linux-kernel - Re: [PATCH] kbuild: use ARCH from compile.h in unclean source tree msg

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Message-ID: <CAK7LNATTE62vNgW5bMhh8rA3=eDO5WoGGvt0N0AkNn3DFGR4bA@mail.gmail.com>
Date: Wed, 7 May 2025 16:23:01 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: Nicolas Schier <nicolas.schier@...ux.dev>, nathan@...nel.org, brendan.higgins@...ux.dev, 
	davidgow@...gle.com, rmoar@...gle.com, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kunit-dev@...glegroups.com, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] kbuild: use ARCH from compile.h in unclean source tree msg

On Wed, May 7, 2025 at 7:07 AM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 5/6/25 05:12, Nicolas Schier wrote:
> > On Fri, 02 May 2025, Shuah Khan wrote:
> >
> >> When make finds the source tree unclean, it prints a message to run
> >> "make ARCH=x86_64 mrproper" message using the ARCH from the command
> >> line. The ARCH specified in the command line could be different from
> >> the ARCH of the existing build in the source tree.
> >>
> >> This could cause problems in regular kernel build and kunit workflows.
> >>
> >> Regular workflow:
> >>
> >> - Build x86_64 kernel
> >>      $ make ARCH=x86_64
> >> - Try building another arch kernel out of tree with O=
> >>      $ make ARCH=um O=/linux/build
> >> - kbuild detects source tree is unclean
> >>
> >>    ***
> >>    *** The source tree is not clean, please run 'make ARCH=um mrproper'
> >>    *** in /linux/linux_srcdir
> >>    ***
> >>
> >> - Clean source tree as suggested by kbuild
> >>      $ make ARCH=um mrproper
> >> - Source clean appears to be clean, but it leaves behind generated header
> >>    files under arch/x86
> >>      arch/x86/realmode/rm/pasyms.h
> >>
> >> A subsequent x86_64e build fails with
> >>    "undefined symbol sev_es_trampoline_start referenced ..."
> >>
> >> kunit workflow runs into this issue:
> >>
> >> - Build x86_64 kernel
> >> - Run kunit tests:  it tries to build for user specified ARCH or uml
> >>    as default:
> >>      $ ./tools/testing/kunit/kunit.py run
> >>
> >> - kbuild detects unclean source tree
> >>
> >>    ***
> >>    *** The source tree is not clean, please run 'make ARCH=um mrproper'
> >>    *** in /linux/linux_6.15
> >>    ***
> >>
> >> - Clean source tree as suggested by kbuild
> >>      $ make ARCH=um mrproper
> >> - Source clean appears to be clean, but it leaves behind generated header
> >>    files under arch/x86
> >>
> >> The problem shows when user tries to run tests on ARCH=x86_64:
> >>
> >>      $ ./tools/testing/kunit/kunit.py run ARCH=x86_64
> >>
> >>      "undefined symbol sev_es_trampoline_start referenced ..."
> >>
> >> Build trips on arch/x86/realmode/rm/pasyms.h left behind by a prior
> >> x86_64 build.
> >>
> >> Problems related to partially cleaned source tree are hard to debug.
> >> Change Makefile to unclean source logic to use ARCH from compile.h
> >> UTS_MACHINE string. With this change kbuild prints:
> >>
> >>      $ ./tools/testing/kunit/kunit.py run
> >>
> >>    ***
> >>    *** The source tree is not clean, please run 'make ARCH=x86_64 mrproper'
> >>    *** in /linux/linux_6.15
> >>    ***
> >>
> >> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> >> ---
> >>   Makefile | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/Makefile b/Makefile
> >> index 5aa9ee52a765..7ee29136b4da 100644
> >> --- a/Makefile
> >> +++ b/Makefile
> >> @@ -674,7 +674,7 @@ ifeq ($(KBUILD_EXTMOD),)
> >>               -d $(srctree)/include/config -o \
> >>               -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
>
> Would it make sense to check for include/generated as a catch all?
>
> >>              echo >&2 "***"; \
> >> -            echo >&2 "*** The source tree is not clean, please run 'make$(if $(findstring command line, $(origin ARCH)), ARCH=$(ARCH)) mrproper'"; \
> >> +            echo >&2 "*** The source tree is not clean, please run 'make ARCH=$(shell grep UTS_MACHINE $(srctree)/include/generated/compile.h | cut -d '"' -f 2) mrproper'"; \
> >
> > Please 'grep' option '-s'.
> >
> > There are some (rare) occassions, when there is no include/generated/compile.h
> > but still the source tree will be considered to be dirty:
>
> I considered adding a check for not finding include/generated/compile.h
> and figured if include/config is found we are probably safe.
>
> I will fix that.


I do not think this patch makes sense.

Kbuild correctly detects that "the source tree is not clean enough
to build with ARCH=um", and displays the following message:
  ***
  *** The source tree is not clean, please run 'make ARCH=um mrproper'
  *** in /linux/linux_srcdir
  ***

This is absolutely correct.


The real issue is that "make ARCH=um mrproper"
does not properly clean the source tree.



-- 
Best Regards
Masahiro Yamada