linux-kernel - Re: [uClinux-dev] [PATCH/RFC] FDPIC: add hook for arches to customize program header parsing

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Date:	Sun, 14 Jun 2009 08:42:42 +0800
From:	Jie Zhang <jie.zhang@...log.com>
To:	Mike Frysinger <vapier.adi@...il.com>
CC:	Jamie Lokier <jamie@...reable.org>,
	uClinux development list <uclinux-dev@...inux.org>,
	linux-kernel@...r.kernel.org, Greg Ungerer <gerg@...inux.org>,
	uclinux-dist-devel@...ckfin.uclinux.org,
	David McCullough <davidm@...pgear.com>
Subject: Re: [uClinux-dev] [PATCH/RFC] FDPIC: add hook for arches to customize
 	program header parsing

Mike Frysinger wrote:
> On Sat, Jun 13, 2009 at 14:25, Jamie Lokier wrote:
>> Mike Frysinger wrote:
>>> On Sat, Jun 13, 2009 at 12:13, Jamie Lokier wrote:
>>>> Mike Frysinger wrote:
>>>>> From: Jie Zhang <jie.zhang@...log.com>
>>>>>
>>>>> The Blackfin port has custom program header flags/addresses for
>>>>> automatically loading regions into the dedicated on-chip SRAM.  So add a
>>>>> hook for ports to leverage.
>>>> It looks like a way for certain special executables to load themselves
>>>> into fixed regions of the on-chip SRAM - and promptly crash if another
>>>> executable does the same.  Not so much a general executable format, as
>>>> a hack to load something specific which should only be done once at a
>>>> time.  What am I missing here?
>>> the addresses are keys, not fixed and/or "real" addresses
>> Oh, I see that is indeed quite nice :-)
>>
>> I see it checks for both flags and special address values.  Are the
>> special address checks mainly historical, as usually flags/types are
>> used to designate special memory types in ELF.
> 
> the EF bits are more for smaller/statically linked applications where
> you want to place the entire ELF into SRAM.  the special PHDRs are for
> selectively compiled code -- i.e. you've done a little bit of
> profiling and testing and know which ones are the hot spots.

Yes. Those e_flags works for the whole ELF file. And these specific 
addresses work as p_flags. May be in future I can add processor specific 
p_flags.


Jie


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