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   1 /*
   2  * Kernel probes (kprobes) for SuperH
   3  *
   4  * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
   5  * Copyright (C) 2006 Lineo Solutions, Inc.
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License.  See the file "COPYING" in the main directory of this archive
   9  * for more details.
  10  */
  11 #include <linux/kprobes.h>
  12 #include <linux/module.h>
  13 #include <linux/ptrace.h>
  14 #include <linux/preempt.h>
  15 #include <linux/kdebug.h>
  16 #include <asm/cacheflush.h>
  17 #include <asm/uaccess.h>
  18
  19 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  20 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  21
  22 static struct kprobe saved_current_opcode;
  23 static struct kprobe saved_next_opcode;
  24 static struct kprobe saved_next_opcode2;
  25
  26 #define OPCODE_JMP(x)   (((x) & 0xF0FF) == 0x402b)
  27 #define OPCODE_JSR(x)   (((x) & 0xF0FF) == 0x400b)
  28 #define OPCODE_BRA(x)   (((x) & 0xF000) == 0xa000)
  29 #define OPCODE_BRAF(x)  (((x) & 0xF0FF) == 0x0023)
  30 #define OPCODE_BSR(x)   (((x) & 0xF000) == 0xb000)
  31 #define OPCODE_BSRF(x)  (((x) & 0xF0FF) == 0x0003)
  32
  33 #define OPCODE_BF_S(x)  (((x) & 0xFF00) == 0x8f00)
  34 #define OPCODE_BT_S(x)  (((x) & 0xFF00) == 0x8d00)
  35
  36 #define OPCODE_BF(x)    (((x) & 0xFF00) == 0x8b00)
  37 #define OPCODE_BT(x)    (((x) & 0xFF00) == 0x8900)
  38
  39 #define OPCODE_RTS(x)   (((x) & 0x000F) == 0x000b)
  40 #define OPCODE_RTE(x)   (((x) & 0xFFFF) == 0x002b)
  41
  42 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  43 {
  44         kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
  45
  46         if (OPCODE_RTE(opcode))
  47                 return -EFAULT; /* Bad breakpoint */
  48
  49         p->opcode = opcode;
  50
  51         return 0;
  52 }
  53
  54 void __kprobes arch_copy_kprobe(struct kprobe *p)
  55 {
  56         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  57         p->opcode = *p->addr;
  58 }
  59
  60 void __kprobes arch_arm_kprobe(struct kprobe *p)
  61 {
  62         *p->addr = BREAKPOINT_INSTRUCTION;
  63         flush_icache_range((unsigned long)p->addr,
  64                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  65 }
  66
  67 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  68 {
  69         *p->addr = p->opcode;
  70         flush_icache_range((unsigned long)p->addr,
  71                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  72 }
  73
  74 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
  75 {
  76         if (*p->addr == BREAKPOINT_INSTRUCTION)
  77                 return 1;
  78
  79         return 0;
  80 }
  81
  82 /**
  83  * If an illegal slot instruction exception occurs for an address
  84  * containing a kprobe, remove the probe.
  85  *
  86  * Returns 0 if the exception was handled successfully, 1 otherwise.
