Pileus Git - ~andy/linux/blob - arch/arc/kernel/kprobes.c

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   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 version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/kprobes.h>
  11 #include <linux/slab.h>
  12 #include <linux/module.h>
  13 #include <linux/kprobes.h>
  14 #include <linux/kdebug.h>
  15 #include <linux/sched.h>
  16 #include <linux/uaccess.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/current.h>
  19 #include <asm/disasm.h>
  20
  21 #define MIN_STACK_SIZE(addr)    min((unsigned long)MAX_STACK_SIZE, \
  22                 (unsigned long)current_thread_info() + THREAD_SIZE - (addr))
  23
  24 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  25 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  26
  27 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  28 {
  29         /* Attempt to probe at unaligned address */
  30         if ((unsigned long)p->addr & 0x01)
  31                 return -EINVAL;
  32
  33         /* Address should not be in exception handling code */
  34
  35         p->ainsn.is_short = is_short_instr((unsigned long)p->addr);
  36         p->opcode = *p->addr;
  37
  38         return 0;
  39 }
  40
  41 void __kprobes arch_arm_kprobe(struct kprobe *p)
  42 {
  43         *p->addr = UNIMP_S_INSTRUCTION;
  44
  45         flush_icache_range((unsigned long)p->addr,
  46                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  47 }
  48
  49 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  50 {
  51         *p->addr = p->opcode;
  52
  53         flush_icache_range((unsigned long)p->addr,
  54                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  55 }
  56
  57 void __kprobes arch_remove_kprobe(struct kprobe *p)
  58 {
  59         arch_disarm_kprobe(p);
  60
  61         /* Can we remove the kprobe in the middle of kprobe handling? */
  62         if (p->ainsn.t1_addr) {
  63                 *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
  64
  65                 flush_icache_range((unsigned long)p->ainsn.t1_addr,
  66                                    (unsigned long)p->ainsn.t1_addr +
  67                                    sizeof(kprobe_opcode_t));
  68
  69                 p->ainsn.t1_addr = NULL;
  70         }
  71
  72         if (p->ainsn.t2_addr) {
  73                 *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
  74
  75                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
  76                                    (unsigned long)p->ainsn.t2_addr +
  77                                    sizeof(kprobe_opcode_t));
  78
  79                 p->ainsn.t2_addr = NULL;
  80         }
  81 }
  82
  83 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  84 {
  85         kcb->prev_kprobe.kp = kprobe_running();
  86         kcb->prev_kprobe.status = kcb->kprobe_status;
  87 }
  88
  89 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  90 {
  91         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  92         kcb->kprobe_status = kcb->prev_kprobe.status;
  93 }
  94
  95 static inline void __kprobes set_current_kprobe(struct kprobe *p)
  96 {
  97         __get_cpu_var(current_kprobe) = p;
  98 }
  99
 100 static void __kprobes resume_execution(struct kprobe *p, unsigned long addr,
 101                                        struct pt_regs *regs)
 102 {
 103         /* Remove the trap instructions inserted for single step and
 104          * restore the original instructions
 105          */
 106         if (p->ainsn.t1_addr) {
 107                 *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
 108
 109                 flush_icache_range((unsigned long)p->ainsn.t1_addr,
 110                                    (unsigned long)p->ainsn.t1_addr +
 111                                    sizeof(kprobe_opcode_t));
 112
 113                 p->ainsn.t1_addr = NULL;
 114         }
 115
 116         if (p->ainsn.t2_addr) {
 117                 *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
 118
 119                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
 120                                    (unsigned long)p->ainsn.t2_addr +
 121                                    sizeof(kprobe_opcode_t));
 122
 123                 p->ainsn.t2_addr = NULL;
 124         }
 125
 126         return;
 127 }
 128
 129 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs)
 130 {
 131         unsigned long next_pc;
 132         unsigned long tgt_if_br = 0;
 133         int is_branch;
 134         unsigned long bta;
 135
 136         /* Copy the opcode back to the kprobe location and execute the
 137          * instruction. Because of this we will not be able to get into the
 138          * same kprobe until this kprobe is done
 139          */
 140         *(p->addr) = p->opcode;
 141
 142         flush_icache_range((unsigned long)p->addr,
 143                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
 144
 145         /* Now we insert the trap at the next location after this instruction to
 146          * single step. If it is a branch we insert the trap at possible branch
 147          * targets
 148          */
 149
 150         bta = regs->bta;
 151
 152         if (regs->status32 & 0x40) {
 153                 /* We are in a delay slot with the branch taken */
 154
 155                 next_pc = bta & ~0x01;
 156
 157                 if (!p->ainsn.is_short) {
 158                         if (bta & 0x01)
