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

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Message-ID: <4E4D916A.2090308@boundarydevices.com>
Date:	Thu, 18 Aug 2011 15:25:46 -0700
From:	Troy Kisky <troy.kisky@...ndarydevices.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Arnaud Lacombe <lacombar@...il.com>, linux-kbuild@...r.kernel.org,
	Nicolas Pitre <nico@...xnic.net>,
	Stephen Boyd <sboyd@...eaurora.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Sam Ravnborg <sam@...nborg.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: zImage: Skip relinking if nothing changes

On 8/18/2011 12:31 PM, Russell King - ARM Linux wrote:
> On Thu, Aug 18, 2011 at 02:03:43PM -0400, Arnaud Lacombe wrote:
>> 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) ?
> It is to be able to reuse the same file source file in both the main
> kernel and the decompressor, sometimes rebuilding it with differing
> options from the main kernel build.
>
> As the two environments are entirely separate, it is not always
> appropriate to clone the previously built object file.
>
> Hence, we copy the source file and re-build it.
>
> The alternative is that we could keep two copies of the same source
> in two different locations, but that's just plain idiotic just to
> satisfy some silly kbuild restriction.
>
Can the second file just contain a "#include " of the 1st?

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