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From:   Matthew Maurer <mmaurer@google.com>
Date:   Thu, 5 Oct 2023 14:36:19 -0700
Message-ID: <CAGSQo01=UxFmPRo6OTU1443izumvF+Z0fevgdWVdHK6DGTehCQ@mail.gmail.com>
Subject: Re: [PATCH v3] rust: Respect HOSTCC when linking for host
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        Alice Ryhl <aliceryhl@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>, Tom Rix <trix@redhat.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kbuild@vger.kernel.org, llvm@lists.linux.dev
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On Fri, Sep 29, 2023 at 10:59=E2=80=AFPM Masahiro Yamada <masahiroy@kernel.=
org> wrote:
>
> On Fri, Sep 29, 2023 at 4:48=E2=80=AFAM Matthew Maurer <mmaurer@google.co=
m> wrote:
> >
> > Currently, rustc defaults to invoking `cc`, even if `HOSTCC` is defined=
,
> > resulting in build failures in hermetic environments where `cc` does no=
t
> > exist. This includes both hostprogs and proc-macros.
> >
> > Since we are setting the linker to `HOSTCC`, we set the linker flavor t=
o
> > `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, includin=
g
> > both `gcc` and `clang`.
> >
> > Signed-off-by: Matthew Maurer <mmaurer@google.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 =3D $(RUSTC_OR_CLIPPY_QUIET) P $@
> >        cmd_rustc_procmacro =3D \
> >         $(RUSTC_OR_CLIPPY) $(rust_common_flags) \
> > +               -Clinker-flavor=3Dgcc -Clinker=3D$(HOSTCC) \
> > +               -Clink-args=3D'$(subst ','\'',$(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=3Ddep-info=3D$(depfile) --emit=3Dlink=3D$@ --ext=
ern proc_macro \
> >                 --crate-type proc-macro \
> >                 --crate-name $(patsubst lib%.so,%,$(notdir $@)) $<
> > diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> > index 8f7f842b54f9..08d83d9db31a 100644
> > --- a/scripts/Makefile.host
> > +++ b/scripts/Makefile.host
> > @@ -91,6 +91,8 @@ hostcxx_flags  =3D -Wp,-MMD,$(depfile) \
> >  # current working directory, which may be not accessible in the out-of=
-tree
> >  # modules case.
> >  hostrust_flags =3D --out-dir $(dir $@) --emit=3Ddep-info=3D$(depfile) =
\
> > +                -Clinker-flavor=3Dgcc -Clinker=3D$(HOSTCC) \
> > +                -Clink-args=3D'$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
> >                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
> >                   $(HOSTRUSTFLAGS_$(target-stem))
> >
> > --
> > 2.42.0.582.g8ccd20d70d-goog
> >
>
>
> --
> Best Regards
> Masahiro Yamada