mm/kasan/init.c - virt/kvm/kvm - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains KASAN shadow initialization code.
  *
  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
  */

 #include <linux/memblock.h>
 #include <linux/init.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
 #include <linux/slab.h>

 #include <asm/page.h>
 #include <asm/pgalloc.h>

 #include "kasan.h"

 /*
  * This page serves two purposes:
  *   - It used as early shadow memory. The entire shadow region populated
  *     with this page, before we will be able to setup normal shadow memory.
  *   - Latter it reused it as zero shadow to cover large ranges of memory
  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  */
 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;

 #if CONFIG_PGTABLE_LEVELS > 4
 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
 static inline bool kasan_p4d_table(pgd_t pgd)
 {
 	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
 }
 #else
 static inline bool kasan_p4d_table(pgd_t pgd)
 {
 	return false;
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
 pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
 static inline bool kasan_pud_table(p4d_t p4d)
 {
 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
 }
 #else
 static inline bool kasan_pud_table(p4d_t p4d)
 {
 	return false;
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
 pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
 static inline bool kasan_pmd_table(pud_t pud)
 {
 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
 }
 #else
 static inline bool kasan_pmd_table(pud_t pud)
 {
 	return false;
 }
 #endif
 pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
 	__page_aligned_bss;

 static inline bool kasan_pte_table(pmd_t pmd)
 {
 	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
 }

 static inline bool kasan_early_shadow_page_entry(pte_t pte)
 {
 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
 }

 static __init void *early_alloc(size_t size, int node)
 {
 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
 					   MEMBLOCK_ALLOC_ACCESSIBLE, node);

 	if (!ptr)
 		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
 		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));

 	return ptr;
 }

 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
 				unsigned long end)
 {
 	pte_t *pte = pte_offset_kernel(pmd, addr);
 	pte_t zero_pte;

 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
 				PAGE_KERNEL);
 	zero_pte = pte_wrprotect(zero_pte);

 	while (addr + PAGE_SIZE <= end) {
 		set_pte_at(&init_mm, addr, pte, zero_pte);
 		addr += PAGE_SIZE;
 		pte = pte_offset_kernel(pmd, addr);
 	}
 }

 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 				unsigned long end)
 {
 	pmd_t *pmd = pmd_offset(pud, addr);
 	unsigned long next;

 	do {
 		next = pmd_addr_end(addr, end);

 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
 			pmd_populate_kernel(&init_mm, pmd,
 					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}

 		if (pmd_none(*pmd)) {
 			pte_t *p;

 			if (slab_is_available())
 				p = pte_alloc_one_kernel(&init_mm);
 			else
 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 			if (!p)
 				return -ENOMEM;

 			pmd_populate_kernel(&init_mm, pmd, p);
 		}
 		zero_pte_populate(pmd, addr, next);
 	} while (pmd++, addr = next, addr != end);

 	return 0;
 }

 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 				unsigned long end)
 {
 	pud_t *pud = pud_offset(p4d, addr);
 	unsigned long next;

 	do {
 		next = pud_addr_end(addr, end);
 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 			pmd_t *pmd;

 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
 			pmd_populate_kernel(&init_mm, pmd,
 					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}

 		if (pud_none(*pud)) {
 			pmd_t *p;

 			if (slab_is_available()) {
 				p = pmd_alloc(&init_mm, pud, addr);
 				if (!p)
 					return -ENOMEM;
 			} else {
 				pud_populate(&init_mm, pud,
 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 			}
 		}
 		zero_pmd_populate(pud, addr, next);
 	} while (pud++, addr = next, addr != end);

 	return 0;
 }

 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 				unsigned long end)
 {
 	p4d_t *p4d = p4d_offset(pgd, addr);
 	unsigned long next;

 	do {
 		next = p4d_addr_end(addr, end);
 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
 			pud_t *pud;
 			pmd_t *pmd;

