[PATCH v3] kbuild: host: use single executable for rustc -C linker

[PATCH v3] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

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 ...

Generate a small wrapper script and pass it to -Clinker e.g.
```
\#!/bin/sh
exec sh -c 'exec "$0" "$@"' ccache gcc "$@"
```

This fix should be general enough to address most if not all cases
(incl. wrappers or subcommands) and avoids surprises of simpler fixes
like just defaulting to gcc.

This avoids passing the user command as an environment variable as
that would be more challenging to trace and debug shell expansions.

Link: https://github.com/Rust-for-Linux/linux/issues/1224
Suggested-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
---
v2 -> v3:
  - Scrap previous hacky approaches (e.g. using lastword) and go with
    a proper fix which turned out not that complex to implement.
    Apologies Gary, I should have listened to you earlier :/

v1 -> v2:
  - Rename HOSTRUSTC_LINKER to HOSTRUSTC_LD for consistency
  - Introduce explicit HOSTRUSTC_LD override
  - Warn when falling back due to multi-argument HOSTCC
  - Error out if a user-specified HOSTRUSTC_LD is not an executable

v1: https://lore.kernel.org/all/20260225102819.16553-1-mo@sdhn.cc/
v2: https://lore.kernel.org/all/20260227132713.23106-1-mo@sdhn.cc/
---
 scripts/Makefile.host | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index c1dedf646..f976a07b7 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -87,11 +87,28 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
                  $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
                  $(HOSTCXXFLAGS_$(target-stem).o)
 
+# rustc's `-Clinker=` 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.
+# To work around this, we generate a wrapper script that forwards arguments to
+# `HOSTRUSTC_LD` so that such commands can be used safely.
+#
+# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC` 
+HOSTRUSTC_LD ?= $(HOSTCC)
+quiet_cmd_rustc-wrapper = HOSTGEN $@
+      cmd_rustc-wrapper = \
+	echo '\#!/bin/sh' > $@; \
+	echo 'exec sh -c '\''exec "$$0" "$$@"'\'' $(HOSTRUSTC_LD) "$$@"' >> $@; \
+	chmod +x $@
+
+$(obj)/rustc-wrapper: FORCE
+	$(call if_changed,rustc-wrapper)
+
 # `--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=$(HOSTCC) \
+		 -Clinker-flavor=gcc -Clinker=$(obj)/rustc-wrapper \
 		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
                  $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
                  $(HOSTRUSTFLAGS_$(target-stem))
@@ -153,7 +170,7 @@ $(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
 quiet_cmd_host-rust	= HOSTRUSTC $@
       cmd_host-rust	= \
 	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
-$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+$(host-rust): $(obj)/%: $(src)/%.rs $(obj)/rustc-wrapper FORCE
 	+$(call if_changed_dep,host-rust)
 
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
-- 
2.52.0

Re: [PATCH v3] kbuild: host: use single executable for rustc -C linker

[Nicolas Schier]

On Thu, 12 Mar 2026 03:28:52 +0300, Mohamad Alsadhan <mo@sdhn.cc> 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 ...
> 
> Generate a small wrapper script and pass it to -Clinker e.g.
> ```
> \#!/bin/sh

('\' is just a copy-and-paste left-over)

> exec sh -c 'exec "$0" "$@"' ccache gcc "$@"
> ```
> 
> This fix should be general enough to address most if not all cases
> (incl. wrappers or subcommands) and avoids surprises of simpler fixes
> like just defaulting to gcc.
> 
> This avoids passing the user command as an environment variable as
> that would be more challenging to trace and debug shell expansions.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1224
> Suggested-by: Yoann Congal <yoann.congal@smile.fr>
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
> 
> ---

thanks for v3 with the wrapper script; it looks cleaner to me.  Some
comments below.

