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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/config.h>
17#include <linux/kernel.h>
18#include <asm/page.h>
19#ifdef CONFIG_HIGHMEM
20#include <linux/threads.h>
21#include <asm/kmap_types.h>
22#endif
23
24/*
25 * Here we define all the compile-time 'special' virtual
26 * addresses. The point is to have a constant address at
27 * compile time, but to set the physical address only
28 * in the boot process. We allocate these special addresses
29 * from the top of unused virtual memory (0xfd000000 - 1 page) backwards.
30 * Also this lets us do fail-safe vmalloc(), we
31 * can guarantee that these special addresses and
32 * vmalloc()-ed addresses never overlap.
33 *
34 * these 'compile-time allocated' memory buffers are
35 * fixed-size 4k pages. (or larger if used with an increment
36 * highger than 1) use fixmap_set(idx,phys) to associate
37 * physical memory with fixmap indices.
38 *
39 * TLB entries of such buffers will not be flushed across
40 * task switches.
41 */
42
43/*
44 * on UP currently we will have no trace of the fixmap mechanism,
45 * no page table allocations, etc. This might change in the
46 * future, say framebuffers for the console driver(s) could be
47 * fix-mapped?
48 */
49enum fixed_addresses {
50 FIX_HOLE,
51#ifdef CONFIG_HIGHMEM
52 FIX_KMAP_BEGIN,
53 FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
54#endif
55 __end_of_fixed_addresses
56};
57
58extern void __set_fixmap (enum fixed_addresses idx,
59 unsigned long phys, pgprot_t flags);
60
61#define set_fixmap(idx, phys) \
62 __set_fixmap(idx, phys, PAGE_KERNEL)
63/*
64 * Some hardware wants to get fixmapped without caching.
65 */
66#define set_fixmap_nocache(idx, phys) \
67 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
68/*
69 * used by vmalloc.c.
70 *
71 * Leave one empty page between IO pages at 0xfd000000 and
72 * the start of the fixmap.
73 */
74#define FIXADDR_TOP (0xfcfff000UL)
75#define FIXADDR_SIZE ((__end_of_fixed_addresses) << PAGE_SHIFT)
76#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
77
78#define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
79#define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
80
81extern void __this_fixmap_does_not_exist(void);
82
83/*
84 * 'index to address' translation. If anyone tries to use the idx
85 * directly without tranlation, we catch the bug with a NULL-deference
86 * kernel oops. Illegal ranges of incoming indices are caught too.
87 */
88static inline unsigned long fix_to_virt(const unsigned int idx)
89{
90 /*
91 * this branch gets completely eliminated after inlining,
92 * except when someone tries to use fixaddr indices in an
93 * illegal way. (such as mixing up address types or using
94 * out-of-range indices).
95 *
96 * If it doesn't get removed, the linker will complain
97 * loudly with a reasonably clear error message..
98 */
99 if (idx >= __end_of_fixed_addresses)
100 __this_fixmap_does_not_exist();
101
102 return __fix_to_virt(idx);
103}
104
105static inline unsigned long virt_to_fix(const unsigned long vaddr)
106{
107 BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
108 return __virt_to_fix(vaddr);
109}
110
111#endif