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 #include <asm/sections.h>
  36
  37 #include "../decode-arm.h"
  38 #include "../decode-thumb.h"
  39 #include "core.h"
  40
  41 #define MIN_STACK_SIZE(addr)                            \
  42         min((unsigned long)MAX_STACK_SIZE,              \
  43             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  44
  45 #define flush_insns(addr, size)                         \
  46         flush_icache_range((unsigned long)(addr),       \
  47                            (unsigned long)(addr) +      \
  48                            (size))
  49
  50 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  51 #define JPROBE_MAGIC_ADDR               0xffffffff
  52
  53 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  54 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  55
  56
  57 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  58 {
  59         kprobe_opcode_t insn;
  60         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  61         unsigned long addr = (unsigned long)p->addr;
  62         bool thumb;
  63         kprobe_decode_insn_t *decode_insn;
  64         const union decode_action *actions;
  65         int is;
  66         const struct decode_checker **checkers;
  67
  68 #ifdef CONFIG_THUMB2_KERNEL
  69         thumb = true;
  70         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  71         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
  72         if (is_wide_instruction(insn)) {
  73                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
  74                 insn = __opcode_thumb32_compose(insn, inst2);
  75                 decode_insn = thumb32_probes_decode_insn;
  76                 actions = kprobes_t32_actions;
  77                 checkers = kprobes_t32_checkers;
  78         } else {
  79                 decode_insn = thumb16_probes_decode_insn;
  80                 actions = kprobes_t16_actions;
  81                 checkers = kprobes_t16_checkers;
  82         }
  83 #else /* !CONFIG_THUMB2_KERNEL */
  84         thumb = false;
  85         if (addr & 0x3)
  86                 return -EINVAL;
  87         insn = __mem_to_opcode_arm(*p->addr);
  88         decode_insn = arm_probes_decode_insn;
  89         actions = kprobes_arm_actions;
  90         checkers = kprobes_arm_checkers;
  91 #endif
  92
  93         p->opcode = insn;
  94         p->ainsn.insn = tmp_insn;
  95
  96         switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
  97         case INSN_REJECTED:     /* not supported */
  98                 return -EINVAL;
  99
 100         case INSN_GOOD:         /* instruction uses slot */
 101                 p->ainsn.insn = get_insn_slot();
 102                 if (!p->ainsn.insn)
 103                         return -ENOMEM;
 104                 for (is = 0; is < MAX_INSN_SIZE; ++is)
 105                         p->ainsn.insn[is] = tmp_insn[is];
 106                 flush_insns(p->ainsn.insn,
 107                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 108                 p->ainsn.insn_fn = (probes_insn_fn_t *)
 109                                         ((uintptr_t)p->ainsn.insn | thumb);
 110                 break;
 111
 112         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 113                 p->ainsn.insn = NULL;
 114                 break;
 115         }
 116
 117         /*
 118          * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
 119          * 'str r0, [sp, #-68]' should also be prohibited.
 120          * See __und_svc.
 121          */
 122         if ((p->ainsn.stack_space < 0) ||
 123                         (p->ainsn.stack_space > MAX_STACK_SIZE))
 124                 return -EINVAL;
 125
 126         return 0;
 127 }
 128
 129 void __kprobes arch_arm_kprobe(struct kprobe *p)
 130 {
 131         unsigned int brkp;
 132         void *addr;
 133
 134         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 135                 /* Remove any Thumb flag */
 136                 addr = (void *)((uintptr_t)p->addr & ~1);
 137
 138                 if (is_wide_instruction(p->opcode))
 139                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 140                 else
 141                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 142         } else {
 143                 kprobe_opcode_t insn = p->opcode;
 144
 145                 addr = p->addr;
 146                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 147
 148                 if (insn >= 0xe0000000)
 149                         brkp |= 0xe0000000;  /* Unconditional instruction */
 150                 else
 151                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 152         }
 153
 154         patch_text(addr, brkp);
 155 }
 156
 157 /*
 158  * The actual disarming is done here on each CPU and synchronized using
 159  * stop_machine. This synchronization is necessary on SMP to avoid removing
 160  * a probe between the moment the 'Undefined Instruction' exception is raised
 161  * and the moment the exception handler reads the faulting instruction from
 162  * memory. It is also needed to atomically set the two half-words of a 32-bit
 163  * Thumb breakpoint.
