1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility, 4 * using the CPU's debug registers. 5 * 6 * Copyright (C) 2012 ARM Limited 7 * Author: Will Deacon <will.deacon@arm.com> 8 */ 9 10 #define pr_fmt(fmt) "hw-breakpoint: " fmt 11 12 #include <linux/compat.h> 13 #include <linux/cpu_pm.h> 14 #include <linux/errno.h> 15 #include <linux/hw_breakpoint.h> 16 #include <linux/kprobes.h> 17 #include <linux/perf_event.h> 18 #include <linux/ptrace.h> 19 #include <linux/smp.h> 20 #include <linux/uaccess.h> 21 22 #include <asm/current.h> 23 #include <asm/debug-monitors.h> 24 #include <asm/hw_breakpoint.h> 25 #include <asm/traps.h> 26 #include <asm/cputype.h> 27 #include <asm/system_misc.h> 28 29 /* Breakpoint currently in use for each BRP. */ 30 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]); 31 32 /* Watchpoint currently in use for each WRP. */ 33 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]); 34 35 /* Currently stepping a per-CPU kernel breakpoint. */ 36 static DEFINE_PER_CPU(int, stepping_kernel_bp); 37 38 /* Number of BRP/WRP registers on this CPU. */ 39 static int core_num_brps; 40 static int core_num_wrps; 41 42 int hw_breakpoint_slots(int type) 43 { 44 /* 45 * We can be called early, so don't rely on 46 * our static variables being initialised. 47 */ 48 switch (type) { 49 case TYPE_INST: 50 return get_num_brps(); 51 case TYPE_DATA: 52 return get_num_wrps(); 53 default: 54 pr_warn("unknown slot type: %d\n", type); 55 return 0; 56 } 57 } 58 59 #define READ_WB_REG_CASE(OFF, N, REG, VAL) \ 60 case (OFF + N): \ 61 AARCH64_DBG_READ(N, REG, VAL); \ 62 break 63 64 #define WRITE_WB_REG_CASE(OFF, N, REG, VAL) \ 65 case (OFF + N): \ 66 AARCH64_DBG_WRITE(N, REG, VAL); \ 67 break 68 69 #define GEN_READ_WB_REG_CASES(OFF, REG, VAL) \ 70 READ_WB_REG_CASE(OFF, 0, REG, VAL); \ 71 READ_WB_REG_CASE(OFF, 1, REG, VAL); \ 72 READ_WB_REG_CASE(OFF, 2, REG, VAL); \ 73 READ_WB_REG_CASE(OFF, 3, REG, VAL); \ 74 READ_WB_REG_CASE(OFF, 4, REG, VAL); \ 75 READ_WB_REG_CASE(OFF, 5, REG, VAL); \ 76 READ_WB_REG_CASE(OFF, 6, REG, VAL); \ 77 READ_WB_REG_CASE(OFF, 7, REG, VAL); \ 78 READ_WB_REG_CASE(OFF, 8, REG, VAL); \ 79 READ_WB_REG_CASE(OFF, 9, REG, VAL); \ 80 READ_WB_REG_CASE(OFF, 10, REG, VAL); \ 81 READ_WB_REG_CASE(OFF, 11, REG, VAL); \ 82 READ_WB_REG_CASE(OFF, 12, REG, VAL); \ 83 READ_WB_REG_CASE(OFF, 13, REG, VAL); \ 84 READ_WB_REG_CASE(OFF, 14, REG, VAL); \ 85 READ_WB_REG_CASE(OFF, 15, REG, VAL) 86 87 #define GEN_WRITE_WB_REG_CASES(OFF, REG, VAL) \ 88 WRITE_WB_REG_CASE(OFF, 0, REG, VAL); \ 89 WRITE_WB_REG_CASE(OFF, 1, REG, VAL); \ 90 WRITE_WB_REG_CASE(OFF, 2, REG, VAL); \ 91 WRITE_WB_REG_CASE(OFF, 3, REG, VAL); \ 92 WRITE_WB_REG_CASE(OFF, 4, REG, VAL); \ 93 WRITE_WB_REG_CASE(OFF, 5, REG, VAL); \ 94 WRITE_WB_REG_CASE(OFF, 6, REG, VAL); \ 95 WRITE_WB_REG_CASE(OFF, 7, REG, VAL); \ 96 WRITE_WB_REG_CASE(OFF, 8, REG, VAL); \ 97 WRITE_WB_REG_CASE(OFF, 9, REG, VAL); \ 98 WRITE_WB_REG_CASE(OFF, 10, REG, VAL); \ 99 WRITE_WB_REG_CASE(OFF, 11, REG, VAL); \ 100 WRITE_WB_REG_CASE(OFF, 12, REG, VAL); \ 101 WRITE_WB_REG_CASE(OFF, 13, REG, VAL); \ 102 WRITE_WB_REG_CASE(OFF, 14, REG, VAL); \ 103 WRITE_WB_REG_CASE(OFF, 15, REG, VAL) 104 105 static u64 read_wb_reg(int reg, int n) 106 { 107 u64 val = 0; 108 109 switch (reg + n) { 110 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val); 111 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val); 112 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val); 113 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val); 114 default: 115 