* It doesn't matter if `rustc` is available, but if rustc can compile to
the hostPlatform. So use a custom condition instead of `availableOn`.
* Explicitly exclude the combination of GCC and riscv which is known
to be broken[1].
[1] https://lore.kernel.org/lkml/31885EDD-EF6D-4EF1-94CA-276BA7A340B7@kernel.org/T/
Co-authored-by: Alyssa Ross <hi@alyssa.is>
This breaks the build like this:
/nix/store/f3k0rdhcd2cx57phx755c2xixgifw5m5-binutils-2.42/bin/ld: Unexpected GOT/PLT entries detected!
/nix/store/f3k0rdhcd2cx57phx755c2xixgifw5m5-binutils-2.42/bin/ld: Unexpected run-time procedure linkages detected!
/nix/store/f3k0rdhcd2cx57phx755c2xixgifw5m5-binutils-2.42/bin/ld: fs/nfs/localio.o: in function `nfs_local_iocb_alloc':
/build/source/build/../fs/nfs/localio.c:290:(.text+0x324): undefined reference to `nfs_to'
[...]
Reported as https://lore.kernel.org/all/D4OUJRP8YWRM.ATQ7KASTYX5H@mbosch.me/
The first assumption[1] we had was that the `aarch64-unknown-none`
target was missing from rustc and that this was the cause for the
regression.
However, it turns out that the relevant code from `rustc` wasn't used
anyways because the Makefile does `--sysroot /dev/null`[2] which prevents
rustc from using its own libcore. So luckily we don't have to patch the
Rust bootstrap to get aarch64-linux back working[3].
In fact, the Rust part seems broken for both 6.10 and 6.11[4], but I
decided to not bother since none of those are longterm versions.
So all that's left here is to enable Rust for aarch64-linux because it
clearly works[5].
[1] https://github.com/NixOS/nixpkgs/pull/315121#issuecomment-2135805876
[2] https://lore.kernel.org/all/20231031201752.1189213-1-mmaurer@google.com/
[3] Of course I only realized this _after_ I spent some time hacking a rustc
patch together 🙃
[4] This broke with
error[E0463]: can't find crate for `core`
|
= note: the `aarch64-unknown-none` target may not be installed
= help: consider downloading the target with `rustup target add aarch64-unknown-none`
= help: consider building the standard library from source with `cargo build -Zbuild-std`
[5] While the build is fine, the VM tests are still panicking, but
that's also the case for `kernel-generic` because of a 9p
regression:
switch_root: can't execute '/nix/store/zv87gw0yxfsslq0mcc35a99k54da9a4z-nixos-system-machine-test/init': Exec format error
[ 1.734997] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000100
[ 1.736002] CPU: 0 UID: 0 PID: 1 Comm: switch_root Not tainted 6.12.0-rc1 #1-NixOS
[...]
Reported as https://lore.kernel.org/all/D4LHHUNLG79Y.12PI0X6BEHRHW@mbosch.me/T/#u
