 | ||
514 | /* | |
515 | * If we have a symbol_name argument look it up, | |
516 | * and add it to the address. That way the addr | |
517 | * field can either be global or relative to a symbol. | |
518 | */ | |
519 | if (p->symbol_name) { | |
520 | if (p->addr) | |
521 | return -EINVAL; | |
522 | kprobe_lookup_name(p->symbol_name, p->addr); | |
523 | } | |
524 | ||
525 | if (!p->addr) | |
526 | return -EINVAL; | |
527 | p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset); | |
528 | ||
529 | if (!kernel_text_address((unsigned long) p->addr) || | |
530 | in_kprobes_functions((unsigned long) p->addr)) | |
531 | return -EINVAL; | |
532 | ||
533 | p->mod_refcounted = 0; | |
534 | ||
535 | /* | |
536 | * Check if are we probing a module. | |
537 | */ | |
538 | probed_mod = module_text_address((unsigned long) p->addr); | |
539 | if (probed_mod) { | |
540 | struct module *calling_mod = module_text_address(called_from); | |
541 | /* | |
542 | * We must allow modules to probe themself and in this case | |
543 | * avoid incrementing the module refcount, so as to allow | |
544 | * unloading of self probing modules. | |
545 | */ | |
546 | if (calling_mod && calling_mod != probed_mod) { | |
547 | if (unlikely(!try_module_get(probed_mod))) | |
548 | return -EINVAL; | |
549 | p->mod_refcounted = 1; | |
550 | } else | |
551 | probed_mod = NULL; | |
552 | } | |
553 | ||
554 | p->nmissed = 0; | |
555 | mutex_lock(&kprobe_mutex); | |
556 | old_p = get_kprobe(p->addr); | |
557 | if (old_p) { | |
558 | ret = register_aggr_kprobe(old_p, p); | |
559 | if (!ret) | |
560 | atomic_inc(&kprobe_count); | |
561 | goto out; | |
562 | } | |
563 | ||
564 | ret = arch_prepare_kprobe(p); | |
565 | if (ret) | |
566 | goto out; | |
567 | ||
568 | INIT_HLIST_NODE(&p->hlist); | |
569 | hlist_add_head_rcu(&p->hlist, | |
570 | &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); | |
571 | ||
572 | if (kprobe_enabled) { | |
573 | if (atomic_add_return(1, &kprobe_count) == \ | |
574 | (ARCH_INACTIVE_KPROBE_COUNT + 1)) | |
575 | register_page_fault_notifier(&kprobe_page_fault_nb); | |
576 | ||
577 | arch_arm_kprobe(p); | |
578 | } | |
579 | out: | |
580 | mutex_unlock(&kprobe_mutex); | |
581 | ||
582 | if (ret && probed_mod) | |
583 | module_put(probed_mod); | |
584 | return ret; | |
585 | } | |
586 | ||
587 | int __kprobes register_kprobe(struct kprobe *p) | |
588 | { | |
589 | return __register_kprobe(p, (unsigned long)__builtin_return_address(0)); | |
590 | } | |
591 | ||
592 | void __kprobes unregister_kprobe(struct kprobe *p) | |
593 | { | |
594 | struct module *mod; | |
595 | struct kprobe *old_p, *list_p; | |
596 | int cleanup_p; | |
597 | ||
598 | mutex_lock(&kprobe_mutex); | |
599 | old_p = get_kprobe(p->addr); | |
600 | if (unlikely(!old_p)) { | |
601 | mutex_unlock(&kprobe_mutex); | |
602 | return; | |
603 | } | |
604 | if (p != old_p) { | |
605 | list_for_each_entry_rcu(list_p, &old_p->list, list) | |
606 | if (list_p == p) | |
607 | /* kprobe p is a valid probe */ | |
608 | goto valid_p; | |
609 | mutex_unlock(&kprobe_mutex); | |
610 | return; | |
611 | } | |
612 | valid_p: | |
613 | if (old_p == p || | |
614 | (old_p->pre_handler == aggr_pre_handler && | |
615 | p->list.next == &old_p->list && p->list.prev == &old_p->list)) { | |
616 | /* | |
617 | * Only probe on the hash list. Disarm only if kprobes are | |
618 | * enabled - otherwise, the breakpoint would already have | |
619 | * been removed. We save on flushing icache. | |
620 | */ | |
