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

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Message-ID: <20250506-accomplished-earthworm-from-valhalla-dbcbcc@l-nschier-aarch64>
Date: Tue, 6 May 2025 13:12:11 +0200
From: Nicolas Schier <nicolas.schier@...ux.dev>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: masahiroy@...nel.org, 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 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 \
>  		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:

    grep: ../include/generated/compile.h: No such file or directory
    ***
    *** The source tree is not clean, please run 'make ARCH= mrproper'
    ...

Kind regards,
Nicolas