pr_warn("attempt to read from unknown breakpoint register %d\n", n); 116 } 117 118 return val; 119 } 120 NOKPROBE_SYMBOL(read_wb_reg); 121 122 static void write_wb_reg(int reg, int n, u64 val) 123 { 124 switch (reg + n) { 125 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val); 126 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val); 127 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val); 128 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val); 129 default: 130 pr_warn("attempt to write to unknown breakpoint register %d\n", n); 131 } 132 isb(); 133 } 134 NOKPROBE_SYMBOL(write_wb_reg); 135 136 /* 137 * Convert a breakpoint privilege level to the corresponding exception 138 * level. 139 */ 140 static enum dbg_active_el debug_exception_level(int privilege) 141 { 142 switch (privilege) { 143 case AARCH64_BREAKPOINT_EL0: 144 return DBG_ACTIVE_EL0; 145 case AARCH64_BREAKPOINT_EL1: 146 return DBG_ACTIVE_EL1; 147 default: 148 pr_warn("invalid breakpoint privilege level %d\n", privilege); 149 return -EINVAL; 150 } 151 } 152 NOKPROBE_SYMBOL(debug_exception_level); 153 154 enum hw_breakpoint_ops { 155 HW_BREAKPOINT_INSTALL, 156 HW_BREAKPOINT_UNINSTALL, 157 HW_BREAKPOINT_RESTORE 158 }; 159 160 static int is_compat_bp(struct perf_event *bp) 161 { 162 struct task_struct *tsk = bp->hw.target; 163 164 /* 165 * tsk can be NULL for per-cpu (non-ptrace) breakpoints. 166 * In this case, use the native interface, since we don't have 167 * the notion of a "compat CPU" and could end up relying on 168 * deprecated behaviour if we use unaligned watchpoints in 169 * AArch64 state. 170 */ 171 return tsk && is_compat_thread(task_thread_info(tsk)); 172 } 173 174 /** 175 * hw_breakpoint_slot_setup - Find and setup a perf slot according to 176 * operations 177 * 178 * @slots: pointer to array of slots 179 * @max_slots: max number of slots 180 * @bp: perf_event to setup 181 * @ops: operation to be carried out on the slot 182 * 183 * Return: 184 * slot index on success 185 * -ENOSPC if no slot is available/matches 186 * -EINVAL on wrong operations parameter 187 */ 188 static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots, 189 struct perf_event *bp, 190 enum hw_breakpoint_ops ops) 191 { 192 int i; 193 struct perf_event **slot; 194 195 for (i = 0; i < max_slots; ++i) { 196 slot = &slots[i]; 197 switch (ops) { 198 case HW_BREAKPOINT_INSTALL: 199 if (!*slot) { 200 *slot = bp; 201 return i; 202 } 203 break; 204 case HW_BREAKPOINT_UNINSTALL: 205 if (*slot == bp) { 206 *slot = NULL; 207 return i; 208 } 209 break; 210 case HW_BREAKPOINT_RESTORE: 211 if (*slot == bp) 212 return i; 213 break; 214 default: 215 pr_warn_once("Unhandled hw breakpoint ops %d\n", ops); 216 return -EINVAL; 217 } 218 } 219 return -ENOSPC; 220 } 221 222 static int hw_breakpoint_control(struct perf_event *bp, 223 enum hw_breakpoint_ops ops) 224 { 225 struct arch_hw_breakpoint *info = counter_arch_bp(bp); 226 struct perf_event **slots; 227 struct debug_info *debug_info = ¤t->thread.debug; 228 int i, max_slots, ctrl_reg, val_reg, reg_enable; 229 enum dbg_active_el dbg_el = debug_exception_level(info->ctrl.privilege); 230 u32 ctrl; 231 232 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) { 233 /* Breakpoint */ 234 ctrl_reg = AARCH64_DBG_REG_BCR; 235 val_reg = AARCH64_DBG_REG_BVR; 236 slots = this_cpu_ptr(bp_on_reg); 237 max_slots = core_num_brps; 238 reg_enable = !debug_info->bps_disabled; 239 } else { 240 /* Watchpoint */ 241 ctrl_reg = AARCH64_DBG_REG_WCR; 242 val_reg = AARCH64_DBG_REG_WVR; 243 slots = this_cpu_ptr(wp_on_reg); 244 max_slots = core_num_wrps; 245 reg_enable = !debug_info->wps_disabled; 246 } 247 248 i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops); 249 250 if (WARN_ONCE(i < 0, "Can't find any breakpoint slot")) 251 return i; 252 253 switch (ops) { 254 case HW_BREAKPOINT_INSTALL: 255 /* 256 * Ensure debug monitors are enabled at the correct exception 257 * level. 