arch/sh/kernel/kprobes.c

   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 <linux/slab.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/uaccess.h>
  19
  20 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  21 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  22
  23 static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
  24 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
  25 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);
  26
  27 #define OPCODE_JMP(x)   (((x) & 0xF0FF) == 0x402b)
  28 #define OPCODE_JSR(x)   (((x) & 0xF0FF) == 0x400b)
  29 #define OPCODE_BRA(x)   (((x) & 0xF000) == 0xa000)
  30 #define OPCODE_BRAF(x)  (((x) & 0xF0FF) == 0x0023)
  31 #define OPCODE_BSR(x)   (((x) & 0xF000) == 0xb000)
  32 #define OPCODE_BSRF(x)  (((x) & 0xF0FF) == 0x0003)
  33
  34 #define OPCODE_BF_S(x)  (((x) & 0xFF00) == 0x8f00)
  35 #define OPCODE_BT_S(x)  (((x) & 0xFF00) == 0x8d00)
  36
  37 #define OPCODE_BF(x)    (((x) & 0xFF00) == 0x8b00)
  38 #define OPCODE_BT(x)    (((x) & 0xFF00) == 0x8900)
  39
  40 #define OPCODE_RTS(x)   (((x) & 0x000F) == 0x000b)
  41 #define OPCODE_RTE(x)   (((x) & 0xFFFF) == 0x002b)
  42
  43 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  44 {
  45         kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
  46
  47         if (OPCODE_RTE(opcode))
  48                 return -EFAULT; /* Bad breakpoint */
  49
  50         p->opcode = opcode;
  51
  52         return 0;
  53 }
  54
  55 void __kprobes arch_copy_kprobe(struct kprobe *p)
  56 {
  57         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  58         p->opcode = *p->addr;
  59 }
  60
  61 void __kprobes arch_arm_kprobe(struct kprobe *p)
  62 {
  63         *p->addr = BREAKPOINT_INSTRUCTION;
  64         flush_icache_range((unsigned long)p->addr,
  65                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  66 }
  67
  68 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  69 {
  70         *p->addr = p->opcode;
  71         flush_icache_range((unsigned long)p->addr,
  72                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  73 }
  74
  75 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
  76 {
  77         if (*p->addr == BREAKPOINT_INSTRUCTION)
  78                 return 1;
  79
  80         return 0;
  81 }
  82
  83 /**
  84  * If an illegal slot instruction exception occurs for an address
  85  * containing a kprobe, remove the probe.
  86  *
  87  * Returns 0 if the exception was handled successfully, 1 otherwise.
  88  */
  89 int __kprobes kprobe_handle_illslot(unsigned long pc)
  90 {
  91         struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
  92
  93         if (p != NULL) {
  94                 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
  95                        (unsigned int)pc + 2);
  96                 unregister_kprobe(p);
  97                 return 0;
  98         }
  99
 100         return 1;
 101 }
 102
 103 void __kprobes arch_remove_kprobe(struct kprobe *p)
 104 {
 105         struct kprobe *saved = &__get_cpu_var(saved_next_opcode);
 106
 107         if (saved->addr) {
 108                 arch_disarm_kprobe(p);
 109                 arch_disarm_kprobe(saved);
 110
 111                 saved->addr = NULL;
 112                 saved->opcode = 0;
 113
 114                 saved = &__get_cpu_var(saved_next_opcode2);
 115                 if (saved->addr) {
 116                         arch_disarm_kprobe(saved);
 117
 118                         saved->addr = NULL;
 119                         saved->opcode = 0;
 120                 }
 121         }
 122 }
 123
 124 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 125 {
 126         kcb->prev_kprobe.kp = kprobe_running();
 127         kcb->prev_kprobe.status = kcb->kprobe_status;
 128 }
 129
 130 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 131 {
 132         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 133         kcb->kprobe_status = kcb->prev_kprobe.status;
 134 }
 135
 136 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 137                                          struct kprobe_ctlblk *kcb)
 138 {
 139         __get_cpu_var(current_kprobe) = p;
 140 }
 141
 142 /*
 143  * Singlestep is implemented by disabling the current kprobe and setting one
 144  * on the next instruction, following branches. Two probes are set if the
 145  * branch is conditional.
