kprobes: support kretprobe blacklist
[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                 printk("Attempt to register kprobe at an unaligned address\n");
46                 return -EINVAL;
47                 }
48
49         /* Use the get_insn_slot() facility for correctness */
50         if (!(p->ainsn.insn = get_insn_slot()))
51                 return -ENOMEM;
52
53         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
54
55         get_instruction_type(&p->ainsn);
56         p->opcode = *p->addr;
57         return 0;
58 }
59
60 int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
61 {
62         switch (*(__u8 *) instruction) {
63         case 0x0c:      /* bassm */
64         case 0x0b:      /* bsm   */
65         case 0x83:      /* diag  */
66         case 0x44:      /* ex    */
67                 return -EINVAL;
68         }
69         switch (*(__u16 *) instruction) {
70         case 0x0101:    /* pr    */
71         case 0xb25a:    /* bsa   */
72         case 0xb240:    /* bakr  */
73         case 0xb258:    /* bsg   */
74         case 0xb218:    /* pc    */
75         case 0xb228:    /* pt    */
76                 return -EINVAL;
77         }
78         return 0;
79 }
80
81 void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
82 {
83         /* default fixup method */
84         ainsn->fixup = FIXUP_PSW_NORMAL;
85
86         /* save r1 operand */
87         ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
88
89         /* save the instruction length (pop 5-5) in bytes */
90         switch (*(__u8 *) (ainsn->insn) >> 6) {
91         case 0:
92                 ainsn->ilen = 2;
93                 break;
94         case 1:
95         case 2:
96                 ainsn->ilen = 4;
97                 break;
98         case 3:
99                 ainsn->ilen = 6;
100                 break;
101         }
102
103         switch (*(__u8 *) ainsn->insn) {
104         case 0x05:      /* balr */
105         case 0x0d:      /* basr */
106                 ainsn->fixup = FIXUP_RETURN_REGISTER;
107                 /* if r2 = 0, no branch will be taken */
108                 if ((*ainsn->insn & 0x0f) == 0)
109                         ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
110                 break;
111         case 0x06:      /* bctr */
112         case 0x07:      /* bcr  */
113                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
114                 break;
115         case 0x45:      /* bal  */
116         case 0x4d:      /* bas  */
117                 ainsn->fixup = FIXUP_RETURN_REGISTER;
118                 break;
119         case 0x47:      /* bc   */
120         case 0x46:      /* bct  */
121         case 0x86:      /* bxh  */
122         case 0x87:      /* bxle */
123                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
124                 break;
125         case 0x82:      /* lpsw */
126                 ainsn->fixup = FIXUP_NOT_REQUIRED;
127                 break;
128         case 0xb2:      /* lpswe */
129                 if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
130                         ainsn->fixup = FIXUP_NOT_REQUIRED;
131                 }
132                 break;
133         case 0xa7:      /* bras */
134                 if ((*ainsn->insn & 0x0f) == 0x05) {
135                         ainsn->fixup |= FIXUP_RETURN_REGISTER;
136                 }
137                 break;
138         case 0xc0:
139                 if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
140                         || (*ainsn->insn & 0x0f) == 0x05) /* brasl */
141                 ainsn->fixup |= FIXUP_RETURN_REGISTER;
142                 break;
143         case 0xeb:
144                 if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||   /* bxhg  */
145                         *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
146                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
147                 }
148                 break;
149         case 0xe3:      /* bctg */
150                 if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
151                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
152                 }
153                 break;
154         }
155 }
156
157 static int __kprobes swap_instruction(void *aref)
158 {
159         struct ins_replace_args *args = aref;
160         u32 *addr;
161         u32 instr;
162         int err = -EFAULT;
163
164         /*
165          * Text segment is read-only, hence we use stura to bypass dynamic
166          * address translation to exchange the instruction. Since stura
167          * always operates on four bytes, but we only want to exchange two
168          * bytes do some calculations to get things right. In addition we
169          * shall not cross any page boundaries (vmalloc area!) when writing
170          * the new instruction.
