arch/arm64/kernel/hw

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

DEFINITIONS
