/*

   *
   *  Copyright (C) 1995  Linus Torvalds
   *
   *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
   */

  #include <linux/module.h>
  #include <linux/signal.h>
  #include <linux/sched.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/ptrace.h>
  #include <linux/mman.h>
  #include <linux/mm.h>
  #include <linux/hugetlb.h>
  #include <linux/swap.h>
  #include <linux/smp.h>
  #include <linux/init.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>

  #include <linux/pci.h>

  #include <linux/pfn.h>

  #include <linux/poison.h>

  #include <linux/bootmem.h>

  #include <linux/memblock.h>

  #include <linux/proc_fs.h>

  #include <linux/memory_hotplug.h>

  #include <linux/initrd.h>

  #include <linux/cpumask.h>

  #include <linux/gfp.h>

  #include <asm/asm.h>

  #include <asm/bios_ebda.h>

  #include <asm/processor.h>
  #include <asm/system.h>
  #include <asm/uaccess.h>
  #include <asm/pgtable.h>
  #include <asm/dma.h>
  #include <asm/fixmap.h>
  #include <asm/e820.h>
  #include <asm/apic.h>

  #include <asm/bugs.h>

  #include <asm/tlb.h>
  #include <asm/tlbflush.h>

  #include <asm/olpc_ofw.h>

  #include <asm/pgalloc.h>

  #include <asm/sections.h>

  #include <asm/paravirt.h>

  #include <asm/setup.h>

  #include <asm/cacheflush.h>

  #include <asm/page_types.h>

  #include <asm/init.h>

  unsigned long highstart_pfn, highend_pfn;

  static noinline int do_test_wp_bit(void);

  bool __read_mostly __vmalloc_start_set = false;

  static __init void *alloc_low_page(void)

  {

  	unsigned long pfn = pgt_buf_end++;

  	void *adr;

  	if (pfn >= pgt_buf_top)

  		panic("alloc_low_page: ran out of memory");
  
  	adr = __va(pfn * PAGE_SIZE);

  	clear_page(adr);

  	return adr;
  }

  /*
   * Creates a middle page table and puts a pointer to it in the
   * given global directory entry. This only returns the gd entry
   * in non-PAE compilation mode, since the middle layer is folded.
   */
  static pmd_t * __init one_md_table_init(pgd_t *pgd)
  {
  	pud_t *pud;
  	pmd_t *pmd_table;

  #ifdef CONFIG_X86_PAE

  	if (!(pgd_val(*pgd) & _PAGE_PRESENT)) {

  		if (after_bootmem)

  			pmd_table = (pmd_t *)alloc_bootmem_pages(PAGE_SIZE);

  		else

  			pmd_table = (pmd_t *)alloc_low_page();

  		paravirt_alloc_pmd(&init_mm, __pa(pmd_table) >> PAGE_SHIFT);

  		set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
  		pud = pud_offset(pgd, 0);

  		BUG_ON(pmd_table != pmd_offset(pud, 0));

  
  		return pmd_table;

  	}
  #endif

  	pud = pud_offset(pgd, 0);
  	pmd_table = pmd_offset(pud, 0);

  	return pmd_table;
  }
  
  /*
   * Create a page table and place a pointer to it in a middle page

   * directory entry:

   */
  static pte_t * __init one_page_table_init(pmd_t *pmd)
  {

  	if (!(pmd_val(*pmd) & _PAGE_PRESENT)) {

  		pte_t *page_table = NULL;

  		if (after_bootmem) {

  #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_KMEMCHECK)

  			page_table = (pte_t *) alloc_bootmem_pages(PAGE_SIZE);

  #endif

  			if (!page_table)
  				page_table =

  				(pte_t *)alloc_bootmem_pages(PAGE_SIZE);

  		} else
  			page_table = (pte_t *)alloc_low_page();

  		paravirt_alloc_pte(&init_mm, __pa(page_table) >> PAGE_SHIFT);

  		set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));

  		BUG_ON(page_table != pte_offset_kernel(pmd, 0));

  	}

  	return pte_offset_kernel(pmd, 0);
  }

  pmd_t * __init populate_extra_pmd(unsigned long vaddr)

