Machine related makefile symbols definition

Initial definitions 
------------------- 

The following symbol definitions rely on you knowing the translation that 
__virt_to_phys() does for your machine. This macro converts the passed 
virtual address to a physical address. Normally, it is simply: 

        phys = virt - PAGE_OFFSET + PHYS_OFFSET 


Decompressor Symbols 
-------------------- 

ZTEXTADDR 
    Start address of decompressor. There's no point in talking about 
    virtual or physical addresses here, since the MMU will be off at 
    the time when you call the decompressor code. You normally call 
    the kernel at this address to start it booting. This doesn't have 
    to be located in RAM, it can be in flash or other read-only or 
    read-write addressable medium. 

ZBSSADDR 
    Start address of zero-initialised work area for the decompressor. 
    This must be pointing at RAM. The decompressor will zero initialise 
    this for you. Again, the MMU will be off. 

ZRELADDR 
    This is the address where the decompressed kernel will be written, 
    and eventually executed. The following constraint must be valid: 

        __virt_to_phys(TEXTADDR) == ZRELADDR 

    The initial part of the kernel is carefully coded to be position 
    independent. 

INITRD_PHYS 
    Physical address to place the initial RAM disk. Only relevant if 
    you are using the bootpImage stuff (which only works on the old 
    struct param_struct). 

INITRD_VIRT 
    Virtual address of the initial RAM disk. The following constraint 
    must be valid: 

        __virt_to_phys(INITRD_VIRT) == INITRD_PHYS 

PARAMS_PHYS 
    Physical address of the struct param_struct or tag list, giving the 
    kernel various parameters about its execution environment. 


Kernel Symbols 
-------------- 

PHYS_OFFSET 
    Physical start address of the first bank of RAM. 

PAGE_OFFSET 
    Virtual start address of the first bank of RAM. During the kernel 
    boot phase, virtual address PAGE_OFFSET will be mapped to physical 
    address PHYS_OFFSET, along with any other mappings you supply. 
    This should be the same value as TASK_SIZE. 

TASK_SIZE 
    The maximum size of a user process in bytes. Since user space 
    always starts at zero, this is the maximum address that a user 
    process can access+1. The user space stack grows down from this 
    address. 

    Any virtual address below TASK_SIZE is deemed to be user process 
    area, and therefore managed dynamically on a process by process 
    basis by the kernel. I'll call this the user segment. 

    Anything above TASK_SIZE is common to all processes. I'll call 
    this the kernel segment. 

    (In other words, you can't put IO mappings below TASK_SIZE, and 
    hence PAGE_OFFSET). 

TEXTADDR 
    Virtual start address of kernel, normally PAGE_OFFSET + 0x8000. 
    This is where the kernel image ends up. With the latest kernels, 
    it must be located at 32768 bytes into a 128MB region. Previous 
    kernels placed a restriction of 256MB here. 

DATAADDR 
    Virtual address for the kernel data segment. Must not be defined 
    when using the decompressor. 

VMALLOC_START 
VMALLOC_END 
    Virtual addresses bounding the vmalloc() area. There must not be 
    any static mappings in this area; vmalloc will overwrite them. 
    The addresses must also be in the kernel segment (see above). 
    Normally, the vmalloc() area starts VMALLOC_OFFSET bytes above the 
    last virtual RAM address (found using variable high_memory). 

VMALLOC_OFFSET 
    Offset normally incorporated into VMALLOC_START to provide a hole 
    between virtual RAM and the vmalloc area. We do this to allow 
    out of bounds memory accesses (eg, something writing off the end 
    of the mapped memory map) to be caught. Normally set to 8MB. 

Architecture Specific Macros 
---------------------------- 

BOOT_MEM(pram,pio,vio) 
    `pram' specifies the physical start address of RAM. Must always 
    be present, and should be the same as PHYS_OFFSET. 

    `pio' is the physical address of an 8MB region containing IO for 
    use with the debugging macros in arch/arm/kernel/debug-armv.S. 

    `vio' is the virtual address of the 8MB debugging region. 

    It is expected that the debugging region will be re-initialised 
    by the architecture specific code later in the code (via the 
    MAPIO function). 

BOOT_PARAMS 
    Same as, and see PARAMS_PHYS. 

FIXUP(func) 
    Machine specific fixups, run before memory subsystems have been 
    initialised. 

MAPIO(func) 
    Machine specific function to map IO areas (including the debug 
    region above). 

INITIRQ(func) 
    Machine specific function to initialise interrupts.