gdbserver - Remote Server for the GNU Debugger
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
host to local TCP port 2345. (Currently,
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.
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
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 the GDB manual in node
Inferiors Connections and Programs Ω- shell command
info -f gdb -n 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
stdio to use
gdbserver. Specify the name of the program
to debug in prog. Any remaining arguments will be passed to the
program verbatim. When the program exits, GDB will close the connection,
gdbserver 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 in pid; GDB will do everything else. Like
with the previous mode, when the process pid exits, GDB will
close the connection, and
gdbserver will exit.
Multi-process mode Ω- 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:
List all options, with brief explanations.
This option causes gdbserver to print its version number and exit.
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 point gdbserver at a binary for the running process.
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
gdbserver to display extra status information
about the debugging process. This option is intended for
gdbserver development and for bug reports to the
gdbserver to display remote protocol debug
output. This option is intended for
and for bug reports to the developers.
gdbserver to send any debug output to the given
filename. This option is intended for
development and for bug reports to the developers.
gdbserver to include extra information in each
line of debugging output.
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
By default, gdbserver keeps the listening TCP port
open, so that additional connections are possible. However, if you start
gdbserver with the --once option, it will
stop listening for any further connection attempts after connecting to
the first GDB session.
The full documentation for GDB is maintained as a Texinfo manual. If
gdb programs and GDB's Texinfo
documentation are properly installed at your site, the command
should give you access to the complete manual.
Using GDB: A Guide to the GNU Source-Level Debugger, Richard M. Stallman and Roland H. Pesch, July 1991.
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