sys/amd64/amd64/db_trace.c

   1 /*-
   2  * Mach Operating System
   3  * Copyright (c) 1991,1990 Carnegie Mellon University
   4  * All Rights Reserved.
   5  *
   6  * Permission to use, copy, modify and distribute this software and its
   7  * documentation is hereby granted, provided that both the copyright
   8  * notice and this permission notice appear in all copies of the
   9  * software, derivative works or modified versions, and any portions
  10  * thereof, and that both notices appear in supporting documentation.
  11  *
  12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
  13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  15  *
  16  * Carnegie Mellon requests users of this software to return to
  17  *
  18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  19  *  School of Computer Science
  20  *  Carnegie Mellon University
  21  *  Pittsburgh PA 15213-3890
  22  *
  23  * any improvements or extensions that they make and grant Carnegie the
  24  * rights to redistribute these changes.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 #include "opt_compat.h"
  31
  32 #include <sys/param.h>
  33 #include <sys/systm.h>
  34 #include <sys/kdb.h>
  35 #include <sys/proc.h>
  36 #include <sys/smp.h>
  37 #include <sys/stack.h>
  38 #include <sys/sysent.h>
  39
  40 #include <machine/cpu.h>
  41 #include <machine/md_var.h>
  42 #include <machine/pcb.h>
  43 #include <machine/reg.h>
  44 #include <machine/stack.h>
  45
  46 #include <vm/vm.h>
  47 #include <vm/vm_param.h>
  48 #include <vm/pmap.h>
  49
  50 #include <ddb/ddb.h>
  51 #include <ddb/db_access.h>
  52 #include <ddb/db_sym.h>
  53 #include <ddb/db_variables.h>
  54
  55 static db_varfcn_t db_dr0;
  56 static db_varfcn_t db_dr1;
  57 static db_varfcn_t db_dr2;
  58 static db_varfcn_t db_dr3;
  59 static db_varfcn_t db_dr4;
  60 static db_varfcn_t db_dr5;
  61 static db_varfcn_t db_dr6;
  62 static db_varfcn_t db_dr7;
  63 static db_varfcn_t db_frame;
  64
  65 CTASSERT(sizeof(struct dbreg) == sizeof(((struct pcpu *)NULL)->pc_dbreg));
  66
  67 /*
  68  * Machine register set.
  69  */
  70 #define DB_OFFSET(x)    (db_expr_t *)offsetof(struct trapframe, x)
  71 struct db_variable db_regs[] = {
  72         { "cs",         DB_OFFSET(tf_cs),       db_frame },
  73         { "ds",         DB_OFFSET(tf_ds),       db_frame },
  74         { "es",         DB_OFFSET(tf_es),       db_frame },
  75         { "fs",         DB_OFFSET(tf_fs),       db_frame },
  76         { "gs",         DB_OFFSET(tf_gs),       db_frame },
  77         { "ss",         DB_OFFSET(tf_ss),       db_frame },
  78         { "rax",        DB_OFFSET(tf_rax),      db_frame },
  79         { "rcx",        DB_OFFSET(tf_rcx),      db_frame },
  80         { "rdx",        DB_OFFSET(tf_rdx),      db_frame },
  81         { "rbx",        DB_OFFSET(tf_rbx),      db_frame },
  82         { "rsp",        DB_OFFSET(tf_rsp),      db_frame },
  83         { "rbp",        DB_OFFSET(tf_rbp),      db_frame },
  84         { "rsi",        DB_OFFSET(tf_rsi),      db_frame },
  85         { "rdi",        DB_OFFSET(tf_rdi),      db_frame },
  86         { "r8",         DB_OFFSET(tf_r8),       db_frame },
  87         { "r9",         DB_OFFSET(tf_r9),       db_frame },
  88         { "r10",        DB_OFFSET(tf_r10),      db_frame },
  89         { "r11",        DB_OFFSET(tf_r11),      db_frame },
  90         { "r12",        DB_OFFSET(tf_r12),      db_frame },
  91         { "r13",        DB_OFFSET(tf_r13),      db_frame },
  92         { "r14",        DB_OFFSET(tf_r14),      db_frame },
  93         { "r15",        DB_OFFSET(tf_r15),      db_frame },
  94         { "rip",        DB_OFFSET(tf_rip),      db_frame },
