arch/arm/probes/kprobes/core.c

   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/sched/debug.h>
  28 #include <linux/stringify.h>
  29 #include <asm/traps.h>
  30 #include <asm/opcodes.h>
  31 #include <asm/cacheflush.h>
  32 #include <linux/percpu.h>
  33 #include <linux/bug.h>
  34 #include <asm/patch.h>
  35
  36 #include "../decode-arm.h"
  37 #include "../decode-thumb.h"
  38 #include "core.h"
  39
  40 #define MIN_STACK_SIZE(addr)                            \
  41         min((unsigned long)MAX_STACK_SIZE,              \
  42             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  43
  44 #define flush_insns(addr, size)                         \
  45         flush_icache_range((unsigned long)(addr),       \
  46                            (unsigned long)(addr) +      \
  47                            (size))
  48
  49 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  50 #define JPROBE_MAGIC_ADDR               0xffffffff
  51
  52 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  53 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  54
  55
  56 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  57 {
  58         kprobe_opcode_t insn;
  59         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  60         unsigned long addr = (unsigned long)p->addr;
  61         bool thumb;
  62         kprobe_decode_insn_t *decode_insn;
  63         const union decode_action *actions;
  64         int is;
  65         const struct decode_checker **checkers;
  66
  67         if (in_exception_text(addr))
  68                 return -EINVAL;
  69
  70 #ifdef CONFIG_THUMB2_KERNEL
  71         thumb = true;
  72         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  73         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
  74         if (is_wide_instruction(insn)) {
  75                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
  76                 insn = __opcode_thumb32_compose(insn, inst2);
  77                 decode_insn = thumb32_probes_decode_insn;
  78                 actions = kprobes_t32_actions;
  79                 checkers = kprobes_t32_checkers;
  80         } else {
  81                 decode_insn = thumb16_probes_decode_insn;
  82                 actions = kprobes_t16_actions;
  83                 checkers = kprobes_t16_checkers;
  84         }
  85 #else /* !CONFIG_THUMB2_KERNEL */
  86         thumb = false;
  87         if (addr & 0x3)
  88                 return -EINVAL;
  89         insn = __mem_to_opcode_arm(*p->addr);
  90         decode_insn = arm_probes_decode_insn;
  91         actions = kprobes_arm_actions;
  92         checkers = kprobes_arm_checkers;
  93 #endif
  94
  95         p->opcode = insn;
  96         p->ainsn.insn = tmp_insn;
  97
  98         switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
  99         case INSN_REJECTED:     /* not supported */
 100                 return -EINVAL;
 101
 102         case INSN_GOOD:         /* instruction uses slot */
 103                 p->ainsn.insn = get_insn_slot();
 104                 if (!p->ainsn.insn)
 105                         return -ENOMEM;
 106                 for (is = 0; is < MAX_INSN_SIZE; ++is)
 107                         p->ainsn.insn[is] = tmp_insn[is];
 108                 flush_insns(p->ainsn.insn,
 109                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 110                 p->ainsn.insn_fn = (probes_insn_fn_t *)
 111                                         ((uintptr_t)p->ainsn.insn | thumb);
 112                 break;
 113
 114         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 115                 p->ainsn.insn = NULL;
 116                 break;
 117         }
 118
 119         /*
 120          * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
 121          * 'str r0, [sp, #-68]' should also be prohibited.
 122          * See __und_svc.
 123          */
 124         if ((p->ainsn.stack_space < 0) ||
 125                         (p->ainsn.stack_space > MAX_STACK_SIZE))
 126                 return -EINVAL;
 127
 128         return 0;
 129 }
 130
 131 void __kprobes arch_arm_kprobe(struct kprobe *p)
 132 {
 133         unsigned int brkp;
 134         void *addr;
 135
 136         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 137                 /* Remove any Thumb flag */
 138                 addr = (void *)((uintptr_t)p->addr & ~1);
 139
 140                 if (is_wide_instruction(p->opcode))
 141                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 142                 else
 143                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 144         } else {
 145                 kprobe_opcode_t insn = p->opcode;
 146
 147                 addr = p->addr;
 148                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 149
 150                 if (insn >= 0xe0000000)
 151                         brkp |= 0xe0000000;  /* Unconditional instruction */
 152                 else
 153                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 154         }
 155
 156         patch_text(addr, brkp);
 157 }
 158
 159 /*
 160  * The actual disarming is done here on each CPU and synchronized using
 161  * stop_machine. This synchronization is necessary on SMP to avoid removing
 162  * a probe between the moment the 'Undefined Instruction' exception is raised
 163  * and the moment the exception handler reads the faulting instruction from
 164  * memory. It is also needed to atomically set the two half-words of a 32-bit
 165  * Thumb breakpoint.
