arch/sh/kernel/kprobes.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Kernel probes (kprobes) for SuperH
   4  *
   5  * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
   6  * Copyright (C) 2006 Lineo Solutions, Inc.
   7  */
   8 #include <linux/kprobes.h>
   9 #include <linux/extable.h>
  10 #include <linux/ptrace.h>
  11 #include <linux/preempt.h>
  12 #include <linux/kdebug.h>
  13 #include <linux/slab.h>
  14 #include <asm/cacheflush.h>
  15 #include <linux/uaccess.h>
  16
  17 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  18 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  19
  20 static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
  21 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
  22 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);
  23
  24 #define OPCODE_JMP(x)   (((x) & 0xF0FF) == 0x402b)
  25 #define OPCODE_JSR(x)   (((x) & 0xF0FF) == 0x400b)
  26 #define OPCODE_BRA(x)   (((x) & 0xF000) == 0xa000)
  27 #define OPCODE_BRAF(x)  (((x) & 0xF0FF) == 0x0023)
  28 #define OPCODE_BSR(x)   (((x) & 0xF000) == 0xb000)
  29 #define OPCODE_BSRF(x)  (((x) & 0xF0FF) == 0x0003)
  30
  31 #define OPCODE_BF_S(x)  (((x) & 0xFF00) == 0x8f00)
  32 #define OPCODE_BT_S(x)  (((x) & 0xFF00) == 0x8d00)
  33
  34 #define OPCODE_BF(x)    (((x) & 0xFF00) == 0x8b00)
  35 #define OPCODE_BT(x)    (((x) & 0xFF00) == 0x8900)
  36
  37 #define OPCODE_RTS(x)   (((x) & 0x000F) == 0x000b)
  38 #define OPCODE_RTE(x)   (((x) & 0xFFFF) == 0x002b)
  39
  40 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  41 {
  42         kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
  43
  44         if (OPCODE_RTE(opcode))
  45                 return -EFAULT; /* Bad breakpoint */
  46
  47         p->opcode = opcode;
  48
  49         return 0;
  50 }
  51
  52 void __kprobes arch_copy_kprobe(struct kprobe *p)
  53 {
  54         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  55         p->opcode = *p->addr;
  56 }
  57
  58 void __kprobes arch_arm_kprobe(struct kprobe *p)
  59 {
  60         *p->addr = BREAKPOINT_INSTRUCTION;
  61         flush_icache_range((unsigned long)p->addr,
  62                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  63 }
  64
  65 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  66 {
  67         *p->addr = p->opcode;
  68         flush_icache_range((unsigned long)p->addr,
  69                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  70 }
  71
  72 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
  73 {
  74         if (*p->addr == BREAKPOINT_INSTRUCTION)
  75                 return 1;
  76
  77         return 0;
  78 }
  79
  80 /**
  81  * If an illegal slot instruction exception occurs for an address
  82  * containing a kprobe, remove the probe.
  83  *
  84  * Returns 0 if the exception was handled successfully, 1 otherwise.
  85  */
  86 int __kprobes kprobe_handle_illslot(unsigned long pc)
  87 {
  88         struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
  89
  90         if (p != NULL) {
  91                 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
  92                        (unsigned int)pc + 2);
  93                 unregister_kprobe(p);
  94                 return 0;
  95         }
  96
  97         return 1;
  98 }
  99
 100 void __kprobes arch_remove_kprobe(struct kprobe *p)
 101 {
 102         struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);
 103
 104         if (saved->addr) {
 105                 arch_disarm_kprobe(p);
 106                 arch_disarm_kprobe(saved);
 107
 108                 saved->addr = NULL;
 109                 saved->opcode = 0;
 110
 111                 saved = this_cpu_ptr(&saved_next_opcode2);
 112                 if (saved->addr) {
 113                         arch_disarm_kprobe(saved);
 114
 115                         saved->addr = NULL;
 116                         saved->opcode = 0;
 117                 }
 118         }
 119 }
 120
 121 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 122 {
 123         kcb->prev_kprobe.kp = kprobe_running();
 124         kcb->prev_kprobe.status = kcb->kprobe_status;
 125 }
 126
 127 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 128 {
 129         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 130         kcb->kprobe_status = kcb->prev_kprobe.status;
 131 }
 132
 133 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 134                                          struct kprobe_ctlblk *kcb)
 135 {
 136         __this_cpu_write(current_kprobe, p);
 137 }
 138
 139 /*
 140  * Singlestep is implemented by disabling the current kprobe and setting one
 141  * on the next instruction, following branches. Two probes are set if the
 142  * branch is conditional.
