1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
30#include <sys/systm.h>
31#include <sys/kdb.h>
32#include <sys/kernel.h>
33#include <sys/pcpu.h>
34#include <sys/proc.h>
35#include <sys/reboot.h>
36#include <sys/sbuf.h>
37
38#include <machine/gdb_machdep.h>
39#include <machine/kdb.h>
40
41#include <gdb/gdb.h>
42#include <gdb/gdb_int.h>
43
44SYSCTL_NODE(_debug, OID_AUTO, gdb, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
45    "GDB settings");
46
47static dbbe_init_f gdb_init;
48static dbbe_trap_f gdb_trap;
49
50KDB_BACKEND(gdb, gdb_init, NULL, NULL, gdb_trap);
51
52static struct gdb_dbgport null_gdb_dbgport;
53DATA_SET(gdb_dbgport_set, null_gdb_dbgport);
54SET_DECLARE(gdb_dbgport_set, struct gdb_dbgport);
55
56struct gdb_dbgport *gdb_cur = NULL;
57int gdb_listening = 0;
58bool gdb_ackmode = true;
59
60static unsigned char gdb_bindata[64];
61
62#ifdef DDB
63bool gdb_return_to_ddb = false;
64#endif
65
66static int
67gdb_init(void)
68{
69	struct gdb_dbgport *dp, **iter;
70	int cur_pri, pri;
71
72	gdb_cur = NULL;
73	cur_pri = -1;
74	SET_FOREACH(iter, gdb_dbgport_set) {
75		dp = *iter;
76		pri = (dp->gdb_probe != NULL) ? dp->gdb_probe() : -1;
77		dp->gdb_active = (pri >= 0) ? 0 : -1;
78		if (pri > cur_pri) {
79			cur_pri = pri;
80			gdb_cur = dp;
81		}
82	}
83	if (gdb_cur != NULL) {
84		printf("GDB: debug ports:");
85		SET_FOREACH(iter, gdb_dbgport_set) {
86			dp = *iter;
87			if (dp->gdb_active == 0)
88				printf(" %s", dp->gdb_name);
89		}
90		printf("\n");
91	} else
92		printf("GDB: no debug ports present\n");
93	if (gdb_cur != NULL) {
94		gdb_cur->gdb_init();
95		printf("GDB: current port: %s\n", gdb_cur->gdb_name);
96	}
97	if (gdb_cur != NULL) {
98		cur_pri = (boothowto & RB_GDB) ? 2 : 0;
99		gdb_consinit();
100	} else
101		cur_pri = -1;
102	return (cur_pri);
103}
104
105static void
106gdb_do_mem_search(void)
107{
108	size_t patlen;
109	intmax_t addr, size;
110	const unsigned char *found;
111
112	if (gdb_rx_varhex(&addr) || gdb_rx_char() != ';' ||
113	    gdb_rx_varhex(&size) || gdb_rx_char() != ';' ||
114	    gdb_rx_bindata(gdb_bindata, sizeof(gdb_bindata), &patlen)) {
115		gdb_tx_err(EINVAL);
116		return;
117	}
118	if (gdb_search_mem((char *)(uintptr_t)addr, size, gdb_bindata,
119	    patlen, &found)) {
120		if (found == 0ULL)
121			gdb_tx_begin('0');
122		else {
123			gdb_tx_begin('1');
124			gdb_tx_char(',');
125			gdb_tx_hex((intmax_t)(uintptr_t)found, 8);
126		}
127		gdb_tx_end();
128	} else
129		gdb_tx_err(EIO);
130}
131
132static void
133gdb_do_threadinfo(struct thread **thr_iter)
134{
135	static struct thread * const done_sentinel = (void *)(uintptr_t)1;
136	static const size_t tidsz_hex = sizeof(lwpid_t) * 2;
137	size_t tds_sent;
138
139	if (*thr_iter == NULL) {
140		gdb_tx_err(ENXIO);
141		return;
142	}
143
144	if (*thr_iter == done_sentinel) {
145		gdb_tx_begin('l');
146		*thr_iter = NULL;
147		goto sendit;
148	}
149
150	gdb_tx_begin('m');
151
152	for (tds_sent = 0;
153	    *thr_iter != NULL && gdb_txbuf_has_capacity(tidsz_hex + 1);
154	    *thr_iter = kdb_thr_next(*thr_iter), tds_sent++) {
155		if (tds_sent > 0)
156			gdb_tx_char(',');
157		gdb_tx_varhex((*thr_iter)->td_tid);
158	}
159
160	/*
161	 * Can't send EOF and "some" in same packet, so set a sentinel to send
162	 * EOF when GDB asks us next.
