[NETFILTER]: nf_conntrack: add helper function for expectation initialization
[hh.org.git] / kernel / kprobes.c
blob610c837ad9e0aa8923f48541aaa7ea903c6b2fd2
1 /*
2 * Kernel Probes (KProbes)
3 * kernel/kprobes.c
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.
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.
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.
19 * Copyright (C) IBM Corporation, 2002, 2004
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.
34 #include <linux/kprobes.h>
35 #include <linux/hash.h>
36 #include <linux/init.h>
37 #include <linux/slab.h>
38 #include <linux/module.h>
39 #include <linux/moduleloader.h>
40 #include <linux/kallsyms.h>
41 #include <asm-generic/sections.h>
42 #include <asm/cacheflush.h>
43 #include <asm/errno.h>
44 #include <asm/kdebug.h>
46 #define KPROBE_HASH_BITS 6
47 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
51 * Some oddball architectures like 64bit powerpc have function descriptors
52 * so this must be overridable.
54 #ifndef kprobe_lookup_name
55 #define kprobe_lookup_name(name, addr) \
56 addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
57 #endif
59 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
60 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
61 static atomic_t kprobe_count;
63 DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */
64 DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */
65 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
67 static struct notifier_block kprobe_page_fault_nb = {
68 .notifier_call = kprobe_exceptions_notify,
69 .priority = 0x7fffffff /* we need to notified first */
72 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
74 * kprobe->ainsn.insn points to the copy of the instruction to be
75 * single-stepped. x86_64, POWER4 and above have no-exec support and
76 * stepping on the instruction on a vmalloced/kmalloced/data page
77 * is a recipe for disaster
79 #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
81 struct kprobe_insn_page {
82 struct hlist_node hlist;
83 kprobe_opcode_t *insns; /* Page of instruction slots */
84 char slot_used[INSNS_PER_PAGE];
85 int nused;
88 static struct hlist_head kprobe_insn_pages;
90 /**
91 * get_insn_slot() - Find a slot on an executable page for an instruction.
92 * We allocate an executable page if there's no room on existing ones.
94 kprobe_opcode_t __kprobes *get_insn_slot(void)
96 struct kprobe_insn_page *kip;
97 struct hlist_node *pos;
99 hlist_for_each(pos, &kprobe_insn_pages) {
100 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
101 if (kip->nused < INSNS_PER_PAGE) {
102 int i;
103 for (i = 0; i < INSNS_PER_PAGE; i++) {
104 if (!kip->slot_used[i]) {
105 kip->slot_used[i] = 1;
106 kip->nused++;
107 return kip->insns + (i * MAX_INSN_SIZE);
110 /* Surprise! No unused slots. Fix kip->nused. */
111 kip->nused = INSNS_PER_PAGE;
115 /* All out of space. Need to allocate a new page. Use slot 0.*/
116 kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
117 if (!kip) {
118 return NULL;
122 * Use module_alloc so this page is within +/- 2GB of where the
123 * kernel image and loaded module images reside. This is required
124 * so x86_64 can correctly handle the %rip-relative fixups.
126 kip->insns = module_alloc(PAGE_SIZE);
127 if (!kip->insns) {
128 kfree(kip);
129 return NULL;
131 INIT_HLIST_NODE(&kip->hlist);
132 hlist_add_head(&kip->hlist, &kprobe_insn_pages);
133 memset(kip->slot_used, 0, INSNS_PER_PAGE);
134 kip->slot_used[0] = 1;
135 kip->nused = 1;
136 return kip->insns;
139 void __kprobes free_insn_slot(kprobe_opcode_t *slot)
141 struct kprobe_insn_page *kip;
142 struct hlist_node *pos;
144 hlist_for_each(pos, &kprobe_insn_pages) {
145 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
146 if (kip->insns <= slot &&
147 slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
148 int i = (slot - kip->insns) / MAX_INSN_SIZE;
149 kip->slot_used[i] = 0;
150 kip->nused--;
151 if (kip->nused == 0) {
153 * Page is no longer in use. Free it unless
154 * it's the last one. We keep the last one
155 * so as not to have to set it up again the
156 * next time somebody inserts a probe.