171          */
172         addr = (u32 *)((unsigned long)args->ptr & -4UL);
173         if ((unsigned long)args->ptr & 2)
174                 instr = ((*addr) & 0xffff0000) | args->new;
175         else
176                 instr = ((*addr) & 0x0000ffff) | args->new << 16;
177
178         asm volatile(
179                 "       lra     %1,0(%1)\n"
180                 "0:     stura   %2,%1\n"
181                 "1:     la      %0,0\n"
182                 "2:\n"
183                 EX_TABLE(0b,2b)
184                 : "+d" (err)
185                 : "a" (addr), "d" (instr)
186                 : "memory", "cc");
187
188         return err;
189 }
190
191 void __kprobes arch_arm_kprobe(struct kprobe *p)
192 {
193         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
194         unsigned long status = kcb->kprobe_status;
195         struct ins_replace_args args;
196
197         args.ptr = p->addr;
198         args.old = p->opcode;
199         args.new = BREAKPOINT_INSTRUCTION;
200
201         kcb->kprobe_status = KPROBE_SWAP_INST;
202         stop_machine_run(swap_instruction, &args, NR_CPUS);
203         kcb->kprobe_status = status;
204 }
205
206 void __kprobes arch_disarm_kprobe(struct kprobe *p)
207 {
208         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
209         unsigned long status = kcb->kprobe_status;
210         struct ins_replace_args args;
211
212         args.ptr = p->addr;
213         args.old = BREAKPOINT_INSTRUCTION;
214         args.new = p->opcode;
215
216         kcb->kprobe_status = KPROBE_SWAP_INST;
217         stop_machine_run(swap_instruction, &args, NR_CPUS);
218         kcb->kprobe_status = status;
219 }
220
221 void __kprobes arch_remove_kprobe(struct kprobe *p)
222 {
223         mutex_lock(&kprobe_mutex);
224         free_insn_slot(p->ainsn.insn, 0);
225         mutex_unlock(&kprobe_mutex);
226 }
227
228 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
229 {
230         per_cr_bits kprobe_per_regs[1];
231
232         memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
233         regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
234
235         /* Set up the per control reg info, will pass to lctl */
236         kprobe_per_regs[0].em_instruction_fetch = 1;
237         kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
238         kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
239
240         /* Set the PER control regs, turns on single step for this address */
241         __ctl_load(kprobe_per_regs, 9, 11);
242         regs->psw.mask |= PSW_MASK_PER;
243         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
244 }
245
246 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
247 {
248         kcb->prev_kprobe.kp = kprobe_running();
249         kcb->prev_kprobe.status = kcb->kprobe_status;
250         kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
251         memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
252                                         sizeof(kcb->kprobe_saved_ctl));
253 }
254
255 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
256 {
257         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
258         kcb->kprobe_status = kcb->prev_kprobe.status;
259         kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
260         memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
261                                         sizeof(kcb->kprobe_saved_ctl));
262 }
263
264 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
265                                                 struct kprobe_ctlblk *kcb)
266 {
267         __get_cpu_var(current_kprobe) = p;
268         /* Save the interrupt and per flags */
269         kcb->kprobe_saved_imask = regs->psw.mask &
270             (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
271         /* Save the control regs that govern PER */
272         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
273 }
274
275 /* Called with kretprobe_lock held */
276 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
277                                         struct pt_regs *regs)
278 {
279         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
280
281         /* Replace the return addr with trampoline addr */
282         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
283 }
284
285 static int __kprobes kprobe_handler(struct pt_regs *regs)
286 {
287         struct kprobe *p;
288         int ret = 0;
289         unsigned long *addr = (unsigned long *)
290                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
291         struct kprobe_ctlblk *kcb;
292
293         /*
294          * We don't want to be preempted for the entire
295          * duration of kprobe processing
296          */
297         preempt_disable();
298         kcb = get_kprobe_ctlblk();
299
300         /* Check we're not actually recursing */
301         if (kprobe_running()) {
302                 p = get_kprobe(addr);
303                 if (p) {
304                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
305                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
306                                 regs->psw.mask &= ~PSW_MASK_PER;
307                                 regs->psw.mask |= kcb->kprobe_saved_imask;
308                                 goto no_kprobe;
309                         }
310                         /* We have reentered the kprobe_handler(), since
311                          * another probe was hit while within the handler.
312                          * We here save the original kprobes variables and
313                          * just single step on the instruction of the new probe
314                          * without calling any user handlers.
315                          */
316                         save_previous_kprobe(kcb);
317                         set_current_kprobe(p, regs, kcb);
318                         kprobes_inc_nmissed_count(p);
319                         prepare_singlestep(p, regs);
320                         kcb->kprobe_status = KPROBE_REENTER;
321                         return 1;
322                 } else {
323                         p = __get_cpu_var(current_kprobe);
324                         if (p->break_handler && p->break_handler(p, regs)) {
325                                 goto ss_probe;
326                         }
327                 }
328                 goto no_kprobe;
329         }
330
331         p = get_kprobe(addr);
332         if (!p)
333                 /*
334                  * No kprobe at this address. The fault has not been
335                  * caused by a kprobe breakpoint. The race of breakpoint
336                  * vs. kprobe remove does not exist because on s390 we
337                  * use stop_machine_run to arm/disarm the breakpoints.