>  scripts/Makefile.host | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646a39..f976a07b7b09 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,28 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-Clinker=` 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.
> +# To work around this, we generate a wrapper script that forwards arguments to
> +# `HOSTRUSTC_LD` so that such commands can be used safely.
> +#
> +# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC` 

(trailing space at EOL)

> +HOSTRUSTC_LD ?= $(HOSTCC)
> +quiet_cmd_rustc-wrapper = HOSTGEN $@
> +      cmd_rustc-wrapper = \
> +	echo '\#!/bin/sh' > $@; \
> +	echo 'exec sh -c '\''exec "$$0" "$$@"'\'' $(HOSTRUSTC_LD) "$$@"' >> $@; \

Why can't we just use this?

    echo 'exec $(HOSTRUSTC_LD) "$$@"' >> $@; \


> +	chmod +x $@
> +
> +$(obj)/rustc-wrapper: FORCE
> +	$(call if_changed,rustc-wrapper)

The if_changed macro is not optimal here, as there are no real prerequisites
for the $(obj)/rustc-wrapper rule but only FORCE, cp.
Documentation/kbuild/makefiles.rst ("Command change detection").  Thus, the
rustc-wrapper will always be rebuilt and so always show the 'HOSTGEN' line.

But you could use filechk instead, e.g.:

define filechk_rustc-wrapper
	printf "%s\n" \
		'#!/bin/sh' \
		'exec sh -c '\''exec "$$0" "$$@"'\'' $(HOSTRUSTC_LD) "$$@"'
endef

$(obj)/rustc-wrapper: FORCE
	$(call filechk,rustc-wrapper)
	$(Q)chmod +x $@


Kind regards

-- 
Nicolas

Re: [PATCH v3] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

On 26/03/12 02:50pm, Nicolas Schier wrote:
> 
> Why can't we just use this?
> 
>     echo 'exec $(HOSTRUSTC_LD) "$$@"' >> $@; \
> 
> 

I was being extra safe with quoting and escaping to make this as
general as it can be. Just in case a more complex command with some 
shell quoting is passed e.g.
    `HOSTRUSTC_LD="env 'CCACHE_DIR=/tmp/my cache' ccache gcc"`

`sh -c` would reparse it with original quoting and avoid potential 
issues. If you think it's unnecessary, I can change it to the simpler 
version.

> 
> The if_changed macro is not optimal here, as there are no real prerequisites
> for the $(obj)/rustc-wrapper rule but only FORCE, cp.
> Documentation/kbuild/makefiles.rst ("Command change detection").  Thus, the
> rustc-wrapper will always be rebuilt and so always show the 'HOSTGEN' line.
> 
> But you could use filechk instead, e.g.:

Noted, I will update this in v4 to use filechk instead.

Thanks for the helpful comments and suggestions,
Mo

[PATCH v4] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

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 ...

Generate a small wrapper script and pass it to -Clinker e.g.
```
exec sh -c 'exec "$0" "$@"' ccache gcc "$@"
```

This fix should be general enough to address most if not all cases
(incl. wrappers or subcommands) and avoids surprises of simpler fixes
like just defaulting to gcc.

This avoids passing the user command as an environment variable as
that would be more challenging to trace and debug shell expansions.

Link: https://github.com/Rust-for-Linux/linux/issues/1224
Suggested-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
---
v3 -> v4:
  - Use filechk instead of if_changed macro to regenerate script
  - Remove trailing space at EOL

v2 -> v3:
  - Scrap previous hacky approaches (e.g. using lastword) and go with
    a proper fix which turned out not that complex to implement.
    Apologies Gary, I should have listened to you earlier :/

v1 -> v2:
  - Rename HOSTRUSTC_LINKER to HOSTRUSTC_LD for consistency
  - Introduce explicit HOSTRUSTC_LD override
  - Warn when falling back due to multi-argument HOSTCC
  - Error out if a user-specified HOSTRUSTC_LD is not an executable

v1: https://lore.kernel.org/all/20260225102819.16553-1-mo@sdhn.cc/
v2: https://lore.kernel.org/all/20260227132713.23106-1-mo@sdhn.cc/
v3: https://lore.kernel.org/all/20260312002852.11292-1-mo@sdhn.cc/
---
 scripts/Makefile.host | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index c1dedf646..e41753828 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -87,11 +87,29 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
                  $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
                  $(HOSTCXXFLAGS_$(target-stem).o)
 
