Date: Wed, 06 Mar 2002 00:41:55 -0500 From: Mike Tancsa <mike@sentex.net> To: Harry Newton <harry_newton@telinco.co.uk> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: reproducible kernel panic Message-ID: <5.1.0.14.0.20020306003951.04fb0328@192.168.0.12> In-Reply-To: <867koq7gp7.fsf@basilisk.locus>
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Hmmm.... Is there any work around to this ? I guess there is no way to
limit this via login.conf ?
---Mike
At 11:11 PM 3/5/2002 +0000, Harry Newton wrote:
>With this:
>
> #!/usr/local/bin/python2.2
>
> import mmap
> m = mmap.mmap(-1,256,mmap.MAP_ANON)
>
> m = 1
>
>I can panic the kernel:
>
> trap 12: page fault while in kernel mode --- supervisor read, page not
> present
>
> Stopped at: vm_map_clean+0x1ee: cmpl $0,0x40(%edi)
>
>I dug around a bit with the debugger, and found the fault to lie in:
>
> /usr/src/sys/vm/vm_map.c : 1749
>
>here's the right bit ( reformatted to fit on this page )
>
>/*
> * Note that there is absolutely no sense in writing out
> * anonymous objects, so we track down the vnode object
> * to write out.
> * We invalidate (remove) all pages from the address space
> * anyway, for semantic correctness.
> */
> while (object->backing_object) {
> object = object->backing_object;
> offset += object->backing_object_offset;
> if (object->size < OFF_TO_IDX( offset + size))
> size = IDX_TO_OFF(object->size) - offset;
> }
>
>But: I can't be much more use, apart from noting that:
>
> size = 4096
> offset = -3621126458136592384
> object = 0x0
> object->backing_object --- can't access memory at 0x40
>
>I take it that messing round with anonymous maps shouldn't panic the
>kernel like this.
>
>Q. + Should I submit a PR ?
> + can I supply anymore information ?
>
>
>( It was mis-keying that caused the first panic, and I've reduced it
>to the above lines of Python: I didn't set out with the above ! )
>
>- Harry
>
>--
>Harry Newton
>harry_newton at telinco.co.uk
>www.gaudeamus.telinco.co.uk/html/gpg.html
>
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Sentex Communications, mike@sentex.net
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