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 <will.deacon@arm.com>
   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/errno.h>
  24 #include <linux/hw_breakpoint.h>
  25 #include <linux/perf_event.h>
  26 #include <linux/ptrace.h>
  27 #include <linux/smp.h>
  28
  29 #include <asm/compat.h>
  30 #include <asm/current.h>
  31 #include <asm/debug-monitors.h>
  32 #include <asm/hw_breakpoint.h>
  33 #include <asm/kdebug.h>
  34 #include <asm/traps.h>
  35 #include <asm/cputype.h>
  36 #include <asm/system_misc.h>
  37
  38 /* Breakpoint currently in use for each BRP. */
  39 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
  40
  41 /* Watchpoint currently in use for each WRP. */
  42 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
  43
  44 /* Currently stepping a per-CPU kernel breakpoint. */
  45 static DEFINE_PER_CPU(int, stepping_kernel_bp);
  46
  47 /* Number of BRP/WRP registers on this CPU. */
  48 static int core_num_brps;
  49 static int core_num_wrps;
  50
  51 /* Determine number of BRP registers available. */
  52 static int get_num_brps(void)
  53 {
  54         return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1;
  55 }
  56
  57 /* Determine number of WRP registers available. */
  58 static int get_num_wrps(void)
  59 {
  60         return ((read_cpuid(ID_AA64DFR0_EL1) >> 20) & 0xf) + 1;
  61 }
  62
  63 int hw_breakpoint_slots(int type)
  64 {
  65         /*
  66          * We can be called early, so don't rely on
  67          * our static variables being initialised.
  68          */
  69         switch (type) {
  70         case TYPE_INST:
  71                 return get_num_brps();
  72         case TYPE_DATA:
  73                 return get_num_wrps();
  74         default:
  75                 pr_warning("unknown slot type: %d\n", type);
  76                 return 0;
  77         }
  78 }
  79
  80 #define READ_WB_REG_CASE(OFF, N, REG, VAL)      \
  81         case (OFF + N):                         \
  82                 AARCH64_DBG_READ(N, REG, VAL);  \
  83                 break
  84
  85 #define WRITE_WB_REG_CASE(OFF, N, REG, VAL)     \
  86         case (OFF + N):                         \
  87                 AARCH64_DBG_WRITE(N, REG, VAL); \
  88                 break
  89
  90 #define GEN_READ_WB_REG_CASES(OFF, REG, VAL)    \
  91         READ_WB_REG_CASE(OFF,  0, REG, VAL);    \
  92         READ_WB_REG_CASE(OFF,  1, REG, VAL);    \
  93         READ_WB_REG_CASE(OFF,  2, REG, VAL);    \
  94         READ_WB_REG_CASE(OFF,  3, REG, VAL);    \
  95         READ_WB_REG_CASE(OFF,  4, REG, VAL);    \
  96         READ_WB_REG_CASE(OFF,  5, REG, VAL);    \
  97         READ_WB_REG_CASE(OFF,  6, REG, VAL);    \
  98         READ_WB_REG_CASE(OFF,  7, REG, VAL);    \
  99         READ_WB_REG_CASE(OFF,  8, REG, VAL);    \
 100         READ_WB_REG_CASE(OFF,  9, REG, VAL);    \
 101         READ_WB_REG_CASE(OFF, 10, REG, VAL);    \
 102         READ_WB_REG_CASE(OFF, 11, REG, VAL);    \
 103         READ_WB_REG_CASE(OFF, 12, REG, VAL);    \
 104         READ_WB_REG_CASE(OFF, 13, REG, VAL);    \
 105         READ_WB_REG_CASE(OFF, 14, REG, VAL);    \
 106         READ_WB_REG_CASE(OFF, 15, REG, VAL)
 107
 108 #define GEN_WRITE_WB_REG_CASES(OFF, REG, VAL)   \
 109         WRITE_WB_REG_CASE(OFF,  0, REG, VAL);   \
 110         WRITE_WB_REG_CASE(OFF,  1, REG, VAL);   \
 111         WRITE_WB_REG_CASE(OFF,  2, REG, VAL);   \
 112         WRITE_WB_REG_CASE(OFF,  3, REG, VAL);   \
 113         WRITE_WB_REG_CASE(OFF,  4, REG, VAL);   \
 114         WRITE_WB_REG_CASE(OFF,  5, REG, VAL);   \
 115         WRITE_WB_REG_CASE(OFF,  6, REG, VAL);   \
 116         WRITE_WB_REG_CASE(OFF,  7, REG, VAL);   \
 117         WRITE_WB_REG_CASE(OFF,  8, REG, VAL);   \
 118         WRITE_WB_REG_CASE(OFF,  9, REG, VAL);   \
 119         WRITE_WB_REG_CASE(OFF, 10, REG, VAL);   \
 120         WRITE_WB_REG_CASE(OFF, 11, REG, VAL);   \
 121         WRITE_WB_REG_CASE(OFF, 12, REG, VAL);   \
 122         WRITE_WB_REG_CASE(OFF, 13, REG, VAL);   \
 123         WRITE_WB_REG_CASE(OFF, 14, REG, VAL);   \
 124         WRITE_WB_REG_CASE(OFF, 15, REG, VAL)
 125
 126 static u64 read_wb_reg(int reg, int n)
 127 {
 128         u64 val = 0;
 129
 130         switch (reg + n) {
 131         GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
 132         GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
 133         GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
 134         GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
