1/*
2 * fixmap.h: compile-time virtual memory allocation
3 *
4 * This file is subject to the terms and conditions of the GNU General Public
5 * License.  See the file "COPYING" in the main directory of this archive
6 * for more details.
7 *
8 * Copyright (C) 1998 Ingo Molnar
9 *
10 * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
11 */
12
13#ifndef _ASM_FIXMAP_H
14#define _ASM_FIXMAP_H
15
16#include <linux/kernel.h>
17#include <asm/page.h>
18#ifdef CONFIG_HIGHMEM
19#include <linux/threads.h>
20#include <asm/kmap_types.h>
21#endif
22
23/*
24 * Here we define all the compile-time 'special' virtual
25 * addresses. The point is to have a constant address at
26 * compile time, but to set the physical address only
27 * in the boot process. We allocate these special  addresses
28 * from the end of P3 backwards.
29 * Also this lets us do fail-safe vmalloc(), we
30 * can guarantee that these special addresses and
31 * vmalloc()-ed addresses never overlap.
32 *
33 * these 'compile-time allocated' memory buffers are
34 * fixed-size 4k pages. (or larger if used with an increment
35 * highger than 1) use fixmap_set(idx,phys) to associate
36 * physical memory with fixmap indices.
37 *
38 * TLB entries of such buffers will not be flushed across
39 * task switches.
40 */
41
42/*
43 * on UP currently we will have no trace of the fixmap mechanizm,
44 * no page table allocations, etc. This might change in the
45 * future, say framebuffers for the console driver(s) could be
46 * fix-mapped?
47 */
48enum fixed_addresses {
49#ifdef CONFIG_HIGHMEM
50	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */
51	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
52#endif
53	__end_of_fixed_addresses
54};
55
56extern void __set_fixmap (enum fixed_addresses idx,
57					unsigned long phys, pgprot_t flags);
58
59#define set_fixmap(idx, phys) \
60		__set_fixmap(idx, phys, PAGE_KERNEL)
61/*
62 * Some hardware wants to get fixmapped without caching.
63 */
64#define set_fixmap_nocache(idx, phys) \
65		__set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
66/*
67 * used by vmalloc.c.
68 *
69 * Leave one empty page between vmalloc'ed areas and
70 * the start of the fixmap, and leave one page empty
71 * at the top of mem..
72 */
73#define FIXADDR_TOP	(P4SEG - PAGE_SIZE)
74#define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
75#define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
76
77#define __fix_to_virt(x)	(FIXADDR_TOP - ((x) << PAGE_SHIFT))
78#define __virt_to_fix(x)	((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
79
80extern void __this_fixmap_does_not_exist(void);
81
82/*
83 * 'index to address' translation. If anyone tries to use the idx
84 * directly without tranlation, we catch the bug with a NULL-deference
85 * kernel oops. Illegal ranges of incoming indices are caught too.
86 */
87static inline unsigned long fix_to_virt(const unsigned int idx)
88{
89	/*
90	 * this branch gets completely eliminated after inlining,
91	 * except when someone tries to use fixaddr indices in an
92	 * illegal way. (such as mixing up address types or using
93	 * out-of-range indices).
94	 *
95	 * If it doesn't get removed, the linker will complain
96	 * loudly with a reasonably clear error message..
97	 */
98	if (idx >= __end_of_fixed_addresses)
99		__this_fixmap_does_not_exist();
100
101        return __fix_to_virt(idx);
102}
103
104static inline unsigned long virt_to_fix(const unsigned long vaddr)
105{
106	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
107	return __virt_to_fix(vaddr);
108}
109
110#endif
111