[Crash-utility] linux_banner has garbage

[Dave Anderson]

----- Original Message -----
> 
> 
> ----- Original Message -----
> > Hello,
> > 
> > We have a CoreOS VM(46 vCPU, 60GB RAM) freeze issue and hoping to find out
> > what is going on in it at the time of freeze. When the VM froze, we have no
> > access to it via ssh and ping works sometimes but not always. So, we
> > suspended the VM which created vmem and vmss files.
> > 
> > Since this is a CoreOS VM, I have used toolbox to install and run crash.
> > When trying to read these files using crash utility, I'm getting the below
> > message:
> > 
> > 
> > 
> > <read_vmware_vmss: addr: ffffffff81c00100 paddr: 1c00100 cnt: 8>
> > 
> > <readmem: ffffffff81c00100, KVADDR, "read_string characters", 1499,
> > (ROE|Q),
> > 7ffcf595cd70>
> > 
> > <read_vmware_vmss: addr: ffffffff81c00100 paddr: 1c00100 cnt: 1499>
> > 
> > linux_banner:
> > 
> > -ش????kB??C???Ã͞}&k?Xb?8/?ν?fF??&v;?Š???? ??
> 
> It would have been helpful to see the full crash -d# log, but I'm presuming
> that the utsname data and the cpus_[possible/present/online/active]_mask
> output
> that gets displayed just before the linux_banner output are also nonsensical?
> 
> Typically this kind of problem is because phys_base cannot be determined,
> or if KASLR is enabled, the KASLR offset cannot be determined.  Those two
> items are encoded into the dumpfile header for kdump dumpfiles, but there
> is no such information in a vmms dumpfile header.
> 
> Can you run crash live on the machine?  You can see whether the phys_base
> and KASLR offset are non-zero on the live system by entering:
> 
>   crash> help -m | grep phys_base
>                   phys_base: 129800000
>   crash> help -k | grep relocate
>         relocate: ffffffffcf400000  (KASLR offset: 30c00000 / 780MB)
>   crash>
> 
> If relocate is 0 (KASLR not enabled), then the phys_base value can
> be applied to your vmcore by entering, for example, "--machdep
> phys_base=780m"
> on the crash command line (using your phys_base).  

Sorry, my mistake -- it would be "--machdep phys_base=129800000". 

Dave