linux-kernel - Re: [PATCH v6 3/4] MIPS: vmlinuz: Use generic ashldi3

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Date:   Wed, 18 Apr 2018 10:52:23 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     James Hogan <jhogan@...nel.org>
Cc:     Matt Redfearn <matt.redfearn@...s.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Antony Pavlov <antonynpavlov@...il.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v6 3/4] MIPS: vmlinuz: Use generic ashldi3

2018-04-18 8:09 GMT+09:00 James Hogan <jhogan@...nel.org>:
> On Wed, Apr 11, 2018 at 08:50:18AM +0100, Matt Redfearn wrote:
>> diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
>> index adce180f3ee4..e03f522c33ac 100644
>> --- a/arch/mips/boot/compressed/Makefile
>> +++ b/arch/mips/boot/compressed/Makefile
>> @@ -46,9 +46,12 @@ $(obj)/uart-ath79.c: $(srctree)/arch/mips/ath79/early_printk.c
>>
>>  vmlinuzobjs-$(CONFIG_KERNEL_XZ) += $(obj)/ashldi3.o $(obj)/bswapsi.o
>>
>> -extra-y += ashldi3.c bswapsi.c
>> -$(obj)/ashldi3.o $(obj)/bswapsi.o: KBUILD_CFLAGS += -I$(srctree)/arch/mips/lib
>> -$(obj)/ashldi3.c $(obj)/bswapsi.c: $(obj)/%.c: $(srctree)/arch/mips/lib/%.c
>> +extra-y += ashldi3.c
>> +$(obj)/ashldi3.c: $(obj)/%.c: $(srctree)/lib/%.c
>> +     $(call cmd,shipped)
>> +
>> +extra-y += bswapsi.c
>> +$(obj)/bswapsi.c: $(obj)/%.c: $(srctree)/arch/mips/lib/%.c
>>       $(call cmd,shipped)
>
> ci20_defconfig:
>
> arch/mips/boot/compressed/ashldi3.c:4:10: fatal error: libgcc.h: No such file or directory
>  #include "libgcc.h"
>            ^~~~~~~~~~
>
> It looks like it had already copied ashldi3.c from arch/mips/lib/ when
> building an older commit, and it hasn't been regenerated from lib/ since
> the Makefile changed, so its still using the old version.
>
> I think it should be using FORCE and if_changed like this:
>
> diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
> index e03f522c33ac..abe77add8789 100644
> --- a/arch/mips/boot/compressed/Makefile
> +++ b/arch/mips/boot/compressed/Makefile
> @@ -47,12 +47,12 @@ $(obj)/uart-ath79.c: $(srctree)/arch/mips/ath79/early_printk.c
>  vmlinuzobjs-$(CONFIG_KERNEL_XZ) += $(obj)/ashldi3.o $(obj)/bswapsi.o
>
>  extra-y += ashldi3.c
> -$(obj)/ashldi3.c: $(obj)/%.c: $(srctree)/lib/%.c
> -       $(call cmd,shipped)
> +$(obj)/ashldi3.c: $(obj)/%.c: $(srctree)/lib/%.c FORCE
> +       $(call if_changed,shipped)
>
>  extra-y += bswapsi.c
> -$(obj)/bswapsi.c: $(obj)/%.c: $(srctree)/arch/mips/lib/%.c
> -       $(call cmd,shipped)
> +$(obj)/bswapsi.c: $(obj)/%.c: $(srctree)/arch/mips/lib/%.c FORCE
> +       $(call if_changed,shipped)
>
>  targets := $(notdir $(vmlinuzobjs-y))
>
> That resolves the build failures when checking out old -> new without
> cleaning, since the .ashldi3.c.cmd is missing so it gets rebuilt.
>
> It should also resolve issues if the path it copies from is updated in
> future since the .ashldi3.c.cmd will get updated.
>
> If you checkout new -> old without cleaning, the now removed
> arch/mips/lib/ashldi3.c will get added which will trigger regeneration,
> so it won't error.
>
> However if you do new -> old -> new then the .ashldi3.cmd file isn't
> updated while at old, so you get the same error as above. I'm not sure
> there's much we can practically do about that, aside perhaps avoiding
> the issue in future by somehow auto-deleting stale .*.cmd files.
>
> Cc'ing kbuild folk in case they have any bright ideas.



I do not have any idea better than if_changed.




> At least the straightforward old->new upgrade will work with the above
> fixup though. If you're okay with it I'm happy to apply as a fixup.
>






-- 
Best Regards
Masahiro Yamada