arch/arm64/mm/mmu.c - kernel/msm-4.9 - Gitiles

 /*
  * Based on arch/arm/mm/mmu.c
  *
  * Copyright (C) 1995-2005 Russell King
  * Copyright (C) 2012 ARM Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/mman.h>
 #include <linux/nodemask.h>
 #include <linux/memblock.h>
 #include <linux/fs.h>
 #include <linux/io.h>

 #include <asm/cputype.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/sizes.h>
 #include <asm/tlb.h>
 #include <asm/mmu_context.h>

 #include "mm.h"

 /*
  * Empty_zero_page is a special page that is used for zero-initialized data
  * and COW.
  */
 struct page *empty_zero_page;
 EXPORT_SYMBOL(empty_zero_page);

 pgprot_t pgprot_default;
 EXPORT_SYMBOL(pgprot_default);

 static pmdval_t prot_sect_kernel;

 struct cachepolicy {
 	const char	policy[16];
 	u64		mair;
 	u64		tcr;
 };

 static struct cachepolicy cache_policies[] __initdata = {
 	{
 		.policy		= "uncached",
 		.mair		= 0x44,			/* inner, outer non-cacheable */
 		.tcr		= TCR_IRGN_NC | TCR_ORGN_NC,
 	}, {
 		.policy		= "writethrough",
 		.mair		= 0xaa,			/* inner, outer write-through, read-allocate */
 		.tcr		= TCR_IRGN_WT | TCR_ORGN_WT,
 	}, {
 		.policy		= "writeback",
 		.mair		= 0xee,			/* inner, outer write-back, read-allocate */
 		.tcr		= TCR_IRGN_WBnWA | TCR_ORGN_WBnWA,
 	}
 };

 /*
  * These are useful for identifying cache coherency problems by allowing the
  * cache or the cache and writebuffer to be turned off. It changes the Normal
  * memory caching attributes in the MAIR_EL1 register.
  */
 static int __init early_cachepolicy(char *p)
 {
 	int i;
 	u64 tmp;

 	for (i = 0; i < ARRAY_SIZE(cache_policies); i++) {
 		int len = strlen(cache_policies[i].policy);

 		if (memcmp(p, cache_policies[i].policy, len) == 0)
 			break;
 	}
 	if (i == ARRAY_SIZE(cache_policies)) {
 		pr_err("ERROR: unknown or unsupported cache policy: %s\n", p);
 		return 0;
 	}

 	flush_cache_all();

 	/*
 	 * Modify MT_NORMAL attributes in MAIR_EL1.
 	 */
 	asm volatile(
 	"	mrs	%0, mair_el1\n"
 	"	bfi	%0, %1, #%2, #8\n"
 	"	msr	mair_el1, %0\n"
 	"	isb\n"
 	: "=&r" (tmp)
 	: "r" (cache_policies[i].mair), "i" (MT_NORMAL * 8));

 	/*
 	 * Modify TCR PTW cacheability attributes.
 	 */
 	asm volatile(
 	"	mrs	%0, tcr_el1\n"
 	"	bic	%0, %0, %2\n"
 	"	orr	%0, %0, %1\n"
 	"	msr	tcr_el1, %0\n"
 	"	isb\n"
 	: "=&r" (tmp)
 	: "r" (cache_policies[i].tcr), "r" (TCR_IRGN_MASK | TCR_ORGN_MASK));

 	flush_cache_all();

 	return 0;
 }
 early_param("cachepolicy", early_cachepolicy);

 /*
  * Adjust the PMD section entries according to the CPU in use.
  */
 static void __init init_mem_pgprot(void)
 {
 	pteval_t default_pgprot;
 	int i;

 	default_pgprot = PTE_ATTRINDX(MT_NORMAL);
 	prot_sect_kernel = PMD_TYPE_SECT | PMD_SECT_AF | PMD_ATTRINDX(MT_NORMAL);

