gdbserver - Unix, Linux Command

Usage (server (target) side):


First, you need to have a copy of the program you want to debug put onto
the target system.  The program can be stripped to save space if needed, as
GDBserver doesn’t care about symbols.  All symbol handling is taken care of by
the GDB running on the host system.


To use the server, you log on to the target system, and run the ‘gdbserver’
program.  You must tell it (a) how to communicate with GDB, (b) the name of
your program, and (c) its arguments.  The general syntax is:


        target> gdbserver COMM PROGRAM [ARGS ...]


For example, using a serial port, you might say:


        target> gdbserver /dev/com1 emacs foo.txt


This tells gdbserver to debug emacs with an argument of foo.txt, and to
communicate with GDB via /dev/com1.  Gdbserver now waits patiently for the
host GDB to communicate with it.


To use a TCP connection, you could say:


        target> gdbserver host:2345 emacs foo.txt


This says pretty much the same thing as the last example, except that we are
going to communicate with the host GDB via TCP.  The ‘host:2345’ argument means
that we are expecting to see a TCP connection from ‘host’ to local TCP port
2345.  (Currently, the ‘host’ part is ignored.)  You can choose any number you
want for the port number as long as it does not conflict with any existing TCP
ports on the target system.  This same port number must be used in the host
GDBs ‘target remote’ command, which will be described shortly.  Note that if
you chose a port number that conflicts with another service, gdbserver will
print an error message and exit.


On some targets, gdbserver can also attach to running programs.
This is accomplished via the --attach argument.  The syntax is:


        target> gdbserver COMM --attach PID


PID is the process ID of a currently running process.  It isn’t
necessary to point gdbserver at a binary for the running process.


Usage (host side):


You need an unstripped copy of the target program on your host system, since
GDB needs to examine it’s symbol tables and such.  Start up GDB as you normally
would, with the target program as the first argument.  (You may need to use the
--baud option if the serial line is running at anything except 9600 baud.)
Ie: ‘gdb TARGET-PROG’, or ‘gdb --baud BAUD TARGET-PROG’.  After that, the only
new command you need to know about is ‘target remote’.  It’s argument is either
a device name (usually a serial device, like ‘/dev/ttyb’), or a HOST:PORT
descriptor.  For example:


        (gdb) target remote /dev/ttyb


communicates with the server via serial line /dev/ttyb, and:


        (gdb) target remote the-target:2345


communicates via a TCP connection to port 2345 on host ‘the-target’, where
you previously started up gdbserver with the same port number.  Note that for
TCP connections, you must start up gdbserver prior to using the ‘target remote’
command, otherwise you may get an error that looks something like
‘Connection refused’.

Remote debugging is particularly useful in cases of embedded applications where resources are scarce. 
So in such cases the program can run on the target machine and you can debug it from remote host machine.
Below are steps involved in debugging with gdbserver
$ gdbserver localhost:2000 gdb_example -l 20 -b 10
Process gdb_example created; pid = 4674
Listening on port 2000

$ gcc -o gdb_example -g gdb_example.c

$ gdb -q gdb_example
Reading symbols from /home/gdb_example...done.
(gdb)

(gdb) target remote 15.77.28.37:2000

$ gdbserver localhost:2000 gdb_example -l 20 -b 10
Process gdb_example created; pid = 4674
Listening on port 2000
Remote debugging from host 15.77.28.36
Area: 20 * 10 = 200

Child exited with status 0
GDBserver exiting

$ gdb -q gdb_example
Reading symbols from /home/gdb_example...done.
(gdb) target remote 15.77.28.37:2000
Remote debugging using 15.77.28.37:2000
Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/ld-linux.so.2
0x00ab3810 in _start () from /lib/ld-linux.so.2
(gdb) b main
Breakpoint 1 at 0x80484fd: file gdb_example.c, line 18.
(gdb) c
Continuing.

Breakpoint 1, main (argc=5, argv=0xbfff8724) at gdb_example.c:18
18              if (argc != 5) {
(gdb) n
23              while ((c = getopt (argc, argv, "l:b:")) != -1) {
(gdb) n
24                      switch( c ) {
(gdb) c
Continuing.

Program exited normally.


    129 Lectures 
     23 hours 

 Eduonix Learning Solutions

    5 Lectures 
     4.5 hours 

 Frahaan Hussain

    35 Lectures 
     2 hours 

 Pradeep D

    41 Lectures 
     2.5 hours 

 Musab Zayadneh

    46 Lectures 
     4 hours 

 GUHARAJANM

    6 Lectures 
     4 hours 

 Uplatz
 Print
 Add Notes
 Bookmark this page