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 <[email protected]>
   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 = *p->addr;
  43
  44         if (OPCODE_RTE(opcode))
  45                 return -EFAULT; /* Bad breakpoint */
  46
  47         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  48         p->opcode = opcode;
  49
  50         return 0;
  51 }
  52
  53 void __kprobes arch_arm_kprobe(struct kprobe *p)
  54 {
  55         *p->addr = BREAKPOINT_INSTRUCTION;
  56         flush_icache_range((unsigned long)p->addr,
  57                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  58 }
  59
  60 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  61 {
  62         *p->addr = p->opcode;
  63         flush_icache_range((unsigned long)p->addr,
  64                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  65 }
  66
  67 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
  68 {
  69         if (*p->addr == BREAKPOINT_INSTRUCTION)
  70                 return 1;
  71
  72         return 0;
  73 }
  74
  75 /**
  76  * If an illegal slot instruction exception occurs for an address
  77  * containing a kprobe, remove the probe.
  78  *
  79  * Returns 0 if the exception was handled successfully, 1 otherwise.
  80  */
  81 int __kprobes kprobe_handle_illslot(unsigned long pc)
  82 {
  83         struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
  84
  85         if (p != NULL) {
  86                 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
  87                        (unsigned int)pc + 2);
  88                 unregister_kprobe(p);
  89                 return 0;
  90         }
  91
  92         return 1;
  93 }
  94
  95 void __kprobes arch_remove_kprobe(struct kprobe *p)
  96 {
  97         struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);
  98
  99         if (saved->addr) {
 100                 arch_disarm_kprobe(p);
 101                 arch_disarm_kprobe(saved);
 102
 103                 saved->addr = NULL;
 104                 saved->opcode = 0;
 105
 106                 saved = this_cpu_ptr(&saved_next_opcode2);
 107                 if (saved->addr) {
 108                         arch_disarm_kprobe(saved);
 109
 110                         saved->addr = NULL;
 111                         saved->opcode = 0;
 112                 }
 113         }
 114 }
 115
 116 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 117 {
 118         kcb->prev_kprobe.kp = kprobe_running();
 119         kcb->prev_kprobe.status = kcb->kprobe_status;
 120 }
 121
 122 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 123 {
 124         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 125         kcb->kprobe_status = kcb->prev_kprobe.status;
 126 }
 127
 128 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 129                                          struct kprobe_ctlblk *kcb)
 130 {
 131         __this_cpu_write(current_kprobe, p);
 132 }
 133
 134 /*
 135  * Singlestep is implemented by disabling the current kprobe and setting one
 136  * on the next instruction, following branches. Two probes are set if the
 137  * branch is conditional.
 138  */
 139 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 140 {
 141         __this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);
 142
 143         if (p != NULL) {
 144                 struct kprobe *op1, *op2;
 145
 146                 arch_disarm_kprobe(p);
 147
 148                 op1 = this_cpu_ptr(&saved_next_opcode);
 149                 op2 = this_cpu_ptr(&saved_next_opcode2);
 150
 151                 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
 152                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
 153                         op1->addr = (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                         op1->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                         op1->addr =
 162                             (kprobe_opcode_t *) (regs->pc + 4 +
 163                                                  regs->regs[reg_nr]);
 164
 165                 } else if (OPCODE_RTS(p->opcode)) {
 166                         op1->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                         op1->addr = p->addr + 1;
 172                         /* case 2 */
 173                         op2->addr =
 174                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 175                         op2->opcode = *(op2->addr);
 176                         arch_arm_kprobe(op2);
 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                         op1->addr = p->addr + 2;
 182                         /* case 2 */
 183                         op2->addr =
 184                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
 185                         op2->opcode = *(op2->addr);
 186                         arch_arm_kprobe(op2);
 187
 188                 } else {
 189                         op1->addr = p->addr + 1;
 190                 }
 191
 192                 op1->opcode = *(op1->addr);
 193                 arch_arm_kprobe(op1);
 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         ri->fp = NULL;
 203
 204         /* Replace the return addr with trampoline addr */
 205         regs->pr = (unsigned long)__kretprobe_trampoline;
 206 }
 207
 208 static int __kprobes kprobe_handler(struct pt_regs *regs)
 209 {
 210         struct kprobe *p;
 211         int ret = 0;
 212         kprobe_opcode_t *addr = NULL;
 213         struct kprobe_ctlblk *kcb;
 214
 215         /*
 216          * We don't want to be preempted for the entire
 217          * duration of kprobe processing
 218          */
 219         preempt_disable();
 220         kcb = get_kprobe_ctlblk();
 221
 222         addr = (kprobe_opcode_t *) (regs->pc);
 223
 224         /* Check we're not actually recursing */
 225         if (kprobe_running()) {
 226                 p = get_kprobe(addr);
 227                 if (p) {
 228                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 229                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 230                                 goto no_kprobe;
 231                         }
 232                         /* We have reentered the kprobe_handler(), since
 233                          * another probe was hit while within the handler.