 166  */
 167 struct patch {
 168         void *addr;
 169         unsigned int insn;
 170 };
 171
 172 static int __kprobes_remove_breakpoint(void *data)
 173 {
 174         struct patch *p = data;
 175         __patch_text(p->addr, p->insn);
 176         return 0;
 177 }
 178
 179 void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
 180 {
 181         struct patch p = {
 182                 .addr = addr,
 183                 .insn = insn,
 184         };
 185         stop_machine(__kprobes_remove_breakpoint, &p, cpu_online_mask);
 186 }
 187
 188 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 189 {
 190         kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
 191                         p->opcode);
 192 }
 193
 194 void __kprobes arch_remove_kprobe(struct kprobe *p)
 195 {
 196         if (p->ainsn.insn) {
 197                 free_insn_slot(p->ainsn.insn, 0);
 198                 p->ainsn.insn = NULL;
 199         }
 200 }
 201
 202 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 203 {
 204         kcb->prev_kprobe.kp = kprobe_running();
 205         kcb->prev_kprobe.status = kcb->kprobe_status;
 206 }
 207
 208 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 209 {
 210         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 211         kcb->kprobe_status = kcb->prev_kprobe.status;
 212 }
 213
 214 static void __kprobes set_current_kprobe(struct kprobe *p)
 215 {
 216         __this_cpu_write(current_kprobe, p);
 217 }
 218
 219 static void __kprobes
 220 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 221 {
 222 #ifdef CONFIG_THUMB2_KERNEL
 223         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 224         if (is_wide_instruction(p->opcode))
 225                 regs->ARM_pc += 4;
 226         else
 227                 regs->ARM_pc += 2;
 228 #else
 229         regs->ARM_pc += 4;
 230 #endif
 231 }
 232
 233 static inline void __kprobes
 234 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 235 {
 236         p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
 237 }
 238
 239 /*
 240  * Called with IRQs disabled. IRQs must remain disabled from that point
 241  * all the way until processing this kprobe is complete.  The current
 242  * kprobes implementation cannot process more than one nested level of
 243  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 244  * risk encountering a new kprobe in an interrupt handler.
 245  */
 246 void __kprobes kprobe_handler(struct pt_regs *regs)
 247 {
 248         struct kprobe *p, *cur;
 249         struct kprobe_ctlblk *kcb;
 250
 251         kcb = get_kprobe_ctlblk();
 252         cur = kprobe_running();
 253
 254 #ifdef CONFIG_THUMB2_KERNEL
 255         /*
 256          * First look for a probe which was registered using an address with
 257          * bit 0 set, this is the usual situation for pointers to Thumb code.
 258          * If not found, fallback to looking for one with bit 0 clear.
 259          */
 260         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 261         if (!p)
 262                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 263
 264 #else /* ! CONFIG_THUMB2_KERNEL */
 265         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 266 #endif
 267
 268         if (p) {
 269                 if (!p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 270                         /*
 271                          * Probe hit but conditional execution check failed,
 272                          * so just skip the instruction and continue as if
 273                          * nothing had happened.
 274                          * In this case, we can skip recursing check too.
