569079ec4ff004f010d64df7d746b0a01caff44c
[linux-2.6.git] / arch / s390 / kernel / kprobes.c
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
33 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
34 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
35
36 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
37
38 int __kprobes arch_prepare_kprobe(struct kprobe *p)
39 {
40         /* Make sure the probe isn't going on a difficult instruction */
41         if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
42                 return -EINVAL;
43
44         if ((unsigned long)p->addr & 0x01)
45                 return -EINVAL;
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
58 int __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
79 void __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) >> 6) {
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
155 static 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
189 void __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(swap_instruction, &args, NULL);
201         kcb->kprobe_status = status;
202 }
203
204 void __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(swap_instruction, &args, NULL);
216         kcb->kprobe_status = status;
217 }
218
219 void __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
226 static 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
244 static 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
253 static 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
262 static 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 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
274                                         struct pt_regs *regs)
275 {
276         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
277
278         /* Replace the return addr with trampoline addr */
279         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
280 }
281
282 static int __kprobes kprobe_handler(struct pt_regs *regs)
283 {
284         struct kprobe *p;
285         int ret = 0;
286         unsigned long *addr = (unsigned long *)
287                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
288         struct kprobe_ctlblk *kcb;
289
290         /*
291          * We don't want to be preempted for the entire
292          * duration of kprobe processing
293          */
294         preempt_disable();
295         kcb = get_kprobe_ctlblk();
296
297         /* Check we're not actually recursing */
298         if (kprobe_running()) {
299                 p = get_kprobe(addr);
300                 if (p) {
301                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
302                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
303                                 regs->psw.mask &= ~PSW_MASK_PER;
304                                 regs->psw.mask |= kcb->kprobe_saved_imask;
305                                 goto no_kprobe;
306                         }
307                         /* We have reentered the kprobe_handler(), since
308                          * another probe was hit while within the handler.
309                          * We here save the original kprobes variables and
310                          * just single step on the instruction of the new probe
311                          * without calling any user handlers.
312                          */
313                         save_previous_kprobe(kcb);
314                         set_current_kprobe(p, regs, kcb);
315                         kprobes_inc_nmissed_count(p);
316                         prepare_singlestep(p, regs);
317                         kcb->kprobe_status = KPROBE_REENTER;
318                         return 1;
319                 } else {
320                         p = __get_cpu_var(current_kprobe);
321                         if (p->break_handler && p->break_handler(p, regs)) {
322                                 goto ss_probe;
323                         }
324                 }
325                 goto no_kprobe;
326         }
327
328         p = get_kprobe(addr);
329         if (!p)
330                 /*
331                  * No kprobe at this address. The fault has not been
332                  * caused by a kprobe breakpoint. The race of breakpoint
333                  * vs. kprobe remove does not exist because on s390 we
334                  * use stop_machine to arm/disarm the breakpoints.
335                  */
336                 goto no_kprobe;
337
338         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
339         set_current_kprobe(p, regs, kcb);
340         if (p->pre_handler && p->pre_handler(p, regs))
341                 /* handler has already set things up, so skip ss setup */
342                 return 1;
343
344 ss_probe:
345         prepare_singlestep(p, regs);
346         kcb->kprobe_status = KPROBE_HIT_SS;
347         return 1;
348
349 no_kprobe:
350         preempt_enable_no_resched();
351         return ret;
352 }
353
354 /*
355  * Function return probe trampoline:
356  *      - init_kprobes() establishes a probepoint here
357  *      - When the probed function returns, this probe
358  *              causes the handlers to fire
359  */
360 static void __used kretprobe_trampoline_holder(void)
361 {
362         asm volatile(".global kretprobe_trampoline\n"
363                      "kretprobe_trampoline: bcr 0,0\n");
364 }
365
366 /*
367  * Called when the probe at kretprobe trampoline is hit
368  */
369 static int __kprobes trampoline_probe_handler(struct kprobe *p,
370                                               struct pt_regs *regs)
371 {
372         struct kretprobe_instance *ri = NULL;
373         struct hlist_head *head, empty_rp;
374         struct hlist_node *node, *tmp;
375         unsigned long flags, orig_ret_address = 0;
376         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
377
378         INIT_HLIST_HEAD(&empty_rp);
379         kretprobe_hash_lock(current, &head, &flags);
380
381         /*
382          * It is possible to have multiple instances associated with a given
383          * task either because an multiple functions in the call path
384          * have a return probe installed on them, and/or more then one return
385          * return probe was registered for a target function.
