On Thu, Jan 18, 2024 at 05:09:40PM +0100, Miguel Ojeda wrote: > On Thu, Jan 18, 2024 at 4:49 PM Conor Dooley <conor@xxxxxxxxxx> wrote: > > > > The bit that worries me most is bindgen, and in particular detecting the > > version of libclang used. I mentioned to Nathan or Nick about needing a > > buildtime test for the version of LIBCLANG being used. > > I'm less worried about this for LLVM=1 builds, since while I think it is > > possible to provide a LIBCLANG path to the build system, I suspect that > > for LLVM=1 builds it's almost always going to match the LLVM toolchain > > in use. I chatted with the clang built linux folks about this yesterday, Nathan agreed that dealing with incompatibility issues iff they crop up is a reasonable way to go. > `scripts/rust_is_available.sh` tests whether `libclang` is at least > the minimum LLVM supported version; and under `LLVM=1` builds, it also > tests whether the `bindgen` found one matches the C compiler. Do you > mean something like that? If by "the bindgen found one matches the C compiler" you mean that the version of libclang used by bindgen matches the C compiler, then that sounds great. > For `bindgen` under GCC builds, we will eventually want a "proper" way > to use GCC instead (or possibly other approaches like querying the > information): https://github.com/rust-lang/rust-bindgen/issues/1949. > Recently, there has been a thread in our Zulip and a couple people are > experimenting: https://rust-for-linux.zulipchat.com/#narrow/stream/288089-General/topic/Bindgen.20--.20GCC.20backend.20port That link for me goes to a message on 22/01, so later than the email you sent. > > I'll do another rebase and resend after the merge window closes I > > suppose :) That said, I gave things another spin today, in a different environment, as a final check before sending and found an issue causing kernel panics. RISC-V (and x86/arm64) supports kcfi (CFI_CLANG) but enabling sanitisers seems to be a nightly only option for rustc. The kernel I built today had CFI_CLANG enabled and that caused panics when the rust samples were loaded. The CFI_CLANG Kconfig entry has a cc-option test for whether the option is supported, but from a quick check I don't see a comparable test to use for rust. Even if a test was added, the current flag is an unstable one, so I am not sure if testing for it is the right call in the first place, given the stabilised flag would be entirely different? The tracking issue seems to be complete: https://github.com/rust-lang/rust/issues/89653 but the tracking issue for sanitisiers themselves is only 3/5: https://github.com/rust-lang/rust/issues/39699 The simple thing would be to make them mutually exclusive options in Kconfig. What do you think? Cheers, Conor.
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