1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2019 Isilon Systems, LLC.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 /*
29 * netgdb.c
30 * FreeBSD subsystem supporting debugging the FreeBSD kernel over the network.
31 *
32 * There are three pieces necessary to use NetGDB.
33 *
34 * First, a dedicated proxy server must be running to accept connections from
35 * both NetGDB and gdb(1), and pass bidirectional traffic between the two
36 * protocols.
37 *
38 * Second, The NetGDB client is activated much like ordinary 'gdb' and
39 * similarly to 'netdump' in ddb(4). Like other debugnet(4) clients
40 * (netdump(4)), the network interface on the route to the proxy server must be
41 * online and support debugnet(4).
42 *
43 * Finally, the remote (k)gdb(1) uses 'target remote <proxy>:<port>' to connect
44 * to the proxy server.
45 *
46 * NetGDBv1 speaks the literal GDB remote serial protocol, and uses a 1:1
47 * relationship between GDB packets and plain debugnet packets. There is no
48 * encryption utilized to keep debugging sessions private, so this is only
49 * appropriate for local segments or trusted networks.
50 */
51
52 #include <sys/cdefs.h>
53 #include "opt_ddb.h"
54 #ifndef DDB
55 #error "NetGDB cannot be used without DDB at this time"
56 #endif
57
58 #include <sys/errno.h>
59 #include <sys/param.h>
60 #include <sys/kdb.h>
61 #include <sys/sbuf.h>
62 #include <sys/socket.h>
63 #include <sys/sysctl.h>
64 #include <sys/ttydefaults.h>
65
66 #include <machine/gdb_machdep.h>
67
68 #ifdef DDB
69 #include <ddb/ddb.h>
70 #include <ddb/db_command.h>
71 #include <ddb/db_lex.h>
72 #endif
73
74 #include <net/debugnet.h>
75 #include <net/if.h>
76 #include <net/if_var.h>
77 #include <net/route.h>
78
79 #include <gdb/gdb.h>
80 #include <gdb/gdb_int.h>
81 #include <gdb/netgdb.h>
82
83 FEATURE(netgdb, "NetGDB support");
84 SYSCTL_NODE(_debug_gdb, OID_AUTO, netgdb, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
85 "NetGDB parameters");
86
87 static unsigned netgdb_debug;
88 SYSCTL_UINT(_debug_gdb_netgdb, OID_AUTO, debug, CTLFLAG_RWTUN,
89 &netgdb_debug, 0,
90 "Debug message verbosity (0: off; 1: on)");
91
92 #define NETGDB_DEBUG(f, ...) do { \
93 if (netgdb_debug > 0) \
94 printf(("%s [%s:%d]: " f), __func__, __FILE__, __LINE__, ## \
95 __VA_ARGS__); \
96 } while (false)
97
98 static void netgdb_fini(void);
99
100 /* Runtime state. */
101 static char netgdb_rxbuf[GDB_BUFSZ + 16]; /* Some overhead for framing. */
102 static struct sbuf netgdb_rxsb;
103 static ssize_t netgdb_rx_off;
104
105 static struct debugnet_pcb *netgdb_conn;
106 static struct gdb_dbgport *netgdb_prev_dbgport;
107 static int *netgdb_prev_kdb_inactive;
108
109 /* TODO(CEM) disable ack mode */
110
111 /*
112 * Attempt to accept the incoming packet. If we run into ENOBUFS or another
113 * error, return it.
114 *
115 * The mbuf chain will have all framing headers removed (ethernet, inet, udp,
116 * debugnet).
117 */
118 static int
netgdb_rx(struct mbuf * m)119 netgdb_rx(struct mbuf *m)
120 {
121 uint32_t rlen, count;
122
123 rlen = m->m_pkthdr.len;
124 #define _SBUF_FREESPACE(s) ((s)->s_size - ((s)->s_len + 1))
125 if (_SBUF_FREESPACE(&netgdb_rxsb) < rlen) {
126 NETGDB_DEBUG("Backpressure: Not ACKing RX of packet that "
127 "would overflow our buffer (%zd/%zd used).\n",
128 netgdb_rxsb.s_len, netgdb_rxsb.s_size);
129 return (ENOBUFS);
130 }
131 #undef _SBUF_FREESPACE
132
133 /*
134 * Inlined m_apply -- why isn't there a macro or inline function
135 * version?
