I can't find this patch in changelogs and snapshots. This patch will not be lost?
Alexander Lebedev 12 апр. 2016 г. 15:39 пользователь "Willy Tarreau" <w...@1wt.eu> написал: > On Tue, Apr 12, 2016 at 11:00:17AM +0200, Vincent Bernat wrote: > > ??? 12 avril 2016 10:38 +0200, Willy Tarreau <w...@1wt.eu> : > > > > > BTW, armv5 is very handy to test alignment. By default it does crap > > > (silent read of the wrong word) but you can configure it to fault or > > > to emulate the alignment. I've found lots of such issues with just > > > a Seagate Dockstar. > > > > Funny fact, I did learn that you can make x86 sensible to > > alignment. > > Yes absolutely, it's by setting the AC flag in EFLAGS. And the funniest > part of it is that I used to believe for many years that it was enabled > by default on Linux and discovered I was wrong a few years ago when Linus > reimplemented his fast SHA1 version for Git which relies on unaligned > accesses. My first thought was "where did he get rid of alignment check?" > then I found he never did :-) > > > Unfortunately, the libc is not ready for that: > > > > http://paste.debian.net/427415/ > > I didn't know it was permitted to clear it from userland (the popf > instruction is restricted so the kernel can do whatever it wants with > your flags). But indeed the libc knows unaligned accesses are supported > and makes use of this useful capability! > > Ah, it feels good to discuss asm and processor flags again on this list, > it changes from systemd issues and spam complaints :-) > > Cheers, > Willy > > >
