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Implement NetGDB(4)

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NetGDB(4) is a component of a system using a panic-time network stack to
remotely debug crashed FreeBSD kernels over the network, instead of
traditional serial interfaces.

There are three pieces in the complete NetGDB system.

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) after a panic.  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>' (like any
other TCP remote) to connect to the proxy server.

The NetGDB v1 protocol speaks the literal GDB remote serial protocol, and
uses a 1:1 relationship between GDB packets and sequences of debugnet
packets (fragmented by MTU).  There is no encryption utilized to keep
debugging sessions private, so this is only appropriate for local
segments or trusted networks.

Submitted by:	John Reimer <john.reimer AT emc.com> (earlier version)
Discussed some with:	emaste, markj
Relnotes:	sure
Differential Revision:	https://reviews.freebsd.org/D21568
This commit is contained in:
Conrad Meyer 2019-10-17 21:33:01 +00:00
parent 092bacb2c4
commit dda17b3672
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=353700
21 changed files with 757 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
share/man/man4/Makefile
View File

@ -307,6 +307,7 @@ MAN= aac.4 \
net80211.4 \
netdump.4 \
netfpga10g_nf10bmac.4 \
netgdb.4 \
netgraph.4 \
netintro.4 \
netmap.4 \

9
share/man/man4/ddb.4
View File

@ -1211,6 +1211,15 @@ Finally, the
.Ic netdump
command does not provide any way to configure compression or encryption.
.Pp
.It Ic netgdb Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc
Initiate a
.Xr netgdb 4
session with the provided parameters.
.Pp
.Ic netgdb
has identical limitations to
.Ic netdump .
.Pp
.It Ic capture on
.It Ic capture off
.It Ic capture reset

147
share/man/man4/netgdb.4 Normal file
View File

@ -0,0 +1,147 @@
.\"-
.\" Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org>
.\"
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd October 17, 2019
.Dt NETGDB 4
.Os
.Sh NAME
.Nm netgdb
.Nd protocol for debugging the kernel with GDB over the network
.Sh SYNOPSIS
NetGDB support is compiled by default, if DDB, GDB, and INET are enabled.
To build a kernel without it, add the following line to your kernel
configuration file:
.Bd -ragged -offset indent
.Cd "nooptions NETGDB"
.Ed
.Sh DESCRIPTION
.Nm
is a UDP-based protocol for communicating with a remote GDB client via an
intermediary proxy.
.Pp
A
.Nm
session is started by using the
.Ic netgdb Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc
command in
.Xr ddb 4
to connect to a proxy server.
When the connection is made, the proxy server logs a message that a
.Nm
client has connected.
It subsequently establishes a TCP listening socket and logs a message
specifying which port it is listening on.
Then it waits for a GDB client to connect.
The GDB command to connect is:
.Bd -ragged -offset indent
.Ic target remote Aq Ar proxyip:proxyport
.Ed
.Pp
At this point, the server proxies traffic back and forth between
.Nm
and the ordinary GDB client, speaking the ordinary GDB remote protocol.
The
.Nm
session is identical to any other kernel GDB sesssion from the perspective
of the GDB debugger.
.Sh IMPLEMENTATION NOTES
The UDP protocol is based on the same packet structure and a subset of the
exact same message types as
.Xr netdump 4 .
It uses the
.Dv HERALD ,
.Dv DATA ( née VMCORE ) ,
and
.Dv FINISHED
message types.
Like
.Xr netdump 4 ,
the client's initial
.Dv HERALD
message is acknowledged from a random source port, and the client sends
subsequent communication to that port.
.Pp
Unlike
.Xr netdump 4 ,
the initial
.Dv HERALD
port is 20025.
Additionally,
the proxy server sends responses to the source port of the client's initial
.Dv HERALD ,
rather than a separate reserved port.
.Nm
message and acknowledgements are bidirectional.
The sequence number and acknowledgement protocol is otherwise identical to
the unidirectional version used by netdump; it just runs in both directions.
Acknowledgements are sent to and from the same addresses and ports as
regular messages.
.Pp
The first version of the
.Nm
protocol uses the protocol number
.Dv Sq 0x2515f095
in the 32-bit
.Va aux2
parameter of the initial
.Dv HERALD
message.
.Pp
The list of supported network drivers and protocol families is identical to
that of
.Xr netdump 4 .
.Sh DIAGNOSTICS
The following variable is available via both
.Xr sysctl 8
and
.Xr loader 8
(as a tunable):
.Bl -tag -width "indent"
.It Va debug.gdb.netgdb.debug
Control debug message verbosity.
Debug messages are disabled by default.
They may be enabled by setting the variable to a non-zero value.
.El
.Sh SEE ALSO
.Xr ddb 4 ,
.Xr gdb 4 ,
.Xr netdump 4
.Sh HISTORY
.Nm
first appeared in
.Fx 13.0 .
.Sh BUGS
.Nm
may only be used after the kernel has panicked, due to limitations in the
treatment of locking primitives under
.Xr ddb 4 .
.Sh SECURITY CONSIDERATIONS
Version 1 of the
.Nm
protocol has no security properties whatsoever.
All messages are sent and acknowledged in cleartext, and no message
authentication codes are used to prevent attackers from forging messages.
It is absolutely inappropriate for use across the public internet.