158 hlist_del(&kip->hlist);
159 if (hlist_empty(&kprobe_insn_pages)) {
160 INIT_HLIST_NODE(&kip->hlist);
161 hlist_add_head(&kip->hlist,
162 &kprobe_insn_pages);
163 } else {
164 module_free(NULL, kip->insns);
165 kfree(kip);
168 return;
172 #endif
174 /* We have preemption disabled.. so it is safe to use __ versions */
175 static inline void set_kprobe_instance(struct kprobe *kp)
177 __get_cpu_var(kprobe_instance) = kp;
180 static inline void reset_kprobe_instance(void)
182 __get_cpu_var(kprobe_instance) = NULL;
186 * This routine is called either:
187 * - under the kprobe_mutex - during kprobe_[un]register()
188 * OR
189 * - with preemption disabled - from arch/xxx/kernel/kprobes.c
191 struct kprobe __kprobes *get_kprobe(void *addr)
193 struct hlist_head *head;
194 struct hlist_node *node;
195 struct kprobe *p;
197 head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
198 hlist_for_each_entry_rcu(p, node, head, hlist) {
199 if (p->addr == addr)
200 return p;
202 return NULL;
206 * Aggregate handlers for multiple kprobes support - these handlers
207 * take care of invoking the individual kprobe handlers on p->list
209 static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
211 struct kprobe *kp;
213 list_for_each_entry_rcu(kp, &p->list, list) {
214 if (kp->pre_handler) {
215 set_kprobe_instance(kp);
216 if (kp->pre_handler(kp, regs))
217 return 1;
219 reset_kprobe_instance();
221 return 0;
224 static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
225 unsigned long flags)
227 struct kprobe *kp;
229 list_for_each_entry_rcu(kp, &p->list, list) {
230 if (kp->post_handler) {
231 set_kprobe_instance(kp);
232 kp->post_handler(kp, regs, flags);
233 reset_kprobe_instance();
236 return;
239 static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
240 int trapnr)
242 struct kprobe *cur = __get_cpu_var(kprobe_instance);
245 * if we faulted "during" the execution of a user specified
246 * probe handler, invoke just that probe's fault handler
248 if (cur && cur->fault_handler) {
249 if (cur->fault_handler(cur, regs, trapnr))
250 return 1;
252 return 0;
255 static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
257 struct kprobe *cur = __get_cpu_var(kprobe_instance);
258 int ret = 0;
260 if (cur && cur->break_handler) {
261 if (cur->break_handler(cur, regs))
262 ret = 1;
264 reset_kprobe_instance();
265 return ret;
268 /* Walks the list and increments nmissed count for multiprobe case */
269 void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
271 struct kprobe *kp;
272 if (p->pre_handler != aggr_pre_handler) {
273 p->nmissed++;
274 } else {
275 list_for_each_entry_rcu(kp, &p->list, list)
276 kp->nmissed++;
278 return;
281 /* Called with kretprobe_lock held */
282 struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
284 struct hlist_node *node;
285 struct kretprobe_instance *ri;
286 hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
287 return ri;
288 return NULL;
291 /* Called with kretprobe_lock held */
292 static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe
293 *rp)
295 struct hlist_node *node;
296 struct kretprobe_instance *ri;
297 hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
298 return ri;
299 return NULL;
302 /* Called with kretprobe_lock held */
303 void __kprobes add_rp_inst(struct kretprobe_instance *ri)
306 * Remove rp inst off the free list -
307 * Add it back when probed function returns
309 hlist_del(&ri->uflist);
311 /* Add rp inst onto table */
312 INIT_HLIST_NODE(&ri->hlist);
313 hlist_add_head(&ri->hlist,
314 &kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);
316 /* Also add this rp inst to the used list. */
317 INIT_HLIST_NODE(&ri->uflist);
318 hlist_add_head(&ri->uflist, &ri->rp->used_instances);
321 /* Called with kretprobe_lock held */
322 void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
323 struct hlist_head *head)
325 /* remove rp inst off the rprobe_inst_table */
326 hlist_del(&ri->hlist);
327 if (ri->rp) {
328 /* remove rp inst off the used list */
329 hlist_del(&ri->uflist);
330 /* put rp inst back onto the free list */
331 INIT_HLIST_NODE(&ri->uflist);
332 hlist_add_head(&ri->uflist, &ri->rp->free_instances);
333 } else
334 /* Unregistering */
335 hlist_add_head(&ri->hlist, head);
338 struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
340 return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
344 * This function is called from finish_task_switch when task tk becomes dead,
345 * so that we can recycle any function-return probe instances associated
346 * with this task. These left over instances represent probed functions
347 * that have been called but will never return.