258 */ 259 enable_debug_monitors(dbg_el); 260 fallthrough; 261 case HW_BREAKPOINT_RESTORE: 262 /* Setup the address register. */ 263 write_wb_reg(val_reg, i, info->address); 264 265 /* Setup the control register. */ 266 ctrl = encode_ctrl_reg(info->ctrl); 267 write_wb_reg(ctrl_reg, i, 268 reg_enable ? ctrl | 0x1 : ctrl & ~0x1); 269 break; 270 case HW_BREAKPOINT_UNINSTALL: 271 /* Reset the control register. */ 272 write_wb_reg(ctrl_reg, i, 0); 273 274 /* 275 * Release the debug monitors for the correct exception 276 * level. 277 */ 278 disable_debug_monitors(dbg_el); 279 break; 280 } 281 282 return 0; 283 } 284 285 /* 286 * Install a perf counter breakpoint. 287 */ 288 int arch_install_hw_breakpoint(struct perf_event *bp) 289 { 290 return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL); 291 } 292 293 void arch_uninstall_hw_breakpoint(struct perf_event *bp) 294 { 295 hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL); 296 } 297 298 static int get_hbp_len(u8 hbp_len) 299 { 300 unsigned int len_in_bytes = 0; 301 302 switch (hbp_len) { 303 case ARM_BREAKPOINT_LEN_1: 304 len_in_bytes = 1; 305 break; 306 case ARM_BREAKPOINT_LEN_2: 307 len_in_bytes = 2; 308 break; 309 case ARM_BREAKPOINT_LEN_3: 310 len_in_bytes = 3; 311 break; 312 case ARM_BREAKPOINT_LEN_4: 313 len_in_bytes = 4; 314 break; 315 case ARM_BREAKPOINT_LEN_5: 316 len_in_bytes = 5; 317 break; 318 case ARM_BREAKPOINT_LEN_6: 319 len_in_bytes = 6; 320 break; 321 case ARM_BREAKPOINT_LEN_7: 322 len_in_bytes = 7; 323 break; 324 case ARM_BREAKPOINT_LEN_8: 325 len_in_bytes = 8; 326 break; 327 } 328 329 return len_in_bytes; 330 } 331 332 /* 333 * Check whether bp virtual address is in kernel space. 334 */ 335 int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw) 336 { 337 unsigned int len; 338 unsigned long va; 339 340 va = hw->address; 341 len = get_hbp_len(hw->ctrl.len); 342 343 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); 344 } 345 346 /* 347 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl. 348 * Hopefully this will disappear when ptrace can bypass the conversion 349 * to generic breakpoint descriptions. 350 */ 351 int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl, 352 int *gen_len, int *gen_type, int *offset) 353 { 354 /* Type */ 355 switch (ctrl.type) { 356 case ARM_BREAKPOINT_EXECUTE: 357 *gen_type = HW_BREAKPOINT_X; 358 break; 359 case ARM_BREAKPOINT_LOAD: 360 *gen_type = HW_BREAKPOINT_R; 361 break; 362 case ARM_BREAKPOINT_STORE: 363 *gen_type = HW_BREAKPOINT_W; 364 break; 365 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE: 366 *gen_type = HW_BREAKPOINT_RW; 367 break; 368 default: 369 return -EINVAL; 370 } 371 372 if (!ctrl.len) 373 return -EINVAL; 374 *offset = __ffs(ctrl.len); 375 376 /* Len */ 377 switch (ctrl.len >> *offset) { 378 case ARM_BREAKPOINT_LEN_1: 379 *gen_len = HW_BREAKPOINT_LEN_1; 380 break; 381 case ARM_BREAKPOINT_LEN_2: 382 *gen_len = HW_BREAKPOINT_LEN_2; 383 break; 384 case ARM_BREAKPOINT_LEN_3: 385 *gen_len = HW_BREAKPOINT_LEN_3; 386 break; 387 case ARM_BREAKPOINT_LEN_4: 388 *gen_len = HW_BREAKPOINT_LEN_4; 389 break; 390 case ARM_BREAKPOINT_LEN_5: 391 *gen_len = HW_BREAKPOINT_LEN_5; 392 break; 393 case ARM_BREAKPOINT_LEN_6: 394 *gen_len = HW_BREAKPOINT_LEN_6; 395 break; 396 case ARM_BREAKPOINT_LEN_7: 397 *gen_len = HW_BREAKPOINT_LEN_7; 398 break; 399 case ARM_BREAKPOINT_LEN_8: 400 *gen_len = HW_BREAKPOINT_LEN_8; 401 break; 402 default: 403 return -EINVAL; 404 } 405 406 return 0; 407 } 408 409 /* 410 * Construct an arch_hw_breakpoint from a perf_event. 