1
sys/amd64/conf/GENERIC
View File

@ -113,6 +113,7 @@ options GZIO # gzip-compressed kernel and user dumps
options ZSTDIO # zstd-compressed kernel and user dumps
options DEBUGNET # debugnet networking
options NETDUMP # netdump(4) client support
options NETGDB # netgdb(4) client support
# Make an SMP-capable kernel by default
options SMP # Symmetric MultiProcessor Kernel

10
sys/conf/NOTES
View File

@ -1038,13 +1038,17 @@ options TCP_SIGNATURE #include support for RFC 2385
# a smooth scheduling of the traffic.
options DUMMYNET
# The DEBUGNET option enables a basic debug/panic-time networking API. It
# is used by NETDUMP and NETGDB.
options DEBUGNET
# The NETDUMP option enables netdump(4) client support in the kernel.
# This allows a panicking kernel to transmit a kernel dump to a remote host.
options NETDUMP
# The DEBUGNET option enables a basic debug/panic-time networking API. It
# is used by NETDUMP.
options DEBUGNET
# The NETGDB option enables netgdb(4) support in the kernel. This allows a
# panicking kernel to be debugged as a GDB remote over the network.
options NETGDB
#####################################################################
# FILESYSTEM OPTIONS

1
sys/conf/files
View File

@ -3546,6 +3546,7 @@ fs/tmpfs/tmpfs_subr.c optional tmpfs
gdb/gdb_cons.c optional gdb
gdb/gdb_main.c optional gdb
gdb/gdb_packet.c optional gdb
gdb/netgdb.c optional ddb debugnet gdb netgdb inet
geom/bde/g_bde.c optional geom_bde
geom/bde/g_bde_crypt.c optional geom_bde
geom/bde/g_bde_lock.c optional geom_bde

6
sys/conf/options
View File

@ -319,10 +319,12 @@ NFS_ROOT opt_nfsroot.h
# SMB/CIFS requester
NETSMB opt_netsmb.h
# Enable netdump(4) client support.
NETDUMP opt_global.h
# Enable debugnet(4) networking support.
DEBUGNET opt_global.h
# Enable netdump(4) client support.
NETDUMP opt_global.h
# Enable netgdb(4) support.
NETGDB opt_global.h
# Options used only in subr_param.c.
HZ opt_param.h

8
sys/gdb/gdb.h
View File

@ -46,8 +46,16 @@ struct gdb_dbgport {
gdb_putc_f *gdb_putc;
gdb_term_f *gdb_term;
int gdb_active;
void (*gdb_sendpacket)(const void *, size_t);
int gdb_dbfeatures;
};
#define GDB_DBGP_FEAT_WANTTERM 0x1 /* Want gdb_term() invocation when
leaving GDB. gdb_term has been
deadcode and never invoked for so
long I don't want to just blindly
start invoking it without opt-in. */
#define GDB_DBGPORT(name, probe, init, term, getc, putc) \
static struct gdb_dbgport name##_gdb_dbgport = { \
.gdb_name = #name, \