 #ifdef CONFIG_SMP
 	/*
 	 * Mark memory with the "shared" attribute for SMP systems
 	 */
 	default_pgprot |= PTE_SHARED;
 	prot_sect_kernel |= PMD_SECT_S;
 #endif

 	for (i = 0; i < 16; i++) {
 		unsigned long v = pgprot_val(protection_map[i]);
 		protection_map[i] = __pgprot(v | default_pgprot);
 	}

 	pgprot_default = __pgprot(PTE_TYPE_PAGE | PTE_AF | default_pgprot);
 }

 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
 	if (!pfn_valid(pfn))
 		return pgprot_noncached(vma_prot);
 	else if (file->f_flags & O_SYNC)
 		return pgprot_writecombine(vma_prot);
 	return vma_prot;
 }
 EXPORT_SYMBOL(phys_mem_access_prot);

 static void __init *early_alloc(unsigned long sz)
 {
 	void *ptr = __va(memblock_alloc(sz, sz));
 	memset(ptr, 0, sz);
 	return ptr;
 }

 static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
 				  unsigned long end, unsigned long pfn)
 {
 	pte_t *pte;

 	if (pmd_none(*pmd)) {
 		pte = early_alloc(PTRS_PER_PTE * sizeof(pte_t));
 		__pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE);
 	}
 	BUG_ON(pmd_bad(*pmd));

 	pte = pte_offset_kernel(pmd, addr);
 	do {
 		set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 		pfn++;
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }

 static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
 				  unsigned long end, phys_addr_t phys)
 {
 	pmd_t *pmd;
 	unsigned long next;

 	/*
 	 * Check for initial section mappings in the pgd/pud and remove them.
 	 */
 	if (pud_none(*pud) || pud_bad(*pud)) {
 		pmd = early_alloc(PTRS_PER_PMD * sizeof(pmd_t));
 		pud_populate(&init_mm, pud, pmd);
 	}

 	pmd = pmd_offset(pud, addr);
 	do {
 		next = pmd_addr_end(addr, end);
 		/* try section mapping first */
 		if (((addr | next | phys) & ~SECTION_MASK) == 0)
 			set_pmd(pmd, __pmd(phys | prot_sect_kernel));
 		else
 			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys));
 		phys += next - addr;
 	} while (pmd++, addr = next, addr != end);
 }

 static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
 				  unsigned long end, unsigned long phys)
 {
 	pud_t *pud = pud_offset(pgd, addr);
 	unsigned long next;

 	do {
 		next = pud_addr_end(addr, end);
 		alloc_init_pmd(pud, addr, next, phys);
 		phys += next - addr;
 	} while (pud++, addr = next, addr != end);
 }

 /*
  * Create the page directory entries and any necessary page tables for the
  * mapping specified by 'md'.
  */
 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 				  phys_addr_t size)
 {
 	unsigned long addr, length, end, next;
 	pgd_t *pgd;

 	if (virt < VMALLOC_START) {
 		pr_warning("BUG: not creating mapping for 0x%016llx at 0x%016lx - outside kernel range\n",
 			   phys, virt);
 		return;
 	}

 	addr = virt & PAGE_MASK;
 	length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));

 	pgd = pgd_offset_k(addr);
 	end = addr + length;
 	do {
 		next = pgd_addr_end(addr, end);
 		alloc_init_pud(pgd, addr, next, phys);
 		phys += next - addr;
 	} while (pgd++, addr = next, addr != end);
 }

 #ifdef CONFIG_EARLY_PRINTK
 /*
  * Create an early I/O mapping using the pgd/pmd entries already populated
  * in head.S as this function is called too early to allocated any memory. The
  * mapping size is 2MB with 4KB pages or 64KB or 64KB pages.
  */
 void __iomem * __init early_io_map(phys_addr_t phys, unsigned long virt)
 {
 	unsigned long size, mask;
 	bool page64k = IS_ENABLED(ARM64_64K_PAGES);
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;

