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Linux/arch/s390/kernel/kprobes.c

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  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/set_memory.h>
 35 #include <asm/sections.h>
 36 #include <linux/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         void *page;
 49 
 50         page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA);
 51         if (page)
 52                 set_memory_x((unsigned long) page, 1);
 53         return page;
 54 }
 55 
 56 static void free_dmainsn_page(void *page)
 57 {
 58         set_memory_nx((unsigned long) page, 1);
 59         free_page((unsigned long)page);
 60 }
 61 
 62 struct kprobe_insn_cache kprobe_dmainsn_slots = {
 63         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
 64         .alloc = alloc_dmainsn_page,
 65         .free = free_dmainsn_page,
 66         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
 67         .insn_size = MAX_INSN_SIZE,
 68 };
 69 
 70 static void copy_instruction(struct kprobe *p)
 71 {
 72         unsigned long ip = (unsigned long) p->addr;
 73         s64 disp, new_disp;
 74         u64 addr, new_addr;
 75 
 76         if (ftrace_location(ip) == ip) {
 77                 /*
 78                  * If kprobes patches the instruction that is morphed by
 79                  * ftrace make sure that kprobes always sees the branch
 80                  * "jg .+24" that skips the mcount block or the "brcl 0,0"
 81                  * in case of hotpatch.
 82                  */
 83                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
 84                 p->ainsn.is_ftrace_insn = 1;
 85         } else
 86                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
 87         p->opcode = p->ainsn.insn[0];
 88         if (!probe_is_insn_relative_long(p->ainsn.insn))
 89                 return;
 90         /*
 91          * For pc-relative instructions in RIL-b or RIL-c format patch the
 92          * RI2 displacement field. We have already made sure that the insn
 93          * slot for the patched instruction is within the same 2GB area
 94          * as the original instruction (either kernel image or module area).
 95          * Therefore the new displacement will always fit.
 96          */
 97         disp = *(s32 *)&p->ainsn.insn[1];
 98         addr = (u64)(unsigned long)p->addr;
 99         new_addr = (u64)(unsigned long)p->ainsn.insn;
100         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
101         *(s32 *)&p->ainsn.insn[1] = new_disp;
102 }
103 NOKPROBE_SYMBOL(copy_instruction);
104 
105 static inline int is_kernel_addr(void *addr)
106 {
107         return addr < (void *)_end;
108 }
109 
110 static int s390_get_insn_slot(struct kprobe *p)
111 {
112         /*
113          * Get an insn slot that is within the same 2GB area like the original
114          * instruction. That way instructions with a 32bit signed displacement
115          * field can be patched and executed within the insn slot.
116          */
117         p->ainsn.insn = NULL;
118         if (is_kernel_addr(p->addr))
119                 p->ainsn.insn = get_dmainsn_slot();
120         else if (is_module_addr(p->addr))
121                 p->ainsn.insn = get_insn_slot();
122         return p->ainsn.insn ? 0 : -ENOMEM;
123 }
124 NOKPROBE_SYMBOL(s390_get_insn_slot);
125 
126 static void s390_free_insn_slot(struct kprobe *p)
127 {
128         if (!p->ainsn.insn)
129                 return;
130         if (is_kernel_addr(p->addr))
131                 free_dmainsn_slot(p->ainsn.insn, 0);
132         else
133                 free_insn_slot(p->ainsn.insn, 0);
134         p->ainsn.insn = NULL;
135 }
136 NOKPROBE_SYMBOL(s390_free_insn_slot);
137 
138 int arch_prepare_kprobe(struct kprobe *p)
139 {
140         if ((unsigned long) p->addr & 0x01)
141                 return -EINVAL;
142         /* Make sure the probe isn't going on a difficult instruction */
143         if (probe_is_prohibited_opcode(p->addr))
144                 return -EINVAL;
145         if (s390_get_insn_slot(p))
146                 return -ENOMEM;
147         copy_instruction(p);
148         return 0;
149 }
150 NOKPROBE_SYMBOL(arch_prepare_kprobe);
151 
152 int arch_check_ftrace_location(struct kprobe *p)
153 {
154         return 0;
155 }
156 
157 struct swap_insn_args {
158         struct kprobe *p;
159         unsigned int arm_kprobe : 1;
160 };
161 
162 static int swap_instruction(void *data)
163 {
164         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
165         unsigned long status = kcb->kprobe_status;
166         struct swap_insn_args *args = data;
167         struct ftrace_insn new_insn, *insn;
168         struct kprobe *p = args->p;
169         size_t len;
170 
171         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