  87  */
  88 int __kprobes kprobe_handle_illslot(unsigned long pc)
  89 {
  90         struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
  91
  92         if (p != NULL) {
  93                 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
  94                        (unsigned int)pc + 2);
  95                 unregister_kprobe(p);
  96                 return 0;
  97         }
  98
  99         return 1;
 100 }
 101
 102 void __kprobes arch_remove_kprobe(struct kprobe *p)
 103 {
 104         if (saved_next_opcode.addr != 0x0) {
 105                 arch_disarm_kprobe(p);
 106                 arch_disarm_kprobe(&saved_next_opcode);
 107                 saved_next_opcode.addr = 0x0;
 108                 saved_next_opcode.opcode = 0x0;
 109
 110                 if (saved_next_opcode2.addr != 0x0) {
 111                         arch_disarm_kprobe(&saved_next_opcode2);
 112                         saved_next_opcode2.addr = 0x0;
 113                         saved_next_opcode2.opcode = 0x0;
 114                 }
 115         }
 116 }
 117
 118 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 119 {
 120         kcb->prev_kprobe.kp = kprobe_running();
 121         kcb->prev_kprobe.status = kcb->kprobe_status;
 122 }
 123
 124 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 125 {
 126         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 127         kcb->kprobe_status = kcb->prev_kprobe.status;
 128 }
 129
 130 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 131                                          struct kprobe_ctlblk *kcb)
 132 {
 133         __get_cpu_var(current_kprobe) = p;
 134 }
 135
 136 /*
 137  * Singlestep is implemented by disabling the current kprobe and setting one
 138  * on the next instruction, following branches. Two probes are set if the
 139  * branch is conditional.
 140  */
 141 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 142 {
 143         kprobe_opcode_t *addr = NULL;
 144         saved_current_opcode.addr = (kprobe_opcode_t *) (regs->pc);
 145         addr = saved_current_opcode.addr;
 146
 147         if (p != NULL) {
 148                 arch_disarm_kprobe(p);
 149
 150                 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
 151                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 152                         saved_next_opcode.addr =
 153                             (kprobe_opcode_t *) regs->regs[reg_nr];
 154                 } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
 155                         unsigned long disp = (p->opcode & 0x0FFF);
 156                         saved_next_opcode.addr =
 157                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 158
 159                 } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
 160                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 161                         saved_next_opcode.addr =
 162                             (kprobe_opcode_t *) (regs->pc + 4 +
 163                                                  regs->regs[reg_nr]);
 164
 165                 } else if (OPCODE_RTS(p->opcode)) {
 166                         saved_next_opcode.addr = (kprobe_opcode_t *) regs->pr;
 167
 168                 } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
 169                         unsigned long disp = (p->opcode & 0x00FF);
 170                         /* case 1 */
 171                         saved_next_opcode.addr = p->addr + 1;
 172                         /* case 2 */
 173                         saved_next_opcode2.addr =
 174                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 175                         saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
 176                         arch_arm_kprobe(&saved_next_opcode2);
 177
 178                 } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
 179                         unsigned long disp = (p->opcode & 0x00FF);
 180                         /* case 1 */
 181                         saved_next_opcode.addr = p->addr + 2;
 182                         /* case 2 */
 183                         saved_next_opcode2.addr =
 184                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 185                         saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
 186                         arch_arm_kprobe(&saved_next_opcode2);
 187
 188                 } else {
 189                         saved_next_opcode.addr = p->addr + 1;
 190                 }
 191
 192                 saved_next_opcode.opcode = *(saved_next_opcode.addr);
 193                 arch_arm_kprobe(&saved_next_opcode);
 194         }
 195 }
 196
 197 /* Called with kretprobe_lock held */
 198 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 199                                       struct pt_regs *regs)
 200 {
 201         ri->ret_addr = (kprobe_opcode_t *) regs->pr;
 202
 203         /* Replace the return addr with trampoline addr */
 204         regs->pr = (unsigned long)kretprobe_trampoline;
 205 }
 206
 207 static int __kprobes kprobe_handler(struct pt_regs *regs)
 208 {
 209         struct kprobe *p;
 210         int ret = 0;
 211         kprobe_opcode_t *addr = NULL;
 212         struct kprobe_ctlblk *kcb;
 213
 214         /*
 215          * We don't want to be preempted for the entire
 216          * duration of kprobe processing
 217          */
 218         preempt_disable();
 219         kcb = get_kprobe_ctlblk();
 220
 221         addr = (kprobe_opcode_t *) (regs->pc);
 222
 223         /* Check we're not actually recursing */
 224         if (kprobe_running()) {
 225                 p = get_kprobe(addr);
 226                 if (p) {
 227                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 228                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 229                                 goto no_kprobe;
 230                         }
 231                         /* We have reentered the kprobe_handler(), since
 232                          * another probe was hit while within the handler.
