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Linux/arch/arm/probes/kprobes/core.c

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  1 /*
  2  * arch/arm/kernel/kprobes.c
  3  *
  4  * Kprobes on ARM
  5  *
  6  * Abhishek Sagar <sagar.abhishek@gmail.com>
  7  * Copyright (C) 2006, 2007 Motorola Inc.
  8  *
  9  * Nicolas Pitre <nico@marvell.com>
 10  * Copyright (C) 2007 Marvell Ltd.
 11  *
 12  * This program is free software; you can redistribute it and/or modify
 13  * it under the terms of the GNU General Public License version 2 as
 14  * published by the Free Software Foundation.
 15  *
 16  * This program is distributed in the hope that it will be useful,
 17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 19  * General Public License for more details.
 20  */
 21 
 22 #include <linux/kernel.h>
 23 #include <linux/kprobes.h>
 24 #include <linux/module.h>
 25 #include <linux/slab.h>
 26 #include <linux/stop_machine.h>
 27 #include <linux/stringify.h>
 28 #include <asm/traps.h>
 29 #include <asm/opcodes.h>
 30 #include <asm/cacheflush.h>
 31 #include <linux/percpu.h>
 32 #include <linux/bug.h>
 33 #include <asm/patch.h>
 34 
 35 #include "../decode-arm.h"
 36 #include "../decode-thumb.h"
 37 #include "core.h"
 38 
 39 #define MIN_STACK_SIZE(addr)                            \
 40         min((unsigned long)MAX_STACK_SIZE,              \
 41             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
 42 
 43 #define flush_insns(addr, size)                         \
 44         flush_icache_range((unsigned long)(addr),       \
 45                            (unsigned long)(addr) +      \
 46                            (size))
 47 
 48 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
 49 #define JPROBE_MAGIC_ADDR               0xffffffff
 50 
 51 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 52 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 53 
 54 
 55 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 56 {
 57         kprobe_opcode_t insn;
 58         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
 59         unsigned long addr = (unsigned long)p->addr;
 60         bool thumb;
 61         kprobe_decode_insn_t *decode_insn;
 62         const union decode_action *actions;
 63         int is;
 64         const struct decode_checker **checkers;
 65 
 66         if (in_exception_text(addr))
 67                 return -EINVAL;
 68 
 69 #ifdef CONFIG_THUMB2_KERNEL
 70         thumb = true;
 71         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
 72         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
 73         if (is_wide_instruction(insn)) {
 74                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
 75                 insn = __opcode_thumb32_compose(insn, inst2);
 76                 decode_insn = thumb32_probes_decode_insn;
 77                 actions = kprobes_t32_actions;
 78                 checkers = kprobes_t32_checkers;
 79         } else {
 80                 decode_insn = thumb16_probes_decode_insn;
 81                 actions = kprobes_t16_actions;
 82                 checkers = kprobes_t16_checkers;
 83         }
 84 #else /* !CONFIG_THUMB2_KERNEL */
 85         thumb = false;
 86         if (addr & 0x3)
 87                 return -EINVAL;
 88         insn = __mem_to_opcode_arm(*p->addr);
 89         decode_insn = arm_probes_decode_insn;
 90         actions = kprobes_arm_actions;
 91         checkers = kprobes_arm_checkers;
 92 #endif
 93 
 94         p->opcode = insn;
 95         p->ainsn.insn = tmp_insn;
 96 
 97         switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
 98         case INSN_REJECTED:     /* not supported */
 99                 return -EINVAL;
100 
101         case INSN_GOOD:         /* instruction uses slot */
102                 p->ainsn.insn = get_insn_slot();
103                 if (!p->ainsn.insn)
104                         return -ENOMEM;
105                 for (is = 0; is < MAX_INSN_SIZE; ++is)
106                         p->ainsn.insn[is] = tmp_insn[is];
107                 flush_insns(p->ainsn.insn,
108                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
109                 p->ainsn.insn_fn = (probes_insn_fn_t *)
110                                         ((uintptr_t)p->ainsn.insn | thumb);
111                 break;
112 
113         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
114                 p->ainsn.insn = NULL;
115                 break;
116         }
117 
118         /*
119          * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
120          * 'str r0, [sp, #-68]' should also be prohibited.