 143  */
 144 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 145 {
 146         __this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);
 147
 148         if (p != NULL) {
 149                 struct kprobe *op1, *op2;
 150
 151                 arch_disarm_kprobe(p);
 152
 153                 op1 = this_cpu_ptr(&saved_next_opcode);
 154                 op2 = this_cpu_ptr(&saved_next_opcode2);
 155
 156                 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
 157                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 158                         op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
 159                 } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
 160                         unsigned long disp = (p->opcode & 0x0FFF);
 161                         op1->addr =
 162                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 163
 164                 } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
 165                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 166                         op1->addr =
 167                             (kprobe_opcode_t *) (regs->pc + 4 +
 168                                                  regs->regs[reg_nr]);
 169
 170                 } else if (OPCODE_RTS(p->opcode)) {
 171                         op1->addr = (kprobe_opcode_t *) regs->pr;
 172
 173                 } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
 174                         unsigned long disp = (p->opcode & 0x00FF);
 175                         /* case 1 */
 176                         op1->addr = p->addr + 1;
 177                         /* case 2 */
 178                         op2->addr =
 179                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 180                         op2->opcode = *(op2->addr);
 181                         arch_arm_kprobe(op2);
 182
 183                 } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
 184                         unsigned long disp = (p->opcode & 0x00FF);
 185                         /* case 1 */
 186                         op1->addr = p->addr + 2;
 187                         /* case 2 */
 188                         op2->addr =
 189                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 190                         op2->opcode = *(op2->addr);
 191                         arch_arm_kprobe(op2);
 192
 193                 } else {
 194                         op1->addr = p->addr + 1;
 195                 }
 196
 197                 op1->opcode = *(op1->addr);
 198                 arch_arm_kprobe(op1);
 199         }
 200 }
 201
 202 /* Called with kretprobe_lock held */
 203 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 204                                       struct pt_regs *regs)
 205 {
 206         ri->ret_addr = (kprobe_opcode_t *) regs->pr;
 207
 208         /* Replace the return addr with trampoline addr */
 209         regs->pr = (unsigned long)kretprobe_trampoline;
 210 }
 211
 212 static int __kprobes kprobe_handler(struct pt_regs *regs)
 213 {
 214         struct kprobe *p;
 215         int ret = 0;
 216         kprobe_opcode_t *addr = NULL;
 217         struct kprobe_ctlblk *kcb;
 218
 219         /*
 220          * We don't want to be preempted for the entire
 221          * duration of kprobe processing
 222          */
 223         preempt_disable();
 224         kcb = get_kprobe_ctlblk();
 225
 226         addr = (kprobe_opcode_t *) (regs->pc);
 227
 228         /* Check we're not actually recursing */
 229         if (kprobe_running()) {
 230                 p = get_kprobe(addr);
 231                 if (p) {
 232                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 233                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 234                                 goto no_kprobe;
 235                         }
 236                         /* We have reentered the kprobe_handler(), since
 237                          * another probe was hit while within the handler.
 238                          * We here save the original kprobes variables and
 239                          * just single step on the instruction of the new probe
 240                          * without calling any user handlers.
 241                          */
 242                         save_previous_kprobe(kcb);
 243                         set_current_kprobe(p, regs, kcb);
 244                         kprobes_inc_nmissed_count(p);
 245                         prepare_singlestep(p, regs);
 246                         kcb->kprobe_status = KPROBE_REENTER;
 247                         return 1;
 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                 reset_current_kprobe();
 275                 preempt_enable_no_resched();
 276                 return 1;
 277         }
 278
 279         prepare_singlestep(p, regs);
 280         kcb->kprobe_status = KPROBE_HIT_SS;
 281         return 1;
 282
 283 no_kprobe:
 284         preempt_enable_no_resched();
 285         return ret;
 286 }
 287
 288 /*
 289  * For function-return probes, init_kprobes() establishes a probepoint
 290  * here. When a retprobed function returns, this probe is hit and
 291  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 292  */
 293 static void __used kretprobe_trampoline_holder(void)
 294 {
 295         asm volatile (".globl kretprobe_trampoline\n"
 296                       "kretprobe_trampoline:\n\t"
 297                       "nop\n");
 298 }
 299
 300 /*
 301  * Called when we hit the probe point at kretprobe_trampoline
 302  */
 303 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 304 {
 305         struct kretprobe_instance *ri = NULL;
 306         struct hlist_head *head, empty_rp;
 307         struct hlist_node *tmp;
 308         unsigned long flags, orig_ret_address = 0;
 309         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 310
 311         INIT_HLIST_HEAD(&empty_rp);
 312         kretprobe_hash_lock(current, &head, &flags);
 313
 314         /*
 315          * It is possible to have multiple instances associated with a given
 316          * task either because an multiple functions in the call path
 317          * have a return probe installed on them, and/or more then one return
 318          * return probe was registered for a target function.
