[S390] zfcpdump support.
[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 <asm/cacheflush.h>
28 #include <asm/kdebug.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 int __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
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) >> 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
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_run(swap_instruction, &args, NR_CPUS);
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_run(swap_instruction, &args, NR_CPUS);
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 /* Called with kretprobe_lock held */
274 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
275                                         struct pt_regs *regs)
276 {
277         struct kretprobe_instance *ri;
278
279         if ((ri = get_free_rp_inst(rp)) != NULL) {
280                 ri->rp = rp;
281                 ri->task = current;
282                 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
283
284                 /* Replace the return addr with trampoline addr */
285                 regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
286
287                 add_rp_inst(ri);
288         } else {
289                 rp->nmissed++;
290         }
291 }
292
293 static int __kprobes kprobe_handler(struct pt_regs *regs)
294 {
295         struct kprobe *p;
296         int ret = 0;
297         unsigned long *addr = (unsigned long *)
298                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
299         struct kprobe_ctlblk *kcb;
300
301         /*
302          * We don't want to be preempted for the entire
303          * duration of kprobe processing
304          */
305         preempt_disable();
306         kcb = get_kprobe_ctlblk();
307
308         /* Check we're not actually recursing */
309         if (kprobe_running()) {
310                 p = get_kprobe(addr);
311                 if (p) {
312                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
313                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
314                                 regs->psw.mask &= ~PSW_MASK_PER;
315                                 regs->psw.mask |= kcb->kprobe_saved_imask;
316                                 goto no_kprobe;
317                         }
318                         /* We have reentered the kprobe_handler(), since
319                          * another probe was hit while within the handler.
320                          * We here save the original kprobes variables and
321                          * just single step on the instruction of the new probe
322                          * without calling any user handlers.
323                          */
324                         save_previous_kprobe(kcb);
325                         set_current_kprobe(p, regs, kcb);
326                         kprobes_inc_nmissed_count(p);
327                         prepare_singlestep(p, regs);
328                         kcb->kprobe_status = KPROBE_REENTER;
329                         return 1;
330                 } else {
331                         p = __get_cpu_var(current_kprobe);
332                         if (p->break_handler && p->break_handler(p, regs)) {
333                                 goto ss_probe;
334                         }
335                 }
336                 goto no_kprobe;
337         }
338
339         p = get_kprobe(addr);
340         if (!p)
341                 /*
342                  * No kprobe at this address. The fault has not been
343                  * caused by a kprobe breakpoint. The race of breakpoint
344                  * vs. kprobe remove does not exist because on s390 we
345                  * use stop_machine_run to arm/disarm the breakpoints.
346                  */
347                 goto no_kprobe;
348
349         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
350         set_current_kprobe(p, regs, kcb);
351         if (p->pre_handler && p->pre_handler(p, regs))
352                 /* handler has already set things up, so skip ss setup */
353                 return 1;
354
355 ss_probe:
356         prepare_singlestep(p, regs);
357         kcb->kprobe_status = KPROBE_HIT_SS;
358         return 1;
359
360 no_kprobe:
361         preempt_enable_no_resched();
362         return ret;
363 }
364
365 /*
366  * Function return probe trampoline:
367  *      - init_kprobes() establishes a probepoint here
368  *      - When the probed function returns, this probe
369  *              causes the handlers to fire
370  */
371 void kretprobe_trampoline_holder(void)
372 {
373         asm volatile(".global kretprobe_trampoline\n"
374                      "kretprobe_trampoline: bcr 0,0\n");
375 }
376
377 /*
378  * Called when the probe at kretprobe trampoline is hit
379  */
380 static int __kprobes trampoline_probe_handler(struct kprobe *p,
381                                               struct pt_regs *regs)
382 {
383         struct kretprobe_instance *ri = NULL;
384         struct hlist_head *head, empty_rp;
385         struct hlist_node *node, *tmp;
386         unsigned long flags, orig_ret_address = 0;
387         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
388
389         INIT_HLIST_HEAD(&empty_rp);
390         spin_lock_irqsave(&kretprobe_lock, flags);
391         head = kretprobe_inst_table_head(current);
392
393         /*
394          * It is possible to have multiple instances associated with a given
395          * task either because an multiple functions in the call path
396          * have a return probe installed on them, and/or more then one return
397          * return probe was registered for a target function.
