1/*
2 *  Kernel Probes (KProbes)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2006
19 *
20 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
21 */
22
23#include <linux/kprobes.h>
24#include <linux/ptrace.h>
25#include <linux/preempt.h>
26#include <linux/stop_machine.h>
27#include <linux/kdebug.h>
28#include <asm/cacheflush.h>
29#include <asm/sections.h>
30#include <asm/uaccess.h>
31#include <linux/module.h>
32
33DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
34DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
35
36int __kprobes arch_prepare_kprobe(struct kprobe *p)
37{
38	/* Make sure the probe isn't going on a difficult instruction */
39	if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
40		return -EINVAL;
41
42	if ((unsigned long)p->addr & 0x01) {
43		printk("Attempt to register kprobe at an unaligned address\n");
44		return -EINVAL;
45		}
46
47	/* Use the get_insn_slot() facility for correctness */
48	if (!(p->ainsn.insn = get_insn_slot()))
49		return -ENOMEM;
50
51	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
52
53	get_instruction_type(&p->ainsn);
54	p->opcode = *p->addr;
55	return 0;
56}
57
58int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
59{
60	switch (*(__u8 *) instruction) {
61	case 0x0c:	/* bassm */
62	case 0x0b:	/* bsm	 */
63	case 0x83:	/* diag  */
64	case 0x44:	/* ex	 */
65		return -EINVAL;
66	}
67	switch (*(__u16 *) instruction) {
68	case 0x0101:	/* pr	 */
69	case 0xb25a:	/* bsa	 */
70	case 0xb240:	/* bakr  */
71	case 0xb258:	/* bsg	 */
72	case 0xb218:	/* pc	 */
73	case 0xb228:	/* pt	 */
74		return -EINVAL;
75	}
76	return 0;
77}
78
79void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
80{
81	/* default fixup method */
82	ainsn->fixup = FIXUP_PSW_NORMAL;
83
84	/* save r1 operand */
85	ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
86
87	/* save the instruction length (pop 5-5) in bytes */
88	switch (*(__u8 *) (ainsn->insn) >> 4) {
89	case 0:
90		ainsn->ilen = 2;
91		break;
92	case 1:
93	case 2:
94		ainsn->ilen = 4;
95		break;
96	case 3:
97		ainsn->ilen = 6;
98		break;
99	}
100
101	switch (*(__u8 *) ainsn->insn) {
102	case 0x05:	/* balr	*/
103	case 0x0d:	/* basr */
104		ainsn->fixup = FIXUP_RETURN_REGISTER;
105		/* if r2 = 0, no branch will be taken */
106		if ((*ainsn->insn & 0x0f) == 0)
107			ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
108		break;
109	case 0x06:	/* bctr	*/
110	case 0x07:	/* bcr	*/
111		ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
112		break;
113	case 0x45:	/* bal	*/
114	case 0x4d:	/* bas	*/
115		ainsn->fixup = FIXUP_RETURN_REGISTER;
116		break;
117	case 0x47:	/* bc	*/
118	case 0x46:	/* bct	*/
119	case 0x86:	/* bxh	*/
120	case 0x87:	/* bxle	*/
121		ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
122		break;
123	case 0x82:	/* lpsw	*/
124		ainsn->fixup = FIXUP_NOT_REQUIRED;
125		break;
126	case 0xb2:	/* lpswe */
127		if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
128			ainsn->fixup = FIXUP_NOT_REQUIRED;
129		}
130		break;
131	case 0xa7:	/* bras	*/
132		if ((*ainsn->insn & 0x0f) == 0x05) {
133			ainsn->fixup |= FIXUP_RETURN_REGISTER;
134		}
135		break;
136	case 0xc0:
137		if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
138			|| (*ainsn->insn & 0x0f) == 0x05) /* brasl */
139		ainsn->fixup |= FIXUP_RETURN_REGISTER;
140		break;
141	case 0xeb:
142		if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||	/* bxhg  */
143			*(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
144			ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
145		}
146		break;
147	case 0xe3:	/* bctg	*/
148		if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
149			ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
150		}
151		break;
152	}
153}
154
155static int __kprobes swap_instruction(void *aref)
156{
157	struct ins_replace_args *args = aref;
158	u32 *addr;
159	u32 instr;
160	int err = -EFAULT;
161
162	/*
163	 * Text segment is read-only, hence we use stura to bypass dynamic
164	 * address translation to exchange the instruction. Since stura
165	 * always operates on four bytes, but we only want to exchange two
166	 * bytes do some calculations to get things right. In addition we
167	 * shall not cross any page boundaries (vmalloc area!) when writing
168	 * the new instruction.