121          * See __und_svc.
122          */
123         if ((p->ainsn.stack_space < 0) ||
124                         (p->ainsn.stack_space > MAX_STACK_SIZE))
125                 return -EINVAL;
126 
127         return 0;
128 }
129 
130 void __kprobes arch_arm_kprobe(struct kprobe *p)
131 {
132         unsigned int brkp;
133         void *addr;
134 
135         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
136                 /* Remove any Thumb flag */
137                 addr = (void *)((uintptr_t)p->addr & ~1);
138 
139                 if (is_wide_instruction(p->opcode))
140                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
141                 else
142                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
143         } else {
144                 kprobe_opcode_t insn = p->opcode;
145 
146                 addr = p->addr;
147                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
148 
149                 if (insn >= 0xe0000000)
150                         brkp |= 0xe0000000;  /* Unconditional instruction */
151                 else
152                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
153         }
154 
155         patch_text(addr, brkp);
156 }
157 
158 /*
159  * The actual disarming is done here on each CPU and synchronized using
160  * stop_machine. This synchronization is necessary on SMP to avoid removing
161  * a probe between the moment the 'Undefined Instruction' exception is raised
162  * and the moment the exception handler reads the faulting instruction from
163  * memory. It is also needed to atomically set the two half-words of a 32-bit
164  * Thumb breakpoint.
165  */
166 struct patch {
167         void *addr;
168         unsigned int insn;
169 };
170 
171 static int __kprobes_remove_breakpoint(void *data)
172 {
173         struct patch *p = data;
174         __patch_text(p->addr, p->insn);
175         return 0;
176 }
177 
178 void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
179 {
180         struct patch p = {
181                 .addr = addr,
182                 .insn = insn,
183         };
184         stop_machine(__kprobes_remove_breakpoint, &p, cpu_online_mask);
185 }
186 
187 void __kprobes arch_disarm_kprobe(struct kprobe *p)
188 {
189         kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
190                         p->opcode);
191 }
192 
193 void __kprobes arch_remove_kprobe(struct kprobe *p)
194 {
195         if (p->ainsn.insn) {
196                 free_insn_slot(p->ainsn.insn, 0);
197                 p->ainsn.insn = NULL;
198         }
199 }
200 
201 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
202 {
203         kcb->prev_kprobe.kp = kprobe_running();
204         kcb->prev_kprobe.status = kcb->kprobe_status;
205 }
206 
207 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
208 {
209         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
210         kcb->kprobe_status = kcb->prev_kprobe.status;
211 }
212 
213 static void __kprobes set_current_kprobe(struct kprobe *p)
214 {
215         __this_cpu_write(current_kprobe, p);
216 }
217 
218 static void __kprobes
219 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
220 {
221 #ifdef CONFIG_THUMB2_KERNEL
222         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
223         if (is_wide_instruction(p->opcode))
224                 regs->ARM_pc += 4;
225         else
226                 regs->ARM_pc += 2;
227 #else
228         regs->ARM_pc += 4;
229 #endif
230 }
231 
232 static inline void __kprobes
233 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
234 {
235         p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
236 }
237 
238 /*
239  * Called with IRQs disabled. IRQs must remain disabled from that point
240  * all the way until processing this kprobe is complete.  The current
241  * kprobes implementation cannot process more than one nested level of
242  * kprobe, and that level is reserved for user kprobe handlers, so we can't
243  * risk encountering a new kprobe in an interrupt handler.
244  */
245 void __kprobes kprobe_handler(struct pt_regs *regs)
246 {
247         struct kprobe *p, *cur;
248         struct kprobe_ctlblk *kcb;
249 
250         kcb = get_kprobe_ctlblk();
251         cur = kprobe_running();
252 
253 #ifdef CONFIG_THUMB2_KERNEL
254         /*
255          * First look for a probe which was registered using an address with
256          * bit 0 set, this is the usual situation for pointers to Thumb code.
257          * If not found, fallback to looking for one with bit 0 clear.