 275                          */
 276                         singlestep_skip(p, regs);
 277                 } else if (cur) {
 278                         /* Kprobe is pending, so we're recursing. */
 279                         switch (kcb->kprobe_status) {
 280                         case KPROBE_HIT_ACTIVE:
 281                         case KPROBE_HIT_SSDONE:
 282                         case KPROBE_HIT_SS:
 283                                 /* A pre- or post-handler probe got us here. */
 284                                 kprobes_inc_nmissed_count(p);
 285                                 save_previous_kprobe(kcb);
 286                                 set_current_kprobe(p);
 287                                 kcb->kprobe_status = KPROBE_REENTER;
 288                                 singlestep(p, regs, kcb);
 289                                 restore_previous_kprobe(kcb);
 290                                 break;
 291                         case KPROBE_REENTER:
 292                                 /* A nested probe was hit in FIQ, it is a BUG */
 293                                 pr_warn("Unrecoverable kprobe detected at %p.\n",
 294                                         p->addr);
 295                                 /* fall through */
 296                         default:
 297                                 /* impossible cases */
 298                                 BUG();
 299                         }
 300                 } else {
 301                         /* Probe hit and conditional execution check ok. */
 302                         set_current_kprobe(p);
 303                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 304
 305                         /*
 306                          * If we have no pre-handler or it returned 0, we
 307                          * continue with normal processing.  If we have a
 308                          * pre-handler and it returned non-zero, it prepped
 309                          * for calling the break_handler below on re-entry,
 310                          * so get out doing nothing more here.
 311                          */
 312                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 313                                 kcb->kprobe_status = KPROBE_HIT_SS;
 314                                 singlestep(p, regs, kcb);
 315                                 if (p->post_handler) {
 316                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 317                                         p->post_handler(p, regs, 0);
 318                                 }
 319                                 reset_current_kprobe();
 320                         }
 321                 }
 322         } else if (cur) {
 323                 /* We probably hit a jprobe.  Call its break handler. */
 324                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 325                         kcb->kprobe_status = KPROBE_HIT_SS;
 326                         singlestep(cur, regs, kcb);
 327                         if (cur->post_handler) {
 328                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 329                                 cur->post_handler(cur, regs, 0);
 330                         }
 331                 }
 332                 reset_current_kprobe();
 333         } else {
 334                 /*
 335                  * The probe was removed and a race is in progress.
 336                  * There is nothing we can do about it.  Let's restart
 337                  * the instruction.  By the time we can restart, the
 338                  * real instruction will be there.
 339                  */
 340         }
 341 }
 342
 343 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 344 {
 345         unsigned long flags;
 346         local_irq_save(flags);
 347         kprobe_handler(regs);
 348         local_irq_restore(flags);
 349         return 0;
 350 }
 351
 352 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 353 {
 354         struct kprobe *cur = kprobe_running();
 355         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 356
 357         switch (kcb->kprobe_status) {
 358         case KPROBE_HIT_SS:
 359         case KPROBE_REENTER:
 360                 /*
 361                  * We are here because the instruction being single
 362                  * stepped caused a page fault. We reset the current
 363                  * kprobe and the PC to point back to the probe address
 364                  * and allow the page fault handler to continue as a
 365                  * normal page fault.
 366                  */
 367                 regs->ARM_pc = (long)cur->addr;
 368                 if (kcb->kprobe_status == KPROBE_REENTER) {
 369                         restore_previous_kprobe(kcb);
 370                 } else {
 371                         reset_current_kprobe();
 372                 }
 373                 break;
 374
 375         case KPROBE_HIT_ACTIVE:
 376         case KPROBE_HIT_SSDONE:
 377                 /*
 378                  * We increment the nmissed count for accounting,
 379                  * we can also use npre/npostfault count for accounting
 380                  * these specific fault cases.
 381                  */
 382                 kprobes_inc_nmissed_count(cur);
 383
 384                 /*
 385                  * We come here because instructions in the pre/post
 386                  * handler caused the page_fault, this could happen
 387                  * if handler tries to access user space by
 388                  * copy_from_user(), get_user() etc. Let the
 389                  * user-specified handler try to fix it.
 390                  */
 391                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 392                         return 1;
 393                 break;
 394
 395         default:
 396                 break;
 397         }
 398
 399         return 0;
 400 }
 401
 402 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 403                                        unsigned long val, void *data)
 404 {
 405         /*
 406          * notify_die() is currently never called on ARM,
 407          * so this callback is currently empty.
 408          */
 409         return NOTIFY_DONE;
 410 }
 411
 412 /*
 413  * When a retprobed function returns, trampoline_handler() is called,
 414  * calling the kretprobe's handler. We construct a struct pt_regs to
 415  * give a view of registers r0-r11 to the user return-handler.  This is
 416  * not a complete pt_regs structure, but that should be plenty sufficient
 417  * for kretprobe handlers which should normally be interested in r0 only
 418  * anyway.