  {
  	int pgd_idx = pgd_index(vaddr);
  	int pmd_idx = pmd_index(vaddr);

  
  	return one_md_table_init(swapper_pg_dir + pgd_idx) + pmd_idx;
  }
  
  pte_t * __init populate_extra_pte(unsigned long vaddr)
  {
  	int pte_idx = pte_index(vaddr);

  	pmd_t *pmd;

  	pmd = populate_extra_pmd(vaddr);
  	return one_page_table_init(pmd) + pte_idx;

  }

  static pte_t *__init page_table_kmap_check(pte_t *pte, pmd_t *pmd,
  					   unsigned long vaddr, pte_t *lastpte)
  {
  #ifdef CONFIG_HIGHMEM
  	/*
  	 * Something (early fixmap) may already have put a pte
  	 * page here, which causes the page table allocation
  	 * to become nonlinear. Attempt to fix it, and if it
  	 * is still nonlinear then we have to bug.
  	 */
  	int pmd_idx_kmap_begin = fix_to_virt(FIX_KMAP_END) >> PMD_SHIFT;
  	int pmd_idx_kmap_end = fix_to_virt(FIX_KMAP_BEGIN) >> PMD_SHIFT;
  
  	if (pmd_idx_kmap_begin != pmd_idx_kmap_end
  	    && (vaddr >> PMD_SHIFT) >= pmd_idx_kmap_begin
  	    && (vaddr >> PMD_SHIFT) <= pmd_idx_kmap_end

  	    && ((__pa(pte) >> PAGE_SHIFT) < pgt_buf_start
  		|| (__pa(pte) >> PAGE_SHIFT) >= pgt_buf_end)) {

  		pte_t *newpte;
  		int i;

  		BUG_ON(after_bootmem);

  		newpte = alloc_low_page();
  		for (i = 0; i < PTRS_PER_PTE; i++)
  			set_pte(newpte + i, pte[i]);
  
  		paravirt_alloc_pte(&init_mm, __pa(newpte) >> PAGE_SHIFT);
  		set_pmd(pmd, __pmd(__pa(newpte)|_PAGE_TABLE));
  		BUG_ON(newpte != pte_offset_kernel(pmd, 0));
  		__flush_tlb_all();
  
  		paravirt_release_pte(__pa(pte) >> PAGE_SHIFT);
  		pte = newpte;
  	}
  	BUG_ON(vaddr < fix_to_virt(FIX_KMAP_BEGIN - 1)
  	       && vaddr > fix_to_virt(FIX_KMAP_END)
  	       && lastpte && lastpte + PTRS_PER_PTE != pte);
  #endif
  	return pte;
  }

  /*

   * This function initializes a certain range of kernel virtual memory

   * with new bootmem page tables, everywhere page tables are missing in
   * the given range.

   *
   * NOTE: The pagetables are allocated contiguous on the physical space
   * so we can cache the place of the first one and move around without

   * checking the pgd every time.
   */

  static void __init
  page_table_range_init(unsigned long start, unsigned long end, pgd_t *pgd_base)

  {

  	int pgd_idx, pmd_idx;
  	unsigned long vaddr;

  	pgd_t *pgd;
  	pmd_t *pmd;

  	pte_t *pte = NULL;

  
  	vaddr = start;
  	pgd_idx = pgd_index(vaddr);
  	pmd_idx = pmd_index(vaddr);
  	pgd = pgd_base + pgd_idx;
  
  	for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd++, pgd_idx++) {

  		pmd = one_md_table_init(pgd);
  		pmd = pmd + pmd_index(vaddr);

  		for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
  							pmd++, pmd_idx++) {

  			pte = page_table_kmap_check(one_page_table_init(pmd),
  			                            pmd, vaddr, pte);

  
  			vaddr += PMD_SIZE;
  		}
  		pmd_idx = 0;
  	}
  }
  
  static inline int is_kernel_text(unsigned long addr)
  {

  	if (addr >= (unsigned long)_text && addr <= (unsigned long)__init_end)

  		return 1;
  	return 0;
  }
  
  /*

   * This maps the physical memory to kernel virtual address space, a total
   * of max_low_pfn pages, by creating page tables starting from address
   * PAGE_OFFSET:

   */

  unsigned long __init
  kernel_physical_mapping_init(unsigned long start,
  			     unsigned long end,
  			     unsigned long page_size_mask)

