GNU Linux-libre 4.9.288-gnu1
[releases.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 IBM Corp. 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 <linux/uaccess.h>
29 #include <linux/extable.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/hardirq.h>
33 #include <linux/ftrace.h>
34 #include <asm/cacheflush.h>
35 #include <asm/sections.h>
36 #include <asm/uaccess.h>
37 #include <asm/dis.h>
38
39 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
40 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
41
42 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
43
44 DEFINE_INSN_CACHE_OPS(dmainsn);
45
46 static void *alloc_dmainsn_page(void)
47 {
48         return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
49 }
50
51 static void free_dmainsn_page(void *page)
52 {
53         free_page((unsigned long)page);
54 }
55
56 struct kprobe_insn_cache kprobe_dmainsn_slots = {
57         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
58         .alloc = alloc_dmainsn_page,
59         .free = free_dmainsn_page,
60         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
61         .insn_size = MAX_INSN_SIZE,
62 };
63
64 static void copy_instruction(struct kprobe *p)
65 {
66         unsigned long ip = (unsigned long) p->addr;
67         s64 disp, new_disp;
68         u64 addr, new_addr;
69
70         if (ftrace_location(ip) == ip) {
71                 /*
72                  * If kprobes patches the instruction that is morphed by
73                  * ftrace make sure that kprobes always sees the branch
74                  * "jg .+24" that skips the mcount block or the "brcl 0,0"
75                  * in case of hotpatch.
76                  */
77                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
78                 p->ainsn.is_ftrace_insn = 1;
79         } else
80                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
81         p->opcode = p->ainsn.insn[0];
82         if (!probe_is_insn_relative_long(p->ainsn.insn))
83                 return;
84         /*
85          * For pc-relative instructions in RIL-b or RIL-c format patch the
86          * RI2 displacement field. We have already made sure that the insn
87          * slot for the patched instruction is within the same 2GB area
88          * as the original instruction (either kernel image or module area).
89          * Therefore the new displacement will always fit.
90          */
91         disp = *(s32 *)&p->ainsn.insn[1];
92         addr = (u64)(unsigned long)p->addr;
93         new_addr = (u64)(unsigned long)p->ainsn.insn;
94         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
95         *(s32 *)&p->ainsn.insn[1] = new_disp;
96 }
97 NOKPROBE_SYMBOL(copy_instruction);
98
99 static inline int is_kernel_addr(void *addr)
100 {
101         return addr < (void *)_end;
102 }
103
104 static int s390_get_insn_slot(struct kprobe *p)
105 {
106         /*
107          * Get an insn slot that is within the same 2GB area like the original
108          * instruction. That way instructions with a 32bit signed displacement
109          * field can be patched and executed within the insn slot.
110          */
111         p->ainsn.insn = NULL;
112         if (is_kernel_addr(p->addr))
113                 p->ainsn.insn = get_dmainsn_slot();
114         else if (is_module_addr(p->addr))
115                 p->ainsn.insn = get_insn_slot();
116         return p->ainsn.insn ? 0 : -ENOMEM;
117 }
118 NOKPROBE_SYMBOL(s390_get_insn_slot);
119
120 static void s390_free_insn_slot(struct kprobe *p)
121 {
122         if (!p->ainsn.insn)
123                 return;
124         if (is_kernel_addr(p->addr))
125                 free_dmainsn_slot(p->ainsn.insn, 0);
126         else
127                 free_insn_slot(p->ainsn.insn, 0);
128         p->ainsn.insn = NULL;
129 }
130 NOKPROBE_SYMBOL(s390_free_insn_slot);
131
132 int arch_prepare_kprobe(struct kprobe *p)
133 {
134         if ((unsigned long) p->addr & 0x01)
135                 return -EINVAL;
136         /* Make sure the probe isn't going on a difficult instruction */
137         if (probe_is_prohibited_opcode(p->addr))
138                 return -EINVAL;
139         if (s390_get_insn_slot(p))
140                 return -ENOMEM;
141         copy_instruction(p);
142         return 0;
143 }
144 NOKPROBE_SYMBOL(arch_prepare_kprobe);
145
146 int arch_check_ftrace_location(struct kprobe *p)
147 {
148         return 0;
149 }
150
151 struct swap_insn_args {
152         struct kprobe *p;
153         unsigned int arm_kprobe : 1;
154 };
155
156 static int swap_instruction(void *data)
157 {
158         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
159         unsigned long status = kcb->kprobe_status;
160         struct swap_insn_args *args = data;
161         struct ftrace_insn new_insn, *insn;
162         struct kprobe *p = args->p;
163         size_t len;
164
