sys/gdb/gdb_main.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2004 Marcel Moolenaar
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include <sys/cdefs.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include <sys/param.h>
  33 #include <sys/systm.h>
  34 #include <sys/kdb.h>
  35 #include <sys/kernel.h>
  36 #include <sys/pcpu.h>
  37 #include <sys/proc.h>
  38 #include <sys/reboot.h>
  39 #include <sys/sbuf.h>
  40
  41 #include <machine/gdb_machdep.h>
  42 #include <machine/kdb.h>
  43
  44 #include <gdb/gdb.h>
  45 #include <gdb/gdb_int.h>
  46
  47 SYSCTL_NODE(_debug, OID_AUTO, gdb, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  48     "GDB settings");
  49
  50 static dbbe_init_f gdb_init;
  51 static dbbe_trap_f gdb_trap;
  52
  53 KDB_BACKEND(gdb, gdb_init, NULL, NULL, gdb_trap);
  54
  55 static struct gdb_dbgport null_gdb_dbgport;
  56 DATA_SET(gdb_dbgport_set, null_gdb_dbgport);
  57 SET_DECLARE(gdb_dbgport_set, struct gdb_dbgport);
  58
  59 struct gdb_dbgport *gdb_cur = NULL;
  60 int gdb_listening = 0;
  61 bool gdb_ackmode = true;
  62
  63 static unsigned char gdb_bindata[64];
  64
  65 #ifdef DDB
  66 bool gdb_return_to_ddb = false;
  67 #endif
  68
  69 static int
  70 gdb_init(void)
  71 {
  72         struct gdb_dbgport *dp, **iter;
  73         int cur_pri, pri;
  74
  75         gdb_cur = NULL;
  76         cur_pri = -1;
  77         SET_FOREACH(iter, gdb_dbgport_set) {
  78                 dp = *iter;
  79                 pri = (dp->gdb_probe != NULL) ? dp->gdb_probe() : -1;
  80                 dp->gdb_active = (pri >= 0) ? 0 : -1;
  81                 if (pri > cur_pri) {
  82                         cur_pri = pri;
  83                         gdb_cur = dp;
  84                 }
  85         }
  86         if (gdb_cur != NULL) {
  87                 printf("GDB: debug ports:");
  88                 SET_FOREACH(iter, gdb_dbgport_set) {
  89                         dp = *iter;
  90                         if (dp->gdb_active == 0)
  91                                 printf(" %s", dp->gdb_name);
  92                 }
  93                 printf("\n");
  94         } else
  95                 printf("GDB: no debug ports present\n");
  96         if (gdb_cur != NULL) {
  97                 gdb_cur->gdb_init();
  98                 printf("GDB: current port: %s\n", gdb_cur->gdb_name);
  99         }
 100         if (gdb_cur != NULL) {
 101                 cur_pri = (boothowto & RB_GDB) ? 2 : 0;
 102                 gdb_consinit();
 103         } else
 104                 cur_pri = -1;
 105         return (cur_pri);
 106 }
 107
 108 static void
 109 gdb_do_mem_search(void)
 110 {
 111         size_t patlen;
 112         intmax_t addr, size;
 113         const unsigned char *found;
 114
 115         if (gdb_rx_varhex(&addr) || gdb_rx_char() != ';' ||
 116             gdb_rx_varhex(&size) || gdb_rx_char() != ';' ||
 117             gdb_rx_bindata(gdb_bindata, sizeof(gdb_bindata), &patlen)) {
 118                 gdb_tx_err(EINVAL);
 119                 return;
 120         }
 121         if (gdb_search_mem((char *)(uintptr_t)addr, size, gdb_bindata,
 122             patlen, &found)) {
 123                 if (found == 0ULL)
 124                         gdb_tx_begin('0');
 125                 else {
 126                         gdb_tx_begin('1');
 127                         gdb_tx_char(',');
