arch/arm64/mm/mmu.c - kernel/msm-4.19 - 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/fixmap.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/sizes.h>
 #include <asm/tlb.h>
 #include <asm/memblock.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 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,
 				  pgprot_t prot)
 {
 	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, prot));
 		pfn++;
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }

 static void __init alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 				  unsigned long addr, unsigned long end,
 				  phys_addr_t phys, pgprot_t prot)
 {
 	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(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) {
 			pmd_t old_pmd =*pmd;
 			set_pmd(pmd, __pmd(phys |
 					   pgprot_val(mk_sect_prot(prot))));
 			/*
 			 * Check for previous table entries created during
 			 * boot (__create_page_tables) and flush them.
 			 */
 			if (!pmd_none(old_pmd))
 				flush_tlb_all();
 		} else {
 			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
 				       prot);
 		}
 		phys += next - addr;
 	} while (pmd++, addr = next, addr != end);
 }

 static void __init alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 				  unsigned long addr, unsigned long end,
 				  phys_addr_t phys, pgprot_t prot)
 {
 	pud_t *pud;
 	unsigned long next;

 	if (pgd_none(*pgd)) {
 		pud = early_alloc(PTRS_PER_PUD * sizeof(pud_t));
 		pgd_populate(mm, pgd, pud);
 	}
 	BUG_ON(pgd_bad(*pgd));

 	pud = pud_offset(pgd, addr);
 	do {
 		next = pud_addr_end(addr, end);

 		/*
 		 * For 4K granule only, attempt to put down a 1GB block
 		 */
 		if ((PAGE_SHIFT == 12) &&
 		    ((addr | next | phys) & ~PUD_MASK) == 0) {
 			pud_t old_pud = *pud;
 			set_pud(pud, __pud(phys |
 					   pgprot_val(mk_sect_prot(prot))));

 			/*
 			 * If we have an old value for a pud, it will
 			 * be pointing to a pmd table that we no longer
 			 * need (from swapper_pg_dir).
 			 *
 			 * Look up the old pmd table and free it.
 			 */
 			if (!pud_none(old_pud)) {
 				phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
 				memblock_free(table, PAGE_SIZE);
 				flush_tlb_all();
 			}
 		} else {
 			alloc_init_pmd(mm, pud, addr, next, phys, prot);
 		}
 		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(struct mm_struct *mm, pgd_t *pgd,
 				    phys_addr_t phys, unsigned long virt,
 				    phys_addr_t size, pgprot_t prot)
 {
 	unsigned long addr, length, end, next;

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

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

 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 				  phys_addr_t size)
 {
 	if (virt < VMALLOC_START) {
 		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 			&phys, virt);
 		return;
 	}
 	__create_mapping(&init_mm, pgd_offset_k(virt & PAGE_MASK), phys, virt,
 			 size, PAGE_KERNEL_EXEC);
 }

 void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			       unsigned long virt, phys_addr_t size,
 			       pgprot_t prot)
 {
 	__create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, prot);
 }

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

 	/*
 	 * Temporarily limit the memblock range. We need to do this as
 	 * create_mapping requires puds, pmds and ptes to be allocated from
 	 * memory addressable from the initial direct kernel mapping.
 	 *
 	 * The initial direct kernel mapping, located at swapper_pg_dir, gives
 	 * us PUD_SIZE (4K pages) or PMD_SIZE (64K pages) memory starting from
 	 * PHYS_OFFSET (which must be aligned to 2MB as per
 	 * Documentation/arm64/booting.txt).
 	 */
 	if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
 		limit = PHYS_OFFSET + PMD_SIZE;
 	else
 		limit = PHYS_OFFSET + PUD_SIZE;
 	memblock_set_current_limit(limit);

 	/* 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;

 #ifndef CONFIG_ARM64_64K_PAGES
 		/*
 		 * For the first memory bank align the start address and
 		 * current memblock limit to prevent create_mapping() from
 		 * allocating pte page tables from unmapped memory.
 		 * When 64K pages are enabled, the pte page table for the
 		 * first PGDIR_SIZE is already present in swapper_pg_dir.
 		 */
 		if (start < limit)
 			start = ALIGN(start, PMD_SIZE);
 		if (end < limit) {
 			limit = end & PMD_MASK;
 			memblock_set_current_limit(limit);
 		}
 #endif

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

 	/* Limit no longer required. */
 	memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
 }

 /*
  * 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;

 	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);

 	/*
 	 * 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;

 	if (pud_sect(*pud))
 		return pfn_valid(pud_pfn(*pud));

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

 	if (pmd_sect(*pmd))
 		return pfn_valid(pmd_pfn(*pmd));