 419  */
 420 void __naked __kprobes kretprobe_trampoline(void)
 421 {
 422         __asm__ __volatile__ (
 423                 "stmdb  sp!, {r0 - r11}         \n\t"
 424                 "mov    r0, sp                  \n\t"
 425                 "bl     trampoline_handler      \n\t"
 426                 "mov    lr, r0                  \n\t"
 427                 "ldmia  sp!, {r0 - r11}         \n\t"
 428 #ifdef CONFIG_THUMB2_KERNEL
 429                 "bx     lr                      \n\t"
 430 #else
 431                 "mov    pc, lr                  \n\t"
 432 #endif
 433                 : : : "memory");
 434 }
 435
 436 /* Called from kretprobe_trampoline */
 437 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 438 {
 439         struct kretprobe_instance *ri = NULL;
 440         struct hlist_head *head, empty_rp;
 441         struct hlist_node *tmp;
 442         unsigned long flags, orig_ret_address = 0;
 443         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 444
 445         INIT_HLIST_HEAD(&empty_rp);
 446         kretprobe_hash_lock(current, &head, &flags);
 447
 448         /*
 449          * It is possible to have multiple instances associated with a given
 450          * task either because multiple functions in the call path have
 451          * a return probe installed on them, and/or more than one return
 452          * probe was registered for a target function.
 453          *
 454          * We can handle this because:
 455          *     - instances are always inserted at the head of the list
 456          *     - when multiple return probes are registered for the same
 457          *       function, the first instance's ret_addr will point to the
 458          *       real return address, and all the rest will point to
 459          *       kretprobe_trampoline
 460          */
 461         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 462                 if (ri->task != current)
 463                         /* another task is sharing our hash bucket */
 464                         continue;
 465
 466                 if (ri->rp && ri->rp->handler) {
 467                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 468                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 469                         ri->rp->handler(ri, regs);
 470                         __this_cpu_write(current_kprobe, NULL);
 471                 }
 472
 473                 orig_ret_address = (unsigned long)ri->ret_addr;
 474                 recycle_rp_inst(ri, &empty_rp);
 475
 476                 if (orig_ret_address != trampoline_address)
 477                         /*
 478                          * This is the real return address. Any other
 479                          * instances associated with this task are for
 480                          * other calls deeper on the call stack
 481                          */
 482                         break;
 483         }
 484
 485         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 486         kretprobe_hash_unlock(current, &flags);
 487
 488         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 489                 hlist_del(&ri->hlist);
 490                 kfree(ri);
 491         }
 492
 493         return (void *)orig_ret_address;
 494 }
 495
 496 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 497                                       struct pt_regs *regs)
 498 {
 499         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 500
 501         /* Replace the return addr with trampoline addr. */
 502         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 503 }
 504
 505 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 506 {
 507         struct jprobe *jp = container_of(p, struct jprobe, kp);
 508         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 509         long sp_addr = regs->ARM_sp;
 510         long cpsr;
 511
 512         kcb->jprobe_saved_regs = *regs;
 513         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 514         regs->ARM_pc = (long)jp->entry;
 515
 516         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 517 #ifdef CONFIG_THUMB2_KERNEL
 518         /* Set correct Thumb state in cpsr */
 519         if (regs->ARM_pc & 1)
 520                 cpsr |= PSR_T_BIT;
 521         else
 522                 cpsr &= ~PSR_T_BIT;
 523 #endif
 524         regs->ARM_cpsr = cpsr;
 525
 526         preempt_disable();
 527         return 1;
 528 }
 529
 530 void __kprobes jprobe_return(void)
 531 {
 532         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 533
 534         __asm__ __volatile__ (
 535                 /*
 536                  * Setup an empty pt_regs. Fill SP and PC fields as
 537                  * they're needed by longjmp_break_handler.
 538                  *
 539                  * We allocate some slack between the original SP and start of
 540                  * our fabricated regs. To be precise we want to have worst case
 541                  * covered which is STMFD with all 16 regs so we allocate 2 *
 542                  * sizeof(struct_pt_regs)).
 543                  *
 544                  * This is to prevent any simulated instruction from writing
 545                  * over the regs when they are accessing the stack.
