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

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Message-ID: <20090613182540.GJ16220@shareable.org>
Date:	Sat, 13 Jun 2009 19:25:40 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Mike Frysinger <vapier.adi@...il.com>
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

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.
> >
> > What does this have to do with FDPIC?  I don't see anything that is
> > specific to FDPIC about this code, other than FDPIC being the type of
> > ELF used on Blackfin.  If an MMU were added to some future Blackfins,
> > wouldn't this code be used for non-FDPIC ELF too?
> 
> no, because with a MMU, the memory would be virtualized and we could
> handle it dynamically

Wouldn't you still want to put some things into local L1 SRAM, using thos, perhaps by
flagging it instead of

> > 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.

Anyway,

Acked-By: Jamie Lokier <jamie@...reable.org>

-- Jamie
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