E420R stuck in endless boot loop. ...Error occurred in module genunix due to a null pointer dereference

There have been situations where E420R's get stuck in an endless loop of booting to a certain point and then rebooting. the following error is reported (CPU number, thread, etc may vary):

  panic cpu 2  thread= 30001908880:bad trap: type 31 rp=2a1002fc40 add=2cmmu_fs r=0
  occured in module genunix due to a null pointer dereference                  

In one case, this problem occurred after loading the recommended patch cluster for Solaris 8 in multi-user mode. The boot prom was not up to date. To resolve the endless booting loop, the following steps were taken:

1.  Boot from cdrom
2.  Mount root and /var and /usr to /a /a/var /a/usr
3.  chroot /a (if chroot fails, please see SRDB 26490)
4.  patchrm 108528-08 (or latest revision)
5.  reboot
6.  Add OBP patch for 420R  109082-04 (or latest revision)
7.  reboot again
8.  Ensure that the system is running
9.  Add the kernel patch once again (in single user mode!)
                  

Applies to Solaris 8

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