arch/arm64/kernel/armv8_deprecated.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2014 ARM Limited
   4  */
   5
   6 #include <linux/cpu.h>
   7 #include <linux/init.h>
   8 #include <linux/list.h>
   9 #include <linux/perf_event.h>
  10 #include <linux/sched.h>
  11 #include <linux/slab.h>
  12 #include <linux/sysctl.h>
  13 #include <linux/uaccess.h>
  14
  15 #include <asm/cpufeature.h>
  16 #include <asm/insn.h>
  17 #include <asm/sysreg.h>
  18 #include <asm/system_misc.h>
  19 #include <asm/traps.h>
  20
  21 #define CREATE_TRACE_POINTS
  22 #include "trace-events-emulation.h"
  23
  24 /*
  25  * The runtime support for deprecated instruction support can be in one of
  26  * following three states -
  27  *
  28  * 0 = undef
  29  * 1 = emulate (software emulation)
  30  * 2 = hw (supported in hardware)
  31  */
  32 enum insn_emulation_mode {
  33         INSN_UNDEF,
  34         INSN_EMULATE,
  35         INSN_HW,
  36 };
  37
  38 enum legacy_insn_status {
  39         INSN_DEPRECATED,
  40         INSN_OBSOLETE,
  41         INSN_UNAVAILABLE,
  42 };
  43
  44 struct insn_emulation {
  45         const char                      *name;
  46         enum legacy_insn_status         status;
  47         bool                            (*try_emulate)(struct pt_regs *regs,
  48                                                        u32 insn);
  49         int                             (*set_hw_mode)(bool enable);
  50
  51         int current_mode;
  52         int min;
  53         int max;
  54
  55         /* sysctl for this emulation */
  56         struct ctl_table sysctl;
  57 };
  58
  59 #define ARM_OPCODE_CONDTEST_FAIL   0
  60 #define ARM_OPCODE_CONDTEST_PASS   1
  61 #define ARM_OPCODE_CONDTEST_UNCOND 2
  62
  63 #define ARM_OPCODE_CONDITION_UNCOND     0xf
  64
  65 static unsigned int __maybe_unused aarch32_check_condition(u32 opcode, u32 psr)
  66 {
  67         u32 cc_bits  = opcode >> 28;
  68
  69         if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
  70                 if ((*aarch32_opcode_cond_checks[cc_bits])(psr))
  71                         return ARM_OPCODE_CONDTEST_PASS;
  72                 else
  73                         return ARM_OPCODE_CONDTEST_FAIL;
  74         }
  75         return ARM_OPCODE_CONDTEST_UNCOND;
  76 }
  77
  78 #ifdef CONFIG_SWP_EMULATION
  79 /*
  80  *  Implement emulation of the SWP/SWPB instructions using load-exclusive and
  81  *  store-exclusive.
  82  *
  83  *  Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
  84  *  Where: Rt  = destination
  85  *         Rt2 = source
  86  *         Rn  = address
  87  */
  88
  89 /*
  90  * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
  91  */
  92
  93 /* Arbitrary constant to ensure forward-progress of the LL/SC loop */
  94 #define __SWP_LL_SC_LOOPS       4
  95
  96 #define __user_swpX_asm(data, addr, res, temp, temp2, B)        \
  97 do {                                                            \
  98         uaccess_enable_privileged();                            \
  99         __asm__ __volatile__(                                   \
 100         "       mov             %w3, %w6\n"                     \
 101         "0:     ldxr"B"         %w2, [%4]\n"                    \
 102         "1:     stxr"B"         %w0, %w1, [%4]\n"               \
 103         "       cbz             %w0, 2f\n"                      \
 104         "       sub             %w3, %w3, #1\n"                 \
 105         "       cbnz            %w3, 0b\n"                      \
 106         "       mov             %w0, %w5\n"                     \
 107         "       b               3f\n"                           \
 108         "2:\n"                                                  \
 109         "       mov             %w1, %w2\n"                     \
 110         "3:\n"                                                  \
 111         _ASM_EXTABLE_UACCESS_ERR(0b, 3b, %w0)                   \
 112         _ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0)                   \
 113         : "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \
 114         : "r" ((unsigned long)addr), "i" (-EAGAIN),             \
 115           "i" (__SWP_LL_SC_LOOPS)                               \
 116         : "memory");                                            \
 117         uaccess_disable_privileged();                           \
 118 } while (0)
 119
 120 #define __user_swp_asm(data, addr, res, temp, temp2) \
 121         __user_swpX_asm(data, addr, res, temp, temp2, "")
 122 #define __user_swpb_asm(data, addr, res, temp, temp2) \
 123         __user_swpX_asm(data, addr, res, temp, temp2, "b")
 124
 125 /*
 126  * Bit 22 of the instruction encoding distinguishes between
 127  * the SWP and SWPB variants (bit set means SWPB).