 	/*
 	 * No early pte entries with !ARM64_64K_PAGES configuration, so using
 	 * sections (pmd).
 	 */
 	size = page64k ? PAGE_SIZE : SECTION_SIZE;
 	mask = ~(size - 1);

 	pgd = pgd_offset_k(virt);
 	pud = pud_offset(pgd, virt);
 	if (pud_none(*pud))
 		return NULL;
 	pmd = pmd_offset(pud, virt);

 	if (page64k) {
 		if (pmd_none(*pmd))
 			return NULL;
 		pte = pte_offset_kernel(pmd, virt);
 		set_pte(pte, __pte((phys & mask) | PROT_DEVICE_nGnRE));
 	} else {
 		set_pmd(pmd, __pmd((phys & mask) | PROT_SECT_DEVICE_nGnRE));
 	}

 	return (void __iomem *)((virt & mask) + (phys & ~mask));
 }
 #endif

 static void __init map_mem(void)
 {
 	struct memblock_region *reg;

 	/* map all the memory banks */
 	for_each_memblock(memory, reg) {
 		phys_addr_t start = reg->base;
 		phys_addr_t end = start + reg->size;

 		if (start >= end)
 			break;

 		create_mapping(start, __phys_to_virt(start), end - start);
 	}
 }

 /*
  * paging_init() sets up the page tables, initialises the zone memory
  * maps and sets up the zero page.
  */
 void __init paging_init(void)
 {
 	void *zero_page;

 	/*
 	 * Maximum PGDIR_SIZE addressable via the initial direct kernel
 	 * mapping in swapper_pg_dir.
 	 */
 	memblock_set_current_limit((PHYS_OFFSET & PGDIR_MASK) + PGDIR_SIZE);

 	init_mem_pgprot();
 	map_mem();

 	/*
 	 * Finally flush the caches and tlb to ensure that we're in a
 	 * consistent state.
 	 */
 	flush_cache_all();
 	flush_tlb_all();

 	/* allocate the zero page. */
 	zero_page = early_alloc(PAGE_SIZE);

 	bootmem_init();

 	empty_zero_page = virt_to_page(zero_page);
 	__flush_dcache_page(empty_zero_page);

 	/*
 	 * TTBR0 is only used for the identity mapping at this stage. Make it
 	 * point to zero page to avoid speculatively fetching new entries.
 	 */
 	cpu_set_reserved_ttbr0();
 	flush_tlb_all();
 }

 /*
  * Enable the identity mapping to allow the MMU disabling.
  */
 void setup_mm_for_reboot(void)
 {
 	cpu_switch_mm(idmap_pg_dir, &init_mm);
 	flush_tlb_all();
 }

 /*
  * Check whether a kernel address is valid (derived from arch/x86/).
  */
 int kern_addr_valid(unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;

 	if ((((long)addr) >> VA_BITS) != -1UL)
 		return 0;

 	pgd = pgd_offset_k(addr);
 	if (pgd_none(*pgd))
 		return 0;

 	pud = pud_offset(pgd, addr);
 	if (pud_none(*pud))
 		return 0;

 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		return 0;

 	pte = pte_offset_kernel(pmd, addr);
 	if (pte_none(*pte))
 		return 0;

 	return pfn_valid(pte_pfn(*pte));
 }
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 #ifdef CONFIG_ARM64_64K_PAGES
 int __meminit vmemmap_populate(struct page *start_page,
 			       unsigned long size, int node)
 {
 	return vmemmap_populate_basepages(start_page, size, node);
 }
 #else	/* !CONFIG_ARM64_64K_PAGES */
 int __meminit vmemmap_populate(struct page *start_page,
 			       unsigned long size, int node)
 {
 	unsigned long addr = (unsigned long)start_page;
 	unsigned long end = (unsigned long)(start_page + size);
 	unsigned long next;
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;

 	do {
 		next = pmd_addr_end(addr, end);

 		pgd = vmemmap_pgd_populate(addr, node);
 		if (!pgd)
 			return -ENOMEM;

 		pud = vmemmap_pud_populate(pgd, addr, node);
 		if (!pud)
 			return -ENOMEM;

 		pmd = pmd_offset(pud, addr);
 		if (pmd_none(*pmd)) {
 			void *p = NULL;

 			p = vmemmap_alloc_block_buf(PMD_SIZE, node);
 			if (!p)
 				return -ENOMEM;

 			set_pmd(pmd, __pmd(__pa(p) | prot_sect_kernel));
 		} else
 			vmemmap_verify((pte_t *)pmd, node, addr, next);
 	} while (addr = next, addr != end);

 	return 0;
 }
 #endif	/* CONFIG_ARM64_64K_PAGES */
 void vmemmap_free(struct page *memmap, unsigned long nr_pages)
 {
 }
 #endif	/* CONFIG_SPARSEMEM_VMEMMAP */
	/*
	* Based on arch/arm/mm/mmu.c
	*
	* Copyright (C) 1995-2005 Russell King
	* Copyright (C) 2012 ARM Ltd.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include <linux/export.h>
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/init.h>
	#include <linux/mman.h>
	#include <linux/nodemask.h>
	#include <linux/memblock.h>
	#include <linux/fs.h>
	#include <linux/io.h>