11
sys/gdb/gdb_int.h
View File

@ -31,8 +31,14 @@
#ifndef _GDB_GDB_INT_H_
#define _GDB_GDB_INT_H_
#include "opt_ddb.h"
#include <sys/sysctl.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#ifndef EOF
#define EOF (-1)
#endif
@ -48,6 +54,11 @@ extern char *gdb_rxp;
extern size_t gdb_rxsz;
extern char *gdb_txp;
#ifdef DDB
/* If set, return to DDB when controlling GDB detaches. */
extern bool gdb_return_to_ddb;
#endif
int gdb_rx_begin(void);
int gdb_rx_equal(const char *);
int gdb_rx_mem(unsigned char *, size_t);

29
sys/gdb/gdb_main.c
View File

@ -60,6 +60,10 @@ int gdb_listening = 0;
static unsigned char gdb_bindata[64];
#ifdef DDB
bool gdb_return_to_ddb = false;
#endif
static int
gdb_init(void)
{
@ -569,6 +573,26 @@ do_qXfer(void)
return;
}
static void
gdb_handle_detach(void)
{
kdb_cpu_clear_singlestep();
gdb_listening = 0;
if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM)
gdb_cur->gdb_term();
#ifdef DDB
if (!gdb_return_to_ddb)
return;
gdb_return_to_ddb = false;
if (kdb_dbbe_select("ddb") != 0)
printf("The ddb backend could not be selected.\n");
#endif
}
static int
gdb_trap(int type, int code)
{
@ -638,7 +662,7 @@ gdb_trap(int type, int code)
}
case 'D': { /* Detach */
gdb_tx_ok();
kdb_cpu_clear_singlestep();
gdb_handle_detach();
return (1);
}
case 'g': { /* Read registers. */
@ -675,8 +699,7 @@ gdb_trap(int type, int code)
break;
}
case 'k': /* Kill request. */
kdb_cpu_clear_singlestep();
gdb_listening = 1;
gdb_handle_detach();
return (1);
case 'm': { /* Read memory. */
uintmax_t addr, size;

54
sys/gdb/gdb_packet.c
View File

@ -45,7 +45,27 @@ __FBSDID("$FreeBSD$");
static char gdb_rxbuf[GDB_BUFSZ];
char *gdb_rxp = NULL;
size_t gdb_rxsz = 0;
static char gdb_txbuf[GDB_BUFSZ];
/*
* The goal here is to allow in-place framing without making the math around
* 'gdb_txbuf' more complicated. A generous reading of union special rule for
* "common initial sequence" suggests this may be valid in standard C99 and
* later.
*/
static union {
struct _midbuf {
char mb_pad1;
char mb_buf[GDB_BUFSZ];
char mb_pad2[4];
} __packed txu_midbuf;
/* sizeof includes trailing nul byte and this is intentional. */
char txu_fullbuf[GDB_BUFSZ + sizeof("$#..")];
} gdb_tx_u;
#define gdb_txbuf gdb_tx_u.txu_midbuf.mb_buf
#define gdb_tx_fullbuf gdb_tx_u.txu_fullbuf
_Static_assert(sizeof(gdb_tx_u.txu_midbuf) == sizeof(gdb_tx_u.txu_fullbuf) &&
offsetof(struct _midbuf, mb_buf) == 1,
"assertions necessary for correctness");
char *gdb_txp = NULL; /* Used in inline functions. */
#define C2N(c) (((c) < 'A') ? (c) - '0' : \
@ -68,6 +88,9 @@ gdb_getc(void)
if (c == CTRL('C')) {
printf("Received ^C; trying to switch back to ddb.\n");
if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM)
gdb_cur->gdb_term();
if (kdb_dbbe_select("ddb") != 0)
printf("The ddb backend could not be selected.\n");
else {
@ -218,6 +241,29 @@ gdb_tx_begin(char tp)
gdb_tx_char(tp);
}
/*
* Take raw packet buffer and perform typical GDB packet framing, but not run-
* length encoding, before forwarding to driver ::gdb_sendpacket() routine.
*/
static void
gdb_tx_sendpacket(void)
{
size_t msglen, i;
unsigned char csum;
msglen = gdb_txp - gdb_txbuf;
/* Add GDB packet framing */
gdb_tx_fullbuf[0] = '$';
csum = 0;
for (i = 0; i < msglen; i++)
csum += (unsigned char)gdb_txbuf[i];
snprintf(&gdb_tx_fullbuf[1 + msglen], 4, "#%02x", (unsigned)csum);
gdb_cur->gdb_sendpacket(gdb_tx_fullbuf, msglen + 4);
}
int
gdb_tx_end(void)
{
@ -226,6 +272,11 @@ gdb_tx_end(void)
unsigned char c, cksum;
do {
if (gdb_cur->gdb_sendpacket != NULL) {
gdb_tx_sendpacket();
goto getack;
}
gdb_cur->gdb_putc('$');
cksum = 0;
@ -284,6 +335,7 @@ gdb_tx_end(void)
c = cksum & 0x0f;
gdb_cur->gdb_putc(N2C(c));
getack:
c = gdb_getc();
} while (c != '+');

