gdbserver(1)
GDBSERVER(1) GNU Development Tools GDBSERVER(1)
NAME
gdbserver - Remote Server for the GNU Debugger
SYNOPSIS
gdbserver comm prog [args...]
gdbserver --attach comm pid
gdbserver --multi comm
DESCRIPTION
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
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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 it's 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 and Programs"
-- shell command "info -f gdb -n 'Inferiors and Programs'".
In such case use the "extended-remote" GDB command variant:
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(gdb) target extended-remote the-target:2345
The gdbserver option --multi may or may not be used in such
case.
OPTIONS
There are three different modes for invoking gdbserver:
o 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 "-" or
"stdio" to use stdin/stdout of "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, and
"gdbserver" will exit.
o 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.
o 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.
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--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 point gdbserver 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
for "gdbserver" development and for bug reports to the
developers.
--remote-debug
Instruct "gdbserver" to display remote protocol debug
output. This option is intended for "gdbserver"
development and for bug reports to the developers.
--debug-format=option1[,option2,...]
Instruct "gdbserver" to include extra information in
each line of debugging output.
--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 start "gdbserver" with the --once option, it will
stop listening for any further connection attempts after
connecting to the first GDB session.
SEE ALSO
The full documentation for GDB is maintained as a Texinfo
manual. If the "info" and "gdb" programs and GDB's Texinfo
documentation are properly installed at your site, the
command
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info gdb
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.
COPYRIGHT
Copyright (c) 1988-2018 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation
License, Version 1.3 or any later version published by the
Free Software Foundation; with the Invariant Sections being
"Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU
Manual," and with the Back-Cover Texts as in (a) below.
(a) The FSF's Back-Cover Text is: "You are free to copy and
modify this GNU Manual. Buying copies from GNU Press
supports the FSF in developing GNU and promoting software
freedom."
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