163	 */
164	if (*thr_iter == NULL && tds_sent > 0)
165		*thr_iter = done_sentinel;
166
167sendit:
168	gdb_tx_end();
169}
170
171#define	BIT(n)	(1ull << (n))
172enum {
173	GDB_MULTIPROCESS,
174	GDB_SWBREAK,
175	GDB_HWBREAK,
176	GDB_QRELOCINSN,
177	GDB_FORK_EVENTS,
178	GDB_VFORK_EVENTS,
179	GDB_EXEC_EVENTS,
180	GDB_VCONT_SUPPORTED,
181	GDB_QTHREADEVENTS,
182	GDB_NO_RESUMED,
183};
184static const char * const gdb_feature_names[] = {
185	[GDB_MULTIPROCESS] = "multiprocess",
186	[GDB_SWBREAK] = "swbreak",
187	[GDB_HWBREAK] = "hwbreak",
188	[GDB_QRELOCINSN] = "qRelocInsn",
189	[GDB_FORK_EVENTS] = "fork-events",
190	[GDB_VFORK_EVENTS] = "vfork-events",
191	[GDB_EXEC_EVENTS] = "exec-events",
192	[GDB_VCONT_SUPPORTED] = "vContSupported",
193	[GDB_QTHREADEVENTS] = "QThreadEvents",
194	[GDB_NO_RESUMED] = "no-resumed",
195};
196static void
197gdb_do_qsupported(uint32_t *feat)
198{
199	char *tok, *delim, ok;
200	size_t i, toklen;
201
202	/* Parse supported host features */
203	*feat = 0;
204	switch (gdb_rx_char()) {
205	case ':':
206		break;
207	case EOF:
208		goto nofeatures;
209	default:
210		goto error;
211	}
212
213	while (gdb_rxsz > 0) {
214		tok = gdb_rxp;
215		delim = strchrnul(gdb_rxp, ';');
216		toklen = (delim - tok);
217
218		gdb_rxp += toklen;
219		gdb_rxsz -= toklen;
220		if (*delim != '\0') {
221			*delim = '\0';
222			gdb_rxp += 1;
223			gdb_rxsz -= 1;
224		}
225
226		if (toklen < 2)
227			goto error;
228
229		ok = tok[toklen - 1];
230		if (ok != '-' && ok != '+') {
231			/*
232			 * GDB only has one KV-pair feature, and we don't
233			 * support it, so ignore and move on.
234			 */
235			if (strchr(tok, '=') != NULL)
236				continue;
237			/* Not a KV-pair, and not a +/- flag?  Malformed. */
238			goto error;
239		}
240		if (ok != '+')
241			continue;
242		tok[toklen - 1] = '\0';
243
244		for (i = 0; i < nitems(gdb_feature_names); i++)
245			if (strcmp(gdb_feature_names[i], tok) == 0)
246				break;
247
248		if (i == nitems(gdb_feature_names)) {
249			/* Unknown GDB feature. */
250			continue;
251		}
252
253		*feat |= BIT(i);
254	}
255
256nofeatures:
257	/* Send a supported feature list back */
258	gdb_tx_begin(0);
259
260	gdb_tx_str("PacketSize");
261	gdb_tx_char('=');
262	/*
263	 * We don't buffer framing bytes, but we do need to retain a byte for a
264	 * trailing nul.
