Date: Mon, 19 Jun 2000 16:40:44 -0500 (CDT) From: Kevin Day <toasty@dragondata.com> To: hackers@freebsd.org Subject: Unknown exception/trap confusion Message-ID: <200006192140.QAA13755@celery.dragondata.com>
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Ok, I've got a system that seems to spuriously "panic: unknown/reserved
trap". In trying to figure out which exception got triggered, I did a
backtrace...
(kgdb) bt
#0 boot (howto=256) at ../../kern/kern_shutdown.c:303
#1 0xc016a355 in panic (fmt=0xc02c58d9 "unknown/reserved trap") at ../../kern/kern_shutdown.c:553
#2 0xc02821ea in trap_fatal (frame=0xd907ebfc, eva=0) at ../../i386/i386/trap.c:929
#3 0xc0281b37 in trap (frame={tf_fs = 24, tf_es = 65552, tf_ds = -653852656, tf_edi = 4, tf_esi = -866895904,
tf_ebp = -653792120, tf_isp = -653792216, tf_ebx = -1066888788, tf_edx = -1070536316, tf_ecx = 16777218,
tf_eax = 1862615194, tf_trapno = 29, tf_err = 0, tf_eip = -1071493032, tf_cs = 8, tf_eflags = 518, tf_esp = -1071172139,
tf_ss = -1042059264}) at ../../i386/i386/trap.c:589
#4 0xc0225058 in ti_intr (xsc=0xc0000) at ../../pci/if_ti.c:1938
#5 0xc027c11f in smp_invltlb () at machine/mpapic.h:104
#6 0xc027dd42 in pmap_qremove (va=3443085312, count=4) at ../../i386/i386/pmap.c:818
#7 0xc01918fc in vfs_vmio_release (bp=0xcc5437e0) at ../../kern/vfs_bio.c:1270
#8 0xc0191dfe in getnewbuf (slpflag=0, slptimeo=0, size=16384, maxsize=16384) at ../../kern/vfs_bio.c:1551
#9 0xc0192a01 in getblk (vp=0xd9928000, blkno=2, size=16384, slpflag=0, slptimeo=0) at ../../kern/vfs_bio.c:2195
#10 0xc019506e in cluster_rbuild (vp=0xd9928000, filesize=136472, lbn=1, blkno=189541632, size=16384, run=2, fbp=0x0)
at ../../kern/vfs_cluster.c:391
#11 0xc0194c72 in cluster_read (vp=0xd9928000, filesize=136472, lblkno=1, size=16384, cred=0x0, totread=2820, seqcount=2,
bpp=0xd907ee68) at ../../kern/vfs_cluster.c:229
#12 0xc0238666 in ffs_read (ap=0xd907ee8c) at ../../ufs/ufs/ufs_readwrite.c:252
#13 0xc01a00fc in vn_read (fp=0xc2dacb80, uio=0xd907eed8, cred=0xc32e1d00, flags=0, p=0xd6952440) at vnode_if.h:334
#14 0xc017a889 in dofileread (p=0xd6952440, fp=0xc2dacb80, fd=18, buf=0x816f035, nbyte=2820, offset=-1, flags=0)
at ../../sys/file.h:141
#15 0xc017a78f in read (p=0xd6952440, uap=0xd907ef80) at ../../kern/sys_generic.c:111
#16 0xc0282511 in syscall2 (frame={tf_fs = 47, tf_es = 47, tf_ds = 135594031, tf_edi = 0, tf_esi = 0, tf_ebp = 0,
tf_isp = -653791276, tf_ebx = 140614144, tf_edx = 140614144, tf_ecx = 140614144, tf_eax = 3, tf_trapno = 7, tf_err = 2,
tf_eip = 673047244, tf_cs = 31, tf_eflags = 663, tf_esp = -1077937696, tf_ss = 47}) at ../../i386/i386/trap.c:1126
In frame 3, trap is getting called with tf_trapno equal to 29... Which
according to machine/trap.h is:
#define T_RESERVED 29 /* reserved (unknown) */
It's getting set that way from the idt vector in exception.s:
IDTVEC(rsvd)
pushl $0; TRAP(T_RESERVED)
because all exceptions that aren't specifically mapped to a idt vector are
pointed to IDTVEC(rsvd) in machdep.c:
for (x = 0; x < NIDT; x++)
setidt(x, &IDTVEC(rsvd), SDT_SYS386TGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
My question is... How am I going to tell which exception is actually getting
called? Is it completely unreasonable to have the rsvd idt vector call trap
with the trap value + MAX_TRAP_MSG or some other constant, so that trap()
can tell what the real exception was?
Without knowing which exception really got called, troubleshooting this is
more difficult, but... I can't quite figure out what's going on in ti_intr
that could cause an exeception... It appears that ti_intr is just getting
things off the stack when it crashes:
#4 0xc0225058 in ti_intr (xsc=0xc0000) at ../../pci/if_ti.c:1938
1938 }
(kgdb) list
1933
1934 if (cur_tx != NULL)
1935 ifp->if_flags &= ~IFF_OACTIVE;
1936
1937 return;
1938 }
1939
1940 static void ti_intr(xsc)
1941 void *xsc;
1942 {
(kgdb) disassemble
Dump of assembler code for function ti_intr:
0xc0225058 <ti_intr>: push %ebp
0xc0225059 <ti_intr+1>: mov %esp,%ebp
0xc022505b <ti_intr+3>: push %esi
0xc022505c <ti_intr+4>: push %ebx
0xc022505d <ti_intr+5>: mov 0x8(%ebp),%esi
0xc0225060 <ti_intr+8>: mov %esi,%ebx
(kgdb) info frame
Stack level 4, frame at 0xd907ec88:
eip = 0xc0225058 in ti_intr (../../pci/if_ti.c:1938); saved eip 0xc027c11f
called by frame at 0xd907ec9c, caller of frame at 0xd907ebf4
source language c.
Arglist at 0xd907ec88, args:
Locals at 0xd907ec88, Previous frame's sp is 0x0
Saved registers:
ebx at 0xd907ec80, ebp at 0xd907ec88, esi at 0xd907ec84, eip at 0xd907ec8c
(kgdb) info registers
eax 0x0 0
ecx 0x0 0
edx 0x0 0
ebx 0x6f05409a 1862615194
esp 0xd907eb58 0xd907eb58
ebp 0xd907ec88 0xd907ec88
esi 0xcc5437e0 -866895904
edi 0x4 4
eip 0xc02701ab 0xc02701ab
eflags 0x0 0
cs 0x0 0
ss 0x0 0
ds 0x0 0
es 0x0 0
fs cannot read u area ptr for proc at 0
I'm a bit over my head here, can anyone offer any pointers on what to do
now?
-- Kevin
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