621 | if (kprobe_enabled) | |
622 | arch_disarm_kprobe(p); | |
623 | hlist_del_rcu(&old_p->hlist); | |
624 | cleanup_p = 1; | |
625 | } else { | |
626 | list_del_rcu(&p->list); | |
627 | cleanup_p = 0; | |
628 | } | |
629 | ||
630 | mutex_unlock(&kprobe_mutex); | |
631 | ||
632 | synchronize_sched(); | |
633 | if (p->mod_refcounted) { | |
634 | mod = module_text_address((unsigned long)p->addr); | |
635 | if (mod) | |
636 | module_put(mod); | |
637 | } | |
638 | ||
639 | if (cleanup_p) { | |
640 | if (p != old_p) { | |
641 | list_del_rcu(&p->list); | |
642 | kfree(old_p); | |
643 | } | |
644 | arch_remove_kprobe(p); | |
645 | } else { | |
646 | mutex_lock(&kprobe_mutex); | |
647 | if (p->break_handler) | |
648 | old_p->break_handler = NULL; | |
649 | if (p->post_handler){ | |
650 | list_for_each_entry_rcu(list_p, &old_p->list, list){ | |
651 | if (list_p->post_handler){ | |
652 | cleanup_p = 2; | |
653 | break; | |
654 | } | |
655 | } | |
656 | if (cleanup_p == 0) | |
657 | old_p->post_handler = NULL; | |
658 | } | |
659 | mutex_unlock(&kprobe_mutex); | |
660 | } | |
661 | ||
662 | /* Call unregister_page_fault_notifier() | |
663 | * if no probes are active | |
664 | */ | |
665 | mutex_lock(&kprobe_mutex); | |
666 | if (atomic_add_return(-1, &kprobe_count) == \ | |
667 | ARCH_INACTIVE_KPROBE_COUNT) | |
668 | unregister_page_fault_notifier(&kprobe_page_fault_nb); | |
669 | mutex_unlock(&kprobe_mutex); | |
670 | return; | |
671 | } | |
672 | ||
673 | static struct notifier_block kprobe_exceptions_nb = { | |
674 | .notifier_call = kprobe_exceptions_notify, | |
675 | .priority = 0x7fffffff /* we need to be notified first */ | |
676 | }; | |
677 | ||
678 | ||
679 | int __kprobes register_jprobe(struct jprobe *jp) | |
680 | { | |
681 | /* Todo: Verify probepoint is a function entry point */ | |
682 | jp->kp.pre_handler = setjmp_pre_handler; | |
683 | jp->kp.break_handler = longjmp_break_handler; | |
684 | ||
685 | return __register_kprobe(&jp->kp, | |
686 | (unsigned long)__builtin_return_address(0)); | |
687 | } | |
688 | ||
689 | void __kprobes unregister_jprobe(struct jprobe *jp) | |
690 | { | |
691 | unregister_kprobe(&jp->kp); | |
692 | } | |
693 | ||
694 | #ifdef ARCH_SUPPORTS_KRETPROBES | |
695 | ||
696 | /* | |
697 | * This kprobe pre_handler is registered with every kretprobe. When probe | |
698 | * hits it will set up the return probe. | |
699 | */ | |
700 | static int __kprobes pre_handler_kretprobe(struct kprobe *p, | |
701 | struct pt_regs *regs) | |
702 | { | |
703 | struct kretprobe *rp = container_of(p, struct kretprobe, kp); | |
704 | unsigned long flags = 0; | |
705 | ||
706 | /*TODO: consider to only swap the RA after the last pre_handler fired */ | |
707 | spin_lock_irqsave(&kretprobe_lock, flags); | |
708 | if (!hlist_empty(&rp->free_instances)) { | |
709 | struct kretprobe_instance *ri; | |
710 | ||
711 | ri = hlist_entry(rp->free_instances.first, | |
712 | struct kretprobe_instance, uflist); | |
713 | ri->rp = rp; | |
714 | ri->task = current; | |
715 | arch_prepare_kretprobe(ri, regs); | |
716 | ||
717 | /* XXX(hch): why is there no hlist_move_head? */ | |
718 | hlist_del(&ri->uflist); | |
719 | hlist_add_head(&ri->uflist, &ri->rp->used_instances); | |
720 | hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task)); | |
721 | } else | |
722 | rp->nmissed++; | |
723 | spin_unlock_irqrestore(&kretprobe_lock, flags); | |
724 | return 0; | |
725 | } | |
726 | ||
727 | int __kprobes register_kretprobe(struct kretprobe *rp) | |
