arch/arm64/kernel/hw_breakpoint.c

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