Crash dumps not working correctly for amd64?

[Scott Long]

Sean Chittenden wrote:
> Howdy.  I've got myself an interesting situation.  It seems as though
> amd64 is unable to collect crash dumps via savecore(8).  Has anyone
> else seen this?  From dmesg(1):
> 
> Checking for core dump on /dev/da0s1b ...
> savecore: first and last dump headers disagree on /dev/da0s1b
> Feb 21 12:45:59 host savecore: first and last dump headers disagree on /dev/da0s1b
> savecore: unsaved dumps found but not saved
> 
> ???  sys/amd64/amd64/dump_machdep.c and sys/i386/i386/dump_machdep.c
> are essentially identical.  I'm not familiar enough with these
> innards, but reviewing savecore(8) didn't point out anything obvious.
> I'm dumping onto a twa(4) controller.
> 
> Are there any known workarounds to get this info?  I'm tempted to turn
> off swap in fstab(5) that way the next time the machine comes up after
> a crash, it'll still have the dump in tact and could poke at it as
> time permitted.  Other suggestions?  -sc
> 

Can you modify savecore to dump the headers anyways so they can be 
inspected?

Scott