Use safe march flags for AUTOBAHN

[RazvanLiviuVarzaru]

Setting AUTOBAHN_ARCH_TARGET=safe will determine the autobahn nvx sources to be compiled with safe march flags as per:
https://github.com/crossbario/autobahn-python/blob/1c7d45cd2129b1fa6daacb0ed7051448fed3ec0d/src/autobahn/nvx/_compile_args.py#L215

In our scenario the RH10 ARM build compiled
_utf8validator with PAC support, being tricked by the QEMU emulation under buildx. PAC was introduced on ARMv8.3-A while our arm hosts are ARMv8.2-A

The CI built image passes the GH Actions tests under emulation, while on our ARM hosts we can see that it crashes when trying to push the RETAA instruction, during a buildbot-worker startup.

[buildbot@6d98845070da ~]$ twistd --pidfile= -ny /home/buildbot/buildbot.tac
Illegal instruction (core dumped)

=> 0xfffedeb72120 <PyInit__nvx_utf8validator+184>:  retaa

[fauust]

good catch!

[grooverdan]

Yike. Well done. Its a good quick fix for this problem.

cat /proc/sys/fs/binfmt_misc//qemu-aarch64
enabled
interpreter /usr/bin/qemu-aarch64-static
..
$ /usr/bin/qemu-aarch64-static --help
usage: qemu-aarch64 [options] program [arguments...]
Linux CPU emulator (compiled for aarch64 emulation)

Options and associated environment variables:

Argument             Env-variable         Description
-h                                        print this help
-help                                     
-g port              QEMU_GDB             wait gdb connection to 'port'
-L path              QEMU_LD_PREFIX       set the elf interpreter prefix to 'path'
-s size              QEMU_STACK_SIZE      set the stack size to 'size' bytes
-cpu model           QEMU_CPU             select CPU (-cpu help for list)

If QEMU_CPU=cortex-a72 (or what we have) is exposed to buildx and the emulated execution respects this we'll be a bit more protected against future and more subtle build/runtime effects.

[RazvanLiviuVarzaru]

Solved!

@hz-arm-bbw2:~$ docker run -it --rm quay.io/mariadb-foundation/bb-worker:dev_rhel10 bash
[buildbot@42a4e4ba1e9d ~]$ twistd --pidfile= -ny /home/buildbot/buildbot.tac
2026-03-18 09:01:06+0000 [-] Loading /home/buildbot/buildbot.tac...
2026-03-18 09:01:07+0000 [-] Loaded.
2026-03-18 09:01:07+0000 [-] twistd 25.5.0 (/usr/bin/python3 3.12.12) starting up.
2026-03-18 09:01:07+0000 [-] reactor class: twisted.internet.epollreactor.EPollReactor.
2026-03-18 09:01:07+0000 [-] Starting Worker -- version: 4.3.0
2026-03-18 09:01:07+0000 [-] recording hostname in twistd.hostname
2026-03-18 09:01:07+0000 [-] Starting factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
2026-03-18 09:01:07+0000 [-] Scheduling retry 1 to connect <twisted.internet.endpoints.TCP4ClientEndpoint object at 0xffff0f7e4e00> in 2.4361218204535717 seconds.
2026-03-18 09:01:07+0000 [-] Stopping factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
2026-03-18 09:01:09+0000 [-] Starting factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
2026-03-18 09:01:09+0000 [-] Scheduling retry 2 to connect <twisted.internet.endpoints.TCP4ClientEndpoint object at 0xffff0f7e4e00> in 2.964904724448062 seconds.
2026-03-18 09:01:09+0000 [-] Stopping factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
2026-03-18 09:01:12+0000 [-] Starting factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
2026-03-18 09:01:12+0000 [-] Scheduling retry 3 to connect <twisted.internet.endpoints.TCP4ClientEndpoint object at 0xffff0f7e4e00> in 3.4368867318039515 seconds.
2026-03-18 09:01:12+0000 [-] Stopping factory <buildbot_worker.pb.BotFactory object at 0xffff0f7e4c20>
^C2026-03-18 09:01:13+0000 [-] Received SIGINT, shutting down.
2026-03-18 09:01:13+0000 [-] Main loop terminated.
2026-03-18 09:01:13+0000 [-] Server Shut Down.