1 files changed, 250 insertions, 0 deletions
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
new file mode 100644
index 000000000..826cb200b
--- /dev/null
+++ b/arch/arm64/mm/pageattr.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/vmalloc.h>
+
+#include <asm/cacheflush.h>
+#include <asm/set_memory.h>
+#include <asm/tlbflush.h>
+#include <asm/kfence.h>
+
+struct page_change_data {
+	pgprot_t set_mask;
+	pgprot_t clear_mask;
+};
+
+bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
+
+bool can_set_direct_map(void)
+{
+	/*
+	 * rodata_full and DEBUG_PAGEALLOC require linear map to be
+	 * mapped at page granularity, so that it is possible to
+	 * protect/unprotect single pages.
+	 *
+	 * KFENCE pool requires page-granular mapping if initialized late.
+	 */
+	return rodata_full || debug_pagealloc_enabled() ||
+	       arm64_kfence_can_set_direct_map();
+}
+
+static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
+{
+	struct page_change_data *cdata = data;
+	pte_t pte = READ_ONCE(*ptep);
+
+	pte = clear_pte_bit(pte, cdata->clear_mask);
+	pte = set_pte_bit(pte, cdata->set_mask);
+
+	set_pte(ptep, pte);
+	return 0;
+}
+
+/*
+ * This function assumes that the range is mapped with PAGE_SIZE pages.
+ */
+static int __change_memory_common(unsigned long start, unsigned long size,
+				pgprot_t set_mask, pgprot_t clear_mask)
+{
+	struct page_change_data data;
+	int ret;
+
+	data.set_mask = set_mask;
+	data.clear_mask = clear_mask;
+
+	ret = apply_to_page_range(&init_mm, start, size, change_page_range,
+					&data);
+
+	flush_tlb_kernel_range(start, start + size);
+	return ret;
+}
+
+static int change_memory_common(unsigned long addr, int numpages,
+				pgprot_t set_mask, pgprot_t clear_mask)
+{
+	unsigned long start = addr;
+	unsigned long size = PAGE_SIZE * numpages;
+	unsigned long end = start + size;
+	struct vm_struct *area;
+	int i;
+
+	if (!PAGE_ALIGNED(addr)) {
+		start &= PAGE_MASK;
+		end = start + size;
+		WARN_ON_ONCE(1);
+	}
+
+	/*
+	 * Kernel VA mappings are always live, and splitting live section
+	 * mappings into page mappings may cause TLB conflicts. This means
+	 * we have to ensure that changing the permission bits of the range
+	 * we are operating on does not result in such splitting.
+	 *
+	 * Let's restrict ourselves to mappings created by vmalloc (or vmap).
+	 * Those are guaranteed to consist entirely of page mappings, and
+	 * splitting is never needed.
+	 *
+	 * So check whether the [addr, addr + size) interval is entirely
+	 * covered by precisely one VM area that has the VM_ALLOC flag set.
+	 */
+	area = find_vm_area((void *)addr);
+	if (!area ||
+	    end > (unsigned long)kasan_reset_tag(area->addr) + area->size ||
+	    !(area->flags & VM_ALLOC))
+		return -EINVAL;
+
+	if (!numpages)
+		return 0;
+
+	/*
+	 * If we are manipulating read-only permissions, apply the same
+	 * change to the linear mapping of the pages that back this VM area.
+	 */
+	if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
+			    pgprot_val(clear_mask) == PTE_RDONLY)) {
+		for (i = 0; i < area->nr_pages; i++) {
+			__change_memory_common((u64)page_address(area->pages[i]),
+					       PAGE_SIZE, set_mask, clear_mask);
+		}
+	}
+
+	/*
+	 * Get rid of potentially aliasing lazily unmapped vm areas that may
+	 * have permissions set that deviate from the ones we are setting here.
