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