 146  */
 147 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 148 {
 149         __get_cpu_var(saved_current_opcode).addr = (kprobe_opcode_t *)regs->pc;
 150
 151         if (p != NULL) {
 152                 struct kprobe *op1, *op2;
 153
 154                 arch_disarm_kprobe(p);
 155
 156                 op1 = &__get_cpu_var(saved_next_opcode);
 157                 op2 = &__get_cpu_var(saved_next_opcode2);
 158
 159                 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
 160                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 161                         op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
 162                 } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
 163                         unsigned long disp = (p->opcode & 0x0FFF);
 164                         op1->addr =
 165                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 166
 167                 } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
 168                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 169                         op1->addr =
 170                             (kprobe_opcode_t *) (regs->pc + 4 +
 171                                                  regs->regs[reg_nr]);
 172
 173                 } else if (OPCODE_RTS(p->opcode)) {
 174                         op1->addr = (kprobe_opcode_t *) regs->pr;
 175
 176                 } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
 177                         unsigned long disp = (p->opcode & 0x00FF);
 178                         /* case 1 */
 179                         op1->addr = p->addr + 1;
 180                         /* case 2 */
 181                         op2->addr =
 182                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 183                         op2->opcode = *(op2->addr);
 184                         arch_arm_kprobe(op2);
 185
 186                 } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
 187                         unsigned long disp = (p->opcode & 0x00FF);
 188                         /* case 1 */
 189                         op1->addr = p->addr + 2;
 190                         /* case 2 */
 191                         op2->addr =
 192                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 193                         op2->opcode = *(op2->addr);
 194                         arch_arm_kprobe(op2);
 195
 196                 } else {
 197                         op1->addr = p->addr + 1;
 198                 }
 199
 200                 op1->opcode = *(op1->addr);
 201                 arch_arm_kprobe(op1);
 202         }
 203 }
 204
 205 /* Called with kretprobe_lock held */
 206 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 207                                       struct pt_regs *regs)
 208 {
 209         ri->ret_addr = (kprobe_opcode_t *) regs->pr;
 210
 211         /* Replace the return addr with trampoline addr */
 212         regs->pr = (unsigned long)kretprobe_trampoline;
 213 }
 214
 215 static int __kprobes kprobe_handler(struct pt_regs *regs)
 216 {
 217         struct kprobe *p;
 218         int ret = 0;
 219         kprobe_opcode_t *addr = NULL;
 220         struct kprobe_ctlblk *kcb;
 221
 222         /*
 223          * We don't want to be preempted for the entire
 224          * duration of kprobe processing
 225          */
 226         preempt_disable();
 227         kcb = get_kprobe_ctlblk();
 228
 229         addr = (kprobe_opcode_t *) (regs->pc);
 230
 231         /* Check we're not actually recursing */
 232         if (kprobe_running()) {
 233                 p = get_kprobe(addr);
 234                 if (p) {
 235                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 236                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 237                                 goto no_kprobe;
 238                         }
 239                         /* We have reentered the kprobe_handler(), since
 240                          * another probe was hit while within the handler.
 241                          * We here save the original kprobes variables and
 242                          * just single step on the instruction of the new probe
 243                          * without calling any user handlers.
 244                          */
 245                         save_previous_kprobe(kcb);
 246                         set_current_kprobe(p, regs, kcb);
 247                         kprobes_inc_nmissed_count(p);
 248                         prepare_singlestep(p, regs);
 249                         kcb->kprobe_status = KPROBE_REENTER;
 250                         return 1;
 251                 } else {
 252                         p = __get_cpu_var(current_kprobe);
 253                         if (p->break_handler && p->break_handler(p, regs)) {
 254                                 goto ss_probe;
 255                         }
 256                 }
 257                 goto no_kprobe;
 258         }
 259
 260         p = get_kprobe(addr);
 261         if (!p) {
 262                 /* Not one of ours: let kernel handle it */
 263                 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
 264                         /*
 265                          * The breakpoint instruction was removed right
 266                          * after we hit it. Another cpu has removed
 267                          * either a probepoint or a debugger breakpoint
 268                          * at this address. In either case, no further
 269                          * handling of this interrupt is appropriate.