 128  */
 129 #define TYPE_SWPB (1 << 22)
 130
 131 static int emulate_swpX(unsigned int address, unsigned int *data,
 132                         unsigned int type)
 133 {
 134         unsigned int res = 0;
 135
 136         if ((type != TYPE_SWPB) && (address & 0x3)) {
 137                 /* SWP to unaligned address not permitted */
 138                 pr_debug("SWP instruction on unaligned pointer!\n");
 139                 return -EFAULT;
 140         }
 141
 142         while (1) {
 143                 unsigned long temp, temp2;
 144
 145                 if (type == TYPE_SWPB)
 146                         __user_swpb_asm(*data, address, res, temp, temp2);
 147                 else
 148                         __user_swp_asm(*data, address, res, temp, temp2);
 149
 150                 if (likely(res != -EAGAIN) || signal_pending(current))
 151                         break;
 152
 153                 cond_resched();
 154         }
 155
 156         return res;
 157 }
 158
 159 /*
 160  * swp_handler logs the id of calling process, dissects the instruction, sanity
 161  * checks the memory location, calls emulate_swpX for the actual operation and
 162  * deals with fixup/error handling before returning
 163  */
 164 static int swp_handler(struct pt_regs *regs, u32 instr)
 165 {
 166         u32 destreg, data, type, address = 0;
 167         const void __user *user_ptr;
 168         int rn, rt2, res = 0;
 169
 170         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 171
 172         type = instr & TYPE_SWPB;
 173
 174         switch (aarch32_check_condition(instr, regs->pstate)) {
 175         case ARM_OPCODE_CONDTEST_PASS:
 176                 break;
 177         case ARM_OPCODE_CONDTEST_FAIL:
 178                 /* Condition failed - return to next instruction */
 179                 goto ret;
 180         case ARM_OPCODE_CONDTEST_UNCOND:
 181                 /* If unconditional encoding - not a SWP, undef */
 182                 return -EFAULT;
 183         default:
 184                 return -EINVAL;
 185         }
 186
 187         rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
 188         rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);
 189
 190         address = (u32)regs->user_regs.regs[rn];
 191         data    = (u32)regs->user_regs.regs[rt2];
 192         destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);
 193
 194         pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
 195                 rn, address, destreg,
 196                 aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);
 197
 198         /* Check access in reasonable access range for both SWP and SWPB */
 199         user_ptr = (const void __user *)(unsigned long)(address & ~3);
 200         if (!access_ok(user_ptr, 4)) {
 201                 pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
 202                         address);
 203                 goto fault;
 204         }
 205
 206         res = emulate_swpX(address, &data, type);
 207         if (res == -EFAULT)
 208                 goto fault;
 209         else if (res == 0)
 210                 regs->user_regs.regs[destreg] = data;
 211
 212 ret:
 213         if (type == TYPE_SWPB)
 214                 trace_instruction_emulation("swpb", regs->pc);
 215         else
 216                 trace_instruction_emulation("swp", regs->pc);
 217
 218         pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
 219                         current->comm, (unsigned long)current->pid, regs->pc);
 220
 221         arm64_skip_faulting_instruction(regs, 4);
 222         return 0;
 223
 224 fault:
 225         pr_debug("SWP{B} emulation: access caused memory abort!\n");
 226         arm64_notify_segfault(address);
 227
 228         return 0;
 229 }
 230
 231 static bool try_emulate_swp(struct pt_regs *regs, u32 insn)
 232 {
 233         /* SWP{B} only exists in ARM state and does not exist in Thumb */
 234         if (!compat_user_mode(regs) || compat_thumb_mode(regs))
 235                 return false;
 236
 237         if ((insn & 0x0fb00ff0) != 0x01000090)
 238                 return false;
 239
 240         return swp_handler(regs, insn) == 0;
 241 }
 242
 243 static struct insn_emulation insn_swp = {
 244         .name = "swp",
 245         .status = INSN_OBSOLETE,
 246         .try_emulate = try_emulate_swp,
 247         .set_hw_mode = NULL,
 248 };
 249 #endif /* CONFIG_SWP_EMULATION */
 250
 251 #ifdef CONFIG_CP15_BARRIER_EMULATION
