summaryrefslogtreecommitdiffstats
path: root/kernel/kprobes.c
blob: 65242529a75f1355e890fd92cda79b6a9d30ce81 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
/*
 *  Kernel Probes (KProbes)
 *  kernel/kprobes.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 *
 * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
 *		Probes initial implementation (includes suggestions from
 *		Rusty Russell).
 * 2004-Aug	Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
 *		hlists and exceptions notifier as suggested by Andi Kleen.
 * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *		interface to access function arguments.
 * 2004-Sep	Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
 *		exceptions notifier to be first on the priority list.
 * 2005-May	Hien Nguyen <hien@us.ibm.com>, Jim Keniston
 *		<jkenisto@us.ibm.com> and Prasanna S Panchamukhi
 *		<prasanna@in.ibm.com> added function-return probes.
 */
#include <linux/kprobes.h>
#include <linux/spinlock.h>
#include <linux/hash.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
#include <asm/errno.h>
#include <asm/kdebug.h>

#define KPROBE_HASH_BITS 6
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)

static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];

unsigned int kprobe_cpu = NR_CPUS;
static DEFINE_SPINLOCK(kprobe_lock);
static struct kprobe *curr_kprobe;

/*
 * kprobe->ainsn.insn points to the copy of the instruction to be
 * single-stepped. x86_64, POWER4 and above have no-exec support and
 * stepping on the instruction on a vmalloced/kmalloced/data page
 * is a recipe for disaster
 */
#define INSNS_PER_PAGE	(PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))

struct kprobe_insn_page {
	struct hlist_node hlist;
	kprobe_opcode_t *insns;		/* Page of instruction slots */
	char slot_used[INSNS_PER_PAGE];
	int nused;
};

static struct hlist_head kprobe_insn_pages;

/**
 * get_insn_slot() - Find a slot on an executable page for an instruction.
 * We allocate an executable page if there's no room on existing ones.
 */
kprobe_opcode_t *get_insn_slot(void)
{
	struct kprobe_insn_page *kip;
	struct hlist_node *pos;

	hlist_for_each(pos, &kprobe_insn_pages) {
		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
		if (kip->nused < INSNS_PER_PAGE) {
			int i;
			for (i = 0; i < INSNS_PER_PAGE; i++) {
				if (!kip->slot_used[i]) {
					kip->slot_used[i] = 1;
					kip->nused++;
					return kip->insns + (i * MAX_INSN_SIZE);
				}
			}
			/* Surprise!  No unused slots.  Fix kip->nused. */
			kip->nused = INSNS_PER_PAGE;
		}
	}

	/* All out of space.  Need to allocate a new page. Use slot 0.*/
	kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
	if (!kip) {
		return NULL;
	}

	/*
	 * Use module_alloc so this page is within +/- 2GB of where the
	 * kernel image and loaded module images reside. This is required
	 * so x86_64 can correctly handle the %rip-relative fixups.
	 */
	kip->insns = module_alloc(PAGE_SIZE);
	if (!kip->insns) {
		kfree(kip);
		return NULL;
	}
	INIT_HLIST_NODE(&kip->hlist);
	hlist_add_head(&kip->hlist, &kprobe_insn_pages);
	memset(kip->slot_used, 0, INSNS_PER_PAGE);
	kip->slot_used[0] = 1;
	kip->nused = 1;
	return kip->insns;
}

void free_insn_slot(kprobe_opcode_t *slot)
{
	struct kprobe_insn_page *kip;
	struct hlist_node *pos;

	hlist_for_each(pos, &kprobe_insn_pages) {
		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
		if (kip->insns <= slot &&
		    slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
			int i = (slot - kip->insns) / MAX_INSN_SIZE;
			kip->slot_used[i] = 0;
			kip->nused--;
			if (kip->nused == 0) {
				/*
				 * Page is no longer in use.  Free it unless
				 * it's the last one.  We keep the last one
				 * so as not to have to set it up again the
				 * next time somebody inserts a probe.
				 */
				hlist_del(&kip->hlist);
				if (hlist_empty(&kprobe_insn_pages)) {
					INIT_HLIST_NODE(&kip->hlist);
					hlist_add_head(&kip->hlist,
						&kprobe_insn_pages);
				} else {
					module_free(NULL, kip->insns);
					kfree(kip);
				}
			}
			return;
		}
	}
}