+# rustc's `-Clinker=` 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.
+# To work around this, we generate a wrapper script that forwards arguments to
+# `HOSTRUSTC_LD` so that such commands can be used safely.
+#
+# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC`
+HOSTRUSTC_LD ?= $(HOSTCC)
+define filechk_rustc-wrapper
+	printf "%s\n" \
+		'#!/bin/sh' \
+		'exec sh -c '\''exec "$$0" "$$@"'\'' $(HOSTRUSTC_LD) "$$@"'
+endef
+
+$(obj)/rustc-wrapper: FORCE
+	$(call filechk,rustc-wrapper)
+	$(Q)chmod +x $@
+
 # `--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=$(HOSTCC) \
+		 -Clinker-flavor=gcc -Clinker=$(obj)/rustc-wrapper \
 		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
                  $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
                  $(HOSTRUSTFLAGS_$(target-stem))
@@ -153,7 +171,7 @@ $(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
 quiet_cmd_host-rust	= HOSTRUSTC $@
       cmd_host-rust	= \
 	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
-$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+$(host-rust): $(obj)/%: $(src)/%.rs $(obj)/rustc-wrapper FORCE
 	+$(call if_changed_dep,host-rust)
 
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
-- 
2.52.0

Re: [PATCH v3] kbuild: host: use single executable for rustc -C linker

[Nicolas Schier]

On Tue, Mar 17, 2026 at 02:10:27PM +0300, Mohamad Alsadhan wrote:
> On 26/03/12 02:50pm, Nicolas Schier wrote:
> > 
> > Why can't we just use this?
> > 
> >     echo 'exec $(HOSTRUSTC_LD) "$$@"' >> $@; \
> > 
> > 
> 
> I was being extra safe with quoting and escaping to make this as
> general as it can be. Just in case a more complex command with some 
> shell quoting is passed e.g.
>     `HOSTRUSTC_LD="env 'CCACHE_DIR=/tmp/my cache' ccache gcc"`

This does not work with the 'printf' variant (v4) either, as the space in
'my cache' will split the printf arguments and results in:

#!/bin/sh
exec sh -c 'exec "$0" "$@"' "env CCACHE_DIR=/tmp/my
cache ccache gcc" "$@"

Sorry, I frequently forget to handle spaces in subdir names correctly.
I'll send another suggestion as reply to v4.


-- 
Nicolas

Re: [PATCH v4] kbuild: host: use single executable for rustc -C linker

[Nicolas Schier]

On Tue, Mar 17, 2026 at 02:20:21PM +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 ...
> 
> Generate a small wrapper script and pass it to -Clinker e.g.
> ```
> exec sh -c 'exec "$0" "$@"' ccache gcc "$@"
> ```
> 
> This fix should be general enough to address most if not all cases
> (incl. wrappers or subcommands) and avoids surprises of simpler fixes
> like just defaulting to gcc.
> 
> This avoids passing the user command as an environment variable as
> that would be more challenging to trace and debug shell expansions.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1224
> Suggested-by: Yoann Congal <yoann.congal@smile.fr>
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
> ---
> v3 -> v4:
>   - Use filechk instead of if_changed macro to regenerate script
>   - Remove trailing space at EOL
> 
> v2 -> v3:
>   - Scrap previous hacky approaches (e.g. using lastword) and go with
>     a proper fix which turned out not that complex to implement.
>     Apologies Gary, I should have listened to you earlier :/
> 
> v1 -> v2:
>   - Rename HOSTRUSTC_LINKER to HOSTRUSTC_LD for consistency
>   - Introduce explicit HOSTRUSTC_LD override
>   - Warn when falling back due to multi-argument HOSTCC
>   - Error out if a user-specified HOSTRUSTC_LD is not an executable
> 
> v1: https://lore.kernel.org/all/20260225102819.16553-1-mo@sdhn.cc/
> v2: https://lore.kernel.org/all/20260227132713.23106-1-mo@sdhn.cc/
> v3: https://lore.kernel.org/all/20260312002852.11292-1-mo@sdhn.cc/
> ---
>  scripts/Makefile.host | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646..e41753828 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,29 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-Clinker=` 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.
> +# To work around this, we generate a wrapper script that forwards arguments to
> +# `HOSTRUSTC_LD` so that such commands can be used safely.
> +#
> +# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC`
> +HOSTRUSTC_LD ?= $(HOSTCC)
> +define filechk_rustc-wrapper
> +	printf "%s\n" \
> +		'#!/bin/sh' \
> +		'exec sh -c '\''exec "$$0" "$$@"'\'' $(HOSTRUSTC_LD) "$$@"'
> +endef

This printf-based solution needs some more tweaking to also support
complex commands in HOSTRUSTC_LD with quoted spaces.  A straight forward
way could be:

	'exec sh -c '\''exec "$$0" "$$@"'\'' $(call escsq,$(HOSTRUSTC_LD)) "$$@"'

to escape single quotes within HOSTRUSTC_LD.  Then the complex example
from v3 works again (make HOSTRUSTC_LD="env 'CCACHE_DIR=/tmp/my cache' ccache gcc").