 164  */
 165 struct patch {
 166         void *addr;
 167         unsigned int insn;
 168 };
 169
 170 static int __kprobes_remove_breakpoint(void *data)
 171 {
 172         struct patch *p = data;
 173         __patch_text(p->addr, p->insn);
 174         return 0;
 175 }
 176
 177 void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
 178 {
 179         struct patch p = {
 180                 .addr = addr,
 181                 .insn = insn,
 182         };
 183         stop_machine_cpuslocked(__kprobes_remove_breakpoint, &p,
 184                                 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 (!p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 269                         /*
 270                          * Probe hit but conditional execution check failed,
 271                          * so just skip the instruction and continue as if
 272                          * nothing had happened.
 273                          * In this case, we can skip recursing check too.
 274                          */
 275                         singlestep_skip(p, regs);
 276                 } else if (cur) {
 277                         /* Kprobe is pending, so we're recursing. */
 278                         switch (kcb->kprobe_status) {
 279                         case KPROBE_HIT_ACTIVE:
 280                         case KPROBE_HIT_SSDONE:
 281                         case KPROBE_HIT_SS:
 282                                 /* A pre- or post-handler probe got us here. */
 283                                 kprobes_inc_nmissed_count(p);
 284                                 save_previous_kprobe(kcb);
 285                                 set_current_kprobe(p);
 286                                 kcb->kprobe_status = KPROBE_REENTER;
 287                                 singlestep(p, regs, kcb);
 288                                 restore_previous_kprobe(kcb);
 289                                 break;
 290                         case KPROBE_REENTER:
 291                                 /* A nested probe was hit in FIQ, it is a BUG */
 292                                 pr_warn("Unrecoverable kprobe detected at %p.\n",
 293                                         p->addr);
 294                                 /* fall through */
 295                         default:
 296                                 /* impossible cases */
 297                                 BUG();
 298                         }
 299                 } else {
 300                         /* Probe hit and conditional execution check ok. */
 301                         set_current_kprobe(p);
 302                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 303
 304                         /*
 305                          * If we have no pre-handler or it returned 0, we
 306                          * continue with normal processing.  If we have a
 307                          * pre-handler and it returned non-zero, it prepped
 308                          * for calling the break_handler below on re-entry,
 309                          * so get out doing nothing more here.
 310                          */
 311                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 312                                 kcb->kprobe_status = KPROBE_HIT_SS;
 313                                 singlestep(p, regs, kcb);
 314                                 if (p->post_handler) {
 315                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 316                                         p->post_handler(p, regs, 0);
 317                                 }
 318                                 reset_current_kprobe();
 319                         }
 320                 }
 321         } else if (cur) {
 322                 /* We probably hit a jprobe.  Call its break handler. */
 323                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 324                         kcb->kprobe_status = KPROBE_HIT_SS;
 325                         singlestep(cur, regs, kcb);
 326                         if (cur->post_handler) {
 327                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 328                                 cur->post_handler(cur, regs, 0);
 329                         }
 330                 }
 331                 reset_current_kprobe();
 332         } else {
 333                 /*
 334                  * The probe was removed and a race is in progress.
 335                  * There is nothing we can do about it.  Let's restart
 336                  * the instruction.  By the time we can restart, the
 337                  * real instruction will be there.
 338                  */
 339         }
 340 }
 341
 342 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 343 {
 344         unsigned long flags;
 345         local_irq_save(flags);
 346         kprobe_handler(regs);
 347         local_irq_restore(flags);
 348         return 0;
 349 }
 350
 351 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 352 {
 353         struct kprobe *cur = kprobe_running();
 354         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 355
 356         switch (kcb->kprobe_status) {
 357         case KPROBE_HIT_SS:
 358         case KPROBE_REENTER:
 359                 /*
 360                  * We are here because the instruction being single
 361                  * stepped caused a page fault. We reset the current
 362                  * kprobe and the PC to point back to the probe address
 363                  * and allow the page fault handler to continue as a
 364                  * normal page fault.
 365                  */
 366                 regs->ARM_pc = (long)cur->addr;
 367                 if (kcb->kprobe_status == KPROBE_REENTER) {
 368                         restore_previous_kprobe(kcb);
 369                 } else {
 370                         reset_current_kprobe();
 371                 }
 372                 break;
 373
 374         case KPROBE_HIT_ACTIVE:
 375         case KPROBE_HIT_SSDONE:
 376                 /*
 377                  * We increment the nmissed count for accounting,
 378                  * we can also use npre/npostfault count for accounting
 379                  * these specific fault cases.
 380                  */
 381                 kprobes_inc_nmissed_count(cur);
 382
 383                 /*
 384                  * We come here because instructions in the pre/post
 385                  * handler caused the page_fault, this could happen
 386                  * if handler tries to access user space by
 387                  * copy_from_user(), get_user() etc. Let the
 388                  * user-specified handler try to fix it.
