/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2019 Isilon Systems, LLC.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* netgdb.c
* FreeBSD subsystem supporting debugging the FreeBSD kernel over the network.
*
* There are three pieces necessary to use NetGDB.
*
* First, a dedicated proxy server must be running to accept connections from
* both NetGDB and gdb(1), and pass bidirectional traffic between the two
* protocols.
*
* Second, The NetGDB client is activated much like ordinary 'gdb' and
* similarly to 'netdump' in ddb(4). Like other debugnet(4) clients
* (netdump(4)), the network interface on the route to the proxy server must be
* online and support debugnet(4).
*
* Finally, the remote (k)gdb(1) uses 'target remote <proxy>:<port>' to connect
* to the proxy server.
*
* NetGDBv1 speaks the literal GDB remote serial protocol, and uses a 1:1
* relationship between GDB packets and plain debugnet packets. There is no
* encryption utilized to keep debugging sessions private, so this is only
* appropriate for local segments or trusted networks.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#ifndef DDB
#error "NetGDB cannot be used without DDB at this time"
#endif
#include <sys/param.h>
#include <sys/kdb.h>
#include <sys/sbuf.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/ttydefaults.h>
#include <machine/gdb_machdep.h>
#ifdef DDB
#include <ddb/ddb.h>
#include <ddb/db_command.h>
#include <ddb/db_lex.h>
#endif
#include <net/debugnet.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/route.h>
#include <gdb/gdb.h>
#include <gdb/gdb_int.h>
#include <gdb/netgdb.h>
FEATURE(netgdb, "NetGDB support");
SYSCTL_NODE(_debug_gdb, OID_AUTO, netgdb, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
"NetGDB parameters");
static unsigned netgdb_debug;
SYSCTL_UINT(_debug_gdb_netgdb, OID_AUTO, debug, CTLFLAG_RWTUN,
&netgdb_debug, 0,
"Debug message verbosity (0: off; 1: on)");
#define NETGDB_DEBUG(f, ...) do { \
if (netgdb_debug > 0) \
printf(("%s [%s:%d]: " f), __func__, __FILE__, __LINE__, ## \
__VA_ARGS__); \
} while (false)
static void netgdb_fini(void);
/* Runtime state. */
static char netgdb_rxbuf[GDB_BUFSZ + 16]; /* Some overhead for framing. */
static struct sbuf netgdb_rxsb;
static ssize_t netgdb_rx_off;
static struct debugnet_pcb *netgdb_conn;
static struct gdb_dbgport *netgdb_prev_dbgport;
static int *netgdb_prev_kdb_inactive;
/* TODO(CEM) disable ack mode */
/*
* Receive non-TX ACK packets on the client port.
*
* The mbuf chain will have all non-debugnet framing headers removed
* (ethernet, inet, udp). It will start with a debugnet_msg_hdr, of
* which the header is guaranteed to be contiguous. If m_pullup is
* used, the supplied in-out mbuf pointer should be updated
* appropriately.
*
* If the handler frees the mbuf chain, it should set the mbuf pointer
* to NULL. Otherwise, the debugnet input framework will free the
* chain.
*/
static void
netgdb_rx(struct debugnet_pcb *pcb, struct mbuf **mb)
{
const struct debugnet_msg_hdr *dnh;
struct mbuf *m;
uint32_t rlen, count;
int error;
m = *mb;
dnh = mtod(m, const void *);
if (ntohl(dnh->mh_type) == DEBUGNET_FINISHED) {
sbuf_putc(&netgdb_rxsb, CTRL('C'));
return;
}
if (ntohl(dnh->mh_type) != DEBUGNET_DATA) {
printf("%s: Got unexpected debugnet message %u\n",
__func__, ntohl(dnh->mh_type));
return;
}
rlen = ntohl(dnh->mh_len);
#define _SBUF_FREESPACE(s) ((s)->s_size - ((s)->s_len + 1))
if (_SBUF_FREESPACE(&netgdb_rxsb) < rlen) {
NETGDB_DEBUG("Backpressure: Not ACKing RX of packet that "
"would overflow our buffer (%zd/%zd used).\n",
netgdb_rxsb.s_len, netgdb_rxsb.s_size);
return;
}
#undef _SBUF_FREESPACE
error = debugnet_ack_output(pcb, dnh->mh_seqno);
if (error != 0) {
printf("%s: Couldn't ACK rx packet %u; %d\n", __func__,
ntohl(dnh->mh_seqno), error);
/*
* Sender will re-xmit, and assuming the condition is
* transient, we'll process the packet's contentss later.
*/
return;
}
m_adj(m, sizeof(*dnh));
dnh = NULL;
/*
* Inlined m_apply -- why isn't there a macro or inline function
* version?
*/
while (m != NULL && m->m_len == 0)
m = m->m_next;
while (rlen > 0) {
MPASS(m != NULL && m->m_len >= 0);
count = min((uint32_t)m->m_len, rlen);
(void)sbuf_bcat(&netgdb_rxsb, mtod(m, const void *), count);
rlen -= count;
m = m->m_next;
}
}
/*
* The following routines implement a pseudo GDB debugport (an emulated serial
* driver that the MI gdb(4) code does I/O with).
