Linux starts killing off the little-used x32 ABI

The Linux kernel is beginning to drop the x32 ABI, the long-neglected hybrid that let 64-bit x86 processors run with 32-bit pointers. Sebastian Andrzej Siewior has posted patches that remove the build option so the feature can no longer be enabled, with the rest of the code slated to go after the last long-term support kernel of the year if no one steps forward.

X32 landed in Linux 3.4 to give programs the extra registers of x86-64 while keeping smaller pointers and a lighter memory footprint. Adoption never followed. Distributions already treat it as optional or off: Debian ships it disabled unless turned on at boot, citing attack surface, and Fedora builds without it. The syscall numbers reserved for x32 cannot be recycled safely on older kernels, but the special compatibility paths can go.

Siewior's series also drops the related nolibc selftest so the test suite does not break once the option disappears. Arnd Bergmann has acked the direction.

Debian developer John Paul Adrian Glaubitz argued for a slower cutover modeled on ia64 removal: leave x32 fully intact through the next LTS release so anyone who still needs it can pin that kernel. Disabling the option now, he said, forces remaining users to notice and speak up quickly, which most will not do because they do not follow kernel development lists or press coverage. Siewior's stated plan is that the disablement commits can simply be reverted if real users appear; otherwise full removal follows the year's final LTS.

For the few workloads still on x32, the practical window to object or migrate is closing with this year's LTS cycle.