 128                         gdb_tx_hex((intmax_t)(uintptr_t)found, 8);
 129                 }
 130                 gdb_tx_end();
 131         } else
 132                 gdb_tx_err(EIO);
 133 }
 134
 135 static void
 136 gdb_do_threadinfo(struct thread **thr_iter)
 137 {
 138         static struct thread * const done_sentinel = (void *)(uintptr_t)1;
 139         static const size_t tidsz_hex = sizeof(lwpid_t) * 2;
 140         size_t tds_sent;
 141
 142         if (*thr_iter == NULL) {
 143                 gdb_tx_err(ENXIO);
 144                 return;
 145         }
 146
 147         if (*thr_iter == done_sentinel) {
 148                 gdb_tx_begin('l');
 149                 *thr_iter = NULL;
 150                 goto sendit;
 151         }
 152
 153         gdb_tx_begin('m');
 154
 155         for (tds_sent = 0;
 156             *thr_iter != NULL && gdb_txbuf_has_capacity(tidsz_hex + 1);
 157             *thr_iter = kdb_thr_next(*thr_iter), tds_sent++) {
 158                 if (tds_sent > 0)
 159                         gdb_tx_char(',');
 160                 gdb_tx_varhex((*thr_iter)->td_tid);
 161         }
 162
 163         /*
 164          * Can't send EOF and "some" in same packet, so set a sentinel to send
 165          * EOF when GDB asks us next.
 166          */
 167         if (*thr_iter == NULL && tds_sent > 0)
 168                 *thr_iter = done_sentinel;
 169
 170 sendit:
 171         gdb_tx_end();
 172 }
 173
 174 #define BIT(n)  (1ull << (n))
 175 enum {
 176         GDB_MULTIPROCESS,
 177         GDB_SWBREAK,
 178         GDB_HWBREAK,
 179         GDB_QRELOCINSN,
 180         GDB_FORK_EVENTS,
 181         GDB_VFORK_EVENTS,
 182         GDB_EXEC_EVENTS,
 183         GDB_VCONT_SUPPORTED,
 184         GDB_QTHREADEVENTS,
 185         GDB_NO_RESUMED,
 186 };
 187 static const char * const gdb_feature_names[] = {
 188         [GDB_MULTIPROCESS] = "multiprocess",
 189         [GDB_SWBREAK] = "swbreak",
 190         [GDB_HWBREAK] = "hwbreak",
 191         [GDB_QRELOCINSN] = "qRelocInsn",
 192         [GDB_FORK_EVENTS] = "fork-events",
 193         [GDB_VFORK_EVENTS] = "vfork-events",
 194         [GDB_EXEC_EVENTS] = "exec-events",
 195         [GDB_VCONT_SUPPORTED] = "vContSupported",
 196         [GDB_QTHREADEVENTS] = "QThreadEvents",
 197         [GDB_NO_RESUMED] = "no-resumed",
 198 };
 199 static void
 200 gdb_do_qsupported(uint32_t *feat)
 201 {
 202         char *tok, *delim, ok;
 203         size_t i, toklen;
 204
 205         /* Parse supported host features */
 206         *feat = 0;
 207         if (gdb_rx_char() != ':')
 208                 goto error;
 209
 210         while (gdb_rxsz > 0) {
 211                 tok = gdb_rxp;
 212                 delim = strchrnul(gdb_rxp, ';');
 213                 toklen = (delim - tok);
 214
 215                 gdb_rxp += toklen;
 216                 gdb_rxsz -= toklen;
 217                 if (*delim != '\0') {
 218                         *delim = '\0';
 219                         gdb_rxp += 1;
 220                         gdb_rxsz -= 1;
 221                 }
 222
 223                 if (toklen < 2)
 224                         goto error;
 225
 226                 ok = tok[toklen - 1];
 227                 if (ok != '-' && ok != '+') {
 228                         /*
 229                          * GDB only has one KV-pair feature, and we don't
 230                          * support it, so ignore and move on.