 389                  */
 390                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 391                         return 1;
 392                 break;
 393
 394         default:
 395                 break;
 396         }
 397
 398         return 0;
 399 }
 400
 401 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 402                                        unsigned long val, void *data)
 403 {
 404         /*
 405          * notify_die() is currently never called on ARM,
 406          * so this callback is currently empty.
 407          */
 408         return NOTIFY_DONE;
 409 }
 410
 411 /*
 412  * When a retprobed function returns, trampoline_handler() is called,
 413  * calling the kretprobe's handler. We construct a struct pt_regs to
 414  * give a view of registers r0-r11 to the user return-handler.  This is
 415  * not a complete pt_regs structure, but that should be plenty sufficient
 416  * for kretprobe handlers which should normally be interested in r0 only
 417  * anyway.
 418  */
 419 void __naked __kprobes kretprobe_trampoline(void)
 420 {
 421         __asm__ __volatile__ (
 422                 "stmdb  sp!, {r0 - r11}         \n\t"
 423                 "mov    r0, sp                  \n\t"
 424                 "bl     trampoline_handler      \n\t"
 425                 "mov    lr, r0                  \n\t"
 426                 "ldmia  sp!, {r0 - r11}         \n\t"
 427 #ifdef CONFIG_THUMB2_KERNEL
 428                 "bx     lr                      \n\t"
 429 #else
 430                 "mov    pc, lr                  \n\t"
 431 #endif
 432                 : : : "memory");
 433 }
 434
 435 /* Called from kretprobe_trampoline */
 436 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 437 {
 438         struct kretprobe_instance *ri = NULL;
 439         struct hlist_head *head, empty_rp;
 440         struct hlist_node *tmp;
 441         unsigned long flags, orig_ret_address = 0;
 442         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 443         kprobe_opcode_t *correct_ret_addr = NULL;
 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                 orig_ret_address = (unsigned long)ri->ret_addr;
 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
 479         correct_ret_addr = ri->ret_addr;
 480         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 481                 if (ri->task != current)
 482                         /* another task is sharing our hash bucket */
 483                         continue;
 484
 485                 orig_ret_address = (unsigned long)ri->ret_addr;
 486                 if (ri->rp && ri->rp->handler) {
 487                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 488                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 489                         ri->ret_addr = correct_ret_addr;
 490                         ri->rp->handler(ri, regs);
 491                         __this_cpu_write(current_kprobe, NULL);
 492                 }
 493
 494                 recycle_rp_inst(ri, &empty_rp);
 495
 496                 if (orig_ret_address != trampoline_address)
 497                         /*
 498                          * This is the real return address. Any other
 499                          * instances associated with this task are for
 500                          * other calls deeper on the call stack
 501                          */
 502                         break;
 503         }
 504
 505         kretprobe_hash_unlock(current, &flags);
 506
 507         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 508                 hlist_del(&ri->hlist);
 509                 kfree(ri);
 510         }
 511
 512         return (void *)orig_ret_address;
 513 }
 514
 515 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 516                                       struct pt_regs *regs)
 517 {
 518         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 519
 520         /* Replace the return addr with trampoline addr. */
 521         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 522 }
 523
 524 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 525 {
 526         struct jprobe *jp = container_of(p, struct jprobe, kp);
 527         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 528         long sp_addr = regs->ARM_sp;
 529         long cpsr;
 530
 531         kcb->jprobe_saved_regs = *regs;
 532         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 533         regs->ARM_pc = (long)jp->entry;
 534
 535         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 536 #ifdef CONFIG_THUMB2_KERNEL
 537         /* Set correct Thumb state in cpsr */
 538         if (regs->ARM_pc & 1)
 539                 cpsr |= PSR_T_BIT;
 540         else
 541                 cpsr &= ~PSR_T_BIT;
 542 #endif
 543         regs->ARM_cpsr = cpsr;
 544
 545         preempt_disable();
 546         return 1;
 547 }
 548
 549 void __kprobes jprobe_return(void)
 550 {
 551         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 552
 553         __asm__ __volatile__ (
 554                 /*
 555                  * Setup an empty pt_regs. Fill SP and PC fields as
 556                  * they're needed by longjmp_break_handler.
 557                  *
 558                  * We allocate some slack between the original SP and start of
 559                  * our fabricated regs. To be precise we want to have worst case
 560                  * covered which is STMFD with all 16 regs so we allocate 2 *
 561                  * sizeof(struct_pt_regs)).
 562                  *
 563                  * This is to prevent any simulated instruction from writing
 564                  * over the regs when they are accessing the stack.