  {

  	int use_pse = page_size_mask == (1<<PG_LEVEL_2M);

  	unsigned long last_map_addr = end;

  	unsigned long start_pfn, end_pfn;

  	pgd_t *pgd_base = swapper_pg_dir;

  	int pgd_idx, pmd_idx, pte_ofs;

  	unsigned long pfn;
  	pgd_t *pgd;
  	pmd_t *pmd;
  	pte_t *pte;

  	unsigned pages_2m, pages_4k;
  	int mapping_iter;

  	start_pfn = start >> PAGE_SHIFT;
  	end_pfn = end >> PAGE_SHIFT;

  	/*
  	 * First iteration will setup identity mapping using large/small pages
  	 * based on use_pse, with other attributes same as set by
  	 * the early code in head_32.S
  	 *
  	 * Second iteration will setup the appropriate attributes (NX, GLOBAL..)
  	 * as desired for the kernel identity mapping.
  	 *
  	 * This two pass mechanism conforms to the TLB app note which says:
  	 *
  	 *     "Software should not write to a paging-structure entry in a way
  	 *      that would change, for any linear address, both the page size
  	 *      and either the page frame or attributes."
  	 */
  	mapping_iter = 1;

  	if (!cpu_has_pse)
  		use_pse = 0;

  repeat:
  	pages_2m = pages_4k = 0;

  	pfn = start_pfn;
  	pgd_idx = pgd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
  	pgd = pgd_base + pgd_idx;

  	for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
  		pmd = one_md_table_init(pgd);

  		if (pfn >= end_pfn)
  			continue;
  #ifdef CONFIG_X86_PAE
  		pmd_idx = pmd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
  		pmd += pmd_idx;
  #else
  		pmd_idx = 0;
  #endif
  		for (; pmd_idx < PTRS_PER_PMD && pfn < end_pfn;

  		     pmd++, pmd_idx++) {

  			unsigned int addr = pfn * PAGE_SIZE + PAGE_OFFSET;

  			/*
  			 * Map with big pages if possible, otherwise
  			 * create normal page tables:
  			 */

  			if (use_pse) {

  				unsigned int addr2;

  				pgprot_t prot = PAGE_KERNEL_LARGE;

  				/*
  				 * first pass will use the same initial
  				 * identity mapping attribute + _PAGE_PSE.
  				 */
  				pgprot_t init_prot =
  					__pgprot(PTE_IDENT_ATTR |
  						 _PAGE_PSE);

  				addr2 = (pfn + PTRS_PER_PTE-1) * PAGE_SIZE +

  					PAGE_OFFSET + PAGE_SIZE-1;

  				if (is_kernel_text(addr) ||
  				    is_kernel_text(addr2))

  					prot = PAGE_KERNEL_LARGE_EXEC;

  				pages_2m++;

  				if (mapping_iter == 1)
  					set_pmd(pmd, pfn_pmd(pfn, init_prot));
  				else
  					set_pmd(pmd, pfn_pmd(pfn, prot));

  				pfn += PTRS_PER_PTE;

  				continue;
  			}
  			pte = one_page_table_init(pmd);

  			pte_ofs = pte_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
  			pte += pte_ofs;
  			for (; pte_ofs < PTRS_PER_PTE && pfn < end_pfn;

  			     pte++, pfn++, pte_ofs++, addr += PAGE_SIZE) {
  				pgprot_t prot = PAGE_KERNEL;

  				/*
  				 * first pass will use the same initial
  				 * identity mapping attribute.
  				 */
  				pgprot_t init_prot = __pgprot(PTE_IDENT_ATTR);

  				if (is_kernel_text(addr))
  					prot = PAGE_KERNEL_EXEC;

  				pages_4k++;

  				if (mapping_iter == 1) {

  					set_pte(pte, pfn_pte(pfn, init_prot));

  					last_map_addr = (pfn << PAGE_SHIFT) + PAGE_SIZE;
  				} else

  					set_pte(pte, pfn_pte(pfn, prot));

  			}
  		}
  	}

  	if (mapping_iter == 1) {
  		/*
  		 * update direct mapping page count only in the first
  		 * iteration.
  		 */
  		update_page_count(PG_LEVEL_2M, pages_2m);
  		update_page_count(PG_LEVEL_4K, pages_4k);
  
