1Taken from list archive at http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2001-July/004064.html
2
3Initial definitions
4-------------------
5
6The following symbol definitions rely on you knowing the translation that
7__virt_to_phys() does for your machine.  This macro converts the passed
8virtual address to a physical address.  Normally, it is simply:
9
10		phys = virt - PAGE_OFFSET + PHYS_OFFSET
11
12
13Decompressor Symbols
14--------------------
15
16ZTEXTADDR
17	Start address of decompressor.  There's no point in talking about
18	virtual or physical addresses here, since the MMU will be off at
19	the time when you call the decompressor code.  You normally call
20	the kernel at this address to start it booting.  This doesn't have
21	to be located in RAM, it can be in flash or other read-only or
22	read-write addressable medium.
23
24ZBSSADDR
25	Start address of zero-initialised work area for the decompressor.
26	This must be pointing at RAM.  The decompressor will zero initialise
27	this for you.  Again, the MMU will be off.
28
29ZRELADDR
30	This is the address where the decompressed kernel will be written,
31	and eventually executed.  The following constraint must be valid:
32
33		__virt_to_phys(TEXTADDR) == ZRELADDR
34
35	The initial part of the kernel is carefully coded to be position
36	independent.
37
38INITRD_PHYS
39	Physical address to place the initial RAM disk.  Only relevant if
40	you are using the bootpImage stuff (which only works on the old
41	struct param_struct).
42
43INITRD_VIRT
44	Virtual address of the initial RAM disk.  The following  constraint
45	must be valid:
46
47		__virt_to_phys(INITRD_VIRT) == INITRD_PHYS
48
49PARAMS_PHYS
50	Physical address of the struct param_struct or tag list, giving the
51	kernel various parameters about its execution environment.
52
53
54Kernel Symbols
55--------------
56
57PHYS_OFFSET
58	Physical start address of the first bank of RAM.
59
60PAGE_OFFSET
61	Virtual start address of the first bank of RAM.  During the kernel
62	boot phase, virtual address PAGE_OFFSET will be mapped to physical
63	address PHYS_OFFSET, along with any other mappings you supply.
64	This should be the same value as TASK_SIZE.
65
66TASK_SIZE
67	The maximum size of a user process in bytes.  Since user space
68	always starts at zero, this is the maximum address that a user
69	process can access+1.  The user space stack grows down from this
70	address.
71
72	Any virtual address below TASK_SIZE is deemed to be user process
73	area, and therefore managed dynamically on a process by process
74	basis by the kernel.  I'll call this the user segment.
75
76	Anything above TASK_SIZE is common to all processes.  I'll call
77	this the kernel segment.
78
79	(In other words, you can't put IO mappings below TASK_SIZE, and
80	hence PAGE_OFFSET).
81
82TEXTADDR
83	Virtual start address of kernel, normally PAGE_OFFSET + 0x8000.
84	This is where the kernel image ends up.  With the latest kernels,
85	it must be located at 32768 bytes into a 128MB region.  Previous
86	kernels placed a restriction of 256MB here.
87
88DATAADDR
89	Virtual address for the kernel data segment.  Must not be defined
90	when using the decompressor.
91
92VMALLOC_START
93VMALLOC_END
94	Virtual addresses bounding the vmalloc() area.  There must not be
95	any static mappings in this area; vmalloc will overwrite them.
96	The addresses must also be in the kernel segment (see above).
97	Normally, the vmalloc() area starts VMALLOC_OFFSET bytes above the
98	last virtual RAM address (found using variable high_memory).
99
100VMALLOC_OFFSET
101	Offset normally incorporated into VMALLOC_START to provide a hole
102	between virtual RAM and the vmalloc area.  We do this to allow
103	out of bounds memory accesses (eg, something writing off the end
104	of the mapped memory map) to be caught.  Normally set to 8MB.
105
106Architecture Specific Macros
107----------------------------
108
109BOOT_MEM(pram,pio,vio)
110	`pram' specifies the physical start address of RAM.  Must always
111	be present, and should be the same as PHYS_OFFSET.
112
113	`pio' is the physical address of an 8MB region containing IO for
114	use with the debugging macros in arch/arm/kernel/debug-armv.S.
115
116	`vio' is the virtual address of the 8MB debugging region.
117
118	It is expected that the debugging region will be re-initialised
119	by the architecture specific code later in the code (via the
120	MAPIO function).
121
122BOOT_PARAMS
123	Same as, and see PARAMS_PHYS.
124
125FIXUP(func)
126	Machine specific fixups, run before memory subsystems have been
127	initialised.
128
129MAPIO(func)
130	Machine specific function to map IO areas (including the debug
131	region above).
132
133INITIRQ(func)
134	Machine specific function to initialise interrupts.
135
136