/* Locks kprobe: irqs must be disabled */
void lock_kprobes(void)
{
	spin_lock(&kprobe_lock);
	kprobe_cpu = smp_processor_id();
}

void unlock_kprobes(void)
{
	kprobe_cpu = NR_CPUS;
	spin_unlock(&kprobe_lock);
}

/* You have to be holding the kprobe_lock */
struct kprobe *get_kprobe(void *addr)
{
	struct hlist_head *head;
	struct hlist_node *node;

	head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
	hlist_for_each(node, head) {
		struct kprobe *p = hlist_entry(node, struct kprobe, hlist);
		if (p->addr == addr)
			return p;
	}
	return NULL;
}

/*
 * Aggregate handlers for multiple kprobes support - these handlers
 * take care of invoking the individual kprobe handlers on p->list
 */
static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe *kp;

	list_for_each_entry(kp, &p->list, list) {
		if (kp->pre_handler) {
			curr_kprobe = kp;
			if (kp->pre_handler(kp, regs))
				return 1;
		}
		curr_kprobe = NULL;
	}
	return 0;
}

static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
			      unsigned long flags)
{
	struct kprobe *kp;

	list_for_each_entry(kp, &p->list, list) {
		if (kp->post_handler) {
			curr_kprobe = kp;
			kp->post_handler(kp, regs, flags);
			curr_kprobe = NULL;
		}
	}
	return;
}

static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
			      int trapnr)
{
	/*
	 * if we faulted "during" the execution of a user specified
	 * probe handler, invoke just that probe's fault handler
	 */
	if (curr_kprobe && curr_kprobe->fault_handler) {
		if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))
			return 1;
	}
	return 0;
}

static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe *kp = curr_kprobe;
	if (curr_kprobe && kp->break_handler) {
		if (kp->break_handler(kp, regs)) {
			curr_kprobe = NULL;
			return 1;
		}
	}
	curr_kprobe = NULL;
	return 0;
}

struct kprobe trampoline_p = {
		.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
		.pre_handler = trampoline_probe_handler,
		.post_handler = trampoline_post_handler
};

struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp)
{
	struct hlist_node *node;
	struct kretprobe_instance *ri;
	hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
		return ri;
	return NULL;
}

static struct kretprobe_instance *get_used_rp_inst(struct kretprobe *rp)
{
	struct hlist_node *node;
	struct kretprobe_instance *ri;
	hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
		return ri;
	return NULL;
}

struct kretprobe_instance *get_rp_inst(void *sara)
{
	struct hlist_head *head;
	struct hlist_node *node;
	struct task_struct *tsk;
	struct kretprobe_instance *ri;

	tsk = arch_get_kprobe_task(sara);
	head = &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
	hlist_for_each_entry(ri, node, head, hlist) {
		if (ri->stack_addr == sara)
			return ri;
	}
	return NULL;
}

void add_rp_inst(struct kretprobe_instance *ri)
{
	struct task_struct *tsk;
	/*
	 * Remove rp inst off the free list -
	 * Add it back when probed function returns
	 */
	hlist_del(&ri->uflist);
	tsk = arch_get_kprobe_task(ri->stack_addr);
	/* Add rp inst onto table */
	INIT_HLIST_NODE(&ri->hlist);
	hlist_add_head(&ri->hlist,
			&kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)]);

	/* Also add this rp inst to the used list. */
	INIT_HLIST_NODE(&ri->uflist);
	hlist_add_head(&ri->uflist, &ri->rp->used_instances);
}

void recycle_rp_inst(struct kretprobe_instance *ri)
{
	/* remove rp inst off the rprobe_inst_table */
	hlist_del(&ri->hlist);
	if (ri->rp) {
		/* remove rp inst off the used list */
		hlist_del(&ri->uflist);
		/* put rp inst back onto the free list */
		INIT_HLIST_NODE(&ri->uflist);
		hlist_add_head(&ri->uflist, &ri->rp->free_instances);
	} else
		/* Unregistering */
		kfree(ri);
}

struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk)
{
	return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
}

struct kretprobe_instance *get_rp_inst_tsk(struct task_struct *tk)
{
	struct task_struct *tsk;
	struct hlist_head *head;
	struct hlist_node *node;
	struct kretprobe_instance *ri;

	head = &kretprobe_inst_table[hash_ptr(tk, KPROBE_HASH_BITS)];

	hlist_for_each_entry(ri, node, head, hlist) {
		tsk = arch_get_kprobe_task(ri->stack_addr);
		if (tsk == tk)
			return ri;
	}
	return NULL;
}