265	 */
266	gdb_tx_varhex(GDB_BUFSZ + strlen("$#nn") - 1);
267
268	gdb_tx_str(";qXfer:threads:read+");
269
270#ifdef HAS_HW_BREAKPOINT
271	if ((*feat & GDB_HWBREAK) != 0)
272		gdb_tx_str(";hwbreak+");
273#endif
274
275	/*
276	 * If the debugport is a reliable transport, request No Ack mode from
277	 * the server.  The server may or may not choose to enter No Ack mode.
278	 * https://sourceware.org/gdb/onlinedocs/gdb/Packet-Acknowledgment.html
279	 */
280	if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_RELIABLE)
281		gdb_tx_str(";QStartNoAckMode+");
282
283	/*
284	 * Future consideration:
285	 *   - vCont
286	 *   - multiprocess
287	 */
288	gdb_tx_end();
289	return;
290
291error:
292	*feat = 0;
293	gdb_tx_err(EINVAL);
294}
295
296/*
297 * A qXfer_context provides a vaguely generic way to generate a multi-packet
298 * response on the fly, making some assumptions about the size of sbuf writes
299 * vs actual packet length constraints.  A non-byzantine gdb host should allow
300 * hundreds of bytes per packet or more.
301 *
302 * Upper layers are considered responsible for escaping the four forbidden
303 * characters '# $ } *'.
304 */
305struct qXfer_context {
306	struct sbuf sb;
307	size_t last_offset;
308	bool flushed;
309	bool lastmessage;
310	char xfer_buf[GDB_BUFSZ];
311};
312
313static int
314qXfer_drain(void *v, const char *buf, int len)
315{
316	struct qXfer_context *qx;
317
318	if (len < 0)
319		return (-EINVAL);
320
321	qx = v;
322	if (qx->flushed) {
323		/*
324		 * Overflow.  We lost some message.  Maybe the packet size is
325		 * ridiculously small.
326		 */
327		printf("%s: Overflow in qXfer detected.\n", __func__);
328		return (-ENOBUFS);
329	}
330
331	qx->last_offset += len;
332	qx->flushed = true;
333
334	if (qx->lastmessage)
335		gdb_tx_begin('l');
336	else
337		gdb_tx_begin('m');
338
339	memcpy(gdb_txp, buf, len);
340	gdb_txp += len;
341
342	gdb_tx_end();
343	return (len);
344}
345
346static int
347init_qXfer_ctx(struct qXfer_context *qx, uintmax_t len)
348{
349
350	/* Protocol (max) length field includes framing overhead. */
351	if (len < sizeof("$m#nn"))
352		return (ENOSPC);
353
354	len -= 4;
355	len = ummin(len, GDB_BUFSZ - 1);
356
357	qx->last_offset = 0;
358	qx->flushed = false;
359	qx->lastmessage = false;
360	sbuf_new(&qx->sb, qx->xfer_buf, len, SBUF_FIXEDLEN);
361	sbuf_set_drain(&qx->sb, qXfer_drain, qx);
362	return (0);
363}
364
365/*
366 * Squashes special XML and GDB characters down to _.  Sorry.
367 */
368static void
369qXfer_escape_xmlattr_str(char *dst, size_t dstlen, const char *src)
370{
371	static const char *forbidden = "#$}*";
372
373	size_t i;
374	char c;
375
376	for (i = 0; i < dstlen - 1 && *src != 0; src++, i++) {
377		c = *src;
378		/* XML attr filter */
379		if (c < 32)
380			c = '_';
381		/* We assume attributes will be "" quoted. */
382		if (c == '<' || c == '&' || c == '"')
383			c = '_';
384
385		/* GDB escape. */
386		if (strchr(forbidden, c) != NULL) {
387			/*
388			 * It would be nice to escape these properly, but to do
389			 * it correctly we need to escape them in the transmit
390			 * layer, potentially doubling our buffer requirements.
391			 * For now, avoid breaking the protocol by squashing
392			 * them to underscore.
393			 */
394#if 0
395			*dst++ = '}';
396			c ^= 0x20;
397#endif
398			c = '_';
399		}
400		*dst++ = c;
401	}
402	if (*src != 0)
403		printf("XXX%s: overflow; API misuse\n", __func__);
404
405	*dst = 0;
406}
407
408/*
409 * Dynamically generate qXfer:threads document, one packet at a time.