	#include <asm/cputype.h>
	#include <asm/sections.h>
	#include <asm/setup.h>
	#include <asm/sizes.h>
	#include <asm/tlb.h>
	#include <asm/mmu_context.h>

	#include "mm.h"

	/*
	* Empty_zero_page is a special page that is used for zero-initialized data
	* and COW.
	*/
	struct page *empty_zero_page;
	EXPORT_SYMBOL(empty_zero_page);

	pgprot_t pgprot_default;
	EXPORT_SYMBOL(pgprot_default);

	static pmdval_t prot_sect_kernel;

	struct cachepolicy {
	const char policy[16];
	u64 mair;
	u64 tcr;
	};

	static struct cachepolicy cache_policies[] __initdata = {
	{
	.policy = "uncached",
	.mair = 0x44, /* inner, outer non-cacheable */
	.tcr = TCR_IRGN_NC \| TCR_ORGN_NC,
	}, {
	.policy = "writethrough",
	.mair = 0xaa, /* inner, outer write-through, read-allocate */
	.tcr = TCR_IRGN_WT \| TCR_ORGN_WT,
	}, {
	.policy = "writeback",
	.mair = 0xee, /* inner, outer write-back, read-allocate */
	.tcr = TCR_IRGN_WBnWA \| TCR_ORGN_WBnWA,
	}
	};

	/*
	* These are useful for identifying cache coherency problems by allowing the
	* cache or the cache and writebuffer to be turned off. It changes the Normal
	* memory caching attributes in the MAIR_EL1 register.
	*/
	static int __init early_cachepolicy(char *p)
	{
	int i;
	u64 tmp;

	for (i = 0; i < ARRAY_SIZE(cache_policies); i++) {
	int len = strlen(cache_policies[i].policy);

	if (memcmp(p, cache_policies[i].policy, len) == 0)
	break;
	}
	if (i == ARRAY_SIZE(cache_policies)) {
	pr_err("ERROR: unknown or unsupported cache policy: %s\n", p);
	return 0;
	}

	flush_cache_all();

	/*
	* Modify MT_NORMAL attributes in MAIR_EL1.
	*/
	asm volatile(
	" mrs %0, mair_el1\n"
	" bfi %0, %1, #%2, #8\n"
	" msr mair_el1, %0\n"
	" isb\n"
	: "=&r" (tmp)
	: "r" (cache_policies[i].mair), "i" (MT_NORMAL * 8));

	/*
	* Modify TCR PTW cacheability attributes.
	*/
	asm volatile(
	" mrs %0, tcr_el1\n"
	" bic %0, %0, %2\n"
	" orr %0, %0, %1\n"
	" msr tcr_el1, %0\n"
	" isb\n"
	: "=&r" (tmp)
	: "r" (cache_policies[i].tcr), "r" (TCR_IRGN_MASK \| TCR_ORGN_MASK));

	flush_cache_all();

	return 0;
	}
	early_param("cachepolicy", early_cachepolicy);

	/*
	* Adjust the PMD section entries according to the CPU in use.
	*/
	static void __init init_mem_pgprot(void)
	{
	pteval_t default_pgprot;
	int i;

	default_pgprot = PTE_ATTRINDX(MT_NORMAL);
	prot_sect_kernel = PMD_TYPE_SECT \| PMD_SECT_AF \| PMD_ATTRINDX(MT_NORMAL);