 231                          */
 232                         if (strchr(tok, '=') != NULL)
 233                                 continue;
 234                         /* Not a KV-pair, and not a +/- flag?  Malformed. */
 235                         goto error;
 236                 }
 237                 if (ok != '+')
 238                         continue;
 239                 tok[toklen - 1] = '\0';
 240
 241                 for (i = 0; i < nitems(gdb_feature_names); i++)
 242                         if (strcmp(gdb_feature_names[i], tok) == 0)
 243                                 break;
 244
 245                 if (i == nitems(gdb_feature_names)) {
 246                         /* Unknown GDB feature. */
 247                         continue;
 248                 }
 249
 250                 *feat |= BIT(i);
 251         }
 252
 253         /* Send a supported feature list back */
 254         gdb_tx_begin(0);
 255
 256         gdb_tx_str("PacketSize");
 257         gdb_tx_char('=');
 258         /*
 259          * We don't buffer framing bytes, but we do need to retain a byte for a
 260          * trailing nul.
 261          */
 262         gdb_tx_varhex(GDB_BUFSZ + strlen("$#nn") - 1);
 263
 264         gdb_tx_str(";qXfer:threads:read+");
 265
 266         /*
 267          * If the debugport is a reliable transport, request No Ack mode from
 268          * the server.  The server may or may not choose to enter No Ack mode.
 269          * https://sourceware.org/gdb/onlinedocs/gdb/Packet-Acknowledgment.html
 270          */
 271         if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_RELIABLE)
 272                 gdb_tx_str(";QStartNoAckMode+");
 273
 274         /*
 275          * Future consideration:
 276          *   - vCont
 277          *   - multiprocess
 278          */
 279         gdb_tx_end();
 280         return;
 281
 282 error:
 283         *feat = 0;
 284         gdb_tx_err(EINVAL);
 285 }
 286
 287 /*
 288  * A qXfer_context provides a vaguely generic way to generate a multi-packet
 289  * response on the fly, making some assumptions about the size of sbuf writes
 290  * vs actual packet length constraints.  A non-byzantine gdb host should allow
 291  * hundreds of bytes per packet or more.
 292  *
 293  * Upper layers are considered responsible for escaping the four forbidden
 294  * characters '# $ } *'.
 295  */
 296 struct qXfer_context {
 297         struct sbuf sb;
 298         size_t last_offset;
 299         bool flushed;
 300         bool lastmessage;
 301         char xfer_buf[GDB_BUFSZ];
 302 };
 303
 304 static int
 305 qXfer_drain(void *v, const char *buf, int len)
 306 {
 307         struct qXfer_context *qx;
 308
 309         if (len < 0)
 310                 return (-EINVAL);
 311
 312         qx = v;
 313         if (qx->flushed) {
 314                 /*
 315                  * Overflow.  We lost some message.  Maybe the packet size is
 316                  * ridiculously small.
 317                  */
 318                 printf("%s: Overflow in qXfer detected.\n", __func__);
 319                 return (-ENOBUFS);
 320         }
 321
 322         qx->last_offset += len;
 323         qx->flushed = true;
 324
 325         if (qx->lastmessage)
 326                 gdb_tx_begin('l');
 327         else
 328                 gdb_tx_begin('m');
 329
 330         memcpy(gdb_txp, buf, len);
 331         gdb_txp += len;
 332
 333         gdb_tx_end();
 334         return (len);
 335 }
 336
 337 static int
 338 init_qXfer_ctx(struct qXfer_context *qx, uintmax_t len)
 339 {
 340
 341         /* Protocol (max) length field includes framing overhead. */
 342         if (len < sizeof("$m#nn"))
 343                 return (ENOSPC);
 344
 345         len -= 4;
 346         len = ummin(len, GDB_BUFSZ - 1);
 347
 348         qx->last_offset = 0;
 349         qx->flushed = false;
 350         qx->lastmessage = false;
 351         sbuf_new(&qx->sb, qx->xfer_buf, len, SBUF_FIXEDLEN);
 352         sbuf_set_drain(&qx->sb, qXfer_drain, qx);
 353         return (0);
 354 }
 355
 356 /*
 357  * dst must be 2x strlen(max_src) + 1.
