Date: Sat, 5 May 2001 14:13:24 -0500 (CDT) From: Rohit Rakshe <rakshe@cs.umn.edu> To: <freebsd-hackers@FreeBSD.ORG> Subject: FPU exception, kernel panic Message-ID: <Pine.GSO.4.31.0105051400070.16637-100000@mercury.cs.umn.edu> In-Reply-To: <20010505195859.A383@cds220.halls.umist.ac.uk>
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Hi !
I modified some TCP and UDP code in FreeBSD 4.1 and suddenly started
getting (almost repeatable) kernel panics. This is how it looks like
from remote gdb:
(kgdb) bt
#0 0xc0192e58 in panic (fmt=0xc035c076 "npxintr from nowhere") at
../../kern/kern_shutdown.c:550
#1 0xc0303c6c in npx_intr (dummy=0x0) at ../../i386/isa/npx.c:721
#2 0xc02e1052 in Xfpu ()
#3 0xc019824d in softclock () at ../../kern/kern_timeout.c:131
.
.
.
(kgdb) list
126 } else {
127 c->c_flags =
128 (c->c_flags &
~CALLOUT_PENDING);
129 }
130 splx(s);
131 c_func(c_arg);
132 s = splhigh();
133 steps = 0;
134 c = nextsoftcheck;
135 }
.
.
.
(kgdb)
#1 0xc0303c6c in npx_intr (dummy=0x0) at ../../i386/isa/npx.c:721
721 panic("npxintr from nowhere");
(kgdb) p npxproc
$5 = 0
(kgdb) p npx_exists
$6 = 1 '\001'
.
.
.
(kgdb) info all-registers
eax 0x12 18
ecx 0xc03a60a0 -1069916000
edx 0x400000 4194304
ebx 0xcbc56540 -876255936
esp 0xc0361354 0xc0361354
ebp 0xc0361410 0xc0361410
esi 0x400000 4194304
edi 0x400000 4194304
eip 0xc019824d 0xc019824d
eflags 0x346 838
cs 0x8 8
ss 0x10 16
ds 0x400010 4194320
es 0x10 16
fs 0x0 0
gs 0x0 0
(kgdb) info float
status 0xc8f5: exceptions: INVALID DIVZ UNDERF LOS FPSTACK; flags: 1000;
top 1
control 0x6620: compute to 53 bits; round DOWN; mask: LOS;
warning: reserved bits on: 0x6000
last instruction: opcode 0x2825; pc 0x71a4:0x2824c316; operand
0xf800:0x8176640
regno tag msb lsb value
%st(7) valid 0000000008179a802825 Denormal (0 as a double)
%st(6) valid 71a42824c31600000000 Unnormal (NaN)
%st(5) valid 08176640282571a42824 Unnormal (NaN)
%st(4) valid c8910818f9380818f800 Unnormal (NaN)
%st(3) valid 282571a42824c316bfbf Unnormal (NaN)
%st(2) valid e82808176620089c3000 Unnormal (NaN)
%st(1) valid 00000032000000010001 Denormal (0 as a double)
%st(0) => valid 0000000000240818f800 Denormal (0 as a double)
So, this means that there was a FPU exception in kernel, right ?
1. The code which I added in kernel does not use any floats. So I am
wondering why this problem should happen at all.
2. pc register in FPU should give address of the instruction which caused
this exception, right ?
3. If yes, how do I translate this 48 bit address in a linear address
which gdb can understand ?
Thanks for help !
- Rohit
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