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         ri->fp = NULL;
 208
 209         /* Replace the return addr with trampoline addr */
 210         regs->pr = (unsigned long)kretprobe_trampoline;
 211 }
 212
 213 static int __kprobes kprobe_handler(struct pt_regs *regs)
 214 {
 215         struct kprobe *p;
 216         int ret = 0;
 217         kprobe_opcode_t *addr = NULL;
 218         struct kprobe_ctlblk *kcb;
 219
 220         /*
 221          * We don't want to be preempted for the entire
 222          * duration of kprobe processing
 223          */
 224         preempt_disable();
 225         kcb = get_kprobe_ctlblk();
 226
 227         addr = (kprobe_opcode_t *) (regs->pc);
 228
 229         /* Check we're not actually recursing */
 230         if (kprobe_running()) {
 231                 p = get_kprobe(addr);
 232                 if (p) {
 233                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 234                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 235                                 goto no_kprobe;
 236                         }
 237                         /* We have reentered the kprobe_handler(), since
 238                          * another probe was hit while within the handler.
 239                          * We here save the original kprobes variables and
 240                          * just single step on the instruction of the new probe
 241                          * without calling any user handlers.
 242                          */
 243                         save_previous_kprobe(kcb);
 244                         set_current_kprobe(p, regs, kcb);
 245                         kprobes_inc_nmissed_count(p);
 246                         prepare_singlestep(p, regs);
 247                         kcb->kprobe_status = KPROBE_REENTER;
 248                         return 1;
 249                 }
 250                 goto no_kprobe;
 251         }
 252
 253         p = get_kprobe(addr);
 254         if (!p) {
 255                 /* Not one of ours: let kernel handle it */
 256                 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
 257                         /*
 258                          * The breakpoint instruction was removed right
 259                          * after we hit it. Another cpu has removed
 260                          * either a probepoint or a debugger breakpoint
 261                          * at this address. In either case, no further
 262                          * handling of this interrupt is appropriate.
 263                          */
 264                         ret = 1;
 265                 }
 266
 267                 goto no_kprobe;
 268         }
 269
 270         set_current_kprobe(p, regs, kcb);
 271         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 272
 273         if (p->pre_handler && p->pre_handler(p, regs)) {
 274                 /* handler has already set things up, so skip ss setup */
 275                 reset_current_kprobe();
 276                 preempt_enable_no_resched();
 277                 return 1;
 278         }
 279
 280         prepare_singlestep(p, regs);
 281         kcb->kprobe_status = KPROBE_HIT_SS;
 282         return 1;
 283
 284 no_kprobe:
 285         preempt_enable_no_resched();
 286         return ret;
 287 }
 288
 289 /*
 290  * For function-return probes, init_kprobes() establishes a probepoint
 291  * here. When a retprobed function returns, this probe is hit and
 292  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 293  */
 294 static void __used kretprobe_trampoline_holder(void)
 295 {
 296         asm volatile (".globl kretprobe_trampoline\n"
 297                       "kretprobe_trampoline:\n\t"
 298                       "nop\n");
 299 }
 300
 301 /*
 302  * Called when we hit the probe point at kretprobe_trampoline
 303  */
 304 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 305 {
 306         regs->pc = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
 307
 308         return 1;
 309 }
 310
 311 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 312 {
 313         struct kprobe *cur = kprobe_running();
 314         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 315         kprobe_opcode_t *addr = NULL;
 316         struct kprobe *p = NULL;
 317
 318         if (!cur)
 319                 return 0;
 320
 321         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 322                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 323                 cur->post_handler(cur, regs, 0);
 324         }
 325
 326         p = this_cpu_ptr(&saved_next_opcode);
 327         if (p->addr) {
 328                 arch_disarm_kprobe(p);
 329                 p->addr = NULL;
 330                 p->opcode = 0;
 331
 332                 addr = __this_cpu_read(saved_current_opcode.addr);
