arch/arm64/kernel/armv8_deprecated.c

   1 /*
   2  *  Copyright (C) 2014 ARM Limited
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/cpu.h>
  10 #include <linux/init.h>
  11 #include <linux/list.h>
  12 #include <linux/perf_event.h>
  13 #include <linux/sched.h>
  14 #include <linux/slab.h>
  15 #include <linux/sysctl.h>
  16
  17 #include <asm/alternative.h>
  18 #include <asm/cpufeature.h>
  19 #include <asm/insn.h>
  20 #include <asm/opcodes.h>
  21 #include <asm/sysreg.h>
  22 #include <asm/system_misc.h>
  23 #include <asm/traps.h>
  24 #include <asm/uaccess.h>
  25 #include <asm/cpufeature.h>
  26
  27 #define CREATE_TRACE_POINTS
  28 #include "trace-events-emulation.h"
  29
  30 /*
  31  * The runtime support for deprecated instruction support can be in one of
  32  * following three states -
  33  *
  34  * 0 = undef
  35  * 1 = emulate (software emulation)
  36  * 2 = hw (supported in hardware)
  37  */
  38 enum insn_emulation_mode {
  39         INSN_UNDEF,
  40         INSN_EMULATE,
  41         INSN_HW,
  42 };
  43
  44 enum legacy_insn_status {
  45         INSN_DEPRECATED,
  46         INSN_OBSOLETE,
  47 };
  48
  49 struct insn_emulation_ops {
  50         const char              *name;
  51         enum legacy_insn_status status;
  52         struct undef_hook       *hooks;
  53         int                     (*set_hw_mode)(bool enable);
  54 };
  55
  56 struct insn_emulation {
  57         struct list_head node;
  58         struct insn_emulation_ops *ops;
  59         int current_mode;
  60         int min;
  61         int max;
  62 };
  63
  64 static LIST_HEAD(insn_emulation);
  65 static int nr_insn_emulated;
  66 static DEFINE_RAW_SPINLOCK(insn_emulation_lock);
  67
  68 static void register_emulation_hooks(struct insn_emulation_ops *ops)
  69 {
  70         struct undef_hook *hook;
  71
  72         BUG_ON(!ops->hooks);
  73
  74         for (hook = ops->hooks; hook->instr_mask; hook++)
  75                 register_undef_hook(hook);
  76
  77         pr_notice("Registered %s emulation handler\n", ops->name);
  78 }
  79
  80 static void remove_emulation_hooks(struct insn_emulation_ops *ops)
  81 {
  82         struct undef_hook *hook;
  83
  84         BUG_ON(!ops->hooks);
  85
  86         for (hook = ops->hooks; hook->instr_mask; hook++)
  87                 unregister_undef_hook(hook);
  88
  89         pr_notice("Removed %s emulation handler\n", ops->name);
  90 }
  91
  92 static void enable_insn_hw_mode(void *data)
  93 {
  94         struct insn_emulation *insn = (struct insn_emulation *)data;
  95         if (insn->ops->set_hw_mode)
  96                 insn->ops->set_hw_mode(true);
  97 }
  98
  99 static void disable_insn_hw_mode(void *data)
 100 {
 101         struct insn_emulation *insn = (struct insn_emulation *)data;
 102         if (insn->ops->set_hw_mode)
 103                 insn->ops->set_hw_mode(false);
 104 }
 105
 106 /* Run set_hw_mode(mode) on all active CPUs */
 107 static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable)
 108 {
 109         if (!insn->ops->set_hw_mode)
 110                 return -EINVAL;
 111         if (enable)
 112                 on_each_cpu(enable_insn_hw_mode, (void *)insn, true);
 113         else
 114                 on_each_cpu(disable_insn_hw_mode, (void *)insn, true);
 115         return 0;
 116 }
 117
 118 /*
 119  * Run set_hw_mode for all insns on a starting CPU.
