linux-kernel - Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=

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Message-Id: <1116D946-05F3-4463-A61F-DE221F258A3F@linux.dev>
Date: Mon, 9 Dec 2024 14:55:44 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 cocci@...ia.fr
Subject: Re: [PATCH v2 05/11] kbuild: change working directory to external
 module directory with M=

On 9. Dec 2024, at 14:46, Thorsten Blum wrote:
> On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
>> 
>> Currently, Kbuild always operates in the output directory of the kernel,
>> even when building external modules. This increases the risk of external
>> module Makefiles attempting to write to the kernel directory.
>> 
>> This commit switches the working directory to the external module
>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
>> some build artifacts.
>> 
>> The command for building external modules maintains backward
>> compatibility, but Makefiles that rely on working in the kernel
>> directory may break. In such cases, $(objtree) and $(srctree) should
>> be used to refer to the output and source directories of the kernel.
>> 
>> The appearance of the build log will change as follows:
>> 
>> [Before]
>> 
>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>> make: Entering directory '/path/to/my/linux'
>>   CC [M]  /path/to/my/externel/module/helloworld.o
>>   MODPOST /path/to/my/externel/module/Module.symvers
>>   CC [M]  /path/to/my/externel/module/helloworld.mod.o
>>   CC [M]  /path/to/my/externel/module/.module-common.o
>>   LD [M]  /path/to/my/externel/module/helloworld.ko
>> make: Leaving directory '/path/to/my/linux'
>> 
>> [After]
>> 
>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>> make: Entering directory '/path/to/my/linux'
>> make[1]: Entering directory '/path/to/my/externel/module'
>>   CC [M]  helloworld.o
>>   MODPOST Module.symvers
>>   CC [M]  helloworld.mod.o
>>   CC [M]  .module-common.o
>>   LD [M]  helloworld.ko
>> make[1]: Leaving directory '/path/to/my/externel/module'
>> make: Leaving directory '/path/to/my/linux'
>> 
>> Printing "Entering directory" twice is cumbersome. This will be
>> addressed later.
>> 
>> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>> ---
> 
> Hi Masahiro,
> 
> I get the following error since this patch is in master, but only when
> using COCCI= in combination with M=<relative or absolute path>.
> 
> It works when I either use COCCI= or M=, but not with both.

Using the absolute path of the cocci script fixes my problem, but this
used to work with relative paths too.

$ make coccicheck COCCI=$(pwd)/scripts/coccinelle/misc/flexible_array.cocci M=arch/

Thanks,
Thorsten