 252 static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
 253 {
 254         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 255
 256         switch (aarch32_check_condition(instr, regs->pstate)) {
 257         case ARM_OPCODE_CONDTEST_PASS:
 258                 break;
 259         case ARM_OPCODE_CONDTEST_FAIL:
 260                 /* Condition failed - return to next instruction */
 261                 goto ret;
 262         case ARM_OPCODE_CONDTEST_UNCOND:
 263                 /* If unconditional encoding - not a barrier instruction */
 264                 return -EFAULT;
 265         default:
 266                 return -EINVAL;
 267         }
 268
 269         switch (aarch32_insn_mcr_extract_crm(instr)) {
 270         case 10:
 271                 /*
 272                  * dmb - mcr p15, 0, Rt, c7, c10, 5
 273                  * dsb - mcr p15, 0, Rt, c7, c10, 4
 274                  */
 275                 if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
 276                         dmb(sy);
 277                         trace_instruction_emulation(
 278                                 "mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc);
 279                 } else {
 280                         dsb(sy);
 281                         trace_instruction_emulation(
 282                                 "mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc);
 283                 }
 284                 break;
 285         case 5:
 286                 /*
 287                  * isb - mcr p15, 0, Rt, c7, c5, 4
 288                  *
 289                  * Taking an exception or returning from one acts as an
 290                  * instruction barrier. So no explicit barrier needed here.
 291                  */
 292                 trace_instruction_emulation(
 293                         "mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc);
 294                 break;
 295         }
 296
 297 ret:
 298         pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
 299                         current->comm, (unsigned long)current->pid, regs->pc);
 300
 301         arm64_skip_faulting_instruction(regs, 4);
 302         return 0;
 303 }
 304
 305 static int cp15_barrier_set_hw_mode(bool enable)
 306 {
 307         if (enable)
 308                 sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_CP15BEN);
 309         else
 310                 sysreg_clear_set(sctlr_el1, SCTLR_EL1_CP15BEN, 0);
 311         return 0;
 312 }
 313
 314 static bool try_emulate_cp15_barrier(struct pt_regs *regs, u32 insn)
 315 {
 316         if (!compat_user_mode(regs) || compat_thumb_mode(regs))
 317                 return false;
 318
 319         if ((insn & 0x0fff0fdf) == 0x0e070f9a)
 320                 return cp15barrier_handler(regs, insn) == 0;
 321
 322         if ((insn & 0x0fff0fff) == 0x0e070f95)
 323                 return cp15barrier_handler(regs, insn) == 0;
 324
 325         return false;
 326 }
 327
 328 static struct insn_emulation insn_cp15_barrier = {
 329         .name = "cp15_barrier",
 330         .status = INSN_DEPRECATED,
 331         .try_emulate = try_emulate_cp15_barrier,
 332         .set_hw_mode = cp15_barrier_set_hw_mode,
 333 };
 334 #endif /* CONFIG_CP15_BARRIER_EMULATION */
 335
 336 #ifdef CONFIG_SETEND_EMULATION
 337 static int setend_set_hw_mode(bool enable)
 338 {
 339         if (!cpu_supports_mixed_endian_el0())
 340                 return -EINVAL;
 341
 342         if (enable)
 343                 sysreg_clear_set(sctlr_el1, SCTLR_EL1_SED, 0);
 344         else
 345                 sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_SED);
 346         return 0;
 347 }
 348
 349 static int compat_setend_handler(struct pt_regs *regs, u32 big_endian)
 350 {
 351         char *insn;
 352
 353         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
 354
 355         if (big_endian) {
 356                 insn = "setend be";
 357                 regs->pstate |= PSR_AA32_E_BIT;
 358         } else {
 359                 insn = "setend le";
 360                 regs->pstate &= ~PSR_AA32_E_BIT;
 361         }
 362
 363         trace_instruction_emulation(insn, regs->pc);
 364         pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n",
 365                         current->comm, (unsigned long)current->pid, regs->pc);
 366
 367         return 0;
 368 }
 369
 370 static int a32_setend_handler(struct pt_regs *regs, u32 instr)
 371 {
 372         int rc = compat_setend_handler(regs, (instr >> 9) & 1);
