Setting a dump device from db> ?

[Alan Somers]

On Thu, Dec 22, 2016 at 12:26 AM, Rodney W. Grimes
<freebsd-rwg at pdx.rh.cn85.dnsmgr.net> wrote:
>> On Mon, Dec 19, 2016 at 02:16:25PM -0700, Alan Somers wrote:
>> > Is it possible to set a dump device from loader.conf or from the db>
>> > prompt?  I'm trying to investigate a panic in mpr(4), but I can only
>> > reproduce it during the boot, before rc(8) has set my dump device.  It
>> > looks like ada(4) initializes before mpr(4), so I should be able to
>> > dump to an ada device, if only I can figure out how.  If not, I
>> > suppose I'll have to try gdb over firewire.
>>
>> You can set "dumpdev=ada0p1" or so in loader.conf. See g_dev_init() and
>> init_dumpdev(). This should probably be documented in loader.conf(5).
>
> Please review and if OK commit
>
> Index: sys/boot/forth/loader.conf
> ===================================================================
> --- sys/boot/forth/loader.conf  (revision 310132)
> +++ sys/boot/forth/loader.conf  (working copy)
> @@ -101,6 +101,7 @@
>  #prompt="\\${interpret}"       # Set the command prompt
>  #root_disk_unit="0"            # Force the root disk unit number
>  #rootdev="disk1s1a"            # Set the root filesystem
> +#dumpdev="disk1s1b"            # Set a dump device early on for crashes during boot
>  #tftp.blksize="1428"           # Set the RFC 2348 TFTP block size.
>                                 # If the TFTP server does not support RFC 2348,
>                                 # the block size is set to 512.  If the value
> --
> Rod Grimes                                                 rgrimes at freebsd.org

rgrimes: done
markj: Thanks for the suggestion.  Unfortunately, it doesn't work in
this case, probably because geom hasn't started yet.  I'll do what I
can with online debugging.

-Alan