README for GDBserver & GDBreplay
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README for GDBserver & GDBreplay
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by Stu Grossman and Fred Fish
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by Stu Grossman and Fred Fish
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Introduction:
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Introduction:
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This is GDBserver, a remote server for Un*x-like systems. It can be used to
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This is GDBserver, a remote server for Un*x-like systems. It can be used to
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control the execution of a program on a target system from a GDB on a different
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control the execution of a program on a target system from a GDB on a different
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host. GDB and GDBserver communicate using the standard remote serial protocol
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host. GDB and GDBserver communicate using the standard remote serial protocol
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implemented in remote.c, and various *-stub.c files. They communicate via
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implemented in remote.c, and various *-stub.c files. They communicate via
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either a serial line or a TCP connection.
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either a serial line or a TCP connection.
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Usage (server (target) side):
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Usage (server (target) side):
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First, you need to have a copy of the program you want to debug put onto
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First, you need to have a copy of the program you want to debug put onto
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the target system. The program can be stripped to save space if needed, as
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the target system. The program can be stripped to save space if needed, as
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GDBserver doesn't care about symbols. All symbol handling is taken care of by
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GDBserver doesn't care about symbols. All symbol handling is taken care of by
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the GDB running on the host system.
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the GDB running on the host system.
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To use the server, you log on to the target system, and run the `gdbserver'
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To use the server, you log on to the target system, and run the `gdbserver'
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program. You must tell it (a) how to communicate with GDB, (b) the name of
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program. You must tell it (a) how to communicate with GDB, (b) the name of
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your program, and (c) its arguments. The general syntax is:
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your program, and (c) its arguments. The general syntax is:
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target> gdbserver COMM PROGRAM [ARGS ...]
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target> gdbserver COMM PROGRAM [ARGS ...]
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For example, using a serial port, you might say:
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For example, using a serial port, you might say:
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target> gdbserver /dev/com1 emacs foo.txt
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target> gdbserver /dev/com1 emacs foo.txt
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This tells gdbserver to debug emacs with an argument of foo.txt, and to
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This tells gdbserver to debug emacs with an argument of foo.txt, and to
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communicate with GDB via /dev/com1. Gdbserver now waits patiently for the
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communicate with GDB via /dev/com1. Gdbserver now waits patiently for the
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host GDB to communicate with it.
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host GDB to communicate with it.
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To use a TCP connection, you could say:
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To use a TCP connection, you could say:
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target> gdbserver host:2345 emacs foo.txt
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target> gdbserver host:2345 emacs foo.txt
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This says pretty much the same thing as the last example, except that we are
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This says pretty much the same thing as the last example, except that we are
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going to communicate with the host GDB via TCP. The `host:2345' argument means
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going to communicate with the host GDB via TCP. The `host:2345' argument means
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that we are expecting to see a TCP connection from `host' to local TCP port
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that we are expecting to see a TCP connection from `host' to local TCP port
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2345. (Currently, the `host' part is ignored.) You can choose any number you
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2345. (Currently, the `host' part is ignored.) You can choose any number you
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want for the port number as long as it does not conflict with any existing TCP
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want for the port number as long as it does not conflict with any existing TCP
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ports on the target system. This same port number must be used in the host
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ports on the target system. This same port number must be used in the host
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GDBs `target remote' command, which will be described shortly. Note that if
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GDBs `target remote' command, which will be described shortly. Note that if
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you chose a port number that conflicts with another service, gdbserver will
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you chose a port number that conflicts with another service, gdbserver will
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print an error message and exit.
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print an error message and exit.
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Usage (host side):
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Usage (host side):
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You need an unstripped copy of the target program on your host system, since
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You need an unstripped copy of the target program on your host system, since
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GDB needs to examine it's symbol tables and such. Start up GDB as you normally
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GDB needs to examine it's symbol tables and such. Start up GDB as you normally
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would, with the target program as the first argument. (You may need to use the
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would, with the target program as the first argument. (You may need to use the
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--baud option if the serial line is running at anything except 9600 baud.)
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--baud option if the serial line is running at anything except 9600 baud.)
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Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only
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Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only
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new command you need to know about is `target remote'. It's argument is either
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new command you need to know about is `target remote'. It's argument is either
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a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT
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a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT
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descriptor. For example:
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descriptor. For example:
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(gdb) target remote /dev/ttyb
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(gdb) target remote /dev/ttyb
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communicates with the server via serial line /dev/ttyb, and:
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communicates with the server via serial line /dev/ttyb, and:
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(gdb) target remote the-target:2345
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(gdb) target remote the-target:2345
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communicates via a TCP connection to port 2345 on host `the-target', where
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communicates via a TCP connection to port 2345 on host `the-target', where
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you previously started up gdbserver with the same port number. Note that for
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you previously started up gdbserver with the same port number. Note that for
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TCP connections, you must start up gdbserver prior to using the `target remote'
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TCP connections, you must start up gdbserver prior to using the `target remote'
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command, otherwise you may get an error that looks something like
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command, otherwise you may get an error that looks something like
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`Connection refused'.