 358  *
 359  * Squashes invalid XML characters down to _.  Sorry.  Then escapes for GDB.
 360  */
 361 static void
 362 qXfer_escape_xmlattr_str(char *dst, size_t dstlen, const char *src)
 363 {
 364         static const char *forbidden = "#$}*";
 365
 366         size_t i;
 367         char c;
 368
 369         for (i = 0; i < dstlen - 1 && *src != 0; src++, i++) {
 370                 c = *src;
 371                 /* XML attr filter */
 372                 if (c < 32)
 373                         c = '_';
 374                 /* We assume attributes will be "" quoted. */
 375                 if (c == '<' || c == '&' || c == '"')
 376                         c = '_';
 377
 378                 /* GDB escape. */
 379                 if (strchr(forbidden, c) != NULL) {
 380                         *dst++ = '}';
 381                         c ^= 0x20;
 382                 }
 383                 *dst++ = c;
 384         }
 385         if (*src != 0)
 386                 printf("XXX%s: overflow; API misuse\n", __func__);
 387
 388         *dst = 0;
 389 }
 390
 391 /*
 392  * Dynamically generate qXfer:threads document, one packet at a time.
 393  *
 394  * The format is loosely described[0], although it does not seem that the
 395  * <?xml?> mentioned on that page is required.
 396  *
 397  * [0]: https://sourceware.org/gdb/current/onlinedocs/gdb/Thread-List-Format.html
 398  */
 399 static void
 400 do_qXfer_threads_read(void)
 401 {
 402         /* Kludgy context */
 403         static struct {
 404                 struct qXfer_context qXfer;
 405                 /* Kludgy state machine */
 406                 struct thread *iter;
 407                 enum {
 408                         XML_START_THREAD,       /* '<thread' */
 409                         XML_THREAD_ID,          /* ' id="xxx"' */
 410                         XML_THREAD_CORE,        /* ' core="yyy"' */
 411                         XML_THREAD_NAME,        /* ' name="zzz"' */
 412                         XML_THREAD_EXTRA,       /* '> ...' */
 413                         XML_END_THREAD,         /* '</thread>' */
 414                         XML_SENT_END_THREADS,   /* '</threads>' */
 415                 } next_step;
 416         } ctx;
 417         static char td_name_escape[MAXCOMLEN * 2 + 1];
 418
 419         const char *name_src;
 420         uintmax_t offset, len;
 421         int error;
 422
 423         /* Annex part must be empty. */
 424         if (gdb_rx_char() != ':')
 425                 goto misformed_request;
 426
 427         if (gdb_rx_varhex(&offset) != 0 ||
 428             gdb_rx_char() != ',' ||
 429             gdb_rx_varhex(&len) != 0)
 430                 goto misformed_request;
 431
 432         /*
 433          * Validate resume xfers.
