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->set_hw_mode && insn->set_hw_mode(enable)) { 466 pr_warn("CPU[%u] cannot support the emulation of %s", 467 cpu, insn->name); 468 rc = -EINVAL; 469 } 470 } 471 local_irq_restore(flags); 472 473 return rc; 474 } 475 476 static int update_insn_emulation_mode(struct insn_emulation *insn, 477 enum insn_emulation_mode prev) 478 { 479 int ret = 0; 480 481 switch (prev) { 482 case INSN_UNDEF: /* Nothing to be done */ 483 break; 484 case INSN_EMULATE: 485 break; 486 case INSN_HW: 487 if (!run_all_cpu_set_hw_mode(insn, false)) 488 pr_notice("Disabled %s support\n", insn->name); 489 break; 490 } 491 492 switch (insn->current_mode) { 493 case INSN_UNDEF: 494 break; 495 case INSN_EMULATE: 496 break; 497 case INSN_HW: 498 ret = run_all_cpu_set_hw_mode(insn, true); 499 if (!ret) 500 pr_notice("Enabled %s support\n", insn->name); 501 break; 502 } 503 504 return ret; 505 } 506 507 static int emulation_proc_handler(struct ctl_table *table, int write, 508 void *buffer, size_t *lenp, 509 loff_t *ppos) 510 { 511 int ret = 0; 512 struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode); 513 enum insn_emulation_mode prev_mode = insn->current_mode; 514 515 mutex_lock(&insn_emulation_mutex); 516 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 517 518 if (ret || !write || prev_mode == insn->current_mode) 519 goto ret; 520 521 ret = update_insn_emulation_mode(insn, prev_mode); 522 if (ret) { 523 /* Mode change failed, revert to previous mode. */ 524 WRITE_ONCE(insn->current_mode, prev_mode); 525 update_insn_emulation_mode(insn, INSN_UNDEF); 526 } 527 ret: 528 mutex_unlock(&insn_emulation_mutex); 529 return ret; 530 } 531 532 static void __init register_insn_emulation(struct insn_emulation *insn) 533 { 534 struct ctl_table *sysctl; 535 536 insn->min = INSN_UNDEF; 537 538 switch (insn->status) { 539 case INSN_DEPRECATED: 540 insn->current_mode = INSN_EMULATE; 541 /* Disable the HW mode if it was turned on at early boot time */ 542 run_all_cpu_set_hw_mode(insn, false); 543 insn->max = INSN_HW; 544 break; 545 case INSN_OBSOLETE: 546 insn->current_mode = INSN_UNDEF; 547 insn->max = INSN_EMULATE; 548 break; 549 case INSN_UNAVAILABLE: 550 insn->current_mode = INSN_UNDEF; 551 insn->max = INSN_UNDEF; 552 break; 553 } 554 555 /* Program the HW if required */ 556 update_insn_emulation_mode(insn, INSN_UNDEF); 557 558 if (insn->status != INSN_UNAVAILABLE) { 559 sysctl = &insn->sysctl; 560 561 sysctl->mode = 0644; 562 sysctl->maxlen = sizeof(int); 563 564 sysctl->procname = insn->name; 565 sysctl->data = &insn->current_mode; 566 sysctl->extra1 = &insn->min; 567 sysctl->extra2 = &insn->max; 568 sysctl->proc_handler = emulation_proc_handler; 569 570 register_sysctl_sz("abi", sysctl, 1); 571 } 572 } 573 574 bool try_emulate_armv8_deprecated(struct pt_regs *regs, u32 insn) 575 { 576 for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) { 577 struct insn_emulation *ie = insn_emulations[i]; 578 579 if (ie->status == INSN_UNAVAILABLE) 580 continue; 581 582 /* 583 * A trap may race with the mode being changed 584 * INSN_EMULATE<->INSN_HW. Try to emulate the instruction to 585 * avoid a spurious UNDEF. 586 */ 587 if (READ_ONCE(ie->current_mode) == INSN_UNDEF) 588 continue; 589 590 if (ie->try_emulate(regs, insn)) 591 return true; 592 } 593 594 return false; 595 } 596 597 /* 598 * Invoked as core_initcall, which guarantees that the instruction 599 * emulation is ready for userspace. 600 */ 601 static int __init armv8_deprecated_init(void) 602 { 603 #ifdef CONFIG_SETEND_EMULATION 604 if (!system_supports_mixed_endian_el0()) { 605 insn_setend.status = INSN_UNAVAILABLE; 606 pr_info("setend instruction emulation is not supported on this system\n"); 607 } 608 609 #endif 610 for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) { 611 struct insn_emulation *ie = insn_emulations[i]; 612 613 if (ie->status == INSN_UNAVAILABLE) 614 continue; 615 616 register_insn_emulation(ie); 617 } 618 619 cpuhp_setup_state_nocalls(CPUHP_AP_ARM64_ISNDEP_STARTING, 620 "arm64/isndep:starting", 621 run_all_insn_set_hw_mode, NULL); 622 return 0; 623 } 624 625 core_initcall(armv8_deprecated_init); 626