165         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
166         len = sizeof(new_insn.opc);
167         if (!p->ainsn.is_ftrace_insn)
168                 goto skip_ftrace;
169         len = sizeof(new_insn);
170         insn = (struct ftrace_insn *) p->addr;
171         if (args->arm_kprobe) {
172                 if (is_ftrace_nop(insn))
173                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
174                 else
175                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
176         } else {
177                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
178                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
179                         ftrace_generate_nop_insn(&new_insn);
180         }
181 skip_ftrace:
182         kcb->kprobe_status = KPROBE_SWAP_INST;
183         s390_kernel_write(p->addr, &new_insn, len);
184         kcb->kprobe_status = status;
185         return 0;
186 }
187 NOKPROBE_SYMBOL(swap_instruction);
188
189 void arch_arm_kprobe(struct kprobe *p)
190 {
191         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
192
193         stop_machine(swap_instruction, &args, NULL);
194 }
195 NOKPROBE_SYMBOL(arch_arm_kprobe);
196
197 void arch_disarm_kprobe(struct kprobe *p)
198 {
199         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
200
201         stop_machine(swap_instruction, &args, NULL);
202 }
203 NOKPROBE_SYMBOL(arch_disarm_kprobe);
204
205 void arch_remove_kprobe(struct kprobe *p)
206 {
207         s390_free_insn_slot(p);
208 }
209 NOKPROBE_SYMBOL(arch_remove_kprobe);
210
211 static void enable_singlestep(struct kprobe_ctlblk *kcb,
212                               struct pt_regs *regs,
213                               unsigned long ip)
214 {
215         struct per_regs per_kprobe;
216
217         /* Set up the PER control registers %cr9-%cr11 */
218         per_kprobe.control = PER_EVENT_IFETCH;
219         per_kprobe.start = ip;
220         per_kprobe.end = ip;
221
222         /* Save control regs and psw mask */
223         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
224         kcb->kprobe_saved_imask = regs->psw.mask &
225                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
226
227         /* Set PER control regs, turns on single step for the given address */
228         __ctl_load(per_kprobe, 9, 11);
229         regs->psw.mask |= PSW_MASK_PER;
230         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
231         regs->psw.addr = ip;
232 }
233 NOKPROBE_SYMBOL(enable_singlestep);
234
235 static void disable_singlestep(struct kprobe_ctlblk *kcb,
236                                struct pt_regs *regs,
237                                unsigned long ip)
238 {
239         /* Restore control regs and psw mask, set new psw address */
240         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
241         regs->psw.mask &= ~PSW_MASK_PER;
242         regs->psw.mask |= kcb->kprobe_saved_imask;
243         regs->psw.addr = ip;
244 }
245 NOKPROBE_SYMBOL(disable_singlestep);
246
247 /*
248  * Activate a kprobe by storing its pointer to current_kprobe. The
249  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
250  * two kprobes can be active, see KPROBE_REENTER.
251  */
252 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
253 {
254         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
255         kcb->prev_kprobe.status = kcb->kprobe_status;
256         __this_cpu_write(current_kprobe, p);
257 }
258 NOKPROBE_SYMBOL(push_kprobe);
259
260 /*
261  * Deactivate a kprobe by backing up to the previous state. If the
262  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
263  * for any other state prev_kprobe.kp will be NULL.
264  */
265 static void pop_kprobe(struct kprobe_ctlblk *kcb)
266 {
267         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
268         kcb->kprobe_status = kcb->prev_kprobe.status;
269 }
270 NOKPROBE_SYMBOL(pop_kprobe);
271
272 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
273 {
274         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
275
276         /* Replace the return addr with trampoline addr */
277         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
278 }
279 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
280
281 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
282 {
283         switch (kcb->kprobe_status) {
284         case KPROBE_HIT_SSDONE:
285         case KPROBE_HIT_ACTIVE:
286                 kprobes_inc_nmissed_count(p);
287                 break;
288         case KPROBE_HIT_SS:
289         case KPROBE_REENTER:
290         default:
291                 /*
292                  * A kprobe on the code path to single step an instruction
293                  * is a BUG. The code path resides in the .kprobes.text
294                  * section and is executed with interrupts disabled.
