Date: Fri, 20 Feb 2004 10:44:22 -0500 From: Eric van Gyzen <vangyzen@stat.duke.edu> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-current@freebsd.org Subject: Re: panic: arithmetic trap in fpurstor() in sys/i386/isa/npx.c Message-ID: <200402201044.22152.vangyzen@stat.duke.edu> In-Reply-To: <20040220171712.D4279@gamplex.bde.org> References: <200402191542.54594.vangyzen@stat.duke.edu> <20040220171712.D4279@gamplex.bde.org>
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Bruce Evans wrote:
> On Thu, 19 Feb 2004, Eric van Gyzen wrote:
> > I can reliably panic 5.2-RELEASE GENERIC running on three different AMD
> > Athlon CPUs with:
> >
> > # echo 'q()' | R --no-save
> >
> > R is ports/math/R-letter, and q() just tells R to quit. This does not
> > happen on an AthlonMP or P3 running the same kernel. It did not happen
> > on the same three Athlon machines while running 5.1-RELEASE. Some simple
> > gdb debugging follows. If you need more info, please ask; I don't debug
> > the kernel very often, so I'm not sure what to provide. :-/
>
> Try backing out rev.1.216 of vm_machdep.c. I don't see exactly how this
> commit could cause the problem, but it is the only related thing that has
> changed since 5.1, and the first part of it has several bugs (it is a
> layering violation and is missing explicit disabling of interrupts).
I'll try that and reply later. (For now, I have to do my /real/ job...)
> > panic: arithmetic trap
> > ...
> > (kgdb) list *0xc07e07b4
> > 0xc07e07b4 is in fpurstor (/usr/src/sys/i386/isa/npx.c:986).
> > [snip]
> >
> > (kgdb) list 976,987
> > 976 static void
> > 977 fpurstor(addr)
> > 978 union savefpu *addr;
> > 979 {
> > 980
> > 981 #ifdef CPU_ENABLE_SSE
> > 982 if (cpu_fxsr)
> > 983 fxrstor(addr);
> > 984 else
> > 985 #endif
> > 986 frstor(addr);
> > 987 }
>
> frstror() can only cause an arithmetic trap on broken CPUs. I doubt
> that Athlons are that broken, so this trap is mysterious. frstor()
> doesn't even trap for plain i386's; it may cause a bogus IRQ13 which
> the kernel has to be careful not to turn into an arithmetic trap.
>
> Please report the value and contents of addr (about 108 bytes of it
> in hex).
When I try to examine addr, gdb tells me 'No symbol "addr" in current
context.' So, I switched to its caller and...
#6 0xc07e05a1 in npxdna () at /build/src/sys/i386/isa/npx.c:840
840 fpurstor(&pcb->pcb_save);
(kgdb) print &pcb->pcb_save
$4 = (union savefpu *) 0x40
(kgdb) print pcb
$5 = (struct pcb *) 0x0
Ummm...that doesn't look quite right. Please tell me if I'm missing
something.
Eric
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