gecko-dev/build/unix/elfhack
Mike Shal d8e4653d19 Bug 1611326 - Default to py3_action, and add a py2 attribute to GENERATED_FILES; r=firefox-build-system-reviewers,rstewart
GENERATED_FILES now defaults to python3 unless py2=True is specified as
an argument. All existing GENERATED_FILES scripts and GeneratedFile
templates have the py2=True attribute added, so this patch should
effectively be a no-op.

Going forward, individual scripts can be converted to python3 and their
corresponding py2=True attribute can be deleted. In effect, this patch
will be backed out in pieces until all scripts run in python3, at which
point the py2 attribute itself can be removed.

Differential Revision: https://phabricator.services.mozilla.com/D60919

--HG--
extra : moz-landing-system : lando
2020-02-14 13:22:46 +00:00
..
inject Bug 1611326 - Default to py3_action, and add a py2 attribute to GENERATED_FILES; r=firefox-build-system-reviewers,rstewart 2020-02-14 13:22:46 +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
elfxx.h
inject.c
moz.build
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.