338                  */
339                 goto no_kprobe;
340
341         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
342         set_current_kprobe(p, regs, kcb);
343         if (p->pre_handler && p->pre_handler(p, regs))
344                 /* handler has already set things up, so skip ss setup */
345                 return 1;
346
347 ss_probe:
348         prepare_singlestep(p, regs);
349         kcb->kprobe_status = KPROBE_HIT_SS;
350         return 1;
351
352 no_kprobe:
353         preempt_enable_no_resched();
354         return ret;
355 }
356
357 /*
358  * Function return probe trampoline:
359  *      - init_kprobes() establishes a probepoint here
360  *      - When the probed function returns, this probe
361  *              causes the handlers to fire
362  */
363 void kretprobe_trampoline_holder(void)
364 {
365         asm volatile(".global kretprobe_trampoline\n"
366                      "kretprobe_trampoline: bcr 0,0\n");
367 }
368
369 /*
370  * Called when the probe at kretprobe trampoline is hit
371  */
372 static int __kprobes trampoline_probe_handler(struct kprobe *p,
373                                               struct pt_regs *regs)
374 {
375         struct kretprobe_instance *ri = NULL;
376         struct hlist_head *head, empty_rp;
377         struct hlist_node *node, *tmp;
378         unsigned long flags, orig_ret_address = 0;
379         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
380
381         INIT_HLIST_HEAD(&empty_rp);
382         spin_lock_irqsave(&kretprobe_lock, flags);
383         head = kretprobe_inst_table_head(current);
384
385         /*
386          * It is possible to have multiple instances associated with a given
387          * task either because an multiple functions in the call path
388          * have a return probe installed on them, and/or more then one return
389          * return probe was registered for a target function.
390          *
391          * We can handle this because:
392          *     - instances are always inserted at the head of the list
393          *     - when multiple return probes are registered for the same
394          *       function, the first instance's ret_addr will point to the
395          *       real return address, and all the rest will point to
396          *       kretprobe_trampoline
397          */
398         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
399                 if (ri->task != current)
400                         /* another task is sharing our hash bucket */
401                         continue;
402
403                 if (ri->rp && ri->rp->handler)
404                         ri->rp->handler(ri, regs);
405
406                 orig_ret_address = (unsigned long)ri->ret_addr;
407                 recycle_rp_inst(ri, &empty_rp);
408
409                 if (orig_ret_address != trampoline_address) {
410                         /*
411                          * This is the real return address. Any other
412                          * instances associated with this task are for
413                          * other calls deeper on the call stack
414                          */
415                         break;
416                 }
417         }
418         kretprobe_assert(ri, orig_ret_address, trampoline_address);
419         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
420
421         reset_current_kprobe();
422         spin_unlock_irqrestore(&kretprobe_lock, flags);
423         preempt_enable_no_resched();
424
425         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
426                 hlist_del(&ri->hlist);
427                 kfree(ri);
428         }
429         /*
430          * By returning a non-zero value, we are telling
431          * kprobe_handler() that we don't want the post_handler
432          * to run (and have re-enabled preemption)
433          */
434         return 1;
435 }
436
437 /*
438  * Called after single-stepping.  p->addr is the address of the
439  * instruction whose first byte has been replaced by the "breakpoint"
440  * instruction.  To avoid the SMP problems that can occur when we
441  * temporarily put back the original opcode to single-step, we
442  * single-stepped a copy of the instruction.  The address of this
443  * copy is p->ainsn.insn.
444  */
445 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
446 {
447         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
448
449         regs->psw.addr &= PSW_ADDR_INSN;
450
451         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
452                 regs->psw.addr = (unsigned long)p->addr +
453                                 ((unsigned long)regs->psw.addr -
454                                  (unsigned long)p->ainsn.insn);
455
456         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
457                 if ((unsigned long)regs->psw.addr -
458                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
459                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
460
461         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
462                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
463                                                 (regs->gprs[p->ainsn.reg] -
464                                                 (unsigned long)p->ainsn.insn))
465                                                 | PSW_ADDR_AMODE;
466
467         regs->psw.addr |= PSW_ADDR_AMODE;
468         /* turn off PER mode */
469         regs->psw.mask &= ~PSW_MASK_PER;
470         /* Restore the original per control regs */
471         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
472         regs->psw.mask |= kcb->kprobe_saved_imask;
473 }
474
475 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
476 {
477         struct kprobe *cur = kprobe_running();
478         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
479
480         if (!cur)
481                 return 0;
482
483         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
484                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
485                 cur->post_handler(cur, regs, 0);
486         }
487
488         resume_execution(cur, regs);
489
490         /*Restore back the original saved kprobes variables and continue. */
491         if (kcb->kprobe_status == KPROBE_REENTER) {
492                 restore_previous_kprobe(kcb);
493                 goto out;
494         }
495         reset_current_kprobe();
496 out:
497         preempt_enable_no_resched();
498
499         /*
500          * if somebody else is singlestepping across a probe point, psw mask
501          * will have PER set, in which case, continue the remaining processing
502          * of do_single_step, as if this is not a probe hit.
