Debugging kernel cores without a stack

[Joshua Isom]

Backtrace gives me an error.  The only backtrace I'm given is from the 
kernel message while it's crashing.  After it's crashed I'm getting nothing.

[jri:~] root# kgdb -q /boot/kernel/kernel /var/crash/vmcore.30
Reading symbols from /boot/kernel/zfs.ko...Reading symbols from 
/boot/kernel/zfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/zfs.ko
Reading symbols from /boot/kernel/opensolaris.ko...Reading symbols from 
/boot/kernel/opensolaris.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/opensolaris.ko
Reading symbols from /boot/kernel/geom_mirror.ko...Reading symbols from 
/boot/kernel/geom_mirror.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/geom_mirror.ko
Reading symbols from /boot/kernel/if_ath.ko...Reading symbols from 
/boot/kernel/if_ath.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/if_ath.ko
Reading symbols from /boot/kernel/amdtemp.ko...Reading symbols from 
/boot/kernel/amdtemp.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/amdtemp.ko
Reading symbols from /boot/kernel/if_ath_pci.ko...Reading symbols from 
/boot/kernel/if_ath_pci.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/if_ath_pci.ko
Reading symbols from /boot/kernel/ums.ko...Reading symbols from 
/boot/kernel/ums.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/ums.ko
Reading symbols from /boot/kernel/ulpt.ko...Reading symbols from 
/boot/kernel/ulpt.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/ulpt.ko
Reading symbols from /boot/kernel/uhid.ko...Reading symbols from 
/boot/kernel/uhid.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/uhid.ko
Reading symbols from /boot/kernel/ipfw.ko...Reading symbols from 
/boot/kernel/ipfw.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/ipfw.ko
Reading symbols from /boot/kernel/nullfs.ko...Reading symbols from 
/boot/kernel/nullfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/nullfs.ko
kgdb: kvm_read: invalid address (0x354541500000000)
#0  0x0000000000000000 in ?? ()
(kgdb) backtrace
#0  0x0000000000000000 in ?? ()
Cannot access memory at address 0x0
(kgdb)


On 3/24/2013 12:44 PM, Adrian Chadd wrote:
> You need to use 'bt' to see the stack trace, then 'frame X' to go into
> that frame.
>
> Post 'bt' output and I'll show you what you're looking for.
>
>
>
>
> Adrian
>