 120  * Returns:
 121  *  0           - If all the hooks ran successfully.
 122  * -EINVAL      - At least one hook is not supported by the CPU.
 123  */
 124 static int run_all_insn_set_hw_mode(unsigned long cpu)
 125 {
 126         int rc = 0;
 127         unsigned long flags;
 128         struct insn_emulation *insn;
 129
 130         raw_spin_lock_irqsave(&insn_emulation_lock, flags);
 131         list_for_each_entry(insn, &insn_emulation, node) {
 132                 bool enable = (insn->current_mode == INSN_HW);
 133                 if (insn->ops->set_hw_mode && insn->ops->set_hw_mode(enable)) {
 134                         pr_warn("CPU[%ld] cannot support the emulation of %s",
 135                                 cpu, insn->ops->name);
 136                         rc = -EINVAL;
 137                 }
 138         }
 139         raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
 140         return rc;
 141 }
 142
 143 static int update_insn_emulation_mode(struct insn_emulation *insn,
 144                                        enum insn_emulation_mode prev)
 145 {
 146         int ret = 0;
 147
 148         switch (prev) {
 149         case INSN_UNDEF: /* Nothing to be done */
 150                 break;
 151         case INSN_EMULATE:
 152                 remove_emulation_hooks(insn->ops);
 153                 break;
 154         case INSN_HW:
 155                 if (!run_all_cpu_set_hw_mode(insn, false))
 156                         pr_notice("Disabled %s support\n", insn->ops->name);
 157                 break;
 158         }
 159
 160         switch (insn->current_mode) {
 161         case INSN_UNDEF:
 162                 break;
 163         case INSN_EMULATE:
 164                 register_emulation_hooks(insn->ops);
 165                 break;
 166         case INSN_HW:
 167                 ret = run_all_cpu_set_hw_mode(insn, true);
 168                 if (!ret)
 169                         pr_notice("Enabled %s support\n", insn->ops->name);
 170                 break;
 171         }
 172
 173         return ret;
 174 }
 175
 176 static void register_insn_emulation(struct insn_emulation_ops *ops)
 177 {
 178         unsigned long flags;
 179         struct insn_emulation *insn;
 180
 181         insn = kzalloc(sizeof(*insn), GFP_KERNEL);
 182         insn->ops = ops;
 183         insn->min = INSN_UNDEF;
 184
 185         switch (ops->status) {
 186         case INSN_DEPRECATED:
 187                 insn->current_mode = INSN_EMULATE;
 188                 /* Disable the HW mode if it was turned on at early boot time */
 189                 run_all_cpu_set_hw_mode(insn, false);
 190                 insn->max = INSN_HW;
 191                 break;
 192         case INSN_OBSOLETE:
 193                 insn->current_mode = INSN_UNDEF;
 194                 insn->max = INSN_EMULATE;
 195                 break;
 196         }
 197
 198         raw_spin_lock_irqsave(&insn_emulation_lock, flags);
 199         list_add(&insn->node, &insn_emulation);
 200         nr_insn_emulated++;
 201         raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
 202
 203         /* Register any handlers if required */
 204         update_insn_emulation_mode(insn, INSN_UNDEF);
 205 }
 206
 207 static int emulation_proc_handler(struct ctl_table *table, int write,
 208                                   void __user *buffer, size_t *lenp,
 209                                   loff_t *ppos)
 210 {
 211         int ret = 0;
 212         struct insn_emulation *insn = (struct insn_emulation *) table->data;
 213         enum insn_emulation_mode prev_mode = insn->current_mode;
 214
 215         table->data = &insn->current_mode;
 216         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 217
 218         if (ret || !write || prev_mode == insn->current_mode)
 219                 goto ret;
 220
 221         ret = update_insn_emulation_mode(insn, prev_mode);
 222         if (ret) {
 223                 /* Mode change failed, revert to previous mode. */
 224                 insn->current_mode = prev_mode;
 225                 update_insn_emulation_mode(insn, INSN_UNDEF);
 226         }
