Date: Wed, 24 May 2000 20:11:31 +0200 (CEST) From: Thomas Faehnle <tf@wurbl.wn.bawue.de> To: freebsd-hackers@freebsd.org Subject: Need help debugging a crash (PR kern/18685) Message-ID: <E12ufif-00035U-00@wurbl.bk.int>
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Hi,
I'm trying to assist in debugging the crash reported as kern/18685--
apparently Greg is unable to reproduce the problem on his machine.
The error
| Fatal trap 12: page fault while in kernel mode
| fault virtual address = 0x69666f27
| fault code = supervisor read, page not present
| instruction pointer = 0x8:0xc0158c14
| stack pointer = 0x10:0xc3dd7bf8
| frame pointer = 0x10:0xc3dd7c0c
| code segment = base 0x0, limit 0xfffff, type 0x1b
| = DPL 0, pres 1, def32 1, gran 1
| processor eflags = interrupt enabled, resume, IOPL = 0
| current process = 974 (make)
| interrupt mask = none
| kernel: type 12 trap, code=0
| Stopped at dscheck+0x104: movl 0xb8(%esi),%edx
|
| db> trace
| dscheck(c1413728,c08c6900) at dscheck+0x104
| diskstrategy(c1413728,c0845e80,c1413728,0,c3dd7c4c) at diskstrategy+0xad
| spec_strategy(c3dd7c70,c3dd7c58,c0208f7d,c3dd7c70,c3dd7c8c) at spec_strategy+0x8c
| spec_vnoperate(c3dd7c70,c3dd7c8c,c02089e5,c3dd7c70,c3dd7ce4) at spec_vnoperate+0x15
| ufs_vnoperatespec(c3dd7c70,c3dd7ce4,c1413728,0,c028ae80) at ufs_vnoperatespec+0x15
| ...
occurs at line 198 ("labelsect = lp->d_partitions[LABEL_PART].p_offset;")
of /sys/kern/subr_diskslice.c due to a bogus "struct diskslices" pointer
(the second argument of dscheck(), "ssp").
I can't do a crash dump, since ddb refuses to step past the instruction
that triggered the trap (saying "panic" just repeats the above message).
I can't catch the "ssp" pointer when it gets corrupted either, since
watchpoints don't seem to work in ddb (at least not on kernel memory).
What can I do to help getting this fixed? Suggestions?
Thomas
--
Thomas Faehnle, Am Sommerrain 12, D-71522 Backnang | MIME mail welcome
mail: tf@wurbl.wn.bawue.de * phone: +49 7191 954671 | PGP key available
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