  		/*
  		 * local global flush tlb, which will flush the previous
  		 * mappings present in both small and large page TLB's.
  		 */
  		__flush_tlb_all();
  
  		/*
  		 * Second iteration will set the actual desired PTE attributes.
  		 */
  		mapping_iter = 2;
  		goto repeat;
  	}

  	return last_map_addr;

  }

  pte_t *kmap_pte;
  pgprot_t kmap_prot;

  static inline pte_t *kmap_get_fixmap_pte(unsigned long vaddr)
  {
  	return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
  			vaddr), vaddr), vaddr);
  }

  
  static void __init kmap_init(void)
  {
  	unsigned long kmap_vstart;

  	/*
  	 * Cache the first kmap pte:
  	 */

  	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
  	kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
  
  	kmap_prot = PAGE_KERNEL;
  }

  #ifdef CONFIG_HIGHMEM

  static void __init permanent_kmaps_init(pgd_t *pgd_base)
  {

  	unsigned long vaddr;

  	pgd_t *pgd;
  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *pte;

  
  	vaddr = PKMAP_BASE;
  	page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);
  
  	pgd = swapper_pg_dir + pgd_index(vaddr);
  	pud = pud_offset(pgd, vaddr);
  	pmd = pmd_offset(pud, vaddr);
  	pte = pte_offset_kernel(pmd, vaddr);

  	pkmap_page_table = pte;

  }

  static void __init add_one_highpage_init(struct page *page)

  {

  	ClearPageReserved(page);
  	init_page_count(page);
  	__free_page(page);
  	totalhigh_pages++;

  }

  void __init add_highpages_with_active_regions(int nid,
  			 unsigned long start_pfn, unsigned long end_pfn)

  {

  	phys_addr_t start, end;
  	u64 i;
  
  	for_each_free_mem_range(i, nid, &start, &end, NULL) {
  		unsigned long pfn = clamp_t(unsigned long, PFN_UP(start),
  					    start_pfn, end_pfn);
  		unsigned long e_pfn = clamp_t(unsigned long, PFN_DOWN(end),
  					      start_pfn, end_pfn);
  		for ( ; pfn < e_pfn; pfn++)
  			if (pfn_valid(pfn))
  				add_one_highpage_init(pfn_to_page(pfn));

  	}

  }

  #else

  static inline void permanent_kmaps_init(pgd_t *pgd_base)
  {
  }

  #endif /* CONFIG_HIGHMEM */

  void __init native_pagetable_setup_start(pgd_t *base)

  {

  	unsigned long pfn, va;
  	pgd_t *pgd;
  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *pte;

  
  	/*

  	 * Remove any mappings which extend past the end of physical
  	 * memory from the boot time page table:

  	 */

  	for (pfn = max_low_pfn + 1; pfn < 1<<(32-PAGE_SHIFT); pfn++) {
  		va = PAGE_OFFSET + (pfn<<PAGE_SHIFT);
  		pgd = base + pgd_index(va);
  		if (!pgd_present(*pgd))
  			break;
  
  		pud = pud_offset(pgd, va);
  		pmd = pmd_offset(pud, va);
  		if (!pmd_present(*pmd))
  			break;
  
  		pte = pte_offset_kernel(pmd, va);
  		if (!pte_present(*pte))
  			break;
  
  		pte_clear(NULL, va, pte);
  	}

  	paravirt_alloc_pmd(&init_mm, __pa(base) >> PAGE_SHIFT);

  }
  
  void __init native_pagetable_setup_done(pgd_t *base)
  {

  }
  
  /*
   * Build a proper pagetable for the kernel mappings.  Up until this
   * point, we've been running on some set of pagetables constructed by
   * the boot process.
   *
   * If we're booting on native hardware, this will be a pagetable

   * constructed in arch/x86/kernel/head_32.S.  The root of the
   * pagetable will be swapper_pg_dir.

