From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12888 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] Fix TLS layout of TLS variant I when there is a gap above TP Date: Sat, 2 Jun 2018 21:11:21 -0400 Message-ID: <20180603011121.GU1392@brightrain.aerifal.cx> References: <20180601235201.GO4418@port70.net> <20180602025911.GT1392@brightrain.aerifal.cx> <20180602071523.GP4418@port70.net> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1527988171 28354 195.159.176.226 (3 Jun 2018 01:09:31 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 3 Jun 2018 01:09:31 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-12904-gllmg-musl=m.gmane.org@lists.openwall.com Sun Jun 03 03:09:27 2018 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1fPHWR-0007IO-9S for gllmg-musl@m.gmane.org; Sun, 03 Jun 2018 03:09:27 +0200 Original-Received: (qmail 22240 invoked by uid 550); 3 Jun 2018 01:11:35 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 22179 invoked from network); 3 Jun 2018 01:11:34 -0000 Content-Disposition: inline In-Reply-To: <20180602071523.GP4418@port70.net> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:12888 Archived-At: On Sat, Jun 02, 2018 at 09:15:23AM +0200, Szabolcs Nagy wrote: > * Rich Felker [2018-06-01 22:59:11 -0400]: > > On Sat, Jun 02, 2018 at 01:52:01AM +0200, Szabolcs Nagy wrote: > > > In TLS variant I the TLS is above TP (or above a fixed offset from TP) > > > but on some targets there is a reserved gap above TP before TLS starts. > > > > > > This matters for the local-exec tls access model when the offsets of > > > TLS variables from the TP are hard coded by the linker into the > > > executable, so the libc must compute these offsets the same way as the > > > linker. The tls offset of the main module has to be > > > > > > alignup(GAP_ABOVE_TP, main_tls_align). > > > > > > If there is no TLS in the main module then the gap can be ignored > > > since musl does not use it and the tls access models of shared > > > libraries are not affected. > > > > > > The previous setup only worked if (tls_align & -GAP_ABOVE_TP) == 0 > > > (i.e. TLS did not require large alignment) because the gap was > > > treated as a fixed offset from TP. Now the TP points at the end > > > of the pthread struct (which is aligned) and there is a gap above > > > it (which may also need alignment). > > > > > > The fix required changing TP_ADJ and __pthread_self on affected > > > targets (aarch64, arm and sh) and in the tlsdesc asm the offset to > > > access the dtv changed too. > > > --- > > > > On first glance it all looks right. I'll read in more detail soon. > > Thanks! > > > > > passed my simple local-exec tests. > > > > Did you test all archs or just some? I think we should at least run > > libc-test (if it sufficiently tests TLS) on the affected archs to make > > sure there are no regressions. > > > > ran libc-test on various targets via qemu-user, i didnt see any regressions. I just setup libc-test to run under qemu-system-sh4, and confirmed failure before the patch, success with the patch applied. I don't have any other qemu-system environments setup, but success here looks like a good sign! Rich