okay, here are some hints for debugging the lower-level parts of
  linux/parisc.
  
  
  1. Absolute addresses
  
  A lot of the assembly code currently runs in real mode, which means
  absolute addresses are used instead of virtual addresses as in the
  rest of the kernel.  To translate an absolute address to a virtual
  address you can lookup in System.map, add __PAGE_OFFSET (0x10000000
  currently).
  
  
  2. HPMCs
  
  When real-mode code tries to access non-existent memory, you'll get
  an HPMC instead of a kernel oops.  To debug an HPMC, try to find
  the System Responder/Requestor addresses.  The System Requestor
  address should match (one of the) processor HPAs (high addresses in
  the I/O range); the System Responder address is the address real-mode
  code tried to access.
  
  Typical values for the System Responder address are addresses larger
  than __PAGE_OFFSET (0x10000000) which mean a virtual address didn't
  get translated to a physical address before real-mode code tried to
  access it.
  
  
  3. Q bit fun
  
  Certain, very critical code has to clear the Q bit in the PSW.  What
  happens when the Q bit is cleared is the CPU does not update the
  registers interruption handlers read to find out where the machine
  was interrupted - so if you get an interruption between the instruction
  that clears the Q bit and the RFI that sets it again you don't know
  where exactly it happened.  If you're lucky the IAOQ will point to the
  instrucion that cleared the Q bit, if you're not it points anywhere
  at all.  Usually Q bit problems will show themselves in unexplainable
  system hangs or running off the end of physical memory.