On Fri, 2011-10-14 at 21:19 +0100, Russell King - ARM Linux wrote:

On Fri, Oct 14, 2011 at 01:16:27PM -0700, Stephen Warren wrote:

quoted

Russell King wrote at Friday, October 14, 2011 2:12 PM:

quoted

I don't think that's so with the various flavours of platform specific
uboot which float around.  For instance, on the OMAP4430 SDP, the
following commands were used as supplied to load a uImage off the SD
card into RAM at a different address to which it was built for, and
execute it at that address:

mmcinit 0
fatload mmc 0 0x80300000 uImage
bootm 80300000

Whether the 'bootm' command then copied the image and called it there,
or whether it executed it at 0x80300000 I've no idea - but why then
load the image at a different address in the first place?

Yes, U-Boot's image handling looks at the image at 80300000, extracts the
"load address" from the image header, memcpy()'s the image to that address,
then jumps to the "entry address" in the image header.

Ah, so specifying that address is just a total waste of space then,
because you might as well specify an address which results in the
copy not being necessary.

However, I'd expect that uboot is dumb enough to still do the copy
irrespective of whether its already in the right place.

U-Boot doesn't do an unnecessary copy if the body of the image is
already at the load address specified in the image header.

Unfortunately, it also doesn't do a copy if the header of the image is
at the load address, (I guess to support images constructed with an
embedded header). This means that

  fatload mmc 0 0x80300000 uImage
  bootm 0x80300000

will crash as it will attempt to boot Linux by executing the image
header. To successfully boot without requiring a relocation we would
need:

  fatload mmc 0 0x80300000-sizeof(header) uImage
  bootm 0x80300000

-- 
Tixy