  95         { "rflags",     DB_OFFSET(tf_rflags),   db_frame },
  96 #define DB_N_SHOW_REGS  24      /* Don't show registers after here. */
  97         { "dr0",        NULL,                   db_dr0 },
  98         { "dr1",        NULL,                   db_dr1 },
  99         { "dr2",        NULL,                   db_dr2 },
 100         { "dr3",        NULL,                   db_dr3 },
 101         { "dr4",        NULL,                   db_dr4 },
 102         { "dr5",        NULL,                   db_dr5 },
 103         { "dr6",        NULL,                   db_dr6 },
 104         { "dr7",        NULL,                   db_dr7 },
 105 };
 106 struct db_variable *db_eregs = db_regs + DB_N_SHOW_REGS;
 107
 108 #define DB_DRX_FUNC(reg)                \
 109 static int                              \
 110 db_ ## reg (vp, valuep, op)             \
 111         struct db_variable *vp;         \
 112         db_expr_t * valuep;             \
 113         int op;                         \
 114 {                                       \
 115         if (op == DB_VAR_GET)           \
 116                 *valuep = r ## reg ();  \
 117         else                            \
 118                 load_ ## reg (*valuep); \
 119         return (1);                     \
 120 }
 121
 122 DB_DRX_FUNC(dr0)
 123 DB_DRX_FUNC(dr1)
 124 DB_DRX_FUNC(dr2)
 125 DB_DRX_FUNC(dr3)
 126 DB_DRX_FUNC(dr4)
 127 DB_DRX_FUNC(dr5)
 128 DB_DRX_FUNC(dr6)
 129 DB_DRX_FUNC(dr7)
 130
 131 static int
 132 db_frame(struct db_variable *vp, db_expr_t *valuep, int op)
 133 {
 134         long *reg;
 135
 136         if (kdb_frame == NULL)
 137                 return (0);
 138
 139         reg = (long *)((uintptr_t)kdb_frame + (db_expr_t)vp->valuep);
 140         if (op == DB_VAR_GET)
 141                 *valuep = *reg;
 142         else
 143                 *reg = *valuep;
 144         return (1);
 145 }
 146
 147 #define NORMAL          0
 148 #define TRAP            1
 149 #define INTERRUPT       2
 150 #define SYSCALL         3
 151 #define TRAP_INTERRUPT  5
 152
 153 static void db_nextframe(struct amd64_frame **, db_addr_t *, struct thread *);
 154 static void db_print_stack_entry(const char *, db_addr_t, void *);
 155 static void decode_syscall(int, struct thread *);
 156
 157 static const char * watchtype_str(int type);
 158 int  amd64_set_watch(int watchnum, unsigned long watchaddr, int size,
 159                     int access, struct dbreg *d);
 160 int  amd64_clr_watch(int watchnum, struct dbreg *d);
 161
 162 static void
 163 db_print_stack_entry(const char *name, db_addr_t callpc, void *frame)
 164 {
 165
 166         db_printf("%s() at ", name != NULL ? name : "??");
 167         db_printsym(callpc, DB_STGY_PROC);
 168         if (frame != NULL)
 169                 db_printf("/frame 0x%lx", (register_t)frame);
 170         db_printf("\n");
 171 }
 172
 173 static void
 174 decode_syscall(int number, struct thread *td)
 175 {
 176         struct proc *p;
 177         c_db_sym_t sym;
 178         db_expr_t diff;
 179         sy_call_t *f;
 180         const char *symname;
 181
 182         db_printf(" (%d", number);
 183         p = (td != NULL) ? td->td_proc : NULL;
 184         if (p != NULL && 0 <= number && number < p->p_sysent->sv_size) {
 185                 f = p->p_sysent->sv_table[number].sy_call;
 186                 sym = db_search_symbol((db_addr_t)f, DB_STGY_ANY, &diff);
 187                 if (sym != DB_SYM_NULL && diff == 0) {
 188                         db_symbol_values(sym, &symname, NULL);
 189                         db_printf(", %s, %s", p->p_sysent->sv_name, symname);
 190                 }
 191         }
 192         db_printf(")");
 193 }
 194
 195 /*
 196  * Figure out the next frame up in the call stack.