349 void __kprobes kprobe_flush_task(struct task_struct *tk)
351 struct kretprobe_instance *ri;
352 struct hlist_head *head, empty_rp;
353 struct hlist_node *node, *tmp;
354 unsigned long flags = 0;
356 INIT_HLIST_HEAD(&empty_rp);
357 spin_lock_irqsave(&kretprobe_lock, flags);
358 head = kretprobe_inst_table_head(tk);
359 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
360 if (ri->task == tk)
361 recycle_rp_inst(ri, &empty_rp);
363 spin_unlock_irqrestore(&kretprobe_lock, flags);
365 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
366 hlist_del(&ri->hlist);
367 kfree(ri);
371 static inline void free_rp_inst(struct kretprobe *rp)
373 struct kretprobe_instance *ri;
374 while ((ri = get_free_rp_inst(rp)) != NULL) {
375 hlist_del(&ri->uflist);
376 kfree(ri);
381 * Keep all fields in the kprobe consistent
383 static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
385 memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
386 memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
390 * Add the new probe to old_p->list. Fail if this is the
391 * second jprobe at the address - two jprobes can't coexist
393 static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
395 if (p->break_handler) {
396 if (old_p->break_handler)
397 return -EEXIST;
398 list_add_tail_rcu(&p->list, &old_p->list);
399 old_p->break_handler = aggr_break_handler;
400 } else
401 list_add_rcu(&p->list, &old_p->list);
402 if (p->post_handler && !old_p->post_handler)
403 old_p->post_handler = aggr_post_handler;
404 return 0;
408 * Fill in the required fields of the "manager kprobe". Replace the
409 * earlier kprobe in the hlist with the manager kprobe
411 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
413 copy_kprobe(p, ap);
414 flush_insn_slot(ap);
415 ap->addr = p->addr;
416 ap->pre_handler = aggr_pre_handler;
417 ap->fault_handler = aggr_fault_handler;
418 if (p->post_handler)
419 ap->post_handler = aggr_post_handler;
420 if (p->break_handler)
421 ap->break_handler = aggr_break_handler;
423 INIT_LIST_HEAD(&ap->list);
424 list_add_rcu(&p->list, &ap->list);
426 hlist_replace_rcu(&p->hlist, &ap->hlist);
430 * This is the second or subsequent kprobe at the address - handle
431 * the intricacies
433 static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
434 struct kprobe *p)
436 int ret = 0;
437 struct kprobe *ap;
439 if (old_p->pre_handler == aggr_pre_handler) {
440 copy_kprobe(old_p, p);
441 ret = add_new_kprobe(old_p, p);
442 } else {
443 ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
444 if (!ap)
445 return -ENOMEM;
446 add_aggr_kprobe(ap, old_p);
447 copy_kprobe(ap, p);
448 ret = add_new_kprobe(ap, p);
450 return ret;
453 static int __kprobes in_kprobes_functions(unsigned long addr)
455 if (addr >= (unsigned long)__kprobes_text_start
456 && addr < (unsigned long)__kprobes_text_end)
457 return -EINVAL;
458 return 0;
461 static int __kprobes __register_kprobe(struct kprobe *p,
462 unsigned long called_from)
464 int ret = 0;
465 struct kprobe *old_p;
466 struct module *probed_mod;
469 * If we have a symbol_name argument look it up,
470 * and add it to the address. That way the addr
471 * field can either be global or relative to a symbol.
