From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fed1rmmtao05.cox.net (fed1rmmtao05.cox.net [68.230.241.34]) by ozlabs.org (Postfix) with ESMTP id CDB2167B20 for ; Fri, 8 Apr 2005 08:14:42 +1000 (EST) Date: Thu, 7 Apr 2005 15:14:40 -0700 From: Tom Rini To: Kumar Gala Message-ID: <20050407221440.GT3396@smtp.west.cox.net> References: <20050407173821.GQ3396@smtp.west.cox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Cc: linuxppc-dev@ozlabs.org Subject: Re: [PATCH] invalid instructions in kernel mode List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Apr 07, 2005 at 04:41:59PM -0500, Kumar Gala wrote: > > On Apr 7, 2005, at 12:38 PM, Tom Rini wrote: > > >On Thu, Mar 31, 2005 at 07:47:32PM +0200, Fillod Stephane wrote: > > > >> When CPU has no (classic) FPU, and math emulation is disabled, > > > fp instructions are not allowed in kernel mode. > > [snip] > > > --- linux/arch/ppc/kernel/misc.S????? 26 Mar 2005 03:28:36 -0000 > > > 1.1.1.2 > > > +++ linux/arch/ppc/kernel/misc.S????? 31 Mar 2005 16:33:25 -0000 > > > @@ -1096,7 +1096,8 @@ > > >?? * and exceptions as if the cpu had performed the load or store. > > >?? */ > > >? > >> -#if defined(CONFIG_4xx) || defined(CONFIG_E500) > >> +#if !(defined(CONFIG_4xx) || defined(CONFIG_E500) || > > > defined(CONFIG_8xx)) ||? defined(CONFIG_MATH_EMULATION) > >> +#if defined(CONFIG_4xx) || defined(CONFIG_E500) > >>? _GLOBAL(cvt_fd) > >>? ???? lfs???? 0,0(r3) > > >? ???? stfd??? 0,0(r4) > > > @@ -1125,6 +1126,7 @@ > > >? ???? stfd??? 0,-4(r5) > > >? ???? blr > > >? #endif > > > +#endif > > > >The problem here is, HEY! (classic) FP instrs in the kernel.? The > > question is why?? Or rather, why are these four classic FP instrs > > (lfs/lfd/stfd/stfs) being done on CONFIG_4xx || E500 when neither has > > classic FP?? I think the problem here is that on !FPU > >(which is 4xx||E500||8xx, or so), we need to rewrite these two > > functions (yes, 8xx does emulate them if hit, but that's a tangent). > > What is not clear to me is what condition causes these to get hit on an > e500. They are called in align.c from fix_alignment(). As has been said, some of the stress testing apps in LTP will trigger this. Since the comment around the code in question (in fix_alignent()) is /* Single-precision FP load and store require conversions... */ perhaps it's more valid to not define these functions on e500 || 4xx, and make the two cases in the switch there depend on !e500 && !4xx. -- Tom Rini http://gate.crashing.org/~trini/