172         len = sizeof(new_insn.opc);
173         if (!p->ainsn.is_ftrace_insn)
174                 goto skip_ftrace;
175         len = sizeof(new_insn);
176         insn = (struct ftrace_insn *) p->addr;
177         if (args->arm_kprobe) {
178                 if (is_ftrace_nop(insn))
179                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
180                 else
181                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
182         } else {
183                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
184                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
185                         ftrace_generate_nop_insn(&new_insn);
186         }
187 skip_ftrace:
188         kcb->kprobe_status = KPROBE_SWAP_INST;
189         s390_kernel_write(p->addr, &new_insn, len);
190         kcb->kprobe_status = status;
191         return 0;
192 }
193 NOKPROBE_SYMBOL(swap_instruction);
194 
195 void arch_arm_kprobe(struct kprobe *p)
196 {
197         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
198 
199         stop_machine_cpuslocked(swap_instruction, &args, NULL);
200 }
201 NOKPROBE_SYMBOL(arch_arm_kprobe);
202 
203 void arch_disarm_kprobe(struct kprobe *p)
204 {
205         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
206 
207         stop_machine_cpuslocked(swap_instruction, &args, NULL);
208 }
209 NOKPROBE_SYMBOL(arch_disarm_kprobe);
210 
211 void arch_remove_kprobe(struct kprobe *p)
212 {
213         s390_free_insn_slot(p);
214 }
215 NOKPROBE_SYMBOL(arch_remove_kprobe);
216 
217 static void enable_singlestep(struct kprobe_ctlblk *kcb,
218                               struct pt_regs *regs,
219                               unsigned long ip)
220 {
221         struct per_regs per_kprobe;
222 
223         /* Set up the PER control registers %cr9-%cr11 */
224         per_kprobe.control = PER_EVENT_IFETCH;
225         per_kprobe.start = ip;
226         per_kprobe.end = ip;
227 
228         /* Save control regs and psw mask */
229         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
230         kcb->kprobe_saved_imask = regs->psw.mask &
231                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
232 
233         /* Set PER control regs, turns on single step for the given address */
234         __ctl_load(per_kprobe, 9, 11);
235         regs->psw.mask |= PSW_MASK_PER;
236         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
237         regs->psw.addr = ip;
238 }
239 NOKPROBE_SYMBOL(enable_singlestep);
240 
241 static void disable_singlestep(struct kprobe_ctlblk *kcb,
242                                struct pt_regs *regs,
243                                unsigned long ip)
244 {
245         /* Restore control regs and psw mask, set new psw address */
246         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
247         regs->psw.mask &= ~PSW_MASK_PER;
248         regs->psw.mask |= kcb->kprobe_saved_imask;
249         regs->psw.addr = ip;
250 }
251 NOKPROBE_SYMBOL(disable_singlestep);
252 
253 /*
254  * Activate a kprobe by storing its pointer to current_kprobe. The
255  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
256  * two kprobes can be active, see KPROBE_REENTER.
257  */
258 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
259 {
260         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
261         kcb->prev_kprobe.status = kcb->kprobe_status;
262         __this_cpu_write(current_kprobe, p);
263 }
264 NOKPROBE_SYMBOL(push_kprobe);
265 
266 /*
267  * Deactivate a kprobe by backing up to the previous state. If the
268  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
269  * for any other state prev_kprobe.kp will be NULL.
270  */
271 static void pop_kprobe(struct kprobe_ctlblk *kcb)
272 {
273         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
274         kcb->kprobe_status = kcb->prev_kprobe.status;
275 }
276 NOKPROBE_SYMBOL(pop_kprobe);
277 
278 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
279 {
280         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
281 
282         /* Replace the return addr with trampoline addr */
283         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
284 }
285 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
286 
287 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
288 {
289         switch (kcb->kprobe_status) {
290         case KPROBE_HIT_SSDONE:
291         case KPROBE_HIT_ACTIVE:
292                 kprobes_inc_nmissed_count(p);
293                 break;
294         case KPROBE_HIT_SS:
295         case KPROBE_REENTER:
296         default:
297                 /*
298                  * A kprobe on the code path to single step an instruction
299                  * is a BUG. The code path resides in the .kprobes.text
300                  * section and is executed with interrupts disabled.