 373         arm64_skip_faulting_instruction(regs, 4);
 374         return rc;
 375 }
 376
 377 static int t16_setend_handler(struct pt_regs *regs, u32 instr)
 378 {
 379         int rc = compat_setend_handler(regs, (instr >> 3) & 1);
 380         arm64_skip_faulting_instruction(regs, 2);
 381         return rc;
 382 }
 383
 384 static bool try_emulate_setend(struct pt_regs *regs, u32 insn)
 385 {
 386         if (compat_thumb_mode(regs) &&
 387             (insn & 0xfffffff7) == 0x0000b650)
 388                 return t16_setend_handler(regs, insn) == 0;
 389
 390         if (compat_user_mode(regs) &&
 391             (insn & 0xfffffdff) == 0xf1010000)
 392                 return a32_setend_handler(regs, insn) == 0;
 393
 394         return false;
 395 }
 396
 397 static struct insn_emulation insn_setend = {
 398         .name = "setend",
 399         .status = INSN_DEPRECATED,
 400         .try_emulate = try_emulate_setend,
 401         .set_hw_mode = setend_set_hw_mode,
 402 };
 403 #endif /* CONFIG_SETEND_EMULATION */
 404
 405 static struct insn_emulation *insn_emulations[] = {
 406 #ifdef CONFIG_SWP_EMULATION
 407         &insn_swp,
 408 #endif
 409 #ifdef CONFIG_CP15_BARRIER_EMULATION
 410         &insn_cp15_barrier,
 411 #endif
 412 #ifdef CONFIG_SETEND_EMULATION
 413         &insn_setend,
 414 #endif
 415 };
 416
 417 static DEFINE_MUTEX(insn_emulation_mutex);
 418
 419 static void enable_insn_hw_mode(void *data)
 420 {
 421         struct insn_emulation *insn = data;
 422         if (insn->set_hw_mode)
 423                 insn->set_hw_mode(true);
 424 }
 425
 426 static void disable_insn_hw_mode(void *data)
 427 {
 428         struct insn_emulation *insn = data;
 429         if (insn->set_hw_mode)
 430                 insn->set_hw_mode(false);
 431 }
 432
 433 /* Run set_hw_mode(mode) on all active CPUs */
 434 static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable)
 435 {
 436         if (!insn->set_hw_mode)
 437                 return -EINVAL;
 438         if (enable)
 439                 on_each_cpu(enable_insn_hw_mode, (void *)insn, true);
 440         else
 441                 on_each_cpu(disable_insn_hw_mode, (void *)insn, true);
 442         return 0;
 443 }
 444
 445 /*
 446  * Run set_hw_mode for all insns on a starting CPU.
 447  * Returns:
 448  *  0           - If all the hooks ran successfully.
 449  * -EINVAL      - At least one hook is not supported by the CPU.
 450  */
 451 static int run_all_insn_set_hw_mode(unsigned int cpu)
 452 {
 453         int rc = 0;
 454         unsigned long flags;
 455
 456         /*
 457          * Disable IRQs to serialize against an IPI from
 458          * run_all_cpu_set_hw_mode(), ensuring the HW is programmed to the most
 459          * recent enablement state if the two race with one another.
 460          */
 461         local_irq_save(flags);
 462         for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
 463                 struct insn_emulation *insn = insn_emulations[i];
 464                 bool enable = READ_ONCE(insn->current_mode) == INSN_HW;
 465                 if (insn->status == INSN_UNAVAILABLE)
 466                         continue;
 467
 468                 if (insn->set_hw_mode && insn->set_hw_mode(enable)) {
 469                         pr_warn("CPU[%u] cannot support the emulation of %s",
 470                                 cpu, insn->name);
 471                         rc = -EINVAL;
 472                 }
 473         }
 474         local_irq_restore(flags);
 475
 476         return rc;
 477 }
 478
 479 static int update_insn_emulation_mode(struct insn_emulation *insn,
 480                                        enum insn_emulation_mode prev)
 481 {
 482         int ret = 0;
 483
 484         switch (prev) {
 485         case INSN_UNDEF: /* Nothing to be done */
 486                 break;
 487         case INSN_EMULATE:
 488                 break;
 489         case INSN_HW:
 490                 if (!run_all_cpu_set_hw_mode(insn, false))
 491                         pr_notice("Disabled %s support\n", insn->name);
 492                 break;
 493         }
 494
 495         switch (insn->current_mode) {
 496         case INSN_UNDEF:
 497                 break;
 498         case INSN_EMULATE:
 499                 break;
 500         case INSN_HW:
 501                 ret = run_all_cpu_set_hw_mode(insn, true);
 502                 if (!ret)
 503                         pr_notice("Enabled %s support\n", insn->name);
 504                 break;