 135         default:
 136                 pr_warning("attempt to read from unknown breakpoint register %d\n", n);
 137         }
 138
 139         return val;
 140 }
 141
 142 static void write_wb_reg(int reg, int n, u64 val)
 143 {
 144         switch (reg + n) {
 145         GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
 146         GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
 147         GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
 148         GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
 149         default:
 150                 pr_warning("attempt to write to unknown breakpoint register %d\n", n);
 151         }
 152         isb();
 153 }
 154
 155 /*
 156  * Convert a breakpoint privilege level to the corresponding exception
 157  * level.
 158  */
 159 static enum debug_el debug_exception_level(int privilege)
 160 {
 161         switch (privilege) {
 162         case AARCH64_BREAKPOINT_EL0:
 163                 return DBG_ACTIVE_EL0;
 164         case AARCH64_BREAKPOINT_EL1:
 165                 return DBG_ACTIVE_EL1;
 166         default:
 167                 pr_warning("invalid breakpoint privilege level %d\n", privilege);
 168                 return -EINVAL;
 169         }
 170 }
 171
 172 /*
 173  * Install a perf counter breakpoint.
 174  */
 175 int arch_install_hw_breakpoint(struct perf_event *bp)
 176 {
 177         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 178         struct perf_event **slot, **slots;
 179         struct debug_info *debug_info = &current->thread.debug;
 180         int i, max_slots, ctrl_reg, val_reg, reg_enable;
 181         u32 ctrl;
 182
 183         if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 184                 /* Breakpoint */
 185                 ctrl_reg = AARCH64_DBG_REG_BCR;
 186                 val_reg = AARCH64_DBG_REG_BVR;
 187                 slots = this_cpu_ptr(bp_on_reg);
 188                 max_slots = core_num_brps;
 189                 reg_enable = !debug_info->bps_disabled;
 190         } else {
 191                 /* Watchpoint */
 192                 ctrl_reg = AARCH64_DBG_REG_WCR;
 193                 val_reg = AARCH64_DBG_REG_WVR;
 194                 slots = this_cpu_ptr(wp_on_reg);
 195                 max_slots = core_num_wrps;
 196                 reg_enable = !debug_info->wps_disabled;
 197         }
 198
 199         for (i = 0; i < max_slots; ++i) {
 200                 slot = &slots[i];
 201
 202                 if (!*slot) {
 203                         *slot = bp;
 204                         break;
 205                 }
 206         }
 207
 208         if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot"))
 209                 return -ENOSPC;
 210
 211         /* Ensure debug monitors are enabled at the correct exception level.  */
 212         enable_debug_monitors(debug_exception_level(info->ctrl.privilege));
 213
 214         /* Setup the address register. */
 215         write_wb_reg(val_reg, i, info->address);
 216
 217         /* Setup the control register. */
 218         ctrl = encode_ctrl_reg(info->ctrl);
 219         write_wb_reg(ctrl_reg, i, reg_enable ? ctrl | 0x1 : ctrl & ~0x1);
 220
 221         return 0;
 222 }
 223
 224 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 225 {
 226         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 227         struct perf_event **slot, **slots;
 228         int i, max_slots, base;
 229
 230         if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 231                 /* Breakpoint */
 232                 base = AARCH64_DBG_REG_BCR;
 233                 slots = this_cpu_ptr(bp_on_reg);
 234                 max_slots = core_num_brps;
 235         } else {
 236                 /* Watchpoint */
 237                 base = AARCH64_DBG_REG_WCR;
 238                 slots = this_cpu_ptr(wp_on_reg);
 239                 max_slots = core_num_wrps;
 240         }
 241
 242         /* Remove the breakpoint. */
 243         for (i = 0; i < max_slots; ++i) {
 244                 slot = &slots[i];
 245
 246                 if (*slot == bp) {
 247                         *slot = NULL;
 248                         break;
 249                 }
 250         }
 251
 252         if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot"))
 253                 return;
 254
 255         /* Reset the control register. */
 256         write_wb_reg(base, i, 0);
 257
 258         /* Release the debug monitors for the correct exception level.  */