 233                          * We here save the original kprobes variables and
 234                          * just single step on the instruction of the new probe
 235                          * without calling any user handlers.
 236                          */
 237                         save_previous_kprobe(kcb);
 238                         set_current_kprobe(p, regs, kcb);
 239                         kprobes_inc_nmissed_count(p);
 240                         prepare_singlestep(p, regs);
 241                         kcb->kprobe_status = KPROBE_REENTER;
 242                         return 1;
 243                 } else {
 244                         p = __get_cpu_var(current_kprobe);
 245                         if (p->break_handler && p->break_handler(p, regs)) {
 246                                 goto ss_probe;
 247                         }
 248                 }
 249                 goto no_kprobe;
 250         }
 251
 252         p = get_kprobe(addr);
 253         if (!p) {
 254                 /* Not one of ours: let kernel handle it */
 255                 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
 256                         /*
 257                          * The breakpoint instruction was removed right
 258                          * after we hit it. Another cpu has removed
 259                          * either a probepoint or a debugger breakpoint
 260                          * at this address. In either case, no further
 261                          * handling of this interrupt is appropriate.
 262                          */
 263                         ret = 1;
 264                 }
 265
 266                 goto no_kprobe;
 267         }
 268
 269         set_current_kprobe(p, regs, kcb);
 270         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 271
 272         if (p->pre_handler && p->pre_handler(p, regs))
 273                 /* handler has already set things up, so skip ss setup */
 274                 return 1;
 275
 276 ss_probe:
 277         prepare_singlestep(p, regs);
 278         kcb->kprobe_status = KPROBE_HIT_SS;
 279         return 1;
 280
 281 no_kprobe:
 282         preempt_enable_no_resched();
 283         return ret;
 284 }
 285
 286 /*
 287  * For function-return probes, init_kprobes() establishes a probepoint
 288  * here. When a retprobed function returns, this probe is hit and
 289  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 290  */
 291 static void __used kretprobe_trampoline_holder(void)
 292 {
 293         asm volatile (".globl kretprobe_trampoline\n"
 294                       "kretprobe_trampoline:\n\t"
 295                       "nop\n");
 296 }
 297
 298 /*
 299  * Called when we hit the probe point at kretprobe_trampoline
 300  */
 301 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 302 {
 303         struct kretprobe_instance *ri = NULL;
 304         struct hlist_head *head, empty_rp;
 305         struct hlist_node *node, *tmp;
 306         unsigned long flags, orig_ret_address = 0;
 307         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 308
 309         INIT_HLIST_HEAD(&empty_rp);
 310         kretprobe_hash_lock(current, &head, &flags);
 311
 312         /*
 313          * It is possible to have multiple instances associated with a given
 314          * task either because an multiple functions in the call path
 315          * have a return probe installed on them, and/or more then one return
 316          * return probe was registered for a target function.
