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Date:      Fri, 16 Apr 2004 01:04:13 -0500
From:      "Alan L. Cox" <alc@imimic.com>
To:        Kris Kennaway <kris@obsecurity.org>
Cc:        Andrew Gallatin <gallatin@cs.duke.edu>
Subject:   Re: Another alpha panic
Message-ID:  <407F775D.7020908@imimic.com>
In-Reply-To: <20040416054804.GA79165@xor.obsecurity.org>
References:  <20040411093343.GA89809@xor.obsecurity.org> <200404132236.20792.jhb@FreeBSD.org> <16509.42895.49213.222503@grasshopper.cs.duke.edu> <20040416045453.GA78366@xor.obsecurity.org> <407F68BA.6000405@imimic.com> <20040416053930.GA78940@xor.obsecurity.org> <20040416054340.GZ238@cs.rice.edu> <20040416054804.GA79165@xor.obsecurity.org>

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Kris Kennaway wrote:
> 
> Dump of assembler code for function pmap_activate:
> 0xfffffc00005cf0b0 <pmap_activate>:     ldah    gp,14(t12)
...
> 0xfffffc00005cf160 <pmap_activate+176>: srl     t1,0xd,t1
> 0xfffffc00005cf164 <pmap_activate+180>: stq     t1,16(t2)
...
I believe that the shift right is the "... >> PAGE_SHIFT" in

     td->td_pcb->pcb_hw.apcb_ptbr =
         ALPHA_K0SEG_TO_PHYS((vm_offset_t) pmap->pm_lev1) >> PAGE_SHIFT;

and the store quad is dereferencing "td->td_pcb".  In other words, 
td->td_pcb points to never-never land.

Alan



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