arch/unicore32/mm/mmu.c - kernel/msm-4.9 - Gitiles

 /*
  * linux/arch/unicore32/mm/mmu.c
  *
  * Code specific to PKUnity SoC and UniCore ISA
  *
  * Copyright (C) 2001-2010 GUAN Xue-tao
  *
  * 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.
  */
 #include <linux/module.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/bootmem.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 <mach/map.h>

 #include "mm.h"

 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);

 /*
  * 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);

 /*
  * The pmd table for the upper-most set of pages.
  */
 pmd_t *top_pmd;

 pgprot_t pgprot_user;
 EXPORT_SYMBOL(pgprot_user);

 pgprot_t pgprot_kernel;
 EXPORT_SYMBOL(pgprot_kernel);

 static int __init noalign_setup(char *__unused)
 {
 	cr_alignment &= ~CR_A;
 	cr_no_alignment &= ~CR_A;
 	set_cr(cr_alignment);
 	return 1;
 }
 __setup("noalign", noalign_setup);

 void adjust_cr(unsigned long mask, unsigned long set)
 {
 	unsigned long flags;

 	mask &= ~CR_A;

 	set &= mask;

 	local_irq_save(flags);

 	cr_no_alignment = (cr_no_alignment & ~mask) | set;
 	cr_alignment = (cr_alignment & ~mask) | set;

 	set_cr((get_cr() & ~mask) | set);

 	local_irq_restore(flags);
 }

 struct map_desc {
 	unsigned long virtual;
 	unsigned long pfn;
 	unsigned long length;
 	unsigned int type;
 };

 #define PROT_PTE_DEVICE		(PTE_PRESENT | PTE_YOUNG |	\
 				PTE_DIRTY | PTE_READ | PTE_WRITE)
 #define PROT_SECT_DEVICE	(PMD_TYPE_SECT | PMD_PRESENT |	\
 				PMD_SECT_READ | PMD_SECT_WRITE)

 static struct mem_type mem_types[] = {
 	[MT_DEVICE] = {		  /* Strongly ordered */
 		.prot_pte	= PROT_PTE_DEVICE,
 		.prot_l1	= PMD_TYPE_TABLE | PMD_PRESENT,
 		.prot_sect	= PROT_SECT_DEVICE,
 	},
 	/*
 	 * MT_KUSER: pte for vecpage -- cacheable,
 	 *       and sect for unigfx mmap -- noncacheable
 	 */
 	[MT_KUSER] = {
 		.prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
 				PTE_CACHEABLE | PTE_READ | PTE_EXEC,
 		.prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
 		.prot_sect = PROT_SECT_DEVICE,
 	},
 	[MT_HIGH_VECTORS] = {
 		.prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
 				PTE_CACHEABLE | PTE_READ | PTE_WRITE |
 				PTE_EXEC,
 		.prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
 	},
 	[MT_MEMORY] = {
 		.prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
 				PTE_WRITE | PTE_EXEC,
 		.prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
 		.prot_sect = PMD_TYPE_SECT | PMD_PRESENT | PMD_SECT_CACHEABLE |
 				PMD_SECT_READ | PMD_SECT_WRITE | PMD_SECT_EXEC,
 	},
 	[MT_ROM] = {
 		.prot_sect = PMD_TYPE_SECT | PMD_PRESENT | PMD_SECT_CACHEABLE |
 				PMD_SECT_READ,
 	},
 };

 const struct mem_type *get_mem_type(unsigned int type)
 {
 	return type < ARRAY_SIZE(mem_types) ? &mem_types[type] : NULL;
 }
 EXPORT_SYMBOL(get_mem_type);

 /*
  * Adjust the PMD section entries according to the CPU in use.
  */
 static void __init build_mem_type_table(void)
 {
 	pgprot_user   = __pgprot(PTE_PRESENT | PTE_YOUNG | PTE_CACHEABLE);
 	pgprot_kernel = __pgprot(PTE_PRESENT | PTE_YOUNG |
 				 PTE_DIRTY | PTE_READ | PTE_WRITE |
 				 PTE_EXEC | PTE_CACHEABLE);
 }

 #define vectors_base()	(vectors_high() ? 0xffff0000 : 0)