 434          */
 435         if (offset != 0) {
 436                 if (offset != ctx.qXfer.last_offset) {
 437                         printf("%s: Resumed offset %ju != expected %zu\n",
 438                             __func__, offset, ctx.qXfer.last_offset);
 439                         error = ESPIPE;
 440                         goto request_error;
 441                 }
 442                 ctx.qXfer.flushed = false;
 443         }
 444
 445         if (offset == 0) {
 446                 ctx.iter = kdb_thr_first();
 447                 ctx.next_step = XML_START_THREAD;
 448                 error = init_qXfer_ctx(&ctx.qXfer, len);
 449                 if (error != 0)
 450                         goto request_error;
 451
 452                 sbuf_cat(&ctx.qXfer.sb, "<threads>");
 453         }
 454
 455         while (!ctx.qXfer.flushed && ctx.iter != NULL) {
 456                 switch (ctx.next_step) {
 457                 case XML_START_THREAD:
 458                         ctx.next_step = XML_THREAD_ID;
 459                         sbuf_cat(&ctx.qXfer.sb, "<thread");
 460                         continue;
 461
 462                 case XML_THREAD_ID:
 463                         ctx.next_step = XML_THREAD_CORE;
 464                         sbuf_printf(&ctx.qXfer.sb, " id=\"%jx\"",
 465                             (uintmax_t)ctx.iter->td_tid);
 466                         continue;
 467
 468                 case XML_THREAD_CORE:
 469                         ctx.next_step = XML_THREAD_NAME;
 470                         if (ctx.iter->td_oncpu != NOCPU) {
 471                                 sbuf_printf(&ctx.qXfer.sb, " core=\"%d\"",
 472                                     ctx.iter->td_oncpu);
 473                         }
 474                         continue;
 475
 476                 case XML_THREAD_NAME:
 477                         ctx.next_step = XML_THREAD_EXTRA;
 478
 479                         if (ctx.iter->td_name[0] != 0)
 480                                 name_src = ctx.iter->td_name;
 481                         else if (ctx.iter->td_proc != NULL &&
 482                             ctx.iter->td_proc->p_comm[0] != 0)
 483                                 name_src = ctx.iter->td_proc->p_comm;
 484                         else
 485                                 continue;
 486
 487                         qXfer_escape_xmlattr_str(td_name_escape,
 488                             sizeof(td_name_escape), name_src);
 489                         sbuf_printf(&ctx.qXfer.sb, " name=\"%s\"",
 490                             td_name_escape);
 491                         continue;
 492
 493                 case XML_THREAD_EXTRA:
 494                         ctx.next_step = XML_END_THREAD;
 495
 496                         sbuf_putc(&ctx.qXfer.sb, '>');
 497
 498                         if (ctx.iter->td_state == TDS_RUNNING)
 499                                 sbuf_cat(&ctx.qXfer.sb, "Running");
 500                         else if (ctx.iter->td_state == TDS_RUNQ)
 501                                 sbuf_cat(&ctx.qXfer.sb, "RunQ");
 502                         else if (ctx.iter->td_state == TDS_CAN_RUN)
 503                                 sbuf_cat(&ctx.qXfer.sb, "CanRun");
 504                         else if (TD_ON_LOCK(ctx.iter))
 505                                 sbuf_cat(&ctx.qXfer.sb, "Blocked");
 506                         else if (TD_IS_SLEEPING(ctx.iter))
 507                                 sbuf_cat(&ctx.qXfer.sb, "Sleeping");
 508                         else if (TD_IS_SWAPPED(ctx.iter))
 509                                 sbuf_cat(&ctx.qXfer.sb, "Swapped");
 510                         else if (TD_AWAITING_INTR(ctx.iter))
 511                                 sbuf_cat(&ctx.qXfer.sb, "IthreadWait");
 512                         else if (TD_IS_SUSPENDED(ctx.iter))
 513                                 sbuf_cat(&ctx.qXfer.sb, "Suspended");
 514                         else
 515                                 sbuf_cat(&ctx.qXfer.sb, "???");
 516                         continue;
 517
 518                 case XML_END_THREAD:
 519                         ctx.next_step = XML_START_THREAD;
 520                         sbuf_cat(&ctx.qXfer.sb, "</thread>");
 521                         ctx.iter = kdb_thr_next(ctx.iter);
 522                         continue;
 523
 524                 /*
 525                  * This one isn't part of the looping state machine,
 526                  * but GCC complains if you leave an enum value out of the
 527                  * select.
