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

[Jie Zhang <jie.zhang@analog.com>]

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@analog.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