linux-kernel - Re: [PATCH] kbuild: quote OBJCOPY var to avoid a pahole call break the build

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Date:   Wed, 26 May 2021 09:18:27 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH] kbuild: quote OBJCOPY var to avoid a pahole call break
 the build

On Tue, May 18, 2021 at 7:23 AM Javier Martinez Canillas
<javierm@...hat.com> wrote:
>
> The ccache tool can be used to speed up cross-compilation, by calling the
> compiler and binutils through ccache. For example, following should work:
>
>     $ export ARCH=arm64 CROSS_COMPILE="ccache aarch64-linux-gnu-"
>
>     $ make M=drivers/gpu/drm/rockchip/
>
> but pahole fails to extract the BTF info from DWARF, breaking the build:
>
>       CC [M]  drivers/gpu/drm/rockchip//rockchipdrm.mod.o
>       LD [M]  drivers/gpu/drm/rockchip//rockchipdrm.ko
>       BTF [M] drivers/gpu/drm/rockchip//rockchipdrm.ko
>     aarch64-linux-gnu-objcopy: invalid option -- 'J'
>     Usage: aarch64-linux-gnu-objcopy [option(s)] in-file [out-file]
>      Copies a binary file, possibly transforming it in the process
>     ...
>     make[1]: *** [scripts/Makefile.modpost:156: __modpost] Error 2
>     make: *** [Makefile:1866: modules] Error 2
>
> this fails because OBJCOPY is set to "ccache aarch64-linux-gnu-copy" and
> later pahole is executed with the following command line:
>
>     LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@
>
> which gets expanded to:
>
>     LLVM_OBJCOPY=ccache aarch64-linux-gnu-objcopy pahole -J ...
>
> instead of:
>
>     LLVM_OBJCOPY="ccache aarch64-linux-gnu-objcopy" pahole -J ...
>
> Fixes: 5f9ae91f7c0 ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it")
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> ---
>

LGTM. Masahiro, would you like us to take this through bpf tree or
you'll apply this to kbuild one?

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  scripts/Makefile.modfinal | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index dd87cea9fba..a7883e45529 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -59,7 +59,7 @@ quiet_cmd_ld_ko_o = LD [M]  $@
>  quiet_cmd_btf_ko = BTF [M] $@
>        cmd_btf_ko =                                                     \
>         if [ -f vmlinux ]; then                                         \
> -               LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@; \
> +               LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J --btf_base vmlinux $@; \
>         else                                                            \
>                 printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
>         fi;
> --
> 2.31.1
>