728 | { | |
729 | int ret = 0; | |
730 | struct kretprobe_instance *inst; | |
731 | int i; | |
732 | ||
733 | rp->kp.pre_handler = pre_handler_kretprobe; | |
734 | rp->kp.post_handler = NULL; | |
735 | rp->kp.fault_handler = NULL; | |
736 | rp->kp.break_handler = NULL; | |
737 | ||
738 | /* Pre-allocate memory for max kretprobe instances */ | |
739 | if (rp->maxactive <= 0) { | |
740 | #ifdef CONFIG_PREEMPT | |
741 | rp->maxactive = max(10, 2 * NR_CPUS); | |
742 | #else | |
743 | rp->maxactive = NR_CPUS; | |
744 | #endif | |
745 | } | |
746 | INIT_HLIST_HEAD(&rp->used_instances); | |
747 | INIT_HLIST_HEAD(&rp->free_instances); | |
748 | for (i = 0; i < rp->maxactive; i++) { | |
749 | inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL); | |
750 | if (inst == NULL) { | |
751 | free_rp_inst(rp); | |
752 | return -ENOMEM; | |
753 | } | |
754 | INIT_HLIST_NODE(&inst->uflist); | |
755 | hlist_add_head(&inst->uflist, &rp->free_instances); | |
756 | } | |
757 | ||
758 | rp->nmissed = 0; | |
759 | /* Establish function entry probe point */ | |
760 | if ((ret = __register_kprobe(&rp->kp, | |
761 | (unsigned long)__builtin_return_address(0))) != 0) | |
762 | free_rp_inst(rp); | |
763 | return ret; | |
764 | } | |
765 | ||
766 | #else /* ARCH_SUPPORTS_KRETPROBES */ | |
767 | ||
768 | int __kprobes register_kretprobe(struct kretprobe *rp) | |
769 | { | |
770 | return -ENOSYS; | |
771 | } | |
772 | ||
773 | static int __kprobes pre_handler_kretprobe(struct kprobe *p, | |
774 | struct pt_regs *regs) | |
775 | { | |
776 | return 0; | |
777 | } | |
778 | ||
779 | #endif /* ARCH_SUPPORTS_KRETPROBES */ | |
780 | ||
781 | void __kprobes unregister_kretprobe(struct kretprobe *rp) | |
782 | { | |
783 | unsigned long flags; | |
784 | struct kretprobe_instance *ri; | |
785 | struct hlist_node *pos, *next; | |
786 | ||
787 | unregister_kprobe(&rp->kp); | |
788 | ||
789 | /* No race here */ | |
790 | spin_lock_irqsave(&kretprobe_lock, flags); | |
791 | hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) { | |
792 | ri->rp = NULL; | |
793 | hlist_del(&ri->uflist); | |
794 | } | |
795 | spin_unlock_irqrestore(&kretprobe_lock, flags); | |
796 | free_rp_inst(rp); | |
797 | } | |
798 | ||
799 | static int __init init_kprobes(void) | |
800 | { | |
801 | int i, err = 0; | |
802 | ||
803 | /* FIXME allocate the probe table, currently defined statically */ | |
804 | /* initialize all list heads */ | |
805 | for (i = 0; i < KPROBE_TABLE_SIZE; i++) { | |
806 | INIT_HLIST_HEAD(&kprobe_table[i]); | |
807 | INIT_HLIST_HEAD(&kretprobe_inst_table[i]); | |
808 | } | |
809 | atomic_set(&kprobe_count, 0); | |
810 | ||
811 | /* By default, kprobes are enabled */ | |
812 | kprobe_enabled = true; | |
813 | ||
814 | err = arch_init_kprobes(); | |
815 | if (!err) | |
816 | err = register_die_notifier(&kprobe_exceptions_nb); | |
817 | ||
818 | return err; | |
819 | } | |
820 | ||
821 | #ifdef CONFIG_DEBUG_FS | |
822 | static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p, | |
823 | const char *sym, int offset,char *modname) | |
824 | { | |
825 | char *kprobe_type; | |
826 | ||
827 | if (p->pre_handler == pre_handler_kretprobe) | |
828 | kprobe_type = "r"; | |
829 | else if (p->pre_handler == setjmp_pre_handler) | |
830 | kprobe_type = "j"; | |
831 | else | |
832 | kprobe_type = "k"; | |
833 | if (sym) | |
834 | seq_printf(pi, "%p %s %s+0x%x %s\n", p->addr, kprobe_type, | |
835 | sym, offset, (modname ? modname : " ")); | |
836 | else | |