258          */
259         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
260         if (!p)
261                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
262 
263 #else /* ! CONFIG_THUMB2_KERNEL */
264         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
265 #endif
266 
267         if (p) {
268                 if (cur) {
269                         /* Kprobe is pending, so we're recursing. */
270                         switch (kcb->kprobe_status) {
271                         case KPROBE_HIT_ACTIVE:
272                         case KPROBE_HIT_SSDONE:
273                                 /* A pre- or post-handler probe got us here. */
274                                 kprobes_inc_nmissed_count(p);
275                                 save_previous_kprobe(kcb);
276                                 set_current_kprobe(p);
277                                 kcb->kprobe_status = KPROBE_REENTER;
278                                 singlestep(p, regs, kcb);
279                                 restore_previous_kprobe(kcb);
280                                 break;
281                         default:
282                                 /* impossible cases */
283                                 BUG();
284                         }
285                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
286                         /* Probe hit and conditional execution check ok. */
287                         set_current_kprobe(p);
288                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
289 
290                         /*
291                          * If we have no pre-handler or it returned 0, we
292                          * continue with normal processing.  If we have a
293                          * pre-handler and it returned non-zero, it prepped
294                          * for calling the break_handler below on re-entry,
295                          * so get out doing nothing more here.
296                          */
297                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
298                                 kcb->kprobe_status = KPROBE_HIT_SS;
299                                 singlestep(p, regs, kcb);
300                                 if (p->post_handler) {
301                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
302                                         p->post_handler(p, regs, 0);
303                                 }
304                                 reset_current_kprobe();
305                         }
306                 } else {
307                         /*
308                          * Probe hit but conditional execution check failed,
309                          * so just skip the instruction and continue as if
310                          * nothing had happened.
311                          */
312                         singlestep_skip(p, regs);
313                 }
314         } else if (cur) {
315                 /* We probably hit a jprobe.  Call its break handler. */
316                 if (cur->break_handler && cur->break_handler(cur, regs)) {
317                         kcb->kprobe_status = KPROBE_HIT_SS;
318                         singlestep(cur, regs, kcb);
319                         if (cur->post_handler) {
320                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
321                                 cur->post_handler(cur, regs, 0);
322                         }
323                 }
324                 reset_current_kprobe();
325         } else {
326                 /*
327                  * The probe was removed and a race is in progress.
328                  * There is nothing we can do about it.  Let's restart
329                  * the instruction.  By the time we can restart, the
330                  * real instruction will be there.
331                  */
332         }
333 }
334 
335 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
336 {
337         unsigned long flags;
338         local_irq_save(flags);
339         kprobe_handler(regs);
340         local_irq_restore(flags);
341         return 0;
342 }
343 
344 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
345 {
346         struct kprobe *cur = kprobe_running();
347         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
348 
349         switch (kcb->kprobe_status) {
350         case KPROBE_HIT_SS:
351         case KPROBE_REENTER:
352                 /*
353                  * We are here because the instruction being single
354                  * stepped caused a page fault. We reset the current
355                  * kprobe and the PC to point back to the probe address
356                  * and allow the page fault handler to continue as a
357                  * normal page fault.
358                  */
359                 regs->ARM_pc = (long)cur->addr;
360                 if (kcb->kprobe_status == KPROBE_REENTER) {
361                         restore_previous_kprobe(kcb);
362                 } else {
363                         reset_current_kprobe();
364                 }
365                 break;
366 
367         case KPROBE_HIT_ACTIVE:
368         case KPROBE_HIT_SSDONE:
369                 /*
370                  * We increment the nmissed count for accounting,
371                  * we can also use npre/npostfault count for accounting
372                  * these specific fault cases.
373                  */
374                 kprobes_inc_nmissed_count(cur);
375 
376                 /*
377                  * We come here because instructions in the pre/post
378                  * handler caused the page_fault, this could happen
379                  * if handler tries to access user space by
380                  * copy_from_user(), get_user() etc. Let the
381                  * user-specified handler try to fix it.
382                  */
383                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
384                         return 1;
385                 break;
386 
387         default:
388                 break;
389         }
390 
391         return 0;
392 }
393 
394 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
395                                        unsigned long val, void *data)
396 {
397         /*
398          * notify_die() is currently never called on ARM,
399          * so this callback is currently empty.