/*
 * This function is called from do_exit or do_execv when task tk's stack is
 * about to be recycled. Recycle any function-return probe instances
 * associated with this task. These represent probed functions that have
 * been called but may never return.
 */
void kprobe_flush_task(struct task_struct *tk)
{
	unsigned long flags = 0;
	spin_lock_irqsave(&kprobe_lock, flags);
	arch_kprobe_flush_task(tk);
	spin_unlock_irqrestore(&kprobe_lock, flags);
}

/*
 * This kprobe pre_handler is registered with every kretprobe. When probe
 * hits it will set up the return probe.
 */
static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
{
	struct kretprobe *rp = container_of(p, struct kretprobe, kp);

	/*TODO: consider to only swap the RA after the last pre_handler fired */
	arch_prepare_kretprobe(rp, regs);
	return 0;
}

static inline void free_rp_inst(struct kretprobe *rp)
{
	struct kretprobe_instance *ri;
	while ((ri = get_free_rp_inst(rp)) != NULL) {
		hlist_del(&ri->uflist);
		kfree(ri);
	}
}

/*
 * Keep all fields in the kprobe consistent
 */
static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
{
	memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
	memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
}

/*
* Add the new probe to old_p->list. Fail if this is the
* second jprobe at the address - two jprobes can't coexist
*/
static int add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
{
        struct kprobe *kp;

	if (p->break_handler) {
		list_for_each_entry(kp, &old_p->list, list) {
			if (kp->break_handler)
				return -EEXIST;
		}
		list_add_tail(&p->list, &old_p->list);
	} else
		list_add(&p->list, &old_p->list);
	return 0;
}

/*
 * Fill in the required fields of the "manager kprobe". Replace the
 * earlier kprobe in the hlist with the manager kprobe
 */
static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
{
	copy_kprobe(p, ap);
	ap->addr = p->addr;
	ap->pre_handler = aggr_pre_handler;
	ap->post_handler = aggr_post_handler;
	ap->fault_handler = aggr_fault_handler;
	ap->break_handler = aggr_break_handler;

	INIT_LIST_HEAD(&ap->list);
	list_add(&p->list, &ap->list);

	INIT_HLIST_NODE(&ap->hlist);
	hlist_del(&p->hlist);
	hlist_add_head(&ap->hlist,
		&kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
}

/*
 * This is the second or subsequent kprobe at the address - handle
 * the intricacies
 * TODO: Move kcalloc outside the spinlock
 */
static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p)
{
	int ret = 0;
	struct kprobe *ap;

	if (old_p->pre_handler == aggr_pre_handler) {
		copy_kprobe(old_p, p);
		ret = add_new_kprobe(old_p, p);
	} else {
		ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);
		if (!ap)
			return -ENOMEM;
		add_aggr_kprobe(ap, old_p);
		copy_kprobe(ap, p);
		ret = add_new_kprobe(ap, p);
	}
	return ret;
}

/* kprobe removal house-keeping routines */
static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
{
	arch_disarm_kprobe(p);
	hlist_del(&p->hlist);
	spin_unlock_irqrestore(&kprobe_lock, flags);
	arch_remove_kprobe(p);
}

static inline void cleanup_aggr_kprobe(struct kprobe *old_p,
		struct kprobe *p, unsigned long flags)
{
	list_del(&p->list);
	if (list_empty(&old_p->list)) {
		cleanup_kprobe(old_p, flags);
		kfree(old_p);
	} else
		spin_unlock_irqrestore(&kprobe_lock, flags);
}

int register_kprobe(struct kprobe *p)
{
	int ret = 0;
	unsigned long flags = 0;
	struct kprobe *old_p;

	if ((ret = arch_prepare_kprobe(p)) != 0) {
		goto rm_kprobe;
	}
	spin_lock_irqsave(&kprobe_lock, flags);
	old_p = get_kprobe(p->addr);
	p->nmissed = 0;
	if (old_p) {
		ret = register_aggr_kprobe(old_p, p);
		goto out;
	}