With the quoting fixed:
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>



I am still not seeing a benefit in calling usage of 'exec' and 'sh -c'.
If we'd skip both, there would be no need to use 'env' for environment
updates:

	'$(call escsq,$(HOSTRUSTC_LD)) "$$@"'

But I may be missing something here.

Kind regards,
Nicolas

Re: [PATCH v4] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

On 26/03/20 07:51am, Nicolas Schier wrote:
> 
> This printf-based solution needs some more tweaking to also support
> complex commands in HOSTRUSTC_LD with quoted spaces.  A straight forward
> way could be:
> 
> 	'exec sh -c '\''exec "$$0" "$$@"'\'' $(call escsq,$(HOSTRUSTC_LD)) "$$@"'
> 
> to escape single quotes within HOSTRUSTC_LD.  Then the complex example
> from v3 works again (make HOSTRUSTC_LD="env 'CCACHE_DIR=/tmp/my cache' ccache gcc").
Thanks for pointing it out, I should've retested more thoroughly.

> I am still not seeing a benefit in calling usage of 'exec' and 'sh -c'.
> If we'd skip both, there would be no need to use 'env' for environment
> updates:
> 
> 	'$(call escsq,$(HOSTRUSTC_LD)) "$$@"'
> 
> But I may be missing something here.
I was trying to make it as general as possible, e.g. for commands with
shell magic, but I honestly can't make up a plausible use case for
that. We can just go with the simple solution as it also doesn't need
`env`.

I'll send the v5 patch with fix for quoted spaces and the simpler
command.

Best regards,
Mo

[PATCH v5] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

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 ...

Generate a small wrapper script and pass it to -Clinker e.g.

  ```
  #!/bin/sh
  ccache gcc "$@"
  ```

This fix should be general enough to address most if not all cases
(incl. wrappers or subcommands) and avoids surprises of simpler fixes
like just defaulting to gcc.

This avoids passing the user command as an environment variable as
that would be more challenging to trace and debug shell expansions.

Link: https://github.com/Rust-for-Linux/linux/issues/1224
Suggested-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
---
v4 -> v5:
  - Fix word splitting issues
  - Remove unnecessary `exec sh -c` and simplify generated script

v3 -> v4:
  - Use filechk instead of if_changed macro to regenerate script
  - Remove trailing space at EOL

v2 -> v3:
  - Scrap previous hacky approaches (e.g. using lastword) and go with
    a proper fix which turned out not that complex to implement.
    Apologies Gary, I should have listened to you earlier :/

v1 -> v2:
  - Rename HOSTRUSTC_LINKER to HOSTRUSTC_LD for consistency
  - Introduce explicit HOSTRUSTC_LD override
  - Warn when falling back due to multi-argument HOSTCC
  - Error out if a user-specified HOSTRUSTC_LD is not an executable

v1: https://lore.kernel.org/all/20260225102819.16553-1-mo@sdhn.cc/
v2: https://lore.kernel.org/all/20260227132713.23106-1-mo@sdhn.cc/
v3: https://lore.kernel.org/all/20260312002852.11292-1-mo@sdhn.cc/
v4: https://lore.kernel.org/all/20260317112021.14353-1-mo@sdhn.cc/
---
 scripts/Makefile.host | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index c1dedf646..2d2429ca0 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -87,11 +87,29 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
                  $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
                  $(HOSTCXXFLAGS_$(target-stem).o)
 