+	 */
+	vm_unmap_aliases();
+
+	return __change_memory_common(start, size, set_mask, clear_mask);
+}
+
+int set_memory_ro(unsigned long addr, int numpages)
+{
+	return change_memory_common(addr, numpages,
+					__pgprot(PTE_RDONLY),
+					__pgprot(PTE_WRITE));
+}
+
+int set_memory_rw(unsigned long addr, int numpages)
+{
+	return change_memory_common(addr, numpages,
+					__pgprot(PTE_WRITE),
+					__pgprot(PTE_RDONLY));
+}
+
+int set_memory_nx(unsigned long addr, int numpages)
+{
+	return change_memory_common(addr, numpages,
+					__pgprot(PTE_PXN),
+					__pgprot(PTE_MAYBE_GP));
+}
+
+int set_memory_x(unsigned long addr, int numpages)
+{
+	return change_memory_common(addr, numpages,
+					__pgprot(PTE_MAYBE_GP),
+					__pgprot(PTE_PXN));
+}
+
+int set_memory_valid(unsigned long addr, int numpages, int enable)
+{
+	if (enable)
+		return __change_memory_common(addr, PAGE_SIZE * numpages,
+					__pgprot(PTE_VALID),
+					__pgprot(0));
+	else
+		return __change_memory_common(addr, PAGE_SIZE * numpages,
+					__pgprot(0),
+					__pgprot(PTE_VALID));
+}
+
+int set_direct_map_invalid_noflush(struct page *page)
+{
+	struct page_change_data data = {
+		.set_mask = __pgprot(0),
+		.clear_mask = __pgprot(PTE_VALID),
+	};
+
+	if (!can_set_direct_map())
+		return 0;
+
+	return apply_to_page_range(&init_mm,
+				   (unsigned long)page_address(page),
+				   PAGE_SIZE, change_page_range, &data);
+}
+
+int set_direct_map_default_noflush(struct page *page)
+{
+	struct page_change_data data = {
+		.set_mask = __pgprot(PTE_VALID | PTE_WRITE),
+		.clear_mask = __pgprot(PTE_RDONLY),
+	};
+
+	if (!can_set_direct_map())
+		return 0;
+
+	return apply_to_page_range(&init_mm,
+				   (unsigned long)page_address(page),
+				   PAGE_SIZE, change_page_range, &data);
+}
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	if (!can_set_direct_map())
+		return;
+
+	set_memory_valid((unsigned long)page_address(page), numpages, enable);
+}
+#endif /* CONFIG_DEBUG_PAGEALLOC */
+
+/*
+ * This function is used to determine if a linear map page has been marked as
+ * not-valid. Walk the page table and check the PTE_VALID bit. This is based
+ * on kern_addr_valid(), which almost does what we need.
+ *
+ * Because this is only called on the kernel linear map,  p?d_sect() implies
+ * p?d_present(). When debug_pagealloc is enabled, sections mappings are
+ * disabled.
+ */
+bool kernel_page_present(struct page *page)
+{
+	pgd_t *pgdp;
+	p4d_t *p4dp;
+	pud_t *pudp, pud;
+	pmd_t *pmdp, pmd;
+	pte_t *ptep;
+	unsigned long addr = (unsigned long)page_address(page);
+
+	if (!can_set_direct_map())
+		return true;
+
+	pgdp = pgd_offset_k(addr);
+	if (pgd_none(READ_ONCE(*pgdp)))
+		return false;
+
+	p4dp = p4d_offset(pgdp, addr);
+	if (p4d_none(READ_ONCE(*p4dp)))
+		return false;
+
+	pudp = pud_offset(p4dp, addr);
+	pud = READ_ONCE(*pudp);
+	if (pud_none(pud))
+		return false;
+	if (pud_sect(pud))
+		return true;
+
+	pmdp = pmd_offset(pudp, addr);
+	pmd = READ_ONCE(*pmdp);
+	if (pmd_none(pmd))
+		return false;
+	if (pmd_sect(pmd))
+		return true;
+
+	ptep = pte_offset_kernel(pmdp, addr);
+	return pte_valid(READ_ONCE(*ptep));
+}