136 */
137 while (m != NULL && m->m_len == 0)
138 m = m->m_next;
139 while (rlen > 0) {
140 MPASS(m != NULL && m->m_len >= 0);
141 count = min((uint32_t)m->m_len, rlen);
142 (void)sbuf_bcat(&netgdb_rxsb, mtod(m, const void *), count);
143 rlen -= count;
144 m = m->m_next;
145 }
146 return (0);
147 }
148
149 static void
netgdb_finish(void)150 netgdb_finish(void)
151 {
152 sbuf_putc(&netgdb_rxsb, CTRL('C'));
153 }
154
155 /*
156 * The following routines implement a pseudo GDB debugport (an emulated serial
157 * driver that the MI gdb(4) code does I/O with).
158 */
159
160 static int
netgdb_dbg_getc(void)161 netgdb_dbg_getc(void)
162 {
163 int c;
164
165 while (true) {
166 /* Pull bytes off any currently cached packet first. */
167 if (netgdb_rx_off < sbuf_len(&netgdb_rxsb)) {
168 c = netgdb_rxsb.s_buf[netgdb_rx_off];
169 netgdb_rx_off++;
170 break;
171 }
172
173 /* Reached EOF? Reuse buffer. */
174 sbuf_clear(&netgdb_rxsb);
175 netgdb_rx_off = 0;
176
177 /* Check for CTRL-C on console/serial, if any. */
178 if (netgdb_prev_dbgport != NULL) {
179 c = netgdb_prev_dbgport->gdb_getc();
180 if (c == CTRL('C'))
181 break;
182 }
183
184 debugnet_network_poll(netgdb_conn);
185 }
186
187 if (c == CTRL('C')) {
188 netgdb_fini();
189 /* Caller gdb_getc() will print that we got ^C. */
190 }
191 return (c);
192 }
193
194 static void
netgdb_dbg_sendpacket(const void * buf,size_t len)195 netgdb_dbg_sendpacket(const void *buf, size_t len)
196 {
197 struct debugnet_proto_aux aux;
198 int error;
199
200 MPASS(len <= UINT32_MAX);
201
202 /*
203 * GDB packet boundaries matter. debugnet_send() fragments a single
204 * request into many sequential debugnet messages. Mark full packet
205 * length and offset for potential reassembly by the proxy.
206 */
207 aux = (struct debugnet_proto_aux) {
208 .dp_aux2 = len,
209 };
210
211 error = debugnet_send(netgdb_conn, DEBUGNET_DATA, buf, len, &aux);
212 if (error != 0) {
213 printf("%s: Network error: %d; trying to switch back to ddb.\n",
214 __func__, error);
215 netgdb_fini();
216
217 if (kdb_dbbe_select("ddb") != 0)
218 printf("The ddb backend could not be selected.\n");
219 else {
220 printf("using longjmp, hope it works!\n");
221 kdb_reenter();
222 }
223 }
224
225 }
226
227 /* Just used for + / - GDB-level ACKs. */
228 static void
netgdb_dbg_putc(int i)229 netgdb_dbg_putc(int i)
230 {
231 char c;
232
233 c = i;
234 netgdb_dbg_sendpacket(&c, 1);
235
236 }
237
238 static struct gdb_dbgport netgdb_gdb_dbgport = {
239 .gdb_name = "netgdb",
240 .gdb_getc = netgdb_dbg_getc,
241 .gdb_putc = netgdb_dbg_putc,
242 .gdb_term = netgdb_fini,
243 .gdb_sendpacket = netgdb_dbg_sendpacket,
244 .gdb_dbfeatures = GDB_DBGP_FEAT_WANTTERM | GDB_DBGP_FEAT_RELIABLE,
245 };
246
247 static void
netgdb_init(void)248 netgdb_init(void)
249 {
250 struct kdb_dbbe *be, **iter;
251
252 /*
253 * Force enable GDB. (If no other debugports were registered at boot,
254 * KDB thinks it doesn't exist.)