 197  */
 198 static void
 199 db_nextframe(struct amd64_frame **fp, db_addr_t *ip, struct thread *td)
 200 {
 201         struct trapframe *tf;
 202         int frame_type;
 203         long rip, rsp, rbp;
 204         db_expr_t offset;
 205         c_db_sym_t sym;
 206         const char *name;
 207
 208         rip = db_get_value((long) &(*fp)->f_retaddr, 8, FALSE);
 209         rbp = db_get_value((long) &(*fp)->f_frame, 8, FALSE);
 210
 211         /*
 212          * Figure out frame type.  We look at the address just before
 213          * the saved instruction pointer as the saved EIP is after the
 214          * call function, and if the function being called is marked as
 215          * dead (such as panic() at the end of dblfault_handler()), then
 216          * the instruction at the saved EIP will be part of a different
 217          * function (syscall() in this example) rather than the one that
 218          * actually made the call.
 219          */
 220         frame_type = NORMAL;
 221         sym = db_search_symbol(rip - 1, DB_STGY_ANY, &offset);
 222         db_symbol_values(sym, &name, NULL);
 223         if (name != NULL) {
 224                 if (strcmp(name, "calltrap") == 0 ||
 225                     strcmp(name, "fork_trampoline") == 0 ||
 226                     strcmp(name, "nmi_calltrap") == 0 ||
 227                     strcmp(name, "Xdblfault") == 0)
 228                         frame_type = TRAP;
 229                 else if (strncmp(name, "Xatpic_intr", 11) == 0 ||
 230                     strncmp(name, "Xapic_isr", 9) == 0 ||
 231                     strcmp(name, "Xtimerint") == 0 ||
 232                     strcmp(name, "Xipi_intr_bitmap_handler") == 0 ||
 233                     strcmp(name, "Xcpustop") == 0 ||
 234                     strcmp(name, "Xcpususpend") == 0 ||
 235                     strcmp(name, "Xrendezvous") == 0)
 236                         frame_type = INTERRUPT;
 237                 else if (strcmp(name, "Xfast_syscall") == 0)
 238                         frame_type = SYSCALL;
 239 #ifdef COMPAT_FREEBSD32
 240                 else if (strcmp(name, "Xint0x80_syscall") == 0)
 241                         frame_type = SYSCALL;
 242 #endif
 243                 /* XXX: These are interrupts with trap frames. */
 244                 else if (strcmp(name, "Xtimerint") == 0 ||
 245                     strcmp(name, "Xcpustop") == 0 ||
 246                     strcmp(name, "Xcpususpend") == 0 ||
 247                     strcmp(name, "Xrendezvous") == 0 ||
 248                     strcmp(name, "Xipi_intr_bitmap_handler") == 0)
 249                         frame_type = TRAP_INTERRUPT;
 250         }
 251
 252         /*
 253          * Normal frames need no special processing.
 254          */
 255         if (frame_type == NORMAL) {
 256                 *ip = (db_addr_t) rip;
 257                 *fp = (struct amd64_frame *) rbp;
 258                 return;
 259         }
 260
 261         db_print_stack_entry(name, rip, &(*fp)->f_frame);
 262
 263         /*
 264          * Point to base of trapframe which is just above the
 265          * current frame.
