Debugging Epiphany

e-server

(Work in progress)

Start e-server

Start e-server in one terminal.

$ e-server --multiprocess

Start a program

In a second terminal we start a host program:
Let's use e-prime from epiphany-examples for this tutorial.

Build the e-prime:

$ cd ~/epiphany-examples/apps/e-prime
$ git pull
$ ./build.sh

Start the program. EHAL_GDBSERVER will make e-hal start any epiphany program in a halted debug mode. This is useful if you want to be able to debug a program from the beginning.

$ EHAL_GDBSERVER=yes ./run.sh

You will notice that e-prime reports 0 primes factored / s. This is because the epiphany cores are not running yet, because of EHAL_GDBSERVER. The next step is to attach with the e-gdb client and start debugging.

gdb

In a third terminal, start e-gdb. You can either do this on your parallella or on your local computer if you have esdk-2016.11.x86_64 installed.

$ cd ~/epiphany-examples/apps/e-prime
$ epiphany-elf-gdb e_prime.elf

Enable non-stop mode. This must to be done before connecting to e-server. We also need to disable pagination as it breaks non-stop.

(gdb) set pagination off
(gdb) set non-stop on

Connect to the e-server. You'll need to adjust localhost to parallella.local. if you use e-gdb from your local computer.

(gdb) target extended-remote localhost:51000

List processes:

(gdb) info os processes

Attach to the default process (workgroup). The default process contains all cores that have not yet been manually assigned to a workgroup. To create a new process, use the monitor workgroup command. The syntax is monitor workgroup [ROW0] [COL0] [ROWS] [COLS].

(gdb) attach 1

Stop all processes:

(gdb) interrupt -a

Show status for all threads:

(gdb) info threads

Switch to thread 7:

(gdb) thread 7

Print backtrace for current thread:

(gdb) bt

Set a breakpoint (will be applied to all threads):

(gdb) b is_prime

Continue all threads:

(gdb) c -a

Print local variables:

(gdb) info locals

Print function arguments:

(gdb) info args