Re: newfs_msdos and DVD-RAM

Andriy Gapon <avg_at_freebsd.org> wrote:

> on 29/03/2010 23:29 Fabian Keil said the following:
> > Andriy Gapon <avg_at_freebsd.org> wrote:
> >> Thus, clearly, it is a fault of a tool that formatted the media for FAT.
> >> It should have picked correct values, or rejected incorrect values if
> >> those were provided as overrides via command line options.
> > 
> > The kernel still shouldn't panic, though.
> 
> A quick reply to this point only - yes, I completely agree.
> But remember that the panic happened only after the sources were modified :)

It wasn't clear from my message, but I was mainly referring to the
division-by-zero panic mentioned at the beginning of the thread,
for which I posted a work-around in <20100319191133.46fe271c_at_r500.local>.

I think no backtrace has been posted yet, so here's the one
I got with mostly vanilla sources from around 2010-02-14:

Fatal trap 18: integer divide fault while in kernel mode
cpuid = 0; apic id = 00         
instruction pointer     = 0x20:0xffffffff803590b8
stack pointer           = 0x28:0xffffff803e845620
frame pointer           = 0x28:0xffffff803e845790
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 2877 (mount_msdosfs)
panic: from debugger            
cpuid = 0                       
Uptime: 22m14s                  
Dumping 1992 MB (5 chunks)      
  chunk 0: 1MB (155 pages) ... ok
  chunk 1: 1990MB (509345 pages) 1974 [...] 6 ... ok
  chunk 2: 2MB (273 pages) ... ok
  chunk 3: 1MB (184 pages)
[...]
(kgdb) where
#0  doadump () at pcpu.h:223
#1  0xffffffff803babdf in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:416
#2  0xffffffff803bafdc in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:579
#3  0xffffffff801f4eb7 in db_panic (addr=Variable "addr" is not available.
) at /usr/src/sys/ddb/db_command.c:478
#4  0xffffffff801f52c1 in db_command (last_cmdp=0xffffffff808a07c0, cmd_table=Variable "cmd_table" is not available.
) at /usr/src/sys/ddb/db_command.c:445
#5  0xffffffff801f5510 in db_command_loop () at /usr/src/sys/ddb/db_command.c:498
#6  0xffffffff801f7469 in db_trap (type=Variable "type" is not available.
) at /usr/src/sys/ddb/db_main.c:229
#7  0xffffffff803e9945 in kdb_trap (type=18, code=0, tf=0xffffff803e845570) at /usr/src/sys/kern/subr_kdb.c:535
#8  0xffffffff806129fd in trap_fatal (frame=0xffffff803e845570, eva=Variable "eva" is not available.
) at /usr/src/sys/amd64/amd64/trap.c:853
#9  0xffffffff80613252 in trap (frame=0xffffff803e845570) at /usr/src/sys/amd64/amd64/trap.c:647
#10 0xffffffff805fa4a3 in calltrap () at /usr/src/sys/amd64/amd64/exception.S:224
#11 0xffffffff803590b8 in msdosfs_mount (mp=0xffffff003cba25f0) at /usr/src/sys/fs/msdosfs/msdosfs_vfsops.c:610
#12 0xffffffff80436db0 in vfs_donmount (td=Variable "td" is not available.
) at /usr/src/sys/kern/vfs_mount.c:988
#13 0xffffffff804377b3 in nmount (td=0xffffff004a6d03b0, uap=0xffffff803e845bf0) at /usr/src/sys/kern/vfs_mount.c:424
#14 0xffffffff80612e7d in syscall (frame=0xffffff803e845c80) at /usr/src/sys/amd64/amd64/trap.c:1026
#15 0xffffffff805fa781 in Xfast_syscall () at /usr/src/sys/amd64/amd64/exception.S:373
#16 0x00000008007a292c in ?? ()
Previous frame inner to this frame (corrupt stack?)

Fabian