linux-kernel - Re: [PATCH] ARM: zImage: Skip relinking if nothing changes

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Message-ID: <CACqU3MUV=-hQ_y3wLPBYRh+DhLcFqneWbURNQ66UyArb5UJcxw@mail.gmail.com>
Date:	Thu, 18 Aug 2011 14:03:43 -0400
From:	Arnaud Lacombe <lacombar@...il.com>
To:	Nicolas Pitre <nico@...xnic.net>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Sam Ravnborg <sam@...nborg.org>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] ARM: zImage: Skip relinking if nothing changes

Hi,

On Wed, Aug 17, 2011 at 11:44 PM, Nicolas Pitre <nico@...xnic.net> wrote:
> On Fri, 12 Aug 2011, Arnaud Lacombe wrote:
>> On Fri, Aug 12, 2011 at 4:48 PM, Arnaud Lacombe <lacombar@...il.com> wrote:
>> > On Fri, Aug 12, 2011 at 3:00 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
>> >> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
>> >> index 0c74a6f..937fd26 100644
>> >> --- a/arch/arm/boot/compressed/Makefile
>> >> +++ b/arch/arm/boot/compressed/Makefile
>> >> @@ -91,7 +91,7 @@ suffix_$(CONFIG_KERNEL_LZMA) = lzma
>> >>
>> >>  targets       := vmlinux vmlinux.lds \
>> >>                 piggy.$(suffix_y) piggy.$(suffix_y).o \
>> >> -                font.o font.c head.o misc.o $(OBJS)
>> >> +                font.o font.c head.o misc.o lib1funcs.o lib1funcs.S $(OBJS)
>> >>
>> >>  # Make sure files are removed during clean
>> >>  extra-y       += piggy.gzip piggy.lzo piggy.lzma lib1funcs.S
>> >> @@ -121,9 +121,7 @@ LDFLAGS_vmlinux += -X
>> >>  LDFLAGS_vmlinux += -T
>> >>
>> >>  # For __aeabi_uidivmod
>> >> -lib1funcs = $(obj)/lib1funcs.o
>> >> -
>> >> -$(obj)/lib1funcs.S: $(srctree)/arch/$(SRCARCH)/lib/lib1funcs.S FORCE
>> >> +$(obj)/lib1funcs.S: $(srctree)/arch/$(SRCARCH)/lib/lib1funcs.S
>> >>        $(call cmd,shipped)
>> >>
>> > You should be able to avoid the extra copy altogether by doing something ala:
>> >
>> > $(obj)/lib1funcs.o: $(srctree)/arch/arm/lib/lib1funcs.S
>> >        $(call cmd,as_o_S)
>> >
>> > note that I also remove the $(SRCARCH), as there is no other
>> > `arch/*/lib/lib1funcs.S' than `arch/arm/lib/lib1funcs.S'
>> >
>> I withdraw this proposal and will hack around this to find a proper
>> solution from within kbuild, and eventually come back on these uses
>> :-)
>
> Any progress on this?
>
> I have a patch doing multiple similar $(call cmd,shipped) at the moment
> and this is far from looking nice.
>
What is your use-case ? Is it re-use of code in a different
subdirectory (use-case presented in this thread), or aliasing of the
same source under different object name in the same directory (as used
in the alpha tree) ?

If it is the former, I potentially have a solution, but it is
highlighting bad use of the kbuild infrastructure. I have not been
able to yet measure the impact of the breakage, ie. either localized
or tree-wide. I should be able to provide you with more info,
hopefully, this evening.

Thanks,
 - Arnaud
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