xref: /openbmc/linux/arch/x86/mm/ident_map.c (revision a44e4f3a)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Helper routines for building identity mapping page tables. This is
4  * included by both the compressed kernel and the regular kernel.
5  */
6 
7 static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
8 			   unsigned long addr, unsigned long end)
9 {
10 	addr &= PMD_MASK;
11 	for (; addr < end; addr += PMD_SIZE) {
12 		pmd_t *pmd = pmd_page + pmd_index(addr);
13 
14 		if (pmd_present(*pmd))
15 			continue;
16 
17 		set_pmd(pmd, __pmd((addr - info->offset) | info->page_flag));
18 	}
19 }
20 
21 static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
22 			  unsigned long addr, unsigned long end)
23 {
24 	unsigned long next;
25 
26 	for (; addr < end; addr = next) {
27 		pud_t *pud = pud_page + pud_index(addr);
28 		pmd_t *pmd;
29 
30 		next = (addr & PUD_MASK) + PUD_SIZE;
31 		if (next > end)
32 			next = end;
33 
34 		if (info->direct_gbpages) {
35 			pud_t pudval;
36 
37 			if (pud_present(*pud))
38 				continue;
39 
40 			addr &= PUD_MASK;
41 			pudval = __pud((addr - info->offset) | info->page_flag);
42 			set_pud(pud, pudval);
43 			continue;
44 		}
45 
46 		if (pud_present(*pud)) {
47 			pmd = pmd_offset(pud, 0);
48 			ident_pmd_init(info, pmd, addr, next);
49 			continue;
50 		}
51 		pmd = (pmd_t *)info->alloc_pgt_page(info->context);
52 		if (!pmd)
53 			return -ENOMEM;
54 		ident_pmd_init(info, pmd, addr, next);
55 		set_pud(pud, __pud(__pa(pmd) | info->kernpg_flag));
56 	}
57 
58 	return 0;
59 }
60 
61 static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
62 			  unsigned long addr, unsigned long end)
63 {
64 	unsigned long next;
65 
66 	for (; addr < end; addr = next) {
67 		p4d_t *p4d = p4d_page + p4d_index(addr);
68 		pud_t *pud;
69 
70 		next = (addr & P4D_MASK) + P4D_SIZE;
71 		if (next > end)
72 			next = end;
73 
74 		if (p4d_present(*p4d)) {
75 			pud = pud_offset(p4d, 0);
76 			ident_pud_init(info, pud, addr, next);
77 			continue;
78 		}
79 		pud = (pud_t *)info->alloc_pgt_page(info->context);
80 		if (!pud)
81 			return -ENOMEM;
82 		ident_pud_init(info, pud, addr, next);
83 		set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
84 	}
85 
86 	return 0;
87 }
88 
89 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
90 			      unsigned long pstart, unsigned long pend)
91 {
92 	unsigned long addr = pstart + info->offset;
93 	unsigned long end = pend + info->offset;
94 	unsigned long next;
95 	int result;
96 
97 	/* Set the default pagetable flags if not supplied */
98 	if (!info->kernpg_flag)
99 		info->kernpg_flag = _KERNPG_TABLE;
100 
101 	/* Filter out unsupported __PAGE_KERNEL_* bits: */
102 	info->kernpg_flag &= __default_kernel_pte_mask;
103 
104 	for (; addr < end; addr = next) {
105 		pgd_t *pgd = pgd_page + pgd_index(addr);
106 		p4d_t *p4d;
107 
108 		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
109 		if (next > end)
110 			next = end;
111 
112 		if (pgd_present(*pgd)) {
113 			p4d = p4d_offset(pgd, 0);
114 			result = ident_p4d_init(info, p4d, addr, next);
115 			if (result)
116 				return result;
117 			continue;
118 		}
119 
120 		p4d = (p4d_t *)info->alloc_pgt_page(info->context);
121 		if (!p4d)
122 			return -ENOMEM;
123 		result = ident_p4d_init(info, p4d, addr, next);
124 		if (result)
125 			return result;
126 		if (pgtable_l5_enabled()) {
127 			set_pgd(pgd, __pgd(__pa(p4d) | info->kernpg_flag));
128 		} else {
129 			/*
130 			 * With p4d folded, pgd is equal to p4d.
131 			 * The pgd entry has to point to the pud page table in this case.
132 			 */
133 			pud_t *pud = pud_offset(p4d, 0);
134 			set_pgd(pgd, __pgd(__pa(pud) | info->kernpg_flag));
135 		}
136 	}
137 
138 	return 0;
139 }
140