398          *
399          * We can handle this because:
400          *     - instances are always inserted at the head of the list
401          *     - when multiple return probes are registered for the same
402          *       function, the first instance's ret_addr will point to the
403          *       real return address, and all the rest will point to
404          *       kretprobe_trampoline
405          */
406         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
407                 if (ri->task != current)
408                         /* another task is sharing our hash bucket */
409                         continue;
410
411                 if (ri->rp && ri->rp->handler)
412                         ri->rp->handler(ri, regs);
413
414                 orig_ret_address = (unsigned long)ri->ret_addr;
415                 recycle_rp_inst(ri, &empty_rp);
416
417                 if (orig_ret_address != trampoline_address) {
418                         /*
419                          * This is the real return address. Any other
420                          * instances associated with this task are for
421                          * other calls deeper on the call stack
422                          */
423                         break;
424                 }
425         }
426         BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
427         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
428
429         reset_current_kprobe();
430         spin_unlock_irqrestore(&kretprobe_lock, flags);
431         preempt_enable_no_resched();
432
433         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
434                 hlist_del(&ri->hlist);
435                 kfree(ri);
436         }
437         /*
438          * By returning a non-zero value, we are telling
439          * kprobe_handler() that we don't want the post_handler
440          * to run (and have re-enabled preemption)
441          */
442         return 1;
443 }
444
445 /*
446  * Called after single-stepping.  p->addr is the address of the
447  * instruction whose first byte has been replaced by the "breakpoint"
448  * instruction.  To avoid the SMP problems that can occur when we
449  * temporarily put back the original opcode to single-step, we
450  * single-stepped a copy of the instruction.  The address of this
451  * copy is p->ainsn.insn.
452  */
453 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
454 {
455         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
456
457         regs->psw.addr &= PSW_ADDR_INSN;
458
459         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
460                 regs->psw.addr = (unsigned long)p->addr +
461                                 ((unsigned long)regs->psw.addr -
462                                  (unsigned long)p->ainsn.insn);
463
464         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
465                 if ((unsigned long)regs->psw.addr -
466                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
467                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
468
469         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
470                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
471                                                 (regs->gprs[p->ainsn.reg] -
472                                                 (unsigned long)p->ainsn.insn))
473                                                 | PSW_ADDR_AMODE;
474
475         regs->psw.addr |= PSW_ADDR_AMODE;
476         /* turn off PER mode */
477         regs->psw.mask &= ~PSW_MASK_PER;
478         /* Restore the original per control regs */
479         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
480         regs->psw.mask |= kcb->kprobe_saved_imask;
481 }
482
483 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
484 {
485         struct kprobe *cur = kprobe_running();
486         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
487
488         if (!cur)
489                 return 0;
490
491         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
492                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
493                 cur->post_handler(cur, regs, 0);
494         }
495
496         resume_execution(cur, regs);
497
498         /*Restore back the original saved kprobes variables and continue. */
499         if (kcb->kprobe_status == KPROBE_REENTER) {
500                 restore_previous_kprobe(kcb);
501                 goto out;
502         }
503         reset_current_kprobe();
504 out:
505         preempt_enable_no_resched();
506
507         /*
508          * if somebody else is singlestepping across a probe point, psw mask
509          * will have PER set, in which case, continue the remaining processing
510          * of do_single_step, as if this is not a probe hit.