837 | seq_printf(pi, "%p %s %p\n", p->addr, kprobe_type, p->addr); | |
838 | } | |
839 | ||
840 | static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos) | |
841 | { | |
842 | return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL; | |
843 | } | |
844 | ||
845 | static void __kprobes *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos) | |
846 | { | |
847 | (*pos)++; | |
848 | if (*pos >= KPROBE_TABLE_SIZE) | |
849 | return NULL; | |
850 | return pos; | |
851 | } | |
852 | ||
853 | static void __kprobes kprobe_seq_stop(struct seq_file *f, void *v) | |
854 | { | |
855 | /* Nothing to do */ | |
856 | } | |
857 | ||
858 | static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v) | |
859 | { | |
860 | struct hlist_head *head; | |
861 | struct hlist_node *node; | |
862 | struct kprobe *p, *kp; | |
863 | const char *sym = NULL; | |
864 | unsigned int i = *(loff_t *) v; | |
865 | unsigned long offset = 0; | |
866 | char *modname, namebuf[128]; | |
867 | ||
868 | head = &kprobe_table[i]; | |
869 | preempt_disable(); | |
870 | hlist_for_each_entry_rcu(p, node, head, hlist) { | |
871 | sym = kallsyms_lookup((unsigned long)p->addr, NULL, | |
872 | &offset, &modname, namebuf); | |
873 | if (p->pre_handler == aggr_pre_handler) { | |
874 | list_for_each_entry_rcu(kp, &p->list, list) | |
875 | report_probe(pi, kp, sym, offset, modname); | |
876 | } else | |
877 | report_probe(pi, p, sym, offset, modname); | |
878 | } | |
879 | preempt_enable(); | |
880 | return 0; | |
881 | } | |
882 | ||
883 | static struct seq_operations kprobes_seq_ops = { | |
884 | .start = kprobe_seq_start, | |
885 | .next = kprobe_seq_next, | |
886 | .stop = kprobe_seq_stop, | |
887 | .show = show_kprobe_addr | |
888 | }; | |
889 | ||
890 | static int __kprobes kprobes_open(struct inode *inode, struct file *filp) | |
891 | { | |
892 | return seq_open(filp, &kprobes_seq_ops); | |
893 | } | |
894 | ||
895 | static struct file_operations debugfs_kprobes_operations = { | |
896 | .open = kprobes_open, | |
897 | .read = seq_read, | |
898 | .llseek = seq_lseek, | |
899 | .release = seq_release, | |
900 | }; | |
901 | ||
902 | static void __kprobes enable_all_kprobes(void) | |
903 | { | |
904 | struct hlist_head *head; | |
905 | struct hlist_node *node; | |
906 | struct kprobe *p; | |
907 | unsigned int i; | |
908 | ||
909 | mutex_lock(&kprobe_mutex); | |
910 | ||
911 | /* If kprobes are already enabled, just return */ | |
912 | if (kprobe_enabled) | |
913 | goto already_enabled; | |
914 | ||
915 | /* | |
916 | * Re-register the page fault notifier only if there are any | |
917 | * active probes at the time of enabling kprobes globally | |
918 | */ | |
919 | if (atomic_read(&kprobe_count) > ARCH_INACTIVE_KPROBE_COUNT) | |
920 | register_page_fault_notifier(&kprobe_page_fault_nb); | |
921 | ||
922 | for (i = 0; i < KPROBE_TABLE_SIZE; i++) { | |
923 | head = &kprobe_table[i]; | |
924 | hlist_for_each_entry_rcu(p, node, head, hlist) | |
925 | arch_arm_kprobe(p); | |
926 | } | |
927 | ||
928 | kprobe_enabled = true; | |
929 | printk(KERN_INFO "Kprobes globally enabled\n"); | |
930 | ||
931 | already_enabled: | |
932 | mutex_unlock(&kprobe_mutex); | |
933 | return; | |
934 | } | |
935 | ||
936 | static void __kprobes disable_all_kprobes(void) | |
937 | { | |
938 | struct hlist_head *head; | |
939 | struct hlist_node *node; | |
940 | struct kprobe *p; | |
941 | unsigned int i; | |
942 | ||
943 | mutex_lock(&kprobe_mutex); | |
944 | ||
945 | /* If kprobes are already disabled, just return */ | |