411 */ 412 static int arch_build_bp_info(struct perf_event *bp, 413 const struct perf_event_attr *attr, 414 struct arch_hw_breakpoint *hw) 415 { 416 /* Type */ 417 switch (attr->bp_type) { 418 case HW_BREAKPOINT_X: 419 hw->ctrl.type = ARM_BREAKPOINT_EXECUTE; 420 break; 421 case HW_BREAKPOINT_R: 422 hw->ctrl.type = ARM_BREAKPOINT_LOAD; 423 break; 424 case HW_BREAKPOINT_W: 425 hw->ctrl.type = ARM_BREAKPOINT_STORE; 426 break; 427 case HW_BREAKPOINT_RW: 428 hw->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE; 429 break; 430 default: 431 return -EINVAL; 432 } 433 434 /* Len */ 435 switch (attr->bp_len) { 436 case HW_BREAKPOINT_LEN_1: 437 hw->ctrl.len = ARM_BREAKPOINT_LEN_1; 438 break; 439 case HW_BREAKPOINT_LEN_2: 440 hw->ctrl.len = ARM_BREAKPOINT_LEN_2; 441 break; 442 case HW_BREAKPOINT_LEN_3: 443 hw->ctrl.len = ARM_BREAKPOINT_LEN_3; 444 break; 445 case HW_BREAKPOINT_LEN_4: 446 hw->ctrl.len = ARM_BREAKPOINT_LEN_4; 447 break; 448 case HW_BREAKPOINT_LEN_5: 449 hw->ctrl.len = ARM_BREAKPOINT_LEN_5; 450 break; 451 case HW_BREAKPOINT_LEN_6: 452 hw->ctrl.len = ARM_BREAKPOINT_LEN_6; 453 break; 454 case HW_BREAKPOINT_LEN_7: 455 hw->ctrl.len = ARM_BREAKPOINT_LEN_7; 456 break; 457 case HW_BREAKPOINT_LEN_8: 458 hw->ctrl.len = ARM_BREAKPOINT_LEN_8; 459 break; 460 default: 461 return -EINVAL; 462 } 463 464 /* 465 * On AArch64, we only permit breakpoints of length 4, whereas 466 * AArch32 also requires breakpoints of length 2 for Thumb. 467 * Watchpoints can be of length 1, 2, 4 or 8 bytes. 468 */ 469 if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE) { 470 if (is_compat_bp(bp)) { 471 if (hw->ctrl.len != ARM_BREAKPOINT_LEN_2 && 472 hw->ctrl.len != ARM_BREAKPOINT_LEN_4) 473 return -EINVAL; 474 } else if (hw->ctrl.len != ARM_BREAKPOINT_LEN_4) { 475 /* 476 * FIXME: Some tools (I'm looking at you perf) assume 477 * that breakpoints should be sizeof(long). This 478 * is nonsense. For now, we fix up the parameter 479 * but we should probably return -EINVAL instead. 480 */ 481 hw->ctrl.len = ARM_BREAKPOINT_LEN_4; 482 } 483 } 484 485 /* Address */ 486 hw->address = attr->bp_addr; 487 488 /* 489 * Privilege 490 * Note that we disallow combined EL0/EL1 breakpoints because 491 * that would complicate the stepping code. 492 */ 493 if (arch_check_bp_in_kernelspace(hw)) 494 hw->ctrl.privilege = AARCH64_BREAKPOINT_EL1; 495 else 496 hw->ctrl.privilege = AARCH64_BREAKPOINT_EL0; 497 498 /* Enabled? */ 499 hw->ctrl.enabled = !attr->disabled; 500 501 return 0; 502 } 503 504 /* 505 * Validate the arch-specific HW Breakpoint register settings. 506 */ 507 int hw_breakpoint_arch_parse(struct perf_event *bp, 508 const struct perf_event_attr *attr, 509 struct arch_hw_breakpoint *hw) 510 { 511 int ret; 512 u64 alignment_mask, offset; 513 514 /* Build the arch_hw_breakpoint. */ 515 ret = arch_build_bp_info(bp, attr, hw); 516 if (ret) 517 return ret; 518 519 /* 520 * Check address alignment. 521 * We don't do any clever alignment correction for watchpoints 522 * because using 64-bit unaligned addresses is deprecated for 523 * AArch64. 