On Mon, 2020-05-25 at 17:04 -0400, Mike Gilbert wrote: > On Mon, May 25, 2020 at 3:18 PM Michał Górny <mgo...@gentoo.org> > wrote: > > On Mon, 2020-05-25 at 19:49 +0200, Alexis Ballier wrote: > > > On Mon, 25 May 2020 11:26:26 -0400 > > > Mike Gilbert <flop...@gentoo.org> wrote: > > > > > > > On Mon, May 25, 2020 at 9:13 AM Alexis Ballier < > > > > aball...@gentoo.org> > > > > wrote: > > > > > On Sun, 24 May 2020 20:25:11 +0000 (UTC) > > > > > "Thomas Deutschmann" <whi...@gentoo.org> wrote: > > > > > > > > > > > commit: 6e149596cc76f1bbcee6720828c8c8c92420f2a3 > > > > > > Author: Thomas Deutschmann <whissi <AT> gentoo <DOT> > > > > > > org> > > > > > > AuthorDate: Sun May 24 19:47:08 2020 +0000 > > > > > > Commit: Thomas Deutschmann <whissi <AT> gentoo <DOT> > > > > > > org> > > > > > > CommitDate: Sun May 24 20:23:53 2020 +0000 > > > > > > URL: > > > > > > https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=6e149596 > > > > > > > > > > > > media-libs/x265: drop USE=pic > > > > > > > > > > > > Gentoo's toolchain uses PIC by default. Since USE=asm was > > > > > > added, > > > > > > we no longer need a USE flag to control that behavior. > > > > > > > > > > You got it wrong here it seems: USE=pic does not control > > > > > whether > > > > > the toolchain produces PIC or not. Shared libs always are, > > > > > and have > > > > > always been, built that way on Gentoo. > > > > > In this case, USE=pic means "no matter what it costs, I do > > > > > not want > > > > > textrels", for the cases of hand written assembly that has to > > > > > be > > > > > rewritten to support PIC. And, still in this case, this costs > > > > > a lot > > > > > of performance, so it is enabled by default on hardened > > > > > profiles > > > > > and not others. > > > > > Textrels work fine (on some architectures), they disallow W^X > > > > > and > > > > > force each process using the shared lib to make a "copy" at > > > > > runtime > > > > > in order to resolve relocations, so are not desirable but > > > > > sometimes > > > > > the cost outweights the gain. > > > > > > > > > > Plus, profiles/features/hardened enables pic by default but > > > > > knows > > > > > nothing about USE=asm so this is a regression for them. > > > > > > > > The USE flag toggles use of assembly, not use of PIC. The > > > > default USE > > > > value in the hardened profile should not drive decisions on > > > > what we > > > > name USE flags. > > > > > > ... but using a global well documented useflag instead of a local > > > invention should drive such decisions. > > > > What 'global well documented useflag'? > > It's neither global, nor well-documented, but several packages do > define it locally. >
https://gitweb.gentoo.org/repo/gentoo/historical.git/commit/profiles/use.desc?id=103236c295aa30e5e42cfc8a7429e4eea5f0d680 https://gitweb.gentoo.org/repo/gentoo/historical.git/commit/profiles/use.desc?id=784deb7134b9d430546557a8f8a0877bf35c02ba I guess this hasn't been really discussed back then. It is also used in a global way in profiles (make.defaults). > Personally, I think it should be renamed to "asm" or something > similar > in the majority of cases where it actually disables all use of > assembly code. Thankfully these days there's usually no need to disable asm to have pic. hardened has no mention of that flag, and I think that e.g. for openssl they would have noticed long ago. And again, 'asm' as a useflag makes no sense: if it works and simply replaces a C function by a faster one then it shouldn't even be an useflag. 'pic' on the other hand conveys the tradeoff idea.