 259         disable_debug_monitors(debug_exception_level(info->ctrl.privilege));
 260 }
 261
 262 static int get_hbp_len(u8 hbp_len)
 263 {
 264         unsigned int len_in_bytes = 0;
 265
 266         switch (hbp_len) {
 267         case ARM_BREAKPOINT_LEN_1:
 268                 len_in_bytes = 1;
 269                 break;
 270         case ARM_BREAKPOINT_LEN_2:
 271                 len_in_bytes = 2;
 272                 break;
 273         case ARM_BREAKPOINT_LEN_4:
 274                 len_in_bytes = 4;
 275                 break;
 276         case ARM_BREAKPOINT_LEN_8:
 277                 len_in_bytes = 8;
 278                 break;
 279         }
 280
 281         return len_in_bytes;
 282 }
 283
 284 /*
 285  * Check whether bp virtual address is in kernel space.
 286  */
 287 int arch_check_bp_in_kernelspace(struct perf_event *bp)
 288 {
 289         unsigned int len;
 290         unsigned long va;
 291         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 292
 293         va = info->address;
 294         len = get_hbp_len(info->ctrl.len);
 295
 296         return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
 297 }
 298
 299 /*
 300  * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
 301  * Hopefully this will disappear when ptrace can bypass the conversion
 302  * to generic breakpoint descriptions.
 303  */
 304 int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
 305                            int *gen_len, int *gen_type)
 306 {
 307         /* Type */
 308         switch (ctrl.type) {
 309         case ARM_BREAKPOINT_EXECUTE:
 310                 *gen_type = HW_BREAKPOINT_X;
 311                 break;
 312         case ARM_BREAKPOINT_LOAD:
 313                 *gen_type = HW_BREAKPOINT_R;
 314                 break;
 315         case ARM_BREAKPOINT_STORE:
 316                 *gen_type = HW_BREAKPOINT_W;
 317                 break;
 318         case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
 319                 *gen_type = HW_BREAKPOINT_RW;
 320                 break;
 321         default:
 322                 return -EINVAL;
 323         }
 324
 325         /* Len */
 326         switch (ctrl.len) {
 327         case ARM_BREAKPOINT_LEN_1:
 328                 *gen_len = HW_BREAKPOINT_LEN_1;
 329                 break;
 330         case ARM_BREAKPOINT_LEN_2:
 331                 *gen_len = HW_BREAKPOINT_LEN_2;
 332                 break;
 333         case ARM_BREAKPOINT_LEN_4:
 334                 *gen_len = HW_BREAKPOINT_LEN_4;
 335                 break;
 336         case ARM_BREAKPOINT_LEN_8:
 337                 *gen_len = HW_BREAKPOINT_LEN_8;
 338                 break;
 339         default:
 340                 return -EINVAL;
 341         }
 342
 343         return 0;
 344 }
 345
 346 /*
 347  * Construct an arch_hw_breakpoint from a perf_event.
 348  */
 349 static int arch_build_bp_info(struct perf_event *bp)
 350 {
 351         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 352
 353         /* Type */
 354         switch (bp->attr.bp_type) {
 355         case HW_BREAKPOINT_X:
 356                 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
 357                 break;
 358         case HW_BREAKPOINT_R:
 359                 info->ctrl.type = ARM_BREAKPOINT_LOAD;
 360                 break;
 361         case HW_BREAKPOINT_W:
 362                 info->ctrl.type = ARM_BREAKPOINT_STORE;
 363                 break;
 364         case HW_BREAKPOINT_RW:
 365                 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
 366                 break;
 367         default:
 368                 return -EINVAL;
 369         }
 370
 371         /* Len */
 372         switch (bp->attr.bp_len) {
 373         case HW_BREAKPOINT_LEN_1:
 374                 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
 375                 break;
 376         case HW_BREAKPOINT_LEN_2:
 377                 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
 378                 break;
 379         case HW_BREAKPOINT_LEN_4:
 380                 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
 381                 break;
 382         case HW_BREAKPOINT_LEN_8:
 383                 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
 384                 break;
 385         default:
 386                 return -EINVAL;
 387         }
 388
 389         /*
 390          * On AArch64, we only permit breakpoints of length 4, whereas
 391          * AArch32 also requires breakpoints of length 2 for Thumb.