 			p4d_populate(&init_mm, p4d,
 					lm_alias(kasan_early_shadow_pud));
 			pud = pud_offset(p4d, addr);
 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
 			pmd_populate_kernel(&init_mm, pmd,
 					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}

 		if (p4d_none(*p4d)) {
 			pud_t *p;

 			if (slab_is_available()) {
 				p = pud_alloc(&init_mm, p4d, addr);
 				if (!p)
 					return -ENOMEM;
 			} else {
 				p4d_populate(&init_mm, p4d,
 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 			}
 		}
 		zero_pud_populate(p4d, addr, next);
 	} while (p4d++, addr = next, addr != end);

 	return 0;
 }

 /**
  * kasan_populate_early_shadow - populate shadow memory region with
  *                               kasan_early_shadow_page
  * @shadow_start - start of the memory range to populate
  * @shadow_end   - end of the memory range to populate
  */
 int __ref kasan_populate_early_shadow(const void *shadow_start,
 					const void *shadow_end)
 {
 	unsigned long addr = (unsigned long)shadow_start;
 	unsigned long end = (unsigned long)shadow_end;
 	pgd_t *pgd = pgd_offset_k(addr);
 	unsigned long next;

 	do {
 		next = pgd_addr_end(addr, end);

 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 			p4d_t *p4d;
 			pud_t *pud;
 			pmd_t *pmd;

 			/*
 			 * kasan_early_shadow_pud should be populated with pmds
 			 * at this moment.
 			 * [pud,pmd]_populate*() below needed only for
 			 * 3,2 - level page tables where we don't have
 			 * puds,pmds, so pgd_populate(), pud_populate()
 			 * is noops.
 			 */
 			pgd_populate(&init_mm, pgd,
 					lm_alias(kasan_early_shadow_p4d));
 			p4d = p4d_offset(pgd, addr);
 			p4d_populate(&init_mm, p4d,
 					lm_alias(kasan_early_shadow_pud));
 			pud = pud_offset(p4d, addr);
 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
 			pmd_populate_kernel(&init_mm, pmd,
 					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}

 		if (pgd_none(*pgd)) {
 			p4d_t *p;

 			if (slab_is_available()) {
 				p = p4d_alloc(&init_mm, pgd, addr);
 				if (!p)
 					return -ENOMEM;
 			} else {
 				pgd_populate(&init_mm, pgd,
 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 			}
 		}
 		zero_p4d_populate(pgd, addr, next);
 	} while (pgd++, addr = next, addr != end);

 	return 0;
 }

 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 {
 	pte_t *pte;
 	int i;

 	for (i = 0; i < PTRS_PER_PTE; i++) {
 		pte = pte_start + i;
 		if (!pte_none(*pte))
 			return;
 	}

 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
 	pmd_clear(pmd);
 }

 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
 {
 	pmd_t *pmd;
 	int i;

 	for (i = 0; i < PTRS_PER_PMD; i++) {
 		pmd = pmd_start + i;
 		if (!pmd_none(*pmd))
 			return;
 	}

 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
 	pud_clear(pud);
 }

 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
 {
 	pud_t *pud;
 	int i;

 	for (i = 0; i < PTRS_PER_PUD; i++) {
 		pud = pud_start + i;
 		if (!pud_none(*pud))
 			return;
 	}

 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
 	p4d_clear(p4d);
 }

 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
 {
 	p4d_t *p4d;
 	int i;

 	for (i = 0; i < PTRS_PER_P4D; i++) {
 		p4d = p4d_start + i;
 		if (!p4d_none(*p4d))
 			return;
 	}

 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
 	pgd_clear(pgd);
 }

 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 				unsigned long end)
 {
 	unsigned long next;

 	for (; addr < end; addr = next, pte++) {
 		next = (addr + PAGE_SIZE) & PAGE_MASK;
 		if (next > end)
 			next = end;

 		if (!pte_present(*pte))
 			continue;

 		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
 			continue;
 		pte_clear(&init_mm, addr, pte);
 	}
 }