524 * 525 * AArch32 tasks expect some simple alignment fixups, so emulate 526 * that here. 527 */ 528 if (is_compat_bp(bp)) { 529 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8) 530 alignment_mask = 0x7; 531 else 532 alignment_mask = 0x3; 533 offset = hw->address & alignment_mask; 534 switch (offset) { 535 case 0: 536 /* Aligned */ 537 break; 538 case 1: 539 case 2: 540 /* Allow halfword watchpoints and breakpoints. */ 541 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2) 542 break; 543 544 fallthrough; 545 case 3: 546 /* Allow single byte watchpoint. */ 547 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) 548 break; 549 550 fallthrough; 551 default: 552 return -EINVAL; 553 } 554 } else { 555 if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE) 556 alignment_mask = 0x3; 557 else 558 alignment_mask = 0x7; 559 offset = hw->address & alignment_mask; 560 } 561 562 hw->address &= ~alignment_mask; 563 hw->ctrl.len <<= offset; 564 565 /* 566 * Disallow per-task kernel breakpoints since these would 567 * complicate the stepping code. 568 */ 569 if (hw->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.target) 570 return -EINVAL; 571 572 return 0; 573 } 574 575 /* 576 * Enable/disable all of the breakpoints active at the specified 577 * exception level at the register level. 578 * This is used when single-stepping after a breakpoint exception. 579 */ 580 static void toggle_bp_registers(int reg, enum dbg_active_el el, int enable) 581 { 582 int i, max_slots, privilege; 583 u32 ctrl; 584 struct perf_event **slots; 585 586 switch (reg) { 587 case AARCH64_DBG_REG_BCR: 588 slots = this_cpu_ptr(bp_on_reg); 589 max_slots = core_num_brps; 590 break; 591 case AARCH64_DBG_REG_WCR: 592 slots = this_cpu_ptr(wp_on_reg); 593 max_slots = core_num_wrps; 594 break; 595 default: 596 return; 597 } 598 599 for (i = 0; i < max_slots; ++i) { 600 if (!slots[i]) 601 continue; 602 603 privilege = counter_arch_bp(slots[i])->ctrl.privilege; 604 if (debug_exception_level(privilege) != el) 605 continue; 606 607 ctrl = read_wb_reg(reg, i); 608 if (enable) 609 ctrl |= 0x1; 610 else 611 ctrl &= ~0x1; 612 write_wb_reg(reg, i, ctrl); 613 } 614 } 615 NOKPROBE_SYMBOL(toggle_bp_registers); 616 617 /* 618 * Debug exception handlers. 619 */ 620 static int breakpoint_handler(unsigned long unused, unsigned int esr, 621 struct pt_regs *regs) 622 { 623 int i, step = 0, *kernel_step; 624 u32 ctrl_reg; 625 u64 addr, val; 626 struct perf_event *bp, **slots; 627 struct debug_info *debug_info; 628 struct arch_hw_breakpoint_ctrl ctrl; 629 630 slots = this_cpu_ptr(bp_on_reg); 631 addr = instruction_pointer(regs); 632 debug_info = ¤t->thread.debug; 633 634 for (i = 0; i < core_num_brps; ++i) { 635 rcu_read_lock(); 636 637 bp = slots[i]; 638 639 if (bp == NULL) 640 goto unlock; 641 642 /* Check if the breakpoint value matches. */ 643 val = read_wb_reg(AARCH64_DBG_REG_BVR, i); 644 if (val != (addr & ~0x3)) 645 goto unlock; 646 647 /* Possible match, check the byte address select to confirm. */ 648 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_BCR, i); 649 decode_ctrl_reg(ctrl_reg, &ctrl); 650 if (!