From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/11776 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: possible bug in setjmp implementation for ppc64 Date: Tue, 1 Aug 2017 19:07:59 -0400 Message-ID: <20170801230759.GF1627@brightrain.aerifal.cx> References: <1501520360.0.593167188853569@go.bunnymail.go> <20170731203007.GB1627@brightrain.aerifal.cx> <20170801051042.GA14914@dora.lan> <20170801224533.GD1627@brightrain.aerifal.cx> 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 1501628893 26449 195.159.176.226 (1 Aug 2017 23:08:13 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 1 Aug 2017 23:08:13 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-11789-gllmg-musl=m.gmane.org@lists.openwall.com Wed Aug 02 01:08:09 2017 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 1dcgGl-0006Yx-NU for gllmg-musl@m.gmane.org; Wed, 02 Aug 2017 01:08:07 +0200 Original-Received: (qmail 21875 invoked by uid 550); 1 Aug 2017 23:08:12 -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 21855 invoked from network); 1 Aug 2017 23:08:11 -0000 Content-Disposition: inline In-Reply-To: <20170801224533.GD1627@brightrain.aerifal.cx> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:11776 Archived-At: On Tue, Aug 01, 2017 at 06:45:33PM -0400, Rich Felker wrote: > On Tue, Aug 01, 2017 at 08:28:27AM +0300, Alexander Monakov wrote: > > On Tue, 1 Aug 2017, Bobby Bingham wrote: > > > I think this either requires having different versions of setjmp/longjmp > > > for static and dynamic libc, > > > > Do you mean for non-pic vs pic objects? As I understand, when libc.a is > > built with -fpic (so it's suitable for static-pie), setjmp-longjmp need > > to preserve saved TOC at (r1+24). So presumably source code would need > > to test #ifdef __PIC__? > > > > > or to increase the size of jmpbuf so we can always save/restore both > > > r2 and the value on the stack, but this would be an ABI change. > > > > Would that work for non-pic, i.e. is (r1+24) a reserved location even in > > non-pic mode? If not, you can't overwrite it from longjmp. > > Pretty much certainly so; there is no separate "non-PIC ABI". PIC code > is just code that doesn't happen to do certain things not permissible > in PIC. It doesn't have additional permissions to do things that > otherwise wouldn't be permitted in "non-PIC code". > > In any case just saving and restoring both is not an ABI change, since > there's plenty of free space (896 bits worth of non-existant signals) > in the jmp_buf due to the "Hurd sigset_t" mess. It might also be possible to manually create both the entry points for setjmp, rather than letting the assembler auto-generate them, in which case I think the choice of which value to save just depends on which entry point was used. Thoughts? Rich