 392          * Watchpoints can be of length 1, 2, 4 or 8 bytes.
 393          */
 394         if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 395                 if (is_compat_task()) {
 396                         if (info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
 397                             info->ctrl.len != ARM_BREAKPOINT_LEN_4)
 398                                 return -EINVAL;
 399                 } else if (info->ctrl.len != ARM_BREAKPOINT_LEN_4) {
 400                         /*
 401                          * FIXME: Some tools (I'm looking at you perf) assume
 402                          *        that breakpoints should be sizeof(long). This
 403                          *        is nonsense. For now, we fix up the parameter
 404                          *        but we should probably return -EINVAL instead.
 405                          */
 406                         info->ctrl.len = ARM_BREAKPOINT_LEN_4;
 407                 }
 408         }
 409
 410         /* Address */
 411         info->address = bp->attr.bp_addr;
 412
 413         /*
 414          * Privilege
 415          * Note that we disallow combined EL0/EL1 breakpoints because
 416          * that would complicate the stepping code.
 417          */
 418         if (arch_check_bp_in_kernelspace(bp))
 419                 info->ctrl.privilege = AARCH64_BREAKPOINT_EL1;
 420         else
 421                 info->ctrl.privilege = AARCH64_BREAKPOINT_EL0;
 422
 423         /* Enabled? */
 424         info->ctrl.enabled = !bp->attr.disabled;
 425
 426         return 0;
 427 }
 428
 429 /*
 430  * Validate the arch-specific HW Breakpoint register settings.
 431  */
 432 int arch_validate_hwbkpt_settings(struct perf_event *bp)
 433 {
 434         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 435         int ret;
 436         u64 alignment_mask, offset;
 437
 438         /* Build the arch_hw_breakpoint. */
 439         ret = arch_build_bp_info(bp);
 440         if (ret)
 441                 return ret;
 442
 443         /*
 444          * Check address alignment.
 445          * We don't do any clever alignment correction for watchpoints
 446          * because using 64-bit unaligned addresses is deprecated for
 447          * AArch64.
 448          *
 449          * AArch32 tasks expect some simple alignment fixups, so emulate
 450          * that here.
 451          */
 452         if (is_compat_task()) {
 453                 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
 454                         alignment_mask = 0x7;
 455                 else
 456                         alignment_mask = 0x3;
 457                 offset = info->address & alignment_mask;
 458                 switch (offset) {
 459                 case 0:
 460                         /* Aligned */
 461                         break;
 462                 case 1:
 463                         /* Allow single byte watchpoint. */
 464                         if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
 465                                 break;
 466                 case 2:
 467                         /* Allow halfword watchpoints and breakpoints. */
 468                         if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
 469                                 break;
 470                 default:
 471                         return -EINVAL;
 472                 }
 473
 474                 info->address &= ~alignment_mask;
 475                 info->ctrl.len <<= offset;
 476         } else {
 477                 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE)
 478                         alignment_mask = 0x3;
 479                 else
 480                         alignment_mask = 0x7;
 481                 if (info->address & alignment_mask)
 482                         return -EINVAL;
 483         }
 484
 485         /*
 486          * Disallow per-task kernel breakpoints since these would
 487          * complicate the stepping code.
 488          */
 489         if (info->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.bp_target)
 490                 return -EINVAL;
 491
 492         return 0;
 493 }
 494
 495 /*
 496  * Enable/disable all of the breakpoints active at the specified
 497  * exception level at the register level.
 498  * This is used when single-stepping after a breakpoint exception.