 317          *
 318          * We can handle this because:
 319          *     - instances are always inserted at the head of the list
 320          *     - when multiple return probes are registered for the same
 321          *       function, the first instance's ret_addr will point to the
 322          *       real return address, and all the rest will point to
 323          *       kretprobe_trampoline
 324          */
 325         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 326                 if (ri->task != current)
 327                         /* another task is sharing our hash bucket */
 328                         continue;
 329
 330                 if (ri->rp && ri->rp->handler) {
 331                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 332                         ri->rp->handler(ri, regs);
 333                         __get_cpu_var(current_kprobe) = NULL;
 334                 }
 335
 336                 orig_ret_address = (unsigned long)ri->ret_addr;
 337                 recycle_rp_inst(ri, &empty_rp);
 338
 339                 if (orig_ret_address != trampoline_address)
 340                         /*
 341                          * This is the real return address. Any other
 342                          * instances associated with this task are for
 343                          * other calls deeper on the call stack
 344                          */
 345                         break;
 346         }
 347
 348         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 349
 350         regs->pc = orig_ret_address;
 351         kretprobe_hash_unlock(current, &flags);
 352
 353         preempt_enable_no_resched();
 354
 355         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 356                 hlist_del(&ri->hlist);
 357                 kfree(ri);
 358         }
 359
 360         return orig_ret_address;
 361 }
 362
 363 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 364 {
 365         struct kprobe *cur = kprobe_running();
 366         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 367         kprobe_opcode_t *addr = NULL;
 368         struct kprobe *p = NULL;
 369
 370         if (!cur)
 371                 return 0;
 372
 373         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 374                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 375                 cur->post_handler(cur, regs, 0);
 376         }
 377
 378         if (saved_next_opcode.addr != 0x0) {
 379                 arch_disarm_kprobe(&saved_next_opcode);
 380                 saved_next_opcode.addr = 0x0;
 381                 saved_next_opcode.opcode = 0x0;
 382
 383                 addr = saved_current_opcode.addr;
 384                 saved_current_opcode.addr = 0x0;
 385
 386                 p = get_kprobe(addr);
 387                 arch_arm_kprobe(p);
 388
 389                 if (saved_next_opcode2.addr != 0x0) {
 390                         arch_disarm_kprobe(&saved_next_opcode2);
 391                         saved_next_opcode2.addr = 0x0;
 392                         saved_next_opcode2.opcode = 0x0;
 393                 }
 394         }
 395
 396         /* Restore back the original saved kprobes variables and continue. */
 397         if (kcb->kprobe_status == KPROBE_REENTER) {
 398                 restore_previous_kprobe(kcb);
 399                 goto out;
 400         }
 401
 402         reset_current_kprobe();
 403
 404 out:
 405         preempt_enable_no_resched();
 406
 407         return 1;
 408 }
 409
 410 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 411 {
 412         struct kprobe *cur = kprobe_running();
 413         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 414         const struct exception_table_entry *entry;
 415
 416         switch (kcb->kprobe_status) {
 417         case KPROBE_HIT_SS:
 418         case KPROBE_REENTER:
 419                 /*
 420                  * We are here because the instruction being single
 421                  * stepped caused a page fault. We reset the current
 422                  * kprobe, point the pc back to the probe address
 423                  * and allow the page fault handler to continue as a
 424                  * normal page fault.
 425                  */
 426                 regs->pc = (unsigned long)cur->addr;
 427                 if (kcb->kprobe_status == KPROBE_REENTER)
 428                         restore_previous_kprobe(kcb);
 429                 else
 430                         reset_current_kprobe();
 431                 preempt_enable_no_resched();
 432                 break;
 433         case KPROBE_HIT_ACTIVE:
 434         case KPROBE_HIT_SSDONE:
 435                 /*
 436                  * We increment the nmissed count for accounting,
 437                  * we can also use npre/npostfault count for accounting
 438                  * these specific fault cases.
 439                  */
 440                 kprobes_inc_nmissed_count(cur);
 441
 442                 /*
 443                  * We come here because instructions in the pre/post
 444                  * handler caused the page_fault, this could happen
 445                  * if handler tries to access user space by
 446                  * copy_from_user(), get_user() etc. Let the
 447                  * user-specified handler try to fix it first.
 448                  */
 449                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 450                         return 1;
 451
 452                 /*
 453                  * In case the user-specified fault handler returned
 454                  * zero, try to fix up.
 455                  */
 456                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 457                         regs->pc = entry->fixup;
 458                         return 1;
 459                 }
 460
 461                 /*
 462                  * fixup_exception() could not handle it,
 463                  * Let do_page_fault() fix it.
