arch/arm64/kernel/hw_breakpoint.c

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