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[PATCH] kbuild: host: use single executable for rustc -C linker

Mohamad Alsadhan posted 1 patch 1 month, 1 week ago
There is a newer version of this series
scripts/Makefile.host | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
[PATCH] kbuild: host: use single executable for rustc -C linker
Posted by Mohamad Alsadhan 1 month, 1 week ago 
rustc's -C linker= option expects a single executable path. When
HOSTCC contains a wrapper (e.g. "ccache gcc"), passing
-Clinker=$(HOSTCC) results in the shell splitting the value into
multiple words, and rustc interprets the additional word as an
input filename:

  error: multiple input filenames provided ...

Use the last word of HOSTCC as the linker executable for host
Rust tools. This preserves wrapper usage for C host tools while
ensuring rustc receives a single executable path.

Closes: https://github.com/Rust-for-Linux/linux/issues/1224

Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
---
 scripts/Makefile.host | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index c1dedf646..22eab2734 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -87,11 +87,18 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
                  $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
                  $(HOSTCXXFLAGS_$(target-stem).o)
 
+# rustc's `-C linker=` expects a single executable path, not a command line.
+# HOSTCC may be a multi-word command when wrapped (e.g. "ccache gcc"),
+# which would otherwise be split by the shell and mis-parsed by rustc.
+#
+# Use a dedicated variable for the linker program used by host Rust tools.
+HOSTRUSTC_LINKER ?= $(lastword $(HOSTCC))
+
 # `--out-dir` is required to avoid temporaries being created by `rustc` in the
 # 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=$(HOSTCC) \
+		 -Clinker-flavor=gcc -Clinker=$(HOSTRUSTC_LINKER) \
 		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
                  $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
                  $(HOSTRUSTFLAGS_$(target-stem))
-- 
2.52.0
Re: [PATCH] kbuild: host: use single executable for rustc -C linker
Posted by Gary Guo 1 month, 1 week ago 
On Wed Feb 25, 2026 at 10:28 AM GMT, Mohamad Alsadhan wrote:
> rustc's -C linker= option expects a single executable path. When
> HOSTCC contains a wrapper (e.g. "ccache gcc"), passing
> -Clinker=$(HOSTCC) results in the shell splitting the value into
> multiple words, and rustc interprets the additional word as an
> input filename:
>
>   error: multiple input filenames provided ...
>
> Use the last word of HOSTCC as the linker executable for host
> Rust tools. This preserves wrapper usage for C host tools while
> ensuring rustc receives a single executable path.

I don't think this is the right fix. Using only the last word is

(1) not what people asks for when they override HOSTCC. When a user ssays "call
ccache gcc", they don't want "gcc" to be invoked instead.
(2) not general enough. If instead of a wrapper, it's something with subcommand,
then this just breaks.
(3) going to cause surprises to people and be hard to troubleshoot when things
do not work.

I think the proper fix should be invoking a helper script with the multi-word
command be passed as environment variable which is then expanded by shell.

Best,
Gary

>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1224
>
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
> ---
>  scripts/Makefile.host | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646..22eab2734 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,18 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-C linker=` expects a single executable path, not a command line.
> +# HOSTCC may be a multi-word command when wrapped (e.g. "ccache gcc"),
> +# which would otherwise be split by the shell and mis-parsed by rustc.
> +#
> +# Use a dedicated variable for the linker program used by host Rust tools.
> +HOSTRUSTC_LINKER ?= $(lastword $(HOSTCC))
> +
>  # `--out-dir` is required to avoid temporaries being created by `rustc` in the
>  # 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=$(HOSTCC) \
> +		 -Clinker-flavor=gcc -Clinker=$(HOSTRUSTC_LINKER) \
>  		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
>                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
>                   $(HOSTRUSTFLAGS_$(target-stem))
Re: [PATCH] kbuild: host: use single executable for rustc -C linker
Posted by Nathan Chancellor 1 month, 1 week ago 
On Wed, Feb 25, 2026 at 01:28:19PM +0300, Mohamad Alsadhan wrote:
> rustc's -C linker= option expects a single executable path. When
> HOSTCC contains a wrapper (e.g. "ccache gcc"), passing
> -Clinker=$(HOSTCC) results in the shell splitting the value into
> multiple words, and rustc interprets the additional word as an
> input filename:
> 
>   error: multiple input filenames provided ...
> 
> Use the last word of HOSTCC as the linker executable for host
> Rust tools. This preserves wrapper usage for C host tools while
> ensuring rustc receives a single executable path.
> 
> Closes: https://github.com/Rust-for-Linux/linux/issues/1224
> 
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>

Miguel, as this is a Rust fix, do you want to take it? If so:

Acked-by: Nathan Chancellor <nathan@kernel.org>

Otherwise, I could take it via kbuild-fixes for 7.0.

> ---
>  scripts/Makefile.host | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646..22eab2734 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,18 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-C linker=` expects a single executable path, not a command line.
> +# HOSTCC may be a multi-word command when wrapped (e.g. "ccache gcc"),
> +# which would otherwise be split by the shell and mis-parsed by rustc.
> +#
> +# Use a dedicated variable for the linker program used by host Rust tools.
> +HOSTRUSTC_LINKER ?= $(lastword $(HOSTCC))

I would probably use HOSTRUSTC_LD to mirror how the rest of Kbuild
refers to the linker.

> +
>  # `--out-dir` is required to avoid temporaries being created by `rustc` in the
>  # 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=$(HOSTCC) \
> +		 -Clinker-flavor=gcc -Clinker=$(HOSTRUSTC_LINKER) \
>  		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
>                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
>                   $(HOSTRUSTFLAGS_$(target-stem))
> -- 
> 2.52.0
>

Patchew 2.1-devel-ea86937

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