Commit Graph

10 Commits

Author SHA1 Message Date
Conrad Meyer
6310546dba gdb(4): Implement support for NoAckMode
When the underlying debugport transport is reliable, GDB's additional
checksums and acknowledgements are redundant.  NoAckMode eliminates the
the acks and allows us to skip checking RX checksums.  The GDB packet
framing does not change, so unfortunately (valid) checksums are still
included as message trailers.

The gdb(4) stub in FreeBSD advertises support for the feature in response to
the client's 'qSupported' request IFF the current debugport has the
gdb_dbfeatures flag GDB_DBGP_FEAT_RELIABLE set.  Currently, only netgdb(4)
supports this feature.

If the remote GDB client supports the feature and does not have it disabled
via a GDB configuration knob, it may instruct our gdb(4) stub to enter
NoAckMode.  Unless and until it issues that command, we must continue to
transmit acks as usual (and for now, we continue to wait until we receive
them as well, even if we know the debugport is on a reliable transport).

In the kernel sources, the sense of the flag representing the state of the
feature is reversed from that of the GDB command.  (I.e., it is
'gdb_ackmode', not 'gdb_noackmode.')  This is to avoid confusing double-
negative conditions.

For reference, see:
  * https://sourceware.org/gdb/onlinedocs/gdb/Packet-Acknowledgment.html
  * https://sourceware.org/gdb/onlinedocs/gdb/General-Query-Packets.html#QStartNoAckMode

Reviewed by:	jhb, markj (both earlier version)
Differential Revision:	https://reviews.freebsd.org/D21761
2019-10-17 22:37:25 +00:00
Conrad Meyer
dda17b3672 Implement NetGDB(4)
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
2019-10-17 21:33:01 +00:00
Conrad Meyer
10f6c05ce7 gdb(4): Root a sysctl tree at 'debug.gdb.'
Like debug.ddb and debug.kdb.  Rename 'debug.gdbcons' to 'debug.gdb.cons,'
but leave the old name as a compatibility alias.
2019-09-08 22:52:47 +00:00
Conrad Meyer
5df6fa4344 gdb(4): Style
No functional change.

I was surprised to find that no sys/ header already defines the -1 EOF
convention anywhere, so defined one locally.
2019-08-22 00:36:16 +00:00
Conrad Meyer
130ef1ad11 gdb(4): Pack 'info threads' responses into fewer packets
We suffer at least one round trip ACK latency every command / packet that
GDB has to send and receive, and the response format for 'info threads'
supports packing many threads IDs into a single packet, so do so.

Adds and uses a new API, gdb_txbuf_has_capacity(), which checks for a
certain number of bytes available in the outgoing txbuf.

On an example amd64 VM, the number of RTTs to transmit this list is reduced
by a factor of 110x.  This is especially beneficial with recent GDB, which
seems to request the list at least twice during attach.
2019-08-19 22:57:03 +00:00
Pedro F. Giffuni
497b6b2a86 sys/gdb: further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
2017-11-27 15:16:59 +00:00
Benno Rice
27ecc2adbc Add support for gdb's memory searching capabilities to our in-kernel gdb
server.

Submitted by:	Daniel O'Connor <daniel.oconnor@isilon.com>
Reviewed by:	jhb
Sponsored by:	EMC Isilon Storage Division
2014-09-05 16:40:47 +00:00
Sam Leffler
7d0c6c9fc5 add support for copying console messages to a remote gdb
Reviewed by:	kan
2006-03-23 23:06:14 +00:00
Warner Losh
fa521b0366 /* -> /*- for copyright notices, minor format tweaks as necessary 2005-01-06 18:27:30 +00:00
Marcel Moolenaar
72d44f31a6 Introduce the GDB debugger backend for the new KDB framework. The
backend improves over the old GDB support in the following ways:
o  Unified implementation with minimal MD code.
o  A simple interface for devices to register themselves as debug
   ports, ala consoles.
o  Compression by using run-length encoding.
o  Implements GDB threading support.
2004-07-10 17:47:22 +00:00