169	 */
170	addr = (u32 *)((unsigned long)args->ptr & -4UL);
171	if ((unsigned long)args->ptr & 2)
172		instr = ((*addr) & 0xffff0000) | args->new;
173	else
174		instr = ((*addr) & 0x0000ffff) | args->new << 16;
175
176	asm volatile(
177		"	lra	%1,0(%1)\n"
178		"0:	stura	%2,%1\n"
179		"1:	la	%0,0\n"
180		"2:\n"
181		EX_TABLE(0b,2b)
182		: "+d" (err)
183		: "a" (addr), "d" (instr)
184		: "memory", "cc");
185
186	return err;
187}
188
189void __kprobes arch_arm_kprobe(struct kprobe *p)
190{
191	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
192	unsigned long status = kcb->kprobe_status;
193	struct ins_replace_args args;
194
195	args.ptr = p->addr;
196	args.old = p->opcode;
197	args.new = BREAKPOINT_INSTRUCTION;
198
199	kcb->kprobe_status = KPROBE_SWAP_INST;
200	stop_machine_run(swap_instruction, &args, NR_CPUS);
201	kcb->kprobe_status = status;
202}
203
204void __kprobes arch_disarm_kprobe(struct kprobe *p)
205{
206	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
207	unsigned long status = kcb->kprobe_status;
208	struct ins_replace_args args;
209
210	args.ptr = p->addr;
211	args.old = BREAKPOINT_INSTRUCTION;
212	args.new = p->opcode;
213
214	kcb->kprobe_status = KPROBE_SWAP_INST;
215	stop_machine_run(swap_instruction, &args, NR_CPUS);
216	kcb->kprobe_status = status;
217}
218
219void __kprobes arch_remove_kprobe(struct kprobe *p)
220{
221	mutex_lock(&kprobe_mutex);
222	free_insn_slot(p->ainsn.insn, 0);
223	mutex_unlock(&kprobe_mutex);
224}
225
226static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
227{
228	per_cr_bits kprobe_per_regs[1];
229
230	memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
231	regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
232
233	/* Set up the per control reg info, will pass to lctl */
234	kprobe_per_regs[0].em_instruction_fetch = 1;
235	kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
236	kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
237
238	/* Set the PER control regs, turns on single step for this address */
239	__ctl_load(kprobe_per_regs, 9, 11);
240	regs->psw.mask |= PSW_MASK_PER;
241	regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
242}
243
244static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
245{
246	kcb->prev_kprobe.kp = kprobe_running();
247	kcb->prev_kprobe.status = kcb->kprobe_status;
248	kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
249	memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
250					sizeof(kcb->kprobe_saved_ctl));
251}
252
253static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
254{
255	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
256	kcb->kprobe_status = kcb->prev_kprobe.status;
257	kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
258	memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
259					sizeof(kcb->kprobe_saved_ctl));
260}
261
262static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
263						struct kprobe_ctlblk *kcb)
264{
265	__get_cpu_var(current_kprobe) = p;
266	/* Save the interrupt and per flags */
267	kcb->kprobe_saved_imask = regs->psw.mask &
268	    (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
269	/* Save the control regs that govern PER */
270	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
271}
272
273/* Called with kretprobe_lock held */
274void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
275					struct pt_regs *regs)
276{
277	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
278
279	/* Replace the return addr with trampoline addr */
280	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
281}
282
283static int __kprobes kprobe_handler(struct pt_regs *regs)
284{
285	struct kprobe *p;
286	int ret = 0;
287	unsigned long *addr = (unsigned long *)
288		((regs->psw.addr & PSW_ADDR_INSN) - 2);
289	struct kprobe_ctlblk *kcb;
290
291	/*
292	 * We don't want to be preempted for the entire
293	 * duration of kprobe processing
294	 */
295	preempt_disable();
296	kcb = get_kprobe_ctlblk();
297
298	/* Check we're not actually recursing */
299	if (kprobe_running()) {
300		p = get_kprobe(addr);
301		if (p) {
302			if (kcb->kprobe_status == KPROBE_HIT_SS &&
303			    *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
304				regs->psw.mask &= ~PSW_MASK_PER;
305				regs->psw.mask |= kcb->kprobe_saved_imask;
306				goto no_kprobe;
307			}
308			/* We have reentered the kprobe_handler(), since
309			 * another probe was hit while within the handler.