	#ifdef CONFIG_SMP
	/*
	* Mark memory with the "shared" attribute for SMP systems
	*/
	default_pgprot \|= PTE_SHARED;
	prot_sect_kernel \|= PMD_SECT_S;
	#endif

	for (i = 0; i < 16; i++) {
	unsigned long v = pgprot_val(protection_map[i]);
	protection_map[i] = __pgprot(v \| default_pgprot);
	}

	pgprot_default = __pgprot(PTE_TYPE_PAGE \| PTE_AF \| default_pgprot);
	}

	pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
	unsigned long size, pgprot_t vma_prot)
	{
	if (!pfn_valid(pfn))
	return pgprot_noncached(vma_prot);
	else if (file->f_flags & O_SYNC)
	return pgprot_writecombine(vma_prot);
	return vma_prot;
	}
	EXPORT_SYMBOL(phys_mem_access_prot);

	static void __init *early_alloc(unsigned long sz)
	{
	void *ptr = __va(memblock_alloc(sz, sz));
	memset(ptr, 0, sz);
	return ptr;
	}

	static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
	unsigned long end, unsigned long pfn)
	{
	pte_t *pte;

	if (pmd_none(*pmd)) {
	pte = early_alloc(PTRS_PER_PTE * sizeof(pte_t));
	__pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE);
	}
	BUG_ON(pmd_bad(*pmd));

	pte = pte_offset_kernel(pmd, addr);
	do {
	set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
	pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	}

	static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
	unsigned long end, phys_addr_t phys)
	{
	pmd_t *pmd;
	unsigned long next;

	/*
	* Check for initial section mappings in the pgd/pud and remove them.
	*/
	if (pud_none(pud) \|\| pud_bad(pud)) {
	pmd = early_alloc(PTRS_PER_PMD * sizeof(pmd_t));
	pud_populate(&init_mm, pud, pmd);
	}

	pmd = pmd_offset(pud, addr);
	do {
	next = pmd_addr_end(addr, end);
	/* try section mapping first */
	if (((addr \| next \| phys) & ~SECTION_MASK) == 0)
	set_pmd(pmd, __pmd(phys \| prot_sect_kernel));
	else
	alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys));
	phys += next - addr;
	} while (pmd++, addr = next, addr != end);
	}

	static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
	unsigned long end, unsigned long phys)
	{
	pud_t *pud = pud_offset(pgd, addr);
	unsigned long next;

	do {
	next = pud_addr_end(addr, end);
	alloc_init_pmd(pud, addr, next, phys);
	phys += next - addr;
	} while (pud++, addr = next, addr != end);
	}

	/*
	* Create the page directory entries and any necessary page tables for the
	* mapping specified by 'md'.
	*/
	static void __init create_mapping(phys_addr_t phys, unsigned long virt,
	phys_addr_t size)
	{
	unsigned long addr, length, end, next;
	pgd_t *pgd;

	if (virt < VMALLOC_START) {
	pr_warning("BUG: not creating mapping for 0x%016llx at 0x%016lx - outside kernel range\n",
	phys, virt);
	return;
	}

	addr = virt & PAGE_MASK;
	length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));

	pgd = pgd_offset_k(addr);
	end = addr + length;
	do {
	next = pgd_addr_end(addr, end);
	alloc_init_pud(pgd, addr, next, phys);
	phys += next - addr;
	} while (pgd++, addr = next, addr != end);
	}

	#ifdef CONFIG_EARLY_PRINTK
	/*
	* Create an early I/O mapping using the pgd/pmd entries already populated
	* in head.S as this function is called too early to allocated any memory. The
	* mapping size is 2MB with 4KB pages or 64KB or 64KB pages.
	*/
	void __iomem * __init early_io_map(phys_addr_t phys, unsigned long virt)
	{
	unsigned long size, mask;
	bool page64k = IS_ENABLED(ARM64_64K_PAGES);
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	/*
	* No early pte entries with !ARM64_64K_PAGES configuration, so using
	* sections (pmd).
	*/
	size = page64k ? PAGE_SIZE : SECTION_SIZE;
	mask = ~(size - 1);

	pgd = pgd_offset_k(virt);
	pud = pud_offset(pgd, virt);
	if (pud_none(*pud))
	return NULL;
	pmd = pmd_offset(pud, virt);

	if (page64k) {
	if (pmd_none(*pmd))
	return NULL;
	pte = pte_offset_kernel(pmd, virt);
	set_pte(pte, __pte((phys & mask) \| PROT_DEVICE_nGnRE));
	} else {
	set_pmd(pmd, __pmd((phys & mask) \| PROT_SECT_DEVICE_nGnRE));
	}

	return (void __iomem *)((virt & mask) + (phys & ~mask));
	}
	#endif

	static void __init map_mem(void)
	{
	struct memblock_region *reg;

