[PATCH v4] rust: Respect HOSTCC when linking for host

[PATCH v4] rust: Respect HOSTCC when linking for host

[Matthew Maurer]

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@google.com>
---

Edited to use escsq in both Makefiles, as per Masahiro Yamada's
suggestion.

 rust/Makefile         | 2 ++
 scripts/Makefile.host | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/rust/Makefile b/rust/Makefile
index 87958e864be0..2ddd821d9435 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='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
 		--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))
 
-- 
2.42.0.609.gbb76f46606-goog

Re: [PATCH v4] rust: Respect HOSTCC when linking for host

[Martin Rodriguez Reboredo]

On 10/5/23 18:39, Matthew Maurer 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@google.com>
> ---
> [...]
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>

[PATCH v4] rust: Respect HOSTCC when linking for host

[Alice Ryhl]

Matthew Maurer <mmaurer@google.com> writes:
> 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@google.com>

Tested-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v4] rust: Respect HOSTCC when linking for host

[Nick Desaulniers]

On Thu, Oct 5, 2023 at 2:41 PM Matthew Maurer <mmaurer@google.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@google.com>
> ---
>
> Edited to use escsq in both Makefiles, as per Masahiro Yamada's
> suggestion.

That looks better; thanks Matthew!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
>  rust/Makefile         | 2 ++
>  scripts/Makefile.host | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index 87958e864be0..2ddd821d9435 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='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
>                 --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))
>
> --
> 2.42.0.609.gbb76f46606-goog
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH v4] rust: Respect HOSTCC when linking for host

[Masahiro Yamada]

On Fri, Oct 6, 2023 at 6:41 AM Matthew Maurer <mmaurer@google.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@google.com>
> ---
>
> Edited to use escsq in both Makefiles, as per Masahiro Yamada's
> suggestion.



Acked-by: Masahiro Yamada <masahiroy@kernel.org>

if Miguel picked this up.


Please let me know if I should pick this up.





-- 
Best Regards
Masahiro Yamada

Re: [PATCH v4] rust: Respect HOSTCC when linking for host

[Miguel Ojeda]

On Sat, Oct 7, 2023 at 5:38 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
>
> if Miguel picked this up.
>
> Please let me know if I should pick this up.

Thanks a lot for taking a look Masahiro -- either way is fine for me.
If you want to take it, please feel free to add my `Acked-by`.

Cheers,
Miguel

Re: [PATCH v4] rust: Respect HOSTCC when linking for host

[Masahiro Yamada]

On Tue, Oct 10, 2023 at 7:00 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Sat, Oct 7, 2023 at 5:38 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > Acked-by: Masahiro Yamada <masahiroy@kernel.org>
> >
> > if Miguel picked this up.
> >
> > Please let me know if I should pick this up.
>
> Thanks a lot for taking a look Masahiro -- either way is fine for me.
> If you want to take it, please feel free to add my `Acked-by`.
>
> Cheers,
> Miguel

I do not see this yet in linux-next.

So, I applied to linux-kbuild with Miguel's Ack now.



-- 
Best Regards
Masahiro Yamada