 464                  */
 465                 break;
 466         default:
 467                 break;
 468         }
 469
 470         return 0;
 471 }
 472
 473 /*
 474  * Wrapper routine to for handling exceptions.
 475  */
 476 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 477                                        unsigned long val, void *data)
 478 {
 479         struct kprobe *p = NULL;
 480         struct die_args *args = (struct die_args *)data;
 481         int ret = NOTIFY_DONE;
 482         kprobe_opcode_t *addr = NULL;
 483         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 484
 485         addr = (kprobe_opcode_t *) (args->regs->pc);
 486         if (val == DIE_TRAP) {
 487                 if (!kprobe_running()) {
 488                         if (kprobe_handler(args->regs)) {
 489                                 ret = NOTIFY_STOP;
 490                         } else {
 491                                 /* Not a kprobe trap */
 492                                 ret = NOTIFY_DONE;
 493                         }
 494                 } else {
 495                         p = get_kprobe(addr);
 496                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 497                             (kcb->kprobe_status == KPROBE_REENTER)) {
 498                                 if (post_kprobe_handler(args->regs))
 499                                         ret = NOTIFY_STOP;
 500                         } else {
 501                                 if (kprobe_handler(args->regs)) {
 502                                         ret = NOTIFY_STOP;
 503                                 } else {
 504                                         p = __get_cpu_var(current_kprobe);
 505                                         if (p->break_handler &&
 506                                             p->break_handler(p, args->regs))
 507                                                 ret = NOTIFY_STOP;
 508                                 }
 509                         }
 510                 }
 511         }
 512
 513         return ret;
 514 }
 515
 516 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 517 {
 518         struct jprobe *jp = container_of(p, struct jprobe, kp);
 519         unsigned long addr;
 520         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 521
 522         kcb->jprobe_saved_regs = *regs;
 523         kcb->jprobe_saved_r15 = regs->regs[15];
 524         addr = kcb->jprobe_saved_r15;
 525
 526         /*
 527          * TBD: As Linus pointed out, gcc assumes that the callee
 528          * owns the argument space and could overwrite it, e.g.
 529          * tailcall optimization. So, to be absolutely safe
 530          * we also save and restore enough stack bytes to cover
 531          * the argument area.
 532          */
 533         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 534                MIN_STACK_SIZE(addr));
 535
 536         regs->pc = (unsigned long)(jp->entry);
 537
 538         return 1;
 539 }
 540
 541 void __kprobes jprobe_return(void)
 542 {
 543         asm volatile ("trapa #0x3a\n\t" "jprobe_return_end:\n\t" "nop\n\t");
 544 }
 545
 546 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 547 {
 548         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 549         unsigned long stack_addr = kcb->jprobe_saved_r15;
 550         u8 *addr = (u8 *)regs->pc;
 551
 552         if ((addr >= (u8 *)jprobe_return) &&
 553             (addr <= (u8 *)jprobe_return_end)) {
 554                 *regs = kcb->jprobe_saved_regs;
 555
 556                 memcpy((kprobe_opcode_t *)stack_addr, kcb->jprobes_stack,
 557                        MIN_STACK_SIZE(stack_addr));
 558
 559                 kcb->kprobe_status = KPROBE_HIT_SS;
 560                 preempt_enable_no_resched();
 561                 return 1;
 562         }
 563
 564         return 0;
 565 }
 566
 567 static struct kprobe trampoline_p = {
 568         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
 569         .pre_handler = trampoline_probe_handler
 570 };
 571
 572 int __init arch_init_kprobes(void)
 573 {
 574         saved_next_opcode.addr = 0x0;
 575         saved_next_opcode.opcode = 0x0;
 576
 577         saved_current_opcode.addr = 0x0;
 578         saved_current_opcode.opcode = 0x0;
 579
 580         saved_next_opcode2.addr = 0x0;
 581         saved_next_opcode2.opcode = 0x0;
 582
 583         return register_kprobe(&trampoline_p);
 584 }