The future of 32-bit support in the kernel [LWN subscriber-only content]
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Arnd Bergmann started his Open Source Summit Europe 2025 talk with a clear statement of position: 32-bit systems are obsolete when it comes to use in any sort of new products. The only reason to work with them at this point is when there is existing hardware and software to support. Since Bergmann is the overall maintainer for architecture support in the kernel, he is frequently asked whether 32-bit support can be removed. So, he concluded, the time has come to talk more about that possibility.
People naturally think about desktop machines first, he continued. If you were running Linux in the 1990s, you had a 32-bit, desktop system. Unix systems, though, moved to 64-bit platforms around 30 years ago, and the Linux desktop made that move about 20 years ago. Even phones and related devices have been 64-bit for the last decade. If those systems were all that Linux had to support, 32-bit support would have long since been removed from the kernel. He summarized the situation with this slide, showing how the non-embedded architectures have transitioned to either 64-bit or nonexistence over time:
The world is not all desktops — or servers — though; embedded Linux exists as well. About 90% of those systems are running on Arm processors. The kernel has accumulated a lot of devicetree files describing those systems over the years; only in this last year has the number of devicetrees for armv8 (64-bit) systems exceeded the number for armv7 (32-bit) systems.
For Arm processors with pre-armv7 architectures, there are only three for which it is still possible to buy hardware, but a number are still supported by the kernel community:
Many other pre-armv7 CPUs are out of production, but the kernel still has support for them. Of those, he said, there are about ten that could be removed now. It would be nice to be able to say that support for the others will be removed after a fixed period, ten years perhaps, but hardware support does not work that way. Instead, one has to think in terms of half lives; every so often, it becomes possible to remove support for half of the platforms. It all depends on whether there are users for the processors in question.
The kernel is still adding support for some 32-bit boards, he said, but at least ten new 64-bit boards gain support for each 32-bit one.
There are a number of non-Arm 32-bit architectures that still have support in the kernel; these include arc, microblaze, nios2, openrisc, rv32, sparc/leon, and xtensa. All of them are being replaced by RISC-V processors in new products. RISC-V is what you use if you don't care about Arm compatibility, he said.
Then, there is the dusty corner where nommu (processors without a memory-management unit) live; these include armv7-m, m68k, superh, and xtensa. Nobody is building anything with this kind of hardware now, and the only people who are working on them in any way are those who have to support existing systems. " Or to prove that it can be done ."
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