+# rustc's `-Clinker=` 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.
+# To work around this, we generate a wrapper script that forwards arguments to
+# `HOSTRUSTC_LD` so that such commands can be used safely.
+#
+# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC`
+HOSTRUSTC_LD ?= $(HOSTCC)
+define filechk_rustc-wrapper
+	printf "%s\n" \
+		'#!/bin/sh' \
+		'$(call escsq,$(HOSTRUSTC_LD)) "$$@"'
+endef
+
+$(obj)/rustc-wrapper: FORCE
+	$(call filechk,rustc-wrapper)
+	$(Q)chmod +x $@
+
 # `--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=$(HOSTCC) \
+		 -Clinker-flavor=gcc -Clinker=$(obj)/rustc-wrapper \
 		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
                  $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
                  $(HOSTRUSTFLAGS_$(target-stem))
@@ -153,7 +171,7 @@ $(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
 quiet_cmd_host-rust	= HOSTRUSTC $@
       cmd_host-rust	= \
 	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
-$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+$(host-rust): $(obj)/%: $(src)/%.rs $(obj)/rustc-wrapper FORCE
 	+$(call if_changed_dep,host-rust)
 
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
-- 
2.52.0

Re: [PATCH v5] kbuild: host: use single executable for rustc -C linker

[Nicolas Schier]

Hi Mohamad,

On Sat, Mar 21, 2026 at 06:00:34PM +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=$(HOSTCC)` results in the shell splitting the value into
> multiple words, and rustc interprets the additional word as an
> input filename:
> 
>   error: multiple input filenames provided ...
> 
> Generate a small wrapper script and pass it to -Clinker e.g.
> 
>   ```
>   #!/bin/sh
>   ccache gcc "$@"
>   ```
> 
> This fix should be general enough to address most if not all cases
> (incl. wrappers or subcommands) and avoids surprises of simpler fixes
> like just defaulting to gcc.
> 
> This avoids passing the user command as an environment variable as
> that would be more challenging to trace and debug shell expansions.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1224
> Suggested-by: Yoann Congal <yoann.congal@smile.fr>
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
> ---

Thanks!

Reviewed-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>

Unfortunately, I overlooked the missing entries for 'clean'/'mrproper'
and scripts/.gitignore.  Is it ok for you if I the following diff to
your patch?


diff --git a/Makefile b/Makefile
index a8d8ed711f9b..69fa18565219 100644
--- a/Makefile
+++ b/Makefile
@@ -1676,7 +1676,8 @@ MRPROPER_FILES += include/config include/generated          \
 		  vmlinux-gdb.py \
 		  rpmbuild \
 		  rust/libmacros.so rust/libmacros.dylib \
-		  rust/libpin_init_internal.so rust/libpin_init_internal.dylib
+		  rust/libpin_init_internal.so rust/libpin_init_internal.dylib \
+		  scripts/rustc-wrapper
 
 # clean - Delete most, but leave enough to build external modules
 #
diff --git a/scripts/.gitignore b/scripts/.gitignore
index 4215c2208f7e..b3948b148c4b 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -6,6 +6,7 @@
 /kallsyms
 /module.lds
 /recordmcount
+/rustc-wrapper
 /rustdoc_test_builder
 /rustdoc_test_gen
 /sign-file


Kind regards,
Nicolas

Re: [PATCH v5] kbuild: host: use single executable for rustc -C linker

[Yoann Congal]

On Sat Mar 21, 2026 at 4:00 PM CET, Mohamad Alsadhan wrote:
> rustc's -C linker= option expects a single executable path. When
> HOSTCC contains a wrapper (e.g. "ccache gcc"), passing
> `-Clinker=$(HOSTCC)` results in the shell splitting the value into
> multiple words, and rustc interprets the additional word as an
> input filename:
>
>   error: multiple input filenames provided ...
>
> Generate a small wrapper script and pass it to -Clinker e.g.
>
>   ```
>   #!/bin/sh
>   ccache gcc "$@"
>   ```
>
> This fix should be general enough to address most if not all cases
> (incl. wrappers or subcommands) and avoids surprises of simpler fixes
> like just defaulting to gcc.
>
> This avoids passing the user command as an environment variable as
> that would be more challenging to trace and debug shell expansions.
>
> Link: https://github.com/Rust-for-Linux/linux/issues/1224
> Suggested-by: Yoann Congal <yoann.congal@smile.fr>
> Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>

Hello,

First, thank you for working on this. This is appreciated :-)

