linux-kernel - Re: [PATCH 4/6] Add support for LZO-compressed kernels for ARM

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Message-ID: <4A7C2BA4.7030408@parrot.com>
Date:	Fri, 7 Aug 2009 15:27:00 +0200
From:	Matthieu CASTET <matthieu.castet@...rot.com>
To:	Albin Tonnerre <albin.tonnerre@...e-electrons.com>
CC:	Alain Knaff <alain@...ff.lu>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"sam@...nborg.org" <sam@...nborg.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-embedded@...r.kernel.org" <linux-embedded@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/6] Add support for LZO-compressed kernels for ARM

Albin Tonnerre a écrit :
> On Fri, Aug 07, 2009 at 01:50:03PM +0200, Matthieu CASTET wrote :
>> Albin Tonnerre a écrit :
>>> On Fri, Aug 07, 2009 at 11:36:56AM +0200, Alain Knaff wrote :
>>>> On 08/07/09 11:24, Albin Tonnerre wrote:
> 
>>>>> Regards,
> 
>>>> Could it be that the patches that remove division (zutil.h and inflate.c)
>>>> have somehow not been applied?
> 
>>> Indeed, they've not been applied. However, I'd rather try to understand why
>>> exactly this is an issue when compiling with -Os and not -O2 instead of working
>>> around it by removing the divisions.
> 
>> Look at the generated code.
> 
>> Arm doesn't have division instruction.
>> May be at -Os gcc emit a call to the software division, but at -O2 it
>> manage to optimise the division (transform it in shift, inline some
>> builtin, ...).
> 
> Yes, I figured that out. What I don't get, though, is that it fails while the
> software division symbol (__aeabi_uidivmod here) does seem to be provided by
> libgcc.
> 
AFAIK we don't link the kernel with libgcc.
That's why the kernel provide __aeabi_* in arch/arm/lib
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