 499  */
 500 static void toggle_bp_registers(int reg, enum debug_el el, int enable)
 501 {
 502         int i, max_slots, privilege;
 503         u32 ctrl;
 504         struct perf_event **slots;
 505
 506         switch (reg) {
 507         case AARCH64_DBG_REG_BCR:
 508                 slots = this_cpu_ptr(bp_on_reg);
 509                 max_slots = core_num_brps;
 510                 break;
 511         case AARCH64_DBG_REG_WCR:
 512                 slots = this_cpu_ptr(wp_on_reg);
 513                 max_slots = core_num_wrps;
 514                 break;
 515         default:
 516                 return;
 517         }
 518
 519         for (i = 0; i < max_slots; ++i) {
 520                 if (!slots[i])
 521                         continue;
 522
 523                 privilege = counter_arch_bp(slots[i])->ctrl.privilege;
 524                 if (debug_exception_level(privilege) != el)
 525                         continue;
 526
 527                 ctrl = read_wb_reg(reg, i);
 528                 if (enable)
 529                         ctrl |= 0x1;
 530                 else
 531                         ctrl &= ~0x1;
 532                 write_wb_reg(reg, i, ctrl);
 533         }
 534 }
 535
 536 /*
 537  * Debug exception handlers.
 538  */
 539 static int breakpoint_handler(unsigned long unused, unsigned int esr,
 540                               struct pt_regs *regs)
 541 {
 542         int i, step = 0, *kernel_step;
 543         u32 ctrl_reg;
 544         u64 addr, val;
 545         struct perf_event *bp, **slots;
 546         struct debug_info *debug_info;
 547         struct arch_hw_breakpoint_ctrl ctrl;
 548
 549         slots = this_cpu_ptr(bp_on_reg);
 550         addr = instruction_pointer(regs);
 551         debug_info = &current->thread.debug;
 552
 553         for (i = 0; i < core_num_brps; ++i) {
 554                 rcu_read_lock();
 555
 556                 bp = slots[i];
 557
 558                 if (bp == NULL)
 559                         goto unlock;
 560
 561                 /* Check if the breakpoint value matches. */
 562                 val = read_wb_reg(AARCH64_DBG_REG_BVR, i);
 563                 if (val != (addr & ~0x3))
 564                         goto unlock;
 565
 566                 /* Possible match, check the byte address select to confirm. */
 567                 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_BCR, i);
 568                 decode_ctrl_reg(ctrl_reg, &ctrl);
 569                 if (!((1 << (addr & 0x3)) & ctrl.len))
 570                         goto unlock;
 571
 572                 counter_arch_bp(bp)->trigger = addr;
 573                 perf_bp_event(bp, regs);
 574
 575                 /* Do we need to handle the stepping? */
 576                 if (!bp->overflow_handler)
 577                         step = 1;
 578 unlock:
 579                 rcu_read_unlock();
 580         }
 581
 582         if (!step)
 583                 return 0;
 584
 585         if (user_mode(regs)) {
 586                 debug_info->bps_disabled = 1;
 587                 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 0);
 588
 589                 /* If we're already stepping a watchpoint, just return. */
 590                 if (debug_info->wps_disabled)
 591                         return 0;
 592
 593                 if (test_thread_flag(TIF_SINGLESTEP))
 594                         debug_info->suspended_step = 1;
 595                 else
 596                         user_enable_single_step(current);
 597         } else {
 598                 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 0);
 599                 kernel_step = this_cpu_ptr(&stepping_kernel_bp);
 600
 601                 if (*kernel_step != ARM_KERNEL_STEP_NONE)
 602                         return 0;
 603
 604                 if (kernel_active_single_step()) {
 605                         *kernel_step = ARM_KERNEL_STEP_SUSPEND;
 606                 } else {
 607                         *kernel_step = ARM_KERNEL_STEP_ACTIVE;
 608                         kernel_enable_single_step(regs);
 609                 }
 610         }
 611
 612         return 0;
 613 }
 614
 615 static int watchpoint_handler(unsigned long addr, unsigned int esr,
 616                               struct pt_regs *regs)
 617 {
 618         int i, step = 0, *kernel_step, access;
 619         u32 ctrl_reg;
 620         u64 val, alignment_mask;
 621         struct perf_event *wp, **slots;
 622         struct debug_info *debug_info;
 623         struct arch_hw_breakpoint *info;
 624         struct arch_hw_breakpoint_ctrl ctrl;
 625
 626         slots = this_cpu_ptr(wp_on_reg);
 627         debug_info = &current->thread.debug;
 628
 629         for (i = 0; i < core_num_wrps; ++i) {
 630                 rcu_read_lock();
 631
 632                 wp = slots[i];
 633
 634                 if (wp == NULL)
 635                         goto unlock;
 636
 637                 info = counter_arch_bp(wp);
 638                 /* AArch32 watchpoints are either 4 or 8 bytes aligned. */
 639                 if (is_compat_task()) {
 640                         if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
 641                                 alignment_mask = 0x7;
 642                         else
 643                                 alignment_mask = 0x3;
 644                 } else {
 645                         alignment_mask = 0x7;
 646                 }
 647
 648                 /* Check if the watchpoint value matches. */
 649                 val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
 650                 if (val != (addr & ~alignment_mask))
 651                         goto unlock;
 652
 653                 /* Possible match, check the byte address select to confirm. */
 654                 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i);
 655                 decode_ctrl_reg(ctrl_reg, &ctrl);
 656                 if (!((1 << (addr & alignment_mask)) & ctrl.len))
 657                         goto unlock;
 658
 659                 /*
 660                  * Check that the access type matches.