 159                                 regs->blink += 2;
 160                         else {
 161                                 /* Branch not taken */
 162                                 next_pc += 2;
 163
 164                                 /* next pc is taken from bta after executing the
 165                                  * delay slot instruction
 166                                  */
 167                                 regs->bta += 2;
 168                         }
 169                 }
 170
 171                 is_branch = 0;
 172         } else
 173                 is_branch =
 174                     disasm_next_pc((unsigned long)p->addr, regs,
 175                         (struct callee_regs *) current->thread.callee_reg,
 176                         &next_pc, &tgt_if_br);
 177
 178         p->ainsn.t1_addr = (kprobe_opcode_t *) next_pc;
 179         p->ainsn.t1_opcode = *(p->ainsn.t1_addr);
 180         *(p->ainsn.t1_addr) = TRAP_S_2_INSTRUCTION;
 181
 182         flush_icache_range((unsigned long)p->ainsn.t1_addr,
 183                            (unsigned long)p->ainsn.t1_addr +
 184                            sizeof(kprobe_opcode_t));
 185
 186         if (is_branch) {
 187                 p->ainsn.t2_addr = (kprobe_opcode_t *) tgt_if_br;
 188                 p->ainsn.t2_opcode = *(p->ainsn.t2_addr);
 189                 *(p->ainsn.t2_addr) = TRAP_S_2_INSTRUCTION;
 190
 191                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
 192                                    (unsigned long)p->ainsn.t2_addr +
 193                                    sizeof(kprobe_opcode_t));
 194         }
 195 }
 196
 197 int __kprobes arc_kprobe_handler(unsigned long addr, struct pt_regs *regs)
 198 {
 199         struct kprobe *p;
 200         struct kprobe_ctlblk *kcb;
 201
 202         preempt_disable();
 203
 204         kcb = get_kprobe_ctlblk();
 205         p = get_kprobe((unsigned long *)addr);
 206
 207         if (p) {
 208                 /*
 209                  * We have reentered the kprobe_handler, since another kprobe
 210                  * was hit while within the handler, we save the original
 211                  * kprobes and single step on the instruction of the new probe
 212                  * without calling any user handlers to avoid recursive
 213                  * kprobes.
 214                  */
 215                 if (kprobe_running()) {
 216                         save_previous_kprobe(kcb);
 217                         set_current_kprobe(p);
 218                         kprobes_inc_nmissed_count(p);
 219                         setup_singlestep(p, regs);
 220                         kcb->kprobe_status = KPROBE_REENTER;
 221                         return 1;
 222                 }
 223
 224                 set_current_kprobe(p);
 225                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 226
 227                 /* If we have no pre-handler or it returned 0, we continue with
 228                  * normal processing. If we have a pre-handler and it returned
 229                  * non-zero - which is expected from setjmp_pre_handler for
 230                  * jprobe, we return without single stepping and leave that to
 231                  * the break-handler which is invoked by a kprobe from
 232                  * jprobe_return
 233                  */
 234                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
 235                         setup_singlestep(p, regs);
 236                         kcb->kprobe_status = KPROBE_HIT_SS;
 237                 }
 238
 239                 return 1;
 240         } else if (kprobe_running()) {
 241                 p = __get_cpu_var(current_kprobe);
 242                 if (p->break_handler && p->break_handler(p, regs)) {
 243                         setup_singlestep(p, regs);
 244                         kcb->kprobe_status = KPROBE_HIT_SS;
 245                         return 1;
 246                 }
 247         }
 248
 249         /* no_kprobe: */
 250         preempt_enable_no_resched();
 251         return 0;
 252 }
 253
 254 static int __kprobes arc_post_kprobe_handler(unsigned long addr,
 255                                          struct pt_regs *regs)
 256 {
 257         struct kprobe *cur = kprobe_running();
 258         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 259
 260         if (!cur)
 261                 return 0;
 262
 263         resume_execution(cur, addr, regs);
 264
 265         /* Rearm the kprobe */
 266         arch_arm_kprobe(cur);
 267
 268         /*
 269          * When we return from trap instruction we go to the next instruction
 270          * We restored the actual instruction in resume_exectuiont and we to
 271          * return to the same address and execute it
 272          */
 273         regs->ret = addr;
 274
 275         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 276                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 277                 cur->post_handler(cur, regs, 0);
 278         }
 279
 280         if (kcb->kprobe_status == KPROBE_REENTER) {
 281                 restore_previous_kprobe(kcb);
 282                 goto out;
 283         }
 284
 285         reset_current_kprobe();
 286
 287 out:
 288         preempt_enable_no_resched();
 289         return 1;
 290 }
 291
 292 /*
 293  * Fault can be for the instruction being single stepped or for the
 294  * pre/post handlers in the module.