 266          */
 267         tf = (struct trapframe *)((long)*fp + 16);
 268
 269         if (INKERNEL((long) tf)) {
 270                 rsp = tf->tf_rsp;
 271                 rip = tf->tf_rip;
 272                 rbp = tf->tf_rbp;
 273                 switch (frame_type) {
 274                 case TRAP:
 275                         db_printf("--- trap %#r", tf->tf_trapno);
 276                         break;
 277                 case SYSCALL:
 278                         db_printf("--- syscall");
 279                         decode_syscall(tf->tf_rax, td);
 280                         break;
 281                 case TRAP_INTERRUPT:
 282                 case INTERRUPT:
 283                         db_printf("--- interrupt");
 284                         break;
 285                 default:
 286                         panic("The moon has moved again.");
 287                 }
 288                 db_printf(", rip = %#lr, rsp = %#lr, rbp = %#lr ---\n", rip,
 289                     rsp, rbp);
 290         }
 291
 292         *ip = (db_addr_t) rip;
 293         *fp = (struct amd64_frame *) rbp;
 294 }
 295
 296 static int
 297 db_backtrace(struct thread *td, struct trapframe *tf, struct amd64_frame *frame,
 298     db_addr_t pc, register_t sp, int count)
 299 {
 300         struct amd64_frame *actframe;
 301         const char *name;
 302         db_expr_t offset;
 303         c_db_sym_t sym;
 304         boolean_t first;
 305
 306         if (count == -1)
 307                 count = 1024;
 308
 309         first = TRUE;
 310         while (count-- && !db_pager_quit) {
 311                 sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
 312                 db_symbol_values(sym, &name, NULL);
 313
 314                 /*
 315                  * Attempt to determine a (possibly fake) frame that gives
 316                  * the caller's pc.  It may differ from `frame' if the
 317                  * current function never sets up a standard frame or hasn't
 318                  * set one up yet or has just discarded one.  The last two
 319                  * cases can be guessed fairly reliably for code generated
 320                  * by gcc.  The first case is too much trouble to handle in
 321                  * general because the amount of junk on the stack depends
 322                  * on the pc (the special handling of "calltrap", etc. in
 323                  * db_nextframe() works because the `next' pc is special).
 324                  */
 325                 actframe = frame;
 326                 if (first) {
 327                         first = FALSE;
 328                         if (sym == C_DB_SYM_NULL && sp != 0) {
 329                                 /*
 330                                  * If a symbol couldn't be found, we've probably
 331                                  * jumped to a bogus location, so try and use
 332                                  * the return address to find our caller.
 333                                  */
 334                                 db_print_stack_entry(name, pc, NULL);
 335                                 pc = db_get_value(sp, 8, FALSE);
 336                                 if (db_search_symbol(pc, DB_STGY_PROC,
 337                                     &offset) == C_DB_SYM_NULL)
 338                                         break;
 339                                 continue;
 340                         } else if (tf != NULL) {
 341                                 int instr;
 342
 343                                 instr = db_get_value(pc, 4, FALSE);
 344                                 if ((instr & 0xffffffff) == 0xe5894855) {
 345                                         /* pushq %rbp; movq %rsp, %rbp */
 346                                         actframe = (void *)(tf->tf_rsp - 8);
 347                                 } else if ((instr & 0xffffff) == 0xe58948) {
 348                                         /* movq %rsp, %rbp */
 349                                         actframe = (void *)tf->tf_rsp;
 350                                         if (tf->tf_rbp == 0) {
 351                                                 /* Fake frame better. */
 352                                                 frame = actframe;
 353                                         }
 354                                 } else if ((instr & 0xff) == 0xc3) {
 355                                         /* ret */
 356                                         actframe = (void *)(tf->tf_rsp - 8);
 357                                 } else if (offset == 0) {
 358                                         /* Probably an assembler symbol. */
 359                                         actframe = (void *)(tf->tf_rsp - 8);
 360                                 }
 361                         } else if (strcmp(name, "fork_trampoline") == 0) {
 362                                 /*
 363                                  * Don't try to walk back on a stack for a
 364                                  * process that hasn't actually been run yet.