 	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(unsigned long start, unsigned long end, int node)
 {
 	return vmemmap_populate_basepages(start, end, node);
 }
 #else	/* !CONFIG_ARM64_64K_PAGES */
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 {
 	unsigned long addr = start;
 	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_NORMAL));
 		} else
 			vmemmap_verify((pte_t *)pmd, node, addr, next);
 	} while (addr = next, addr != end);

 	return 0;
 }
 #endif	/* CONFIG_ARM64_64K_PAGES */
 void vmemmap_free(unsigned long start, unsigned long end)
 {
 }
 #endif	/* CONFIG_SPARSEMEM_VMEMMAP */

 static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
 #if CONFIG_ARM64_PGTABLE_LEVELS > 2
 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
 #endif
 #if CONFIG_ARM64_PGTABLE_LEVELS > 3
 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
 #endif

 static inline pud_t * fixmap_pud(unsigned long addr)
 {
 	pgd_t *pgd = pgd_offset_k(addr);

 	BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));

 	return pud_offset(pgd, addr);
 }

 static inline pmd_t * fixmap_pmd(unsigned long addr)
 {
 	pud_t *pud = fixmap_pud(addr);

 	BUG_ON(pud_none(*pud) || pud_bad(*pud));

 	return pmd_offset(pud, addr);
 }

 static inline pte_t * fixmap_pte(unsigned long addr)
 {
 	pmd_t *pmd = fixmap_pmd(addr);

 	BUG_ON(pmd_none(*pmd) || pmd_bad(*pmd));

 	return pte_offset_kernel(pmd, addr);
 }

 void __init early_fixmap_init(void)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	unsigned long addr = FIXADDR_START;

 	pgd = pgd_offset_k(addr);
 	pgd_populate(&init_mm, pgd, bm_pud);
 	pud = pud_offset(pgd, addr);
 	pud_populate(&init_mm, pud, bm_pmd);
 	pmd = pmd_offset(pud, addr);
 	pmd_populate_kernel(&init_mm, pmd, bm_pte);

 	/*
 	 * The boot-ioremap range spans multiple pmds, for which
 	 * we are not preparted:
 	 */
 	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
 		     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));

 	if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
 	     || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
 		WARN_ON(1);
 		pr_warn("pmd %p != %p, %p\n",
 			pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
 			fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
 		pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
 			fix_to_virt(FIX_BTMAP_BEGIN));
 		pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
 			fix_to_virt(FIX_BTMAP_END));

 		pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
 		pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
 	}
 }

 void __set_fixmap(enum fixed_addresses idx,
 			       phys_addr_t phys, pgprot_t flags)
 {
 	unsigned long addr = __fix_to_virt(idx);
 	pte_t *pte;

 	if (idx >= __end_of_fixed_addresses) {
 		BUG();
 		return;
 	}

 	pte = fixmap_pte(addr);

 	if (pgprot_val(flags)) {
 		set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
 	} else {
 		pte_clear(&init_mm, addr, pte);
 		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 	}
 }
	/*
	* 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/fixmap.h>
	#include <asm/sections.h>
	#include <asm/setup.h>
	#include <asm/sizes.h>
	#include <asm/tlb.h>
	#include <asm/memblock.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 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,
	pgprot_t prot)
	{
	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, prot));
	pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	}

	static void __init alloc_init_pmd(struct mm_struct mm, pud_t pud,
	unsigned long addr, unsigned long end,
	phys_addr_t phys, pgprot_t prot)
	{
	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(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) {
	pmd_t old_pmd =*pmd;
	set_pmd(pmd, __pmd(phys \|
	pgprot_val(mk_sect_prot(prot))));
	/*
	* Check for previous table entries created during
	* boot (__create_page_tables) and flush them.
	*/
	if (!pmd_none(old_pmd))
	flush_tlb_all();
	} else {
	alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
	prot);
	}
	phys += next - addr;
	} while (pmd++, addr = next, addr != end);
	}

	static void __init alloc_init_pud(struct mm_struct mm, pgd_t pgd,
	unsigned long addr, unsigned long end,
	phys_addr_t phys, pgprot_t prot)
	{
	pud_t *pud;
	unsigned long next;

	if (pgd_none(*pgd)) {
	pud = early_alloc(PTRS_PER_PUD * sizeof(pud_t));
	pgd_populate(mm, pgd, pud);
	}
	BUG_ON(pgd_bad(*pgd));

	pud = pud_offset(pgd, addr);
	do {
	next = pud_addr_end(addr, end);

	/*
	* For 4K granule only, attempt to put down a 1GB block
	*/
	if ((PAGE_SHIFT == 12) &&
	((addr \| next \| phys) & ~PUD_MASK) == 0) {
	pud_t old_pud = *pud;
	set_pud(pud, __pud(phys \|
	pgprot_val(mk_sect_prot(prot))));

	/*
	* If we have an old value for a pud, it will
	* be pointing to a pmd table that we no longer
	* need (from swapper_pg_dir).
	*
	* Look up the old pmd table and free it.
	*/
	if (!pud_none(old_pud)) {
	phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
	memblock_free(table, PAGE_SIZE);
	flush_tlb_all();
	}
	} else {
	alloc_init_pmd(mm, pud, addr, next, phys, prot);
	}
	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(struct mm_struct mm, pgd_t pgd,
	phys_addr_t phys, unsigned long virt,
	phys_addr_t size, pgprot_t prot)
	{
	unsigned long addr, length, end, next;