 234                          * We here save the original kprobes variables and
 235                          * just single step on the instruction of the new probe
 236                          * without calling any user handlers.
 237                          */
 238                         save_previous_kprobe(kcb);
 239                         set_current_kprobe(p, regs, kcb);
 240                         kprobes_inc_nmissed_count(p);
 241                         prepare_singlestep(p, regs);
 242                         kcb->kprobe_status = KPROBE_REENTER;
 243                         return 1;
 244                 }
 245                 goto no_kprobe;
 246         }
 247
 248         p = get_kprobe(addr);
 249         if (!p) {
 250                 /* Not one of ours: let kernel handle it */
 251                 if (*addr != BREAKPOINT_INSTRUCTION) {
 252                         /*
 253                          * The breakpoint instruction was removed right
 254                          * after we hit it. Another cpu has removed
 255                          * either a probepoint or a debugger breakpoint
 256                          * at this address. In either case, no further
 257                          * handling of this interrupt is appropriate.
 258                          */
 259                         ret = 1;
 260                 }
 261
 262                 goto no_kprobe;
 263         }
 264
 265         set_current_kprobe(p, regs, kcb);
 266         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 267
 268         if (p->pre_handler && p->pre_handler(p, regs)) {
 269                 /* handler has already set things up, so skip ss setup */
 270                 reset_current_kprobe();
 271                 preempt_enable_no_resched();
 272                 return 1;
 273         }
 274
 275         prepare_singlestep(p, regs);
 276         kcb->kprobe_status = KPROBE_HIT_SS;
 277         return 1;
 278
 279 no_kprobe:
 280         preempt_enable_no_resched();
 281         return ret;
 282 }
 283
 284 /*
 285  * For function-return probes, init_kprobes() establishes a probepoint
 286  * here. When a retprobed function returns, this probe is hit and
 287  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 288  */
 289 static void __used kretprobe_trampoline_holder(void)
 290 {
 291         asm volatile (".globl __kretprobe_trampoline\n"
 292                       "__kretprobe_trampoline:\n\t"
 293                       "nop\n");
 294 }
 295
 296 /*
 297  * Called when we hit the probe point at __kretprobe_trampoline
 298  */
 299 static int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 300 {
 301         regs->pc = __kretprobe_trampoline_handler(regs, NULL);
 302
 303         return 1;
 304 }
 305
 306 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 307 {
 308         struct kprobe *cur = kprobe_running();
 309         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 310         kprobe_opcode_t *addr = NULL;
 311         struct kprobe *p = NULL;
 312
 313         if (!cur)
 314                 return 0;
 315
 316         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 317                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 318                 cur->post_handler(cur, regs, 0);
 319         }
 320
 321         p = this_cpu_ptr(&saved_next_opcode);
 322         if (p->addr) {
 323                 arch_disarm_kprobe(p);
 324                 p->addr = NULL;
 325                 p->opcode = 0;
 326
 327                 addr = __this_cpu_read(saved_current_opcode.addr);
 328                 __this_cpu_write(saved_current_opcode.addr, NULL);
 329
 330                 p = get_kprobe(addr);
 331                 arch_arm_kprobe(p);
 332
 333                 p = this_cpu_ptr(&saved_next_opcode2);
 334                 if (p->addr) {
 335                         arch_disarm_kprobe(p);
 336                         p->addr = NULL;
 337                         p->opcode = 0;
 338                 }
 339         }
 340