511          */
512         if (regs->psw.mask & PSW_MASK_PER) {
513                 return 0;
514         }
515
516         return 1;
517 }
518
519 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
520 {
521         struct kprobe *cur = kprobe_running();
522         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
523         const struct exception_table_entry *entry;
524
525         switch(kcb->kprobe_status) {
526         case KPROBE_SWAP_INST:
527                 /* We are here because the instruction replacement failed */
528                 return 0;
529         case KPROBE_HIT_SS:
530         case KPROBE_REENTER:
531                 /*
532                  * We are here because the instruction being single
533                  * stepped caused a page fault. We reset the current
534                  * kprobe and the nip points back to the probe address
535                  * and allow the page fault handler to continue as a
536                  * normal page fault.
537                  */
538                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
539                 regs->psw.mask &= ~PSW_MASK_PER;
540                 regs->psw.mask |= kcb->kprobe_saved_imask;
541                 if (kcb->kprobe_status == KPROBE_REENTER)
542                         restore_previous_kprobe(kcb);
543                 else
544                         reset_current_kprobe();
545                 preempt_enable_no_resched();
546                 break;
547         case KPROBE_HIT_ACTIVE:
548         case KPROBE_HIT_SSDONE:
549                 /*
550                  * We increment the nmissed count for accounting,
551                  * we can also use npre/npostfault count for accouting
552                  * these specific fault cases.
553                  */
554                 kprobes_inc_nmissed_count(cur);
555
556                 /*
557                  * We come here because instructions in the pre/post
558                  * handler caused the page_fault, this could happen
559                  * if handler tries to access user space by
560                  * copy_from_user(), get_user() etc. Let the
561                  * user-specified handler try to fix it first.
562                  */
563                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
564                         return 1;
565
566                 /*
567                  * In case the user-specified fault handler returned
568                  * zero, try to fix up.
569                  */
570                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
571                 if (entry) {
572                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
573                         return 1;
574                 }
575
576                 /*
577                  * fixup_exception() could not handle it,
578                  * Let do_page_fault() fix it.
579                  */
580                 break;
581         default:
582                 break;
583         }
584         return 0;
585 }
586
587 /*
588  * Wrapper routine to for handling exceptions.
589  */
590 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
591                                        unsigned long val, void *data)
592 {
593         struct die_args *args = (struct die_args *)data;
594         int ret = NOTIFY_DONE;
595
596         switch (val) {
597         case DIE_BPT:
598                 if (kprobe_handler(args->regs))
599                         ret = NOTIFY_STOP;
600                 break;
601         case DIE_SSTEP:
602                 if (post_kprobe_handler(args->regs))
603                         ret = NOTIFY_STOP;
604                 break;
605         case DIE_TRAP:
606         case DIE_PAGE_FAULT:
607                 /* kprobe_running() needs smp_processor_id() */
608                 preempt_disable();
609                 if (kprobe_running() &&
610                     kprobe_fault_handler(args->regs, args->trapnr))
611                         ret = NOTIFY_STOP;
612                 preempt_enable();
613                 break;
614         default:
615                 break;
616         }
617         return ret;
618 }
619
620 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
621 {
622         struct jprobe *jp = container_of(p, struct jprobe, kp);
623         unsigned long addr;
624         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
625
626         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
627
628         /* setup return addr to the jprobe handler routine */
629         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
630
631         /* r14 is the function return address */
632         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
633         /* r15 is the stack pointer */
634         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
635         addr = (unsigned long)kcb->jprobe_saved_r15;
636
637         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
638                MIN_STACK_SIZE(addr));
639         return 1;
640 }
641
642 void __kprobes jprobe_return(void)
643 {
644         asm volatile(".word 0x0002");
645 }
646
647 void __kprobes jprobe_return_end(void)
648 {
649         asm volatile("bcr 0,0");
650 }
651
652 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
653 {
654         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
655         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
656
657         /* Put the regs back */
658         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
659         /* put the stack back */
660         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
661                MIN_STACK_SIZE(stack_addr));
662         preempt_enable_no_resched();
663         return 1;
664 }
665
666 static struct kprobe trampoline_p = {
667         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
668         .pre_handler = trampoline_probe_handler
669 };
670
671 int __init arch_init_kprobes(void)
672 {
673         return register_kprobe(&trampoline_p);
674 }