406
sys/gdb/netgdb.c Normal file
View File

@ -0,0 +1,406 @@
/*-
* 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, 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,
};
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_FUNC(netgdb, db_netgdb_cmd, db_cmd_table, CS_OWN, NULL)
{
struct debugnet_ddb_config params;
struct debugnet_conn_params dcp;
struct debugnet_pcb *pcb;
int error;
if (panicstr == NULL) {
/* 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", &params);
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 */

44
sys/gdb/netgdb.h Normal file
View File

@ -0,0 +1,44 @@
/*-
* 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.
*
* $FreeBSD$
*/
#pragma once
/*
* Protocol information, for use by the userspace proxy server.
*
* It might make sense to allow not hardcoding these parameters as future work
* (e.g., for use in environments with arbitrary port filtering).
*
* The herald port is only used for initial handshake. The proxy server will
* choose a different remote port to connect back to the NetGDB client on by
* sending the HERALD ACK from that other port.
*/
#define NETGDB_HERALDPORT 20025
#define NETGDB_CLIENTPORT 20026
#define NETGDB_PROTO_V1 0x2515f095 /* Rolled a 2^32 sided die. */

1
sys/i386/conf/GENERIC
View File

@ -101,6 +101,7 @@ options GZIO # gzip-compressed kernel and user dumps
options ZSTDIO # zstd-compressed kernel and user dumps
options DEBUGNET # debugnet networking
options NETDUMP # netdump(4) client support
options NETGDB # netgdb(4) client support
# To make an SMP kernel, the next two lines are needed
options SMP # Symmetric MultiProcessor Kernel

1
sys/kern/subr_kdb.c
View File

@ -77,7 +77,6 @@ static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
KDB_BACKEND(null, NULL, NULL, NULL, NULL);
SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);

16
sys/net/debugnet.c
View File

@ -183,7 +183,7 @@ debugnet_udp_output(struct debugnet_pcb *pcb, struct mbuf *m)
return (debugnet_ip_output(pcb, m));
}
static int
int
debugnet_ack_output(struct debugnet_pcb *pcb, uint32_t seqno /* net endian */)
{
struct debugnet_ack *dn_ack;
@ -330,7 +330,7 @@ debugnet_send(struct debugnet_pcb *pcb, uint32_t type, const void *data,
printf(". ");
goto retransmit;
}
debugnet_network_poll(pcb->dp_ifp);
debugnet_network_poll(pcb);
DELAY(500);
if (pcb->dp_state == DN_STATE_REMOTE_CLOSED)
return (ECONNRESET);
@ -577,8 +577,11 @@ debugnet_pkt_in(struct ifnet *ifp, struct mbuf *m)
* driver directly for packets.
*/
void
debugnet_network_poll(struct ifnet *ifp)
debugnet_network_poll(struct debugnet_pcb *pcb)
{
struct ifnet *ifp;
ifp = pcb->dp_ifp;
ifp->if_debugnet_methods->dn_poll(ifp, 1000);
}
@ -610,6 +613,7 @@ int
debugnet_connect(const struct debugnet_conn_params *dcp,
struct debugnet_pcb **pcb_out)
{
struct debugnet_proto_aux herald_auxdata;
struct debugnet_pcb *pcb;
struct ifnet *ifp;
int error;
@ -738,8 +742,12 @@ debugnet_connect(const struct debugnet_conn_params *dcp,
}
MPASS(pcb->dp_state == DN_STATE_HAVE_GW_MAC);
herald_auxdata = (struct debugnet_proto_aux) {
.dp_offset_start = dcp->dc_herald_offset,
.dp_aux2 = dcp->dc_herald_aux2,
};
error = debugnet_send(pcb, DEBUGNET_HERALD, dcp->dc_herald_data,
dcp->dc_herald_datalen, NULL);
dcp->dc_herald_datalen, &herald_auxdata);
if (error != 0) {
printf("%s: failed to herald debugnet server\n", __func__);
goto cleanup;

