gdb/gdbserver/README

   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 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
  89 Configuring gdbserver you should specify the same machine for host and
  90 target (which are the machine that gdbserver is going to run on.  This
  91 is not the same as the machine that gdb is going to run on; building
  92 gdbserver automatically as part of building a whole tree of tools does
  93 not currently work if cross-compilation is involved (we don't get the
  94 right CC in the Makefile, to start with)).
  95
  96 Building gdbserver for your target is very straightforward.  If you build
  97 GDB natively on a target which gdbserver supports, it will be built
  98 automatically 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
 105 If you prefer to cross-compile to your target, then you can also build
 106 gdbserver 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
 112 Using GDBreplay:
 113
 114 A special hacked down version of gdbserver can be used to replay remote
 115 debug log files created by gdb.  Before using the gdb "target" command to
 116 initiate a remote debug session, use "set remotelogfile <filename>" to tell
 117 gdb that you want to make a recording of the serial or tcp session.  Note
 118 that when replaying the session, gdb communicates with gdbreplay via tcp,
 119 regardless of whether the original session was via a serial link or tcp.
 120
 121 Once you are done with the remote debug session, start gdbreplay and
 122 tell it the name of the log file and the host and port number that gdb
 123 should connect to (typically the same as the host running gdb):
 124
 125         $ gdbreplay logfile host:port
 126
 127 Then 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
 132 Repeat the same sequence of user commands to gdb that you gave in the
 133 original debug session.  Gdb should not be able to tell that it is talking
 134 to gdbreplay rather than a real target, all other things being equal.  Note
 135 that gdbreplay echos the command lines to stderr, as well as the contents of
 136 the packets it sends and receives.  The last command echoed by gdbreplay is
 137 the next command that needs to be typed to gdb to continue the session in
 138 sync with the original session.