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/extable.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 <linux/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 = this_cpu_ptr(&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 = this_cpu_ptr(&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         __this_cpu_write(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         __this_cpu_write(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         __this_cpu_write(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 = this_cpu_ptr(&saved_next_opcode);
 157                 op2 = this_cpu_ptr(&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                 }
 252                 goto no_kprobe;
 253         }
 254
 255         p = get_kprobe(addr);
 256         if (!p) {
 257                 /* Not one of ours: let kernel handle it */
 258                 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
 259                         /*
 260                          * The breakpoint instruction was removed right
 261                          * after we hit it. Another cpu has removed
 262                          * either a probepoint or a debugger breakpoint
 263                          * at this address. In either case, no further
 264                          * handling of this interrupt is appropriate.
 265                          */
 266                         ret = 1;
 267                 }
 268
 269                 goto no_kprobe;
 270         }
 271
 272         set_current_kprobe(p, regs, kcb);
 273         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 274
 275         if (p->pre_handler && p->pre_handler(p, regs)) {
 276                 /* handler has already set things up, so skip ss setup */
 277                 reset_current_kprobe();
 278                 preempt_enable_no_resched();
 279                 return 1;
 280         }
 281
 282         prepare_singlestep(p, regs);
 283         kcb->kprobe_status = KPROBE_HIT_SS;
 284         return 1;
 285
 286 no_kprobe:
 287         preempt_enable_no_resched();
 288         return ret;
 289 }
 290
 291 /*
 292  * For function-return probes, init_kprobes() establishes a probepoint
 293  * here. When a retprobed function returns, this probe is hit and
 294  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 295  */
 296 static void __used kretprobe_trampoline_holder(void)
 297 {
 298         asm volatile (".globl kretprobe_trampoline\n"
 299                       "kretprobe_trampoline:\n\t"
 300                       "nop\n");
 301 }
 302
 303 /*
 304  * Called when we hit the probe point at kretprobe_trampoline
 305  */
 306 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 307 {
 308         struct kretprobe_instance *ri = NULL;
 309         struct hlist_head *head, empty_rp;
 310         struct hlist_node *tmp;
 311         unsigned long flags, orig_ret_address = 0;
 312         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 313
 314         INIT_HLIST_HEAD(&empty_rp);
 315         kretprobe_hash_lock(current, &head, &flags);
 316
 317         /*
 318          * It is possible to have multiple instances associated with a given
 319          * task either because an multiple functions in the call path
 320          * have a return probe installed on them, and/or more then one return
 321          * return probe was registered for a target function.
 322          *
 323          * We can handle this because:
 324          *     - instances are always inserted at the head of the list
 325          *     - when multiple return probes are registered for the same
 326          *       function, the first instance's ret_addr will point to the
 327          *       real return address, and all the rest will point to
 328          *       kretprobe_trampoline
 329          */
 330         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 331                 if (ri->task != current)
 332                         /* another task is sharing our hash bucket */
 333                         continue;
 334
 335                 if (ri->rp && ri->rp->handler) {
 336                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 337                         ri->rp->handler(ri, regs);
 338                         __this_cpu_write(current_kprobe, NULL);
 339                 }
 340
 341                 orig_ret_address = (unsigned long)ri->ret_addr;
 342                 recycle_rp_inst(ri, &empty_rp);
 343
 344                 if (orig_ret_address != trampoline_address)
 345                         /*
 346                          * This is the real return address. Any other
 347                          * instances associated with this task are for
 348                          * other calls deeper on the call stack
 349                          */
 350                         break;
 351         }
 352
 353         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 354
 355         regs->pc = orig_ret_address;
 356         kretprobe_hash_unlock(current, &flags);
 357
 358         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 359                 hlist_del(&ri->hlist);
 360                 kfree(ri);
 361         }
 362
 363         return orig_ret_address;
 364 }
 365
 366 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 367 {
 368         struct kprobe *cur = kprobe_running();
 369         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 370         kprobe_opcode_t *addr = NULL;
 371         struct kprobe *p = NULL;
 372
 373         if (!cur)
 374                 return 0;
 375