301                  */
302                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
303                 dump_kprobe(p);
304                 BUG();
305         }
306 }
307 NOKPROBE_SYMBOL(kprobe_reenter_check);
308 
309 static int kprobe_handler(struct pt_regs *regs)
310 {
311         struct kprobe_ctlblk *kcb;
312         struct kprobe *p;
313 
314         /*
315          * We want to disable preemption for the entire duration of kprobe
316          * processing. That includes the calls to the pre/post handlers
317          * and single stepping the kprobe instruction.
318          */
319         preempt_disable();
320         kcb = get_kprobe_ctlblk();
321         p = get_kprobe((void *)(regs->psw.addr - 2));
322 
323         if (p) {
324                 if (kprobe_running()) {
325                         /*
326                          * We have hit a kprobe while another is still
327                          * active. This can happen in the pre and post
328                          * handler. Single step the instruction of the
329                          * new probe but do not call any handler function
330                          * of this secondary kprobe.
331                          * push_kprobe and pop_kprobe saves and restores
332                          * the currently active kprobe.
333                          */
334                         kprobe_reenter_check(kcb, p);
335                         push_kprobe(kcb, p);
336                         kcb->kprobe_status = KPROBE_REENTER;
337                 } else {
338                         /*
339                          * If we have no pre-handler or it returned 0, we
340                          * continue with single stepping. If we have a
341                          * pre-handler and it returned non-zero, it prepped
342                          * for calling the break_handler below on re-entry
343                          * for jprobe processing, so get out doing nothing
344                          * more here.
345                          */
346                         push_kprobe(kcb, p);
347                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
348                         if (p->pre_handler && p->pre_handler(p, regs))
349                                 return 1;
350                         kcb->kprobe_status = KPROBE_HIT_SS;
351                 }
352                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
353                 return 1;
354         } else if (kprobe_running()) {
355                 p = __this_cpu_read(current_kprobe);
356                 if (p->break_handler && p->break_handler(p, regs)) {
357                         /*
358                          * Continuation after the jprobe completed and
359                          * caused the jprobe_return trap. The jprobe
360                          * break_handler "returns" to the original
361                          * function that still has the kprobe breakpoint
362                          * installed. We continue with single stepping.
363                          */
364                         kcb->kprobe_status = KPROBE_HIT_SS;
365                         enable_singlestep(kcb, regs,
366                                           (unsigned long) p->ainsn.insn);
367                         return 1;
368                 } /* else:
369                    * No kprobe at this address and the current kprobe
370                    * has no break handler (no jprobe!). The kernel just
371                    * exploded, let the standard trap handler pick up the
372                    * pieces.
373                    */
374         } /* else:
375            * No kprobe at this address and no active kprobe. The trap has
376            * not been caused by a kprobe breakpoint. The race of breakpoint
377            * vs. kprobe remove does not exist because on s390 as we use
378            * stop_machine to arm/disarm the breakpoints.
379            */
380         preempt_enable_no_resched();
381         return 0;
382 }
383 NOKPROBE_SYMBOL(kprobe_handler);
384 
385 /*
386  * Function return probe trampoline:
387  *      - init_kprobes() establishes a probepoint here
388  *      - When the probed function returns, this probe
389  *              causes the handlers to fire
390  */
391 static void __used kretprobe_trampoline_holder(void)
392 {
393         asm volatile(".global kretprobe_trampoline\n"
394                      "kretprobe_trampoline: bcr 0,0\n");
395 }
396 
397 /*
398  * Called when the probe at kretprobe trampoline is hit
399  */
400 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
401 {
402         struct kretprobe_instance *ri;
403         struct hlist_head *head, empty_rp;
404         struct hlist_node *tmp;
405         unsigned long flags, orig_ret_address;
406         unsigned long trampoline_address;
407         kprobe_opcode_t *correct_ret_addr;
408 
409         INIT_HLIST_HEAD(&empty_rp);
410         kretprobe_hash_lock(current, &head, &flags);
411 
412         /*
413          * It is possible to have multiple instances associated with a given
414          * task either because an multiple functions in the call path
415          * have a return probe installed on them, and/or more than one return
416          * return probe was registered for a target function.
