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Re: putting a variable in an own section


Torsten Mohr <tmohr at s dot netic dot de> writes:

> > http://sourceware.org/binutils/docs-2.12/ld.info/Output-Section-LMA.html#Ou
> >tput%20Section%20LMA
> 
> thanks for that hint.  That's exactly what i was
> searching for, but i have some problems with it.
> 
> What's bothering me here is that there is no
> additional section generated, but isn't that
> necessary to mark a memory region as "used"
> or "reserved for something"?

On most systems it is not.  Since you are generating S-records, what
you would expect to see in the reserved memory region?  The S-records
will give you something to burn into PROM.  You don't need anything to
put into RAM.  Just initialize it at runtime.

> I'm testing this on v850-unknown-elf and i have
> for V850/SF1:
> 
> 	.text : { *(.text) _etext = . ; } >rom
> 	.rodata : { *(.rodata) } >rom
> 	.data : AT(ADDR(.rodata)) { *(.data) } >ram
> 
> 
> But this leads to an error in the line with ".data":
> v850-unknown-elf-ld: ADDR forward reference of section .rodata
> What's wrong here?

Not sure, really.  It might be a bug.  On the other hand, the script
doesn't really make sense, because you're trying to load both .rodata
and .data at the same LMA.

> Now i've tried the following, basicall i put everything that
> goes in .data into .rodata and set the size of .data
> to the size of .rodata:
> 
> 	.text : { *(.text) _etext = . ; } >rom
> 	.rodata : { *(.data) } >rom
> 	.data : { . += SIZEOF(.rodata); } >ram

I don't see any need to create the .data section at all.

> Do you see disadvantages of this approach?

I don't see a reason for it.

> .data doesn't go into S-Record, .rodata goes into S-Record.  Is this
> because *(.data) is now in .rodata and .data is just a "fill"?

Yes.  The .data output section has no contents, so there is nothing to
put in the S-records.  What would you expect to see there?

Ian


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