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

 static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr,
 		unsigned long prot)
 {
 	if (pmd_none(*pmd)) {
 		pte_t *pte = early_alloc(PTRS_PER_PTE * sizeof(pte_t));
 		__pmd_populate(pmd, __pa(pte) | prot);
 	}
 	BUG_ON(pmd_bad(*pmd));
 	return pte_offset_kernel(pmd, addr);
 }

 static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
 				  unsigned long end, unsigned long pfn,
 				  const struct mem_type *type)
 {
 	pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1);
 	do {
 		set_pte(pte, pfn_pte(pfn, __pgprot(type->prot_pte)));
 		pfn++;
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }

 static void __init alloc_init_section(pgd_t *pgd, unsigned long addr,
 				      unsigned long end, unsigned long phys,
 				      const struct mem_type *type)
 {
 	pmd_t *pmd = pmd_offset((pud_t *)pgd, addr);

 	/*
 	 * Try a section mapping - end, addr and phys must all be aligned
 	 * to a section boundary.
 	 */
 	if (((addr | end | phys) & ~SECTION_MASK) == 0) {
 		pmd_t *p = pmd;

 		do {
 			set_pmd(pmd, __pmd(phys | type->prot_sect));
 			phys += SECTION_SIZE;
 		} while (pmd++, addr += SECTION_SIZE, addr != end);

 		flush_pmd_entry(p);
 	} else {
 		/*
 		 * No need to loop; pte's aren't interested in the
 		 * individual L1 entries.
 		 */
 		alloc_init_pte(pmd, addr, end, __phys_to_pfn(phys), type);
 	}
 }

 /*
  * Create the page directory entries and any necessary
  * page tables for the mapping specified by `md'.  We
  * are able to cope here with varying sizes and address
  * offsets, and we take full advantage of sections.
  */
 static void __init create_mapping(struct map_desc *md)
 {
 	unsigned long phys, addr, length, end;
 	const struct mem_type *type;
 	pgd_t *pgd;

 	if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
 		printk(KERN_WARNING "BUG: not creating mapping for "
 		       "0x%08llx at 0x%08lx in user region\n",
 		       __pfn_to_phys((u64)md->pfn), md->virtual);
 		return;
 	}

 	if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
 	    md->virtual >= PAGE_OFFSET && md->virtual < VMALLOC_END) {
 		printk(KERN_WARNING "BUG: mapping for 0x%08llx at 0x%08lx "
 		       "overlaps vmalloc space\n",
 		       __pfn_to_phys((u64)md->pfn), md->virtual);
 	}

 	type = &mem_types[md->type];

 	addr = md->virtual & PAGE_MASK;
 	phys = (unsigned long)__pfn_to_phys(md->pfn);
 	length = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));

 	if (type->prot_l1 == 0 && ((addr | phys | length) & ~SECTION_MASK)) {
 		printk(KERN_WARNING "BUG: map for 0x%08lx at 0x%08lx can not "
 		       "be mapped using pages, ignoring.\n",
 		       __pfn_to_phys(md->pfn), addr);
 		return;
 	}

 	pgd = pgd_offset_k(addr);
 	end = addr + length;
 	do {
 		unsigned long next = pgd_addr_end(addr, end);

 		alloc_init_section(pgd, addr, next, phys, type);

 		phys += next - addr;
 		addr = next;
 	} while (pgd++, addr != end);
 }

 static void * __initdata vmalloc_min = (void *)(VMALLOC_END - SZ_128M);

 /*
  * vmalloc=size forces the vmalloc area to be exactly 'size'
  * bytes. This can be used to increase (or decrease) the vmalloc
  * area - the default is 128m.
  */
 static int __init early_vmalloc(char *arg)
 {
 	unsigned long vmalloc_reserve = memparse(arg, NULL);

 	if (vmalloc_reserve < SZ_16M) {
 		vmalloc_reserve = SZ_16M;
 		printk(KERN_WARNING
 			"vmalloc area too small, limiting to %luMB\n",
 			vmalloc_reserve >> 20);
 	}

 	if (vmalloc_reserve > VMALLOC_END - (PAGE_OFFSET + SZ_32M)) {
 		vmalloc_reserve = VMALLOC_END - (PAGE_OFFSET + SZ_32M);
 		printk(KERN_WARNING
 			"vmalloc area is too big, limiting to %luMB\n",
 			vmalloc_reserve >> 20);
 	}

 	vmalloc_min = (void *)(VMALLOC_END - vmalloc_reserve);
 	return 0;
 }
 early_param("vmalloc", early_vmalloc);

 static phys_addr_t lowmem_limit __initdata = SZ_1G;

 static void __init sanity_check_meminfo(void)
 {
 	int i, j;

 	lowmem_limit = __pa(vmalloc_min - 1) + 1;
 	memblock_set_current_limit(lowmem_limit);

 	for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
 		struct membank *bank = &meminfo.bank[j];
 		*bank = meminfo.bank[i];
 		j++;
 	}
 	meminfo.nr_banks = j;
 }

 static inline void prepare_page_table(void)
 {
 	unsigned long addr;
 	phys_addr_t end;