> ---
> v4 -> v5:
>   - Fix word splitting issues
>   - Remove unnecessary `exec sh -c` and simplify generated script
>
> v3 -> v4:
>   - Use filechk instead of if_changed macro to regenerate script
>   - Remove trailing space at EOL
>
> v2 -> v3:
>   - Scrap previous hacky approaches (e.g. using lastword) and go with
>     a proper fix which turned out not that complex to implement.
>     Apologies Gary, I should have listened to you earlier :/
>
> v1 -> v2:
>   - Rename HOSTRUSTC_LINKER to HOSTRUSTC_LD for consistency
>   - Introduce explicit HOSTRUSTC_LD override
>   - Warn when falling back due to multi-argument HOSTCC
>   - Error out if a user-specified HOSTRUSTC_LD is not an executable
>
> v1: https://lore.kernel.org/all/20260225102819.16553-1-mo@sdhn.cc/
> v2: https://lore.kernel.org/all/20260227132713.23106-1-mo@sdhn.cc/
> v3: https://lore.kernel.org/all/20260312002852.11292-1-mo@sdhn.cc/
> v4: https://lore.kernel.org/all/20260317112021.14353-1-mo@sdhn.cc/
> ---
>  scripts/Makefile.host | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646..2d2429ca0 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,29 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-Clinker=` 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.
> +# To work around this, we generate a wrapper script that forwards arguments to
> +# `HOSTRUSTC_LD` so that such commands can be used safely.
> +#
> +# Set `HOSTRUSTC_LD` for a different rustc linker command than `HOSTCC`
> +HOSTRUSTC_LD ?= $(HOSTCC)
> +define filechk_rustc-wrapper
> +	printf "%s\n" \
> +		'#!/bin/sh' \
> +		'$(call escsq,$(HOSTRUSTC_LD)) "$$@"'
> +endef
> +
> +$(obj)/rustc-wrapper: FORCE
> +	$(call filechk,rustc-wrapper)
> +	$(Q)chmod +x $@
> +
>  # `--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=$(HOSTCC) \
> +		 -Clinker-flavor=gcc -Clinker=$(obj)/rustc-wrapper \

Shouldn't this fix be also applied to rust/Makefile?
It also contains a "-Clinker=$(HOSTCC)" argument for rustc[0].

With something like the following (On a 6.18.19), it does compile:
diff --git a/rust/Makefile b/rust/Makefile
index d4618f646b05..516fc1ea872d 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -422,7 +422,7 @@ $(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) $(rustc_target_flags) \
-		-Clinker-flavor=gcc -Clinker=$(HOSTCC) \
+		-Clinker-flavor=gcc -Clinker=scripts/rustc-wrapper \
 		-Clink-args='$(call escsq,$(KBUILD_PROCMACROLDFLAGS))' \
 		--emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \
 		--crate-type proc-macro \

Note that I did not use the same patch: scripts/rustc-wrapper instead of
$(obj)/rustc-wrapper.
$(obj)/rustc-wrapper did not work (the wrapper was searched in rust/ and
not found) when I tried it.

[0]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/rust/Makefile#n553

Regards,

>  		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
>                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
>                   $(HOSTRUSTFLAGS_$(target-stem))
> @@ -153,7 +171,7 @@ $(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
>  quiet_cmd_host-rust	= HOSTRUSTC $@
>        cmd_host-rust	= \
>  	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
> -$(host-rust): $(obj)/%: $(src)/%.rs FORCE
> +$(host-rust): $(obj)/%: $(src)/%.rs $(obj)/rustc-wrapper FORCE
>  	+$(call if_changed_dep,host-rust)
>  
>  targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \


-- 
Yoann Congal
Smile ECS

Re: [PATCH v5] kbuild: host: use single executable for rustc -C linker

[Mohamad Alsadhan]

Hello Nicolas,

On 26/03/25 09:45am, Nicolas Schier wrote:
> Unfortunately, I overlooked the missing entries for 'clean'/'mrproper'
> and scripts/.gitignore.  Is it ok for you if I the following diff to
> your patch?

Please go ahead, I missed those as well. Thanks for catching that!

I also missed another instance where the linker is passed to `RUSTC`,
in `rust/Makefile`, as Yoann pointed out. So it's worth considering
adding the fix in there too.

Happy to send an updated patch with the missing bits if you'd prefer,
but I'm also fine with you folding it in.

Best,
Mo