 661                  * 0 => load, otherwise => store
 662                  */
 663                 access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W :
 664                          HW_BREAKPOINT_R;
 665                 if (!(access & hw_breakpoint_type(wp)))
 666                         goto unlock;
 667
 668                 info->trigger = addr;
 669                 perf_bp_event(wp, regs);
 670
 671                 /* Do we need to handle the stepping? */
 672                 if (!wp->overflow_handler)
 673                         step = 1;
 674
 675 unlock:
 676                 rcu_read_unlock();
 677         }
 678
 679         if (!step)
 680                 return 0;
 681
 682         /*
 683          * We always disable EL0 watchpoints because the kernel can
 684          * cause these to fire via an unprivileged access.
 685          */
 686         toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 0);
 687
 688         if (user_mode(regs)) {
 689                 debug_info->wps_disabled = 1;
 690
 691                 /* If we're already stepping a breakpoint, just return. */
 692                 if (debug_info->bps_disabled)
 693                         return 0;
 694
 695                 if (test_thread_flag(TIF_SINGLESTEP))
 696                         debug_info->suspended_step = 1;
 697                 else
 698                         user_enable_single_step(current);
 699         } else {
 700                 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 0);
 701                 kernel_step = this_cpu_ptr(&stepping_kernel_bp);
 702
 703                 if (*kernel_step != ARM_KERNEL_STEP_NONE)
 704                         return 0;
 705
 706                 if (kernel_active_single_step()) {
 707                         *kernel_step = ARM_KERNEL_STEP_SUSPEND;
 708                 } else {
 709                         *kernel_step = ARM_KERNEL_STEP_ACTIVE;
 710                         kernel_enable_single_step(regs);
 711                 }
 712         }
 713
 714         return 0;
 715 }
 716
 717 /*
 718  * Handle single-step exception.
 719  */
 720 int reinstall_suspended_bps(struct pt_regs *regs)
 721 {
 722         struct debug_info *debug_info = &current->thread.debug;
 723         int handled_exception = 0, *kernel_step;
 724
 725         kernel_step = this_cpu_ptr(&stepping_kernel_bp);
 726
 727         /*
 728          * Called from single-step exception handler.
 729          * Return 0 if execution can resume, 1 if a SIGTRAP should be
 730          * reported.
 731          */
 732         if (user_mode(regs)) {
 733                 if (debug_info->bps_disabled) {
 734                         debug_info->bps_disabled = 0;
 735                         toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 1);
 736                         handled_exception = 1;
 737                 }
 738
 739                 if (debug_info->wps_disabled) {
 740                         debug_info->wps_disabled = 0;
 741                         toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
 742                         handled_exception = 1;
 743                 }
 744
 745                 if (handled_exception) {
 746                         if (debug_info->suspended_step) {
 747                                 debug_info->suspended_step = 0;
 748                                 /* Allow exception handling to fall-through. */
 749                                 handled_exception = 0;
 750                         } else {
 751                                 user_disable_single_step(current);
 752                         }
 753                 }
 754         } else if (*kernel_step != ARM_KERNEL_STEP_NONE) {
 755                 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 1);
 756                 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 1);
 757
 758                 if (!debug_info->wps_disabled)
 759                         toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
 760
 761                 if (*kernel_step != ARM_KERNEL_STEP_SUSPEND) {
 762                         kernel_disable_single_step();
 763                         handled_exception = 1;
 764                 } else {
 765                         handled_exception = 0;
 766                 }
 767
 768                 *kernel_step = ARM_KERNEL_STEP_NONE;
 769         }
 770
 771         return !handled_exception;
 772 }
 773
 774 /*
 775  * Context-switcher for restoring suspended breakpoints.