*/
static int
netgdb_dbg_getc(void)
{
int c;
while (true) {
/* Pull bytes off any currently cached packet first. */
if (netgdb_rx_off < sbuf_len(&netgdb_rxsb)) {
c = netgdb_rxsb.s_buf[netgdb_rx_off];
netgdb_rx_off++;
break;
}
/* Reached EOF? Reuse buffer. */
sbuf_clear(&netgdb_rxsb);
netgdb_rx_off = 0;
/* Check for CTRL-C on console/serial, if any. */
if (netgdb_prev_dbgport != NULL) {
c = netgdb_prev_dbgport->gdb_getc();
if (c == CTRL('C'))
break;
}
debugnet_network_poll(netgdb_conn);
}
if (c == CTRL('C')) {
netgdb_fini();
/* Caller gdb_getc() will print that we got ^C. */
}
return (c);
}
static void
netgdb_dbg_sendpacket(const void *buf, size_t len)
{
struct debugnet_proto_aux aux;
int error;
MPASS(len <= UINT32_MAX);
/*
* GDB packet boundaries matter. debugnet_send() fragments a single
* request into many sequential debugnet messages. Mark full packet
* length and offset for potential reassembly by the proxy.
*/
aux = (struct debugnet_proto_aux) {
.dp_aux2 = len,
};
error = debugnet_send(netgdb_conn, DEBUGNET_DATA, buf, len, &aux);
if (error != 0) {
printf("%s: Network error: %d; trying to switch back to ddb.\n",
__func__, error);
netgdb_fini();
if (kdb_dbbe_select("ddb") != 0)
printf("The ddb backend could not be selected.\n");
else {
printf("using longjmp, hope it works!\n");
kdb_reenter();
}
}
}
/* Just used for + / - GDB-level ACKs. */
static void
netgdb_dbg_putc(int i)
{
char c;
c = i;
netgdb_dbg_sendpacket(&c, 1);
}
static struct gdb_dbgport netgdb_gdb_dbgport = {
.gdb_name = "netgdb",
.gdb_getc = netgdb_dbg_getc,
.gdb_putc = netgdb_dbg_putc,
.gdb_term = netgdb_fini,
.gdb_sendpacket = netgdb_dbg_sendpacket,
.gdb_dbfeatures = GDB_DBGP_FEAT_WANTTERM | GDB_DBGP_FEAT_RELIABLE,
};
static void
netgdb_init(void)
{
struct kdb_dbbe *be, **iter;
/*
* Force enable GDB. (If no other debugports were registered at boot,
* KDB thinks it doesn't exist.)
*/
SET_FOREACH(iter, kdb_dbbe_set) {
be = *iter;
if (strcmp(be->dbbe_name, "gdb") != 0)
continue;
if (be->dbbe_active == -1) {
netgdb_prev_kdb_inactive = &be->dbbe_active;
be->dbbe_active = 0;
}
break;
}
/* Force netgdb debugport. */
netgdb_prev_dbgport = gdb_cur;
gdb_cur = &netgdb_gdb_dbgport;
sbuf_new(&netgdb_rxsb, netgdb_rxbuf, sizeof(netgdb_rxbuf),
SBUF_FIXEDLEN);
netgdb_rx_off = 0;
}
static void
netgdb_fini(void)
{
/* TODO: tear down conn gracefully? */
if (netgdb_conn != NULL) {
debugnet_free(netgdb_conn);
netgdb_conn = NULL;
}
sbuf_delete(&netgdb_rxsb);
gdb_cur = netgdb_prev_dbgport;
if (netgdb_prev_kdb_inactive != NULL) {
*netgdb_prev_kdb_inactive = -1;
netgdb_prev_kdb_inactive = NULL;
}
}
#ifdef DDB
/*
* Usage: netgdb -s <server> [-g <gateway -c <localip> -i <interface>]
*
* Order is not significant.
*
* Currently, this command does not support configuring encryption or
* compression.
*/
DB_COMMAND_FLAGS(netgdb, db_netgdb_cmd, CS_OWN)
{
struct debugnet_ddb_config params;
struct debugnet_conn_params dcp;
struct debugnet_pcb *pcb;
int error;
if (!KERNEL_PANICKED()) {
/* TODO: This limitation should be removed in future work. */
printf("%s: netgdb is currently limited to use only after a "
"panic. Sorry.\n", __func__);
return;
}
error = debugnet_parse_ddb_cmd("netgdb", ¶ms);
if (error != 0) {
db_printf("Error configuring netgdb: %d\n", error);
return;
}
/*
* Must initialize netgdb_rxsb before debugnet_connect(), because we
* might be getting rx handler callbacks from the send->poll path
* during debugnet_connect().
*/
netgdb_init();
if (!params.dd_has_client)
params.dd_client = INADDR_ANY;
if (!params.dd_has_gateway)
params.dd_gateway = INADDR_ANY;
dcp = (struct debugnet_conn_params) {
.dc_ifp = params.dd_ifp,
.dc_client = params.dd_client,
.dc_server = params.dd_server,
.dc_gateway = params.dd_gateway,
.dc_herald_port = NETGDB_HERALDPORT,
.dc_client_port = NETGDB_CLIENTPORT,
.dc_herald_aux2 = NETGDB_PROTO_V1,
.dc_rx_handler = netgdb_rx,
};
error = debugnet_connect(&dcp, &pcb);
if (error != 0) {
printf("failed to contact netgdb server: %d\n", error);
netgdb_fini();
return;
}
netgdb_conn = pcb;
if (kdb_dbbe_select("gdb") != 0) {
db_printf("The remote GDB backend could not be selected.\n");
netgdb_fini();
return;
}
/*
* Mark that we are done in ddb(4). Return -> kdb_trap() should
* re-enter with the new backend.
*/
db_cmd_loop_done = 1;
gdb_return_to_ddb = true;
db_printf("(detaching GDB will return control to DDB)\n");
#if 0
/* Aspirational, but does not work reliably. */
db_printf("(ctrl-c will return control to ddb)\n");
#endif
}
#endif /* DDB */