946 | if (!kprobe_enabled) | |
947 | goto already_disabled; | |
948 | ||
949 | kprobe_enabled = false; | |
950 | printk(KERN_INFO "Kprobes globally disabled\n"); | |
951 | for (i = 0; i < KPROBE_TABLE_SIZE; i++) { | |
952 | head = &kprobe_table[i]; | |
953 | hlist_for_each_entry_rcu(p, node, head, hlist) { | |
954 | if (!arch_trampoline_kprobe(p)) | |
955 | arch_disarm_kprobe(p); | |
956 | } | |
957 | } | |
958 | ||
959 | mutex_unlock(&kprobe_mutex); | |
960 | /* Allow all currently running kprobes to complete */ | |
961 | synchronize_sched(); | |
962 | ||
963 | mutex_lock(&kprobe_mutex); | |
964 | /* Unconditionally unregister the page_fault notifier */ | |
965 | unregister_page_fault_notifier(&kprobe_page_fault_nb); | |
966 | ||
967 | already_disabled: | |
968 | mutex_unlock(&kprobe_mutex); | |
969 | return; | |
970 | } | |
971 | ||
972 | /* | |
973 | * XXX: The debugfs bool file interface doesn't allow for callbacks | |
974 | * when the bool state is switched. We can reuse that facility when | |
975 | * available | |
976 | */ | |
977 | static ssize_t read_enabled_file_bool(struct file *file, | |
978 | char __user *user_buf, size_t count, loff_t *ppos) | |
979 | { | |
980 | char buf[3]; | |
981 | ||
982 | if (kprobe_enabled) | |
983 | buf[0] = '1'; | |
984 | else | |
985 | buf[0] = '0'; | |
986 | buf[1] = '\n'; | |
987 | buf[2] = 0x00; | |
988 | return simple_read_from_buffer(user_buf, count, ppos, buf, 2); | |
989 | } | |
990 | ||
991 | static ssize_t write_enabled_file_bool(struct file *file, | |
992 | const char __user *user_buf, size_t count, loff_t *ppos) | |
993 | { | |
994 | char buf[32]; | |
995 | int buf_size; | |
996 | ||
997 | buf_size = min(count, (sizeof(buf)-1)); | |
998 | if (copy_from_user(buf, user_buf, buf_size)) | |
999 | return -EFAULT; | |
1000 | ||
1001 | switch (buf[0]) { | |
1002 | case 'y': | |
1003 | case 'Y': | |
1004 | case '1': | |
1005 | enable_all_kprobes(); | |
1006 | break; | |
1007 | case 'n': | |
1008 | case 'N': | |
1009 | case '0': | |
1010 | disable_all_kprobes(); | |
1011 | break; | |
1012 | } | |
1013 | ||
1014 | return count; | |
1015 | } | |
1016 | ||
1017 | static struct file_operations fops_kp = { | |
1018 | .read = read_enabled_file_bool, | |
1019 | .write = write_enabled_file_bool, | |
1020 | }; | |
1021 | ||
1022 | static int __kprobes debugfs_kprobe_init(void) | |
1023 | { | |
1024 | struct dentry *dir, *file; | |
1025 | unsigned int value = 1; | |
1026 | ||
1027 | dir = debugfs_create_dir("kprobes", NULL); | |
1028 | if (!dir) | |
1029 | return -ENOMEM; | |
1030 | ||
1031 | file = debugfs_create_file("list", 0444, dir, NULL, | |
1032 | &debugfs_kprobes_operations); | |
1033 | if (!file) { | |
1034 | debugfs_remove(dir); | |
1035 | return -ENOMEM; | |
1036 | } | |
1037 | ||
1038 | file = debugfs_create_file("enabled", 0600, dir, | |
1039 | &value, &fops_kp); | |
1040 | if (!file) { | |
1041 | debugfs_remove(dir); | |
1042 | return -ENOMEM; | |
1043 | } | |
1044 | ||
1045 | return 0; | |
1046 | } | |
1047 | ||
1048 | late_initcall(debugfs_kprobe_init); | |
1049 | #endif /* CONFIG_DEBUG_FS */ | |
1050 | ||
1051 | module_init(init_kprobes); | |
1052 | ||
1053 | EXPORT_SYMBOL_GPL(register_kprobe); | |
1054 | EXPORT_SYMBOL_GPL(unregister_kprobe); | |
1055 | EXPORT_SYMBOL_GPL(register_jprobe); | |
1056 | EXPORT_SYMBOL_GPL(unregister_jprobe); | |
1057 | EXPORT_SYMBOL_GPL(jprobe_return); | |
1058 | EXPORT_SYMBOL_GPL(register_kretprobe); | |
1059 | EXPORT_SYMBOL_GPL(unregister_kretprobe); |