 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
 				unsigned long end)
 {
 	unsigned long next;

 	for (; addr < end; addr = next, pmd++) {
 		pte_t *pte;

 		next = pmd_addr_end(addr, end);

 		if (!pmd_present(*pmd))
 			continue;

 		if (kasan_pte_table(*pmd)) {
 			if (IS_ALIGNED(addr, PMD_SIZE) &&
 			    IS_ALIGNED(next, PMD_SIZE))
 				pmd_clear(pmd);
 			continue;
 		}
 		pte = pte_offset_kernel(pmd, addr);
 		kasan_remove_pte_table(pte, addr, next);
 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
 	}
 }

 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
 				unsigned long end)
 {
 	unsigned long next;

 	for (; addr < end; addr = next, pud++) {
 		pmd_t *pmd, *pmd_base;

 		next = pud_addr_end(addr, end);

 		if (!pud_present(*pud))
 			continue;

 		if (kasan_pmd_table(*pud)) {
 			if (IS_ALIGNED(addr, PUD_SIZE) &&
 			    IS_ALIGNED(next, PUD_SIZE))
 				pud_clear(pud);
 			continue;
 		}
 		pmd = pmd_offset(pud, addr);
 		pmd_base = pmd_offset(pud, 0);
 		kasan_remove_pmd_table(pmd, addr, next);
 		kasan_free_pmd(pmd_base, pud);
 	}
 }

 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
 				unsigned long end)
 {
 	unsigned long next;

 	for (; addr < end; addr = next, p4d++) {
 		pud_t *pud;

 		next = p4d_addr_end(addr, end);

 		if (!p4d_present(*p4d))
 			continue;

 		if (kasan_pud_table(*p4d)) {
 			if (IS_ALIGNED(addr, P4D_SIZE) &&
 			    IS_ALIGNED(next, P4D_SIZE))
 				p4d_clear(p4d);
 			continue;
 		}
 		pud = pud_offset(p4d, addr);
 		kasan_remove_pud_table(pud, addr, next);
 		kasan_free_pud(pud_offset(p4d, 0), p4d);
 	}
 }

 void kasan_remove_zero_shadow(void *start, unsigned long size)
 {
 	unsigned long addr, end, next;
 	pgd_t *pgd;

 	addr = (unsigned long)kasan_mem_to_shadow(start);
 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);

 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 		return;

 	for (; addr < end; addr = next) {
 		p4d_t *p4d;

 		next = pgd_addr_end(addr, end);

 		pgd = pgd_offset_k(addr);
 		if (!pgd_present(*pgd))
 			continue;

 		if (kasan_p4d_table(*pgd)) {
 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
 			    IS_ALIGNED(next, PGDIR_SIZE))
 				pgd_clear(pgd);
 			continue;
 		}

 		p4d = p4d_offset(pgd, addr);
 		kasan_remove_p4d_table(p4d, addr, next);
 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
 	}
 }

 int kasan_add_zero_shadow(void *start, unsigned long size)
 {
 	int ret;
 	void *shadow_start, *shadow_end;

 	shadow_start = kasan_mem_to_shadow(start);
 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);

 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 		return -EINVAL;

 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 	if (ret)
 		kasan_remove_zero_shadow(shadow_start,
 					size >> KASAN_SHADOW_SCALE_SHIFT);
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* This file contains KASAN shadow initialization code.
	*
	* Copyright (c) 2015 Samsung Electronics Co., Ltd.
	* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
	*/

	#include <linux/memblock.h>
	#include <linux/init.h>
	#include <linux/kasan.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/pfn.h>
	#include <linux/slab.h>

	#include <asm/page.h>
	#include <asm/pgalloc.h>

	#include "kasan.h"

	/*
	* This page serves two purposes:
	* - It used as early shadow memory. The entire shadow region populated
	* with this page, before we will be able to setup normal shadow memory.
	* - Latter it reused it as zero shadow to cover large ranges of memory
	* that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
	*/
	unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;