((1 << (addr & 0x3)) & ctrl.len)) 651 goto unlock; 652 653 counter_arch_bp(bp)->trigger = addr; 654 perf_bp_event(bp, regs); 655 656 /* Do we need to handle the stepping? */ 657 if (is_default_overflow_handler(bp)) 658 step = 1; 659 unlock: 660 rcu_read_unlock(); 661 } 662 663 if (!step) 664 return 0; 665 666 if (user_mode(regs)) { 667 debug_info->bps_disabled = 1; 668 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 0); 669 670 /* If we're already stepping a watchpoint, just return. */ 671 if (debug_info->wps_disabled) 672 return 0; 673 674 if (test_thread_flag(TIF_SINGLESTEP)) 675 debug_info->suspended_step = 1; 676 else 677 user_enable_single_step(current); 678 } else { 679 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 0); 680 kernel_step = this_cpu_ptr(&stepping_kernel_bp); 681 682 if (*kernel_step != ARM_KERNEL_STEP_NONE) 683 return 0; 684 685 if (kernel_active_single_step()) { 686 *kernel_step = ARM_KERNEL_STEP_SUSPEND; 687 } else { 688 *kernel_step = ARM_KERNEL_STEP_ACTIVE; 689 kernel_enable_single_step(regs); 690 } 691 } 692 693 return 0; 694 } 695 NOKPROBE_SYMBOL(breakpoint_handler); 696 697 /* 698 * Arm64 hardware does not always report a watchpoint hit address that matches 699 * one of the watchpoints set. It can also report an address "near" the 700 * watchpoint if a single instruction access both watched and unwatched 701 * addresses. There is no straight-forward way, short of disassembling the 702 * offending instruction, to map that address back to the watchpoint. This 703 * function computes the distance of the memory access from the watchpoint as a 704 * heuristic for the likelihood that a given access triggered the watchpoint. 705 * 706 * See Section D2.10.5 "Determining the memory location that caused a Watchpoint 707 * exception" of ARMv8 Architecture Reference Manual for details. 708 * 709 * The function returns the distance of the address from the bytes watched by 710 * the watchpoint. In case of an exact match, it returns 0. 711 */ 712 static u64 get_distance_from_watchpoint(unsigned long addr, u64 val, 713 struct arch_hw_breakpoint_ctrl *ctrl) 714 { 715 u64 wp_low, wp_high; 716 u32 lens, lene; 717 718 addr = untagged_addr(addr); 719 720 lens = __ffs(ctrl->len); 721 lene = __fls(ctrl->len); 722 723 wp_low = val + lens; 724 wp_high = val + lene; 725 if (addr < wp_low) 726 return wp_low - addr; 727 else if (addr > wp_high) 728 return addr - wp_high; 729 else 730 return 0; 731 } 732 733 static int watchpoint_report(struct perf_event *wp, unsigned long addr, 734 struct pt_regs *regs) 735 { 736 int step = is_default_overflow_handler(wp); 737 struct arch_hw_breakpoint *info = counter_arch_bp(wp); 738 739 info->trigger = addr; 740 741 /* 742 * If we triggered a user watchpoint from a uaccess routine, then 743 * handle the stepping ourselves since userspace really can't help 744 * us with this. 745 */ 746 if (!user_mode(regs) && info->ctrl.privilege == AARCH64_BREAKPOINT_EL0) 747 step = 1; 748 else 749 perf_bp_event(wp, regs); 750 751 return step; 752 } 753 754 static int watchpoint_handler(unsigned long addr, unsigned int esr, 755 struct pt_regs *regs) 756 { 757 int i, step = 0, *kernel_step, access, closest_match = 0; 758 u64 min_dist = -1, dist; 759 u32 ctrl_reg; 760 u64 val; 761 struct perf_event *wp, **slots; 762 struct debug_info *debug_info; 763 struct arch_hw_breakpoint_ctrl ctrl; 764 765 slots = this_cpu_ptr(wp_on_reg); 766 debug_info = ¤t->thread.debug; 767 768 /* 769 * Find all watchpoints that match the reported address. If no exact 770 * match is found. Attribute the hit to the closest watchpoint. 771 */ 772 rcu_read_lock(); 773 for (i = 0; i < core_num_wrps; ++i) { 774 wp = slots[i]; 775 if (wp == NULL) 776 continue; 777 778 /* 779 * Check that the access type matches. 780 * 0 => load, otherwise => store 781 */ 782 access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W : 783 HW_BREAKPOINT_R; 784 if (!