473 if (p->symbol_name) {
474 if (p->addr)
475 return -EINVAL;
476 kprobe_lookup_name(p->symbol_name, p->addr);
479 if (!p->addr)
480 return -EINVAL;
481 p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset);
483 if ((!kernel_text_address((unsigned long) p->addr)) ||
484 in_kprobes_functions((unsigned long) p->addr))
485 return -EINVAL;
487 p->mod_refcounted = 0;
488 /* Check are we probing a module */
489 if ((probed_mod = module_text_address((unsigned long) p->addr))) {
490 struct module *calling_mod = module_text_address(called_from);
491 /* We must allow modules to probe themself and
492 * in this case avoid incrementing the module refcount,
493 * so as to allow unloading of self probing modules.
495 if (calling_mod && (calling_mod != probed_mod)) {
496 if (unlikely(!try_module_get(probed_mod)))
497 return -EINVAL;
498 p->mod_refcounted = 1;
499 } else
500 probed_mod = NULL;
503 p->nmissed = 0;
504 mutex_lock(&kprobe_mutex);
505 old_p = get_kprobe(p->addr);
506 if (old_p) {
507 ret = register_aggr_kprobe(old_p, p);
508 if (!ret)
509 atomic_inc(&kprobe_count);
510 goto out;
513 if ((ret = arch_prepare_kprobe(p)) != 0)
514 goto out;
516 INIT_HLIST_NODE(&p->hlist);
517 hlist_add_head_rcu(&p->hlist,
518 &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
520 if (atomic_add_return(1, &kprobe_count) == \
521 (ARCH_INACTIVE_KPROBE_COUNT + 1))
522 register_page_fault_notifier(&kprobe_page_fault_nb);
524 arch_arm_kprobe(p);
526 out:
527 mutex_unlock(&kprobe_mutex);
529 if (ret && probed_mod)
530 module_put(probed_mod);
531 return ret;
534 int __kprobes register_kprobe(struct kprobe *p)
536 return __register_kprobe(p,
537 (unsigned long)__builtin_return_address(0));
540 void __kprobes unregister_kprobe(struct kprobe *p)
542 struct module *mod;
543 struct kprobe *old_p, *list_p;
544 int cleanup_p;
546 mutex_lock(&kprobe_mutex);
547 old_p = get_kprobe(p->addr);
548 if (unlikely(!old_p)) {
549 mutex_unlock(&kprobe_mutex);
550 return;
552 if (p != old_p) {
553 list_for_each_entry_rcu(list_p, &old_p->list, list)
554 if (list_p == p)
555 /* kprobe p is a valid probe */
556 goto valid_p;
557 mutex_unlock(&kprobe_mutex);
558 return;
560 valid_p:
561 if ((old_p == p) || ((old_p->pre_handler == aggr_pre_handler) &&
562 (p->list.next == &old_p->list) &&
563 (p->list.prev == &old_p->list))) {
564 /* Only probe on the hash list */
565 arch_disarm_kprobe(p);
566 hlist_del_rcu(&old_p->hlist);
567 cleanup_p = 1;
568 } else {
569 list_del_rcu(&p->list);
570 cleanup_p = 0;
573 mutex_unlock(&kprobe_mutex);
575 synchronize_sched();
576 if (p->mod_refcounted &&
577 (mod = module_text_address((unsigned long)p->addr)))
578 module_put(mod);
580 if (cleanup_p) {
581 if (p != old_p) {
582 list_del_rcu(&p->list);
583 kfree(old_p);
585 arch_remove_kprobe(p);
586 } else {
587 mutex_lock(&kprobe_mutex);
588 if (p->break_handler)
589 old_p->break_handler = NULL;
590 if (p->post_handler){
591 list_for_each_entry_rcu(list_p, &old_p->list, list){
592 if (list_p->post_handler){
593 cleanup_p = 2;
594 break;
597 if (cleanup_p == 0)
598 old_p->post_handler = NULL;
600 mutex_unlock(&kprobe_mutex);
603 /* Call unregister_page_fault_notifier()
604 * if no probes are active
606 mutex_lock(&kprobe_mutex);
607 if (atomic_add_return(-1, &kprobe_count) == \
608 ARCH_INACTIVE_KPROBE_COUNT)
609 unregister_page_fault_notifier(&kprobe_page_fault_nb);
610 mutex_unlock(&kprobe_mutex);
611 return;
614 static struct notifier_block kprobe_exceptions_nb = {
615 .notifier_call = kprobe_exceptions_notify,
616 .priority = 0x7fffffff /* we need to be notified first */
620 int __kprobes register_jprobe(struct jprobe *jp)
622 /* Todo: Verify probepoint is a function entry point */
623 jp->kp.pre_handler = setjmp_pre_handler;
624 jp->kp.break_handler = longjmp_break_handler;
626 return __register_kprobe(&jp->kp,
627 (unsigned long)__builtin_return_address(0));
630 void __kprobes unregister_jprobe(struct jprobe *jp)
632 unregister_kprobe(&jp->kp);
635 #ifdef ARCH_SUPPORTS_KRETPROBES
638 * This kprobe pre_handler is registered with every kretprobe. When probe
639 * hits it will set up the return probe.