 270                          */
 271                         ret = 1;
 272                 }
 273
 274                 goto no_kprobe;
 275         }
 276
 277         set_current_kprobe(p, regs, kcb);
 278         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 279
 280         if (p->pre_handler && p->pre_handler(p, regs))
 281                 /* handler has already set things up, so skip ss setup */
 282                 return 1;
 283
 284 ss_probe:
 285         prepare_singlestep(p, regs);
 286         kcb->kprobe_status = KPROBE_HIT_SS;
 287         return 1;
 288
 289 no_kprobe:
 290         preempt_enable_no_resched();
 291         return ret;
 292 }
 293
 294 /*
 295  * For function-return probes, init_kprobes() establishes a probepoint
 296  * here. When a retprobed function returns, this probe is hit and
 297  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 298  */
 299 static void __used kretprobe_trampoline_holder(void)
 300 {
 301         asm volatile (".globl kretprobe_trampoline\n"
 302                       "kretprobe_trampoline:\n\t"
 303                       "nop\n");
 304 }
 305
 306 /*
 307  * Called when we hit the probe point at kretprobe_trampoline
 308  */
 309 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 310 {
 311         struct kretprobe_instance *ri = NULL;
 312         struct hlist_head *head, empty_rp;
 313         struct hlist_node *node, *tmp;
 314         unsigned long flags, orig_ret_address = 0;
 315         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 316
 317         INIT_HLIST_HEAD(&empty_rp);
 318         kretprobe_hash_lock(current, &head, &flags);
 319
 320         /*
 321          * It is possible to have multiple instances associated with a given
 322          * task either because an multiple functions in the call path
 323          * have a return probe installed on them, and/or more then one return
 324          * return probe was registered for a target function.
 325          *
 326          * We can handle this because:
 327          *     - instances are always inserted at the head of the list
 328          *     - when multiple return probes are registered for the same
 329          *       function, the first instance's ret_addr will point to the
 330          *       real return address, and all the rest will point to
 331          *       kretprobe_trampoline
 332          */
 333         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 334                 if (ri->task != current)
 335                         /* another task is sharing our hash bucket */
 336                         continue;
 337
 338                 if (ri->rp && ri->rp->handler) {
 339                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 340                         ri->rp->handler(ri, regs);
 341                         __get_cpu_var(current_kprobe) = NULL;
 342                 }
 343
 344                 orig_ret_address = (unsigned long)ri->ret_addr;
 345                 recycle_rp_inst(ri, &empty_rp);
 346
 347                 if (orig_ret_address != trampoline_address)
 348                         /*
 349                          * This is the real return address. Any other
 350                          * instances associated with this task are for
 351                          * other calls deeper on the call stack
 352                          */
 353                         break;
 354         }
 355
 356         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 357
 358         regs->pc = orig_ret_address;
 359         kretprobe_hash_unlock(current, &flags);
 360
 361         preempt_enable_no_resched();
 362
 363         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 364                 hlist_del(&ri->hlist);
 365                 kfree(ri);
 366         }
 367
 368         return orig_ret_address;
 369 }
 370
 371 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 372 {
 373         struct kprobe *cur = kprobe_running();
 374         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 375         kprobe_opcode_t *addr = NULL;
 376         struct kprobe *p = NULL;
 377
 378         if (!cur)
 379                 return 0;
 380
 381         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 382                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 383                 cur->post_handler(cur, regs, 0);
 384         }
 385
 386         p = &__get_cpu_var(saved_next_opcode);
 387         if (p->addr) {
 388                 arch_disarm_kprobe(p);
 389                 p->addr = NULL;
 390                 p->opcode = 0;
 391
 392                 addr = __get_cpu_var(saved_current_opcode).addr;
 393                 __get_cpu_var(saved_current_opcode).addr = NULL;
 394
 395                 p = get_kprobe(addr);
 396                 arch_arm_kprobe(p);
 397
 398                 p = &__get_cpu_var(saved_next_opcode2);
 399                 if (p->addr) {
 400                         arch_disarm_kprobe(p);
 401                         p->addr = NULL;
 402                         p->opcode = 0;
 403                 }
 404         }
 405
 406         /* Restore back the original saved kprobes variables and continue. */
 407         if (kcb->kprobe_status == KPROBE_REENTER) {
 408                 restore_previous_kprobe(kcb);
 409                 goto out;
 410         }
 411
 412         reset_current_kprobe();
 413
 414 out:
 415         preempt_enable_no_resched();
 416
 417         return 1;
 418 }
 419
 420 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 421 {
 422         struct kprobe *cur = kprobe_running();
 423         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 424         const struct exception_table_entry *entry;
 425
 426         switch (kcb->kprobe_status) {
 427         case KPROBE_HIT_SS:
 428         case KPROBE_REENTER:
 429                 /*
 430                  * We are here because the instruction being single
 431                  * stepped caused a page fault. We reset the current
 432                  * kprobe, point the pc back to the probe address
 433                  * and allow the page fault handler to continue as a
 434                  * normal page fault.
 435                  */
 436                 regs->pc = (unsigned long)cur->addr;
 437                 if (kcb->kprobe_status == KPROBE_REENTER)
 438                         restore_previous_kprobe(kcb);
 439                 else
 440                         reset_current_kprobe();
 441                 preempt_enable_no_resched();
 442                 break;
 443         case KPROBE_HIT_ACTIVE:
 444         case KPROBE_HIT_SSDONE:
 445                 /*
 446                  * We increment the nmissed count for accounting,
 447                  * we can also use npre/npostfault count for accounting
 448                  * these specific fault cases.