(access & hw_breakpoint_type(wp))) 785 continue; 786 787 /* Check if the watchpoint value and byte select match. */ 788 val = read_wb_reg(AARCH64_DBG_REG_WVR, i); 789 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i); 790 decode_ctrl_reg(ctrl_reg, &ctrl); 791 dist = get_distance_from_watchpoint(addr, val, &ctrl); 792 if (dist < min_dist) { 793 min_dist = dist; 794 closest_match = i; 795 } 796 /* Is this an exact match? */ 797 if (dist != 0) 798 continue; 799 800 step = watchpoint_report(wp, addr, regs); 801 } 802 803 /* No exact match found? */ 804 if (min_dist > 0 && min_dist != -1) 805 step = watchpoint_report(slots[closest_match], addr, regs); 806 807 rcu_read_unlock(); 808 809 if (!step) 810 return 0; 811 812 /* 813 * We always disable EL0 watchpoints because the kernel can 814 * cause these to fire via an unprivileged access. 815 */ 816 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 0); 817 818 if (user_mode(regs)) { 819 debug_info->wps_disabled = 1; 820 821 /* If we're already stepping a breakpoint, just return. */ 822 if (debug_info->bps_disabled) 823 return 0; 824 825 if (test_thread_flag(TIF_SINGLESTEP)) 826 debug_info->suspended_step = 1; 827 else 828 user_enable_single_step(current); 829 } else { 830 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 0); 831 kernel_step = this_cpu_ptr(&stepping_kernel_bp); 832 833 if (*kernel_step != ARM_KERNEL_STEP_NONE) 834 return 0; 835 836 if (kernel_active_single_step()) { 837 *kernel_step = ARM_KERNEL_STEP_SUSPEND; 838 } else { 839 *kernel_step = ARM_KERNEL_STEP_ACTIVE; 840 kernel_enable_single_step(regs); 841 } 842 } 843 844 return 0; 845 } 846 NOKPROBE_SYMBOL(watchpoint_handler); 847 848 /* 849 * Handle single-step exception. 850 */ 851 int reinstall_suspended_bps(struct pt_regs *regs) 852 { 853 struct debug_info *debug_info = ¤t->thread.debug; 854 int handled_exception = 0, *kernel_step; 855 856 kernel_step = this_cpu_ptr(&stepping_kernel_bp); 857 858 /* 859 * Called from single-step exception handler. 860 * Return 0 if execution can resume, 1 if a SIGTRAP should be 861 * reported. 862 */ 863 if (user_mode(regs)) { 864 if (debug_info->bps_disabled) { 865 debug_info->bps_disabled = 0; 866 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 1); 867 handled_exception = 1; 868 } 869 870 if (debug_info->wps_disabled) { 871 debug_info->wps_disabled = 0; 872 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1); 873 handled_exception = 1; 874 } 875 876 if (handled_exception) { 877 if (debug_info->suspended_step) { 878 debug_info->suspended_step = 0; 879 /* Allow exception handling to fall-through. */ 880 handled_exception = 0; 881 } else { 882 user_disable_single_step(current); 883 } 884 } 885 } else if (*kernel_step != ARM_KERNEL_STEP_NONE) { 886 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 1); 887 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 1); 888 889 if (!debug_info->wps_disabled) 890 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1); 891 892 if (*kernel_step != ARM_KERNEL_STEP_SUSPEND) { 893 kernel_disable_single_step(); 894 handled_exception = 1; 895 } else { 896 handled_exception = 0; 897 } 898 899 *kernel_step = ARM_KERNEL_STEP_NONE; 900 } 901 902 return !handled_exception; 903 } 904 NOKPROBE_SYMBOL(reinstall_suspended_bps); 905 906 /* 907 * Context-switcher for restoring suspended breakpoints. 