 	/*
 	 * Clear out all the mappings below the kernel image.
 	 */
 	for (addr = 0; addr < MODULES_VADDR; addr += PGDIR_SIZE)
 		pmd_clear(pmd_off_k(addr));

 	for ( ; addr < PAGE_OFFSET; addr += PGDIR_SIZE)
 		pmd_clear(pmd_off_k(addr));

 	/*
 	 * Find the end of the first block of lowmem.
 	 */
 	end = memblock.memory.regions[0].base + memblock.memory.regions[0].size;
 	if (end >= lowmem_limit)
 		end = lowmem_limit;

 	/*
 	 * Clear out all the kernel space mappings, except for the first
 	 * memory bank, up to the end of the vmalloc region.
 	 */
 	for (addr = __phys_to_virt(end);
 	     addr < VMALLOC_END; addr += PGDIR_SIZE)
 		pmd_clear(pmd_off_k(addr));
 }

 /*
  * Reserve the special regions of memory
  */
 void __init uc32_mm_memblock_reserve(void)
 {
 	/*
 	 * Reserve the page tables.  These are already in use,
 	 * and can only be in node 0.
 	 */
 	memblock_reserve(__pa(swapper_pg_dir), PTRS_PER_PGD * sizeof(pgd_t));
 }

 /*
  * Set up device the mappings.  Since we clear out the page tables for all
  * mappings above VMALLOC_END, we will remove any debug device mappings.
  * This means you have to be careful how you debug this function, or any
  * called function.  This means you can't use any function or debugging
  * method which may touch any device, otherwise the kernel _will_ crash.
  */
 static void __init devicemaps_init(void)
 {
 	struct map_desc map;
 	unsigned long addr;
 	void *vectors;

 	/*
 	 * Allocate the vector page early.
 	 */
 	vectors = early_alloc(PAGE_SIZE);

 	for (addr = VMALLOC_END; addr; addr += PGDIR_SIZE)
 		pmd_clear(pmd_off_k(addr));

 	/*
 	 * Create a mapping for the machine vectors at the high-vectors
 	 * location (0xffff0000).  If we aren't using high-vectors, also
 	 * create a mapping at the low-vectors virtual address.
 	 */
 	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
 	map.virtual = VECTORS_BASE;
 	map.length = PAGE_SIZE;
 	map.type = MT_HIGH_VECTORS;
 	create_mapping(&map);

 	/*
 	 * Create a mapping for the kuser page at the special
 	 * location (0xbfff0000) to the same vectors location.
 	 */
 	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
 	map.virtual = KUSER_VECPAGE_BASE;
 	map.length = PAGE_SIZE;
 	map.type = MT_KUSER;
 	create_mapping(&map);

 	/*
 	 * Finally flush the caches and tlb to ensure that we're in a
 	 * consistent state wrt the writebuffer.  This also ensures that
 	 * any write-allocated cache lines in the vector page are written
 	 * back.  After this point, we can start to touch devices again.
 	 */
 	local_flush_tlb_all();
 	flush_cache_all();
 }

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

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

 		if (end > lowmem_limit)
 			end = lowmem_limit;
 		if (start >= end)
 			break;

 		map.pfn = __phys_to_pfn(start);
 		map.virtual = __phys_to_virt(start);
 		map.length = end - start;
 		map.type = MT_MEMORY;

 		create_mapping(&map);
 	}
 }

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

 	build_mem_type_table();
 	sanity_check_meminfo();
 	prepare_page_table();
 	map_lowmem();
 	devicemaps_init();

 	top_pmd = pmd_off_k(0xffff0000);

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

 	bootmem_init();

 	empty_zero_page = virt_to_page(zero_page);
 	__flush_dcache_page(NULL, empty_zero_page);
 }