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`Connection refused'.
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Building:
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Building:
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Configuring gdbserver you should specify the same machine for host and
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Configuring gdbserver you should specify the same machine for host and
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target (which are the machine that gdbserver is going to run on. This
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target (which are the machine that gdbserver is going to run on. This
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is not the same as the machine that gdb is going to run on; building
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is not the same as the machine that gdb is going to run on; building
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gdbserver automatically as part of building a whole tree of tools does
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gdbserver automatically as part of building a whole tree of tools does
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not currently work if cross-compilation is involved (we don't get the
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not currently work if cross-compilation is involved (we don't get the
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right CC in the Makefile, to start with)).
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right CC in the Makefile, to start with)).
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gdbserver should work on sparc-sun-sunos4* or Lynx. The following
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gdbserver should work on sparc-sun-sunos4* or Lynx. The following
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instructions pertain to Lynx. To build the server for Lynx, make a
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instructions pertain to Lynx. To build the server for Lynx, make a
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new copy of the distribution onto a disk that is NFS shared with the
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new copy of the distribution onto a disk that is NFS shared with the
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Lynx system. Lets say that's in a directory called xyzzy. Then,
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Lynx system. Lets say that's in a directory called xyzzy. Then,
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follow these steps under the host system:
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follow these steps under the host system:
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1) cd xyzzy/gdb/gdbserver
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1) cd xyzzy/gdb/gdbserver
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2) ../../configure i386-none-lynx
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2) ../../configure i386-none-lynx
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When that completes, do the following on the Lynx system:
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When that completes, do the following on the Lynx system:
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3) cd xyzzy/gdb/gdbserver
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3) cd xyzzy/gdb/gdbserver
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4) make CC=gcc
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4) make CC=gcc
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It should build with only a minor complaint about NULL being redefined. That's
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It should build with only a minor complaint about NULL being redefined. That's
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a LynxOS problem, and can be ignored.
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a LynxOS problem, and can be ignored.
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It's also possible that you may have a cross-compiler to Lynx. In that case,
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It's also possible that you may have a cross-compiler to Lynx. In that case,
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you can skip the stuff about NFS. You would replace steps 3 & 4 with:
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you can skip the stuff about NFS. You would replace steps 3 & 4 with:
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make CC=lynx-target-compiler...
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make CC=lynx-target-compiler...
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Using GDBreplay:
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Using GDBreplay:
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A special hacked down version of gdbserver can be used to replay remote
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A special hacked down version of gdbserver can be used to replay remote
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debug log files created by gdb. Before using the gdb "target" command to
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debug log files created by gdb. Before using the gdb "target" command to
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initiate a remote debug session, use "set remotelogfile " to tell
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initiate a remote debug session, use "set remotelogfile " to tell
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gdb that you want to make a recording of the serial or tcp session. Note
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gdb that you want to make a recording of the serial or tcp session. Note
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that when replaying the session, gdb communicates with gdbreplay via tcp,
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that when replaying the session, gdb communicates with gdbreplay via tcp,
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regardless of whether the original session was via a serial link or tcp.
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regardless of whether the original session was via a serial link or tcp.
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Once you are done with the remote debug session, start gdbreplay and
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Once you are done with the remote debug session, start gdbreplay and
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tell it the name of the log file and the host and port number that gdb
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tell it the name of the log file and the host and port number that gdb
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should connect to (typically the same as the host running gdb):
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should connect to (typically the same as the host running gdb):
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$ gdbreplay logfile host:port
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$ gdbreplay logfile host:port
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Then start gdb (preferably in a different screen or window) and use the
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Then start gdb (preferably in a different screen or window) and use the
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"target" command to connect to gdbreplay:
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"target" command to connect to gdbreplay:
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(gdb) target remote host:port
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(gdb) target remote host:port
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Repeat the same sequence of user commands to gdb that you gave in the
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Repeat the same sequence of user commands to gdb that you gave in the
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original debug session. Gdb should not be able to tell that it is talking
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original debug session. Gdb should not be able to tell that it is talking
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to gdbreplay rather than a real target, all other things being equal. Note
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to gdbreplay rather than a real target, all other things being equal. Note
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that gdbreplay echos the command lines to stderr, as well as the contents of
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that gdbreplay echos the command lines to stderr, as well as the contents of
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the packets it sends and receives. The last command echoed by gdbreplay is
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the packets it sends and receives. The last command echoed by gdbreplay is
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the next command that needs to be typed to gdb to continue the session in
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the next command that needs to be typed to gdb to continue the session in
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sync with the original session.
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sync with the original session.
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