	#if CONFIG_PGTABLE_LEVELS > 4
	p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
	static inline bool kasan_p4d_table(pgd_t pgd)
	{
	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
	}
	#else
	static inline bool kasan_p4d_table(pgd_t pgd)
	{
	return false;
	}
	#endif
	#if CONFIG_PGTABLE_LEVELS > 3
	pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
	static inline bool kasan_pud_table(p4d_t p4d)
	{
	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
	}
	#else
	static inline bool kasan_pud_table(p4d_t p4d)
	{
	return false;
	}
	#endif
	#if CONFIG_PGTABLE_LEVELS > 2
	pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
	static inline bool kasan_pmd_table(pud_t pud)
	{
	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
	}
	#else
	static inline bool kasan_pmd_table(pud_t pud)
	{
	return false;
	}
	#endif
	pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
	__page_aligned_bss;

	static inline bool kasan_pte_table(pmd_t pmd)
	{
	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
	}

	static inline bool kasan_early_shadow_page_entry(pte_t pte)
	{
	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
	}

	static __init void *early_alloc(size_t size, int node)
	{
	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
	MEMBLOCK_ALLOC_ACCESSIBLE, node);

	if (!ptr)
	panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
	__func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));

	return ptr;
	}

	static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
	unsigned long end)
	{
	pte_t *pte = pte_offset_kernel(pmd, addr);
	pte_t zero_pte;

	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
	PAGE_KERNEL);
	zero_pte = pte_wrprotect(zero_pte);

	while (addr + PAGE_SIZE <= end) {
	set_pte_at(&init_mm, addr, pte, zero_pte);
	addr += PAGE_SIZE;
	pte = pte_offset_kernel(pmd, addr);
	}
	}

	static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
	unsigned long end)
	{
	pmd_t *pmd = pmd_offset(pud, addr);
	unsigned long next;

	do {
	next = pmd_addr_end(addr, end);

	if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
	pmd_populate_kernel(&init_mm, pmd,
	lm_alias(kasan_early_shadow_pte));
	continue;
	}

	if (pmd_none(*pmd)) {
	pte_t *p;

	if (slab_is_available())
	p = pte_alloc_one_kernel(&init_mm);
	else
	p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
	if (!p)
	return -ENOMEM;

	pmd_populate_kernel(&init_mm, pmd, p);
	}
	zero_pte_populate(pmd, addr, next);
	} while (pmd++, addr = next, addr != end);

	return 0;
	}

	static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
	unsigned long end)
	{
	pud_t *pud = pud_offset(p4d, addr);
	unsigned long next;

	do {
	next = pud_addr_end(addr, end);
	if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
	pmd_t *pmd;

	pud_populate(&init_mm, pud,
	lm_alias(kasan_early_shadow_pmd));
	pmd = pmd_offset(pud, addr);
	pmd_populate_kernel(&init_mm, pmd,
	lm_alias(kasan_early_shadow_pte));
	continue;
	}

	if (pud_none(*pud)) {
	pmd_t *p;

	if (slab_is_available()) {
	p = pmd_alloc(&init_mm, pud, addr);
	if (!p)
	return -ENOMEM;
	} else {
	pud_populate(&init_mm, pud,
	early_alloc(PAGE_SIZE, NUMA_NO_NODE));
	}
	}
	zero_pmd_populate(pud, addr, next);
	} while (pud++, addr = next, addr != end);

	return 0;
	}

	static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
	unsigned long end)
	{
	p4d_t *p4d = p4d_offset(pgd, addr);
	unsigned long next;

	do {
	next = p4d_addr_end(addr, end);
	if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
	pud_t *pud;
	pmd_t *pmd;

	p4d_populate(&init_mm, p4d,
	lm_alias(kasan_early_shadow_pud));
	pud = pud_offset(p4d, addr);
	pud_populate(&init_mm, pud,
	lm_alias(kasan_early_shadow_pmd));
	pmd = pmd_offset(pud, addr);
	pmd_populate_kernel(&init_mm, pmd,
	lm_alias(kasan_early_shadow_pte));
	continue;
	}