 227 ret:
 228         table->data = insn;
 229         return ret;
 230 }
 231
 232 static struct ctl_table ctl_abi[] = {
 233         {
 234                 .procname = "abi",
 235                 .mode = 0555,
 236         },
 237         { }
 238 };
 239
 240 static void register_insn_emulation_sysctl(struct ctl_table *table)
 241 {
 242         unsigned long flags;
 243         int i = 0;
 244         struct insn_emulation *insn;
 245         struct ctl_table *insns_sysctl, *sysctl;
 246
 247         insns_sysctl = kzalloc(sizeof(*sysctl) * (nr_insn_emulated + 1),
 248                               GFP_KERNEL);
 249
 250         raw_spin_lock_irqsave(&insn_emulation_lock, flags);
 251         list_for_each_entry(insn, &insn_emulation, node) {
 252                 sysctl = &insns_sysctl[i];
 253
 254                 sysctl->mode = 0644;
 255                 sysctl->maxlen = sizeof(int);
 256
 257                 sysctl->procname = insn->ops->name;
 258                 sysctl->data = insn;
 259                 sysctl->extra1 = &insn->min;
 260                 sysctl->extra2 = &insn->max;
 261                 sysctl->proc_handler = emulation_proc_handler;
 262                 i++;
 263         }
 264         raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
 265
 266         table->child = insns_sysctl;
 267         register_sysctl_table(table);
 268 }
 269
 270 /*
 271  *  Implement emulation of the SWP/SWPB instructions using load-exclusive and
 272  *  store-exclusive.
 273  *
 274  *  Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
 275  *  Where: Rt  = destination
 276  *         Rt2 = source
 277  *         Rn  = address
 278  */
 279
 280 /*
 281  * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
 282  */
 283 #define __user_swpX_asm(data, addr, res, temp, B)               \
 284         __asm__ __volatile__(                                   \
 285         ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,    \
 286                     CONFIG_ARM64_PAN)                           \
 287         "0:     ldxr"B"         %w2, [%3]\n"                    \
 288         "1:     stxr"B"         %w0, %w1, [%3]\n"               \
 289         "       cbz             %w0, 2f\n"                      \
 290         "       mov             %w0, %w4\n"                     \
 291         "       b               3f\n"                           \
 292         "2:\n"                                                  \
 293         "       mov             %w1, %w2\n"                     \
 294         "3:\n"                                                  \
 295         "       .pushsection     .fixup,\"ax\"\n"               \
 296         "       .align          2\n"                            \
 297         "4:     mov             %w0, %w5\n"                     \
 298         "       b               3b\n"                           \
 299         "       .popsection"                                    \
 300         "       .pushsection     __ex_table,\"a\"\n"            \
 301         "       .align          3\n"                            \
 302         "       .quad           0b, 4b\n"                       \
 303         "       .quad           1b, 4b\n"                       \
 304         "       .popsection\n"                                  \
 305         ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,    \
 306                 CONFIG_ARM64_PAN)                               \
 307         : "=&r" (res), "+r" (data), "=&r" (temp)                \
 308         : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT)              \
 309         : "memory")
 310
 311 #define __user_swp_asm(data, addr, res, temp) \
 312         __user_swpX_asm(data, addr, res, temp, "")
 313 #define __user_swpb_asm(data, addr, res, temp) \
 314         __user_swpX_asm(data, addr, res, temp, "b")
 315
 316 /*
 317  * Bit 22 of the instruction encoding distinguishes between
 318  * the SWP and SWPB variants (bit set means SWPB).
 319  */
 320 #define TYPE_SWPB (1 << 22)
 321
 322 /*
 323  * Set up process info to signal segmentation fault - called on access error.