295                  */
296                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
297                 dump_kprobe(p);
298                 BUG();
299         }
300 }
301 NOKPROBE_SYMBOL(kprobe_reenter_check);
302
303 static int kprobe_handler(struct pt_regs *regs)
304 {
305         struct kprobe_ctlblk *kcb;
306         struct kprobe *p;
307
308         /*
309          * We want to disable preemption for the entire duration of kprobe
310          * processing. That includes the calls to the pre/post handlers
311          * and single stepping the kprobe instruction.
312          */
313         preempt_disable();
314         kcb = get_kprobe_ctlblk();
315         p = get_kprobe((void *)(regs->psw.addr - 2));
316
317         if (p) {
318                 if (kprobe_running()) {
319                         /*
320                          * We have hit a kprobe while another is still
321                          * active. This can happen in the pre and post
322                          * handler. Single step the instruction of the
323                          * new probe but do not call any handler function
324                          * of this secondary kprobe.
325                          * push_kprobe and pop_kprobe saves and restores
326                          * the currently active kprobe.
327                          */
328                         kprobe_reenter_check(kcb, p);
329                         push_kprobe(kcb, p);
330                         kcb->kprobe_status = KPROBE_REENTER;
331                 } else {
332                         /*
333                          * If we have no pre-handler or it returned 0, we
334                          * continue with single stepping. If we have a
335                          * pre-handler and it returned non-zero, it prepped
336                          * for calling the break_handler below on re-entry
337                          * for jprobe processing, so get out doing nothing
338                          * more here.
339                          */
340                         push_kprobe(kcb, p);
341                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
342                         if (p->pre_handler && p->pre_handler(p, regs))
343                                 return 1;
344                         kcb->kprobe_status = KPROBE_HIT_SS;
345                 }
346                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
347                 return 1;
348         } else if (kprobe_running()) {
349                 p = __this_cpu_read(current_kprobe);
350                 if (p->break_handler && p->break_handler(p, regs)) {
351                         /*
352                          * Continuation after the jprobe completed and
353                          * caused the jprobe_return trap. The jprobe
354                          * break_handler "returns" to the original
355                          * function that still has the kprobe breakpoint
356                          * installed. We continue with single stepping.
357                          */
358                         kcb->kprobe_status = KPROBE_HIT_SS;
359                         enable_singlestep(kcb, regs,
360                                           (unsigned long) p->ainsn.insn);
361                         return 1;
362                 } /* else:
363                    * No kprobe at this address and the current kprobe
364                    * has no break handler (no jprobe!). The kernel just
365                    * exploded, let the standard trap handler pick up the
366                    * pieces.
367                    */
368         } /* else:
369            * No kprobe at this address and no active kprobe. The trap has
370            * not been caused by a kprobe breakpoint. The race of breakpoint
371            * vs. kprobe remove does not exist because on s390 as we use
372            * stop_machine to arm/disarm the breakpoints.
373            */
374         preempt_enable_no_resched();
375         return 0;
376 }
377 NOKPROBE_SYMBOL(kprobe_handler);
378
379 /*
380  * Function return probe trampoline:
381  *      - init_kprobes() establishes a probepoint here
382  *      - When the probed function returns, this probe
383  *              causes the handlers to fire
384  */
385 static void __used kretprobe_trampoline_holder(void)
386 {
387         asm volatile(".global kretprobe_trampoline\n"
388                      "kretprobe_trampoline: bcr 0,0\n");
389 }
390
391 /*
392  * Called when the probe at kretprobe trampoline is hit
393  */
394 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
395 {
396         struct kretprobe_instance *ri;
397         struct hlist_head *head, empty_rp;
398         struct hlist_node *tmp;
399         unsigned long flags, orig_ret_address;
400         unsigned long trampoline_address;
401         kprobe_opcode_t *correct_ret_addr;
402
403         INIT_HLIST_HEAD(&empty_rp);
404         kretprobe_hash_lock(current, &head, &flags);
405
406         /*
407          * It is possible to have multiple instances associated with a given
408          * task either because an multiple functions in the call path
409          * have a return probe installed on them, and/or more than one return
410          * return probe was registered for a target function.
