Date: Mon, 15 Nov 1999 12:58:30 -0500 (EST) From: Thomas David Rivers <rivers@dignus.com> To: FreeBSD-gnats-submit@freebsd.org Subject: kern/14900: 3.3-RELEASE panic in pmap_pte_quick() Message-ID: <199911151758.MAA02091@lakes.dignus.com>
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>Number: 14900
>Category: kern
>Synopsis: 3.3-RELEASE panic in pmap_pte_quick()
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Nov 15 10:00:00 PST 1999
>Closed-Date:
>Last-Modified:
>Originator: Thomas David Rivers
>Release: FreeBSD 3.3-RELEASE i386
>Organization:
Dignus, LLC
>Environment:
3.3-RELEASE running on a P200, w/ 64Meg memory, AHA2940.
>Description:
I have seen, every-now-and-then, panics with 3.3-RELEASE.
After observing when these occur, I was able to put together
a sequence of programs to run which will cause the panic.
My debugging of the kernel indicates that pmap_pte_quick()
is being passed a bad `pmap' parm. Although, I'm unable
to take it from there.
Here's the traceback:
pmap_pte_quick()+12
pmap_ts_referenced()
vm_pageout_page_stats()
vm_pageout()
kproc_start()
fork_trampoline()
The particular instruction which causes the panic is:
movl 0(%edx,%eax,4),%ecx
which comes from the source line:
if (pde = (unsigned) pmap->pm_pdir[va >> PDRSHIFT]) {
this is the instruction to reference the pm_pdir array. %edx
should contain a correct value for pmap->pm_pdir, but contains
trash (or, at least an address outside of the kernel's address
table.) %edx is loaded from the in-coming `pmap' parm.
>How-To-Repeat:
I have the reproduction - unfortunately it involves running
a purchase program, so I'm not at liberty to hand it out.
I will be happy to test any potential fixes.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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