linux-kernel - Re: [PATCH v3] rust: Respect HOSTCC when linking for host

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Date:   Thu, 5 Oct 2023 14:36:19 -0700
From:   Matthew Maurer <mmaurer@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Andreas Hindborg <a.hindborg@...sung.com>,
        Alice Ryhl <aliceryhl@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>, Tom Rix <trix@...hat.com>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v3] rust: Respect HOSTCC when linking for host

On Fri, Sep 29, 2023 at 10:59 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Fri, Sep 29, 2023 at 4:48 AM Matthew Maurer <mmaurer@...gle.com> wrote:
> >
> > Currently, rustc defaults to invoking `cc`, even if `HOSTCC` is defined,
> > resulting in build failures in hermetic environments where `cc` does not
> > exist. This includes both hostprogs and proc-macros.
> >
> > Since we are setting the linker to `HOSTCC`, we set the linker flavor to
> > `gcc` explicitly. The linker-flavor selects both which linker to search
> > for if the linker is unset, and which kind of linker flags to pass.
> > Without this flag, `rustc` would attempt to determine which flags to
> > pass based on the name of the binary passed as `HOSTCC`. `gcc` is the
> > name of the linker-flavor used by `rustc` for all C compilers, including
> > both `gcc` and `clang`.
> >
> > Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
> > ---
> >  rust/Makefile         | 2 ++
> >  scripts/Makefile.host | 2 ++
> >  2 files changed, 4 insertions(+)
> >
> > diff --git a/rust/Makefile b/rust/Makefile
> > index 87958e864be0..da664d7aed51 100644
> > --- a/rust/Makefile
> > +++ b/rust/Makefile
> > @@ -383,6 +383,8 @@ $(obj)/exports_kernel_generated.h: $(obj)/kernel.o FORCE
> >  quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
> >        cmd_rustc_procmacro = \
> >         $(RUSTC_OR_CLIPPY) $(rust_common_flags) \
> > +               -Clinker-flavor=gcc -Clinker=$(HOSTCC) \
> > +               -Clink-args='$(subst ','\'',$(KBUILD_HOSTLDFLAGS))' \
>
>
>
> Why not consistently use the escsq macro here too ?
>
>
I didn't use it in rust/Makefile because that makefile doesn't
directly import scripts/Kbuild.include, and I was under the mistaken
impression that scripts/ was supposed to be its own namespace, even if
Make wasn't enforcing it. Inspecting other functions in
scripts/Kbuild.include though, it's clear they're called elsewhere, so
I'll upload another version of the patch using escsq here as well.
>
>
>
>
> >                 --emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \
> >                 --crate-type proc-macro \
> >                 --crate-name $(patsubst lib%.so,%,$(notdir $@)) $<
> > diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> > index 8f7f842b54f9..08d83d9db31a 100644
> > --- a/scripts/Makefile.host
> > +++ b/scripts/Makefile.host
> > @@ -91,6 +91,8 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
> >  # current working directory, which may be not accessible in the out-of-tree
> >  # modules case.
> >  hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
> > +                -Clinker-flavor=gcc -Clinker=$(HOSTCC) \
> > +                -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
> >                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
> >                   $(HOSTRUSTFLAGS_$(target-stem))
> >
> > --
> > 2.42.0.582.g8ccd20d70d-goog
> >
>
>
> --
> Best Regards
> Masahiro Yamada