On Tue, 26 May 2020 10:45:39 -0400 Mike Gilbert <flop...@gentoo.org> wrote: > > Note that having the 'pic' useflag should be considered something > > to be fixed: rewrite the asm in a PIC way. But these days nobody > > has the will to do it since this is mostly an issue on x86+pax, > > both being slowly decreasing. > > Given that PaX has been stripped out of official Gentoo kernels due to > the grsecurity licensing issue, I wonder if there is any other good > reason to keep the "pic" USE flag today. Surely this affects a very > small population of users.
I couldn't find any recent reference, but PIC shared libs used to be a QA policy. There's mainly two reasons to it: First is W^X enforcement; non PIC shared libs are refused by the x86_64 linker so a non-issue there, on x86 you need pax to emulate it because the mmu doesn't support the X part; I don't know about other arches. Then there is the small memory waste done because those libs will be loaded COW and thus their "code" is not shared anymore between processes. And the small startup performance hit to perform the relocations. The latter part affects everyone, and the rule of thumb for having a pic useflag (instead of always pic) is that the gain for non-pic asm is better than the loss of non-pic shared libs. This is subjective but usually a no-brainer for multimedia packages. This is probably something to bring up to QA too.