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

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

	static void __init create_mapping(phys_addr_t phys, unsigned long virt,
	phys_addr_t size)
	{
	if (virt < VMALLOC_START) {
	pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
	&phys, virt);
	return;
	}
	__create_mapping(&init_mm, pgd_offset_k(virt & PAGE_MASK), phys, virt,
	size, PAGE_KERNEL_EXEC);
	}

	void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
	unsigned long virt, phys_addr_t size,
	pgprot_t prot)
	{
	__create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, prot);
	}

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

	/*
	* Temporarily limit the memblock range. We need to do this as
	* create_mapping requires puds, pmds and ptes to be allocated from
	* memory addressable from the initial direct kernel mapping.
	*
	* The initial direct kernel mapping, located at swapper_pg_dir, gives
	* us PUD_SIZE (4K pages) or PMD_SIZE (64K pages) memory starting from
	* PHYS_OFFSET (which must be aligned to 2MB as per
	* Documentation/arm64/booting.txt).
	*/
	if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
	limit = PHYS_OFFSET + PMD_SIZE;
	else
	limit = PHYS_OFFSET + PUD_SIZE;
	memblock_set_current_limit(limit);

	/* 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;

	#ifndef CONFIG_ARM64_64K_PAGES
	/*
	* For the first memory bank align the start address and
	* current memblock limit to prevent create_mapping() from
	* allocating pte page tables from unmapped memory.
	* When 64K pages are enabled, the pte page table for the
	* first PGDIR_SIZE is already present in swapper_pg_dir.
	*/
	if (start < limit)
	start = ALIGN(start, PMD_SIZE);
	if (end < limit) {
	limit = end & PMD_MASK;
	memblock_set_current_limit(limit);
	}
	#endif

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

	/* Limit no longer required. */
	memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
	}

	/*
	* 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;

	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);

	/*
	* 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;

	if (pud_sect(*pud))
	return pfn_valid(pud_pfn(*pud));

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

	if (pmd_sect(*pmd))
	return pfn_valid(pmd_pfn(*pmd));

	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(unsigned long start, unsigned long end, int node)
	{
	return vmemmap_populate_basepages(start, end, node);
	}
	#else /* !CONFIG_ARM64_64K_PAGES */
	int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
	{
	unsigned long addr = start;
	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_NORMAL));
	} else
	vmemmap_verify((pte_t *)pmd, node, addr, next);
	} while (addr = next, addr != end);

	return 0;
	}
	#endif /* CONFIG_ARM64_64K_PAGES */
	void vmemmap_free(unsigned long start, unsigned long end)
	{
	}
	#endif /* CONFIG_SPARSEMEM_VMEMMAP */

	static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
	#if CONFIG_ARM64_PGTABLE_LEVELS > 2
	static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
	#endif
	#if CONFIG_ARM64_PGTABLE_LEVELS > 3
	static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
	#endif

	static inline pud_t * fixmap_pud(unsigned long addr)
	{
	pgd_t *pgd = pgd_offset_k(addr);

	BUG_ON(pgd_none(pgd) \|\| pgd_bad(pgd));

	return pud_offset(pgd, addr);
	}

	static inline pmd_t * fixmap_pmd(unsigned long addr)
	{
	pud_t *pud = fixmap_pud(addr);

	BUG_ON(pud_none(pud) \|\| pud_bad(pud));

	return pmd_offset(pud, addr);
	}

	static inline pte_t * fixmap_pte(unsigned long addr)
	{
	pmd_t *pmd = fixmap_pmd(addr);

	BUG_ON(pmd_none(pmd) \|\| pmd_bad(pmd));

	return pte_offset_kernel(pmd, addr);
	}

	void __init early_fixmap_init(void)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	unsigned long addr = FIXADDR_START;

	pgd = pgd_offset_k(addr);
	pgd_populate(&init_mm, pgd, bm_pud);
	pud = pud_offset(pgd, addr);
	pud_populate(&init_mm, pud, bm_pmd);
	pmd = pmd_offset(pud, addr);
	pmd_populate_kernel(&init_mm, pmd, bm_pte);

	/*
	* The boot-ioremap range spans multiple pmds, for which
	* we are not preparted:
	*/
	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
	!= (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));

	if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
	\|\| pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
	WARN_ON(1);
	pr_warn("pmd %p != %p, %p\n",
	pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
	fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
	pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
	fix_to_virt(FIX_BTMAP_BEGIN));
	pr_warn("fix_to_virt(FIX_BTMAP_END): %08lx\n",
	fix_to_virt(FIX_BTMAP_END));

	pr_warn("FIX_BTMAP_END: %d\n", FIX_BTMAP_END);
	pr_warn("FIX_BTMAP_BEGIN: %d\n", FIX_BTMAP_BEGIN);
	}
	}

	void __set_fixmap(enum fixed_addresses idx,
	phys_addr_t phys, pgprot_t flags)
	{
	unsigned long addr = __fix_to_virt(idx);
	pte_t *pte;

	if (idx >= __end_of_fixed_addresses) {
	BUG();
	return;
	}

	pte = fixmap_pte(addr);

	if (pgprot_val(flags)) {
	set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
	} else {
	pte_clear(&init_mm, addr, pte);
	flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
	}
	}