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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 7 Dec 2021 16:05:33 -0800
Message-ID: <CAKwvOdk2Z2-GQZ3rxHzdYQGVw2G-w0BmbiwDb_PCDzQaw6MdXw@mail.gmail.com>
Subject: Re: [PATCH 15/19] Kbuild: add Rust support
To:     Wedson Almeida Filho <wedsonaf@google.com>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        linux-kbuild@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Alex Gaynor <alex.gaynor@gmail.com>,
        Finn Behrens <me@kloenk.de>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Gary Guo <gary@garyguo.net>,
        Boris-Chengbiao Zhou <bobo1239@web.de>,
        Boqun Feng <boqun.feng@gmail.com>,
        Douglas Su <d0u9.su@outlook.com>,
        Dariusz Sosnowski <dsosnowski@dsosnowski.pl>,
        Antonio Terceiro <antonio.terceiro@linaro.org>,
        Daniel Xu <dxu@dxuuu.xyz>
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On Tue, Dec 7, 2021 at 3:25 PM Wedson Almeida Filho <wedsonaf@google.com> wrote:
>
> On Tue, 7 Dec 2021 at 23:21, Nick Desaulniers <ndesaulniers@google.com> wrote:
> >
> > On Tue, Dec 7, 2021 at 2:45 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
> > >
> > > On Mon, Dec 6, 2021 at 6:07 AM Miguel Ojeda <ojeda@kernel.org> wrote:
> > > >
> > >
> > > ... snip ...
> > >
> > > Miguel and team,
> > > I'm happy to see progress here! Just some quick notes after a first pass.
> > >
> > > Testing this series applied on mainline, I see:
> > > $ make LLVM=1 -j72 defconfig
> > > $ grep RUST .config
> > > CONFIG_HAS_RUST=y
> > > CONFIG_RUSTC_VERSION=14000
> > > # CONFIG_RUST is not set
> > > ...
> > > $ make LLVM=1 -j72 menuconfig
> > > # enable CONFIG_RUST
> > > $ make LLVM=1
> > > ...
> > >   CALL    scripts/checksyscalls.sh
> > > error: @path is unstable - use -Z unstable-options to enable its use
> > >
> > > error: @path is unstable - use -Z unstable-options to enable its use
> > > $ rustc --version
> > > rustc 1.40.0 (73528e339 2019-12-16)
> > >
> > > Can we update some Kconfig checks to fix that?
> >
> > After now reading though the Documentation/ patch:
> >
> > $ rustup update
> > $ rustc --version
> > rustc 1.57.0 (f1edd0429 2021-11-29)
> > $ make LLVM=1 -j72
> > ...
> > make[1]: *** No rule to make target
> > '/usr/local/google/home/ndesaulniers/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/lib.rs',
> > needed by 'rust/core.o'.  Stop.
>
> Can you run `rustup component add rust-src`?
>
> When we change the compiler version, we need to install the source
> code for `core` for the new version. (We'll update the documentation
> to reflect that.)

Cool, yeah please add that to the docs.  Kconfig checks should be
added to make this idiot-proof; starting from everything uninstalled,
I should be able to read the Kconfig dependencies in `make menuconfig`
to understand what I'm missing. And if I'm missing anything, I
shouldn't be able to select CONFIG_RUST.

I get slightly further now.

$ make LLVM=1 -j72
...
  BINDGEN rust/bindings_helpers_generated.rs
thread 'main' panicked at 'called `Result::unwrap()` on an `Err`
value: "could not run executable `/android0/llvm-project/clang`:
Permission denied (os error 13)"',
/usr/local/google/home/ndesaulniers/.cargo/registry/src/github.com-1ecc6299db9ec823/clang-sys-1.3.0/src/support.rs:196:58
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'main' panicked at 'called `Result::unwrap()` on an `Err`
value: "could not run executable `/android0/llvm-project/clang`:
Permission denied (os error 13)"',
/usr/local/google/home/ndesaulniers/.cargo/registry/src/github.com-1ecc6299db9ec823/clang-sys-1.3.0/src/support.rs:196:58
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
make[1]: *** [rust/Makefile:261: rust/bindings_helpers_generated.rs] Error 1
make[1]: *** Deleting file 'rust/bindings_helpers_generated.rs'
make[1]: *** Waiting for unfinished jobs....
make[1]: *** [rust/Makefile:248: rust/bindings_generated.rs] Error 1
make[1]: *** Deleting file 'rust/bindings_generated.rs'
make: *** [Makefile:1271: prepare0] Error 2

It looks like bindgen found part of the path to llvm-project that I
have checked out to disk for when I do development on LLVM for work.
So this might only be an issue if folks have a copy of clang built
from source in their $PATH?

$ which clang
/android0/llvm-project/llvm/build/bin/clang

Looking at the output of `make LLVM=1 -j72 V=1`, I see two invocations
of bindgen, and can repro if I just run the full command manually.

I don't see my path to my source code checkout of llvm-project in the
command line invocation of bindgen; this might be an issue itself with
bindgen.

Googling for "could not run executable" and bindgen, I find this
thread with a similar failure string:
https://bugzilla.mozilla.org/show_bug.cgi?id=1363655
No hits in their issue tracker: https://github.com/rust-lang/rust-bindgen.

$ bindgen --version
bindgen 0.59.2
$ cargo install --locked --version 0.56.0 bindgen
$ bindgen --version
bindgen 0.56.0
$ make LLVM=1 -j72
# produces the same error.

I guess the error is coming not from bindgen, but a dependency of its;
"clang-sys?"
https://github.com/KyleMayes/clang-sys/blob/master/src/support.rs

I've filed an issue in
https://github.com/KyleMayes/clang-sys/issues/138; let's follow up
there?
-- 
Thanks,
~Nick Desaulniers