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
7static 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
21static 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
61static 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	int result;
66
67	for (; addr < end; addr = next) {
68		p4d_t *p4d = p4d_page + p4d_index(addr);
69		pud_t *pud;
70
71		next = (addr & P4D_MASK) + P4D_SIZE;
72		if (next > end)
73			next = end;
74
75		if (p4d_present(*p4d)) {
76			pud = pud_offset(p4d, 0);
77			result = ident_pud_init(info, pud, addr, next);
78			if (result)
79				return result;
80
81			continue;
82		}
83		pud = (pud_t *)info->alloc_pgt_page(info->context);
84		if (!pud)
85			return -ENOMEM;
86
87		result = ident_pud_init(info, pud, addr, next);
88		if (result)
89			return result;
90
91		set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
92	}
93
94	return 0;
95}
96
97int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
98			      unsigned long pstart, unsigned long pend)
99{
100	unsigned long addr = pstart + info->offset;
101	unsigned long end = pend + info->offset;
102	unsigned long next;
103	int result;
104
105	/* Set the default pagetable flags if not supplied */
106	if (!info->kernpg_flag)
107		info->kernpg_flag = _KERNPG_TABLE;
108
109	/* Filter out unsupported __PAGE_KERNEL_* bits: */
110	info->kernpg_flag &= __default_kernel_pte_mask;
111
112	for (; addr < end; addr = next) {
113		pgd_t *pgd = pgd_page + pgd_index(addr);
114		p4d_t *p4d;
115
116		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
117		if (next > end)
118			next = end;
119
120		if (pgd_present(*pgd)) {
121			p4d = p4d_offset(pgd, 0);
122			result = ident_p4d_init(info, p4d, addr, next);
123			if (result)
124				return result;
125			continue;
126		}
127
128		p4d = (p4d_t *)info->alloc_pgt_page(info->context);
129		if (!p4d)
130			return -ENOMEM;
131		result = ident_p4d_init(info, p4d, addr, next);
132		if (result)
133			return result;
134		if (pgtable_l5_enabled()) {
135			set_pgd(pgd, __pgd(__pa(p4d) | info->kernpg_flag));
136		} else {
137			/*
138			 * With p4d folded, pgd is equal to p4d.
139			 * The pgd entry has to point to the pud page table in this case.
140			 */
141			pud_t *pud = pud_offset(p4d, 0);
142			set_pgd(pgd, __pgd(__pa(pud) | info->kernpg_flag));
143		}
144	}
145
146	return 0;
147}
148