1 files changed, 105 insertions, 0 deletions
diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c
new file mode 100644
index 000000000000..5410b2cac590
--- /dev/null
+++ b/arch/arm64/kernel/pi/map_range.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2023 Google LLC
+// Author: Ard Biesheuvel <ardb@google.com>
+
+#include <linux/types.h>
+#include <linux/sizes.h>
+
+#include <asm/memory.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+
+#include "pi.h"
+
+/**
+ * map_range - Map a contiguous range of physical pages into virtual memory
+ *
+ * @pte:		Address of physical pointer to array of pages to
+ *			allocate page tables from
+ * @start:		Virtual address of the start of the range
+ * @end:		Virtual address of the end of the range (exclusive)
+ * @pa:			Physical address of the start of the range
+ * @prot:		Access permissions of the range
+ * @level:		Translation level for the mapping
+ * @tbl:		The level @level page table to create the mappings in
+ * @may_use_cont:	Whether the use of the contiguous attribute is allowed
+ * @va_offset:		Offset between a physical page and its current mapping
+ * 			in the VA space
+ */
+void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot,
+		      int level, pte_t *tbl, bool may_use_cont, u64 va_offset)
+{
+	u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX;
+	u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK;
+	int lshift = (3 - level) * (PAGE_SHIFT - 3);
+	u64 lmask = (PAGE_SIZE << lshift) - 1;
+
+	start	&= PAGE_MASK;
+	pa	&= PAGE_MASK;
+
+	/* Advance tbl to the entry that covers start */
+	tbl += (start >> (lshift + PAGE_SHIFT)) % PTRS_PER_PTE;
+
+	/*
+	 * Set the right block/page bits for this level unless we are
+	 * clearing the mapping
+	 */
+	if (protval)
+		protval |= (level < 3) ? PMD_TYPE_SECT : PTE_TYPE_PAGE;
+
+	while (start < end) {
+		u64 next = min((start | lmask) + 1, PAGE_ALIGN(end));
+
+		if (level < 3 && (start | next | pa) & lmask) {
+			/*
+			 * This chunk needs a finer grained mapping. Create a
+			 * table mapping if necessary and recurse.
+			 */
+			if (pte_none(*tbl)) {
+				*tbl = __pte(__phys_to_pte_val(*pte) |
+					     PMD_TYPE_TABLE | PMD_TABLE_UXN);
+				*pte += PTRS_PER_PTE * sizeof(pte_t);
+			}
+			map_range(pte, start, next, pa, prot, level + 1,
+				  (pte_t *)(__pte_to_phys(*tbl) + va_offset),
+				  may_use_cont, va_offset);
+		} else {
+			/*
+			 * Start a contiguous range if start and pa are
+			 * suitably aligned
+			 */
+			if (((start | pa) & cmask) == 0 && may_use_cont)
+				protval |= PTE_CONT;
+
+			/*
+			 * Clear the contiguous attribute if the remaining
+			 * range does not cover a contiguous block
+			 */
+			if ((end & ~cmask) <= start)
+				protval &= ~PTE_CONT;
+
+			/* Put down a block or page mapping */
+			*tbl = __pte(__phys_to_pte_val(pa) | protval);
+		}
+		pa += next - start;
+		start = next;
+		tbl++;
+	}
+}
+
+asmlinkage u64 __init create_init_idmap(pgd_t *pg_dir, pteval_t clrmask)
+{
+	u64 ptep = (u64)pg_dir + PAGE_SIZE;
+	pgprot_t text_prot = PAGE_KERNEL_ROX;
+	pgprot_t data_prot = PAGE_KERNEL;
+
+	pgprot_val(text_prot) &= ~clrmask;
+	pgprot_val(data_prot) &= ~clrmask;
+
+	map_range(&ptep, (u64)_stext, (u64)__initdata_begin, (u64)_stext,
+		  text_prot, IDMAP_ROOT_LEVEL, (pte_t *)pg_dir, false, 0);
+	map_range(&ptep, (u64)__initdata_begin, (u64)_end, (u64)__initdata_begin,
+		  data_prot, IDMAP_ROOT_LEVEL, (pte_t *)pg_dir, false, 0);
+
+	return ptep;
+}