From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 709381A089E for ; Fri, 28 Nov 2014 03:08:49 +1100 (AEDT) Date: Thu, 27 Nov 2014 10:08:29 -0600 From: Segher Boessenkool To: Peter Bergner Subject: Re: [PATCH] powerpc: 32 bit getcpu VDSO function uses 64 bit instructions Message-ID: <20141127160829.GA26139@gate.crashing.org> References: <1417036288-22079-1-git-send-email-anton@samba.org> <1417041497.12952.2.camel@concordia> <1417045827.16862.32.camel@otta> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1417045827.16862.32.camel@otta> Cc: linuxppc-dev@lists.ozlabs.org, Anton Blanchard , paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Nov 26, 2014 at 05:50:27PM -0600, Peter Bergner wrote: > On Thu, 2014-11-27 at 09:38 +1100, Michael Ellerman wrote: > > On Thu, 2014-11-27 at 08:11 +1100, Anton Blanchard wrote: > > > I used some 64 bit instructions when adding the 32 bit getcpu VDSO > > > function. Fix it. > > > > Ouch. The symptom is a SIGILL I presume? > > Nope, you don't get a SIGILL when executing 64-bit instructions in > 32-bit mode, so it'll happily just execute the instruction, doing > a full 64-bit compare. I'm guessing that the upper 32-bits of both > r3 and r4 contain zeros, so we're probably just getting lucky. You will get a SIGILL if you run on 32-bit hardware. > > Could we catch this by forcing -m32 in the CFLAGS for vdso32 ? > > As Segher mentioned, GCC passing -many down to the assembler means > -m32 won't help. It was due to Anton disabling that gcc "feature", > that this was caught. There are extremely many complex failure cases without the -many. Feel free to work on removing it, I won't :-) Segher