Miguel Ojeda sent out his pull request of the new Rust kernel code slated for introduction in Linux 7.4. It's a big one this round due to updating the Zerocopy vendored library plus updating other Rust crates for the kernel.
The Zerocopy crate update is a big one in jumping eight versions ahead. This is the code providing traits and macros to safely convert between raw byte sequences and structured types. Rust for Linux 7.4 also has other toolchain and infrastructure updates, enabling the unstable proc_macro_span feature for better diagnostics of all procedural macros, and more.
The Rust kernel create adds new "mem" and "ratelimit" modules while improving some of the existing modules. The pin-init crate is adding support for tuple structs as well as allowing for the safe creation of self-references. There is also much improved diagnostics.
More details on these central Rust code changes for Linux 7.4 can be found via this pull request. Via individual subsystem pull requests will also be more Rust code for Linux 7.4, like the NVIDIA Nova driver improvements for Linux 7.4 and the other Rust DRM infrastructure work that brings.
it is not the default
The default is GCC, and you need to build the kernel with clang to build the kernel with the rust support, how is possible rust arrives by default? https://docs.kernel.org/rust/quick-start.html
Maybe is the default in your distribution, but is not the default in the kernel
I believe this statement is incompatible with how C works. The kernel can load modules written in any language as long as it outputs a .ko, so there can be no technical requirement for building the rest of the kernel itself with clang.
You can't load modules built with a different compiler. The modules aren't external programs, the modules are literally part of the kernel. And if you want to use a module wrote in rust you also need to have built in the rust support in the kernel
Sure you can. There's even multiple guides for how to write C++ kernel modules, which inherently is going to use a different compiler than what was used for the kernel itself. BOSS Linux even writes C++ kernel modules.
Only if the module uses rust-specific interfaces in the kernel, otherwise it can be assembled into a .ko to have plain C-style symbols loaded by the kernel like normal.
The C and C++ compilers use the same backends (and rust to, llvm), just try to build a module with clang for a kernel build with GCC, or it fails in compile phase or when you try to load the module. You can write a module in the lenguaje that you want if you use the same backend, but if we are talking about avoiding to use a kernel with rust, man is the default in the kernel, just read the config, rust is disabled
I did just now, and it worked fine.