[U-Boot-Users] arm linux images with load address == entry point

["Uwe Kleine-König" <ukleinek@informatik.uni-freiburg.de>]

Hello,

the make target "uImage" in the linux kernel calls mkimage as follows:

	 $(MKIMAGE) -A arm -O linux -T kernel \
	 -C none -a $(ZRELADDR) -e $(ZRELADDR) \
	 -n 'Linux-$(KERNELRELEASE)' -d $< $@

(see http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=arch/arm/boot/Makefile;h=ec9c400c7f82d171ba9ccf6e52cdb055bf1a50cb;hb=HEAD,
line 63)

i.e. sets the load address and the entry point to the same address.

This part is unchanged since it was introduced in 2003.


If I understand do_bootm and do_bootm_linux (for arm, in
lib_arm/armlinux.c) correctly, the first asserts that the image is
loaded to the load address[1] and the latter jumps to entry point.

For an image created with the above rule from the vanilla kernel, that
means, jump to the header (instead of the actual image@entry point +
0x40).

So I think the linux rule is wrong, or did I miss anything?

The U-Boot I have on my target here has somewhere after the crc check in
do_bootm the following:

        hdr->ih_load = htonl(addr);
        hdr->ih_ep = htonl(addr + 0x40);

(Actually it's still worse, load_addr instead of addr is used ...)
This works but is ugly.

I wonder how other people using U-Boot + Linux on ARM handle that.

Best regards
Uwe

PS: Linux uses entry point == load address == 0 for PowerPC.  Didn't
look in the PowerPC version of bootm_linux, but maybe it has the same
problem?

[1] For Linux this is not needed, because the decompressor (at least for
2.6) is position independant.  But that's another topic.
-- 
Uwe Kleine-K?nig

http://www.google.com/search?q=1+stone%3D