386          *
387          * We can handle this because:
388          *     - instances are always inserted at the head of the list
389          *     - when multiple return probes are registered for the same
390          *       function, the first instance's ret_addr will point to the
391          *       real return address, and all the rest will point to
392          *       kretprobe_trampoline
393          */
394         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
395                 if (ri->task != current)
396                         /* another task is sharing our hash bucket */
397                         continue;
398
399                 if (ri->rp && ri->rp->handler)
400                         ri->rp->handler(ri, regs);
401
402                 orig_ret_address = (unsigned long)ri->ret_addr;
403                 recycle_rp_inst(ri, &empty_rp);
404
405                 if (orig_ret_address != trampoline_address) {
406                         /*
407                          * This is the real return address. Any other
408                          * instances associated with this task are for
409                          * other calls deeper on the call stack
410                          */
411                         break;
412                 }
413         }
414         kretprobe_assert(ri, orig_ret_address, trampoline_address);
415         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
416
417         reset_current_kprobe();
418         kretprobe_hash_unlock(current, &flags);
419         preempt_enable_no_resched();
420
421         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
422                 hlist_del(&ri->hlist);
423                 kfree(ri);
424         }
425         /*
426          * By returning a non-zero value, we are telling
427          * kprobe_handler() that we don't want the post_handler
428          * to run (and have re-enabled preemption)
429          */
430         return 1;
431 }
432
433 /*
434  * Called after single-stepping.  p->addr is the address of the
435  * instruction whose first byte has been replaced by the "breakpoint"
436  * instruction.  To avoid the SMP problems that can occur when we
437  * temporarily put back the original opcode to single-step, we
438  * single-stepped a copy of the instruction.  The address of this
439  * copy is p->ainsn.insn.
440  */
441 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
442 {
443         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
444
445         regs->psw.addr &= PSW_ADDR_INSN;
446
447         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
448                 regs->psw.addr = (unsigned long)p->addr +
449                                 ((unsigned long)regs->psw.addr -
450                                  (unsigned long)p->ainsn.insn);
451
452         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
453                 if ((unsigned long)regs->psw.addr -
454                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
455                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
456
457         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
458                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
459                                                 (regs->gprs[p->ainsn.reg] -
460                                                 (unsigned long)p->ainsn.insn))
461                                                 | PSW_ADDR_AMODE;
462
463         regs->psw.addr |= PSW_ADDR_AMODE;
464         /* turn off PER mode */
465         regs->psw.mask &= ~PSW_MASK_PER;
466         /* Restore the original per control regs */
467         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
468         regs->psw.mask |= kcb->kprobe_saved_imask;
469 }
470
471 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
472 {
473         struct kprobe *cur = kprobe_running();
474         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
475
476         if (!cur)
477                 return 0;
478
479         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
480                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
481                 cur->post_handler(cur, regs, 0);
482         }
483
484         resume_execution(cur, regs);
485
486         /*Restore back the original saved kprobes variables and continue. */
487         if (kcb->kprobe_status == KPROBE_REENTER) {
488                 restore_previous_kprobe(kcb);
489                 goto out;
490         }
491         reset_current_kprobe();
492 out:
493         preempt_enable_no_resched();
494
495         /*
496          * if somebody else is singlestepping across a probe point, psw mask
497          * will have PER set, in which case, continue the remaining processing
498          * of do_single_step, as if this is not a probe hit.
