Re: [PATCH v5 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Hari Bathini <hbathini@linux.ibm.com>]

On 09/10/24 8:53 pm, Masahiro Yamada wrote:
> On Mon, Sep 16, 2024 at 5:58 AM Hari Bathini <hbathini@linux.ibm.com> wrote:
>>
>> From: Naveen N Rao <naveen@kernel.org>
>>
>> On powerpc, we would like to be able to make a pass on vmlinux.o and
>> generate a new object file to be linked into vmlinux. Add a generic pass
>> in Makefile.vmlinux that architectures can use for this purpose.
>>
>> Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
>> provide arch/<arch>/tools/Makefile with .arch.vmlinux.o target, which
>> will be invoked prior to the final vmlinux link step.
>>
>> Signed-off-by: Naveen N Rao <naveen@kernel.org>
>> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
>> ---
>>
>> Changes in v5:
>> * Intermediate files named .vmlinux.arch.* instead of .arch.vmlinux.*
>>
>>
>>   arch/Kconfig             | 6 ++++++
>>   scripts/Makefile.vmlinux | 7 +++++++
>>   scripts/link-vmlinux.sh  | 7 ++++++-
>>   3 files changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/Kconfig b/arch/Kconfig
>> index 975dd22a2dbd..ef868ff8156a 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -1643,4 +1643,10 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
>>   config ARCH_NEED_CMPXCHG_1_EMU
>>          bool
>>
>> +config ARCH_WANTS_PRE_LINK_VMLINUX
>> +       def_bool n
> 
> 
> Redundant default. This line should be "bool".
> 
> 
> 
> 
> 
> 
>> +       help
>> +         An architecture can select this if it provides arch/<arch>/tools/Makefile
>> +         with .arch.vmlinux.o target to be linked into vmlinux.
>> +
>>   endmenu
>> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
>> index 49946cb96844..edf6fae8d960 100644
>> --- a/scripts/Makefile.vmlinux
>> +++ b/scripts/Makefile.vmlinux
>> @@ -22,6 +22,13 @@ targets += .vmlinux.export.o
>>   vmlinux: .vmlinux.export.o
>>   endif
>>
>> +ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
>> +vmlinux: arch/$(SRCARCH)/tools/.vmlinux.arch.o
> 
> If you move this to arch/*/tools/, there is no reason
> to make it a hidden file.

Thanks for reviewing and the detailed comments, Masahiro.

> 
> 
> vmlinux: arch/$(SRCARCH)/tools/vmlinux.arch.o
> 
> 
> 
> 
>> +arch/$(SRCARCH)/tools/.vmlinux.arch.o: vmlinux.o
> 
> FORCE is missing.


I dropped FORCE as it was rebuilding vmlinux on every invocation
of `make` irrespective of whether vmlinux.o changed or not..
Just curious if the changes you suggested makes FORCE necessary
or FORCE was expected even without the other changes you suggested?

Thanks
Hari