641 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
642 struct pt_regs *regs)
644 struct kretprobe *rp = container_of(p, struct kretprobe, kp);
645 unsigned long flags = 0;
647 /*TODO: consider to only swap the RA after the last pre_handler fired */
648 spin_lock_irqsave(&kretprobe_lock, flags);
649 arch_prepare_kretprobe(rp, regs);
650 spin_unlock_irqrestore(&kretprobe_lock, flags);
651 return 0;
654 int __kprobes register_kretprobe(struct kretprobe *rp)
656 int ret = 0;
657 struct kretprobe_instance *inst;
658 int i;
660 rp->kp.pre_handler = pre_handler_kretprobe;
661 rp->kp.post_handler = NULL;
662 rp->kp.fault_handler = NULL;
663 rp->kp.break_handler = NULL;
665 /* Pre-allocate memory for max kretprobe instances */
666 if (rp->maxactive <= 0) {
667 #ifdef CONFIG_PREEMPT
668 rp->maxactive = max(10, 2 * NR_CPUS);
669 #else
670 rp->maxactive = NR_CPUS;
671 #endif
673 INIT_HLIST_HEAD(&rp->used_instances);
674 INIT_HLIST_HEAD(&rp->free_instances);
675 for (i = 0; i < rp->maxactive; i++) {
676 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
677 if (inst == NULL) {
678 free_rp_inst(rp);
679 return -ENOMEM;
681 INIT_HLIST_NODE(&inst->uflist);
682 hlist_add_head(&inst->uflist, &rp->free_instances);
685 rp->nmissed = 0;
686 /* Establish function entry probe point */
687 if ((ret = __register_kprobe(&rp->kp,
688 (unsigned long)__builtin_return_address(0))) != 0)
689 free_rp_inst(rp);
690 return ret;
693 #else /* ARCH_SUPPORTS_KRETPROBES */
695 int __kprobes register_kretprobe(struct kretprobe *rp)
697 return -ENOSYS;
700 #endif /* ARCH_SUPPORTS_KRETPROBES */
702 void __kprobes unregister_kretprobe(struct kretprobe *rp)
704 unsigned long flags;
705 struct kretprobe_instance *ri;
707 unregister_kprobe(&rp->kp);
708 /* No race here */
709 spin_lock_irqsave(&kretprobe_lock, flags);
710 while ((ri = get_used_rp_inst(rp)) != NULL) {
711 ri->rp = NULL;
712 hlist_del(&ri->uflist);
714 spin_unlock_irqrestore(&kretprobe_lock, flags);
715 free_rp_inst(rp);
718 static int __init init_kprobes(void)
720 int i, err = 0;
722 /* FIXME allocate the probe table, currently defined statically */
723 /* initialize all list heads */
724 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
725 INIT_HLIST_HEAD(&kprobe_table[i]);
726 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
728 atomic_set(&kprobe_count, 0);
730 err = arch_init_kprobes();
731 if (!err)
732 err = register_die_notifier(&kprobe_exceptions_nb);
734 return err;
737 __initcall(init_kprobes);
739 EXPORT_SYMBOL_GPL(register_kprobe);
740 EXPORT_SYMBOL_GPL(unregister_kprobe);
741 EXPORT_SYMBOL_GPL(register_jprobe);
742 EXPORT_SYMBOL_GPL(unregister_jprobe);
743 EXPORT_SYMBOL_GPL(jprobe_return);
744 EXPORT_SYMBOL_GPL(register_kretprobe);
745 EXPORT_SYMBOL_GPL(unregister_kretprobe);