908 */ 909 void hw_breakpoint_thread_switch(struct task_struct *next) 910 { 911 /* 912 * current next 913 * disabled: 0 0 => The usual case, NOTIFY_DONE 914 * 0 1 => Disable the registers 915 * 1 0 => Enable the registers 916 * 1 1 => NOTIFY_DONE. per-task bps will 917 * get taken care of by perf. 918 */ 919 920 struct debug_info *current_debug_info, *next_debug_info; 921 922 current_debug_info = ¤t->thread.debug; 923 next_debug_info = &next->thread.debug; 924 925 /* Update breakpoints. */ 926 if (current_debug_info->bps_disabled != next_debug_info->bps_disabled) 927 toggle_bp_registers(AARCH64_DBG_REG_BCR, 928 DBG_ACTIVE_EL0, 929 !next_debug_info->bps_disabled); 930 931 /* Update watchpoints. */ 932 if (current_debug_info->wps_disabled != next_debug_info->wps_disabled) 933 toggle_bp_registers(AARCH64_DBG_REG_WCR, 934 DBG_ACTIVE_EL0, 935 !next_debug_info->wps_disabled); 936 } 937 938 /* 939 * CPU initialisation. 940 */ 941 static int hw_breakpoint_reset(unsigned int cpu) 942 { 943 int i; 944 struct perf_event **slots; 945 /* 946 * When a CPU goes through cold-boot, it does not have any installed 947 * slot, so it is safe to share the same function for restoring and 948 * resetting breakpoints; when a CPU is hotplugged in, it goes 949 * through the slots, which are all empty, hence it just resets control 950 * and value for debug registers. 951 * When this function is triggered on warm-boot through a CPU PM 952 * notifier some slots might be initialized; if so they are 953 * reprogrammed according to the debug slots content. 954 */ 955 for (slots = this_cpu_ptr(bp_on_reg), i = 0; i < core_num_brps; ++i) { 956 if (slots[i]) { 957 hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE); 958 } else { 959 write_wb_reg(AARCH64_DBG_REG_BCR, i, 0UL); 960 write_wb_reg(AARCH64_DBG_REG_BVR, i, 0UL); 961 } 962 } 963 964 for (slots = this_cpu_ptr(wp_on_reg), i = 0; i < core_num_wrps; ++i) { 965 if (slots[i]) { 966 hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE); 967 } else { 968 write_wb_reg(AARCH64_DBG_REG_WCR, i, 0UL); 969 write_wb_reg(AARCH64_DBG_REG_WVR, i, 0UL); 970 } 971 } 972 973 return 0; 974 } 975 976 #ifdef CONFIG_CPU_PM 977 extern void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int)); 978 #else 979 static inline void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int)) 980 { 981 } 982 #endif 983 984 /* 985 * One-time initialisation. 986 */ 987 static int __init arch_hw_breakpoint_init(void) 988 { 989 int ret; 990 991 core_num_brps = get_num_brps(); 992 core_num_wrps = get_num_wrps(); 993 994 pr_info("found %d breakpoint and %d watchpoint registers.\n", 995 core_num_brps, core_num_wrps); 996 997 /* Register debug fault handlers. */ 998 hook_debug_fault_code(DBG_ESR_EVT_HWBP, breakpoint_handler, SIGTRAP, 999 TRAP_HWBKPT, "hw-breakpoint handler"); 1000 hook_debug_fault_code(DBG_ESR_EVT_HWWP, watchpoint_handler, SIGTRAP, 1001 TRAP_HWBKPT, "hw-watchpoint handler"); 1002 1003 /* 1004 * Reset the breakpoint resources. We assume that a halting 1005 * debugger will leave the world in a nice state for us. 1006 */ 1007 ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING, 1008 "perf/arm64/hw_breakpoint:starting", 1009 hw_breakpoint_reset, NULL); 1010 if (ret) 1011 pr_err("failed to register CPU hotplug notifier: %d\n", ret); 1012 1013 /* Register cpu_suspend hw breakpoint restore hook */ 1014 cpu_suspend_set_dbg_restorer(hw_breakpoint_reset); 1015 1016 return ret; 1017 } 1018 arch_initcall(arch_hw_breakpoint_init); 1019 1020 void hw_breakpoint_pmu_read(struct perf_event *bp) 1021 { 1022 } 1023 1024 /* 1025 * Dummy function to register with die_notifier. 1026 */ 1027 int hw_breakpoint_exceptions_notify(struct notifier_block *unused, 1028 unsigned long val, void *data) 1029 { 1030 return NOTIFY_DONE; 1031 } 1032