411          *
412          * We can handle this because:
413          *     - instances are always inserted at the head of the list
414          *     - when multiple return probes are registered for the same
415          *       function, the first instance's ret_addr will point to the
416          *       real return address, and all the rest will point to
417          *       kretprobe_trampoline
418          */
419         ri = NULL;
420         orig_ret_address = 0;
421         correct_ret_addr = NULL;
422         trampoline_address = (unsigned long) &kretprobe_trampoline;
423         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
424                 if (ri->task != current)
425                         /* another task is sharing our hash bucket */
426                         continue;
427
428                 orig_ret_address = (unsigned long) ri->ret_addr;
429
430                 if (orig_ret_address != trampoline_address)
431                         /*
432                          * This is the real return address. Any other
433                          * instances associated with this task are for
434                          * other calls deeper on the call stack
435                          */
436                         break;
437         }
438
439         kretprobe_assert(ri, orig_ret_address, trampoline_address);
440
441         correct_ret_addr = ri->ret_addr;
442         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
443                 if (ri->task != current)
444                         /* another task is sharing our hash bucket */
445                         continue;
446
447                 orig_ret_address = (unsigned long) ri->ret_addr;
448
449                 if (ri->rp && ri->rp->handler) {
450                         ri->ret_addr = correct_ret_addr;
451                         ri->rp->handler(ri, regs);
452                 }
453
454                 recycle_rp_inst(ri, &empty_rp);
455
456                 if (orig_ret_address != trampoline_address)
457                         /*
458                          * This is the real return address. Any other
459                          * instances associated with this task are for
460                          * other calls deeper on the call stack
461                          */
462                         break;
463         }
464
465         regs->psw.addr = orig_ret_address;
466
467         pop_kprobe(get_kprobe_ctlblk());
468         kretprobe_hash_unlock(current, &flags);
469         preempt_enable_no_resched();
470
471         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
472                 hlist_del(&ri->hlist);
473                 kfree(ri);
474         }
475         /*
476          * By returning a non-zero value, we are telling
477          * kprobe_handler() that we don't want the post_handler
478          * to run (and have re-enabled preemption)
479          */
480         return 1;
481 }
482 NOKPROBE_SYMBOL(trampoline_probe_handler);
483
484 /*
485  * Called after single-stepping.  p->addr is the address of the
486  * instruction whose first byte has been replaced by the "breakpoint"
487  * instruction.  To avoid the SMP problems that can occur when we
488  * temporarily put back the original opcode to single-step, we
489  * single-stepped a copy of the instruction.  The address of this
490  * copy is p->ainsn.insn.
491  */
492 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
493 {
494         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
495         unsigned long ip = regs->psw.addr;
496         int fixup = probe_get_fixup_type(p->ainsn.insn);
497
498         /* Check if the kprobes location is an enabled ftrace caller */
499         if (p->ainsn.is_ftrace_insn) {
500                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
501                 struct ftrace_insn call_insn;
502
503                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
504                 /*
505                  * A kprobe on an enabled ftrace call site actually single
506                  * stepped an unconditional branch (ftrace nop equivalent).
507                  * Now we need to fixup things and pretend that a brasl r0,...
508                  * was executed instead.
509                  */
510                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
511                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
512                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
513                 }
514         }
515
516         if (fixup & FIXUP_PSW_NORMAL)
517                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
518
519         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
520                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
521                 if (ip - (unsigned long) p->ainsn.insn == ilen)
522                         ip = (unsigned long) p->addr + ilen;
523         }
524
525         if (fixup & FIXUP_RETURN_REGISTER) {
526                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
527                 regs->gprs[reg] += (unsigned long) p->addr -
528                                    (unsigned long) p->ainsn.insn;
529         }
530
531         disable_singlestep(kcb, regs, ip);
532 }
533 NOKPROBE_SYMBOL(resume_execution);
534
535 static int post_kprobe_handler(struct pt_regs *regs)
536 {
537         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
538         struct kprobe *p = kprobe_running();
539
540         if (!p)
541                 return 0;
542
543         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
544                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
545                 p->post_handler(p, regs, 0);
546         }
547
548         resume_execution(p, regs);
549         pop_kprobe(kcb);
550         preempt_enable_no_resched();
551
552         /*
553          * if somebody else is singlestepping across a probe point, psw mask
554          * will have PER set, in which case, continue the remaining processing
555          * of do_single_step, as if this is not a probe hit.
556          */
557         if (regs->psw.mask & PSW_MASK_PER)
558                 return 0;
559
560         return 1;
561 }
562 NOKPROBE_SYMBOL(post_kprobe_handler);
563
564 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
565 {
566         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
567         struct kprobe *p = kprobe_running();
568         const struct exception_table_entry *entry;
569
570         switch(kcb->kprobe_status) {
571         case KPROBE_SWAP_INST:
572                 /* We are here because the instruction replacement failed */
573                 return 0;
574         case KPROBE_HIT_SS:
575         case KPROBE_REENTER:
576                 /*
577                  * We are here because the instruction being single
578                  * stepped caused a page fault. We reset the current
579                  * kprobe and the nip points back to the probe address
580                  * and allow the page fault handler to continue as a
581                  * normal page fault.
