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1=======2Porting3=======4 5Taken from list archive at http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2001-July/004064.html6 7Initial definitions8-------------------9 10The following symbol definitions rely on you knowing the translation that11__virt_to_phys() does for your machine. This macro converts the passed12virtual address to a physical address. Normally, it is simply:13 14 phys = virt - PAGE_OFFSET + PHYS_OFFSET15 16 17Decompressor Symbols18--------------------19 20ZTEXTADDR21 Start address of decompressor. There's no point in talking about22 virtual or physical addresses here, since the MMU will be off at23 the time when you call the decompressor code. You normally call24 the kernel at this address to start it booting. This doesn't have25 to be located in RAM, it can be in flash or other read-only or26 read-write addressable medium.27 28ZBSSADDR29 Start address of zero-initialised work area for the decompressor.30 This must be pointing at RAM. The decompressor will zero initialise31 this for you. Again, the MMU will be off.32 33ZRELADDR34 This is the address where the decompressed kernel will be written,35 and eventually executed. The following constraint must be valid:36 37 __virt_to_phys(TEXTADDR) == ZRELADDR38 39 The initial part of the kernel is carefully coded to be position40 independent.41 42INITRD_PHYS43 Physical address to place the initial RAM disk. Only relevant if44 you are using the bootpImage stuff (which only works on the old45 struct param_struct).46 47INITRD_VIRT48 Virtual address of the initial RAM disk. The following constraint49 must be valid:50 51 __virt_to_phys(INITRD_VIRT) == INITRD_PHYS52 53PARAMS_PHYS54 Physical address of the struct param_struct or tag list, giving the55 kernel various parameters about its execution environment.56 57 58Kernel Symbols59--------------60 61PHYS_OFFSET62 Physical start address of the first bank of RAM.63 64PAGE_OFFSET65 Virtual start address of the first bank of RAM. During the kernel66 boot phase, virtual address PAGE_OFFSET will be mapped to physical67 address PHYS_OFFSET, along with any other mappings you supply.68 This should be the same value as TASK_SIZE.69 70TASK_SIZE71 The maximum size of a user process in bytes. Since user space72 always starts at zero, this is the maximum address that a user73 process can access+1. The user space stack grows down from this74 address.75 76 Any virtual address below TASK_SIZE is deemed to be user process77 area, and therefore managed dynamically on a process by process78 basis by the kernel. I'll call this the user segment.79 80 Anything above TASK_SIZE is common to all processes. I'll call81 this the kernel segment.82 83 (In other words, you can't put IO mappings below TASK_SIZE, and84 hence PAGE_OFFSET).85 86TEXTADDR87 Virtual start address of kernel, normally PAGE_OFFSET + 0x8000.88 This is where the kernel image ends up. With the latest kernels,89 it must be located at 32768 bytes into a 128MB region. Previous90 kernels placed a restriction of 256MB here.91 92DATAADDR93 Virtual address for the kernel data segment. Must not be defined94 when using the decompressor.95 96VMALLOC_START / VMALLOC_END97 Virtual addresses bounding the vmalloc() area. There must not be98 any static mappings in this area; vmalloc will overwrite them.99 The addresses must also be in the kernel segment (see above).100 Normally, the vmalloc() area starts VMALLOC_OFFSET bytes above the101 last virtual RAM address (found using variable high_memory).102 103VMALLOC_OFFSET104 Offset normally incorporated into VMALLOC_START to provide a hole105 between virtual RAM and the vmalloc area. We do this to allow106 out of bounds memory accesses (eg, something writing off the end107 of the mapped memory map) to be caught. Normally set to 8MB.108 109Architecture Specific Macros110----------------------------111 112BOOT_MEM(pram,pio,vio)113 `pram` specifies the physical start address of RAM. Must always114 be present, and should be the same as PHYS_OFFSET.115 116 `pio` is the physical address of an 8MB region containing IO for117 use with the debugging macros in arch/arm/kernel/debug-armv.S.118 119 `vio` is the virtual address of the 8MB debugging region.120 121 It is expected that the debugging region will be re-initialised122 by the architecture specific code later in the code (via the123 MAPIO function).124 125BOOT_PARAMS126 Same as, and see PARAMS_PHYS.127 128FIXUP(func)129 Machine specific fixups, run before memory subsystems have been130 initialised.131 132MAPIO(func)133 Machine specific function to map IO areas (including the debug134 region above).135 136INITIRQ(func)137 Machine specific function to initialise interrupts.138