 365                                  */
 366                                 db_print_stack_entry(name, pc, actframe);
 367                                 break;
 368                         }
 369                 }
 370
 371                 db_print_stack_entry(name, pc, actframe);
 372
 373                 if (actframe != frame) {
 374                         /* `frame' belongs to caller. */
 375                         pc = (db_addr_t)
 376                             db_get_value((long)&actframe->f_retaddr, 8, FALSE);
 377                         continue;
 378                 }
 379
 380                 db_nextframe(&frame, &pc, td);
 381
 382                 if (INKERNEL((long)pc) && !INKERNEL((long)frame)) {
 383                         sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
 384                         db_symbol_values(sym, &name, NULL);
 385                         db_print_stack_entry(name, pc, frame);
 386                         break;
 387                 }
 388                 if (!INKERNEL((long) frame)) {
 389                         break;
 390                 }
 391         }
 392
 393         return (0);
 394 }
 395
 396 void
 397 db_trace_self(void)
 398 {
 399         struct amd64_frame *frame;
 400         db_addr_t callpc;
 401         register_t rbp;
 402
 403         __asm __volatile("movq %%rbp,%0" : "=r" (rbp));
 404         frame = (struct amd64_frame *)rbp;
 405         callpc = (db_addr_t)db_get_value((long)&frame->f_retaddr, 8, FALSE);
 406         frame = frame->f_frame;
 407         db_backtrace(curthread, NULL, frame, callpc, 0, -1);
 408 }
 409
 410 int
 411 db_trace_thread(struct thread *thr, int count)
 412 {
 413         struct pcb *ctx;
 414         struct trapframe *tf;
 415
 416         ctx = kdb_thr_ctx(thr);
 417         tf = thr == kdb_thread ? kdb_frame : NULL;
 418         return (db_backtrace(thr, tf, (struct amd64_frame *)ctx->pcb_rbp,
 419             ctx->pcb_rip, ctx->pcb_rsp, count));
 420 }
 421
 422 int
 423 amd64_set_watch(watchnum, watchaddr, size, access, d)
 424         int watchnum;
 425         unsigned long watchaddr;
 426         int size;
 427         int access;
 428         struct dbreg *d;
 429 {
 430         int i, len;
 431
 432         if (watchnum == -1) {
 433                 for (i = 0; i < 4; i++)
 434                         if (!DBREG_DR7_ENABLED(d->dr[7], i))
 435                                 break;
 436                 if (i < 4)
 437                         watchnum = i;
 438                 else
 439                         return (-1);
 440         }
 441
 442         switch (access) {
 443         case DBREG_DR7_EXEC:
 444                 size = 1; /* size must be 1 for an execution breakpoint */
 445                 /* fall through */
 446         case DBREG_DR7_WRONLY:
 447         case DBREG_DR7_RDWR:
 448                 break;
 449         default:
 450                 return (-1);
 451         }
 452
 453         /*
 454          * we can watch a 1, 2, 4, or 8 byte sized location
 455          */
 456         switch (size) {
 457         case 1:
 458                 len = DBREG_DR7_LEN_1;
 459                 break;
 460         case 2:
 461                 len = DBREG_DR7_LEN_2;
 462                 break;
 463         case 4:
 464                 len = DBREG_DR7_LEN_4;
 465                 break;
 466         case 8:
 467                 len = DBREG_DR7_LEN_8;
 468                 break;
 469         default:
 470                 return (-1);
 471         }
 472
 473         /* clear the bits we are about to affect */
 474         d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
 475
 476         /* set drN register to the address, N=watchnum */
 477         DBREG_DRX(d, watchnum) = watchaddr;
 478
 479         /* enable the watchpoint */
 480         d->dr[7] |= DBREG_DR7_SET(watchnum, len, access,
 481             DBREG_DR7_GLOBAL_ENABLE);
 482
 483         return (watchnum);
 484 }
 485
 486
 487 int
 488 amd64_clr_watch(watchnum, d)
 489         int watchnum;
 490         struct dbreg *d;
 491 {
 492
 493         if (watchnum < 0 || watchnum >= 4)
 494                 return (-1);
 495
 496         d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
 497         DBREG_DRX(d, watchnum) = 0;
 498
 499         return (0);
 500 }
 501
 502
 503 int
 504 db_md_set_watchpoint(addr, size)
 505         db_expr_t addr;
 506         db_expr_t size;
 507 {
 508         struct dbreg *d;
 509         struct pcpu *pc;
 510         int avail, c, cpu, i, wsize;
 511
 512         d = (struct dbreg *)PCPU_PTR(dbreg);
