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* [gentoo-dev] [RFC] News item: GCC 6 defaults to USE="pie ssp"
@ 2017-05-09 17:26 99% Matthias Maier
  0 siblings, 0 replies; 1+ results
From: Matthias Maier @ 2017-05-09 17:26 UTC (permalink / raw
  To: gentoo-dev; +Cc: toolchain

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Title: GCC 6 defaults to USE="pie ssp"
Author: Matthias Maier <tamiko@gentoo.org>
Content-Type: text/plain
Posted: 2017-05-07
Revision: 1
News-Item-Format: 1.0
Display-If-Installed: >=sys-devel/gcc-6.3.0
Display-If-Keyword: amd64

In Gentoo, several GCC features can be default disabled or enabled 
via use-flags of sys-devel/gcc. Starting with gcc-4.8.3 we have already
enabled default SSP [1]. Since the PIE patchset for default position 
independent executable support was integrated upstream [2,3], starting 
with gcc-6.3 we are also enabling PIE by default (via a default-enabled 
use-flag pie) in regular (non-hardened) profiles.

[Additionally, following Gentoo policies, the default-off use-flags 
nopie (only present in Hardened) and nossp are replaced starting with 
gcc-6 by default-on use-flags pie and ssp.]

Be advised that switching from an older version to GCC 6 will enable the 
PIE feature by default. This should not cause many problems, but it may 
be necessary to recompile parts of your userland. An indicator are 
linker errors of the form [4]

  relocation R_X86_64_32 against `.rodata.str1.1' can not be used when
  making a shared object; recompile with -fPIC

[1] https://www.gentoo.org/support/news-items/2014-06-15-gcc48_ssp.html
[2] https://gcc.gnu.org/gcc-6/changes.html
[3] A big thanks to all developers and members of the Gentoo community that
    made upstreaming the pie patchset and other hardening options possible!
[4] https://bugs.gentoo.org/617698

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