| README for GDBserver & GDBreplay
| by Stu Grossman and Fred Fish
|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.
|They communicate via either a serial line or a TCP connection.
|For more information about GDBserver, see the GDB manual:
|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 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 GDB's
|`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.
|On some targets, 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.
|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
|See the `configure.srv` file for the list of host triplets you can build
|Building GDBserver for your host is very straightforward. If you build
|GDB natively on a host which GDBserver supports, it will be built
|automatically when you build GDB. You can also build just GDBserver:
| % mkdir obj
| % cd obj
| % path-to-toplevel-sources/configure --disable-gdb
| % make all-gdbserver
|(If you have a combined binutils+gdb tree, you may want to also
|disable other directories when configuring, e.g., binutils, gas, gold,
|gprof, and ld.)
|If you prefer to cross-compile to your target, then you can also build
|GDBserver that way. For example:
| % export CC=your-cross-compiler
| % path-to-topevel-sources/configure --disable-gdb
| % make all-gdbserver
|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.