 376         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 377                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 378                 cur->post_handler(cur, regs, 0);
 379         }
 380
 381         p = this_cpu_ptr(&saved_next_opcode);
 382         if (p->addr) {
 383                 arch_disarm_kprobe(p);
 384                 p->addr = NULL;
 385                 p->opcode = 0;
 386
 387                 addr = __this_cpu_read(saved_current_opcode.addr);
 388                 __this_cpu_write(saved_current_opcode.addr, NULL);
 389
 390                 p = get_kprobe(addr);
 391                 arch_arm_kprobe(p);
 392
 393                 p = this_cpu_ptr(&saved_next_opcode2);
 394                 if (p->addr) {
 395                         arch_disarm_kprobe(p);
 396                         p->addr = NULL;
 397                         p->opcode = 0;
 398                 }
 399         }
 400
 401         /* Restore back the original saved kprobes variables and continue. */
 402         if (kcb->kprobe_status == KPROBE_REENTER) {
 403                 restore_previous_kprobe(kcb);
 404                 goto out;
 405         }
 406
 407         reset_current_kprobe();
 408
 409 out:
 410         preempt_enable_no_resched();
 411
 412         return 1;
 413 }
 414
 415 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 416 {
 417         struct kprobe *cur = kprobe_running();
 418         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 419         const struct exception_table_entry *entry;
 420
 421         switch (kcb->kprobe_status) {
 422         case KPROBE_HIT_SS:
 423         case KPROBE_REENTER:
 424                 /*
 425                  * We are here because the instruction being single
 426                  * stepped caused a page fault. We reset the current
 427                  * kprobe, point the pc back to the probe address
 428                  * and allow the page fault handler to continue as a
 429                  * normal page fault.
 430                  */
 431                 regs->pc = (unsigned long)cur->addr;
 432                 if (kcb->kprobe_status == KPROBE_REENTER)
 433                         restore_previous_kprobe(kcb);
 434                 else
 435                         reset_current_kprobe();
 436                 preempt_enable_no_resched();
 437                 break;
 438         case KPROBE_HIT_ACTIVE:
 439         case KPROBE_HIT_SSDONE:
 440                 /*
 441                  * We increment the nmissed count for accounting,
 442                  * we can also use npre/npostfault count for accounting
 443                  * these specific fault cases.
 444                  */
 445                 kprobes_inc_nmissed_count(cur);
 446
 447                 /*
 448                  * We come here because instructions in the pre/post
 449                  * handler caused the page_fault, this could happen
 450                  * if handler tries to access user space by
 451                  * copy_from_user(), get_user() etc. Let the
 452                  * user-specified handler try to fix it first.
 453                  */
 454                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 455                         return 1;
 456
 457                 /*
 458                  * In case the user-specified fault handler returned
 459                  * zero, try to fix up.
 460                  */
 461                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 462                         regs->pc = entry->fixup;
 463                         return 1;
 464                 }
 465
 466                 /*
 467                  * fixup_exception() could not handle it,
 468                  * Let do_page_fault() fix it.
 469                  */
 470                 break;
 471         default:
 472                 break;
 473         }
 474
 475         return 0;
 476 }
 477
 478 /*
 479  * Wrapper routine to for handling exceptions.
 480  */
 481 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 482                                        unsigned long val, void *data)
 483 {
 484         struct kprobe *p = NULL;
 485         struct die_args *args = (struct die_args *)data;
 486         int ret = NOTIFY_DONE;
 487         kprobe_opcode_t *addr = NULL;
 488         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 489
 490         addr = (kprobe_opcode_t *) (args->regs->pc);
 491         if (val == DIE_TRAP) {
 492                 if (!kprobe_running()) {
 493                         if (kprobe_handler(args->regs)) {
 494                                 ret = NOTIFY_STOP;
 495                         } else {
 496                                 /* Not a kprobe trap */
 497                                 ret = NOTIFY_DONE;
 498                         }
 499                 } else {
 500                         p = get_kprobe(addr);
 501                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 502                             (kcb->kprobe_status == KPROBE_REENTER)) {
 503                                 if (post_kprobe_handler(args->regs))
 504                                         ret = NOTIFY_STOP;
 505                         } else {
 506                                 if (kprobe_handler(args->regs))
 507                                         ret = NOTIFY_STOP;
 508                         }
 509                 }
 510         }
 511
 512         return ret;
 513 }
 514
 515 static struct kprobe trampoline_p = {
 516         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
 517         .pre_handler = trampoline_probe_handler
 518 };
 519
 520 int __init arch_init_kprobes(void)
 521 {
 522         return register_kprobe(&trampoline_p);
 523 }