Re: [PATCH v2] x86: Start removing X86_X32_ABI

[John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>]

Hello,

On Tue, 2026-07-07 at 23:22 +0200, Sebastian Andrzej Siewior wrote:
> The x32 ABI was introduced in v3.4 to leverage the additional registers
> which were available on x86_64 but not on i386 while keeping the smaller
> 32bit pointers.
> 
> This did not take off. The memory usage usually knows no limit and the
> better performance did not reach a point where certain workloads widely
> move to x32 and use it exclusively. In the meantime Debian introduced a
> patch to disable x32 by default (so it has to be enabled at boot time on
> the command line) because they are afraid of the increased attack
> surface. Fedora as far as I tell has X32 disabled (looking at 7.0-rc5
> rpm in rawhide).
> 
> The syscall range >512 used by x32 can not be reused because on earlier
> kernels (before v5.4 with x32 enabled, see commit 6365b842aae4
> ("x86/syscalls: Split the x32 syscalls into their own table") it is not
> obvious if the syscall is for x86-64 and not implemented or meant for
> x32.
> What can be removed are the special compat cases due to different
> alignment.
> 
> Since there is practically no real use for x32, start removing it by
> removing the symbol first, not allowing to enable it. Should nothing
> happening by the end of the year, it will removed after the last LTS
> kernel this year.

As mentioned before, there are still actively maintained Debian and Gentoo
ports of x32, so I guess the last paragraph is rather subjective.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
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