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}