Date: Wed, 1 Apr 2009 01:09:45 +0200 From: Olivier Houchard <mlfbsd@ci0.org> To: Guillaume Ballet <gballet@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: locore.S question Message-ID: <20090331230945.GA8584@ci0.org> In-Reply-To: <fd183dc60903250706y26d8f7eeu1f608ace54c8b813@mail.gmail.com> References: <fd183dc60903250706y26d8f7eeu1f608ace54c8b813@mail.gmail.com>
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On Wed, Mar 25, 2009 at 03:06:49PM +0100, Guillaume Ballet wrote: > Hello list, > Hi Guillaume, > I'm working on a FreeBSD port for the BeagleBoard. I'm starting the > kernel with u-boot and wrote my own small loader for this purpose. > That loader puts the kernel at 0x81000000 (physical address, since the > MMU is disabled at this stage). > Nice to hear you're working on that port :) > In locore.S, however, there is the following piece of code that is > executed before the MMU is disabled: > > 112 adr r7, Lunmapped > 113 bic r7, r7, #0xff000000 > 114 orr r7, r7, #PHYSADDR > > (snip, disabling MMU) > > 129 mov pc, r7 > > Since PHYSADDR is set to 0x80000000 (physical start of RAM), then r7 > is set to 0x80000000 + offset(Lunmapped) instead of 0x81000000 + > offset(Lunmapped). Of course it crashes. > > Now, bypassing the problem is relatively easy, but still I was > wondering why it is 0xff000000 instead of 0xf0000000 on line 113? > Honestly, I may have had a reason at some point, but can't remember which. So I went ahead and just committed the change, I doubt it will be a problem. Thanks for working on this ! Olivier
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