gecko-dev/build/unix/elfhack
Mike Hommey fd54149a7a Bug 1698706 - Fix linux build bustage. a=bustage-fix CLOSED TREE 2021-03-17 10:23:21 +02:00
..
inject Bug 1698706 - Fix linux build bustage. a=bustage-fix CLOSED TREE 2021-03-17 10:23:21 +02:00
Makefile.in
README
dummy.c
elf.cpp Bug 1495733 - Fix elfhack for files > 2GiB and < 4GiB. r=gsvelto 2020-10-21 07:30:38 +00:00
elfhack.cpp
elfxx.h Bug 1495733 - Fix elfhack for files > 2GiB and < 4GiB. r=gsvelto 2020-10-21 07:30:38 +00:00
inject.c
moz.build Bug 1654103: Standardize on Black for Python code in `mozilla-central`. 2020-10-26 18:34:53 +00:00
test-array.c
test-ctors.c
test.c

README

Elfhack is a program to optimize ELF binaries for size and cold startup
speed.

Presently, it is quite experimental, though it works well for the target
it was created for: Firefox's libxul.so.

Elfhack currently only does one thing: packing dynamic relocations ;
which ends up being a quite complex task, that can be summarized this
way:
- Remove RELATIVE relocations from the .rel.dyn/.rela.dyn section.
- Inject a small code able to apply relative relocations "by hand"
  after the .rel.dyn/.rela.dyn section.
- Inject a section containing relocative relocations in a different
  and more packed format, after the small code.
- Register the small code as DT_INIT function. Make the small code call
  what was initially the DT_INIT function, if there was one.
- Remove the hole between the new section containing relative
  relocations and the following sections, adjusting offsets and base
  addresses accordingly.
- Adjust PT_LOAD entries to fit new offsets, and add an additional
  PT_LOAD entry when that is necessary to handle the discrepancy between
  offsets and base addresses, meaning the section offsets may yet again
  need adjustments.
- Adjust various DT_* dynamic tags to fit the new ELF layout.
- Adjust section headers.
- Adjust ELF headers.

See http://glandium.org/blog/?p=1177#relocations for some figures.