417          *
418          * We can handle this because:
419          *     - instances are always inserted at the head of the list
420          *     - when multiple return probes are registered for the same
421          *       function, the first instance's ret_addr will point to the
422          *       real return address, and all the rest will point to
423          *       kretprobe_trampoline
424          */
425         ri = NULL;
426         orig_ret_address = 0;
427         correct_ret_addr = NULL;
428         trampoline_address = (unsigned long) &kretprobe_trampoline;
429         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
430                 if (ri->task != current)
431                         /* another task is sharing our hash bucket */
432                         continue;
433 
434                 orig_ret_address = (unsigned long) ri->ret_addr;
435 
436                 if (orig_ret_address != trampoline_address)
437                         /*
438                          * This is the real return address. Any other
439                          * instances associated with this task are for
440                          * other calls deeper on the call stack
441                          */
442                         break;
443         }
444 
445         kretprobe_assert(ri, orig_ret_address, trampoline_address);
446 
447         correct_ret_addr = ri->ret_addr;
448         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
449                 if (ri->task != current)
450                         /* another task is sharing our hash bucket */
451                         continue;
452 
453                 orig_ret_address = (unsigned long) ri->ret_addr;
454 
455                 if (ri->rp && ri->rp->handler) {
456                         ri->ret_addr = correct_ret_addr;
457                         ri->rp->handler(ri, regs);
458                 }
459 
460                 recycle_rp_inst(ri, &empty_rp);
461 
462                 if (orig_ret_address != trampoline_address)
463                         /*
464                          * This is the real return address. Any other
465                          * instances associated with this task are for
466                          * other calls deeper on the call stack
467                          */
468                         break;
469         }
470 
471         regs->psw.addr = orig_ret_address;
472 
473         pop_kprobe(get_kprobe_ctlblk());
474         kretprobe_hash_unlock(current, &flags);
475         preempt_enable_no_resched();
476 
477         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
478                 hlist_del(&ri->hlist);
479                 kfree(ri);
480         }
481         /*
482          * By returning a non-zero value, we are telling
483          * kprobe_handler() that we don't want the post_handler
484          * to run (and have re-enabled preemption)
485          */
486         return 1;
487 }
488 NOKPROBE_SYMBOL(trampoline_probe_handler);
489 
490 /*
491  * Called after single-stepping.  p->addr is the address of the
492  * instruction whose first byte has been replaced by the "breakpoint"
493  * instruction.  To avoid the SMP problems that can occur when we
494  * temporarily put back the original opcode to single-step, we
495  * single-stepped a copy of the instruction.  The address of this
496  * copy is p->ainsn.insn.
497  */
498 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
499 {
500         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
501         unsigned long ip = regs->psw.addr;
502         int fixup = probe_get_fixup_type(p->ainsn.insn);
503 
504         /* Check if the kprobes location is an enabled ftrace caller */
505         if (p->ainsn.is_ftrace_insn) {
506                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
507                 struct ftrace_insn call_insn;
508 
509                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
510                 /*
511                  * A kprobe on an enabled ftrace call site actually single
512                  * stepped an unconditional branch (ftrace nop equivalent).
513                  * Now we need to fixup things and pretend that a brasl r0,...
514                  * was executed instead.
515                  */
516                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
517                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
518                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
519                 }
520         }
521 
522         if (fixup & FIXUP_PSW_NORMAL)
523                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
524 
525         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
526                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
527                 if (ip - (unsigned long) p->ainsn.insn == ilen)
528                         ip = (unsigned long) p->addr + ilen;
529         }
530 
531         if (fixup & FIXUP_RETURN_REGISTER) {
532                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
533                 regs->gprs[reg] += (unsigned long) p->addr -
534                                    (unsigned long) p->ainsn.insn;
535         }
536 
537         disable_singlestep(kcb, regs, ip);
538 }
539 NOKPROBE_SYMBOL(resume_execution);
540 
541 static int post_kprobe_handler(struct pt_regs *regs)
542 {
543         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
544         struct kprobe *p = kprobe_running();
545 
546         if (!p)
547                 return 0;
548 
549         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
550                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
551                 p->post_handler(p, regs, 0);
552         }
553 
554         resume_execution(p, regs);
555         pop_kprobe(kcb);
556         preempt_enable_no_resched();
557 
558         /*
559          * if somebody else is singlestepping across a probe point, psw mask
560          * will have PER set, in which case, continue the remaining processing
561          * of do_single_step, as if this is not a probe hit.
562          */
563         if (regs->psw.mask & PSW_MASK_PER)
564                 return 0;
565 
566         return 1;
567 }
568 NOKPROBE_SYMBOL(post_kprobe_handler);
569 
570 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
571 {
572         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
573         struct kprobe *p = kprobe_running();
574         const struct exception_table_entry *entry;
575 
576         switch(kcb->kprobe_status) {
577         case KPROBE_SWAP_INST:
578                 /* We are here because the instruction replacement failed */
579                 return 0;
580         case KPROBE_HIT_SS:
581         case KPROBE_REENTER:
582                 /*
583                  * We are here because the instruction being single
584                  * stepped caused a page fault. We reset the current
585                  * kprobe and the nip points back to the probe address
586                  * and allow the page fault handler to continue as a
587                  * normal page fault.
