From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (qmailr@mailserv2.iuinc.com [206.245.164.55]) by puffin.external.hp.com (8.8.7/8.8.7) with SMTP id QAA21943 for ; Mon, 15 Nov 1999 16:13:11 -0700 Sender: frowand@cup.hp.com Message-ID: <383093DE.A8B73CE4@hp.com> Date: Mon, 15 Nov 1999 15:14:38 -0800 From: Frank Rowand Reply-To: frowand@cup.hp.com MIME-Version: 1.0 To: Philipp Rumpf , parisc-linux@thepuffingroup.com CC: Alex deVries Subject: Re: [parisc-linux] depi? References: <199911150736.XAA14959@opus.allegro.com> <19991115092549.G30917@mathe.stud.uni-erlangen.de> Content-Type: text/plain; charset=us-ascii List-ID: Philipp Rumpf wrote: > > > > ; First order of business is to adjust some pointers > > > depi 3,1,2,%arg0 ; phys->virt(free mem ptr) > > > depi 3,1,2, %sp ; phys->virt SP > > > depi 3,1,2, %dp ; p2v DP > > > > DEPI is "Deposite Immediate". depi 3,1,2, %arg0 > > drops the value 3 into the upper 2 bits of register arg0. > > > > IIRC, it's: DEPI immediate_value, right_most_bit#, #bits, target_register > > > > But...strange code. It's setting the upper 2 bits of R26, R30, and R27. > > The way physical memory is mapped to kernel virtual memory is (with exceptions): > > physical address P is mapped at virtual address P + PAGE_OFFSET. > > PAGE_OFFSET currently is 0xc000 0000 which was a bad value and will be changed > to either 0x8000 0000 or 0xe000 0000 in the near future. This is one of the > reasons you should use tophys and tovirt instead of doing the depi by hand. < stuff deleted > This is just one of several recent messages dealing with the issues caused by locating the kernel at virtual address 0xc0000000 instead of 0x00000000. I still don't understand why the kernel can't be at zero, even though several people have tried to explain it to me. Can anyone provide a clear explanation? Thanks! -Frank