 546                  */
 547 #ifdef CONFIG_THUMB2_KERNEL
 548                 "sub    r0, %0, %1              \n\t"
 549                 "mov    sp, r0                  \n\t"
 550 #else
 551                 "sub    sp, %0, %1              \n\t"
 552 #endif
 553                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 554                 "str    %0, [sp, %2]            \n\t"
 555                 "str    r0, [sp, %3]            \n\t"
 556                 "mov    r0, sp                  \n\t"
 557                 "bl     kprobe_handler          \n\t"
 558
 559                 /*
 560                  * Return to the context saved by setjmp_pre_handler
 561                  * and restored by longjmp_break_handler.
 562                  */
 563 #ifdef CONFIG_THUMB2_KERNEL
 564                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 565                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 566                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 567                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 568                                                       /* rfe context */
 569                 "ldmia  sp, {r0 - r12}          \n\t"
 570                 "mov    sp, lr                  \n\t"
 571                 "ldr    lr, [sp], #4            \n\t"
 572                 "rfeia  sp!                     \n\t"
 573 #else
 574                 "ldr    r0, [sp, %4]            \n\t"
 575                 "msr    cpsr_cxsf, r0           \n\t"
 576                 "ldmia  sp, {r0 - pc}           \n\t"
 577 #endif
 578                 :
 579                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 580                   "I" (sizeof(struct pt_regs) * 2),
 581                   "J" (offsetof(struct pt_regs, ARM_sp)),
 582                   "J" (offsetof(struct pt_regs, ARM_pc)),
 583                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 584                   "J" (offsetof(struct pt_regs, ARM_lr))
 585                 : "memory", "cc");
 586 }
 587
 588 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 589 {
 590         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 591         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 592         long orig_sp = regs->ARM_sp;
 593         struct jprobe *jp = container_of(p, struct jprobe, kp);
 594
 595         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 596                 if (orig_sp != stack_addr) {
 597                         struct pt_regs *saved_regs =
 598                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 599                         printk("current sp %lx does not match saved sp %lx\n",
 600                                orig_sp, stack_addr);
 601                         printk("Saved registers for jprobe %p\n", jp);
 602                         show_regs(saved_regs);
 603                         printk("Current registers\n");
 604                         show_regs(regs);
 605                         BUG();
 606                 }
 607                 *regs = kcb->jprobe_saved_regs;
 608                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 609                        MIN_STACK_SIZE(stack_addr));
 610                 preempt_enable_no_resched();
 611                 return 1;
 612         }
 613         return 0;
 614 }
 615
 616 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 617 {
 618         return 0;
 619 }
 620
 621 #ifdef CONFIG_THUMB2_KERNEL
 622
 623 static struct undef_hook kprobes_thumb16_break_hook = {
 624         .instr_mask     = 0xffff,
 625         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 626         .cpsr_mask      = MODE_MASK,
 627         .cpsr_val       = SVC_MODE,
 628         .fn             = kprobe_trap_handler,
 629 };
 630
 631 static struct undef_hook kprobes_thumb32_break_hook = {
 632         .instr_mask     = 0xffffffff,
 633         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 634         .cpsr_mask      = MODE_MASK,
 635         .cpsr_val       = SVC_MODE,
 636         .fn             = kprobe_trap_handler,
 637 };
 638
 639 #else  /* !CONFIG_THUMB2_KERNEL */
 640
 641 static struct undef_hook kprobes_arm_break_hook = {
 642         .instr_mask     = 0x0fffffff,
 643         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 644         .cpsr_mask      = MODE_MASK,
 645         .cpsr_val       = SVC_MODE,
 646         .fn             = kprobe_trap_handler,
 647 };
 648
 649 #endif /* !CONFIG_THUMB2_KERNEL */
 650
 651 int __init arch_init_kprobes()
 652 {
 653         arm_probes_decode_init();
 654 #ifdef CONFIG_THUMB2_KERNEL
 655         register_undef_hook(&kprobes_thumb16_break_hook);
 656         register_undef_hook(&kprobes_thumb32_break_hook);
 657 #else
 658         register_undef_hook(&kprobes_arm_break_hook);
 659 #endif
 660         return 0;
 661 }