 505         }
 506
 507         return ret;
 508 }
 509
 510 static int emulation_proc_handler(const struct ctl_table *table, int write,
 511                                   void *buffer, size_t *lenp,
 512                                   loff_t *ppos)
 513 {
 514         int ret = 0;
 515         struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode);
 516         enum insn_emulation_mode prev_mode = insn->current_mode;
 517
 518         mutex_lock(&insn_emulation_mutex);
 519         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 520
 521         if (ret || !write || prev_mode == insn->current_mode)
 522                 goto ret;
 523
 524         ret = update_insn_emulation_mode(insn, prev_mode);
 525         if (ret) {
 526                 /* Mode change failed, revert to previous mode. */
 527                 WRITE_ONCE(insn->current_mode, prev_mode);
 528                 update_insn_emulation_mode(insn, INSN_UNDEF);
 529         }
 530 ret:
 531         mutex_unlock(&insn_emulation_mutex);
 532         return ret;
 533 }
 534
 535 static void __init register_insn_emulation(struct insn_emulation *insn)
 536 {
 537         struct ctl_table *sysctl;
 538
 539         insn->min = INSN_UNDEF;
 540
 541         switch (insn->status) {
 542         case INSN_DEPRECATED:
 543                 insn->current_mode = INSN_EMULATE;
 544                 /* Disable the HW mode if it was turned on at early boot time */
 545                 run_all_cpu_set_hw_mode(insn, false);
 546                 insn->max = INSN_HW;
 547                 break;
 548         case INSN_OBSOLETE:
 549                 insn->current_mode = INSN_UNDEF;
 550                 insn->max = INSN_EMULATE;
 551                 break;
 552         case INSN_UNAVAILABLE:
 553                 insn->current_mode = INSN_UNDEF;
 554                 insn->max = INSN_UNDEF;
 555                 break;
 556         }
 557
 558         /* Program the HW if required */
 559         update_insn_emulation_mode(insn, INSN_UNDEF);
 560
 561         if (insn->status != INSN_UNAVAILABLE) {
 562                 sysctl = &insn->sysctl;
 563
 564                 sysctl->mode = 0644;
 565                 sysctl->maxlen = sizeof(int);
 566
 567                 sysctl->procname = insn->name;
 568                 sysctl->data = &insn->current_mode;
 569                 sysctl->extra1 = &insn->min;
 570                 sysctl->extra2 = &insn->max;
 571                 sysctl->proc_handler = emulation_proc_handler;
 572
 573                 register_sysctl_sz("abi", sysctl, 1);
 574         }
 575 }
 576
 577 bool try_emulate_armv8_deprecated(struct pt_regs *regs, u32 insn)
 578 {
 579         for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
 580                 struct insn_emulation *ie = insn_emulations[i];
 581
 582                 if (ie->status == INSN_UNAVAILABLE)
 583                         continue;
 584
 585                 /*
 586                  * A trap may race with the mode being changed
 587                  * INSN_EMULATE<->INSN_HW. Try to emulate the instruction to
 588                  * avoid a spurious UNDEF.
 589                  */
 590                 if (READ_ONCE(ie->current_mode) == INSN_UNDEF)
 591                         continue;
 592
 593                 if (ie->try_emulate(regs, insn))
 594                         return true;
 595         }
 596
 597         return false;
 598 }
 599
 600 /*
 601  * Invoked as core_initcall, which guarantees that the instruction
 602  * emulation is ready for userspace.
 603  */
 604 static int __init armv8_deprecated_init(void)
 605 {
 606 #ifdef CONFIG_SETEND_EMULATION
 607         if (!system_supports_mixed_endian_el0()) {
 608                 insn_setend.status = INSN_UNAVAILABLE;
 609                 pr_info("setend instruction emulation is not supported on this system\n");
 610         }
 611
 612 #endif
 613         for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
 614                 struct insn_emulation *ie = insn_emulations[i];
 615
 616                 if (ie->status == INSN_UNAVAILABLE)
 617                         continue;
 618
 619                 register_insn_emulation(ie);
 620         }
 621
 622         cpuhp_setup_state_nocalls(CPUHP_AP_ARM64_ISNDEP_STARTING,
 623                                   "arm64/isndep:starting",
 624                                   run_all_insn_set_hw_mode, NULL);
 625         return 0;
 626 }
 627
 628 core_initcall(armv8_deprecated_init);