Hi Arnd, On Fri, 2024-10-25 at 09:55 +0000, Arnd Bergmann wrote: > I think the idea of using the generic syscall ABI (in particular > the time64-only variant) makes sense if there is going to be a > new ABI, and I can help figure out what needs to be done in the > kernel for that.
I don't actually know whether this would be a completely new ABI as m68k has supported 32-bit alignment through the "-malign-int" switch for a long time. > The question is really if it's already too late to do it now, > given the scope of the project and the limited developer > resources. Maintaining two ABIs in the kernel and toolchain > longterm is likely going to make things harder, and phasing > out the existing ABI completely will likely take more than > a decade. I expect that this is the same timeframe (mid-2030s) > by which we will be debating the removal of any 32-bit > targets from the kernel, in particular if we also want to > add 128-bit targets. I was not talking about maintaining two separate ABIs and I don't think it makes much sense to keep the old ABI around. > Based on those experiences, I think there is a significant > chance that adding a new ABI is going to make things harder > to maintain for both distro and kernel maintainers rather > than easier, regardless of how much better the new ABI is. The m68k port is already half broken because of the 16-bit alignment and I have to admit I starting to get tired of people telling me that switching the default alignment is a bad idea. A current example is Python 3.13 which just crashes with the default alignment but builds just fine with "-malign-int". I really don't understand why there is such a big resistance of switching a port over to a different alignment which allegedly no one is using or maintaining. Someone made a bad design decision 40 years ago and we're not allowed to fix that because someone might run an old binary from the 80ies on a current version of the Linux kernel. > I also expect that a lot of users (of m68k kernels) are > never going to get the benefits as they are already stuck on > older userspace because of added bloat in new software > releases. I assume you have better understanding than me > of what m68k hardware is commonly used these days, and > how constrained that is in practice. Users with very slow hardware and without accelerators aren't going to run a modern kernel anyway, so this argument is moot. Adrian -- .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