 /*
  * In order to soft-boot, we need to insert a 1:1 mapping in place of
  * the user-mode pages.  This will then ensure that we have predictable
  * results when turning the mmu off
  */
 void setup_mm_for_reboot(char mode)
 {
 	unsigned long base_pmdval;
 	pgd_t *pgd;
 	int i;

 	/*
 	 * We need to access to user-mode page tables here. For kernel threads
 	 * we don't have any user-mode mappings so we use the context that we
 	 * "borrowed".
 	 */
 	pgd = current->active_mm->pgd;

 	base_pmdval = PMD_SECT_WRITE | PMD_SECT_READ | PMD_TYPE_SECT;

 	for (i = 0; i < FIRST_USER_PGD_NR + USER_PTRS_PER_PGD; i++, pgd++) {
 		unsigned long pmdval = (i << PGDIR_SHIFT) | base_pmdval;
 		pmd_t *pmd;

 		pmd = pmd_off(pgd, i << PGDIR_SHIFT);
 		set_pmd(pmd, __pmd(pmdval));
 		flush_pmd_entry(pmd);
 	}

 	local_flush_tlb_all();
 }

 /*
  * Take care of architecture specific things when placing a new PTE into
  * a page table, or changing an existing PTE.  Basically, there are two
  * things that we need to take care of:
  *
  *  1. If PG_dcache_clean is not set for the page, we need to ensure
  *     that any cache entries for the kernels virtual memory
  *     range are written back to the page.
  *  2. If we have multiple shared mappings of the same space in
  *     an object, we need to deal with the cache aliasing issues.
  *
  * Note that the pte lock will be held.
  */
 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
 	pte_t *ptep)
 {
 	unsigned long pfn = pte_pfn(*ptep);
 	struct address_space *mapping;
 	struct page *page;

 	if (!pfn_valid(pfn))
 		return;

 	/*
 	 * The zero page is never written to, so never has any dirty
 	 * cache lines, and therefore never needs to be flushed.
 	 */
 	page = pfn_to_page(pfn);
 	if (page == ZERO_PAGE(0))
 		return;

 	mapping = page_mapping(page);
 	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
 		__flush_dcache_page(mapping, page);
 	if (mapping)
 		if (vma->vm_flags & VM_EXEC)
 			__flush_icache_all();
 }
	/*
	* linux/arch/unicore32/mm/mmu.c
	*
	* Code specific to PKUnity SoC and UniCore ISA
	*
	* Copyright (C) 2001-2010 GUAN Xue-tao
	*
	* 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.
	*/
	#include <linux/module.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/bootmem.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 <mach/map.h>

	#include "mm.h"

	DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);

	/*
	* 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);

	/*
	* The pmd table for the upper-most set of pages.
	*/
	pmd_t *top_pmd;

	pgprot_t pgprot_user;
	EXPORT_SYMBOL(pgprot_user);

	pgprot_t pgprot_kernel;
	EXPORT_SYMBOL(pgprot_kernel);

	static int __init noalign_setup(char *__unused)
	{
	cr_alignment &= ~CR_A;
	cr_no_alignment &= ~CR_A;
	set_cr(cr_alignment);
	return 1;
	}
	__setup("noalign", noalign_setup);

	void adjust_cr(unsigned long mask, unsigned long set)
	{
	unsigned long flags;

	mask &= ~CR_A;

	set &= mask;

	local_irq_save(flags);

	cr_no_alignment = (cr_no_alignment & ~mask) \| set;
	cr_alignment = (cr_alignment & ~mask) \| set;

	set_cr((get_cr() & ~mask) \| set);

	local_irq_restore(flags);
	}

	struct map_desc {
	unsigned long virtual;
	unsigned long pfn;
	unsigned long length;
	unsigned int type;
	};