400          */
401         return NOTIFY_DONE;
402 }
403 
404 /*
405  * When a retprobed function returns, trampoline_handler() is called,
406  * calling the kretprobe's handler. We construct a struct pt_regs to
407  * give a view of registers r0-r11 to the user return-handler.  This is
408  * not a complete pt_regs structure, but that should be plenty sufficient
409  * for kretprobe handlers which should normally be interested in r0 only
410  * anyway.
411  */
412 void __naked __kprobes kretprobe_trampoline(void)
413 {
414         __asm__ __volatile__ (
415                 "stmdb  sp!, {r0 - r11}         \n\t"
416                 "mov    r0, sp                  \n\t"
417                 "bl     trampoline_handler      \n\t"
418                 "mov    lr, r0                  \n\t"
419                 "ldmia  sp!, {r0 - r11}         \n\t"
420 #ifdef CONFIG_THUMB2_KERNEL
421                 "bx     lr                      \n\t"
422 #else
423                 "mov    pc, lr                  \n\t"
424 #endif
425                 : : : "memory");
426 }
427 
428 /* Called from kretprobe_trampoline */
429 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
430 {
431         struct kretprobe_instance *ri = NULL;
432         struct hlist_head *head, empty_rp;
433         struct hlist_node *tmp;
434         unsigned long flags, orig_ret_address = 0;
435         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
436 
437         INIT_HLIST_HEAD(&empty_rp);
438         kretprobe_hash_lock(current, &head, &flags);
439 
440         /*
441          * It is possible to have multiple instances associated with a given
442          * task either because multiple functions in the call path have
443          * a return probe installed on them, and/or more than one return
444          * probe was registered for a target function.
445          *
446          * We can handle this because:
447          *     - instances are always inserted at the head of the list
448          *     - when multiple return probes are registered for the same
449          *       function, the first instance's ret_addr will point to the
450          *       real return address, and all the rest will point to
451          *       kretprobe_trampoline
452          */
453         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
454                 if (ri->task != current)
455                         /* another task is sharing our hash bucket */
456                         continue;
457 
458                 if (ri->rp && ri->rp->handler) {
459                         __this_cpu_write(current_kprobe, &ri->rp->kp);
460                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
461                         ri->rp->handler(ri, regs);
462                         __this_cpu_write(current_kprobe, NULL);
463                 }
464 
465                 orig_ret_address = (unsigned long)ri->ret_addr;
466                 recycle_rp_inst(ri, &empty_rp);
467 
468                 if (orig_ret_address != trampoline_address)
469                         /*
470                          * This is the real return address. Any other
471                          * instances associated with this task are for
472                          * other calls deeper on the call stack
473                          */
474                         break;
475         }
476 
477         kretprobe_assert(ri, orig_ret_address, trampoline_address);
478         kretprobe_hash_unlock(current, &flags);
479 
480         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
481                 hlist_del(&ri->hlist);
482                 kfree(ri);
483         }
484 
485         return (void *)orig_ret_address;
486 }
487 
488 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
489                                       struct pt_regs *regs)
490 {
491         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
492 
493         /* Replace the return addr with trampoline addr. */
494         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
495 }
496 
497 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
498 {
499         struct jprobe *jp = container_of(p, struct jprobe, kp);
500         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
501         long sp_addr = regs->ARM_sp;
502         long cpsr;
503 
504         kcb->jprobe_saved_regs = *regs;
505         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
506         regs->ARM_pc = (long)jp->entry;
507 
508         cpsr = regs->ARM_cpsr | PSR_I_BIT;
509 #ifdef CONFIG_THUMB2_KERNEL
510         /* Set correct Thumb state in cpsr */
511         if (regs->ARM_pc & 1)
512                 cpsr |= PSR_T_BIT;
513         else
514                 cpsr &= ~PSR_T_BIT;
515 #endif
516         regs->ARM_cpsr = cpsr;
517 
518         preempt_disable();
519         return 1;
520 }
521 
522 void __kprobes jprobe_return(void)
523 {
524         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
525 
526         __asm__ __volatile__ (
527                 /*
528                  * Setup an empty pt_regs. Fill SP and PC fields as
529                  * they're needed by longjmp_break_handler.
530                  *
531                  * We allocate some slack between the original SP and start of
532                  * our fabricated regs. To be precise we want to have worst case
533                  * covered which is STMFD with all 16 regs so we allocate 2 *
534                  * sizeof(struct_pt_regs)).
