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

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Message-ID: <8bd0f97a0906131732v5394eaf5gb0f7862dfe7f58f3@mail.gmail.com>
Date:	Sat, 13 Jun 2009 20:32:51 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Jamie Lokier <jamie@...reable.org>
Cc:	uClinux development list <uclinux-dev@...inux.org>,
	linux-kernel@...r.kernel.org, Jie Zhang <jie.zhang@...log.com>,
	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

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.
-mike
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