| 1 | README for GDBserver & GDBreplay |
| 2 | by Stu Grossman and Fred Fish |
| 3 | |
| 4 | Introduction: |
| 5 | |
| 6 | This is GDBserver, a remote server for Un*x-like systems. It can be used to |
| 7 | control the execution of a program on a target system from a GDB on a different |
| 8 | host. GDB and GDBserver communicate using the standard remote serial protocol |
| 9 | implemented in remote.c, and various *-stub.c files. They communicate via |
| 10 | either a serial line or a TCP connection. |
| 11 | |
| 12 | Usage (server (target) side): |
| 13 | |
| 14 | First, you need to have a copy of the program you want to debug put onto |
| 15 | the target system. The program can be stripped to save space if needed, as |
| 16 | GDBserver doesn't care about symbols. All symbol handling is taken care of by |
| 17 | the GDB running on the host system. |
| 18 | |
| 19 | To use the server, you log on to the target system, and run the `gdbserver' |
| 20 | program. You must tell it (a) how to communicate with GDB, (b) the name of |
| 21 | your program, and (c) its arguments. The general syntax is: |
| 22 | |
| 23 | target> gdbserver COMM PROGRAM [ARGS ...] |
| 24 | |
| 25 | For example, using a serial port, you might say: |
| 26 | |
| 27 | target> gdbserver /dev/com1 emacs foo.txt |
| 28 | |
| 29 | This tells gdbserver to debug emacs with an argument of foo.txt, and to |
| 30 | communicate with GDB via /dev/com1. Gdbserver now waits patiently for the |
| 31 | host GDB to communicate with it. |
| 32 | |
| 33 | To use a TCP connection, you could say: |
| 34 | |
| 35 | target> gdbserver host:2345 emacs foo.txt |
| 36 | |
| 37 | This says pretty much the same thing as the last example, except that we are |
| 38 | going to communicate with the host GDB via TCP. The `host:2345' argument means |
| 39 | that we are expecting to see a TCP connection from `host' to local TCP port |
| 40 | 2345. (Currently, the `host' part is ignored.) You can choose any number you |
| 41 | want for the port number as long as it does not conflict with any existing TCP |
| 42 | ports on the target system. This same port number must be used in the host |
| 43 | GDBs `target remote' command, which will be described shortly. Note that if |
| 44 | you chose a port number that conflicts with another service, gdbserver will |
| 45 | print an error message and exit. |
| 46 | |
| 47 | On some targets, gdbserver can also attach to running programs. This is |
| 48 | accomplished via the --attach argument. The syntax is: |
| 49 | |
| 50 | target> gdbserver COMM --attach PID |
| 51 | |
| 52 | PID is the process ID of a currently running process. It isn't necessary |
| 53 | to point gdbserver at a binary for the running process. |
| 54 | |
| 55 | Usage (host side): |
| 56 | |
| 57 | You need an unstripped copy of the target program on your host system, since |
| 58 | GDB needs to examine it's symbol tables and such. Start up GDB as you normally |
| 59 | would, 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.) |
| 61 | Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only |
| 62 | new command you need to know about is `target remote'. It's argument is either |
| 63 | a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT |
| 64 | descriptor. For example: |
| 65 | |
| 66 | (gdb) target remote /dev/ttyb |
| 67 | |
| 68 | communicates with the server via serial line /dev/ttyb, and: |
| 69 | |
| 70 | (gdb) target remote the-target:2345 |
| 71 | |
| 72 | communicates via a TCP connection to port 2345 on host `the-target', where |
| 73 | you previously started up gdbserver with the same port number. Note that for |
| 74 | TCP connections, you must start up gdbserver prior to using the `target remote' |
| 75 | command, otherwise you may get an error that looks something like |
| 76 | `Connection refused'. |
| 77 | |
| 78 | Building gdbserver: |
| 79 | |
| 80 | The supported targets as of November 2006 are: |
| 81 | arm-*-linux* |
| 82 | crisv32-*-linux* |
| 83 | cris-*-linux* |
| 84 | i[34567]86-*-cygwin* |
| 85 | i[34567]86-*-linux* |
| 86 | i[34567]86-*-mingw* |
| 87 | ia64-*-linux* |
| 88 | m32r*-*-linux* |
| 89 | m68*-*-linux* |
| 90 | m68*-*-uclinux* |
| 91 | mips*64*-*-linux* |
| 92 | mips*-*-linux* |
| 93 | powerpc[64]-*-linux* |
| 94 | s390[x]-*-linux* |
| 95 | sh-*-linux* |
| 96 | spu*-*-* |
| 97 | x86_64-*-linux* |
| 98 | xscale*-*-linux* |
| 99 | |
| 100 | Configuring gdbserver you should specify the same machine for host and |
| 101 | target (which are the machine that gdbserver is going to run on. This |
| 102 | is not the same as the machine that gdb is going to run on; building |
| 103 | gdbserver automatically as part of building a whole tree of tools does |
| 104 | not currently work if cross-compilation is involved (we don't get the |
| 105 | right CC in the Makefile, to start with)). |
| 106 | |
| 107 | Building gdbserver for your target is very straightforward. If you build |
| 108 | GDB natively on a target which gdbserver supports, it will be built |
| 109 | automatically when you build GDB. You can also build just gdbserver: |
| 110 | |
| 111 | % mkdir obj |
| 112 | % cd obj |
| 113 | % path-to-gdbserver-sources/configure |
| 114 | % make |
| 115 | |
| 116 | If you prefer to cross-compile to your target, then you can also build |
| 117 | gdbserver that way. In a Bourne shell, for example: |
| 118 | |
| 119 | % export CC=your-cross-compiler |
| 120 | % path-to-gdbserver-sources/configure your-target-name |
| 121 | % make |
| 122 | |
| 123 | Using GDBreplay: |
| 124 | |
| 125 | A special hacked down version of gdbserver can be used to replay remote |
| 126 | debug log files created by gdb. Before using the gdb "target" command to |
| 127 | initiate a remote debug session, use "set remotelogfile <filename>" to tell |
| 128 | gdb that you want to make a recording of the serial or tcp session. Note |
| 129 | that when replaying the session, gdb communicates with gdbreplay via tcp, |
| 130 | regardless of whether the original session was via a serial link or tcp. |
| 131 | |
| 132 | Once you are done with the remote debug session, start gdbreplay and |
| 133 | tell it the name of the log file and the host and port number that gdb |
| 134 | should connect to (typically the same as the host running gdb): |
| 135 | |
| 136 | $ gdbreplay logfile host:port |
| 137 | |
| 138 | Then start gdb (preferably in a different screen or window) and use the |
| 139 | "target" command to connect to gdbreplay: |
| 140 | |
| 141 | (gdb) target remote host:port |
| 142 | |
| 143 | Repeat the same sequence of user commands to gdb that you gave in the |
| 144 | original debug session. Gdb should not be able to tell that it is talking |
| 145 | to gdbreplay rather than a real target, all other things being equal. Note |
| 146 | that gdbreplay echos the command lines to stderr, as well as the contents of |
| 147 | the packets it sends and receives. The last command echoed by gdbreplay is |
| 148 | the next command that needs to be typed to gdb to continue the session in |
| 149 | sync with the original session. |