xref: /linux/arch/xtensa/include/asm/fixmap.h (revision 44f57d78)
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 <asm/pgtable.h>
17 #ifdef CONFIG_HIGHMEM
18 #include <linux/threads.h>
19 #include <asm/kmap_types.h>
20 #endif
21 
22 /*
23  * Here we define all the compile-time 'special' virtual
24  * addresses. The point is to have a constant address at
25  * compile time, but to set the physical address only
26  * in the boot process. We allocate these special addresses
27  * from the start of the consistent memory region upwards.
28  * Also this lets us do fail-safe vmalloc(), we
29  * can guarantee that these special addresses and
30  * vmalloc()-ed addresses never overlap.
31  *
32  * these 'compile-time allocated' memory buffers are
33  * fixed-size 4k pages. (or larger if used with an increment
34  * higher than 1) use fixmap_set(idx,phys) to associate
35  * physical memory with fixmap indices.
36  */
37 enum fixed_addresses {
38 #ifdef CONFIG_HIGHMEM
39 	/* reserved pte's for temporary kernel mappings */
40 	FIX_KMAP_BEGIN,
41 	FIX_KMAP_END = FIX_KMAP_BEGIN +
42 		(KM_TYPE_NR * NR_CPUS * DCACHE_N_COLORS) - 1,
43 #endif
44 	__end_of_fixed_addresses
45 };
46 
47 #define FIXADDR_TOP     (XCHAL_KSEG_CACHED_VADDR - PAGE_SIZE)
48 #define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
49 #define FIXADDR_START	((FIXADDR_TOP - FIXADDR_SIZE) & PMD_MASK)
50 
51 #define __fix_to_virt(x)	(FIXADDR_START + ((x) << PAGE_SHIFT))
52 #define __virt_to_fix(x)	(((x) - FIXADDR_START) >> PAGE_SHIFT)
53 
54 #ifndef __ASSEMBLY__
55 /*
56  * 'index to address' translation. If anyone tries to use the idx
57  * directly without translation, we catch the bug with a NULL-deference
58  * kernel oops. Illegal ranges of incoming indices are caught too.
59  */
60 static __always_inline unsigned long fix_to_virt(const unsigned int idx)
61 {
62 	/* Check if this memory layout is broken because fixmap overlaps page
63 	 * table.
64 	 */
65 	BUILD_BUG_ON(FIXADDR_START <
66 		     TLBTEMP_BASE_1 + TLBTEMP_SIZE);
67 	BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
68 	return __fix_to_virt(idx);
69 }
70 
71 static inline unsigned long virt_to_fix(const unsigned long vaddr)
72 {
73 	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
74 	return __virt_to_fix(vaddr);
75 }
76 
77 #endif
78 
79 #define kmap_get_fixmap_pte(vaddr) \
80 	pte_offset_kernel( \
81 		pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), \
82 		(vaddr) \
83 	)
84 
85 #endif
86