could you give the command to get execve on nginx?

[YuxiLing]

Hi, I'm trying to reproduce the experiment of getting execve on nginx. But bopc always returns 0 solution. Could you help provide specific instructions for this program?

The following is the command I tried:

./source/BOPC.py -dd --binary evaluation/nginx1 --source payloads/execve.spl --abstraction load --entry -1 --format gdb

It would be nice if you could point out the mistake above.