 565                  */
 566 #ifdef CONFIG_THUMB2_KERNEL
 567                 "sub    r0, %0, %1              \n\t"
 568                 "mov    sp, r0                  \n\t"
 569 #else
 570                 "sub    sp, %0, %1              \n\t"
 571 #endif
 572                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 573                 "str    %0, [sp, %2]            \n\t"
 574                 "str    r0, [sp, %3]            \n\t"
 575                 "mov    r0, sp                  \n\t"
 576                 "bl     kprobe_handler          \n\t"
 577
 578                 /*
 579                  * Return to the context saved by setjmp_pre_handler
 580                  * and restored by longjmp_break_handler.
 581                  */
 582 #ifdef CONFIG_THUMB2_KERNEL
 583                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 584                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 585                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 586                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 587                                                       /* rfe context */
 588                 "ldmia  sp, {r0 - r12}          \n\t"
 589                 "mov    sp, lr                  \n\t"
 590                 "ldr    lr, [sp], #4            \n\t"
 591                 "rfeia  sp!                     \n\t"
 592 #else
 593                 "ldr    r0, [sp, %4]            \n\t"
 594                 "msr    cpsr_cxsf, r0           \n\t"
 595                 "ldmia  sp, {r0 - pc}           \n\t"
 596 #endif
 597                 :
 598                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 599                   "I" (sizeof(struct pt_regs) * 2),
 600                   "J" (offsetof(struct pt_regs, ARM_sp)),
 601                   "J" (offsetof(struct pt_regs, ARM_pc)),
 602                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 603                   "J" (offsetof(struct pt_regs, ARM_lr))
 604                 : "memory", "cc");
 605 }
 606
 607 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 608 {
 609         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 610         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 611         long orig_sp = regs->ARM_sp;
 612         struct jprobe *jp = container_of(p, struct jprobe, kp);
 613
 614         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 615                 if (orig_sp != stack_addr) {
 616                         struct pt_regs *saved_regs =
 617                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 618                         printk("current sp %lx does not match saved sp %lx\n",
 619                                orig_sp, stack_addr);
 620                         printk("Saved registers for jprobe %p\n", jp);
 621                         show_regs(saved_regs);
 622                         printk("Current registers\n");
 623                         show_regs(regs);
 624                         BUG();
 625                 }
 626                 *regs = kcb->jprobe_saved_regs;
 627                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 628                        MIN_STACK_SIZE(stack_addr));
 629                 preempt_enable_no_resched();
 630                 return 1;
 631         }
 632         return 0;
 633 }
 634
 635 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 636 {
 637         return 0;
 638 }
 639
 640 #ifdef CONFIG_THUMB2_KERNEL
 641
 642 static struct undef_hook kprobes_thumb16_break_hook = {
 643         .instr_mask     = 0xffff,
 644         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 645         .cpsr_mask      = MODE_MASK,
 646         .cpsr_val       = SVC_MODE,
 647         .fn             = kprobe_trap_handler,
 648 };
 649
 650 static struct undef_hook kprobes_thumb32_break_hook = {
 651         .instr_mask     = 0xffffffff,
 652         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 653         .cpsr_mask      = MODE_MASK,
 654         .cpsr_val       = SVC_MODE,
 655         .fn             = kprobe_trap_handler,
 656 };
 657
 658 #else  /* !CONFIG_THUMB2_KERNEL */
 659
 660 static struct undef_hook kprobes_arm_break_hook = {
 661         .instr_mask     = 0x0fffffff,
 662         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 663         .cpsr_mask      = MODE_MASK,
 664         .cpsr_val       = SVC_MODE,
 665         .fn             = kprobe_trap_handler,
 666 };
 667
 668 #endif /* !CONFIG_THUMB2_KERNEL */
 669
 670 int __init arch_init_kprobes()
 671 {
 672         arm_probes_decode_init();
 673 #ifdef CONFIG_THUMB2_KERNEL
 674         register_undef_hook(&kprobes_thumb16_break_hook);
 675         register_undef_hook(&kprobes_thumb32_break_hook);
 676 #else
 677         register_undef_hook(&kprobes_arm_break_hook);
 678 #endif
 679         return 0;
 680 }
 681
 682 bool arch_within_kprobe_blacklist(unsigned long addr)
 683 {
 684         void *a = (void *)addr;
 685
 686         return __in_irqentry_text(addr) ||
 687                in_entry_text(addr) ||
 688                in_idmap_text(addr) ||
 689                memory_contains(__kprobes_text_start, __kprobes_text_end, a, 1);
 690 }