gecko-dev/build/unix/elfhack
Sylvestre Ledru 34acbb653a Bug 1619165 - Reformat recent changes to the Google coding style r=andi
First reformat with clang-format 10

# ignore-this-changeset

Differential Revision: https://phabricator.services.mozilla.com/D68802
2020-04-25 09:40:08 +00:00
..
inject Bug 1616630 - Use py3_action for GENERATED_FILES that already support it; r=firefox-build-system-reviewers,kvark,rstewart 2020-02-21 00:05:17 +00:00
Makefile.in
README
dummy.c
elf.cpp Bug 1606739 - Initialize the .dynamic section first. r=froydnj 2020-01-08 14:30:21 +00:00
elfhack.cpp Bug 1579430 - mark some elfhack methods as `override`; r=glandium 2019-09-09 23:54:34 +00:00
elfxx.h Bug 1547143 - Format the tree: Be prescriptive with the pointer style (left) r=Ehsan 2019-05-01 08:47:10 +00:00
inject.c Bug 1547143 - Format the tree: Be prescriptive with the pointer style (left) r=Ehsan 2019-05-01 08:47:10 +00:00
moz.build
test-array.c
test-ctors.c
test.c Bug 1619165 - Reformat recent changes to the Google coding style r=andi 2020-04-25 09:40:08 +00:00

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.