310			 * We here save the original kprobes variables and
311			 * just single step on the instruction of the new probe
312			 * without calling any user handlers.
313			 */
314			save_previous_kprobe(kcb);
315			set_current_kprobe(p, regs, kcb);
316			kprobes_inc_nmissed_count(p);
317			prepare_singlestep(p, regs);
318			kcb->kprobe_status = KPROBE_REENTER;
319			return 1;
320		} else {
321			p = __get_cpu_var(current_kprobe);
322			if (p->break_handler && p->break_handler(p, regs)) {
323				goto ss_probe;
324			}
325		}
326		goto no_kprobe;
327	}
328
329	p = get_kprobe(addr);
330	if (!p)
331		/*
332		 * No kprobe at this address. The fault has not been
333		 * caused by a kprobe breakpoint. The race of breakpoint
334		 * vs. kprobe remove does not exist because on s390 we
335		 * use stop_machine_run to arm/disarm the breakpoints.
336		 */
337		goto no_kprobe;
338
339	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
340	set_current_kprobe(p, regs, kcb);
341	if (p->pre_handler && p->pre_handler(p, regs))
342		/* handler has already set things up, so skip ss setup */
343		return 1;
344
345ss_probe:
346	prepare_singlestep(p, regs);
347	kcb->kprobe_status = KPROBE_HIT_SS;
348	return 1;
349
350no_kprobe:
351	preempt_enable_no_resched();
352	return ret;
353}
354
355/*
356 * Function return probe trampoline:
357 *	- init_kprobes() establishes a probepoint here
358 *	- When the probed function returns, this probe
359 *		causes the handlers to fire
360 */
361void kretprobe_trampoline_holder(void)
362{
363	asm volatile(".global kretprobe_trampoline\n"
364		     "kretprobe_trampoline: bcr 0,0\n");
365}
366
367/*
368 * Called when the probe at kretprobe trampoline is hit
369 */
370static int __kprobes trampoline_probe_handler(struct kprobe *p,
371					      struct pt_regs *regs)
372{
373	struct kretprobe_instance *ri = NULL;
374	struct hlist_head *head, empty_rp;
375	struct hlist_node *node, *tmp;
376	unsigned long flags, orig_ret_address = 0;
377	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
378
379	INIT_HLIST_HEAD(&empty_rp);
380	spin_lock_irqsave(&kretprobe_lock, flags);
381	head = kretprobe_inst_table_head(current);
382
383	/*
384	 * It is possible to have multiple instances associated with a given
385	 * task either because an multiple functions in the call path
386	 * have a return probe installed on them, and/or more then one return
387	 * return probe was registered for a target function.