	arch_copy_kprobe(p);
	INIT_HLIST_NODE(&p->hlist);
	hlist_add_head(&p->hlist,
		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);

  	arch_arm_kprobe(p);

out:
	spin_unlock_irqrestore(&kprobe_lock, flags);
rm_kprobe:
	if (ret == -EEXIST)
		arch_remove_kprobe(p);
	return ret;
}

void unregister_kprobe(struct kprobe *p)
{
	unsigned long flags;
	struct kprobe *old_p;

	spin_lock_irqsave(&kprobe_lock, flags);
	old_p = get_kprobe(p->addr);
	if (old_p) {
		if (old_p->pre_handler == aggr_pre_handler)
			cleanup_aggr_kprobe(old_p, p, flags);
		else
			cleanup_kprobe(p, flags);
	} else
		spin_unlock_irqrestore(&kprobe_lock, flags);
}

static struct notifier_block kprobe_exceptions_nb = {
	.notifier_call = kprobe_exceptions_notify,
	.priority = 0x7fffffff /* we need to notified first */
};

int register_jprobe(struct jprobe *jp)
{
	/* Todo: Verify probepoint is a function entry point */
	jp->kp.pre_handler = setjmp_pre_handler;
	jp->kp.break_handler = longjmp_break_handler;

	return register_kprobe(&jp->kp);
}

void unregister_jprobe(struct jprobe *jp)
{
	unregister_kprobe(&jp->kp);
}

#ifdef ARCH_SUPPORTS_KRETPROBES

int register_kretprobe(struct kretprobe *rp)
{
	int ret = 0;
	struct kretprobe_instance *inst;
	int i;

	rp->kp.pre_handler = pre_handler_kretprobe;

	/* Pre-allocate memory for max kretprobe instances */
	if (rp->maxactive <= 0) {
#ifdef CONFIG_PREEMPT
		rp->maxactive = max(10, 2 * NR_CPUS);
#else
		rp->maxactive = NR_CPUS;
#endif
	}
	INIT_HLIST_HEAD(&rp->used_instances);
	INIT_HLIST_HEAD(&rp->free_instances);
	for (i = 0; i < rp->maxactive; i++) {
		inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
		if (inst == NULL) {
			free_rp_inst(rp);
			return -ENOMEM;
		}
		INIT_HLIST_NODE(&inst->uflist);
		hlist_add_head(&inst->uflist, &rp->free_instances);
	}

	rp->nmissed = 0;
	/* Establish function entry probe point */
	if ((ret = register_kprobe(&rp->kp)) != 0)
		free_rp_inst(rp);
	return ret;
}

#else /* ARCH_SUPPORTS_KRETPROBES */

int register_kretprobe(struct kretprobe *rp)
{
	return -ENOSYS;
}

#endif /* ARCH_SUPPORTS_KRETPROBES */

void unregister_kretprobe(struct kretprobe *rp)
{
	unsigned long flags;
	struct kretprobe_instance *ri;

	unregister_kprobe(&rp->kp);
	/* No race here */
	spin_lock_irqsave(&kprobe_lock, flags);
	free_rp_inst(rp);
	while ((ri = get_used_rp_inst(rp)) != NULL) {
		ri->rp = NULL;
		hlist_del(&ri->uflist);
	}
	spin_unlock_irqrestore(&kprobe_lock, flags);
}

static int __init init_kprobes(void)
{
	int i, err = 0;

	/* FIXME allocate the probe table, currently defined statically */
	/* initialize all list heads */
	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
		INIT_HLIST_HEAD(&kprobe_table[i]);
		INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
	}

	err = register_die_notifier(&kprobe_exceptions_nb);
	/* Register the trampoline probe for return probe */
	register_kprobe(&trampoline_p);
	return err;
}

__initcall(init_kprobes);

EXPORT_SYMBOL_GPL(register_kprobe);
EXPORT_SYMBOL_GPL(unregister_kprobe);
EXPORT_SYMBOL_GPL(register_jprobe);
EXPORT_SYMBOL_GPL(unregister_jprobe);
EXPORT_SYMBOL_GPL(jprobe_return);
EXPORT_SYMBOL_GPL(register_kretprobe);
EXPORT_SYMBOL_GPL(unregister_kretprobe);