410 *
411 * The format is loosely described[0], although it does not seem that the
412 * <?xml?> mentioned on that page is required.
413 *
414 * [0]: https://sourceware.org/gdb/current/onlinedocs/gdb/Thread-List-Format.html
415 */
416static void
417do_qXfer_threads_read(void)
418{
419	/* Kludgy context */
420	static struct {
421		struct qXfer_context qXfer;
422		/* Kludgy state machine */
423		struct thread *iter;
424		enum {
425			XML_START_THREAD,	/* '<thread' */
426			XML_THREAD_ID,		/* ' id="xxx"' */
427			XML_THREAD_CORE,	/* ' core="yyy"' */
428			XML_THREAD_NAME,	/* ' name="zzz"' */
429			XML_THREAD_EXTRA,	/* '> ...' */
430			XML_END_THREAD,		/* '</thread>' */
431			XML_SENT_END_THREADS,	/* '</threads>' */
432		} next_step;
433	} ctx;
434	static char td_name_escape[MAXCOMLEN * 2 + 1];
435
436	const char *name_src;
437	uintmax_t offset, len;
438	int error;
439
440	/* Annex part must be empty. */
441	if (gdb_rx_char() != ':')
442		goto misformed_request;
443
444	if (gdb_rx_varhex(&offset) != 0 ||
445	    gdb_rx_char() != ',' ||
446	    gdb_rx_varhex(&len) != 0)
447		goto misformed_request;
448
449	/*
450	 * Validate resume xfers.
451	 */
452	if (offset != 0) {
453		if (offset != ctx.qXfer.last_offset) {
454			printf("%s: Resumed offset %ju != expected %zu\n",
455			    __func__, offset, ctx.qXfer.last_offset);
456			error = ESPIPE;
457			goto request_error;
458		}
459		ctx.qXfer.flushed = false;
460	}
461
462	if (offset == 0) {
463		ctx.iter = kdb_thr_first();
464		ctx.next_step = XML_START_THREAD;
465		error = init_qXfer_ctx(&ctx.qXfer, len);
466		if (error != 0)
467			goto request_error;
468
469		sbuf_cat(&ctx.qXfer.sb, "<threads>");
470	}
471
472	while (!ctx.qXfer.flushed && ctx.iter != NULL) {
473		switch (ctx.next_step) {
474		case XML_START_THREAD:
475			ctx.next_step = XML_THREAD_ID;
476			sbuf_cat(&ctx.qXfer.sb, "<thread");
477			continue;
478
479		case XML_THREAD_ID:
480			ctx.next_step = XML_THREAD_CORE;
481			sbuf_printf(&ctx.qXfer.sb, " id=\"%jx\"",
482			    (uintmax_t)ctx.iter->td_tid);
483			continue;
484
485		case XML_THREAD_CORE:
486			ctx.next_step = XML_THREAD_NAME;
487			if (ctx.iter->td_oncpu != NOCPU) {
488				sbuf_printf(&ctx.qXfer.sb, " core=\"%d\"",
489				    ctx.iter->td_oncpu);
490			}
491			continue;
492
493		case XML_THREAD_NAME:
494			ctx.next_step = XML_THREAD_EXTRA;
495
496			if (ctx.iter->td_name[0] != 0)
497				name_src = ctx.iter->td_name;
498			else if (ctx.iter->td_proc != NULL &&
499			    ctx.iter->td_proc->p_comm[0] != 0)
500				name_src = ctx.iter->td_proc->p_comm;
501			else
502				continue;
503
504			qXfer_escape_xmlattr_str(td_name_escape,
505			    sizeof(td_name_escape), name_src);
506			sbuf_printf(&ctx.qXfer.sb, " name=\"%s\"",
507			    td_name_escape);
508			continue;
509
510		case XML_THREAD_EXTRA:
511			ctx.next_step = XML_END_THREAD;
512
513			sbuf_putc(&ctx.qXfer.sb, '>');
514