   *
   * If we're booting paravirtualized under a hypervisor, then there are
   * more options: we may already be running PAE, and the pagetable may
   * or may not be based in swapper_pg_dir.  In any case,
   * paravirt_pagetable_setup_start() will set up swapper_pg_dir
   * appropriately for the rest of the initialization to work.
   *
   * In general, pagetable_init() assumes that the pagetable may already
   * be partially populated, and so it avoids stomping on any existing
   * mappings.
   */

  void __init early_ioremap_page_table_range_init(void)

  {

  	pgd_t *pgd_base = swapper_pg_dir;

  	unsigned long vaddr, end;

  	/*
  	 * Fixed mappings, only the page table structure has to be
  	 * created - mappings will be set by set_fixmap():
  	 */
  	vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;

  	end = (FIXADDR_TOP + PMD_SIZE - 1) & PMD_MASK;
  	page_table_range_init(vaddr, end, pgd_base);

  	early_ioremap_reset();

  }
  
  static void __init pagetable_init(void)
  {
  	pgd_t *pgd_base = swapper_pg_dir;

  	permanent_kmaps_init(pgd_base);

  }

  pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL | _PAGE_IOMAP);

  EXPORT_SYMBOL_GPL(__supported_pte_mask);

  /* user-defined highmem size */
  static unsigned int highmem_pages = -1;
  
  /*
   * highmem=size forces highmem to be exactly 'size' bytes.
   * This works even on boxes that have no highmem otherwise.
   * This also works to reduce highmem size on bigger boxes.
   */
  static int __init parse_highmem(char *arg)
  {
  	if (!arg)
  		return -EINVAL;
  
  	highmem_pages = memparse(arg, &arg) >> PAGE_SHIFT;
  	return 0;
  }
  early_param("highmem", parse_highmem);

  #define MSG_HIGHMEM_TOO_BIG \
  	"highmem size (%luMB) is bigger than pages available (%luMB)!
  "
  
  #define MSG_LOWMEM_TOO_SMALL \
  	"highmem size (%luMB) results in <64MB lowmem, ignoring it!
  "

  /*

   * All of RAM fits into lowmem - but if user wants highmem
   * artificially via the highmem=x boot parameter then create
   * it:

   */

  void __init lowmem_pfn_init(void)

  {

  	/* max_low_pfn is 0, we already have early_res support */

  	max_low_pfn = max_pfn;

  	if (highmem_pages == -1)
  		highmem_pages = 0;
  #ifdef CONFIG_HIGHMEM
  	if (highmem_pages >= max_pfn) {
  		printk(KERN_ERR MSG_HIGHMEM_TOO_BIG,
  			pages_to_mb(highmem_pages), pages_to_mb(max_pfn));
  		highmem_pages = 0;
  	}
  	if (highmem_pages) {
  		if (max_low_pfn - highmem_pages < 64*1024*1024/PAGE_SIZE) {
  			printk(KERN_ERR MSG_LOWMEM_TOO_SMALL,

  				pages_to_mb(highmem_pages));
  			highmem_pages = 0;
  		}

  		max_low_pfn -= highmem_pages;
  	}
  #else
  	if (highmem_pages)
  		printk(KERN_ERR "ignoring highmem size on non-highmem kernel!
  ");
  #endif
  }
  
  #define MSG_HIGHMEM_TOO_SMALL \
  	"only %luMB highmem pages available, ignoring highmem size of %luMB!
  "
  
  #define MSG_HIGHMEM_TRIMMED \
  	"Warning: only 4GB will be used. Use a HIGHMEM64G enabled kernel!
  "
  /*
   * We have more RAM than fits into lowmem - we try to put it into
   * highmem, also taking the highmem=x boot parameter into account:
   */
  void __init highmem_pfn_init(void)
  {

  	max_low_pfn = MAXMEM_PFN;

  	if (highmem_pages == -1)
  		highmem_pages = max_pfn - MAXMEM_PFN;
  
  	if (highmem_pages + MAXMEM_PFN < max_pfn)
  		max_pfn = MAXMEM_PFN + highmem_pages;
  
  	if (highmem_pages + MAXMEM_PFN > max_pfn) {
  		printk(KERN_WARNING MSG_HIGHMEM_TOO_SMALL,
  			pages_to_mb(max_pfn - MAXMEM_PFN),
  			pages_to_mb(highmem_pages));
  		highmem_pages = 0;
  	}