 449                  */
 450                 kprobes_inc_nmissed_count(cur);
 451
 452                 /*
 453                  * We come here because instructions in the pre/post
 454                  * handler caused the page_fault, this could happen
 455                  * if handler tries to access user space by
 456                  * copy_from_user(), get_user() etc. Let the
 457                  * user-specified handler try to fix it first.
 458                  */
 459                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 460                         return 1;
 461
 462                 /*
 463                  * In case the user-specified fault handler returned
 464                  * zero, try to fix up.
 465                  */
 466                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 467                         regs->pc = entry->fixup;
 468                         return 1;
 469                 }
 470
 471                 /*
 472                  * fixup_exception() could not handle it,
 473                  * Let do_page_fault() fix it.
 474                  */
 475                 break;
 476         default:
 477                 break;
 478         }
 479
 480         return 0;
 481 }
 482
 483 /*
 484  * Wrapper routine to for handling exceptions.
 485  */
 486 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 487                                        unsigned long val, void *data)
 488 {
 489         struct kprobe *p = NULL;
 490         struct die_args *args = (struct die_args *)data;
 491         int ret = NOTIFY_DONE;
 492         kprobe_opcode_t *addr = NULL;
 493         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 494
 495         addr = (kprobe_opcode_t *) (args->regs->pc);
 496         if (val == DIE_TRAP) {
 497                 if (!kprobe_running()) {
 498                         if (kprobe_handler(args->regs)) {
 499                                 ret = NOTIFY_STOP;
 500                         } else {
 501                                 /* Not a kprobe trap */
 502                                 ret = NOTIFY_DONE;
 503                         }
 504                 } else {
 505                         p = get_kprobe(addr);
 506                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 507                             (kcb->kprobe_status == KPROBE_REENTER)) {
 508                                 if (post_kprobe_handler(args->regs))
 509                                         ret = NOTIFY_STOP;
 510                         } else {
 511                                 if (kprobe_handler(args->regs)) {
 512                                         ret = NOTIFY_STOP;
 513                                 } else {
 514                                         p = __get_cpu_var(current_kprobe);
 515                                         if (p->break_handler &&
 516                                             p->break_handler(p, args->regs))
 517                                                 ret = NOTIFY_STOP;
 518                                 }
 519                         }
 520                 }
 521         }
 522
 523         return ret;
 524 }
 525
 526 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 527 {
 528         struct jprobe *jp = container_of(p, struct jprobe, kp);
 529         unsigned long addr;
 530         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 531
 532         kcb->jprobe_saved_regs = *regs;
 533         kcb->jprobe_saved_r15 = regs->regs[15];
 534         addr = kcb->jprobe_saved_r15;
 535
 536         /*
 537          * TBD: As Linus pointed out, gcc assumes that the callee
 538          * owns the argument space and could overwrite it, e.g.
 539          * tailcall optimization. So, to be absolutely safe
 540          * we also save and restore enough stack bytes to cover
 541          * the argument area.
 542          */
 543         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 544                MIN_STACK_SIZE(addr));
 545
 546         regs->pc = (unsigned long)(jp->entry);
 547
 548         return 1;
 549 }
 550
 551 void __kprobes jprobe_return(void)
 552 {
 553         asm volatile ("trapa #0x3a\n\t" "jprobe_return_end:\n\t" "nop\n\t");
 554 }
 555
 556 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 557 {
 558         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 559         unsigned long stack_addr = kcb->jprobe_saved_r15;
 560         u8 *addr = (u8 *)regs->pc;
 561
 562         if ((addr >= (u8 *)jprobe_return) &&
 563             (addr <= (u8 *)jprobe_return_end)) {
 564                 *regs = kcb->jprobe_saved_regs;
 565
 566                 memcpy((kprobe_opcode_t *)stack_addr, kcb->jprobes_stack,
 567                        MIN_STACK_SIZE(stack_addr));
 568
 569                 kcb->kprobe_status = KPROBE_HIT_SS;
 570                 preempt_enable_no_resched();
 571                 return 1;
 572         }
 573
 574         return 0;
 575 }
 576
 577 static struct kprobe trampoline_p = {
 578         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
 579         .pre_handler = trampoline_probe_handler
 580 };
 581
 582 int __init arch_init_kprobes(void)
 583 {
 584         return register_kprobe(&trampoline_p);
 585 }