 776  */
 777 void hw_breakpoint_thread_switch(struct task_struct *next)
 778 {
 779         /*
 780          *           current        next
 781          * disabled: 0              0     => The usual case, NOTIFY_DONE
 782          *           0              1     => Disable the registers
 783          *           1              0     => Enable the registers
 784          *           1              1     => NOTIFY_DONE. per-task bps will
 785          *                                   get taken care of by perf.
 786          */
 787
 788         struct debug_info *current_debug_info, *next_debug_info;
 789
 790         current_debug_info = &current->thread.debug;
 791         next_debug_info = &next->thread.debug;
 792
 793         /* Update breakpoints. */
 794         if (current_debug_info->bps_disabled != next_debug_info->bps_disabled)
 795                 toggle_bp_registers(AARCH64_DBG_REG_BCR,
 796                                     DBG_ACTIVE_EL0,
 797                                     !next_debug_info->bps_disabled);
 798
 799         /* Update watchpoints. */
 800         if (current_debug_info->wps_disabled != next_debug_info->wps_disabled)
 801                 toggle_bp_registers(AARCH64_DBG_REG_WCR,
 802                                     DBG_ACTIVE_EL0,
 803                                     !next_debug_info->wps_disabled);
 804 }
 805
 806 /*
 807  * CPU initialisation.
 808  */
 809 static void reset_ctrl_regs(void *unused)
 810 {
 811         int i;
 812
 813         for (i = 0; i < core_num_brps; ++i) {
 814                 write_wb_reg(AARCH64_DBG_REG_BCR, i, 0UL);
 815                 write_wb_reg(AARCH64_DBG_REG_BVR, i, 0UL);
 816         }
 817
 818         for (i = 0; i < core_num_wrps; ++i) {
 819                 write_wb_reg(AARCH64_DBG_REG_WCR, i, 0UL);
 820                 write_wb_reg(AARCH64_DBG_REG_WVR, i, 0UL);
 821         }
 822 }
 823
 824 static int hw_breakpoint_reset_notify(struct notifier_block *self,
 825                                                 unsigned long action,
 826                                                 void *hcpu)
 827 {
 828         int cpu = (long)hcpu;
 829         if (action == CPU_ONLINE)
 830                 smp_call_function_single(cpu, reset_ctrl_regs, NULL, 1);
 831         return NOTIFY_OK;
 832 }
 833
 834 static struct notifier_block hw_breakpoint_reset_nb = {
 835         .notifier_call = hw_breakpoint_reset_notify,
 836 };
 837
 838 /*
 839  * One-time initialisation.
 840  */
 841 static int __init arch_hw_breakpoint_init(void)
 842 {
 843         core_num_brps = get_num_brps();
 844         core_num_wrps = get_num_wrps();
 845
 846         pr_info("found %d breakpoint and %d watchpoint registers.\n",
 847                 core_num_brps, core_num_wrps);
 848
 849         /*
 850          * Reset the breakpoint resources. We assume that a halting
 851          * debugger will leave the world in a nice state for us.
 852          */
 853         smp_call_function(reset_ctrl_regs, NULL, 1);
 854         reset_ctrl_regs(NULL);
 855
 856         /* Register debug fault handlers. */
 857         hook_debug_fault_code(DBG_ESR_EVT_HWBP, breakpoint_handler, SIGTRAP,
 858                               TRAP_HWBKPT, "hw-breakpoint handler");
 859         hook_debug_fault_code(DBG_ESR_EVT_HWWP, watchpoint_handler, SIGTRAP,
 860                               TRAP_HWBKPT, "hw-watchpoint handler");
 861
 862         /* Register hotplug notifier. */
 863         register_cpu_notifier(&hw_breakpoint_reset_nb);
 864
 865         return 0;
 866 }
 867 arch_initcall(arch_hw_breakpoint_init);
 868
 869 void hw_breakpoint_pmu_read(struct perf_event *bp)
 870 {
 871 }
 872
 873 /*
 874  * Dummy function to register with die_notifier.
 875  */
 876 int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
 877                                     unsigned long val, void *data)
 878 {
 879         return NOTIFY_DONE;
 880 }