1 /* SPDX-License-Identifier: GPL-2.0
2 *
3 * fixmap.h: compile-time virtual memory allocation
4 *
5 * Copyright (C) 1998 Ingo Molnar
6 *
7 * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
8 */
9
10 #ifndef _ASM_FIXMAP_H
11 #define _ASM_FIXMAP_H
12
13 #include <linux/kernel.h>
14 #include <linux/threads.h>
15 #include <asm/page.h>
16
17 /*
18 * Here we define all the compile-time 'special' virtual
19 * addresses. The point is to have a constant address at
20 * compile time, but to set the physical address only
21 * in the boot process. We allocate these special addresses
22 * from the end of P3 backwards.
23 * Also this lets us do fail-safe vmalloc(), we
24 * can guarantee that these special addresses and
25 * vmalloc()-ed addresses never overlap.
26 *
27 * these 'compile-time allocated' memory buffers are
28 * fixed-size 4k pages. (or larger if used with an increment
29 * highger than 1) use fixmap_set(idx,phys) to associate
30 * physical memory with fixmap indices.
31 *
32 * TLB entries of such buffers will not be flushed across
33 * task switches.
34 */
35
36 /*
37 * on UP currently we will have no trace of the fixmap mechanizm,
38 * no page table allocations, etc. This might change in the
39 * future, say framebuffers for the console driver(s) could be
40 * fix-mapped?
41 */
42 enum fixed_addresses {
43 /*
44 * The FIX_CMAP entries are used by kmap_coherent() to get virtual
45 * addresses which are of a known color, and so their values are
46 * important. __fix_to_virt(FIX_CMAP_END - n) must give an address
47 * which is the same color as a page (n<<PAGE_SHIFT).
48 */
49 #define FIX_N_COLOURS 8
50 FIX_CMAP_BEGIN,
51 FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
52
53 #ifdef CONFIG_IOREMAP_FIXED
54 /*
55 * FIX_IOREMAP entries are useful for mapping physical address
56 * space before ioremap() is useable, e.g. really early in boot
57 * before kmalloc() is working.
58 */
59 #define FIX_N_IOREMAPS 32
60 FIX_IOREMAP_BEGIN,
61 FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
62 #endif
63
64 __end_of_fixed_addresses
65 };
66
67 extern void __set_fixmap(enum fixed_addresses idx,
68 unsigned long phys, pgprot_t flags);
69 extern void __clear_fixmap(enum fixed_addresses idx, pgprot_t flags);
70
71 /*
72 * used by vmalloc.c.
73 *
74 * Leave one empty page between vmalloc'ed areas and
75 * the start of the fixmap, and leave one page empty
76 * at the top of mem..
77 */
78 #define FIXADDR_TOP (P4SEG - PAGE_SIZE)
79 #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
80 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
81
82 #define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE
83
84 #include <asm-generic/fixmap.h>
85
86 #endif
87
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