1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Kernel page table mapping
4  *
5  * Copyright (C) 2015 ARM Ltd.
6  */
7 
8 #ifndef __ASM_KERNEL_PGTABLE_H
9 #define __ASM_KERNEL_PGTABLE_H
10 
11 #include <asm/boot.h>
12 #include <asm/pgtable-hwdef.h>
13 #include <asm/sparsemem.h>
14 
15 /*
16  * The linear mapping and the start of memory are both 2M aligned (per
17  * the arm64 booting.txt requirements). Hence we can use section mapping
18  * with 4K (section size = 2M) but not with 16K (section size = 32M) or
19  * 64K (section size = 512M).
20  */
21 
22 /*
23  * The idmap and swapper page tables need some space reserved in the kernel
24  * image. Both require pgd, pud (4 levels only) and pmd tables to (section)
25  * map the kernel. With the 64K page configuration, swapper and idmap need to
26  * map to pte level. The swapper also maps the FDT (see __create_page_tables
27  * for more information). Note that the number of ID map translation levels
28  * could be increased on the fly if system RAM is out of reach for the default
29  * VA range, so pages required to map highest possible PA are reserved in all
30  * cases.
31  */
32 #ifdef CONFIG_ARM64_4K_PAGES
33 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS - 1)
34 #else
35 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS)
36 #endif
37 
38 
39 /*
40  * If KASLR is enabled, then an offset K is added to the kernel address
41  * space. The bottom 21 bits of this offset are zero to guarantee 2MB
42  * alignment for PA and VA.
43  *
44  * For each pagetable level of the swapper, we know that the shift will
45  * be larger than 21 (for the 4KB granule case we use section maps thus
46  * the smallest shift is actually 30) thus there is the possibility that
47  * KASLR can increase the number of pagetable entries by 1, so we make
48  * room for this extra entry.
49  *
50  * Note KASLR cannot increase the number of required entries for a level
51  * by more than one because it increments both the virtual start and end
52  * addresses equally (the extra entry comes from the case where the end
53  * address is just pushed over a boundary and the start address isn't).
54  */
55 
56 #ifdef CONFIG_RANDOMIZE_BASE
57 #define EARLY_KASLR	(1)
58 #else
59 #define EARLY_KASLR	(0)
60 #endif
61 
62 #define SPAN_NR_ENTRIES(vstart, vend, shift) \
63 	((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1)
64 
65 #define EARLY_ENTRIES(vstart, vend, shift, add) \
66 	(SPAN_NR_ENTRIES(vstart, vend, shift) + (add))
67 
68 #define EARLY_PGDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, PGDIR_SHIFT, add))
69 
70 #if SWAPPER_PGTABLE_LEVELS > 3
71 #define EARLY_PUDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, PUD_SHIFT, add))
72 #else
73 #define EARLY_PUDS(vstart, vend, add) (0)
74 #endif
75 
76 #if SWAPPER_PGTABLE_LEVELS > 2
77 #define EARLY_PMDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, SWAPPER_TABLE_SHIFT, add))
78 #else
79 #define EARLY_PMDS(vstart, vend, add) (0)
80 #endif
81 
82 #define EARLY_PAGES(vstart, vend, add) ( 1 			/* PGDIR page */				\
83 			+ EARLY_PGDS((vstart), (vend), add) 	/* each PGDIR needs a next level page table */	\
84 			+ EARLY_PUDS((vstart), (vend), add)	/* each PUD needs a next level page table */	\
85 			+ EARLY_PMDS((vstart), (vend), add))	/* each PMD needs a next level page table */
86 #define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end, EARLY_KASLR))
87 
88 /* the initial ID map may need two extra pages if it needs to be extended */
89 #if VA_BITS < 48
90 #define INIT_IDMAP_DIR_SIZE	((INIT_IDMAP_DIR_PAGES + 2) * PAGE_SIZE)
91 #else
92 #define INIT_IDMAP_DIR_SIZE	(INIT_IDMAP_DIR_PAGES * PAGE_SIZE)
93 #endif
94 #define INIT_IDMAP_DIR_PAGES	EARLY_PAGES(KIMAGE_VADDR, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE, 1)
95 
96 /* Initial memory map size */
97 #ifdef CONFIG_ARM64_4K_PAGES
98 #define SWAPPER_BLOCK_SHIFT	PMD_SHIFT
99 #define SWAPPER_BLOCK_SIZE	PMD_SIZE
100 #define SWAPPER_TABLE_SHIFT	PUD_SHIFT
101 #else
102 #define SWAPPER_BLOCK_SHIFT	PAGE_SHIFT
103 #define SWAPPER_BLOCK_SIZE	PAGE_SIZE
104 #define SWAPPER_TABLE_SHIFT	PMD_SHIFT
105 #endif
106 
107 /*
108  * Initial memory map attributes.
109  */
110 #define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED | PTE_UXN)
111 #define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S | PTE_UXN)
112 
113 #ifdef CONFIG_ARM64_4K_PAGES
114 #define SWAPPER_RW_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS | PTE_WRITE)
115 #define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PMD_SECT_RDONLY)
116 #else
117 #define SWAPPER_RW_MMUFLAGS	(PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS | PTE_WRITE)
118 #define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PTE_RDONLY)
119 #endif
120 
121 #endif	/* __ASM_KERNEL_PGTABLE_H */
122