 324  */
 325 static void set_segfault(struct pt_regs *regs, unsigned long addr)
 326 {
 327         siginfo_t info;
 328
 329         down_read(&current->mm->mmap_sem);
 330         if (find_vma(current->mm, addr) == NULL)
 331                 info.si_code = SEGV_MAPERR;
 332         else
 333                 info.si_code = SEGV_ACCERR;
 334         up_read(&current->mm->mmap_sem);
 335
 336         info.si_signo = SIGSEGV;
 337         info.si_errno = 0;
 338         info.si_addr  = (void *) instruction_pointer(regs);
 339
 340         pr_debug("SWP{B} emulation: access caused memory abort!\n");
 341         arm64_notify_die("Illegal memory access", regs, &info, 0);
 342 }
 343
 344 static int emulate_swpX(unsigned int address, unsigned int *data,
 345                         unsigned int type)
 346 {
 347         unsigned int res = 0;
 348
 349         if ((type != TYPE_SWPB) && (address & 0x3)) {
 350                 /* SWP to unaligned address not permitted */
 351                 pr_debug("SWP instruction on unaligned pointer!\n");
 352                 return -EFAULT;
 353         }
 354
 355         while (1) {
 356                 unsigned long temp;
 357
 358                 if (type == TYPE_SWPB)
 359                         __user_swpb_asm(*data, address, res, temp);
 360                 else
 361                         __user_swp_asm(*data, address, res, temp);
 362
 363                 if (likely(res != -EAGAIN) || signal_pending(current))
 364                         break;
 365
 366                 cond_resched();
 367         }
 368
 369         return res;
 370 }
 371
 372 /*
 373  * swp_handler logs the id of calling process, dissects the instruction, sanity
 374  * checks the memory location, calls emulate_swpX for the actual operation and
 375  * deals with fixup/error handling before returning
 376  */
 377 static int swp_handler(struct pt_regs *regs, u32 instr)
 378 {
 379         u32 destreg, data, type, address = 0;
 380         int rn, rt2, res = 0;
 381
 382         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 383
 384         type = instr & TYPE_SWPB;
 385
 386         switch (arm_check_condition(instr, regs->pstate)) {
 387         case ARM_OPCODE_CONDTEST_PASS:
 388                 break;
 389         case ARM_OPCODE_CONDTEST_FAIL:
 390                 /* Condition failed - return to next instruction */
 391                 goto ret;
 392         case ARM_OPCODE_CONDTEST_UNCOND:
 393                 /* If unconditional encoding - not a SWP, undef */
 394                 return -EFAULT;
 395         default:
 396                 return -EINVAL;
 397         }
 398
 399         rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
 400         rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);
 401
 402         address = (u32)regs->user_regs.regs[rn];
 403         data    = (u32)regs->user_regs.regs[rt2];
 404         destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);
 405
 406         pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
 407                 rn, address, destreg,
 408                 aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);
 409
 410         /* Check access in reasonable access range for both SWP and SWPB */
 411         if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
 412                 pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
 413                         address);
 414                 goto fault;
 415         }
 416
 417         res = emulate_swpX(address, &data, type);
 418         if (res == -EFAULT)
 419                 goto fault;
 420         else if (res == 0)
 421                 regs->user_regs.regs[destreg] = data;
 422
 423 ret:
 424         if (type == TYPE_SWPB)
 425                 trace_instruction_emulation("swpb", regs->pc);
 426         else
 427                 trace_instruction_emulation("swp", regs->pc);
 428
 429         pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
 430                         current->comm, (unsigned long)current->pid, regs->pc);
 431
 432         regs->pc += 4;
 433         return 0;
 434
 435 fault:
 436         set_segfault(regs, address);
 437
 438         return 0;
 439 }
 440
 441 /*
 442  * Only emulate SWP/SWPB executed in ARM state/User mode.
 443  * The kernel must be SWP free and SWP{B} does not exist in Thumb.