	#define PROT_PTE_DEVICE (PTE_PRESENT \| PTE_YOUNG \| \
	PTE_DIRTY \| PTE_READ \| PTE_WRITE)
	#define PROT_SECT_DEVICE (PMD_TYPE_SECT \| PMD_PRESENT \| \
	PMD_SECT_READ \| PMD_SECT_WRITE)

	static struct mem_type mem_types[] = {
	[MT_DEVICE] = { /* Strongly ordered */
	.prot_pte = PROT_PTE_DEVICE,
	.prot_l1 = PMD_TYPE_TABLE \| PMD_PRESENT,
	.prot_sect = PROT_SECT_DEVICE,
	},
	/*
	* MT_KUSER: pte for vecpage -- cacheable,
	* and sect for unigfx mmap -- noncacheable
	*/
	[MT_KUSER] = {
	.prot_pte = PTE_PRESENT \| PTE_YOUNG \| PTE_DIRTY \|
	PTE_CACHEABLE \| PTE_READ \| PTE_EXEC,
	.prot_l1 = PMD_TYPE_TABLE \| PMD_PRESENT,
	.prot_sect = PROT_SECT_DEVICE,
	},
	[MT_HIGH_VECTORS] = {
	.prot_pte = PTE_PRESENT \| PTE_YOUNG \| PTE_DIRTY \|
	PTE_CACHEABLE \| PTE_READ \| PTE_WRITE \|
	PTE_EXEC,
	.prot_l1 = PMD_TYPE_TABLE \| PMD_PRESENT,
	},
	[MT_MEMORY] = {
	.prot_pte = PTE_PRESENT \| PTE_YOUNG \| PTE_DIRTY \|
	PTE_WRITE \| PTE_EXEC,
	.prot_l1 = PMD_TYPE_TABLE \| PMD_PRESENT,
	.prot_sect = PMD_TYPE_SECT \| PMD_PRESENT \| PMD_SECT_CACHEABLE \|
	PMD_SECT_READ \| PMD_SECT_WRITE \| PMD_SECT_EXEC,
	},
	[MT_ROM] = {
	.prot_sect = PMD_TYPE_SECT \| PMD_PRESENT \| PMD_SECT_CACHEABLE \|
	PMD_SECT_READ,
	},
	};

	const struct mem_type *get_mem_type(unsigned int type)
	{
	return type < ARRAY_SIZE(mem_types) ? &mem_types[type] : NULL;
	}
	EXPORT_SYMBOL(get_mem_type);

	/*
	* Adjust the PMD section entries according to the CPU in use.
	*/
	static void __init build_mem_type_table(void)
	{
	pgprot_user = __pgprot(PTE_PRESENT \| PTE_YOUNG \| PTE_CACHEABLE);
	pgprot_kernel = __pgprot(PTE_PRESENT \| PTE_YOUNG \|
	PTE_DIRTY \| PTE_READ \| PTE_WRITE \|
	PTE_EXEC \| PTE_CACHEABLE);
	}

	#define vectors_base() (vectors_high() ? 0xffff0000 : 0)

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

	static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr,
	unsigned long prot)
	{
	if (pmd_none(*pmd)) {
	pte_t pte = early_alloc(PTRS_PER_PTE sizeof(pte_t));
	__pmd_populate(pmd, __pa(pte) \| prot);
	}
	BUG_ON(pmd_bad(*pmd));
	return pte_offset_kernel(pmd, addr);
	}

	static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
	unsigned long end, unsigned long pfn,
	const struct mem_type *type)
	{
	pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1);
	do {
	set_pte(pte, pfn_pte(pfn, __pgprot(type->prot_pte)));
	pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	}

	static void __init alloc_init_section(pgd_t *pgd, unsigned long addr,
	unsigned long end, unsigned long phys,
	const struct mem_type *type)
	{
	pmd_t pmd = pmd_offset((pud_t )pgd, addr);

	/*
	* Try a section mapping - end, addr and phys must all be aligned
	* to a section boundary.
	*/
	if (((addr \| end \| phys) & ~SECTION_MASK) == 0) {
	pmd_t *p = pmd;

	do {
	set_pmd(pmd, __pmd(phys \| type->prot_sect));
	phys += SECTION_SIZE;
	} while (pmd++, addr += SECTION_SIZE, addr != end);

	flush_pmd_entry(p);
	} else {
	/*
	* No need to loop; pte's aren't interested in the
	* individual L1 entries.
	*/
	alloc_init_pte(pmd, addr, end, __phys_to_pfn(phys), type);
	}
	}