 528                  */
 529                 case XML_SENT_END_THREADS:
 530                         /* NOTREACHED */
 531                         break;
 532                 }
 533         }
 534         if (ctx.qXfer.flushed)
 535                 return;
 536
 537         if (ctx.next_step != XML_SENT_END_THREADS) {
 538                 ctx.next_step = XML_SENT_END_THREADS;
 539                 sbuf_cat(&ctx.qXfer.sb, "</threads>");
 540         }
 541         if (ctx.qXfer.flushed)
 542                 return;
 543
 544         ctx.qXfer.lastmessage = true;
 545         sbuf_finish(&ctx.qXfer.sb);
 546         sbuf_delete(&ctx.qXfer.sb);
 547         ctx.qXfer.last_offset = 0;
 548         return;
 549
 550 misformed_request:
 551         /*
 552          * GDB "General-Query-Packets.html" qXfer-read anchor specifically
 553          * documents an E00 code for malformed requests or invalid annex.
 554          * Non-zero codes indicate invalid offset or "error reading the data."
 555          */
 556         error = 0;
 557 request_error:
 558         gdb_tx_err(error);
 559         return;
 560 }
 561
 562 /*
 563  * A set of standardized transfers from "special data areas."
 564  *
 565  * We've already matched on "qXfer:" and advanced the rx packet buffer past
 566  * that bit.  Parse out the rest of the packet and generate an appropriate
 567  * response.
 568  */
 569 static void
 570 do_qXfer(void)
 571 {
 572         if (!gdb_rx_equal("threads:"))
 573                 goto unrecognized;
 574
 575         if (!gdb_rx_equal("read:"))
 576                 goto unrecognized;
 577
 578         do_qXfer_threads_read();
 579         return;
 580
 581 unrecognized:
 582         gdb_tx_empty();
 583         return;
 584 }
 585
 586 static void
 587 gdb_handle_detach(void)
 588 {
 589         kdb_cpu_clear_singlestep();
 590         gdb_listening = 0;
 591
 592         if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM)
 593                 gdb_cur->gdb_term();
 594
 595 #ifdef DDB
 596         if (!gdb_return_to_ddb)
 597                 return;
 598
 599         gdb_return_to_ddb = false;
 600
 601         if (kdb_dbbe_select("ddb") != 0)
 602                 printf("The ddb backend could not be selected.\n");
 603 #endif
 604 }
 605
 606 static int
 607 gdb_trap(int type, int code)
 608 {
 609         jmp_buf jb;
 610         struct thread *thr_iter;
 611         void *prev_jb;
 612         uint32_t host_features;
 613
 614         prev_jb = kdb_jmpbuf(jb);
 615         if (setjmp(jb) != 0) {
 616                 printf("%s bailing, hopefully back to ddb!\n", __func__);
 617                 gdb_listening = 0;
 618                 (void)kdb_jmpbuf(prev_jb);
 619                 return (1);
 620         }
 621
 622         gdb_listening = 0;
 623         gdb_ackmode = true;
 624
 625         /*
 626          * Send a T packet. We currently do not support watchpoints (the
 627          * awatch, rwatch or watch elements).
