From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12039 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: How to handle attempts to combine ARM Thumb with frame pointers? Date: Thu, 26 Oct 2017 20:30:10 -0400 Message-ID: <20171027003010.GC1627@brightrain.aerifal.cx> References: <20171008032153.GH1627@brightrain.aerifal.cx> <20171025211623.GU15263@port70.net> <20171026170054.GA1627@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 1509064225 4133 195.159.176.226 (27 Oct 2017 00:30:25 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 27 Oct 2017 00:30:25 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) Cc: musl@lists.openwall.com To: Adhemerval Zanella Original-X-From: musl-return-12052-gllmg-musl=m.gmane.org@lists.openwall.com Fri Oct 27 02:30:21 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 1e7sXT-0000OT-Ji for gllmg-musl@m.gmane.org; Fri, 27 Oct 2017 02:30:19 +0200 Original-Received: (qmail 19863 invoked by uid 550); 27 Oct 2017 00:30:24 -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 19839 invoked from network); 27 Oct 2017 00:30:23 -0000 Content-Disposition: inline In-Reply-To: Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:12039 Archived-At: On Thu, Oct 26, 2017 at 04:46:04PM -0200, Adhemerval Zanella wrote: > >>> http://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/arm/sysdep.h;h=6a64351cdd87c2041d639a17efc9f681262d5e3f;hb=HEAD#l335 > >>> > >> > >> Why do you mean by glibc strategy might not be acceptable? What > >> kind of issue are you referring on interrupt case? > > > > If you're compiling with frame pointers because you want them to be > > present (and always valid) for debugging purposes or similar, there's > > no way to achieve that while making syscalls -- and the most likely > > place for a process to get stopped debugging is usually at a syscall. > > Maybe this doesn't matter. It's not something we can change, just an > > observation about a problem with the ABI, I think. > > I think this might be a problem for musl where it does not provide > unwind information through CFI. For debugging with GLIBC, afaik GDB > will these information along libgcc unwind symbols to get correct call > frame and libc-do-syscall.S does seems to have correct CFI annotations. In that case, it might make sense to add debug or runtime unwind information to pure asm functions that clobber the frame pointer, which would basically just be __syscall I think. But this is a separate topic from fixing the build issue at hand. Rich