  #ifndef CONFIG_HIGHMEM

  	/* Maximum memory usable is what is directly addressable */
  	printk(KERN_WARNING "Warning only %ldMB will be used.
  ", MAXMEM>>20);
  	if (max_pfn > MAX_NONPAE_PFN)
  		printk(KERN_WARNING "Use a HIGHMEM64G enabled kernel.
  ");
  	else
  		printk(KERN_WARNING "Use a HIGHMEM enabled kernel.
  ");
  	max_pfn = MAXMEM_PFN;

  #else /* !CONFIG_HIGHMEM */
  #ifndef CONFIG_HIGHMEM64G

  	if (max_pfn > MAX_NONPAE_PFN) {
  		max_pfn = MAX_NONPAE_PFN;
  		printk(KERN_WARNING MSG_HIGHMEM_TRIMMED);
  	}

  #endif /* !CONFIG_HIGHMEM64G */
  #endif /* !CONFIG_HIGHMEM */

  }
  
  /*
   * Determine low and high memory ranges:
   */
  void __init find_low_pfn_range(void)
  {
  	/* it could update max_pfn */

  	if (max_pfn <= MAXMEM_PFN)

  		lowmem_pfn_init();

  	else
  		highmem_pfn_init();

  }

  #ifndef CONFIG_NEED_MULTIPLE_NODES

  void __init initmem_init(void)

  {

  #ifdef CONFIG_HIGHMEM
  	highstart_pfn = highend_pfn = max_pfn;
  	if (max_pfn > max_low_pfn)
  		highstart_pfn = max_low_pfn;

  	printk(KERN_NOTICE "%ldMB HIGHMEM available.
  ",
  		pages_to_mb(highend_pfn - highstart_pfn));
  	num_physpages = highend_pfn;
  	high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
  #else

  	num_physpages = max_low_pfn;
  	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
  #endif

  
  	memblock_set_node(0, (phys_addr_t)ULLONG_MAX, 0);
  	sparse_memory_present_with_active_regions(0);

  #ifdef CONFIG_FLATMEM
  	max_mapnr = num_physpages;
  #endif

  	__vmalloc_start_set = true;

  	printk(KERN_NOTICE "%ldMB LOWMEM available.
  ",
  			pages_to_mb(max_low_pfn));
  
  	setup_bootmem_allocator();

  }

  #endif /* !CONFIG_NEED_MULTIPLE_NODES */

  void __init setup_bootmem_allocator(void)
  {

  	printk(KERN_INFO "  mapped low ram: 0 - %08lx
  ",
  		 max_pfn_mapped<<PAGE_SHIFT);

  	printk(KERN_INFO "  low ram: 0 - %08lx
  ", max_low_pfn<<PAGE_SHIFT);

  	after_bootmem = 1;

  }

  /*
   * paging_init() sets up the page tables - note that the first 8MB are
   * already mapped by head.S.
   *
   * This routines also unmaps the page at virtual kernel address 0, so
   * that we can trap those pesky NULL-reference errors in the kernel.
   */
  void __init paging_init(void)
  {

  	pagetable_init();

  	__flush_tlb_all();
  
  	kmap_init();

  
  	/*
  	 * NOTE: at this point the bootmem allocator is fully available.
  	 */

  	olpc_dt_build_devicetree();

  	sparse_memory_present_with_active_regions(MAX_NUMNODES);

  	sparse_init();
  	zone_sizes_init();

  }
  
  /*
   * Test if the WP bit works in supervisor mode. It isn't supported on 386's

   * and also on some strange 486's. All 586+'s are OK. This used to involve
   * black magic jumps to work around some nasty CPU bugs, but fortunately the
   * switch to using exceptions got rid of all that.

   */

  static void __init test_wp_bit(void)
  {

  	printk(KERN_INFO
    "Checking if this processor honours the WP bit even in supervisor mode...");

  
  	/* Any page-aligned address will do, the test is non-destructive */
  	__set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_READONLY);
  	boot_cpu_data.wp_works_ok = do_test_wp_bit();
  	clear_fixmap(FIX_WP_TEST);
  
  	if (!boot_cpu_data.wp_works_ok) {

  		printk(KERN_CONT "No.
  ");

  #ifdef CONFIG_X86_WP_WORKS_OK

  		panic(
    "This kernel doesn't support CPU's with broken WP. Recompile it for a 386!");

  #endif
  	} else {

  		printk(KERN_CONT "Ok.
  ");