 295  * This is applicable for applications like user probes, where we have the
 296  * probe in user space and the handlers in the kernel
 297  */
 298
 299 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr)
 300 {
 301         struct kprobe *cur = kprobe_running();
 302         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 303
 304         switch (kcb->kprobe_status) {
 305         case KPROBE_HIT_SS:
 306         case KPROBE_REENTER:
 307                 /*
 308                  * We are here because the instruction being single stepped
 309                  * caused the fault. We reset the current kprobe and allow the
 310                  * exception handler as if it is regular exception. In our
 311                  * case it doesn't matter because the system will be halted
 312                  */
 313                 resume_execution(cur, (unsigned long)cur->addr, regs);
 314
 315                 if (kcb->kprobe_status == KPROBE_REENTER)
 316                         restore_previous_kprobe(kcb);
 317                 else
 318                         reset_current_kprobe();
 319
 320                 preempt_enable_no_resched();
 321                 break;
 322
 323         case KPROBE_HIT_ACTIVE:
 324         case KPROBE_HIT_SSDONE:
 325                 /*
 326                  * We are here because the instructions in the pre/post handler
 327                  * caused the fault.
 328                  */
 329
 330                 /* We increment the nmissed count for accounting,
 331                  * we can also use npre/npostfault count for accouting
 332                  * these specific fault cases.
 333                  */
 334                 kprobes_inc_nmissed_count(cur);
 335
 336                 /*
 337                  * We come here because instructions in the pre/post
 338                  * handler caused the page_fault, this could happen
 339                  * if handler tries to access user space by
 340                  * copy_from_user(), get_user() etc. Let the
 341                  * user-specified handler try to fix it first.
 342                  */
 343                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 344                         return 1;
 345
 346                 /*
 347                  * In case the user-specified fault handler returned zero,
 348                  * try to fix up.
 349                  */
 350                 if (fixup_exception(regs))
 351                         return 1;
 352
 353                 /*
 354                  * fixup_exception() could not handle it,
 355                  * Let do_page_fault() fix it.
