Gdb/gdbserver-man
gdbserver man
gdbserver man
gdbserver comm prog [args…] gdbserver –attach comm pid gdbserver –multi comm
gdbserver
is a program that allows you to run GDB on a different machine
than the one which is running the program being debugged.
Usage (server (target) side)
First, you need to have a copy of the program you want to debug put onto
the target system. The program can be stripped to save space if needed, as
gdbserver
doesn’t care about symbols. All symbol handling is taken care of by
the GDB running on the host system.
To use the server, you log on to the target system, and run the gdbserver
program. You must tell it (a) how to communicate with GDB, (b) the name of
your program, and (c) its arguments. The general syntax is:
target> gdbserver comm program [args ...]
For example, using a serial port, you might say:
target> gdbserver /dev/com1 emacs foo.txt
This tells gdbserver
to debug emacs with an argument of foo.txt, and
to communicate with GDB via /dev/com1
. gdbserver
now
waits patiently for the host GDB to communicate with it.
To use a TCP connection, you could say:
target> gdbserver host:2345 emacs foo.txt
This says pretty much the same thing as the last example, except that we are
going to communicate with the host
GDB via TCP. The host:2345
argument means
that we are expecting to see a TCP connection from host
to local TCP port
2345. (Currently, the host
part is ignored.) You can choose any number you
want for the port number as long as it does not conflict with any existing TCP
ports on the target system. This same port number must be used in the host
GDBs target remote
command, which will be described shortly. Note that if
you chose a port number that conflicts with another service, gdbserver
will
print an error message and exit.
gdbserver
can also attach to running programs.
This is accomplished via the --attach
argument. The syntax is:
target> gdbserver --attach comm pid
pid
is the process ID of a currently running process. It isn’t
necessary to point gdbserver
at a binary for the running process.
To start gdbserver
without supplying an initial command to run
or process ID to attach, use the --multi
command line option.
In such case you should connect using target extended-remote to start
the program you want to debug.
target> gdbserver --multi comm
Usage (host side)
You need an unstripped copy of the target program on your host system, since
GDB needs to examine its symbol tables and such. Start up GDB as you normally
would, with the target program as the first argument. (You may need to use the
--baud
option if the serial line is running at anything except 9600 baud.)
That is gdb TARGET-PROG
, or gdb --baud BAUD TARGET-PROG
. After that, the only
new command you need to know about is target remote
(or target extended-remote
). Its argument is either
a device name (usually a serial device, like /dev/ttyb
), or a HOST:PORT
descriptor. For example:
(gdb) target remote /dev/ttyb
communicates with the server via serial line /dev/ttyb
, and:
(gdb) target remote the-target:2345
communicates via a TCP connection to port 2345 on host ‘the-target’, where
you previously started up gdbserver
with the same port number. Note that for
TCP connections, you must start up gdbserver
prior to using the ‘target remote’
command, otherwise you may get an error that looks something like
‘Connection refused’.
gdbserver
can also debug multiple inferiors at once,
described in
Inferiors Connections and Programs.
In such case use the extended-remote
GDB command variant:
(gdb) target extended-remote the-target:2345
The gdbserver
option --multi
may or may not be used in such
case.
There are three different modes for invoking gdbserver
:
Debug a specific program specified by its program name:
gdbserver comm prog [args…]
The
comm
parameter specifies how should the server communicate with GDB; it is either a device name (to use a serial line), a TCP port number (:1234
), or-
orstdio
to use stdin/stdout ofgdbserver
. Specify the name of the program to debug inprog
. Any remaining arguments will be passed to the program verbatim. When the program exits, GDB will close the connection, andgdbserver
will exit.Debug a specific program by specifying the process ID of a running program:
gdbserver --attach comm pid
The
comm
parameter is as described above. Supply the process ID of a running program inpid
; GDB will do everything else. Like with the previous mode, when the processpid
exits, GDB will close the connection, andgdbserver
will exit.Multi-process mode – debug more than one program/process:
gdbserver --multi comm
In this mode, GDB can instruct
gdbserver
which command(s) to run. Unlike the other 2 modes, GDB will not close the connection when a process being debugged exits, so you can debug several processes in the same session.
In each of the modes you may specify these options:
--help
List all options, with brief explanations.
--version
This option causes
gdbserver
to print its version number and exit.--attach
gdbserver
will attach to a running program. The syntax is:target> gdbserver --attach comm pid
pid
is the process ID of a currently running process. It isn’t necessary to pointgdbserver
at a binary for the running process.--multi
To start
gdbserver
without supplying an initial command to run or process ID to attach, use this command line option. Then you can connect using target extended-remote and start the program you want to debug. The syntax is:target> gdbserver --multi comm
--debug
Instruct
gdbserver
to display extra status information about the debugging process. This option is intended forgdbserver
development and for bug reports to the developers.--remote-debug
Instruct
gdbserver
to display remote protocol debug output. This option is intended forgdbserver
development and for bug reports to the developers.--debug-file=filename
Instruct
gdbserver
to send any debug output to the givenfilename
. This option is intended forgdbserver
development and for bug reports to the developers.--debug-format=option1[,option2,...]
Instruct
gdbserver
to include extra information in each line of debugging output. See Other Command-Line Arguments for gdbserver.--wrapper
Specify a wrapper to launch programs for debugging. The option should be followed by the name of the wrapper, then any command-line arguments to pass to the wrapper, then -- indicating the end of the wrapper arguments.
--once
By default,
gdbserver
keeps the listening TCP port open, so that additional connections are possible. However, if you startgdbserver
with the--once
option, it will stop listening for any further connection attempts after connecting to the first GDB session.