 444  */
 445 static struct undef_hook swp_hooks[] = {
 446         {
 447                 .instr_mask     = 0x0fb00ff0,
 448                 .instr_val      = 0x01000090,
 449                 .pstate_mask    = COMPAT_PSR_MODE_MASK,
 450                 .pstate_val     = COMPAT_PSR_MODE_USR,
 451                 .fn             = swp_handler
 452         },
 453         { }
 454 };
 455
 456 static struct insn_emulation_ops swp_ops = {
 457         .name = "swp",
 458         .status = INSN_OBSOLETE,
 459         .hooks = swp_hooks,
 460         .set_hw_mode = NULL,
 461 };
 462
 463 static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
 464 {
 465         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 466
 467         switch (arm_check_condition(instr, regs->pstate)) {
 468         case ARM_OPCODE_CONDTEST_PASS:
 469                 break;
 470         case ARM_OPCODE_CONDTEST_FAIL:
 471                 /* Condition failed - return to next instruction */
 472                 goto ret;
 473         case ARM_OPCODE_CONDTEST_UNCOND:
 474                 /* If unconditional encoding - not a barrier instruction */
 475                 return -EFAULT;
 476         default:
 477                 return -EINVAL;
 478         }
 479
 480         switch (aarch32_insn_mcr_extract_crm(instr)) {
 481         case 10:
 482                 /*
 483                  * dmb - mcr p15, 0, Rt, c7, c10, 5
 484                  * dsb - mcr p15, 0, Rt, c7, c10, 4
 485                  */
 486                 if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
 487                         dmb(sy);
 488                         trace_instruction_emulation(
 489                                 "mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc);
 490                 } else {
 491                         dsb(sy);
 492                         trace_instruction_emulation(
 493                                 "mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc);
 494                 }
 495                 break;
 496         case 5:
 497                 /*
 498                  * isb - mcr p15, 0, Rt, c7, c5, 4
 499                  *
 500                  * Taking an exception or returning from one acts as an
 501                  * instruction barrier. So no explicit barrier needed here.
 502                  */
 503                 trace_instruction_emulation(
 504                         "mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc);
 505                 break;
 506         }
 507
 508 ret:
 509         pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
 510                         current->comm, (unsigned long)current->pid, regs->pc);
 511
 512         regs->pc += 4;
 513         return 0;
 514 }
 515
 516 static int cp15_barrier_set_hw_mode(bool enable)
 517 {
 518         if (enable)
 519                 config_sctlr_el1(0, SCTLR_EL1_CP15BEN);
 520         else
 521                 config_sctlr_el1(SCTLR_EL1_CP15BEN, 0);
 522         return 0;
 523 }
 524
 525 static struct undef_hook cp15_barrier_hooks[] = {
 526         {
 527                 .instr_mask     = 0x0fff0fdf,
 528                 .instr_val      = 0x0e070f9a,
 529                 .pstate_mask    = COMPAT_PSR_MODE_MASK,
 530                 .pstate_val     = COMPAT_PSR_MODE_USR,
 531                 .fn             = cp15barrier_handler,
 532         },
 533         {
 534                 .instr_mask     = 0x0fff0fff,
 535                 .instr_val      = 0x0e070f95,
 536                 .pstate_mask    = COMPAT_PSR_MODE_MASK,
 537                 .pstate_val     = COMPAT_PSR_MODE_USR,
 538                 .fn             = cp15barrier_handler,
 539         },
 540         { }
 541 };
 542
 543 static struct insn_emulation_ops cp15_barrier_ops = {
 544         .name = "cp15_barrier",
 545         .status = INSN_DEPRECATED,
 546         .hooks = cp15_barrier_hooks,
 547         .set_hw_mode = cp15_barrier_set_hw_mode,