503          */
504         if (regs->psw.mask & PSW_MASK_PER) {
505                 return 0;
506         }
507
508         return 1;
509 }
510
511 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
512 {
513         struct kprobe *cur = kprobe_running();
514         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
515         const struct exception_table_entry *entry;
516
517         switch(kcb->kprobe_status) {
518         case KPROBE_SWAP_INST:
519                 /* We are here because the instruction replacement failed */
520                 return 0;
521         case KPROBE_HIT_SS:
522         case KPROBE_REENTER:
523                 /*
524                  * We are here because the instruction being single
525                  * stepped caused a page fault. We reset the current
526                  * kprobe and the nip points back to the probe address
527                  * and allow the page fault handler to continue as a
528                  * normal page fault.
529                  */
530                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
531                 regs->psw.mask &= ~PSW_MASK_PER;
532                 regs->psw.mask |= kcb->kprobe_saved_imask;
533                 if (kcb->kprobe_status == KPROBE_REENTER)
534                         restore_previous_kprobe(kcb);
535                 else
536                         reset_current_kprobe();
537                 preempt_enable_no_resched();
538                 break;
539         case KPROBE_HIT_ACTIVE:
540         case KPROBE_HIT_SSDONE:
541                 /*
542                  * We increment the nmissed count for accounting,
543                  * we can also use npre/npostfault count for accouting
544                  * these specific fault cases.
545                  */
546                 kprobes_inc_nmissed_count(cur);
547
548                 /*
549                  * We come here because instructions in the pre/post
550                  * handler caused the page_fault, this could happen
551                  * if handler tries to access user space by
552                  * copy_from_user(), get_user() etc. Let the
553                  * user-specified handler try to fix it first.
554                  */
555                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
556                         return 1;
557
558                 /*
559                  * In case the user-specified fault handler returned
560                  * zero, try to fix up.
561                  */
562                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
563                 if (entry) {
564                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
565                         return 1;
566                 }
567
568                 /*
569                  * fixup_exception() could not handle it,
570                  * Let do_page_fault() fix it.
571                  */
572                 break;
573         default:
574                 break;
575         }
576         return 0;
577 }
578
579 /*
580  * Wrapper routine to for handling exceptions.
581  */
582 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
583                                        unsigned long val, void *data)
584 {
585         struct die_args *args = (struct die_args *)data;
586         int ret = NOTIFY_DONE;
587
588         switch (val) {
589         case DIE_BPT:
590                 if (kprobe_handler(args->regs))
591                         ret = NOTIFY_STOP;
592                 break;
593         case DIE_SSTEP:
594                 if (post_kprobe_handler(args->regs))
595                         ret = NOTIFY_STOP;
596                 break;
597         case DIE_TRAP:
598                 /* kprobe_running() needs smp_processor_id() */
599                 preempt_disable();
600                 if (kprobe_running() &&
601                     kprobe_fault_handler(args->regs, args->trapnr))
602                         ret = NOTIFY_STOP;
603                 preempt_enable();
604                 break;
605         default:
606                 break;
607         }
608         return ret;
609 }
610
611 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
612 {
613         struct jprobe *jp = container_of(p, struct jprobe, kp);
614         unsigned long addr;
615         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
616
617         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
618
619         /* setup return addr to the jprobe handler routine */
620         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
621
622         /* r14 is the function return address */
623         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
624         /* r15 is the stack pointer */
625         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
626         addr = (unsigned long)kcb->jprobe_saved_r15;
627
628         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
629                MIN_STACK_SIZE(addr));
630         return 1;
631 }
632
633 void __kprobes jprobe_return(void)
634 {
635         asm volatile(".word 0x0002");
636 }
637
638 void __kprobes jprobe_return_end(void)
639 {
640         asm volatile("bcr 0,0");
641 }
642
643 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
644 {
645         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
646         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
647
648         /* Put the regs back */
649         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
650         /* put the stack back */
651         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
652                MIN_STACK_SIZE(stack_addr));
653         preempt_enable_no_resched();
654         return 1;
655 }
656
657 static struct kprobe trampoline_p = {
658         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
659         .pre_handler = trampoline_probe_handler
660 };
661
662 int __init arch_init_kprobes(void)
663 {
664         return register_kprobe(&trampoline_p);
665 }
666
667 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
668 {
669         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
670                 return 1;
671         return 0;
672 }