515			if (TD_GET_STATE(ctx.iter) == TDS_RUNNING)
516				sbuf_cat(&ctx.qXfer.sb, "Running");
517			else if (TD_GET_STATE(ctx.iter) == TDS_RUNQ)
518				sbuf_cat(&ctx.qXfer.sb, "RunQ");
519			else if (TD_GET_STATE(ctx.iter) == TDS_CAN_RUN)
520				sbuf_cat(&ctx.qXfer.sb, "CanRun");
521			else if (TD_ON_LOCK(ctx.iter))
522				sbuf_cat(&ctx.qXfer.sb, "Blocked");
523			else if (TD_IS_SLEEPING(ctx.iter))
524				sbuf_cat(&ctx.qXfer.sb, "Sleeping");
525			else if (TD_IS_SWAPPED(ctx.iter))
526				sbuf_cat(&ctx.qXfer.sb, "Swapped");
527			else if (TD_AWAITING_INTR(ctx.iter))
528				sbuf_cat(&ctx.qXfer.sb, "IthreadWait");
529			else if (TD_IS_SUSPENDED(ctx.iter))
530				sbuf_cat(&ctx.qXfer.sb, "Suspended");
531			else
532				sbuf_cat(&ctx.qXfer.sb, "???");
533			continue;
534
535		case XML_END_THREAD:
536			ctx.next_step = XML_START_THREAD;
537			sbuf_cat(&ctx.qXfer.sb, "</thread>");
538			ctx.iter = kdb_thr_next(ctx.iter);
539			continue;
540
541		/*
542		 * This one isn't part of the looping state machine,
543		 * but GCC complains if you leave an enum value out of the
544		 * select.
545		 */
546		case XML_SENT_END_THREADS:
547			/* NOTREACHED */
548			break;
549		}
550	}
551	if (ctx.qXfer.flushed)
552		return;
553
554	if (ctx.next_step != XML_SENT_END_THREADS) {
555		ctx.next_step = XML_SENT_END_THREADS;
556		sbuf_cat(&ctx.qXfer.sb, "</threads>");
557	}
558	if (ctx.qXfer.flushed)
559		return;
560
561	ctx.qXfer.lastmessage = true;
562	sbuf_finish(&ctx.qXfer.sb);
563	sbuf_delete(&ctx.qXfer.sb);
564	ctx.qXfer.last_offset = 0;
565	return;
566
567misformed_request:
568	/*
569	 * GDB "General-Query-Packets.html" qXfer-read anchor specifically
570	 * documents an E00 code for malformed requests or invalid annex.
571	 * Non-zero codes indicate invalid offset or "error reading the data."
572	 */
573	error = 0;
574request_error:
575	gdb_tx_err(error);
576	return;
577}
578
579/*
580 * A set of standardized transfers from "special data areas."
581 *
582 * We've already matched on "qXfer:" and advanced the rx packet buffer past
583 * that bit.  Parse out the rest of the packet and generate an appropriate
584 * response.
585 */
586static void
587do_qXfer(void)
588{
589	if (!gdb_rx_equal("threads:"))
590		goto unrecognized;
591
592	if (!gdb_rx_equal("read:"))
593		goto unrecognized;
594
595	do_qXfer_threads_read();
596	return;
597
598unrecognized:
599	gdb_tx_empty();
600	return;
601}
602
603static void
604gdb_handle_detach(void)
605{
606	kdb_cpu_clear_singlestep();
607	gdb_listening = 0;
608
609	if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM)
610		gdb_cur->gdb_term();
611
612#ifdef DDB
613	if (!gdb_return_to_ddb)
614		return;
615
616	gdb_return_to_ddb = false;
617
618	if (kdb_dbbe_select("ddb") != 0)
619		printf("The ddb backend could not be selected.\n");
620#endif
621}
622
623/*
624 * Handle a 'Z' packet: set a breakpoint or watchpoint.
625 *
626 * Currently, only watchpoints are supported.
