Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx> writes: > On Mon, Feb 27, 2023 at 07:19:38PM +0100, Arnd Bergmann wrote: >> On Mon, Feb 27, 2023, at 17:50, Dmitry Rokosov wrote: >> > On Mon, Feb 27, 2023 at 05:38:49PM +0100, Neil Armstrong wrote: >> >> On 27/02/2023 17:15, Arnd Bergmann wrote: >> >> > On Mon, Feb 27, 2023, at 16:51, Dmitry Rokosov wrote: >> >> > >> >> > Most of these don't apply in userspace, so the incentive to >> >> > run smaller 32-bit userland on systems with less than 1GB of >> >> > RAM usually outweighs the benefits of 64-bit userspace. >> >> >> >> Thanks for the details! >> > >> > Looks like Thomas has already prepared a basic patch series for buildroot, >> > but maintainers declined it. >> > >> > https://lore.kernel.org/all/20220730194331.GA2515056@scaer/ >> >> I see. I know very little about buildroot, but it sounds like >> there are other ways of doing the same thing here. In general, >> this is pretty much an Arm specific problem. While you clearly >> want compat mode for small userland on any architecture but don't >> want 32-bit kernels, arm is the only one that has a different >> kernel "ARCH=" value and needs a separate gcc toolchain. >> >> If the problem is only the toolchain, an easy way out may >> be to use clang instead of gcc as your compiler, as a single >> clang binary can target both 32-bit userland and 64-bit kernel >> on all supported architectures. > > Agreed with you. We will try different local approaches to support > compat build configurations. For now, prebuilt toolchain (buildroot make > sdk goal) is best way from my point of view. Anyway, we will try to > solve this problem in the our sandbox and stay on the 64-bit kernel. > Thank you for all the helpful details you shared, appreciate it! Just to clarify one thing... More specifically, this is a buildroot *build system* problem. If you build the kernel separately from the rootfs, it works fine. I use 32-bit buildroot (and debian) rootfs images all the time on Amlogic SoCs with 64-bit kernels and it works fine. Kevin
