Step through the following procedure in order to start remote debugging with gdbserver:

• Go to the top of your Linux i.MX6 installation and activate the cross development environment:

[sasha@liman linux-imx6sx-2.3.3]$ . ./ACTIVATE.sh

• Make sure your target board has TCP/IP configured and up in Linux:

~ # ifconfig 
eth0      Link encap:Ethernet  HWaddr 3C:FB:96:02:04:9B  
          inet addr:192.168.0.66  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:13108 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10853 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1475879 (1.4 MiB)  TX bytes:1121568 (1.0 MiB)

• It is recommended to rebuild your application (see attached for example) with special GCC options. Use the following options:

[sasha@liman app]$ $CC -o app app.c -O0 -g

• Deploy your application binary (app) to the target. For example, you can scp it or add to the initramfs image:

[sasha@liman app]$ scp app 
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 :/tmp/
app                                           100%   10KB  10.4KB/s   00:00

• Run gdbserver on the target:

~ # gdbserver :1234 /tmp/app
Process /tmp/app created; pid = 527
Listening on port 1234

• Run GDB on the development host:

[sasha@liman app]$ arm-poky-linux-gnueabi-gdb ./app
GNU gdb (GDB) 7.8.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "--host=i686-pokysdk-linux --
target=arm-poky-linux-gnueabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
.
Find the GDB manual and other documentation resources online at:
.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./app...done.
(gdb) 

• Specify the sysroot directory containing copies of the target libraries:

(gdb) set sysroot /opt/poky/1.8.1/sysroots/\
cortexa5hf-vfp-neon-poky-linux-gnueabi
(gdb) 

• Establish a connection to the target:

(gdb) target remote 192.168.0.66:1234
Remote debugging using 192.168.0.66:1234
Reading symbols from /opt/poky/1.8.1/sysroots/cortexa5hf-vfp-neon-poky-
linux-gnueabi/lib/ld-linux-armhf.so.3...Reading symbols from /opt/poky/
1.8.1/sysroots/cortexa5hf-vfp-
neon-poky-linux-gnueabi/lib/.debug/ld-2.21.so...done.
done.
Loaded symbols for /opt/poky/1.8.1/sysroots/cortexa5hf-vfp-neon-poky-
linux-gnueabi/lib/ld-linux-armhf.so.3
0x76fd7b00 in _start ()
   from /opt/poky/1.8.1/sysroots/cortexa5hf-vfp-neon-poky-linux-gnueabi
/lib/ld-linux-armhf.so.3
(gdb) 

• Debug your application using the standard GDB commands. Here is a sample debug session:

(gdb) b main
Breakpoint 1 at 0x8490: file app.c, line 16.
(gdb) c
Continuing.
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?

Breakpoint 1, main () at app.c:16
16              a = 10;
(gdb) n
18              b = 20;
(gdb) p a
$1 = 10
(gdb) n
20              ret = func(a,b);
(gdb) p b
$2 = 20
(gdb) s
func (a=10, b=20) at app.c:5
5               int c = (a+b)/2;
(gdb) n
7               printf("%s: (%d + %d)/2 = %d\n", __func__, a, b, c);
(gdb) p c
$3 = 15
(gdb) bt
#0  func (a=10, b=20) at app.c:7
#1  0x000084ac in main () at app.c:20
(gdb) n
9               return c;
(gdb) n
10      }
(gdb) fini
Run till exit from #0  func (a=10, b=20) at app.c:10
0x000084ac in main () at app.c:20
20              ret = func(a,b);
Value returned is $4 = 15
(gdb) 

The linux-vdso warning above is benign and can be ignored.