22
sys/net/debugnet.h
View File

@ -107,6 +107,14 @@ struct debugnet_conn_params {
const void *dc_herald_data;
uint32_t dc_herald_datalen;
/*
* Consistent with debugnet_send(), aux paramaters to debugnet
* functions are provided host-endian (but converted to
* network endian on the wire).
*/
uint32_t dc_herald_aux2;
uint64_t dc_herald_offset;
/*
* If NULL, debugnet is a unidirectional channel from panic machine to
* remote server (like netdump).
@ -123,12 +131,14 @@ struct debugnet_conn_params {
* If the handler frees the mbuf chain, it should set the mbuf pointer
* to NULL. Otherwise, the debugnet input framework will free the
* chain.
*
* The handler should ACK receieved packets with debugnet_ack_output.
*/
void (*dc_rx_handler)(struct debugnet_pcb *, struct mbuf **);
};
/*
* Open a unidirectional stream to the specified server's herald port.
* Open a stream to the specified server's herald port.
*
* If all goes well, the server will send ACK from a different port to our ack
* port. This allows servers to somewhat gracefully handle multiple debugnet
@ -177,6 +187,16 @@ debugnet_sendempty(struct debugnet_pcb *pcb, uint32_t mhtype)
return (debugnet_send(pcb, mhtype, NULL, 0, NULL));
}
/*
* Full-duplex RX should ACK received messages.
*/
int debugnet_ack_output(struct debugnet_pcb *, uint32_t seqno /*net endian*/);
/*
* Check and/or wait for further packets.
*/
void debugnet_network_poll(struct debugnet_pcb *);
/*
* PCB accessors.
*/

2
sys/net/debugnet_inet.c
View File

@ -407,7 +407,7 @@ debugnet_arp_gw(struct debugnet_pcb *pcb)
return (error);
for (polls = 0; polls < debugnet_npolls &&
pcb->dp_state < DN_STATE_HAVE_GW_MAC; polls++) {
debugnet_network_poll(pcb->dp_ifp);
debugnet_network_poll(pcb);
DELAY(500);
}
if (pcb->dp_state >= DN_STATE_HAVE_GW_MAC)

1
sys/net/debugnet_int.h
View File

@ -87,7 +87,6 @@ SYSCTL_DECL(_net_debugnet);
int debugnet_ether_output(struct mbuf *, struct ifnet *, struct ether_addr,
u_short);
void debugnet_handle_udp(struct debugnet_pcb *, struct mbuf **);
void debugnet_network_poll(struct ifnet *);
#ifdef INET
int debugnet_arp_gw(struct debugnet_pcb *);

3
sys/sys/kdb.h
View File

@ -31,6 +31,7 @@
#ifndef _SYS_KDB_H_
#define _SYS_KDB_H_
#include <sys/linker_set.h>
#include <machine/setjmp.h>
struct pcb;
@ -61,6 +62,8 @@ struct kdb_dbbe {
}; \
DATA_SET(kdb_dbbe_set, name##_dbbe)
SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
extern u_char kdb_active; /* Non-zero while in debugger. */
extern int debugger_on_trap; /* enter the debugger on trap. */
extern struct kdb_dbbe *kdb_dbbe; /* Default debugger backend or NULL. */

2
sys/sys/param.h
View File

@ -60,7 +60,7 @@
* in the range 5 to 9.
*/
#undef __FreeBSD_version
#define __FreeBSD_version 1300052 /* Master, propagated to newvers */
#define __FreeBSD_version 1300053 /* Master, propagated to newvers */
/*
* __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,