627 */
628static void
629gdb_z_insert(void)
630{
631	intmax_t addr, length;
632	char ztype;
633	int error;
634
635	ztype = gdb_rx_char();
636	if (gdb_rx_char() != ',' || gdb_rx_varhex(&addr) ||
637	    gdb_rx_char() != ',' || gdb_rx_varhex(&length)) {
638		error = EINVAL;
639		goto fail;
640	}
641
642	switch (ztype) {
643	case '2': /* write watchpoint */
644		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
645		    (vm_size_t)length, KDB_DBG_ACCESS_W);
646		break;
647	case '3': /* read watchpoint */
648		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
649		    (vm_size_t)length, KDB_DBG_ACCESS_R);
650		break;
651	case '4': /* access (RW) watchpoint */
652		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
653		    (vm_size_t)length, KDB_DBG_ACCESS_RW);
654		break;
655	case '1': /* hardware breakpoint */
656#ifdef HAS_HW_BREAKPOINT
657		error = kdb_cpu_set_breakpoint((vm_offset_t)addr);
658		break;
659#endif
660	case '0': /* software breakpoint */
661		/* Not implemented. */
662		gdb_tx_empty();
663		return;
664	default:
665		error = EINVAL;
666		break;
667	}
668	if (error != 0)
669		goto fail;
670	gdb_tx_ok();
671	return;
672fail:
673	gdb_tx_err(error);
674	return;
675}
676
677/*
678 * Handle a 'z' packet; clear a breakpoint or watchpoint.
679 *
680 * Currently, only watchpoints are supported.
681 */
682static void
683gdb_z_remove(void)
684{
685	intmax_t addr, length;
686	char ztype;
687	int error;
688
689	ztype = gdb_rx_char();
690	if (gdb_rx_char() != ',' || gdb_rx_varhex(&addr) ||
691	    gdb_rx_char() != ',' || gdb_rx_varhex(&length)) {
692		error = EINVAL;
693		goto fail;
694	}
695
696	switch (ztype) {
697	case '2': /* write watchpoint */
698	case '3': /* read watchpoint */
699	case '4': /* access (RW) watchpoint */
700		error = kdb_cpu_clr_watchpoint((vm_offset_t)addr,
701		    (vm_size_t)length);
702		break;
703	case '1': /* hardware breakpoint */
704#ifdef HAS_HW_BREAKPOINT
705		error = kdb_cpu_clr_breakpoint((vm_offset_t)addr);
706		break;
707#endif
708	case '0': /* software breakpoint */
709		/* Not implemented. */
710		gdb_tx_empty();
711		return;
712	default:
713		error = EINVAL;
714		break;
715	}
716	if (error != 0)
717		goto fail;
718	gdb_tx_ok();
719	return;
720fail:
721	gdb_tx_err(error);
722	return;
723}
724
725static int
726gdb_trap(int type, int code)
727{
728	jmp_buf jb;
729	struct thread *thr_iter;
730	void *prev_jb;
731	uint32_t host_features;
732
733	prev_jb = kdb_jmpbuf(jb);
734	if (setjmp(jb) != 0) {
735		printf("%s bailing, hopefully back to ddb!\n", __func__);
736		gdb_listening = 0;
737		(void)kdb_jmpbuf(prev_jb);
738		return (1);
739	}
740
741	gdb_listening = 0;
742	gdb_ackmode = true;
743
744	/*
745	 * Send a T packet. We currently do not support watchpoints (the
746	 * awatch, rwatch or watch elements).