	if (p4d_none(*p4d)) {
	pud_t *p;

	if (slab_is_available()) {
	p = pud_alloc(&init_mm, p4d, addr);
	if (!p)
	return -ENOMEM;
	} else {
	p4d_populate(&init_mm, p4d,
	early_alloc(PAGE_SIZE, NUMA_NO_NODE));
	}
	}
	zero_pud_populate(p4d, addr, next);
	} while (p4d++, addr = next, addr != end);

	return 0;
	}

	/**
	* kasan_populate_early_shadow - populate shadow memory region with
	* kasan_early_shadow_page
	* @shadow_start - start of the memory range to populate
	* @shadow_end - end of the memory range to populate
	*/
	int __ref kasan_populate_early_shadow(const void *shadow_start,
	const void *shadow_end)
	{
	unsigned long addr = (unsigned long)shadow_start;
	unsigned long end = (unsigned long)shadow_end;
	pgd_t *pgd = pgd_offset_k(addr);
	unsigned long next;

	do {
	next = pgd_addr_end(addr, end);

	if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;

	/*
	* kasan_early_shadow_pud should be populated with pmds
	* at this moment.
	* [pud,pmd]_populate*() below needed only for
	* 3,2 - level page tables where we don't have
	* puds,pmds, so pgd_populate(), pud_populate()
	* is noops.
	*/
	pgd_populate(&init_mm, pgd,
	lm_alias(kasan_early_shadow_p4d));
	p4d = p4d_offset(pgd, addr);
	p4d_populate(&init_mm, p4d,
	lm_alias(kasan_early_shadow_pud));
	pud = pud_offset(p4d, addr);
	pud_populate(&init_mm, pud,
	lm_alias(kasan_early_shadow_pmd));
	pmd = pmd_offset(pud, addr);
	pmd_populate_kernel(&init_mm, pmd,
	lm_alias(kasan_early_shadow_pte));
	continue;
	}

	if (pgd_none(*pgd)) {
	p4d_t *p;

	if (slab_is_available()) {
	p = p4d_alloc(&init_mm, pgd, addr);
	if (!p)
	return -ENOMEM;
	} else {
	pgd_populate(&init_mm, pgd,
	early_alloc(PAGE_SIZE, NUMA_NO_NODE));
	}
	}
	zero_p4d_populate(pgd, addr, next);
	} while (pgd++, addr = next, addr != end);

	return 0;
	}

	static void kasan_free_pte(pte_t pte_start, pmd_t pmd)
	{
	pte_t *pte;
	int i;

	for (i = 0; i < PTRS_PER_PTE; i++) {
	pte = pte_start + i;
	if (!pte_none(*pte))
	return;
	}

	pte_free_kernel(&init_mm, (pte_t )page_to_virt(pmd_page(pmd)));
	pmd_clear(pmd);
	}

	static void kasan_free_pmd(pmd_t pmd_start, pud_t pud)
	{
	pmd_t *pmd;
	int i;

	for (i = 0; i < PTRS_PER_PMD; i++) {
	pmd = pmd_start + i;
	if (!pmd_none(*pmd))
	return;
	}

	pmd_free(&init_mm, (pmd_t )page_to_virt(pud_page(pud)));
	pud_clear(pud);
	}

	static void kasan_free_pud(pud_t pud_start, p4d_t p4d)
	{
	pud_t *pud;
	int i;

	for (i = 0; i < PTRS_PER_PUD; i++) {
	pud = pud_start + i;
	if (!pud_none(*pud))
	return;
	}

	pud_free(&init_mm, (pud_t )page_to_virt(p4d_page(p4d)));
	p4d_clear(p4d);
	}

	static void kasan_free_p4d(p4d_t p4d_start, pgd_t pgd)
	{
	p4d_t *p4d;
	int i;