388	 *
389	 * We can handle this because:
390	 *     - instances are always inserted at the head of the list
391	 *     - when multiple return probes are registered for the same
392	 *	 function, the first instance's ret_addr will point to the
393	 *	 real return address, and all the rest will point to
394	 *	 kretprobe_trampoline
395	 */
396	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
397		if (ri->task != current)
398			/* another task is sharing our hash bucket */
399			continue;
400
401		if (ri->rp && ri->rp->handler)
402			ri->rp->handler(ri, regs);
403
404		orig_ret_address = (unsigned long)ri->ret_addr;
405		recycle_rp_inst(ri, &empty_rp);
406
407		if (orig_ret_address != trampoline_address) {
408			/*
409			 * This is the real return address. Any other
410			 * instances associated with this task are for
411			 * other calls deeper on the call stack
412			 */
413			break;
414		}
415	}
416	kretprobe_assert(ri, orig_ret_address, trampoline_address);
417	regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
418
419	reset_current_kprobe();
420	spin_unlock_irqrestore(&kretprobe_lock, flags);
421	preempt_enable_no_resched();
422
423	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
424		hlist_del(&ri->hlist);
425		kfree(ri);
426	}
427	/*
428	 * By returning a non-zero value, we are telling
429	 * kprobe_handler() that we don't want the post_handler
430	 * to run (and have re-enabled preemption)
431	 */
432	return 1;
433}
434
435/*
436 * Called after single-stepping.  p->addr is the address of the
437 * instruction whose first byte has been replaced by the "breakpoint"
438 * instruction.  To avoid the SMP problems that can occur when we
439 * temporarily put back the original opcode to single-step, we
440 * single-stepped a copy of the instruction.  The address of this
441 * copy is p->ainsn.insn.
442 */
443static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
444{
445	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
446
447	regs->psw.addr &= PSW_ADDR_INSN;
448
449	if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
450		regs->psw.addr = (unsigned long)p->addr +
451				((unsigned long)regs->psw.addr -
452				 (unsigned long)p->ainsn.insn);
453
454	if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
455		if ((unsigned long)regs->psw.addr -
456		    (unsigned long)p->ainsn.insn == p->ainsn.ilen)
457			regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
458
459	if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
460		regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
461						(regs->gprs[p->ainsn.reg] -
462						(unsigned long)p->ainsn.insn))
463						| PSW_ADDR_AMODE;
464
465	regs->psw.addr |= PSW_ADDR_AMODE;
466	/* turn off PER mode */
467	regs->psw.mask &= ~PSW_MASK_PER;
468	/* Restore the original per control regs */
469	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
470	regs->psw.mask |= kcb->kprobe_saved_imask;
471}
472
473static int __kprobes post_kprobe_handler(struct pt_regs *regs)
474{
475	struct kprobe *cur = kprobe_running();
476	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
477
478	if (!cur)
479		return 0;
480
481	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
482		kcb->kprobe_status = KPROBE_HIT_SSDONE;
483		cur->post_handler(cur, regs, 0);
484	}
485
486	resume_execution(cur, regs);
487
488	/*Restore back the original saved kprobes variables and continue. */
489	if (kcb->kprobe_status == KPROBE_REENTER) {
490		restore_previous_kprobe(kcb);
491		goto out;
492	}
493	reset_current_kprobe();
494out:
495	preempt_enable_no_resched();
496
497	/*
498	 * if somebody else is singlestepping across a probe point, psw mask
499	 * will have PER set, in which case, continue the remaining processing
500	 * of do_single_step, as if this is not a probe hit.
501	 */
502	if (regs->psw.mask & PSW_MASK_PER) {
503		return 0;
504	}
505
506	return 1;
507}
508
509int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
510{
511	struct kprobe *cur = kprobe_running();
512	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
513	const struct exception_table_entry *entry;
514
515	switch(kcb->kprobe_status) {
516	case KPROBE_SWAP_INST:
517		/* We are here because the instruction replacement failed */
518		return 0;
519	case KPROBE_HIT_SS:
520	case KPROBE_REENTER:
521		/*
522		 * We are here because the instruction being single
523		 * stepped caused a page fault. We reset the current
524		 * kprobe and the nip points back to the probe address
525		 * and allow the page fault handler to continue as a
526		 * normal page fault.