 513         cpu = PCPU_GET(cpuid);
 514         fill_dbregs(NULL, d);
 515
 516         avail = 0;
 517         for (i = 0; i < 4; i++) {
 518                 if (!DBREG_DR7_ENABLED(d->dr[7], i))
 519                         avail++;
 520         }
 521
 522         if (avail * 8 < size)
 523                 return (-1);
 524
 525         for (i = 0; i < 4 && size > 0; i++) {
 526                 if (!DBREG_DR7_ENABLED(d->dr[7], i)) {
 527                         if (size >= 8 || (avail == 1 && size > 4))
 528                                 wsize = 8;
 529                         else if (size > 2)
 530                                 wsize = 4;
 531                         else
 532                                 wsize = size;
 533                         amd64_set_watch(i, addr, wsize, DBREG_DR7_WRONLY, d);
 534                         addr += wsize;
 535                         size -= wsize;
 536                         avail--;
 537                 }
 538         }
 539
 540         set_dbregs(NULL, d);
 541         CPU_FOREACH(c) {
 542                 if (c == cpu)
 543                         continue;
 544                 pc = pcpu_find(c);
 545                 memcpy(pc->pc_dbreg, d, sizeof(*d));
 546                 pc->pc_dbreg_cmd = PC_DBREG_CMD_LOAD;
 547         }
 548
 549         return (0);
 550 }
 551
 552 int
 553 db_md_clr_watchpoint(addr, size)
 554         db_expr_t addr;
 555         db_expr_t size;
 556 {
 557         struct dbreg *d;
 558         struct pcpu *pc;
 559         int i, c, cpu;
 560
 561         d = (struct dbreg *)PCPU_PTR(dbreg);
 562         cpu = PCPU_GET(cpuid);
 563         fill_dbregs(NULL, d);
 564
 565         for (i = 0; i < 4; i++) {
 566                 if (DBREG_DR7_ENABLED(d->dr[7], i)) {
 567                         if (DBREG_DRX((d), i) >= addr &&
 568                             DBREG_DRX((d), i) < addr + size)
 569                                 amd64_clr_watch(i, d);
 570
 571                 }
 572         }
 573
 574         set_dbregs(NULL, d);
 575         CPU_FOREACH(c) {
 576                 if (c == cpu)
 577                         continue;
 578                 pc = pcpu_find(c);
 579                 memcpy(pc->pc_dbreg, d, sizeof(*d));
 580                 pc->pc_dbreg_cmd = PC_DBREG_CMD_LOAD;
 581         }
 582
 583         return (0);
 584 }
 585
 586
 587 static const char *
 588 watchtype_str(type)
 589         int type;
 590 {
 591         switch (type) {
 592                 case DBREG_DR7_EXEC   : return "execute";    break;
 593                 case DBREG_DR7_RDWR   : return "read/write"; break;
 594                 case DBREG_DR7_WRONLY : return "write";      break;
 595                 default               : return "invalid";    break;
 596         }
 597 }
 598
 599
 600 void
 601 db_md_list_watchpoints()
 602 {
 603         struct dbreg d;
 604         int i, len, type;
 605
 606         fill_dbregs(NULL, &d);
 607
 608         db_printf("\nhardware watchpoints:\n");
 609         db_printf("  watch    status        type  len             address\n");
 610         db_printf("  -----  --------  ----------  ---  ------------------\n");
 611         for (i = 0; i < 4; i++) {
 612                 if (DBREG_DR7_ENABLED(d.dr[7], i)) {
 613                         type = DBREG_DR7_ACCESS(d.dr[7], i);
 614                         len = DBREG_DR7_LEN(d.dr[7], i);
 615                         if (len == DBREG_DR7_LEN_8)
 616                                 len = 8;
 617                         else
 618                                 len++;
 619                         db_printf("  %-5d  %-8s  %10s  %3d  ",
 620                             i, "enabled", watchtype_str(type), len);
 621                         db_printsym((db_addr_t)DBREG_DRX((&d), i), DB_STGY_ANY);
 622                         db_printf("\n");
 623                 } else {
 624                         db_printf("  %-5d  disabled\n", i);
 625                 }
 626         }
 627
 628         db_printf("\ndebug register values:\n");
 629         for (i = 0; i < 8; i++) {
 630                 db_printf("  dr%d 0x%016lx\n", i, DBREG_DRX((&d), i));
 631         }
 632         db_printf("\n");
 633 }
 634
 635 void
 636 amd64_db_resume_dbreg(void)
 637 {
 638         struct dbreg *d;
 639
 640         switch (PCPU_GET(dbreg_cmd)) {
 641         case PC_DBREG_CMD_LOAD:
 642                 d = (struct dbreg *)PCPU_PTR(dbreg);
 643                 set_dbregs(NULL, d);
 644                 PCPU_SET(dbreg_cmd, PC_DBREG_CMD_NONE);
 645                 break;
 646         }
 647 }