535                  *
536                  * This is to prevent any simulated instruction from writing
537                  * over the regs when they are accessing the stack.
538                  */
539 #ifdef CONFIG_THUMB2_KERNEL
540                 "sub    r0, %0, %1              \n\t"
541                 "mov    sp, r0                  \n\t"
542 #else
543                 "sub    sp, %0, %1              \n\t"
544 #endif
545                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
546                 "str    %0, [sp, %2]            \n\t"
547                 "str    r0, [sp, %3]            \n\t"
548                 "mov    r0, sp                  \n\t"
549                 "bl     kprobe_handler          \n\t"
550 
551                 /*
552                  * Return to the context saved by setjmp_pre_handler
553                  * and restored by longjmp_break_handler.
554                  */
555 #ifdef CONFIG_THUMB2_KERNEL
556                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
557                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
558                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
559                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
560                                                       /* rfe context */
561                 "ldmia  sp, {r0 - r12}          \n\t"
562                 "mov    sp, lr                  \n\t"
563                 "ldr    lr, [sp], #4            \n\t"
564                 "rfeia  sp!                     \n\t"
565 #else
566                 "ldr    r0, [sp, %4]            \n\t"
567                 "msr    cpsr_cxsf, r0           \n\t"
568                 "ldmia  sp, {r0 - pc}           \n\t"
569 #endif
570                 :
571                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
572                   "I" (sizeof(struct pt_regs) * 2),
573                   "J" (offsetof(struct pt_regs, ARM_sp)),
574                   "J" (offsetof(struct pt_regs, ARM_pc)),
575                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
576                   "J" (offsetof(struct pt_regs, ARM_lr))
577                 : "memory", "cc");
578 }
579 
580 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
581 {
582         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
583         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
584         long orig_sp = regs->ARM_sp;
585         struct jprobe *jp = container_of(p, struct jprobe, kp);
586 
587         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
588                 if (orig_sp != stack_addr) {
589                         struct pt_regs *saved_regs =
590                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
591                         printk("current sp %lx does not match saved sp %lx\n",
592                                orig_sp, stack_addr);
593                         printk("Saved registers for jprobe %p\n", jp);
594                         show_regs(saved_regs);
595                         printk("Current registers\n");
596                         show_regs(regs);
597                         BUG();
598                 }
599                 *regs = kcb->jprobe_saved_regs;
600                 memcpy((void *)stack_addr, kcb->jprobes_stack,
601                        MIN_STACK_SIZE(stack_addr));
602                 preempt_enable_no_resched();
603                 return 1;
604         }
605         return 0;
606 }
607 
608 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
609 {
610         return 0;
611 }
612 
613 #ifdef CONFIG_THUMB2_KERNEL
614 
615 static struct undef_hook kprobes_thumb16_break_hook = {
616         .instr_mask     = 0xffff,
617         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
618         .cpsr_mask      = MODE_MASK,
619         .cpsr_val       = SVC_MODE,
620         .fn             = kprobe_trap_handler,
621 };
622 
623 static struct undef_hook kprobes_thumb32_break_hook = {
624         .instr_mask     = 0xffffffff,
625         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
626         .cpsr_mask      = MODE_MASK,
627         .cpsr_val       = SVC_MODE,
628         .fn             = kprobe_trap_handler,
629 };
630 
631 #else  /* !CONFIG_THUMB2_KERNEL */
632 
633 static struct undef_hook kprobes_arm_break_hook = {
634         .instr_mask     = 0x0fffffff,
635         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
636         .cpsr_mask      = MODE_MASK,
637         .cpsr_val       = SVC_MODE,
638         .fn             = kprobe_trap_handler,
639 };
640 
641 #endif /* !CONFIG_THUMB2_KERNEL */
642 
643 int __init arch_init_kprobes()
644 {
645         arm_probes_decode_init();
646 #ifdef CONFIG_THUMB2_KERNEL
647         register_undef_hook(&kprobes_thumb16_break_hook);
648         register_undef_hook(&kprobes_thumb32_break_hook);
649 #else
650         register_undef_hook(&kprobes_arm_break_hook);
651 #endif
652         return 0;
653 }
654 

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