We (Sagitta HPC/Terahash) looked into doing OpenCL on Altera FPGA back in 2015 and there were several severe limitations and drawbacks.
The first big issue, which you are running into now, is that there is no JIT compiler. You would need to pre-compile the kernels and then patch Hashcat to load the binary kernels (which is the way oclHashcat used to work before we went open source and switched to JIT compiling.)
The second biggest issue was the driver. Now, this may have changed with Intel's acquisition of Altera. But at the time, driver (1) used an ancient ABI and would only compile on CentOS 5, and (2) could only support one thread.
We got md5stress and oclGaussCrack to work with Altera's OpenCL, but the task of getting Hashcat to work seemed like a massive undertaking, and we shelved it until the state of OpenCL on FPGA improves.
The first big issue, which you are running into now, is that there is no JIT compiler. You would need to pre-compile the kernels and then patch Hashcat to load the binary kernels (which is the way oclHashcat used to work before we went open source and switched to JIT compiling.)
The second biggest issue was the driver. Now, this may have changed with Intel's acquisition of Altera. But at the time, driver (1) used an ancient ABI and would only compile on CentOS 5, and (2) could only support one thread.
We got md5stress and oclGaussCrack to work with Altera's OpenCL, but the task of getting Hashcat to work seemed like a massive undertaking, and we shelved it until the state of OpenCL on FPGA improves.