The future of 32-bit Linux [LWN.net]

The future of 32-bit Linux

Posted Mar 15, 2021 22:44 UTC (Mon) by mat2 (guest, #100235)
In reply to: The future of 32-bit Linux by wtarreau
Parent article: The future of 32-bit Linux

"While the CPU was designed to be 64-bit (and I bought it for this reason), this one is limited to 32-bit, and long mode cannot be enabled in the BIOS."

Well, I wonder whether the 64-bit mode is really disabled in the CPU or only hidden in the CPUID flags. If the latter, the computer could be made to run a 64-bit kernel.

Similarly, there are some Pentium M processors that support PAE (Physical Address Extensions), but do not show this support in CPUID. They could be made to run distributions that require PAE with the "forcepae" kernel command line parameter.

This could be tested by removing the verify_cpu check in arch/x86/boot/compressed/head_64.S

to post comments

The future of 32-bit Linux

Posted Mar 16, 2021 13:11 UTC (Tue) by amacater (subscriber, #790) [Link] (1 responses)

A quicker check, maybe, for this situation on an unknown PC: boot the netinst for Debian multi-arch - there are various settings there, one of which is 64 bit kernel and 32 bit userland.

I do remember a Toshiba tablet/convertible PC which was almost exactly this and the multi-arch was the only thing that would boot
it at all.

The future of 32-bit Linux

Posted Mar 16, 2021 18:08 UTC (Tue) by mat2 (guest, #100235) [Link]

This won't work because the 64-bit kernel detects whether the CPU supports the 64-bit mode and refuses to boot otherwise.
So a mixed mode system will not boot, it is necessary to override the check in the kernel.