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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 | Usage (host side): | |
48 | ||
49 | You need an unstripped copy of the target program on your host system, since | |
50 | GDB needs to examine it's symbol tables and such. Start up GDB as you normally | |
51 | would, with the target program as the first argument. (You may need to use the | |
52 | --baud option if the serial line is running at anything except 9600 baud.) | |
53 | Ie: `gdb TARGET-PROG', or `gdb --baud BAUD TARGET-PROG'. After that, the only | |
54 | new command you need to know about is `target remote'. It's argument is either | |
55 | a device name (usually a serial device, like `/dev/ttyb'), or a HOST:PORT | |
56 | descriptor. For example: | |
57 | ||
58 | (gdb) target remote /dev/ttyb | |
59 | ||
60 | communicates with the server via serial line /dev/ttyb, and: | |
61 | ||
62 | (gdb) target remote the-target:2345 | |
63 | ||
64 | communicates via a TCP connection to port 2345 on host `the-target', where | |
65 | you previously started up gdbserver with the same port number. Note that for | |
66 | TCP connections, you must start up gdbserver prior to using the `target remote' | |
67 | command, otherwise you may get an error that looks something like | |
68 | `Connection refused'. | |
69 | ||
70 | Building: | |
71 | ||
72 | Configuring gdbserver you should specify the same machine for host and | |
73 | target (which are the machine that gdbserver is going to run on. This | |
74 | is not the same as the machine that gdb is going to run on; building | |
75 | gdbserver automatically as part of building a whole tree of tools does | |
76 | not currently work if cross-compilation is involved (we don't get the | |
77 | right CC in the Makefile, to start with)). | |
78 | ||
79 | gdbserver should work on sparc-sun-sunos4* or Lynx. The following | |
80 | instructions pertain to Lynx. To build the server for Lynx, make a | |
81 | new copy of the distribution onto a disk that is NFS shared with the | |
82 | Lynx system. Lets say that's in a directory called xyzzy. Then, | |
83 | follow these steps under the host system: | |
84 | ||
85 | 1) cd xyzzy/gdb/gdbserver | |
86 | 2) ../../configure i386-none-lynx | |
87 | ||
88 | When that completes, do the following on the Lynx system: | |
89 | ||
90 | 3) cd xyzzy/gdb/gdbserver | |
91 | 4) make CC=gcc | |
92 | ||
93 | It should build with only a minor complaint about NULL being redefined. That's | |
94 | a LynxOS problem, and can be ignored. | |
95 | ||
96 | It's also possible that you may have a cross-compiler to Lynx. In that case, | |
97 | you can skip the stuff about NFS. You would replace steps 3 & 4 with: | |
98 | ||
99 | make CC=lynx-target-compiler... | |
100 | ||
101 | Using GDBreplay: | |
102 | ||
103 | A special hacked down version of gdbserver can be used to replay remote | |
104 | debug log files created by gdb. Before using the gdb "target" command to | |
105 | initiate a remote debug session, use "set remotelogfile <filename>" to tell | |
106 | gdb that you want to make a recording of the serial or tcp session. Note | |
107 | that when replaying the session, gdb communicates with gdbreplay via tcp, | |
108 | regardless of whether the original session was via a serial link or tcp. | |
109 | ||
110 | Once you are done with the remote debug session, start gdbreplay and | |
111 | tell it the name of the log file and the host and port number that gdb | |
112 | should connect to (typically the same as the host running gdb): | |
113 | ||
114 | $ gdbreplay logfile host:port | |
115 | ||
116 | Then start gdb (preferably in a different screen or window) and use the | |
117 | "target" command to connect to gdbreplay: | |
118 | ||
119 | (gdb) target remote host:port | |
120 | ||
121 | Repeat the same sequence of user commands to gdb that you gave in the | |
122 | original debug session. Gdb should not be able to tell that it is talking | |
123 | to gdbreplay rather than a real target, all other things being equal. Note | |
124 | that gdbreplay echos the command lines to stderr, as well as the contents of | |
125 | the packets it sends and receives. The last command echoed by gdbreplay is | |
126 | the next command that needs to be typed to gdb to continue the session in | |
127 | sync with the original session. |