  	}
  }

  void __init mem_init(void)
  {

  	int codesize, reservedpages, datasize, initsize;

  	int tmp;

  	pci_iommu_alloc();

  #ifdef CONFIG_FLATMEM

  	BUG_ON(!mem_map);

  #endif

  	/*
  	 * With CONFIG_DEBUG_PAGEALLOC initialization of highmem pages has to
  	 * be done before free_all_bootmem(). Memblock use free low memory for
  	 * temporary data (see find_range_array()) and for this purpose can use
  	 * pages that was already passed to the buddy allocator, hence marked as
  	 * not accessible in the page tables when compiled with
  	 * CONFIG_DEBUG_PAGEALLOC. Otherwise order of initialization is not
  	 * important here.
  	 */
  	set_highmem_pages_init();

  	/* this will put all low memory onto the freelists */
  	totalram_pages += free_all_bootmem();
  
  	reservedpages = 0;
  	for (tmp = 0; tmp < max_low_pfn; tmp++)
  		/*

  		 * Only count reserved RAM pages:

  		 */
  		if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
  			reservedpages++;

  	codesize =  (unsigned long) &_etext - (unsigned long) &_text;
  	datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
  	initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;

  	printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, "
  			"%dk reserved, %dk data, %dk init, %ldk highmem)
  ",

  		nr_free_pages() << (PAGE_SHIFT-10),

  		num_physpages << (PAGE_SHIFT-10),
  		codesize >> 10,
  		reservedpages << (PAGE_SHIFT-10),
  		datasize >> 10,
  		initsize >> 10,

  		totalhigh_pages << (PAGE_SHIFT-10));

  	printk(KERN_INFO "virtual kernel memory layout:
  "

  		"    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)
  "

  #ifdef CONFIG_HIGHMEM

  		"    pkmap   : 0x%08lx - 0x%08lx   (%4ld kB)
  "

  #endif

  		"    vmalloc : 0x%08lx - 0x%08lx   (%4ld MB)
  "
  		"    lowmem  : 0x%08lx - 0x%08lx   (%4ld MB)
  "
  		"      .init : 0x%08lx - 0x%08lx   (%4ld kB)
  "
  		"      .data : 0x%08lx - 0x%08lx   (%4ld kB)
  "
  		"      .text : 0x%08lx - 0x%08lx   (%4ld kB)
  ",
  		FIXADDR_START, FIXADDR_TOP,
  		(FIXADDR_TOP - FIXADDR_START) >> 10,

  
  #ifdef CONFIG_HIGHMEM

  		PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE,
  		(LAST_PKMAP*PAGE_SIZE) >> 10,

  #endif

  		VMALLOC_START, VMALLOC_END,
  		(VMALLOC_END - VMALLOC_START) >> 20,

  		(unsigned long)__va(0), (unsigned long)high_memory,
  		((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,

  		(unsigned long)&__init_begin, (unsigned long)&__init_end,
  		((unsigned long)&__init_end -
  		 (unsigned long)&__init_begin) >> 10,

  		(unsigned long)&_etext, (unsigned long)&_edata,
  		((unsigned long)&_edata - (unsigned long)&_etext) >> 10,

  		(unsigned long)&_text, (unsigned long)&_etext,
  		((unsigned long)&_etext - (unsigned long)&_text) >> 10);

  	/*
  	 * Check boundaries twice: Some fundamental inconsistencies can
  	 * be detected at build time already.
  	 */
  #define __FIXADDR_TOP (-PAGE_SIZE)
  #ifdef CONFIG_HIGHMEM
  	BUILD_BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE	> FIXADDR_START);
  	BUILD_BUG_ON(VMALLOC_END			> PKMAP_BASE);
  #endif
  #define high_memory (-128UL << 20)
  	BUILD_BUG_ON(VMALLOC_START			>= VMALLOC_END);
  #undef high_memory
  #undef __FIXADDR_TOP

  #ifdef CONFIG_HIGHMEM

  	BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE	> FIXADDR_START);
  	BUG_ON(VMALLOC_END				> PKMAP_BASE);

  #endif

  	BUG_ON(VMALLOC_START				>= VMALLOC_END);

  	BUG_ON((unsigned long)high_memory		> VMALLOC_START);

  	if (boot_cpu_data.wp_works_ok < 0)
  		test_wp_bit();