	/* map all the memory banks */
	for_each_memblock(memory, reg) {
	phys_addr_t start = reg->base;
	phys_addr_t end = start + reg->size;

	if (start >= end)
	break;

	create_mapping(start, __phys_to_virt(start), end - start);
	}
	}

	/*
	* paging_init() sets up the page tables, initialises the zone memory
	* maps and sets up the zero page.
	*/
	void __init paging_init(void)
	{
	void *zero_page;

	/*
	* Maximum PGDIR_SIZE addressable via the initial direct kernel
	* mapping in swapper_pg_dir.
	*/
	memblock_set_current_limit((PHYS_OFFSET & PGDIR_MASK) + PGDIR_SIZE);

	init_mem_pgprot();
	map_mem();

	/*
	* Finally flush the caches and tlb to ensure that we're in a
	* consistent state.
	*/
	flush_cache_all();
	flush_tlb_all();

	/* allocate the zero page. */
	zero_page = early_alloc(PAGE_SIZE);

	bootmem_init();

	empty_zero_page = virt_to_page(zero_page);
	__flush_dcache_page(empty_zero_page);

	/*
	* TTBR0 is only used for the identity mapping at this stage. Make it
	* point to zero page to avoid speculatively fetching new entries.
	*/
	cpu_set_reserved_ttbr0();
	flush_tlb_all();
	}

	/*
	* Enable the identity mapping to allow the MMU disabling.
	*/
	void setup_mm_for_reboot(void)
	{
	cpu_switch_mm(idmap_pg_dir, &init_mm);
	flush_tlb_all();
	}

	/*
	* Check whether a kernel address is valid (derived from arch/x86/).
	*/
	int kern_addr_valid(unsigned long addr)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if ((((long)addr) >> VA_BITS) != -1UL)
	return 0;

	pgd = pgd_offset_k(addr);
	if (pgd_none(*pgd))
	return 0;

	pud = pud_offset(pgd, addr);
	if (pud_none(*pud))
	return 0;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
	return 0;

	pte = pte_offset_kernel(pmd, addr);
	if (pte_none(*pte))
	return 0;

	return pfn_valid(pte_pfn(*pte));
	}
	#ifdef CONFIG_SPARSEMEM_VMEMMAP
	#ifdef CONFIG_ARM64_64K_PAGES
	int __meminit vmemmap_populate(struct page *start_page,
	unsigned long size, int node)
	{
	return vmemmap_populate_basepages(start_page, size, node);
	}
	#else /* !CONFIG_ARM64_64K_PAGES */
	int __meminit vmemmap_populate(struct page *start_page,
	unsigned long size, int node)
	{
	unsigned long addr = (unsigned long)start_page;
	unsigned long end = (unsigned long)(start_page + size);
	unsigned long next;
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;

	do {
	next = pmd_addr_end(addr, end);

	pgd = vmemmap_pgd_populate(addr, node);
	if (!pgd)
	return -ENOMEM;

	pud = vmemmap_pud_populate(pgd, addr, node);
	if (!pud)
	return -ENOMEM;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd)) {
	void *p = NULL;

	p = vmemmap_alloc_block_buf(PMD_SIZE, node);
	if (!p)
	return -ENOMEM;

	set_pmd(pmd, __pmd(__pa(p) \| prot_sect_kernel));
	} else
	vmemmap_verify((pte_t *)pmd, node, addr, next);
	} while (addr = next, addr != end);

	return 0;
	}
	#endif /* CONFIG_ARM64_64K_PAGES */
	void vmemmap_free(struct page *memmap, unsigned long nr_pages)
	{
	}
	#endif /* CONFIG_SPARSEMEM_VMEMMAP */