588                  */
589                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
590                 pop_kprobe(kcb);
591                 preempt_enable_no_resched();
592                 break;
593         case KPROBE_HIT_ACTIVE:
594         case KPROBE_HIT_SSDONE:
595                 /*
596                  * We increment the nmissed count for accounting,
597                  * we can also use npre/npostfault count for accounting
598                  * these specific fault cases.
599                  */
600                 kprobes_inc_nmissed_count(p);
601 
602                 /*
603                  * We come here because instructions in the pre/post
604                  * handler caused the page_fault, this could happen
605                  * if handler tries to access user space by
606                  * copy_from_user(), get_user() etc. Let the
607                  * user-specified handler try to fix it first.
608                  */
609                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
610                         return 1;
611 
612                 /*
613                  * In case the user-specified fault handler returned
614                  * zero, try to fix up.
615                  */
616                 entry = search_exception_tables(regs->psw.addr);
617                 if (entry) {
618                         regs->psw.addr = extable_fixup(entry);
619                         return 1;
620                 }
621 
622                 /*
623                  * fixup_exception() could not handle it,
624                  * Let do_page_fault() fix it.
625                  */
626                 break;
627         default:
628                 break;
629         }
630         return 0;
631 }
632 NOKPROBE_SYMBOL(kprobe_trap_handler);
633 
634 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
635 {
636         int ret;
637 
638         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
639                 local_irq_disable();
640         ret = kprobe_trap_handler(regs, trapnr);
641         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
642                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
643         return ret;
644 }
645 NOKPROBE_SYMBOL(kprobe_fault_handler);
646 
647 /*
648  * Wrapper routine to for handling exceptions.
649  */
650 int kprobe_exceptions_notify(struct notifier_block *self,
651                              unsigned long val, void *data)
652 {
653         struct die_args *args = (struct die_args *) data;
654         struct pt_regs *regs = args->regs;
655         int ret = NOTIFY_DONE;
656 
657         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
658                 local_irq_disable();
659 
660         switch (val) {
661         case DIE_BPT:
662                 if (kprobe_handler(regs))
663                         ret = NOTIFY_STOP;
664                 break;
665         case DIE_SSTEP:
666                 if (post_kprobe_handler(regs))
667                         ret = NOTIFY_STOP;
668                 break;
669         case DIE_TRAP:
670                 if (!preemptible() && kprobe_running() &&
671                     kprobe_trap_handler(regs, args->trapnr))
672                         ret = NOTIFY_STOP;
673                 break;
674         default:
675                 break;
676         }
677 
678         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
679                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
680 
681         return ret;
682 }
683 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
684 
685 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
686 {
687         struct jprobe *jp = container_of(p, struct jprobe, kp);
688         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
689         unsigned long stack;
690 
691         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
692 
693         /* setup return addr to the jprobe handler routine */
694         regs->psw.addr = (unsigned long) jp->entry;
695         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
696 
697         /* r15 is the stack pointer */
698         stack = (unsigned long) regs->gprs[15];
699 
700         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
701 
702         /*
703          * jprobes use jprobe_return() which skips the normal return
704          * path of the function, and this messes up the accounting of the
705          * function graph tracer to get messed up.
706          *
707          * Pause function graph tracing while performing the jprobe function.
708          */
709         pause_graph_tracing();
710         return 1;
711 }
712 NOKPROBE_SYMBOL(setjmp_pre_handler);
713 
714 void jprobe_return(void)
715 {
716         asm volatile(".word 0x0002");
717 }
718 NOKPROBE_SYMBOL(jprobe_return);
719 
720 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
721 {
722         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
723         unsigned long stack;
724 
725         /* It's OK to start function graph tracing again */
726         unpause_graph_tracing();
727 
728         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
729 
730         /* Put the regs back */
731         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
732         /* put the stack back */
733         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
734         preempt_enable_no_resched();
735         return 1;
736 }
737 NOKPROBE_SYMBOL(longjmp_break_handler);
738 
739 static struct kprobe trampoline = {
740         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
741         .pre_handler = trampoline_probe_handler
742 };
743 
744 int __init arch_init_kprobes(void)
745 {
746         return register_kprobe(&trampoline);
747 }
748 
749 int arch_trampoline_kprobe(struct kprobe *p)
750 {
751         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
752 }
753 NOKPROBE_SYMBOL(arch_trampoline_kprobe);
754 

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