582                  */
583                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
584                 pop_kprobe(kcb);
585                 preempt_enable_no_resched();
586                 break;
587         case KPROBE_HIT_ACTIVE:
588         case KPROBE_HIT_SSDONE:
589                 /*
590                  * We increment the nmissed count for accounting,
591                  * we can also use npre/npostfault count for accounting
592                  * these specific fault cases.
593                  */
594                 kprobes_inc_nmissed_count(p);
595
596                 /*
597                  * We come here because instructions in the pre/post
598                  * handler caused the page_fault, this could happen
599                  * if handler tries to access user space by
600                  * copy_from_user(), get_user() etc. Let the
601                  * user-specified handler try to fix it first.
602                  */
603                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
604                         return 1;
605
606                 /*
607                  * In case the user-specified fault handler returned
608                  * zero, try to fix up.
609                  */
610                 entry = search_exception_tables(regs->psw.addr);
611                 if (entry) {
612                         regs->psw.addr = extable_fixup(entry);
613                         return 1;
614                 }
615
616                 /*
617                  * fixup_exception() could not handle it,
618                  * Let do_page_fault() fix it.
619                  */
620                 break;
621         default:
622                 break;
623         }
624         return 0;
625 }
626 NOKPROBE_SYMBOL(kprobe_trap_handler);
627
628 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
629 {
630         int ret;
631
632         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
633                 local_irq_disable();
634         ret = kprobe_trap_handler(regs, trapnr);
635         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
636                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
637         return ret;
638 }
639 NOKPROBE_SYMBOL(kprobe_fault_handler);
640
641 /*
642  * Wrapper routine to for handling exceptions.
643  */
644 int kprobe_exceptions_notify(struct notifier_block *self,
645                              unsigned long val, void *data)
646 {
647         struct die_args *args = (struct die_args *) data;
648         struct pt_regs *regs = args->regs;
649         int ret = NOTIFY_DONE;
650
651         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
652                 local_irq_disable();
653
654         switch (val) {
655         case DIE_BPT:
656                 if (kprobe_handler(regs))
657                         ret = NOTIFY_STOP;
658                 break;
659         case DIE_SSTEP:
660                 if (post_kprobe_handler(regs))
661                         ret = NOTIFY_STOP;
662                 break;
663         case DIE_TRAP:
664                 if (!preemptible() && kprobe_running() &&
665                     kprobe_trap_handler(regs, args->trapnr))
666                         ret = NOTIFY_STOP;
667                 break;
668         default:
669                 break;
670         }
671
672         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
673                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
674
675         return ret;
676 }
677 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
678
679 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
680 {
681         struct jprobe *jp = container_of(p, struct jprobe, kp);
682         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
683         unsigned long stack;
684
685         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
686
687         /* setup return addr to the jprobe handler routine */
688         regs->psw.addr = (unsigned long) jp->entry;
689         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
690
691         /* r15 is the stack pointer */
692         stack = (unsigned long) regs->gprs[15];
693
694         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
695
696         /*
697          * jprobes use jprobe_return() which skips the normal return
698          * path of the function, and this messes up the accounting of the
699          * function graph tracer to get messed up.
700          *
701          * Pause function graph tracing while performing the jprobe function.
702          */
703         pause_graph_tracing();
704         return 1;
705 }
706 NOKPROBE_SYMBOL(setjmp_pre_handler);
707
708 void jprobe_return(void)
709 {
710         asm volatile(".word 0x0002");
711 }
712 NOKPROBE_SYMBOL(jprobe_return);
713
714 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
715 {
716         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
717         unsigned long stack;
718
719         /* It's OK to start function graph tracing again */
720         unpause_graph_tracing();
721
722         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
723
724         /* Put the regs back */
725         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
726         /* put the stack back */
727         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
728         preempt_enable_no_resched();
729         return 1;
730 }
731 NOKPROBE_SYMBOL(longjmp_break_handler);
732
733 static struct kprobe trampoline = {
734         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
735         .pre_handler = trampoline_probe_handler
736 };
737
738 int __init arch_init_kprobes(void)
739 {
740         return register_kprobe(&trampoline);
741 }
742
743 int arch_trampoline_kprobe(struct kprobe *p)
744 {
745         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
746 }
747 NOKPROBE_SYMBOL(arch_trampoline_kprobe);