1 README for GDBserver & GDBreplay 2 by Stu Grossman and Fred Fish 3 4Introduction: 5 6This is GDBserver, a remote server for Un*x-like systems. It can be used to 7control the execution of a program on a target system from a GDB on a different 8host. GDB and GDBserver communicate using the standard remote serial protocol 9implemented in remote.c, and various *-stub.c files. They communicate via 10either a serial line or a TCP connection. 11 12Usage (server (target) side): 13 14First, you need to have a copy of the program you want to debug put onto 15the target system. The program can be stripped to save space if needed, as 16GDBserver doesn't care about symbols. All symbol handling is taken care of by 17the GDB running on the host system. 18 19To use the server, you log on to the target system, and run the `gdbserver' 20program. You must tell it (a) how to communicate with GDB, (b) the name of 21your program, and (c) its arguments. The general syntax is: 22 23 target> gdbserver COMM PROGRAM [ARGS ...] 24 25For example, using a serial port, you might say: 26 27 target> gdbserver /dev/com1 emacs foo.txt 28 29This tells gdbserver to debug emacs with an argument of foo.txt, and to 30communicate with GDB via /dev/com1. Gdbserver now waits patiently for the 31host GDB to communicate with it. 32 33To use a TCP connection, you could say: 34 35 target> gdbserver host:2345 emacs foo.txt 36 37This says pretty much the same thing as the last example, except that we are 38going to communicate with the host GDB via TCP. The `host:2345' argument means 39that we are expecting to see a TCP connection from `host' to local TCP port 402345. (Currently, the `host' part is ignored.) You can choose any number you 41want for the port number as long as it does not conflict with any existing TCP 42ports on the target system. This same port number must be used in the host 43GDBs `target remote' command, which will be described shortly. Note that if 44you chose a port number that conflicts with another service, gdbserver will 45print an error message and exit. 46 47On some targets, gdbserver can also attach to running programs. This is 48accomplished via the --attach argument. The syntax is: 49 50 target> gdbserver COMM --attach PID 51 52PID is the process ID of a currently running process. It isn't necessary 53to point gdbserver at a binary for the running process. 54 55Usage (host side): 56 57You need an unstripped copy of the target program on your host system, since 58GDB needs to examine it's symbol tables and such. Start up GDB as you normally 59would, with the target program as the first argument. (You may need to use the 60--baud option if the serial line is running at anything except 9600 baud.) 61Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only 62new command you need to know about is `target remote'. It's argument is either 63a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT 64descriptor. For example: 65 66 (gdb) target remote /dev/ttyb 67 68communicates with the server via serial line /dev/ttyb, and: 69 70 (gdb) target remote the-target:2345 71 72communicates via a TCP connection to port 2345 on host `the-target', where 73you previously started up gdbserver with the same port number. Note that for 74TCP connections, you must start up gdbserver prior to using the `target remote' 75command, otherwise you may get an error that looks something like 76`Connection refused'. 77 78Building gdbserver: 79 80The supported targets as of February 2002 are: 81 arm-*-linux-gnu 82 i386-*-linux-gnu 83 ia64-*-linux-gnu 84 m68k-*-linux-gnu 85 mips-*-linux-gnu 86 powerpc-*-linux-gnu 87 sh-*-linux-gnu 88 89Configuring gdbserver you should specify the same machine for host and 90target (which are the machine that gdbserver is going to run on. This 91is not the same as the machine that gdb is going to run on; building 92gdbserver automatically as part of building a whole tree of tools does 93not currently work if cross-compilation is involved (we don't get the 94right CC in the Makefile, to start with)). 95 96Building gdbserver for your target is very straightforward. If you build 97GDB natively on a target which gdbserver supports, it will be built 98automatically when you build GDB. You can also build just gdbserver: 99 100 % mkdir obj 101 % cd obj 102 % path-to-gdbserver-sources/configure 103 % make 104 105If you prefer to cross-compile to your target, then you can also build 106gdbserver that way. In a Bourne shell, for example: 107 108 % export CC=your-cross-compiler 109 % path-to-gdbserver-sources/configure your-target-name 110 % make 111 112Using GDBreplay: 113 114A special hacked down version of gdbserver can be used to replay remote 115debug log files created by gdb. Before using the gdb "target" command to 116initiate a remote debug session, use "set remotelogfile <filename>" to tell 117gdb that you want to make a recording of the serial or tcp session. Note 118that when replaying the session, gdb communicates with gdbreplay via tcp, 119regardless of whether the original session was via a serial link or tcp. 120 121Once you are done with the remote debug session, start gdbreplay and 122tell it the name of the log file and the host and port number that gdb 123should connect to (typically the same as the host running gdb): 124 125 $ gdbreplay logfile host:port 126 127Then start gdb (preferably in a different screen or window) and use the 128"target" command to connect to gdbreplay: 129 130 (gdb) target remote host:port 131 132Repeat the same sequence of user commands to gdb that you gave in the 133original debug session. Gdb should not be able to tell that it is talking 134to gdbreplay rather than a real target, all other things being equal. Note 135that gdbreplay echos the command lines to stderr, as well as the contents of 136the packets it sends and receives. The last command echoed by gdbreplay is 137the next command that needs to be typed to gdb to continue the session in 138sync with the original session. 139