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 For more information about GDBserver, see the GDB manual.
  13
  14 Usage (server (target) side):
  15
  16 First, you need to have a copy of the program you want to debug put onto
  17 the target system.  The program can be stripped to save space if needed, as
  18 GDBserver doesn't care about symbols.  All symbol handling is taken care of by
  19 the GDB running on the host system.
  20
  21 To use the server, you log on to the target system, and run the `gdbserver'
  22 program.  You must tell it (a) how to communicate with GDB, (b) the name of
  23 your program, and (c) its arguments.  The general syntax is:
  24
  25         target> gdbserver COMM PROGRAM [ARGS ...]
  26
  27 For example, using a serial port, you might say:
  28
  29         target> gdbserver /dev/com1 emacs foo.txt
  30
  31 This tells GDBserver to debug emacs with an argument of foo.txt, and to
  32 communicate with GDB via /dev/com1.  GDBserver now waits patiently for the
  33 host GDB to communicate with it.
  34
  35 To use a TCP connection, you could say:
  36
  37         target> gdbserver host:2345 emacs foo.txt
  38
  39 This says pretty much the same thing as the last example, except that we are
  40 going to communicate with the host GDB via TCP.  The `host:2345' argument means
  41 that we are expecting to see a TCP connection from `host' to local TCP port
  42 2345.  (Currently, the `host' part is ignored.)  You can choose any number you
  43 want for the port number as long as it does not conflict with any existing TCP
  44 ports on the target system.  This same port number must be used in the host
  45 GDBs `target remote' command, which will be described shortly.  Note that if
  46 you chose a port number that conflicts with another service, GDBserver will
  47 print an error message and exit.
  48
  49 On some targets, GDBserver can also attach to running programs.  This is
  50 accomplished via the --attach argument.  The syntax is:
  51
  52         target> gdbserver --attach COMM PID
  53
  54 PID is the process ID of a currently running process.  It isn't necessary
  55 to point GDBserver at a binary for the running process.
  56
  57 Usage (host side):
  58
  59 You need an unstripped copy of the target program on your host system, since
  60 GDB needs to examine it's symbol tables and such.  Start up GDB as you normally
  61 would, with the target program as the first argument.  (You may need to use the
  62 --baud option if the serial line is running at anything except 9600 baud.)
  63 Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'.  After that, the only
  64 new command you need to know about is `target remote'.  It's argument is either
  65 a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT
  66 descriptor.  For example:
  67
  68         (gdb) target remote /dev/ttyb
  69
  70 communicates with the server via serial line /dev/ttyb, and:
  71
  72         (gdb) target remote the-target:2345
  73
  74 communicates via a TCP connection to port 2345 on host `the-target', where
  75 you previously started up GDBserver with the same port number.  Note that for
  76 TCP connections, you must start up GDBserver prior to using the `target remote'
  77 command, otherwise you may get an error that looks something like
  78 `Connection refused'.
  79
  80 Building GDBserver:
  81
  82 The supported targets as of November 2006 are:
  83         arm-*-linux*
  84         bfin-*-uclinux
  85         bfin-*-linux-uclibc
  86         crisv32-*-linux*
  87         cris-*-linux*
  88         i[34567]86-*-cygwin*
  89         i[34567]86-*-linux*
  90         i[34567]86-*-mingw*
  91         ia64-*-linux*
  92         m32r*-*-linux*
  93         m68*-*-linux*
  94         m68*-*-uclinux*
  95         mips*64*-*-linux*
  96         mips*-*-linux*
  97         powerpc[64]-*-linux*
  98         s390[x]-*-linux*
  99         sh-*-linux*
 100         spu*-*-*
 101         x86_64-*-linux*
 102
 103 Configuring GDBserver you should specify the same machine for host and
 104 target (which are the machine that GDBserver is going to run on.  This
 105 is not the same as the machine that GDB is going to run on; building
 106 GDBserver automatically as part of building a whole tree of tools does
 107 not currently work if cross-compilation is involved (we don't get the
 108 right CC in the Makefile, to start with)).
 109
 110 Building GDBserver for your target is very straightforward.  If you build
 111 GDB natively on a target which GDBserver supports, it will be built
 112 automatically when you build GDB.  You can also build just GDBserver:
 113
 114         % mkdir obj
 115         % cd obj
 116         % path-to-gdbserver-sources/configure
 117         % make
 118
 119 If you prefer to cross-compile to your target, then you can also build
 120 GDBserver that way.  In a Bourne shell, for example:
 121
 122         % export CC=your-cross-compiler
 123         % path-to-gdbserver-sources/configure your-target-name
 124         % make
 125
 126 Using GDBreplay:
 127
 128 A special hacked down version of GDBserver can be used to replay remote
 129 debug log files created by GDB.  Before using the GDB "target" command to
 130 initiate a remote debug session, use "set remotelogfile <filename>" to tell
 131 GDB that you want to make a recording of the serial or tcp session.  Note
 132 that when replaying the session, GDB communicates with GDBreplay via tcp,
 133 regardless of whether the original session was via a serial link or tcp.
 134
 135 Once you are done with the remote debug session, start GDBreplay and
 136 tell it the name of the log file and the host and port number that GDB
 137 should connect to (typically the same as the host running GDB):
 138
 139         $ gdbreplay logfile host:port
 140
 141 Then start GDB (preferably in a different screen or window) and use the
 142 "target" command to connect to GDBreplay:
 143
 144         (gdb) target remote host:port
 145
 146 Repeat the same sequence of user commands to GDB that you gave in the
 147 original debug session.  GDB should not be able to tell that it is talking
 148 to GDBreplay rather than a real target, all other things being equal.  Note
 149 that GDBreplay echos the command lines to stderr, as well as the contents of
 150 the packets it sends and receives.  The last command echoed by GDBreplay is
 151 the next command that needs to be typed to GDB to continue the session in
 152 sync with the original session.