 319          *
 320          * We can handle this because:
 321          *     - instances are always inserted at the head of the list
 322          *     - when multiple return probes are registered for the same
 323          *       function, the first instance's ret_addr will point to the
 324          *       real return address, and all the rest will point to
 325          *       kretprobe_trampoline
 326          */
 327         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 328                 if (ri->task != current)
 329                         /* another task is sharing our hash bucket */
 330                         continue;
 331
 332                 if (ri->rp && ri->rp->handler) {
 333                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 334                         ri->rp->handler(ri, regs);
 335                         __this_cpu_write(current_kprobe, NULL);
 336                 }
 337
 338                 orig_ret_address = (unsigned long)ri->ret_addr;
 339                 recycle_rp_inst(ri, &empty_rp);
 340
 341                 if (orig_ret_address != trampoline_address)
 342                         /*
 343                          * This is the real return address. Any other
 344                          * instances associated with this task are for
 345                          * other calls deeper on the call stack
 346                          */
 347                         break;
 348         }
 349
 350         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 351
 352         regs->pc = orig_ret_address;
 353         kretprobe_hash_unlock(current, &flags);
 354
 355         hlist_for_each_entry_safe(ri, 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         p = this_cpu_ptr(&saved_next_opcode);
 379         if (p->addr) {
 380                 arch_disarm_kprobe(p);
 381                 p->addr = NULL;
 382                 p->opcode = 0;
 383
 384                 addr = __this_cpu_read(saved_current_opcode.addr);
 385                 __this_cpu_write(saved_current_opcode.addr, NULL);
 386
 387                 p = get_kprobe(addr);
 388                 arch_arm_kprobe(p);
 389
 390                 p = this_cpu_ptr(&saved_next_opcode2);
 391                 if (p->addr) {
 392                         arch_disarm_kprobe(p);
 393                         p->addr = NULL;
 394                         p->opcode = 0;
 395                 }
 396         }
 397
 398         /* Restore back the original saved kprobes variables and continue. */
 399         if (kcb->kprobe_status == KPROBE_REENTER) {
 400                 restore_previous_kprobe(kcb);
 401                 goto out;
 402         }
 403
 404         reset_current_kprobe();
 405
 406 out:
 407         preempt_enable_no_resched();
 408
 409         return 1;
 410 }
 411
 412 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 413 {
 414         struct kprobe *cur = kprobe_running();
 415         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 416         const struct exception_table_entry *entry;
 417
 418         switch (kcb->kprobe_status) {
 419         case KPROBE_HIT_SS:
 420         case KPROBE_REENTER:
 421                 /*
 422                  * We are here because the instruction being single
 423                  * stepped caused a page fault. We reset the current
 424                  * kprobe, point the pc back to the probe address
 425                  * and allow the page fault handler to continue as a
 426                  * normal page fault.
 427                  */
 428                 regs->pc = (unsigned long)cur->addr;
 429                 if (kcb->kprobe_status == KPROBE_REENTER)
 430                         restore_previous_kprobe(kcb);
 431                 else
 432                         reset_current_kprobe();
 433                 preempt_enable_no_resched();
 434                 break;
 435         case KPROBE_HIT_ACTIVE:
 436         case KPROBE_HIT_SSDONE:
 437                 /*
 438                  * We increment the nmissed count for accounting,
 439                  * we can also use npre/npostfault count for accounting
 440                  * these specific fault cases.
 441                  */
 442                 kprobes_inc_nmissed_count(cur);
 443
 444                 /*
 445                  * We come here because instructions in the pre/post
 446                  * handler caused the page_fault, this could happen
 447                  * if handler tries to access user space by
 448                  * copy_from_user(), get_user() etc. Let the
 449                  * user-specified handler try to fix it first.
 450                  */
 451                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 452                         return 1;
 453
 454                 /*
 455                  * In case the user-specified fault handler returned
 456                  * zero, try to fix up.
 457                  */
 458                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 459                         regs->pc = entry->fixup;
 460                         return 1;
 461                 }
 462
 463                 /*
 464                  * fixup_exception() could not handle it,
 465                  * Let do_page_fault() fix it.
 466                  */
 467                 break;
 468         default:
 469                 break;
 470         }
 471
 472         return 0;
 473 }
 474
 475 /*
 476  * Wrapper routine to for handling exceptions.
 477  */
 478 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 479                                        unsigned long val, void *data)
 480 {
 481         struct kprobe *p = NULL;
 482         struct die_args *args = (struct die_args *)data;
 483         int ret = NOTIFY_DONE;
 484         kprobe_opcode_t *addr = NULL;
 485         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 486
 487         addr = (kprobe_opcode_t *) (args->regs->pc);
 488         if (val == DIE_TRAP) {
 489                 if (!kprobe_running()) {
 490                         if (kprobe_handler(args->regs)) {
 491                                 ret = NOTIFY_STOP;
 492                         } else {
 493                                 /* Not a kprobe trap */
 494                                 ret = NOTIFY_DONE;
 495                         }
 496                 } else {
 497                         p = get_kprobe(addr);
 498                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 499                             (kcb->kprobe_status == KPROBE_REENTER)) {
 500                                 if (post_kprobe_handler(args->regs))
 501                                         ret = NOTIFY_STOP;
 502                         } else {
 503                                 if (kprobe_handler(args->regs))
 504                                         ret = NOTIFY_STOP;
 505                         }
 506                 }
 507         }
 508
 509         return ret;
 510 }
 511
 512 static struct kprobe trampoline_p = {
 513         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
 514         .pre_handler = trampoline_probe_handler
 515 };
 516
 517 int __init arch_init_kprobes(void)
 518 {
 519         return register_kprobe(&trampoline_p);
 520 }