the current mkimage requires XIP images to have their entry point set to the load address + 64 bytes. my question is simply, why ? why cant the entry point be an arbitrary location ? i cant seem to find any technical reason for this restriction.
the Blackfin kernel has long been using an entry point way in the middle of the text. as an example, the typical output of our last release: $ bfin-uclinux-mkimage -l /tftpboot/uImage Image Name: Linux-2.6.28.10-ADI-2009R1.1-svn Created: Fri Jan 15 17:45:22 2010 Image Type: Blackfin Linux Kernel Image (gzip compressed) Data Size: 6370016 Bytes = 6220.72 kB = 6.07 MB Load Address: 00001000 Entry Point: 002f3938
this is because we store most of head.S (like __start) in the .init.text section. this code is never going to be returned to, so putting it in .text or even the very start of .text is pointless. when we added ROM kernel support, this no longer worked -- mkimage demands that the entry point be located right after the load address / uimage header.
so what am i missing ? or should i submit a patch to delete this check from the mkimage tool and let the entry point be arbitrary like non-xip ? -mike