 341         /* Restore back the original saved kprobes variables and continue. */
 342         if (kcb->kprobe_status == KPROBE_REENTER) {
 343                 restore_previous_kprobe(kcb);
 344                 goto out;
 345         }
 346
 347         reset_current_kprobe();
 348
 349 out:
 350         preempt_enable_no_resched();
 351
 352         return 1;
 353 }
 354
 355 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 356 {
 357         struct kprobe *cur = kprobe_running();
 358         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 359         const struct exception_table_entry *entry;
 360
 361         switch (kcb->kprobe_status) {
 362         case KPROBE_HIT_SS:
 363         case KPROBE_REENTER:
 364                 /*
 365                  * We are here because the instruction being single
 366                  * stepped caused a page fault. We reset the current
 367                  * kprobe, point the pc back to the probe address
 368                  * and allow the page fault handler to continue as a
 369                  * normal page fault.
 370                  */
 371                 regs->pc = (unsigned long)cur->addr;
 372                 if (kcb->kprobe_status == KPROBE_REENTER)
 373                         restore_previous_kprobe(kcb);
 374                 else
 375                         reset_current_kprobe();
 376                 preempt_enable_no_resched();
 377                 break;
 378         case KPROBE_HIT_ACTIVE:
 379         case KPROBE_HIT_SSDONE:
 380                 /*
 381                  * In case the user-specified fault handler returned
 382                  * zero, try to fix up.
 383                  */
 384                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 385                         regs->pc = entry->fixup;
 386                         return 1;
 387                 }
 388
 389                 /*
 390                  * fixup_exception() could not handle it,
 391                  * Let do_page_fault() fix it.
 392                  */
 393                 break;
 394         default:
 395                 break;
 396         }
 397
 398         return 0;
 399 }
 400
 401 /*
 402  * Wrapper routine to for handling exceptions.
 403  */
 404 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 405                                        unsigned long val, void *data)
 406 {
 407         struct kprobe *p = NULL;
 408         struct die_args *args = (struct die_args *)data;
 409         int ret = NOTIFY_DONE;
 410         kprobe_opcode_t *addr = NULL;
 411         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 412
 413         addr = (kprobe_opcode_t *) (args->regs->pc);
 414         if (val == DIE_TRAP &&
 415             args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
 416                 if (!kprobe_running()) {
 417                         if (kprobe_handler(args->regs)) {
 418                                 ret = NOTIFY_STOP;
 419                         } else {
 420                                 /* Not a kprobe trap */
 421                                 ret = NOTIFY_DONE;
 422                         }
 423                 } else {
 424                         p = get_kprobe(addr);
 425                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
 426                             (kcb->kprobe_status == KPROBE_REENTER)) {
 427                                 if (post_kprobe_handler(args->regs))
 428                                         ret = NOTIFY_STOP;
 429                         } else {
 430                                 if (kprobe_handler(args->regs))
 431                                         ret = NOTIFY_STOP;
 432                         }
 433                 }
 434         }
 435
 436         return ret;
 437 }
 438
 439 static struct kprobe trampoline_p = {
 440         .addr = (kprobe_opcode_t *)&__kretprobe_trampoline,
 441         .pre_handler = trampoline_probe_handler
 442 };
 443
 444 int __init arch_init_kprobes(void)
 445 {
 446         return register_kprobe(&trampoline_p);
 447 }