1 files changed, 225 insertions, 0 deletions
diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
new file mode 100644
index 000000000000..bd5d101c5c37
--- /dev/null
+++ b/arch/x86/mm/ident_map.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helper routines for building identity mapping page tables. This is
+ * included by both the compressed kernel and the regular kernel.
+ */
+
+static void free_pte(struct x86_mapping_info *info, pmd_t *pmd)
+{
+	pte_t *pte = pte_offset_kernel(pmd, 0);
+
+	info->free_pgt_page(pte, info->context);
+}
+
+static void free_pmd(struct x86_mapping_info *info, pud_t *pud)
+{
+	pmd_t *pmd = pmd_offset(pud, 0);
+	int i;
+
+	for (i = 0; i < PTRS_PER_PMD; i++) {
+		if (!pmd_present(pmd[i]))
+			continue;
+
+		if (pmd_leaf(pmd[i]))
+			continue;
+
+		free_pte(info, &pmd[i]);
+	}
+
+	info->free_pgt_page(pmd, info->context);
+}
+
+static void free_pud(struct x86_mapping_info *info, p4d_t *p4d)
+{
+	pud_t *pud = pud_offset(p4d, 0);
+	int i;
+
+	for (i = 0; i < PTRS_PER_PUD; i++) {
+		if (!pud_present(pud[i]))
+			continue;
+
+		if (pud_leaf(pud[i]))
+			continue;
+
+		free_pmd(info, &pud[i]);
+	}
+
+	info->free_pgt_page(pud, info->context);
+}
+
+static void free_p4d(struct x86_mapping_info *info, pgd_t *pgd)
+{
+	p4d_t *p4d = p4d_offset(pgd, 0);
+	int i;
+
+	for (i = 0; i < PTRS_PER_P4D; i++) {
+		if (!p4d_present(p4d[i]))
+			continue;
+
+		free_pud(info, &p4d[i]);
+	}
+
+	if (pgtable_l5_enabled())
+		info->free_pgt_page(p4d, info->context);
+}
+
+void kernel_ident_mapping_free(struct x86_mapping_info *info, pgd_t *pgd)
+{
+	int i;
+
+	for (i = 0; i < PTRS_PER_PGD; i++) {
+		if (!pgd_present(pgd[i]))
+			continue;
+
+		free_p4d(info, &pgd[i]);
+	}
+
+	info->free_pgt_page(pgd, info->context);
+}
+
+static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
+			   unsigned long addr, unsigned long end)
+{
+	addr &= PMD_MASK;
+	for (; addr < end; addr += PMD_SIZE) {
+		pmd_t *pmd = pmd_page + pmd_index(addr);
+
+		if (pmd_present(*pmd))
+			continue;
+
+		set_pmd(pmd, __pmd((addr - info->offset) | info->page_flag));
+	}
+}
+
+static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
+			  unsigned long addr, unsigned long end)
+{
+	unsigned long next;
+
+	for (; addr < end; addr = next) {
+		pud_t *pud = pud_page + pud_index(addr);
+		pmd_t *pmd;
+		bool use_gbpage;
+
+		next = pud_addr_end(addr, end);
+
+		/* if this is already a gbpage, this portion is already mapped */
+		if (pud_leaf(*pud))
+			continue;
+
+		/* Is using a gbpage allowed? */
+		use_gbpage = info->direct_gbpages;
+
+		/* Don't use gbpage if it maps more than the requested region. */
+		/* at the begining: */
+		use_gbpage &= ((addr & ~PUD_MASK) == 0);
+		/* ... or at the end: */
+		use_gbpage &= ((next & ~PUD_MASK) == 0);
+
+		/* Never overwrite existing mappings */
+		use_gbpage &= !pud_present(*pud);
+
+		if (use_gbpage) {
+			pud_t pudval;
+
+			pudval = __pud((addr - info->offset) | info->page_flag);
+			set_pud(pud, pudval);
+			continue;
+		}
+
+		if (pud_present(*pud)) {
+			pmd = pmd_offset(pud, 0);
+			ident_pmd_init(info, pmd, addr, next);
+			continue;
+		}
+		pmd = (pmd_t *)info->alloc_pgt_page(info->context);
+		if (!pmd)
+			return -ENOMEM;
+		ident_pmd_init(info, pmd, addr, next);
+		set_pud(pud, __pud(__pa(pmd) | info->kernpg_flag));
+	}
+
+	return 0;
+}
+
+static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
+			  unsigned long addr, unsigned long end)
+{
+	unsigned long next;
+	int result;
+
+	for (; addr < end; addr = next) {
+		p4d_t *p4d = p4d_page + p4d_index(addr);
+		pud_t *pud;
+
+		next = p4d_addr_end(addr, end);
+		if (p4d_present(*p4d)) {
+			pud = pud_offset(p4d, 0);
+			result = ident_pud_init(info, pud, addr, next);
+			if (result)
+				return result;
+
+			continue;
+		}
+		pud = (pud_t *)info->alloc_pgt_page(info->context);
+		if (!pud)
+			return -ENOMEM;
+
+		result = ident_pud_init(info, pud, addr, next);
+		if (result)
+			return result;
+
+		set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag | _PAGE_NOPTISHADOW));
+	}
+
+	return 0;
+}
+
+int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
+			      unsigned long pstart, unsigned long pend)
+{
+	unsigned long addr = pstart + info->offset;
+	unsigned long end = pend + info->offset;
+	unsigned long next;
+	int result;
+
+	/* Set the default pagetable flags if not supplied */
+	if (!info->kernpg_flag)
+		info->kernpg_flag = _KERNPG_TABLE;
+
+	/* Filter out unsupported __PAGE_KERNEL_* bits: */
+	info->kernpg_flag &= __default_kernel_pte_mask;
+
+	for (; addr < end; addr = next) {
+		pgd_t *pgd = pgd_page + pgd_index(addr);
+		p4d_t *p4d;
+
+		next = pgd_addr_end(addr, end);
+		if (pgd_present(*pgd)) {
+			p4d = p4d_offset(pgd, 0);
+			result = ident_p4d_init(info, p4d, addr, next);
+			if (result)
+				return result;
+			continue;
+		}
+
+		p4d = (p4d_t *)info->alloc_pgt_page(info->context);
+		if (!p4d)
+			return -ENOMEM;
+		result = ident_p4d_init(info, p4d, addr, next);
+		if (result)
+			return result;
+		if (pgtable_l5_enabled()) {
+			set_pgd(pgd, __pgd(__pa(p4d) | info->kernpg_flag | _PAGE_NOPTISHADOW));
+		} else {
+			/*
+			 * With p4d folded, pgd is equal to p4d.
+			 * The pgd entry has to point to the pud page table in this case.
+			 */
+			pud_t *pud = pud_offset(p4d, 0);
+			set_pgd(pgd, __pgd(__pa(pud) | info->kernpg_flag | _PAGE_NOPTISHADOW));
+		}
+	}
+
+	return 0;
+}