527		 */
528		regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
529		regs->psw.mask &= ~PSW_MASK_PER;
530		regs->psw.mask |= kcb->kprobe_saved_imask;
531		if (kcb->kprobe_status == KPROBE_REENTER)
532			restore_previous_kprobe(kcb);
533		else
534			reset_current_kprobe();
535		preempt_enable_no_resched();
536		break;
537	case KPROBE_HIT_ACTIVE:
538	case KPROBE_HIT_SSDONE:
539		/*
540		 * We increment the nmissed count for accounting,
541		 * we can also use npre/npostfault count for accouting
542		 * these specific fault cases.
543		 */
544		kprobes_inc_nmissed_count(cur);
545
546		/*
547		 * We come here because instructions in the pre/post
548		 * handler caused the page_fault, this could happen
549		 * if handler tries to access user space by
550		 * copy_from_user(), get_user() etc. Let the
551		 * user-specified handler try to fix it first.
552		 */
553		if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
554			return 1;
555
556		/*
557		 * In case the user-specified fault handler returned
558		 * zero, try to fix up.
559		 */
560		entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
561		if (entry) {
562			regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
563			return 1;
564		}
565
566		/*
567		 * fixup_exception() could not handle it,
568		 * Let do_page_fault() fix it.
569		 */
570		break;
571	default:
572		break;
573	}
574	return 0;
575}
576
577/*
578 * Wrapper routine to for handling exceptions.
579 */
580int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
581				       unsigned long val, void *data)
582{
583	struct die_args *args = (struct die_args *)data;
584	int ret = NOTIFY_DONE;
585
586	switch (val) {
587	case DIE_BPT:
588		if (kprobe_handler(args->regs))
589			ret = NOTIFY_STOP;
590		break;
591	case DIE_SSTEP:
592		if (post_kprobe_handler(args->regs))
593			ret = NOTIFY_STOP;
594		break;
595	case DIE_TRAP:
596		/* kprobe_running() needs smp_processor_id() */
597		preempt_disable();
598		if (kprobe_running() &&
599		    kprobe_fault_handler(args->regs, args->trapnr))
600			ret = NOTIFY_STOP;
601		preempt_enable();
602		break;
603	default:
604		break;
605	}
606	return ret;
607}
608
609int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
610{
611	struct jprobe *jp = container_of(p, struct jprobe, kp);
612	unsigned long addr;
613	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
614
615	memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
616
617	/* setup return addr to the jprobe handler routine */
618	regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
619
620	/* r14 is the function return address */
621	kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
622	/* r15 is the stack pointer */
623	kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
624	addr = (unsigned long)kcb->jprobe_saved_r15;
625
626	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
627	       MIN_STACK_SIZE(addr));
628	return 1;
629}
630
631void __kprobes jprobe_return(void)
632{
633	asm volatile(".word 0x0002");
634}
635
636void __kprobes jprobe_return_end(void)
637{
638	asm volatile("bcr 0,0");
639}
640
641int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
642{
643	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
644	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
645
646	/* Put the regs back */
647	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
648	/* put the stack back */
649	memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
650	       MIN_STACK_SIZE(stack_addr));
651	preempt_enable_no_resched();
652	return 1;
653}
654
655static struct kprobe trampoline_p = {
656	.addr = (kprobe_opcode_t *) & kretprobe_trampoline,
657	.pre_handler = trampoline_probe_handler
658};
659
660int __init arch_init_kprobes(void)
661{
662	return register_kprobe(&trampoline_p);
663}
664
665int __kprobes arch_trampoline_kprobe(struct kprobe *p)
666{
667	if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
668		return 1;
669	return 0;
670}
671