Date: Fri, 16 Apr 2004 10:41:22 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: "Alan L. Cox" <alc@imimic.com> Cc: Kris Kennaway <kris@obsecurity.org> Subject: Re: Another alpha panic Message-ID: <16511.61586.123216.627307@grasshopper.cs.duke.edu> In-Reply-To: <407F775D.7020908@imimic.com> 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> <407F775D.7020908@imimic.com>
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Alan L. Cox writes: > 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. > Is it really pointing into never-never land? The original panic was that pmap_emulate_reference() was complaining that the page was not managed.. The physical address 0xb0a0000 is not totally unreasonable, and would sit around ~176MB into memory. The fact that the trap was an ALPHA_MMCSR_FOW, and not an ALPHA_MMCSR_INVALTRANS or ALPHA_MMCSR_ACCESS makes me think that the kva was also good... I was wondering if there might be some more insidious pmap corruption happening. Or at least why a page in the middle of memory is not marked as managed. Drew
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