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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Sun, 8 Jan 2023 00:22:08 +0900
Message-ID: <CAK7LNARpdAywWZCLC0a78SbDA1TSMMgZU4HK5akWivM=Z5y+iA@mail.gmail.com>
Subject: Re: nm vmlinux error in arch/arm reappears after upgrade to make 4.4
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
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On Sat, Jan 7, 2023 at 4:19 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Sat, Jan 7, 2023 at 9:29 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Hi Masahiro,
> >
> > My distribution recently updated their version of make to 4.4 from 4.3,
> > after which I notice the following error from nm when building ARCH=arm
> > kernels, which I thought that this was supposed to be resolved with
> > commit 3ec8a5b33dea ("kbuild: do not export LDFLAGS_vmlinux") but the
> > tree clearly has this and it is not visible while just running clean (I
> > have to build zImage to see it):
>
>
> Presumably, this is a different issue than 3ec8a5b33dea
>


My bad.

3ec8a5b33dea unexported LDFLAGS_vmlinux


However,

5d4aeffbf709 exported LDFLAGS_vmlinux again.


> >
> >   $ git show -s --format='%h ("%s")'
> >   512dee0c00ad ("Merge tag 'x86-urgent-2023-01-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")
> >
> >   $ make --version | head -1
> >   GNU Make 4.4
> >
> >   $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- O=build defconfig zImage
> >   arm-linux-gnueabi-nm: 'arch/arm/boot/compressed/../../../../vmlinux': No such file
> >
> > vs.
> >
> >   $ make --version | head -1
> >   GNU Make 4.3
> >
> >   $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- O=build defconfig zImage
> >
> > I bisected make to see what change causes this and I landed on
> > commit 98da874c ("[SV 10593] Export variables to $(shell ...)
> > commands") [1], which certainly seems like a reasonable commit to
> > blame but I am not sure how exactly it factors in here.
> >
> > If you need any more information on reproducing this, I am happy to
> > provide it (CROSS_COMPILE is just the toolchains from kernel.org).
> >
> > [1]: https://git.savannah.gnu.org/cgit/make.git/commit/?id=98da874c43035a490cdca81331724f233a3d0c9a
> >
> > Cheers,
> > Nathan
>
>
>
> Confirmed, but I still do not understand what
> is triggering this.


I figured out the reason.

I will send a patch later.


>
> These are my findings:
>
>  - O= option is needed to reproduce it.
>
>  - allnoconfig still produces it.
>
>  - I do not see it in the incremental builds.
>    I see it again in the full build after "git clean -fdx".
>
>
>
> If I slightly cleaned the code like follows,
> this issue disappeared.
> ($(obj)/../../../../vmlinux is the same as vmlinux)
>
>
>
>
> diff --git a/arch/arm/boot/compressed/Makefile
> b/arch/arm/boot/compressed/Makefile
> index 2ef651a78fa2..726ecabcef09 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -107,7 +107,7 @@ ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg
>  asflags-y := -DZIMAGE
>
>  # Supply kernel BSS size to the decompressor via a linker symbol.
> -KBSS_SZ = $(shell echo $$(($$($(NM) $(obj)/../../../../vmlinux | \
> +KBSS_SZ = $(shell echo $$(($$($(NM) vmlinux | \
>                 sed -n -e 's/^\([^ ]*\) [ABD] __bss_start$$/-0x\1/p' \
>                        -e 's/^\([^ ]*\) [ABD] __bss_stop$$/+0x\1/p') )) )
>  LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ)
>
>
>
>
>
>
>
>
>
>
> --
> Best Regards
> Masahiro Yamada


-- 
Best Regards
Masahiro Yamada