Remapping to Processor code region Vs Without remapping

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What is the differences between:  
1.Remapping memories to processor code region and  
2.Executing the program code built with absolute addresses without
remapping

I read something about executing multiple image in a microprocessor (ARM
Cortex-M3) and i'm ambiguous about differences between executing with
remapping image to "code space" and without remapping?

I would be grateful if you help me to understand these two concept
clearly

thanks


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Re: Remapping to Processor code region Vs Without remapping
On 12/7/2017 7:42 AM, mohsenzandie wrote:
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It sounds like you're asking about how relocatable code works.  
Relocatable code is code that has little to no absolute memory  
references.  That means it can (in theory) run successfully at any start  
address and references memory objects loaded at user defined addresses.

I'm no expert about relocatable code technology.  Google will probably  
give you a sufficient number of matches if you give it "how does  
relocatable code work".  I believe many modern tool sets can build  
relocatable code as an option.

JJS

Re: Remapping to Processor code region Vs Without remapping
On 07.12.2017 ?. 19:59, John Speth wrote:
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Not so sure this is what he is asking but in my vocabulary this is
called "position independent code", that's how it was called back in
my 6809 days :-). Means exactly the same thing of course.

Last 20+ years I have been writing essentially position independent
code (which is also reentrant), under dps this is "normal".
One can run fixed address code and is allowed to write non-reentrant
code as well but I don't know it these features work, never tried
them out... :).

The OP seems to ask just about pages (4k on ARM?) being mapped as
executable or not, I am not familiar with the ARM MMU so this is
better explained by someone else.

Dimiter

======================================================
Dimiter Popoff, TGI             http://www.tgi-sci.com
======================================================
http://www.flickr.com/photos/didi_tgi/



Re: Remapping to Processor code region Vs Without remapping
On 08/12/17 02:42, mohsenzandie wrote:
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It sounds like you are asking about Harvard architecture machines.
These have program memory, and data memory. Instructions are fetched
from program memory, never from data memory. Data cannot be fetched
from or written to program memory (except using special features).

That means to be able to load and execute a program, there must be
some special way to store data into program memory before executing
it.

Re: Remapping to Processor code region Vs Without remapping
wrote:

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Some DSP's can run code from data memory, I guess it's dependant upon
processor type.

Cheers

Re: Remapping to Processor code region Vs Without remapping
On 08/12/17 11:23, Martin Riddle wrote:
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In which case they aren't (strict) Harvard architectures,
as I pointed out.

The AVR is like that; special instructions support data reads
on instruction space, which is annoyingly poorly handled by
compilers for accessing constant data tables.

Re: Remapping to Processor code region Vs Without remapping
On 07/12/17 16:42, mohsenzandie wrote:
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I think you are going to have to try again, explaining in a lot more
detail what you are trying to do.  Give information about the processor
in question, and how you hope the code will work.

Also make sure you are online and checking regularly for replies so that
you can add information as requested.  This is easier if you use a
proper newsreader and newsclient, rather than a web interface like
EmbeddedRelated.

There are plenty of knowledgeable people here who will help you if they
can, but we need to know what you are asking!


(And if this is homework for a course of some sort, say so.  People will
try to give you helpful hints if you are honest about it.)


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