From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12885 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: Fri, 1 Jun 2018 22:59:11 -0400 Message-ID: <20180602025911.GT1392@brightrain.aerifal.cx> References: <20180601235201.GO4418@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 1527908241 4576 195.159.176.226 (2 Jun 2018 02:57:21 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 2 Jun 2018 02:57:21 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-12901-gllmg-musl=m.gmane.org@lists.openwall.com Sat Jun 02 04:57:17 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 1fOwjE-000171-Rh for gllmg-musl@m.gmane.org; Sat, 02 Jun 2018 04:57:16 +0200 Original-Received: (qmail 26164 invoked by uid 550); 2 Jun 2018 02:59:24 -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 26143 invoked from network); 2 Jun 2018 02:59:24 -0000 Content-Disposition: inline In-Reply-To: <20180601235201.GO4418@port70.net> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:12885 Archived-At: 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. Rich