	for (i = 0; i < PTRS_PER_P4D; i++) {
	p4d = p4d_start + i;
	if (!p4d_none(*p4d))
	return;
	}

	p4d_free(&init_mm, (p4d_t )page_to_virt(pgd_page(pgd)));
	pgd_clear(pgd);
	}

	static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
	unsigned long end)
	{
	unsigned long next;

	for (; addr < end; addr = next, pte++) {
	next = (addr + PAGE_SIZE) & PAGE_MASK;
	if (next > end)
	next = end;

	if (!pte_present(*pte))
	continue;

	if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
	continue;
	pte_clear(&init_mm, addr, pte);
	}
	}

	static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
	unsigned long end)
	{
	unsigned long next;

	for (; addr < end; addr = next, pmd++) {
	pte_t *pte;

	next = pmd_addr_end(addr, end);

	if (!pmd_present(*pmd))
	continue;

	if (kasan_pte_table(*pmd)) {
	if (IS_ALIGNED(addr, PMD_SIZE) &&
	IS_ALIGNED(next, PMD_SIZE))
	pmd_clear(pmd);
	continue;
	}
	pte = pte_offset_kernel(pmd, addr);
	kasan_remove_pte_table(pte, addr, next);
	kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
	}
	}

	static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
	unsigned long end)
	{
	unsigned long next;

	for (; addr < end; addr = next, pud++) {
	pmd_t pmd, pmd_base;

	next = pud_addr_end(addr, end);

	if (!pud_present(*pud))
	continue;

	if (kasan_pmd_table(*pud)) {
	if (IS_ALIGNED(addr, PUD_SIZE) &&
	IS_ALIGNED(next, PUD_SIZE))
	pud_clear(pud);
	continue;
	}
	pmd = pmd_offset(pud, addr);
	pmd_base = pmd_offset(pud, 0);
	kasan_remove_pmd_table(pmd, addr, next);
	kasan_free_pmd(pmd_base, pud);
	}
	}

	static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
	unsigned long end)
	{
	unsigned long next;

	for (; addr < end; addr = next, p4d++) {
	pud_t *pud;

	next = p4d_addr_end(addr, end);

	if (!p4d_present(*p4d))
	continue;

	if (kasan_pud_table(*p4d)) {
	if (IS_ALIGNED(addr, P4D_SIZE) &&
	IS_ALIGNED(next, P4D_SIZE))
	p4d_clear(p4d);
	continue;
	}
	pud = pud_offset(p4d, addr);
	kasan_remove_pud_table(pud, addr, next);
	kasan_free_pud(pud_offset(p4d, 0), p4d);
	}
	}

	void kasan_remove_zero_shadow(void *start, unsigned long size)
	{
	unsigned long addr, end, next;
	pgd_t *pgd;

	addr = (unsigned long)kasan_mem_to_shadow(start);
	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);

	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) \|\|
	WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
	return;

	for (; addr < end; addr = next) {
	p4d_t *p4d;

	next = pgd_addr_end(addr, end);

	pgd = pgd_offset_k(addr);
	if (!pgd_present(*pgd))
	continue;

	if (kasan_p4d_table(*pgd)) {
	if (IS_ALIGNED(addr, PGDIR_SIZE) &&
	IS_ALIGNED(next, PGDIR_SIZE))
	pgd_clear(pgd);
	continue;
	}

	p4d = p4d_offset(pgd, addr);
	kasan_remove_p4d_table(p4d, addr, next);
	kasan_free_p4d(p4d_offset(pgd, 0), pgd);
	}
	}

	int kasan_add_zero_shadow(void *start, unsigned long size)
	{
	int ret;
	void shadow_start, shadow_end;

	shadow_start = kasan_mem_to_shadow(start);
	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);

	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) \|\|
	WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
	return -EINVAL;

	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
	if (ret)
	kasan_remove_zero_shadow(shadow_start,
	size >> KASAN_SHADOW_SCALE_SHIFT);
	return ret;
	}