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

[Matt Redfearn]

Hi James,

On 18/04/18 00:09, James Hogan wrote:
> 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.
>
> 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.

Unbelievable how fragile this change is proving to be :-/
Yeah fixup looks good to me.

Thanks,
Matt

> Cheers
> James