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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#define FIX_N_COLOURS 16
50 FIX_CMAP_BEGIN,
51 FIX_CMAP_END = FIX_CMAP_BEGIN + FIX_N_COLOURS,
52#ifdef CONFIG_HIGHMEM
53 FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
54 FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
55#endif
56 __end_of_fixed_addresses
57};
58
59extern void __set_fixmap(enum fixed_addresses idx,
60 unsigned long phys, pgprot_t flags);
61
62#define set_fixmap(idx, phys) \
63 __set_fixmap(idx, phys, PAGE_KERNEL)
64/*
65 * Some hardware wants to get fixmapped without caching.
66 */
67#define set_fixmap_nocache(idx, phys) \
68 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
69/*
70 * used by vmalloc.c.
71 *
72 * Leave one empty page between vmalloc'ed areas and
73 * the start of the fixmap, and leave one page empty
74 * at the top of mem..
75 */
76#define FIXADDR_TOP (P4SEG - PAGE_SIZE)
77#define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
78#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
79
80#define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
81#define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
82
83extern void __this_fixmap_does_not_exist(void);
84
85/*
86 * 'index to address' translation. If anyone tries to use the idx
87 * directly without tranlation, we catch the bug with a NULL-deference
88 * kernel oops. Illegal ranges of incoming indices are caught too.
89 */
90static inline unsigned long fix_to_virt(const unsigned int idx)
91{
92 /*
93 * this branch gets completely eliminated after inlining,
94 * except when someone tries to use fixaddr indices in an
95 * illegal way. (such as mixing up address types or using
96 * out-of-range indices).
97 *
98 * If it doesn't get removed, the linker will complain
99 * loudly with a reasonably clear error message..
100 */
101 if (idx >= __end_of_fixed_addresses)
102 __this_fixmap_does_not_exist();
103
104 return __fix_to_virt(idx);
105}
106
107static inline unsigned long virt_to_fix(const unsigned long vaddr)
108{
109 BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
110 return __virt_to_fix(vaddr);
111}
112#endif