499          */
500         if (regs->psw.mask & PSW_MASK_PER) {
501                 return 0;
502         }
503
504         return 1;
505 }
506
507 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
508 {
509         struct kprobe *cur = kprobe_running();
510         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
511         const struct exception_table_entry *entry;
512
513         switch(kcb->kprobe_status) {
514         case KPROBE_SWAP_INST:
515                 /* We are here because the instruction replacement failed */
516                 return 0;
517         case KPROBE_HIT_SS:
518         case KPROBE_REENTER:
519                 /*
520                  * We are here because the instruction being single
521                  * stepped caused a page fault. We reset the current
522                  * kprobe and the nip points back to the probe address
523                  * and allow the page fault handler to continue as a
524                  * normal page fault.
525                  */
526                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
527                 regs->psw.mask &= ~PSW_MASK_PER;
528                 regs->psw.mask |= kcb->kprobe_saved_imask;
529                 if (kcb->kprobe_status == KPROBE_REENTER)
530                         restore_previous_kprobe(kcb);
531                 else
532                         reset_current_kprobe();
533                 preempt_enable_no_resched();
534                 break;
535         case KPROBE_HIT_ACTIVE:
536         case KPROBE_HIT_SSDONE:
537                 /*
538                  * We increment the nmissed count for accounting,
539                  * we can also use npre/npostfault count for accouting
540                  * these specific fault cases.
541                  */
542                 kprobes_inc_nmissed_count(cur);
543
544                 /*
545                  * We come here because instructions in the pre/post
546                  * handler caused the page_fault, this could happen
547                  * if handler tries to access user space by
548                  * copy_from_user(), get_user() etc. Let the
549                  * user-specified handler try to fix it first.
550                  */
551                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
552                         return 1;
553
554                 /*
555                  * In case the user-specified fault handler returned
556                  * zero, try to fix up.
557                  */
558                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
559                 if (entry) {
560                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
561                         return 1;
562                 }
563
564                 /*
565                  * fixup_exception() could not handle it,
566                  * Let do_page_fault() fix it.
567                  */
568                 break;
569         default:
570                 break;
571         }
572         return 0;
573 }
574
575 /*
576  * Wrapper routine to for handling exceptions.
577  */
578 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
579                                        unsigned long val, void *data)
580 {
581         struct die_args *args = (struct die_args *)data;
582         int ret = NOTIFY_DONE;
583
584         switch (val) {
585         case DIE_BPT:
586                 if (kprobe_handler(args->regs))
587                         ret = NOTIFY_STOP;
588                 break;
589         case DIE_SSTEP:
590                 if (post_kprobe_handler(args->regs))
591                         ret = NOTIFY_STOP;
592                 break;
593         case DIE_TRAP:
594                 /* kprobe_running() needs smp_processor_id() */
595                 preempt_disable();
596                 if (kprobe_running() &&
597                     kprobe_fault_handler(args->regs, args->trapnr))
598                         ret = NOTIFY_STOP;
599                 preempt_enable();
600                 break;
601         default:
602                 break;
603         }
604         return ret;
605 }
606
607 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
608 {
609         struct jprobe *jp = container_of(p, struct jprobe, kp);
610         unsigned long addr;
611         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
612
613         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
614
615         /* setup return addr to the jprobe handler routine */
616         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
617
618         /* r14 is the function return address */
619         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
620         /* r15 is the stack pointer */
621         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
622         addr = (unsigned long)kcb->jprobe_saved_r15;
623
624         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
625                MIN_STACK_SIZE(addr));
626         return 1;
627 }
628
629 void __kprobes jprobe_return(void)
630 {
631         asm volatile(".word 0x0002");
632 }
633
634 void __kprobes jprobe_return_end(void)
635 {
636         asm volatile("bcr 0,0");
637 }
638
639 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
640 {
641         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
642         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
643
644         /* Put the regs back */
645         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
646         /* put the stack back */
647         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
648                MIN_STACK_SIZE(stack_addr));
649         preempt_enable_no_resched();
650         return 1;
651 }
652
653 static struct kprobe trampoline_p = {
654         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
655         .pre_handler = trampoline_probe_handler
656 };
657
658 int __init arch_init_kprobes(void)
659 {
660         return register_kprobe(&trampoline_p);
661 }
662
663 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
664 {
665         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
666                 return 1;
667         return 0;
668 }