| README for GDBserver & GDBreplay |
| by Stu Grossman and Fred Fish |
| |
| Introduction: |
| |
| This is GDBserver, a remote server for Un*x-like systems. It can be used to |
| control the execution of a program on a target system from a GDB on a different |
| host. GDB and GDBserver communicate using the standard remote serial protocol |
| implemented in remote.c, and various *-stub.c files. They communicate via |
| either a serial line or a TCP connection. |
| |
| 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. |
| |
| 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.) |
| Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only |
| new command you need to know about is `target remote'. It's 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'. |
| |
| Building: |
| |
| Configuring gdbserver you should specify the same machine for host and |
| target (which are the machine that gdbserver is going to run on. This |
| is not the same as the machine that gdb is going to run on; building |
| gdbserver automatically as part of building a whole tree of tools does |
| not currently work if cross-compilation is involved (we don't get the |
| right CC in the Makefile, to start with)). |
| |
| gdbserver should work on sparc-sun-sunos4* or Lynx. The following |
| instructions pertain to Lynx. To build the server for Lynx, make a |
| new copy of the distribution onto a disk that is NFS shared with the |
| Lynx system. Lets say that's in a directory called xyzzy. Then, |
| follow these steps under the host system: |
| |
| 1) cd xyzzy/gdb/gdbserver |
| 2) ../../configure i386-none-lynx |
| |
| When that completes, do the following on the Lynx system: |
| |
| 3) cd xyzzy/gdb/gdbserver |
| 4) make CC=gcc |
| |
| It should build with only a minor complaint about NULL being redefined. That's |
| a LynxOS problem, and can be ignored. |
| |
| It's also possible that you may have a cross-compiler to Lynx. In that case, |
| you can skip the stuff about NFS. You would replace steps 3 & 4 with: |
| |
| make CC=lynx-target-compiler... |
| |
| Using GDBreplay: |
| |
| A special hacked down version of gdbserver can be used to replay remote |
| debug log files created by gdb. Before using the gdb "target" command to |
| initiate a remote debug session, use "set remotelogfile <filename>" to tell |
| gdb that you want to make a recording of the serial or tcp session. Note |
| that when replaying the session, gdb communicates with gdbreplay via tcp, |
| regardless of whether the original session was via a serial link or tcp. |
| |
| Once you are done with the remote debug session, start gdbreplay and |
| tell it the name of the log file and the host and port number that gdb |
| should connect to (typically the same as the host running gdb): |
| |
| $ gdbreplay logfile host:port |
| |
| Then start gdb (preferably in a different screen or window) and use the |
| "target" command to connect to gdbreplay: |
| |
| (gdb) target remote host:port |
| |
| Repeat the same sequence of user commands to gdb that you gave in the |
| original debug session. Gdb should not be able to tell that it is talking |
| to gdbreplay rather than a real target, all other things being equal. Note |
| that gdbreplay echos the command lines to stderr, as well as the contents of |
| the packets it sends and receives. The last command echoed by gdbreplay is |
| the next command that needs to be typed to gdb to continue the session in |
| sync with the original session. |