[U-Boot-Users] Destination link address

Wolfgang Denk wd at denx.de
Tue Jul 8 16:20:37 CEST 2003

In message <20030708140659.GA26624 at buici.com> you wrote:
> > It doesn't make it easier, but not really difficult either.
> Let me rephrase that.  It makes it impossible to use GDB since the
> symbols don't point to the correct base.  I suppose that there might
> be a command in GDB to move the base address.  I've never looked for

You can use GDB. Just use the "add-symbol-file" to  load  the  symbol
table to the relocation address.

> one because it is too easy to make the linker do the heavy lifting.

But this does not work for all architectures / all boards.

> When I was working on the x86 version, I wanted to be able to debug
> all of the code using gdb.  This means telling the linker exactly what
> is going on.  It has directives to indicate the difference between
> load address and execution address for just this purpose.  So,
> 'proper' means that the ELF file reflects what is happen when the
> program runs.

This does not help much, or does it? In  the  end  you  will  burn  a
binary image to some flash memory, right? Then this method breaks.

> What I don't see is the utility of linking code to an address where it
> definitely won't execute.  If it is moved elsewhere due to exigencies

We link the code to the flash  address  where  it  _starts_executing_
when  the  CPU  wakes  up  from  reset.  The  fact  that it might get
relocated to a different address somewhere in  RAM  is  a  completely
different story. Um, at least a different (later) chapter.

> of the target then there is nothing we can do about that.  However, if
> it is likely to execute at a known address it is helpful to make that
> clear in the ELF file.

But the ELF file cannot be installed in flash.

You may want to read the README for some explanations how  his  works
for example on PowerPC systems.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
It is necessary to have purpose.
	-- Alice #1, "I, Mudd", stardate 4513.3

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