747	 */
748	gdb_tx_begin('T');
749	gdb_tx_hex(gdb_cpu_signal(type, code), 2);
750	gdb_tx_varhex(GDB_REG_PC);
751	gdb_tx_char(':');
752	gdb_tx_reg(GDB_REG_PC);
753	gdb_tx_char(';');
754	gdb_cpu_stop_reason(type, code);
755	gdb_tx_str("thread:");
756	gdb_tx_varhex((uintmax_t)kdb_thread->td_tid);
757	gdb_tx_char(';');
758	gdb_tx_end();			/* XXX check error condition. */
759
760	thr_iter = NULL;
761	while (gdb_rx_begin() == 0) {
762		/* printf("GDB: got '%s'\n", gdb_rxp); */
763		switch (gdb_rx_char()) {
764		case '?':	/* Last signal. */
765			gdb_tx_begin('T');
766			gdb_tx_hex(gdb_cpu_signal(type, code), 2);
767			gdb_tx_str("thread:");
768			gdb_tx_varhex((long)kdb_thread->td_tid);
769			gdb_tx_char(';');
770			gdb_tx_end();
771			break;
772		case 'c': {	/* Continue. */
773			uintmax_t addr;
774			register_t pc;
775			if (!gdb_rx_varhex(&addr)) {
776				pc = addr;
777				gdb_cpu_setreg(GDB_REG_PC, &pc);
778			}
779			kdb_cpu_clear_singlestep();
780			gdb_listening = 1;
781			return (1);
782		}
783		case 'C': {	/* Continue with signal. */
784			uintmax_t addr, sig;
785			register_t pc;
786			if (!gdb_rx_varhex(&sig) && gdb_rx_char() == ';' &&
787			    !gdb_rx_varhex(&addr)) {
788				pc = addr;
789				gdb_cpu_setreg(GDB_REG_PC, &pc);
790			}
791			kdb_cpu_clear_singlestep();
792			gdb_listening = 1;
793			return (1);
794		}
795		case 'D': {     /* Detach */
796			gdb_tx_ok();
797			gdb_handle_detach();
798			return (1);
799		}
800		case 'g': {	/* Read registers. */
801			size_t r;
802			gdb_tx_begin(0);
803			for (r = 0; r < GDB_NREGS; r++)
804				gdb_tx_reg(r);
805			gdb_tx_end();
806			break;
807		}
808		case 'G': {	/* Write registers. */
809			char *val;
810			bool success;
811			size_t r;
812			for (success = true, r = 0; r < GDB_NREGS; r++) {
813				val = gdb_rxp;
814				if (!gdb_rx_mem(val, gdb_cpu_regsz(r))) {
815					gdb_tx_err(EINVAL);
816					success = false;
817					break;
818				}
819				gdb_cpu_setreg(r, val);
820			}
821			if (success)
822				gdb_tx_ok();
823			break;
824		}
825		case 'H': {	/* Set thread. */
826			intmax_t tid;
827			struct thread *thr;
828
829			/* Ignore 'g' (general) or 'c' (continue) flag. */
830			(void) gdb_rx_char();
831
832			if (gdb_rx_varhex(&tid)) {
833				gdb_tx_err(EINVAL);
834				break;
835			}
836			if (tid > 0) {
837				thr = kdb_thr_lookup(tid);
838				if (thr == NULL) {
839					gdb_tx_err(ENOENT);
840					break;
841				}
842				kdb_thr_select(thr);
843			}
844			gdb_tx_ok();
845			break;
846		}
847		case 'k':	/* Kill request. */
848			gdb_handle_detach();
849			return (1);
850		case 'm': {	/* Read memory. */
851			uintmax_t addr, size;
852			if (gdb_rx_varhex(&addr) || gdb_rx_char() != ',' ||
853			    gdb_rx_varhex(&size)) {
854				gdb_tx_err(EINVAL);
855				break;
856			}
857			gdb_tx_begin(0);
858			if (gdb_tx_mem((char *)(uintptr_t)addr, size))
859				gdb_tx_end();
860			else
861				gdb_tx_err(EIO);
862			break;
863		}
864		case 'M': {	/* Write memory. */
865			uintmax_t addr, size;
866			if (gdb_rx_varhex(&addr) || gdb_rx_char() != ',' ||
867			    gdb_rx_varhex(&size) || gdb_rx_char() != ':') {
868				gdb_tx_err(EINVAL);
869				break;
