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-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
-instruction 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.