michael@0: Elfhack is a program to optimize ELF binaries for size and cold startup
michael@0: speed.
michael@0: 
michael@0: Presently, it is quite experimental, though it works well for the target
michael@0: it was created for: Firefox's libxul.so.
michael@0: 
michael@0: Elfhack currently only does one thing: packing dynamic relocations ;
michael@0: which ends up being a quite complex task, that can be summarized this
michael@0: way:
michael@0: - Remove RELATIVE relocations from the .rel.dyn/.rela.dyn section.
michael@0: - Inject a small code able to apply relative relocations "by hand"
michael@0:   after the .rel.dyn/.rela.dyn section.
michael@0: - Inject a section containing relocative relocations in a different
michael@0:   and more packed format, after the small code.
michael@0: - Register the small code as DT_INIT function. Make the small code call
michael@0:   what was initially the DT_INIT function, if there was one.
michael@0: - Remove the hole between the new section containing relative
michael@0:   relocations and the following sections, adjusting offsets and base
michael@0:   addresses accordingly.
michael@0: - Adjust PT_LOAD entries to fit new offsets, and add an additional
michael@0:   PT_LOAD entry when that is necessary to handle the discrepancy between
michael@0:   offsets and base addresses, meaning the section offsets may yet again
michael@0:   need adjustments.
michael@0: - Adjust various DT_* dynamic tags to fit the new ELF layout.
michael@0: - Adjust section headers.
michael@0: - Adjust ELF headers.
michael@0: 
michael@0: See http://glandium.org/blog/?p=1177#relocations for some figures.