 548 };
 549
 550 static int setend_set_hw_mode(bool enable)
 551 {
 552         if (!cpu_supports_mixed_endian_el0())
 553                 return -EINVAL;
 554
 555         if (enable)
 556                 config_sctlr_el1(SCTLR_EL1_SED, 0);
 557         else
 558                 config_sctlr_el1(0, SCTLR_EL1_SED);
 559         return 0;
 560 }
 561
 562 static int compat_setend_handler(struct pt_regs *regs, u32 big_endian)
 563 {
 564         char *insn;
 565
 566         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 567
 568         if (big_endian) {
 569                 insn = "setend be";
 570                 regs->pstate |= COMPAT_PSR_E_BIT;
 571         } else {
 572                 insn = "setend le";
 573                 regs->pstate &= ~COMPAT_PSR_E_BIT;
 574         }
 575
 576         trace_instruction_emulation(insn, regs->pc);
 577         pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n",
 578                         current->comm, (unsigned long)current->pid, regs->pc);
 579
 580         return 0;
 581 }
 582
 583 static int a32_setend_handler(struct pt_regs *regs, u32 instr)
 584 {
 585         int rc = compat_setend_handler(regs, (instr >> 9) & 1);
 586         regs->pc += 4;
 587         return rc;
 588 }
 589
 590 static int t16_setend_handler(struct pt_regs *regs, u32 instr)
 591 {
 592         int rc = compat_setend_handler(regs, (instr >> 3) & 1);
 593         regs->pc += 2;
 594         return rc;
 595 }
 596
 597 static struct undef_hook setend_hooks[] = {
 598         {
 599                 .instr_mask     = 0xfffffdff,
 600                 .instr_val      = 0xf1010000,
 601                 .pstate_mask    = COMPAT_PSR_MODE_MASK,
 602                 .pstate_val     = COMPAT_PSR_MODE_USR,
 603                 .fn             = a32_setend_handler,
 604         },
 605         {
 606                 /* Thumb mode */
 607                 .instr_mask     = 0x0000fff7,
 608                 .instr_val      = 0x0000b650,
 609                 .pstate_mask    = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_MASK),
 610                 .pstate_val     = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_USR),
 611                 .fn             = t16_setend_handler,
 612         },
 613         {}
 614 };
 615
 616 static struct insn_emulation_ops setend_ops = {
 617         .name = "setend",
 618         .status = INSN_DEPRECATED,
 619         .hooks = setend_hooks,
 620         .set_hw_mode = setend_set_hw_mode,
 621 };
 622
 623 static int insn_cpu_hotplug_notify(struct notifier_block *b,
 624                               unsigned long action, void *hcpu)
 625 {
 626         int rc = 0;
 627         if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
 628                 rc = run_all_insn_set_hw_mode((unsigned long)hcpu);
 629
 630         return notifier_from_errno(rc);
 631 }
 632
 633 static struct notifier_block insn_cpu_hotplug_notifier = {
 634         .notifier_call = insn_cpu_hotplug_notify,
 635 };
 636
 637 /*
 638  * Invoked as late_initcall, since not needed before init spawned.
 639  */
 640 static int __init armv8_deprecated_init(void)
 641 {
 642         if (IS_ENABLED(CONFIG_SWP_EMULATION))
 643                 register_insn_emulation(&swp_ops);
 644
 645         if (IS_ENABLED(CONFIG_CP15_BARRIER_EMULATION))
 646                 register_insn_emulation(&cp15_barrier_ops);
 647
 648         if (IS_ENABLED(CONFIG_SETEND_EMULATION)) {
 649                 if(system_supports_mixed_endian_el0())
 650                         register_insn_emulation(&setend_ops);
 651                 else
 652                         pr_info("setend instruction emulation is not supported on the system");
 653         }
 654
 655         register_cpu_notifier(&insn_cpu_hotplug_notifier);
 656         register_insn_emulation_sysctl(ctl_abi);
 657
 658         return 0;
 659 }
 660
 661 late_initcall(armv8_deprecated_init);