Re: [PATCH] kbuild: rust: avoid creating temporary files

[Nathan Chancellor]

On Tue, Jul 18, 2023 at 07:52:35AM +0200, Miguel Ojeda wrote:
> `rustc` outputs by default the temporary files (i.e. the ones saved
> by `-Csave-temps`, such as `*.rcgu*` files) in the current working
> directory when `-o` and `--out-dir` are not given (even if
> `--emit=x=path` is given, i.e. it does not use those for temporaries).
> 
> Since out-of-tree modules are compiled from the `linux` tree,
> `rustc` then tries to create them there, which may not be accessible.
> 
> Thus pass `--out-dir` explicitly, even if it is just for the temporary
> files.
> 
> Reported-by: Raphael Nestler <raphael.nestler@xxxxxxxxx>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1015
> Reported-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
> Tested-by: Raphael Nestler <raphael.nestler@xxxxxxxxx>
> Tested-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>

Seems reasonable to me.

Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>

> ---
>  scripts/Makefile.build | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 6413342a03f4..82e3fb19fdaf 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -264,6 +264,9 @@ $(obj)/%.lst: $(src)/%.c FORCE
>  
>  rust_allowed_features := new_uninit
>  
> +# `--out-dir` is required to avoid temporaries being created by `rustc` in the
> +# current working directory, which may be not accessible in the out-of-tree
> +# modules case.
>  rust_common_cmd = \
>  	RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
>  	-Zallow-features=$(rust_allowed_features) \
> @@ -272,7 +275,7 @@ rust_common_cmd = \
>  	--extern alloc --extern kernel \
>  	--crate-type rlib -L $(objtree)/rust/ \
>  	--crate-name $(basename $(notdir $@)) \
> -	--emit=dep-info=$(depfile)
> +	--out-dir $(dir $@) --emit=dep-info=$(depfile)
>  
>  # `--emit=obj`, `--emit=asm` and `--emit=llvm-ir` imply a single codegen unit
>  # will be used. We explicitly request `-Ccodegen-units=1` in any case, and
> 
> base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
> -- 
> 2.41.0
>