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[174.88.78.8]) by smtp.gmail.com with ESMTPSA id j5-v6sm27738513pff.139.2018.09.19.14.02.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 19 Sep 2018 14:02:14 -0700 (PDT) Sender: Mark Johnston Date: Wed, 19 Sep 2018 17:02:11 -0400 From: Mark Johnston To: Steve Kargl Cc: freebsd-current@freebsd.org Subject: Re: ALPHA4 panic in VM Message-ID: <20180919210211.GC99168@raichu> References: <20180919200152.GA1164@troutmask.apl.washington.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180919200152.GA1164@troutmask.apl.washington.edu> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Sep 2018 21:02:17 -0000 On Wed, Sep 19, 2018 at 01:01:52PM -0700, Steve Kargl wrote: > I have the kernel and core file if more information is needed. > > % cat info.2 > Dump header from device: /dev/ada0p3 Architecture: amd64 > Architecture Version: 2 > Dump Length: 2348281856 > Blocksize: 512 > Compression: none > Dumptime: Wed Sep 19 12:29:59 2018 > Hostname: troutmask.apl.washington.edu > Magic: FreeBSD Kernel Dump > Version String: FreeBSD 12.0-ALPHA4 #0 r338505: Thu Sep 6 13:45:34 PDT 2018 > kargl@troutmask.apl.washington.edu:/usr/obj/usr/src/amd64.amd64/sys/SPEW > Panic String: page fault > Dump Parity: 2676008548 > Bounds: 2 > Dump Status: good > > % more core.txt.2 > Fatal trap 12: page fault while in kernel mode > cpuid = 1; apic id = 11 > fault virtual address = 0xffffb8000719a428 This seems to be the result of a bit-flip. cred is 0xffffb8000719a400, which is almost but not quite in the direct map. In particular we have: (kgdb) frame 10 #10 0xffffffff8083e07d in vm_object_destroy (object=) at /usr/src/sys/vm/vm_object.c:703 703 swap_release_by_cred(object->charge, object->cred); (kgdb) p object $8 = (kgdb) p *(vm_object_t)$r13 $9 = { ... cred = 0xffffb8000719a400, charge = 28672, umtx_data = 0x0 } (kgdb) p *(struct ucred *)0xfffff8000719a400 $10 = { cr_ref = 5737, cr_uid = 1001, cr_ruid = 1001, cr_svuid = 1001, cr_ngroups = 7, cr_rgid = 1001, cr_svgid = 1001, cr_uidinfo = 0xfffff80007285500, cr_ruidinfo = 0xfffff80007285500, cr_prison = 0xffffffff80a9de10 , ... That is, flipping one of the bits in the fault address leads me to a valid ucred. This could in principle be the result of a software bug, but I'd be more inclined to suspect the hardware.