Hello Kevin, On Thu, Mar 09, 2023 at 01:52:41PM -0800, Kevin Hilman wrote: > 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. You are totally right. It's one of the possible ways. But in the our internal project we build kernel + roofs + uboot together in the one buildroot project ('repo' based). So we will try to stay in the such paradigm, but will use multi-arch toolchain, maybe. Anyway, thanks a lot for sharing your experience. -- Thank you, Dmitry