 356                  */
 357                 break;
 358
 359         default:
 360                 break;
 361         }
 362         return 0;
 363 }
 364
 365 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 366                                        unsigned long val, void *data)
 367 {
 368         struct die_args *args = data;
 369         unsigned long addr = args->err;
 370         int ret = NOTIFY_DONE;
 371
 372         switch (val) {
 373         case DIE_IERR:
 374                 if (arc_kprobe_handler(addr, args->regs))
 375                         return NOTIFY_STOP;
 376                 break;
 377
 378         case DIE_TRAP:
 379                 if (arc_post_kprobe_handler(addr, args->regs))
 380                         return NOTIFY_STOP;
 381                 break;
 382
 383         default:
 384                 break;
 385         }
 386
 387         return ret;
 388 }
 389
 390 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 391 {
 392         struct jprobe *jp = container_of(p, struct jprobe, kp);
 393         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 394         unsigned long sp_addr = regs->sp;
 395
 396         kcb->jprobe_saved_regs = *regs;
 397         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 398         regs->ret = (unsigned long)(jp->entry);
 399
 400         return 1;
 401 }
 402
 403 void __kprobes jprobe_return(void)
 404 {
 405         __asm__ __volatile__("unimp_s");
 406         return;
 407 }
 408
 409 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 410 {
 411         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 412         unsigned long sp_addr;
 413
 414         *regs = kcb->jprobe_saved_regs;
 415         sp_addr = regs->sp;
 416         memcpy((void *)sp_addr, kcb->jprobes_stack, MIN_STACK_SIZE(sp_addr));
 417         preempt_enable_no_resched();
 418
 419         return 1;
 420 }
 421
 422 static void __used kretprobe_trampoline_holder(void)
 423 {
 424         __asm__ __volatile__(".global kretprobe_trampoline\n"
 425                              "kretprobe_trampoline:\n" "nop\n");
 426 }
 427
 428 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 429                                       struct pt_regs *regs)
 430 {
 431
 432         ri->ret_addr = (kprobe_opcode_t *) regs->blink;
 433
 434         /* Replace the return addr with trampoline addr */
 435         regs->blink = (unsigned long)&kretprobe_trampoline;
 436 }
 437
 438 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 439                                               struct pt_regs *regs)
 440 {
 441         struct kretprobe_instance *ri = NULL;
 442         struct hlist_head *head, empty_rp;
 443         struct hlist_node *tmp;
 444         unsigned long flags, orig_ret_address = 0;
 445         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 446
 447         INIT_HLIST_HEAD(&empty_rp);
 448         kretprobe_hash_lock(current, &head, &flags);
 449
 450         /*
 451          * It is possible to have multiple instances associated with a given
 452          * task either because an multiple functions in the call path
 453          * have a return probe installed on them, and/or more than one return
 454          * return probe was registered for a target function.
 455          *
 456          * We can handle this because:
 457          *     - instances are always inserted at the head of the list
 458          *     - when multiple return probes are registered for the same
 459          *       function, the first instance's ret_addr will point to the
 460          *       real return address, and all the rest will point to
 461          *       kretprobe_trampoline
 462          */
 463         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 464                 if (ri->task != current)
 465                         /* another task is sharing our hash bucket */
 466                         continue;
 467
 468                 if (ri->rp && ri->rp->handler)
 469                         ri->rp->handler(ri, regs);
 470
 471                 orig_ret_address = (unsigned long)ri->ret_addr;
 472                 recycle_rp_inst(ri, &empty_rp);
 473
 474                 if (orig_ret_address != trampoline_address) {
 475                         /*
 476                          * This is the real return address. Any other
 477                          * instances associated with this task are for
 478                          * other calls deeper on the call stack
 479                          */
 480                         break;
 481                 }
 482         }
 483
 484         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 485         regs->ret = orig_ret_address;
 486
 487         reset_current_kprobe();
 488         kretprobe_hash_unlock(current, &flags);
 489         preempt_enable_no_resched();
 490
 491         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 492                 hlist_del(&ri->hlist);
 493                 kfree(ri);
 494         }
 495
 496         /* By returning a non zero value, we are telling the kprobe handler
 497          * that we don't want the post_handler to run
 498          */
 499         return 1;
 500 }
 501
 502 static struct kprobe trampoline_p = {
 503         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 504         .pre_handler = trampoline_probe_handler
 505 };
 506
 507 int __init arch_init_kprobes(void)
 508 {
 509         /* Registering the trampoline code for the kret probe */
 510         return register_kprobe(&trampoline_p);
 511 }
 512
 513 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 514 {
 515         if (p->addr == (kprobe_opcode_t *) &kretprobe_trampoline)
 516                 return 1;
 517
 518         return 0;
 519 }
 520
 521 void trap_is_kprobe(unsigned long cause, unsigned long address,
 522                     struct pt_regs *regs)
 523 {
 524         notify_die(DIE_TRAP, "kprobe_trap", regs, address, cause, SIGTRAP);
 525 }