870			}
871			if (gdb_rx_mem((char *)(uintptr_t)addr, size) == 0)
872				gdb_tx_err(EIO);
873			else
874				gdb_tx_ok();
875			break;
876		}
877		case 'p': {     /* Read register. */
878			uintmax_t reg;
879			if (gdb_rx_varhex(&reg)) {
880				gdb_tx_err(EINVAL);
881				break;
882			}
883			gdb_tx_begin(0);
884			gdb_tx_reg(reg);
885			gdb_tx_end();
886			break;
887		}
888		case 'P': {	/* Write register. */
889			char *val;
890			uintmax_t reg;
891			val = gdb_rxp;
892			if (gdb_rx_varhex(&reg) || gdb_rx_char() != '=' ||
893			    !gdb_rx_mem(val, gdb_cpu_regsz(reg))) {
894				gdb_tx_err(EINVAL);
895				break;
896			}
897			gdb_cpu_setreg(reg, val);
898			gdb_tx_ok();
899			break;
900		}
901		case 'q':	/* General query. */
902			if (gdb_rx_equal("C")) {
903				gdb_tx_begin('Q');
904				gdb_tx_char('C');
905				gdb_tx_varhex((long)kdb_thread->td_tid);
906				gdb_tx_end();
907			} else if (gdb_rx_equal("Supported")) {
908				gdb_do_qsupported(&host_features);
909			} else if (gdb_rx_equal("fThreadInfo")) {
910				thr_iter = kdb_thr_first();
911				gdb_do_threadinfo(&thr_iter);
912			} else if (gdb_rx_equal("sThreadInfo")) {
913				gdb_do_threadinfo(&thr_iter);
914			} else if (gdb_rx_equal("Xfer:")) {
915				do_qXfer();
916			} else if (gdb_rx_equal("Search:memory:")) {
917				gdb_do_mem_search();
918#ifdef __powerpc__
919			} else if (gdb_rx_equal("Offsets")) {
920				gdb_cpu_do_offsets();
921#endif
922			} else if (!gdb_cpu_query())
923				gdb_tx_empty();
924			break;
925		case 'Q':
926			if (gdb_rx_equal("StartNoAckMode")) {
927				if ((gdb_cur->gdb_dbfeatures &
928				    GDB_DBGP_FEAT_RELIABLE) == 0) {
929					/*
930					 * Shouldn't happen if we didn't
931					 * advertise support.  Reject.
932					 */
933					gdb_tx_empty();
934					break;
935				}
936				gdb_ackmode = false;
937				gdb_tx_ok();
938			} else
939				gdb_tx_empty();
940			break;
941		case 's': {	/* Step. */
942			uintmax_t addr;
943			register_t pc;
944			if (!gdb_rx_varhex(&addr)) {
945				pc = addr;
946				gdb_cpu_setreg(GDB_REG_PC, &pc);
947			}
948			kdb_cpu_set_singlestep();
949			gdb_listening = 1;
950			return (1);
951		}
952		case 'S': {	/* Step with signal. */
953			uintmax_t addr, sig;
954			register_t pc;
955			if (!gdb_rx_varhex(&sig) && gdb_rx_char() == ';' &&
956			    !gdb_rx_varhex(&addr)) {
957				pc = addr;
958				gdb_cpu_setreg(GDB_REG_PC, &pc);
959			}
960			kdb_cpu_set_singlestep();
961			gdb_listening = 1;
962			return (1);
963		}
964		case 'T': {	/* Thread alive. */
965			intmax_t tid;
966			if (gdb_rx_varhex(&tid)) {
967				gdb_tx_err(EINVAL);
968				break;
969			}
970			if (kdb_thr_lookup(tid) != NULL)
971				gdb_tx_ok();
972			else
973				gdb_tx_err(ENOENT);
974			break;
975		}
976		case 'z': {	/* Remove watchpoint. */
977			gdb_z_remove();
978			break;
979		}
980		case 'Z': {	/* Set watchpoint. */
981			gdb_z_insert();
982			break;
983		}
984		case EOF:
985			/* Empty command. Treat as unknown command. */
986			/* FALLTHROUGH */
987		default:
988			/* Unknown command. Send empty response. */
989			gdb_tx_empty();
990			break;
991		}
992	}
993	(void)kdb_jmpbuf(prev_jb);
994	return (0);
995}
996