gecko-dev

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History

Mike Hommey a95697631f Bug 1606739 - Initialize the .dynamic section first. r=froydnj Differential Revision: https://phabricator.services.mozilla.com/D59078 --HG-- extra : moz-landing-system : lando		2020-01-08 14:30:21 +00:00
..
inject	Bug 1586358 - Replace existing instances of GENERATED_FILES with references to the GeneratedFile template r=firefox-build-system-reviewers,mshal	2019-10-07 21:15:19 +00:00
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
Makefile.in
moz.build
README
test-array.c
test-ctors.c
test.c	Bug 1547143 - Format the tree: Be prescriptive with the pointer style (left) r=Ehsan	2019-05-01 08:47:10 +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.