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

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Date:   Thu, 27 May 2021 04:53:04 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...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 Thu, May 27, 2021 at 1:18 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> 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-"

Actually, I did not know this...

> >
> >     $ 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
> >


Please feel free to pick it up.
I do not know 5f9ae91f7c0.

BTW, I see similar code in scripts/link-vmlinux.sh too.

     LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${extra_paholeopt} ${1}

Is it OK to leave it unquoted?


-- 
Best Regards
Masahiro Yamada