From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <1389154189.2076.5.camel@concordia> Subject: Re: [PATCH] powerpc: Fix alignment of secondary cpu spin vars From: Michael Ellerman To: Olof Johansson Date: Wed, 08 Jan 2014 15:09:49 +1100 In-Reply-To: <20140103081219.GA10233@quad.lixom.net> References: <1388264507-5100-1-git-send-email-olof@lixom.net> <20140103081219.GA10233@quad.lixom.net> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: linuxppc-dev , "linux-kernel@vger.kernel.org" , Anton Blanchard , chzigotzky@xenosoft.de List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2014-01-03 at 00:12 -0800, Olof Johansson wrote: > On Thu, Jan 02, 2014 at 11:56:04PM -0800, Olof Johansson wrote: > > > This makes things interesting though. The BE/LE trampoline code > > assumes at least 3 consecutive instructions. What was the reasoning > > behind entering the kernel LE instead of keeping the old boot protocol > > and just switching to LE once kernel is loaded? Is it actually used on > > some platforms or is this just a theoretical thing? > > Actually, adding a little hack that zeroes out the memory once we're done > executing it will work just fine too. I know this is sort of icky, but maybe > it'll be good enough for now? > > Of course, main worry is that this is just hiding some latent NULL deref in > the kernel now... :-/ Wow, that would have to come close to winning the grossest-hack-in-arch-powerpc award :) Have you tried changing the value at 8 to point to a reserved page? Some other possibilities: * Change the #define so FIXUP_ENDIAN is empty for PASEMI, that would mean you'd only be able to boot pasemi_defconfig. * Move the hack into FIXUP_ENDIAN cheers