 333                 __this_cpu_write(saved_current_opcode.addr, NULL);
 334
 335                 p = get_kprobe(addr);
 336                 arch_arm_kprobe(p);
 337
 338                 p = this_cpu_ptr(&saved_next_opcode2);
 339                 if (p->addr) {
 340                         arch_disarm_kprobe(p);
 341                         p->addr = NULL;
 342                         p->opcode = 0;
 343                 }
 344         }
 345
 346         /* Restore back the original saved kprobes variables and continue. */
 347         if (kcb->kprobe_status == KPROBE_REENTER) {
 348                 restore_previous_kprobe(kcb);
 349                 goto out;
 350         }
 351
 352         reset_current_kprobe();
 353
 354 out:
 355         preempt_enable_no_resched();
 356
 357         return 1;
 358 }
 359
 360 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 361 {
 362         struct kprobe *cur = kprobe_running();
 363         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 364         const struct exception_table_entry *entry;
 365
 366         switch (kcb->kprobe_status) {
 367         case KPROBE_HIT_SS:
 368         case KPROBE_REENTER:
 369                 /*
 370                  * We are here because the instruction being single
 371                  * stepped caused a page fault. We reset the current
 372                  * kprobe, point the pc back to the probe address
 373                  * and allow the page fault handler to continue as a
 374                  * normal page fault.
 375                  */
 376                 regs->pc = (unsigned long)cur->addr;
 377                 if (kcb->kprobe_status == KPROBE_REENTER)
 378                         restore_previous_kprobe(kcb);
 379                 else
 380                         reset_current_kprobe();
 381                 preempt_enable_no_resched();
 382                 break;
 383         case KPROBE_HIT_ACTIVE:
 384         case KPROBE_HIT_SSDONE:
 385                 /*
 386                  * We increment the nmissed count for accounting,
 387                  * we can also use npre/npostfault count for accounting
 388                  * these specific fault cases.
 389                  */
 390                 kprobes_inc_nmissed_count(cur);
 391
 392                 /*
 393                  * In case the user-specified fault handler returned
 394                  * zero, try to fix up.
 395                  */
 396                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 397                         regs->pc = entry->fixup;
 398                         return 1;
 399                 }
 400
 401                 /*
 402                  * fixup_exception() could not handle it,
 403                  * Let do_page_fault() fix it.
 404                  */
 405                 break;
 406         default:
 407                 break;
 408         }
 409
 410         return 0;
 411 }
 412
 413 /*
 414  * Wrapper routine to for handling exceptions.
 415  */
 416 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 417                                        unsigned long val, void *data)
 418 {
 419         struct kprobe *p = NULL;
 420         struct die_args *args = (struct die_args *)data;
 421         int ret = NOTIFY_DONE;
 422         kprobe_opcode_t *addr = NULL;
 423         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 424
 425         addr = (kprobe_opcode_t *) (args->regs->pc);
 426         if (val == DIE_TRAP &&
 427             args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
 428                 if (!kprobe_running()) {
 429                         if (kprobe_handler(args->regs)) {
 430                                 ret = NOTIFY_STOP;
 431                         } else {
 432                                 /* Not a kprobe trap */
 433                                 ret = NOTIFY_DONE;
 434                         }
 435                 } else {
 436                         p = get_kprobe(addr);
 437                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 438                             (kcb->kprobe_status == KPROBE_REENTER)) {
 439                                 if (post_kprobe_handler(args->regs))
 440                                         ret = NOTIFY_STOP;
 441                         } else {
 442                                 if (kprobe_handler(args->regs))
 443                                         ret = NOTIFY_STOP;
 444                         }
 445                 }
 446         }
 447
 448         return ret;
 449 }
 450
 451 static struct kprobe trampoline_p = {
 452         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
 453         .pre_handler = trampoline_probe_handler
 454 };
 455
 456 int __init arch_init_kprobes(void)
 457 {
 458         return register_kprobe(&trampoline_p);
 459 }