 628          */
 629         gdb_tx_begin('T');
 630         gdb_tx_hex(gdb_cpu_signal(type, code), 2);
 631         gdb_tx_varhex(GDB_REG_PC);
 632         gdb_tx_char(':');
 633         gdb_tx_reg(GDB_REG_PC);
 634         gdb_tx_char(';');
 635         gdb_tx_str("thread:");
 636         gdb_tx_varhex((long)kdb_thread->td_tid);
 637         gdb_tx_char(';');
 638         gdb_tx_end();                   /* XXX check error condition. */
 639
 640         thr_iter = NULL;
 641         while (gdb_rx_begin() == 0) {
 642                 /* printf("GDB: got '%s'\n", gdb_rxp); */
 643                 switch (gdb_rx_char()) {
 644                 case '?':       /* Last signal. */
 645                         gdb_tx_begin('T');
 646                         gdb_tx_hex(gdb_cpu_signal(type, code), 2);
 647                         gdb_tx_str("thread:");
 648                         gdb_tx_varhex((long)kdb_thread->td_tid);
 649                         gdb_tx_char(';');
 650                         gdb_tx_end();
 651                         break;
 652                 case 'c': {     /* Continue. */
 653                         uintmax_t addr;
 654                         register_t pc;
 655                         if (!gdb_rx_varhex(&addr)) {
 656                                 pc = addr;
 657                                 gdb_cpu_setreg(GDB_REG_PC, &pc);
 658                         }
 659                         kdb_cpu_clear_singlestep();
 660                         gdb_listening = 1;
 661                         return (1);
 662                 }
 663                 case 'C': {     /* Continue with signal. */
 664                         uintmax_t addr, sig;
 665                         register_t pc;
 666                         if (!gdb_rx_varhex(&sig) && gdb_rx_char() == ';' &&
 667                             !gdb_rx_varhex(&addr)) {
 668                                 pc = addr;
 669                                 gdb_cpu_setreg(GDB_REG_PC, &pc);
 670                         }
 671                         kdb_cpu_clear_singlestep();
 672                         gdb_listening = 1;
 673                         return (1);
 674                 }
 675                 case 'D': {     /* Detach */
 676                         gdb_tx_ok();
 677                         gdb_handle_detach();
 678                         return (1);
 679                 }
 680                 case 'g': {     /* Read registers. */
 681                         size_t r;
 682                         gdb_tx_begin(0);
 683                         for (r = 0; r < GDB_NREGS; r++)
 684                                 gdb_tx_reg(r);
 685                         gdb_tx_end();
 686                         break;
 687                 }
 688                 case 'G':       /* Write registers. */
 689                         gdb_tx_err(0);
 690                         break;
 691                 case 'H': {     /* Set thread. */
 692                         intmax_t tid;
 693                         struct thread *thr;
 694
 695                         /* Ignore 'g' (general) or 'c' (continue) flag. */
 696                         (void) gdb_rx_char();
 697
 698                         if (gdb_rx_varhex(&tid)) {
 699                                 gdb_tx_err(EINVAL);
 700                                 break;
 701                         }
 702                         if (tid > 0) {
 703                                 thr = kdb_thr_lookup(tid);
 704                                 if (thr == NULL) {
 705                                         gdb_tx_err(ENOENT);
 706                                         break;
 707                                 }
 708                                 kdb_thr_select(thr);
 709                         }
 710                         gdb_tx_ok();
 711                         break;
 712                 }
 713                 case 'k':       /* Kill request. */
 714                         gdb_handle_detach();
 715                         return (1);
 716                 case 'm': {     /* Read memory. */
 717                         uintmax_t addr, size;
 718                         if (gdb_rx_varhex(&addr) || gdb_rx_char() != ',' ||
 719                             gdb_rx_varhex(&size)) {
 720                                 gdb_tx_err(EINVAL);
 721                                 break;
 722                         }
 723                         gdb_tx_begin(0);
 724                         if (gdb_tx_mem((char *)(uintptr_t)addr, size))
 725                                 gdb_tx_end();
 726                         else
 727                                 gdb_tx_err(EIO);
 728                         break;
 729                 }
 730                 case 'M': {     /* Write memory. */
 731                         uintmax_t addr, size;
 732                         if (gdb_rx_varhex(&addr) || gdb_rx_char() != ',' ||
 733                             gdb_rx_varhex(&size) || gdb_rx_char() != ':') {
 734                                 gdb_tx_err(EINVAL);
 735                                 break;
 736                         }
 737                         if (gdb_rx_mem((char *)(uintptr_t)addr, size) == 0)