	/*
	* Create the page directory entries and any necessary
	* page tables for the mapping specified by `md'. We
	* are able to cope here with varying sizes and address
	* offsets, and we take full advantage of sections.
	*/
	static void __init create_mapping(struct map_desc *md)
	{
	unsigned long phys, addr, length, end;
	const struct mem_type *type;
	pgd_t *pgd;

	if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
	printk(KERN_WARNING "BUG: not creating mapping for "
	"0x%08llx at 0x%08lx in user region\n",
	__pfn_to_phys((u64)md->pfn), md->virtual);
	return;
	}

	if ((md->type == MT_DEVICE \|\| md->type == MT_ROM) &&
	md->virtual >= PAGE_OFFSET && md->virtual < VMALLOC_END) {
	printk(KERN_WARNING "BUG: mapping for 0x%08llx at 0x%08lx "
	"overlaps vmalloc space\n",
	__pfn_to_phys((u64)md->pfn), md->virtual);
	}

	type = &mem_types[md->type];

	addr = md->virtual & PAGE_MASK;
	phys = (unsigned long)__pfn_to_phys(md->pfn);
	length = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));

	if (type->prot_l1 == 0 && ((addr \| phys \| length) & ~SECTION_MASK)) {
	printk(KERN_WARNING "BUG: map for 0x%08lx at 0x%08lx can not "
	"be mapped using pages, ignoring.\n",
	__pfn_to_phys(md->pfn), addr);
	return;
	}

	pgd = pgd_offset_k(addr);
	end = addr + length;
	do {
	unsigned long next = pgd_addr_end(addr, end);

	alloc_init_section(pgd, addr, next, phys, type);

	phys += next - addr;
	addr = next;
	} while (pgd++, addr != end);
	}

	static void * __initdata vmalloc_min = (void *)(VMALLOC_END - SZ_128M);

	/*
	* vmalloc=size forces the vmalloc area to be exactly 'size'
	* bytes. This can be used to increase (or decrease) the vmalloc
	* area - the default is 128m.
	*/
	static int __init early_vmalloc(char *arg)
	{
	unsigned long vmalloc_reserve = memparse(arg, NULL);

	if (vmalloc_reserve < SZ_16M) {
	vmalloc_reserve = SZ_16M;
	printk(KERN_WARNING
	"vmalloc area too small, limiting to %luMB\n",
	vmalloc_reserve >> 20);
	}

	if (vmalloc_reserve > VMALLOC_END - (PAGE_OFFSET + SZ_32M)) {
	vmalloc_reserve = VMALLOC_END - (PAGE_OFFSET + SZ_32M);
	printk(KERN_WARNING
	"vmalloc area is too big, limiting to %luMB\n",
	vmalloc_reserve >> 20);
	}

	vmalloc_min = (void *)(VMALLOC_END - vmalloc_reserve);
	return 0;
	}
	early_param("vmalloc", early_vmalloc);

	static phys_addr_t lowmem_limit __initdata = SZ_1G;

	static void __init sanity_check_meminfo(void)
	{
	int i, j;

	lowmem_limit = __pa(vmalloc_min - 1) + 1;
	memblock_set_current_limit(lowmem_limit);

	for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
	struct membank *bank = &meminfo.bank[j];
	*bank = meminfo.bank[i];
	j++;
	}
	meminfo.nr_banks = j;
	}

	static inline void prepare_page_table(void)
	{
	unsigned long addr;
	phys_addr_t end;

	/*
	* Clear out all the mappings below the kernel image.
	*/
	for (addr = 0; addr < MODULES_VADDR; addr += PGDIR_SIZE)
	pmd_clear(pmd_off_k(addr));

	for ( ; addr < PAGE_OFFSET; addr += PGDIR_SIZE)
	pmd_clear(pmd_off_k(addr));

	/*
	* Find the end of the first block of lowmem.
	*/
	end = memblock.memory.regions[0].base + memblock.memory.regions[0].size;
	if (end >= lowmem_limit)
	end = lowmem_limit;

	/*
	* Clear out all the kernel space mappings, except for the first
	* memory bank, up to the end of the vmalloc region.
	*/
	for (addr = __phys_to_virt(end);
	addr < VMALLOC_END; addr += PGDIR_SIZE)
	pmd_clear(pmd_off_k(addr));
	}

	/*
	* Reserve the special regions of memory
	*/
	void __init uc32_mm_memblock_reserve(void)
	{
	/*
	* Reserve the page tables. These are already in use,
	* and can only be in node 0.
	*/
	memblock_reserve(__pa(swapper_pg_dir), PTRS_PER_PGD * sizeof(pgd_t));
	}

