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Message-ID: <20240902182833.GA514@openwall.com>
Date: Mon, 2 Sep 2024 20:28:33 +0200
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: How to debug segmentation fault using OpenCL and ROCM
Hi Andrea,
On Mon, Sep 02, 2024 at 08:01:09PM +0200, Andrea wrote:
> I have just recently started to learn using JtR tool and I would like to
> enable OpenCL capabilities.
>
> Unfortunately, running some tests, I'm always getting segmentation fault
> error; I would like to understand the best way to debug the issue and
> track it down to understand if the issue is related to either ROCM,
> OpenCL or JtR (or a mix of them).
In our experience, on AMD GPUs it is "normal" to have a few failing
formats. So if you run tests of many/all formats and only a few fail,
you just accept it's that way with your current combination of GPU and
driver. AMD's software is just poor.
We sometimes try and workaround individual bugs, but we've long since
accepted that some formats will be failing on AMD. If you want all to
work at once (with the same driver version, etc.), get NVIDIA. We do
get to 100% passing tests on NVIDIA, but (as I recall) never on AMD.
That said, it is also possible that in your case the problem is
different. So if you determine that _all_ formats are failing like
that, then it makes sense to look into the cause (e.g., incorrect driver
or JtR installation) and fix that. From your testing of just one
format, we can't tell.
> Example of command and related error:
>
> john --test=0 --format=sha256crypt-opencl
>
> Device 1: gfx90c:xnack- [AMD Radeon Graphics]
> Testing: sha256crypt-opencl, crypt(3) $5$ (rounds=5000) [SHA256
> OpenCL]... Build log: warning: argument unused during compilation: '-I
> opencl' [-Wunused-command-line-argument]
> 1 warning generated.
> Segmentation fault
It is unusual that this specific format fails. It normally works:
$ ./john --test=0 --format=sha256crypt-opencl
Device 1: gfx900 [Radeon RX Vega]
Testing: sha256crypt-opencl, crypt(3) $5$ (rounds=5000) [SHA256 OpenCL]... PASS
So please try testing other formats.
Alexander
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