  }

  #ifdef CONFIG_MEMORY_HOTPLUG

  int arch_add_memory(int nid, u64 start, u64 size)

  {

  	struct pglist_data *pgdata = NODE_DATA(nid);

  	struct zone *zone = pgdata->node_zones + ZONE_HIGHMEM;

  	unsigned long start_pfn = start >> PAGE_SHIFT;
  	unsigned long nr_pages = size >> PAGE_SHIFT;

  	return __add_pages(nid, zone, start_pfn, nr_pages);

  }

  #endif

  /*
   * This function cannot be __init, since exceptions don't work in that
   * section.  Put this after the callers, so that it cannot be inlined.
   */

  static noinline int do_test_wp_bit(void)

  {
  	char tmp_reg;
  	int flag;
  
  	__asm__ __volatile__(

  		"	movb %0, %1	
  "
  		"1:	movb %1, %0	
  "
  		"	xorl %2, %2	
  "

  		"2:			
  "

  		_ASM_EXTABLE(1b,2b)

  		:"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
  		 "=q" (tmp_reg),
  		 "=r" (flag)
  		:"2" (1)
  		:"memory");

  	return flag;
  }

  #ifdef CONFIG_DEBUG_RODATA

  const int rodata_test_data = 0xC3;
  EXPORT_SYMBOL_GPL(rodata_test_data);

  int kernel_set_to_readonly __read_mostly;

  
  void set_kernel_text_rw(void)
  {
  	unsigned long start = PFN_ALIGN(_text);
  	unsigned long size = PFN_ALIGN(_etext) - start;
  
  	if (!kernel_set_to_readonly)
  		return;
  
  	pr_debug("Set kernel text: %lx - %lx for read write
  ",
  		 start, start+size);
  
  	set_pages_rw(virt_to_page(start), size >> PAGE_SHIFT);
  }
  
  void set_kernel_text_ro(void)
  {
  	unsigned long start = PFN_ALIGN(_text);
  	unsigned long size = PFN_ALIGN(_etext) - start;
  
  	if (!kernel_set_to_readonly)
  		return;
  
  	pr_debug("Set kernel text: %lx - %lx for read only
  ",
  		 start, start+size);
  
  	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
  }

  static void mark_nxdata_nx(void)
  {
  	/*
  	 * When this called, init has already been executed and released,

  	 * so everything past _etext should be NX.

  	 */
  	unsigned long start = PFN_ALIGN(_etext);
  	/*
  	 * This comes from is_kernel_text upper limit. Also HPAGE where used:
  	 */
  	unsigned long size = (((unsigned long)__init_end + HPAGE_SIZE) & HPAGE_MASK) - start;
  
  	if (__supported_pte_mask & _PAGE_NX)
  		printk(KERN_INFO "NX-protecting the kernel data: %luk
  ", size >> 10);
  	set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
  }

  void mark_rodata_ro(void)
  {

  	unsigned long start = PFN_ALIGN(_text);
  	unsigned long size = PFN_ALIGN(_etext) - start;

  	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
  	printk(KERN_INFO "Write protecting the kernel text: %luk
  ",
  		size >> 10);

  	kernel_set_to_readonly = 1;

  #ifdef CONFIG_CPA_DEBUG

  	printk(KERN_INFO "Testing CPA: Reverting %lx-%lx
  ",
  		start, start+size);
  	set_pages_rw(virt_to_page(start), size>>PAGE_SHIFT);

  	printk(KERN_INFO "Testing CPA: write protecting again
  ");
  	set_pages_ro(virt_to_page(start), size>>PAGE_SHIFT);

  #endif

  	start += size;
  	size = (unsigned long)__end_rodata - start;

  	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

  	printk(KERN_INFO "Write protecting the kernel read-only data: %luk
  ",
  		size >> 10);

  	rodata_test();

  #ifdef CONFIG_CPA_DEBUG

  	printk(KERN_INFO "Testing CPA: undo %lx-%lx
  ", start, start + size);

  	set_pages_rw(virt_to_page(start), size >> PAGE_SHIFT);

  	printk(KERN_INFO "Testing CPA: write protecting again
  ");

  	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

  #endif

  	mark_nxdata_nx();

  }
  #endif