	/*
	* Set up device the mappings. Since we clear out the page tables for all
	* mappings above VMALLOC_END, we will remove any debug device mappings.
	* This means you have to be careful how you debug this function, or any
	* called function. This means you can't use any function or debugging
	* method which may touch any device, otherwise the kernel _will_ crash.
	*/
	static void __init devicemaps_init(void)
	{
	struct map_desc map;
	unsigned long addr;
	void *vectors;

	/*
	* Allocate the vector page early.
	*/
	vectors = early_alloc(PAGE_SIZE);

	for (addr = VMALLOC_END; addr; addr += PGDIR_SIZE)
	pmd_clear(pmd_off_k(addr));

	/*
	* Create a mapping for the machine vectors at the high-vectors
	* location (0xffff0000). If we aren't using high-vectors, also
	* create a mapping at the low-vectors virtual address.
	*/
	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
	map.virtual = VECTORS_BASE;
	map.length = PAGE_SIZE;
	map.type = MT_HIGH_VECTORS;
	create_mapping(&map);

	/*
	* Create a mapping for the kuser page at the special
	* location (0xbfff0000) to the same vectors location.
	*/
	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
	map.virtual = KUSER_VECPAGE_BASE;
	map.length = PAGE_SIZE;
	map.type = MT_KUSER;
	create_mapping(&map);

	/*
	* Finally flush the caches and tlb to ensure that we're in a
	* consistent state wrt the writebuffer. This also ensures that
	* any write-allocated cache lines in the vector page are written
	* back. After this point, we can start to touch devices again.
	*/
	local_flush_tlb_all();
	flush_cache_all();
	}

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

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

	if (end > lowmem_limit)
	end = lowmem_limit;
	if (start >= end)
	break;

	map.pfn = __phys_to_pfn(start);
	map.virtual = __phys_to_virt(start);
	map.length = end - start;
	map.type = MT_MEMORY;

	create_mapping(&map);
	}
	}

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

	build_mem_type_table();
	sanity_check_meminfo();
	prepare_page_table();
	map_lowmem();
	devicemaps_init();

	top_pmd = pmd_off_k(0xffff0000);

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

	bootmem_init();

	empty_zero_page = virt_to_page(zero_page);
	__flush_dcache_page(NULL, empty_zero_page);
	}

	/*
	* In order to soft-boot, we need to insert a 1:1 mapping in place of
	* the user-mode pages. This will then ensure that we have predictable
	* results when turning the mmu off
	*/
	void setup_mm_for_reboot(char mode)
	{
	unsigned long base_pmdval;
	pgd_t *pgd;
	int i;

	/*
	* We need to access to user-mode page tables here. For kernel threads
	* we don't have any user-mode mappings so we use the context that we
	* "borrowed".
	*/
	pgd = current->active_mm->pgd;

	base_pmdval = PMD_SECT_WRITE \| PMD_SECT_READ \| PMD_TYPE_SECT;

	for (i = 0; i < FIRST_USER_PGD_NR + USER_PTRS_PER_PGD; i++, pgd++) {
	unsigned long pmdval = (i << PGDIR_SHIFT) \| base_pmdval;
	pmd_t *pmd;

	pmd = pmd_off(pgd, i << PGDIR_SHIFT);
	set_pmd(pmd, __pmd(pmdval));
	flush_pmd_entry(pmd);
	}

	local_flush_tlb_all();
	}

	/*
	* Take care of architecture specific things when placing a new PTE into
	* a page table, or changing an existing PTE. Basically, there are two
	* things that we need to take care of:
	*
	* 1. If PG_dcache_clean is not set for the page, we need to ensure
	* that any cache entries for the kernels virtual memory
	* range are written back to the page.
	* 2. If we have multiple shared mappings of the same space in
	* an object, we need to deal with the cache aliasing issues.
	*
	* Note that the pte lock will be held.
	*/
	void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
	pte_t *ptep)
	{
	unsigned long pfn = pte_pfn(*ptep);
	struct address_space *mapping;
	struct page *page;

	if (!pfn_valid(pfn))
	return;

	/*
	* The zero page is never written to, so never has any dirty
	* cache lines, and therefore never needs to be flushed.
	*/
	page = pfn_to_page(pfn);
	if (page == ZERO_PAGE(0))
	return;

	mapping = page_mapping(page);
	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
	__flush_dcache_page(mapping, page);
	if (mapping)
	if (vma->vm_flags & VM_EXEC)
	__flush_icache_all();
	}