255 */
256 SET_FOREACH(iter, kdb_dbbe_set) {
257 be = *iter;
258 if (strcmp(be->dbbe_name, "gdb") != 0)
259 continue;
260 if (be->dbbe_active == -1) {
261 netgdb_prev_kdb_inactive = &be->dbbe_active;
262 be->dbbe_active = 0;
263 }
264 break;
265 }
266
267 /* Force netgdb debugport. */
268 netgdb_prev_dbgport = gdb_cur;
269 gdb_cur = &netgdb_gdb_dbgport;
270
271 sbuf_new(&netgdb_rxsb, netgdb_rxbuf, sizeof(netgdb_rxbuf),
272 SBUF_FIXEDLEN);
273 netgdb_rx_off = 0;
274 }
275
276 static void
netgdb_fini(void)277 netgdb_fini(void)
278 {
279
280 /* TODO: tear down conn gracefully? */
281 if (netgdb_conn != NULL) {
282 debugnet_free(netgdb_conn);
283 netgdb_conn = NULL;
284 }
285
286 sbuf_delete(&netgdb_rxsb);
287
288 gdb_cur = netgdb_prev_dbgport;
289
290 if (netgdb_prev_kdb_inactive != NULL) {
291 *netgdb_prev_kdb_inactive = -1;
292 netgdb_prev_kdb_inactive = NULL;
293 }
294 }
295
296 #ifdef DDB
297 /*
298 * Usage: netgdb -s <server> [-g <gateway -c <localip> -i <interface>]
299 *
300 * Order is not significant.
301 *
302 * Currently, this command does not support configuring encryption or
303 * compression.
304 */
DB_COMMAND_FLAGS(netgdb,db_netgdb_cmd,CS_OWN)305 DB_COMMAND_FLAGS(netgdb, db_netgdb_cmd, CS_OWN)
306 {
307 struct debugnet_ddb_config params;
308 struct debugnet_conn_params dcp;
309 struct debugnet_pcb *pcb;
310 char proxy_buf[INET_ADDRSTRLEN];
311 int error;
312
313 if (!KERNEL_PANICKED()) {
314 /* TODO: This limitation should be removed in future work. */
315 printf("%s: netgdb is currently limited to use only after a "
316 "panic. Sorry.\n", __func__);
317 return;
318 }
319
320 error = debugnet_parse_ddb_cmd("netgdb", ¶ms);
321 if (error != 0) {
322 db_printf("Error configuring netgdb: %d\n", error);
323 return;
324 }
325
326 /*
327 * Must initialize netgdb_rxsb before debugnet_connect(), because we
328 * might be getting rx handler callbacks from the send->poll path
329 * during debugnet_connect().
330 */
331 netgdb_init();
332
333 if (!params.dd_has_client)
334 params.dd_client = INADDR_ANY;
335 if (!params.dd_has_gateway)
336 params.dd_gateway = INADDR_ANY;
337
338 dcp = (struct debugnet_conn_params) {
339 .dc_ifp = params.dd_ifp,
340 .dc_client = params.dd_client,
341 .dc_server = params.dd_server,
342 .dc_gateway = params.dd_gateway,
343 .dc_herald_port = NETGDB_HERALDPORT,
344 .dc_client_port = NETGDB_CLIENTPORT,
345 .dc_herald_aux2 = NETGDB_PROTO_V1,
346 .dc_rx_handler = netgdb_rx,
347 .dc_finish_handler = netgdb_finish,
348 };
349
350 error = debugnet_connect(&dcp, &pcb);
351 if (error != 0) {
352 printf("failed to contact netgdb server: %d\n", error);
353 netgdb_fini();
354 return;
355 }
356
357 netgdb_conn = pcb;
358
359 if (kdb_dbbe_select("gdb") != 0) {
360 db_printf("The remote GDB backend could not be selected.\n");
361 netgdb_fini();
362 return;
363 }
364
365 /*
366 * Mark that we are done in ddb(4). Return -> kdb_trap() should
367 * re-enter with the new backend.
368 */
369 db_cmd_loop_done = 1;
370 gdb_return_to_ddb = true;
371 db_printf("(detaching GDB will return control to DDB)\n");
372
373 const in_addr_t *proxy_addr = debugnet_get_server_addr(netgdb_conn);
374 const uint16_t proxy_port = debugnet_get_server_port(netgdb_conn) + 1;
375 inet_ntop(AF_INET, proxy_addr, proxy_buf, sizeof(proxy_buf));
376 if (inet_ntop(AF_INET, proxy_addr, proxy_buf, sizeof(proxy_buf)) == NULL) {
377 db_printf("Connected to proxy. "
378 "Use target remote <proxy address>:%hu to begin debugging.\n",
379 proxy_port);
380 } else {
381 db_printf("Connected to proxy. "
382 "Use target remote %s:%hu to begin debugging.\n",
383 proxy_buf, proxy_port);
384 }
385 #if 0
386 /* Aspirational, but does not work reliably. */
387 db_printf("(ctrl-c will return control to ddb)\n");
388 #endif
389 }
390 #endif /* DDB */
391