Rust stalks IBM mainframes, but only in nightly form

"Engineer Jan Polensky has submitted a patch series titled “s390: enable Rust support and add required arch glue.” If accepted, it will allow Rust code to be used in the Linux kernel on IBM mainframe hardware, which the kernel still refers to as s390 after the generation of IBM mainframe kit introduced in 1990. He notes: “For now, using a nightly build of the Rust compiler does not sound to us like the sort of thing many conservative mainframe shops are likely to embrace with enthusiasm, but even big new features have to start somewhere.”"

"When Rust was introduced into the kernel in 2022, The Register mentioned a problem that we rarely see raised elsewhere: while the kernel is generally compiled with GCC, the standard Rust compiler, rustc, is based on LLVM instead. Wikipedia has a list of LLVM backends, and although there are a growing number, it's a shorter list than GCC's 48. There is an experimental GCC front-end for Rust but it's not ready for the prime time yet."

"The Linux kernel itself has supported compilation using LLVM since kernel 6.9 over two years ago. At the moment, the kernel development team is still working on version 7.1, which at the time of writing is still on release candidate 3 - so relatively early days. Last month, we reported on its new NTFS driver and the removal of some fairly ancient hardware support."

"The final version of Linux 7.1 will probably appear about halfway through 2026, meaning that kernel 7.2 is still quite far off. It might be in time to appear in Ubuntu 26.10 - but then again, we suspect that very few IBM mainframe customers use interim Ubuntu releases."

A patch series titled “s390: enable Rust support and add required arch glue” would allow Rust code to be used in the Linux kernel on IBM mainframe hardware. The kernel targets the s390 architecture name for IBM mainframe kit introduced in 1990. Adoption would require comfort with a nightly Rust compiler for now, which may not fit conservative mainframe operational practices. Rust in the kernel relies on rustc, which is LLVM-based, while the kernel is commonly built with GCC. The kernel has supported LLVM-based compilation since version 6.9. Linux development is currently focused on version 7.1, with a likely release around mid-2026.

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