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Date:   Fri, 16 Apr 2021 15:38:32 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     ojeda@kernel.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, linux-kbuild@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Geoffrey Thomas <geofft@ldpreload.com>,
        Finn Behrens <me@kloenk.de>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 04/13] Kbuild: Rust support
Message-ID: <YHmTWEAS/QjX++w4@hirez.programming.kicks-ass.net>
References: <20210414184604.23473-1-ojeda@kernel.org>
 <20210414184604.23473-5-ojeda@kernel.org>
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On Wed, Apr 14, 2021 at 08:45:55PM +0200, ojeda@kernel.org wrote:
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 1b6094a13034..3665c49c4dcf 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -26,6 +26,7 @@ EXTRA_CPPFLAGS :=
>  EXTRA_LDFLAGS  :=
>  asflags-y  :=
>  ccflags-y  :=
> +rustcflags-y :=
>  cppflags-y :=
>  ldflags-y  :=
>  
> @@ -287,6 +288,24 @@ quiet_cmd_cc_lst_c = MKLST   $@
>  $(obj)/%.lst: $(src)/%.c FORCE
>  	$(call if_changed_dep,cc_lst_c)
>  
> +# Compile Rust sources (.rs)
> +# ---------------------------------------------------------------------------
> +
> +rustc_cross_flags := --target=$(srctree)/arch/$(SRCARCH)/rust/target.json
> +
> +quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
> +      cmd_rustc_o_rs = \
> +	RUST_MODFILE=$(modfile) \
> +	$(RUSTC_OR_CLIPPY) $(rustc_flags) $(rustc_cross_flags) \
> +		--extern alloc --extern kernel \
> +		--crate-type rlib --out-dir $(obj) -L $(objtree)/rust/ \
> +		--crate-name $(patsubst %.o,%,$(notdir $@)) $<; \
> +	mv $(obj)/$(subst .o,,$(notdir $@)).d $(depfile); \
> +	sed -i '/^\#/d' $(depfile)
> +
> +$(obj)/%.o: $(src)/%.rs FORCE
> +	$(call if_changed_dep,rustc_o_rs)
> +
>  # Compile assembler sources (.S)
>  # ---------------------------------------------------------------------------
>  

So if I read all this right, rust compiles to .o and, like any other .o
file is then fed into objtool (for x86_64). Did you have any problems
with objtool? Does it generate correct ORC unwind information?

AFAICT rust has try/throw/catch exception handling (like
C++/Java/others) which is typically implemented with stack unwinding of
its own.

Does all that interact sanely?