2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 2019 Isilon Systems, LLC.
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7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
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24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * FreeBSD subsystem supporting debugging the FreeBSD kernel over the network.
32 * There are three pieces necessary to use NetGDB.
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
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).
43 * Finally, the remote (k)gdb(1) uses 'target remote <proxy>:<port>' to connect
44 * to the proxy server.
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.
52 #include <sys/cdefs.h>
55 #error "NetGDB cannot be used without DDB at this time"
58 #include <sys/errno.h>
59 #include <sys/param.h>
62 #include <sys/socket.h>
63 #include <sys/sysctl.h>
64 #include <sys/ttydefaults.h>
66 #include <machine/gdb_machdep.h>
70 #include <ddb/db_command.h>
71 #include <ddb/db_lex.h>
74 #include <net/debugnet.h>
76 #include <net/if_var.h>
77 #include <net/route.h>
80 #include <gdb/gdb_int.h>
81 #include <gdb/netgdb.h>
83 FEATURE(netgdb, "NetGDB support");
84 SYSCTL_NODE(_debug_gdb, OID_AUTO, netgdb, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
87 static unsigned netgdb_debug;
88 SYSCTL_UINT(_debug_gdb_netgdb, OID_AUTO, debug, CTLFLAG_RWTUN,
90 "Debug message verbosity (0: off; 1: on)");
92 #define NETGDB_DEBUG(f, ...) do { \
93 if (netgdb_debug > 0) \
94 printf(("%s [%s:%d]: " f), __func__, __FILE__, __LINE__, ## \
98 static void netgdb_fini(void);
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;
105 static struct debugnet_pcb *netgdb_conn;
106 static struct gdb_dbgport *netgdb_prev_dbgport;
107 static int *netgdb_prev_kdb_inactive;
109 /* TODO(CEM) disable ack mode */
112 * Attempt to accept the incoming packet. If we run into ENOBUFS or another
115 * The mbuf chain will have all framing headers removed (ethernet, inet, udp,
119 netgdb_rx(struct mbuf *m)
121 uint32_t rlen, count;
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);
131 #undef _SBUF_FREESPACE
134 * Inlined m_apply -- why isn't there a macro or inline function
137 while (m != NULL && m->m_len == 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);
152 sbuf_putc(&netgdb_rxsb, CTRL('C'));
156 * The following routines implement a pseudo GDB debugport (an emulated serial
157 * driver that the MI gdb(4) code does I/O with).
161 netgdb_dbg_getc(void)
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];
173 /* Reached EOF? Reuse buffer. */
174 sbuf_clear(&netgdb_rxsb);
177 /* Check for CTRL-C on console/serial, if any. */
178 if (netgdb_prev_dbgport != NULL) {
179 c = netgdb_prev_dbgport->gdb_getc();
184 debugnet_network_poll(netgdb_conn);
187 if (c == CTRL('C')) {
189 /* Caller gdb_getc() will print that we got ^C. */
195 netgdb_dbg_sendpacket(const void *buf, size_t len)
197 struct debugnet_proto_aux aux;
200 MPASS(len <= UINT32_MAX);
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.
207 aux = (struct debugnet_proto_aux) {
211 error = debugnet_send(netgdb_conn, DEBUGNET_DATA, buf, len, &aux);
213 printf("%s: Network error: %d; trying to switch back to ddb.\n",
217 if (kdb_dbbe_select("ddb") != 0)
218 printf("The ddb backend could not be selected.\n");
220 printf("using longjmp, hope it works!\n");
227 /* Just used for + / - GDB-level ACKs. */
229 netgdb_dbg_putc(int i)
234 netgdb_dbg_sendpacket(&c, 1);
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,
250 struct kdb_dbbe *be, **iter;
253 * Force enable GDB. (If no other debugports were registered at boot,
254 * KDB thinks it doesn't exist.)
256 SET_FOREACH(iter, kdb_dbbe_set) {
258 if (strcmp(be->dbbe_name, "gdb") != 0)
260 if (be->dbbe_active == -1) {
261 netgdb_prev_kdb_inactive = &be->dbbe_active;
267 /* Force netgdb debugport. */
268 netgdb_prev_dbgport = gdb_cur;
269 gdb_cur = &netgdb_gdb_dbgport;
271 sbuf_new(&netgdb_rxsb, netgdb_rxbuf, sizeof(netgdb_rxbuf),
280 /* TODO: tear down conn gracefully? */
281 if (netgdb_conn != NULL) {
282 debugnet_free(netgdb_conn);
286 sbuf_delete(&netgdb_rxsb);
288 gdb_cur = netgdb_prev_dbgport;
290 if (netgdb_prev_kdb_inactive != NULL) {
291 *netgdb_prev_kdb_inactive = -1;
292 netgdb_prev_kdb_inactive = NULL;
298 * Usage: netgdb -s <server> [-g <gateway -c <localip> -i <interface>]
300 * Order is not significant.
302 * Currently, this command does not support configuring encryption or
305 DB_COMMAND_FLAGS(netgdb, db_netgdb_cmd, CS_OWN)
307 struct debugnet_ddb_config params;
308 struct debugnet_conn_params dcp;
309 struct debugnet_pcb *pcb;
310 char proxy_buf[INET_ADDRSTRLEN];
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__);
320 error = debugnet_parse_ddb_cmd("netgdb", ¶ms);
322 db_printf("Error configuring netgdb: %d\n", error);
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().
333 if (!params.dd_has_client)
334 params.dd_client = INADDR_ANY;
335 if (!params.dd_has_gateway)
336 params.dd_gateway = INADDR_ANY;
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,
350 error = debugnet_connect(&dcp, &pcb);
352 printf("failed to contact netgdb server: %d\n", error);
359 if (kdb_dbbe_select("gdb") != 0) {
360 db_printf("The remote GDB backend could not be selected.\n");
366 * Mark that we are done in ddb(4). Return -> kdb_trap() should
367 * re-enter with the new backend.
369 db_cmd_loop_done = 1;
370 gdb_return_to_ddb = true;
371 db_printf("(detaching GDB will return control to DDB)\n");
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",
381 db_printf("Connected to proxy. "
382 "Use target remote %s:%hu to begin debugging.\n",
383 proxy_buf, proxy_port);
386 /* Aspirational, but does not work reliably. */
387 db_printf("(ctrl-c will return control to ddb)\n");