GNU linker script question

Hi,

I'm working on an embedded project at home using GNU gcc & ld.  I need
to burn a function into a particular flash rom address.  My attempt
will be to place the function in its own file and define a section
like:

SECTIONS {
   MySection 0x10000:
  {
    MyFile.o
  }
  _MySectionEnd =  . ;
}

Then, in my app, I should be able to refer to _MySectionEnd to get the
end address of the function.  I'm pretty sure this, or a variant will
work (my syntax might not be 100% as I'm an ld newbie).

But, is there a better way?  Also, while this is OK for one, or a few
functions, it would be a pain if I ever had to do a lot of 'em.  I know
there's a "section" attribute for gnu C, so I was wondering if I can
create one or more MySection1 and _MySection1End symbol pairs in a
linker script and somehow place each function at the desired section
while all functions reside in one file?


Thanks for the ideas!



Jim

Just to avoid a bunch of comments correcting me, the linker script
above turned out to be more like:

	.text :
	{
		MyFunc.o (.text)
		_MyFuncEnd = .;
		*(.text)
		*(.rodata)
		. = ALIGN(0x4) ;
		__etext = .;
	}  > ram


Jim

p.s.
I did finally find something about causing gcc to create each function
in it's own section as if it were in its own file, but it didn't say
how you knew what the section names would be.  I'm guessing it would be
a derivative of the function name.

Jim <adirondackmtn@yahoo.com> wrote:

> I know there's a "section" attribute for gnu C, so I was wondering if
> I can create one or more MySection1 and _MySection1End symbol pairs in
> a linker script and somehow place each function at the desired section
> while all functions reside in one file?

Yes, go to <http://www.devrs.com/gba/ccode.php#cmisc> and download the
crtls package for an example of how it can be done.

-a

Jim wrote:
> Just to avoid a bunch of comments correcting me, the linker script
> above turned out to be more like:
> 
> 	.text :
> 	{
> 		MyFunc.o (.text)
> 		_MyFuncEnd = .;
> 		*(.text)
> 		*(.rodata)
> 		. = ALIGN(0x4) ;
> 		__etext = .;
> 	}  > ram
> 
> 
> Jim
> 
> p.s.
> I did finally find something about causing gcc to create each function
> in it's own section as if it were in its own file, but it didn't say
> how you knew what the section names would be.  I'm guessing it would be
> a derivative of the function name.
> 

If you are only looking for the end address of a single function, then 
you could put that function in its own named section (look in the gcc 
manual for "function attributes").  I've done this on several targets 
for putting flash routines in a separate section so that they run from 
ram rather than flash.

ammonton@cc.full.stop.helsinki.fi wrote:
> Jim <adirondackmtn@yahoo.com> wrote:
>
> > I know there's a "section" attribute for gnu C, so I was wondering if
> > I can create one or more MySection1 and _MySection1End symbol pairs in
> > a linker script and somehow place each function at the desired section
> > while all functions reside in one file?
>
> Yes, go to <http://www.devrs.com/gba/ccode.php#cmisc> and download the
> crtls package for an example of how it can be done.
> 
> -a

That's an interesting site.  Thanks.


Jim