 738                                 gdb_tx_err(EIO);
 739                         else
 740                                 gdb_tx_ok();
 741                         break;
 742                 }
 743                 case 'P': {     /* Write register. */
 744                         char *val;
 745                         uintmax_t reg;
 746                         val = gdb_rxp;
 747                         if (gdb_rx_varhex(&reg) || gdb_rx_char() != '=' ||
 748                             !gdb_rx_mem(val, gdb_cpu_regsz(reg))) {
 749                                 gdb_tx_err(EINVAL);
 750                                 break;
 751                         }
 752                         gdb_cpu_setreg(reg, val);
 753                         gdb_tx_ok();
 754                         break;
 755                 }
 756                 case 'q':       /* General query. */
 757                         if (gdb_rx_equal("C")) {
 758                                 gdb_tx_begin('Q');
 759                                 gdb_tx_char('C');
 760                                 gdb_tx_varhex((long)kdb_thread->td_tid);
 761                                 gdb_tx_end();
 762                         } else if (gdb_rx_equal("Supported")) {
 763                                 gdb_do_qsupported(&host_features);
 764                         } else if (gdb_rx_equal("fThreadInfo")) {
 765                                 thr_iter = kdb_thr_first();
 766                                 gdb_do_threadinfo(&thr_iter);
 767                         } else if (gdb_rx_equal("sThreadInfo")) {
 768                                 gdb_do_threadinfo(&thr_iter);
 769                         } else if (gdb_rx_equal("Xfer:")) {
 770                                 do_qXfer();
 771                         } else if (gdb_rx_equal("Search:memory:")) {
 772                                 gdb_do_mem_search();
 773 #ifdef __powerpc__
 774                         } else if (gdb_rx_equal("Offsets")) {
 775                                 gdb_cpu_do_offsets();
 776 #endif
 777                         } else if (!gdb_cpu_query())
 778                                 gdb_tx_empty();
 779                         break;
 780                 case 'Q':
 781                         if (gdb_rx_equal("StartNoAckMode")) {
 782                                 if ((gdb_cur->gdb_dbfeatures &
 783                                     GDB_DBGP_FEAT_RELIABLE) == 0) {
 784                                         /*
 785                                          * Shouldn't happen if we didn't
 786                                          * advertise support.  Reject.
 787                                          */
 788                                         gdb_tx_empty();
 789                                         break;
 790                                 }
 791                                 gdb_ackmode = false;
 792                                 gdb_tx_ok();
 793                         } else
 794                                 gdb_tx_empty();
 795                         break;
 796                 case 's': {     /* Step. */
 797                         uintmax_t addr;
 798                         register_t pc;
 799                         if (!gdb_rx_varhex(&addr)) {
 800                                 pc = addr;
 801                                 gdb_cpu_setreg(GDB_REG_PC, &pc);
 802                         }
 803                         kdb_cpu_set_singlestep();
 804                         gdb_listening = 1;
 805                         return (1);
 806                 }
 807                 case 'S': {     /* Step with signal. */
 808                         uintmax_t addr, sig;
 809                         register_t pc;
 810                         if (!gdb_rx_varhex(&sig) && gdb_rx_char() == ';' &&
 811                             !gdb_rx_varhex(&addr)) {
 812                                 pc = addr;
 813                                 gdb_cpu_setreg(GDB_REG_PC, &pc);
 814                         }
 815                         kdb_cpu_set_singlestep();
 816                         gdb_listening = 1;
 817                         return (1);
 818                 }
 819                 case 'T': {     /* Thread alive. */
 820                         intmax_t tid;
 821                         if (gdb_rx_varhex(&tid)) {
 822                                 gdb_tx_err(EINVAL);
 823                                 break;
 824                         }
 825                         if (kdb_thr_lookup(tid) != NULL)
 826                                 gdb_tx_ok();
 827                         else
 828                                 gdb_tx_err(ENOENT);
 829                         break;
 830                 }
 831                 case EOF:
 832                         /* Empty command. Treat as unknown command. */
 833                         /* FALLTHROUGH */
 834                 default:
 835                         /* Unknown command. Send empty response. */
 836                         gdb_tx_empty();
 837                         break;
 838                 }
 839         }
 840         (void)kdb_jmpbuf(prev_jb);
 841         return (0);
 842 }