arch/powerpc/mm/pgtable_32.c - linux - Git at Google

 /*
  * This file contains the routines setting up the linux page tables.
  *  -- paulus
  *
  *  Derived from arch/ppc/mm/init.c:
  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
  *
  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
  *    Copyright (C) 1996 Paul Mackerras
  *
  *  Derived from "arch/i386/mm/init.c"
  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  as published by the Free Software Foundation; either version
  *  2 of the License, or (at your option) any later version.
  *
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
 #include <linux/memblock.h>
 #include <linux/slab.h>

 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
 #include <asm/fixmap.h>
 #include <asm/io.h>
 #include <asm/setup.h>
 #include <asm/sections.h>

 #include "mmu_decl.h"

 unsigned long ioremap_bot;
 EXPORT_SYMBOL(ioremap_bot);	/* aka VMALLOC_END */

 extern char etext[], _stext[], _sinittext[], _einittext[];

 __ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
 {
 	if (!slab_is_available())
 		return memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);

 	return (pte_t *)pte_fragment_alloc(mm, 1);
 }

 pgtable_t pte_alloc_one(struct mm_struct *mm)
 {
 	return (pgtable_t)pte_fragment_alloc(mm, 0);
 }

 void __iomem *
 ioremap(phys_addr_t addr, unsigned long size)
 {
 	pgprot_t prot = pgprot_noncached(PAGE_KERNEL);

 	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(ioremap);

 void __iomem *
 ioremap_wc(phys_addr_t addr, unsigned long size)
 {
 	pgprot_t prot = pgprot_noncached_wc(PAGE_KERNEL);

 	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(ioremap_wc);

 void __iomem *
 ioremap_wt(phys_addr_t addr, unsigned long size)
 {
 	pgprot_t prot = pgprot_cached_wthru(PAGE_KERNEL);

 	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(ioremap_wt);

 void __iomem *
 ioremap_coherent(phys_addr_t addr, unsigned long size)
 {
 	pgprot_t prot = pgprot_cached(PAGE_KERNEL);

 	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(ioremap_coherent);

 void __iomem *
 ioremap_prot(phys_addr_t addr, unsigned long size, unsigned long flags)
 {
 	pte_t pte = __pte(flags);

 	/* writeable implies dirty for kernel addresses */
 	if (pte_write(pte))
 		pte = pte_mkdirty(pte);

 	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
 	pte = pte_exprotect(pte);
 	pte = pte_mkprivileged(pte);

 	return __ioremap_caller(addr, size, pte_pgprot(pte), __builtin_return_address(0));
 }
 EXPORT_SYMBOL(ioremap_prot);

 void __iomem *
 __ioremap(phys_addr_t addr, unsigned long size, unsigned long flags)
 {
 	return __ioremap_caller(addr, size, __pgprot(flags), __builtin_return_address(0));
 }

 void __iomem *
 __ioremap_caller(phys_addr_t addr, unsigned long size, pgprot_t prot, void *caller)
 {
 	unsigned long v, i;
 	phys_addr_t p;
 	int err;

 	/*
 	 * Choose an address to map it to.
 	 * Once the vmalloc system is running, we use it.
 	 * Before then, we use space going down from IOREMAP_TOP
 	 * (ioremap_bot records where we're up to).
 	 */
 	p = addr & PAGE_MASK;
 	size = PAGE_ALIGN(addr + size) - p;

 	/*
 	 * If the address lies within the first 16 MB, assume it's in ISA
 	 * memory space
 	 */
 	if (p < 16*1024*1024)
 		p += _ISA_MEM_BASE;

 #ifndef CONFIG_CRASH_DUMP
 	/*
 	 * Don't allow anybody to remap normal RAM that we're using.
 	 * mem_init() sets high_memory so only do the check after that.
 	 */
 	if (slab_is_available() && p <= virt_to_phys(high_memory - 1) &&
 	    page_is_ram(__phys_to_pfn(p))) {
 		printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
 		       (unsigned long long)p, __builtin_return_address(0));
 		return NULL;
 	}
 #endif

 	if (size == 0)
 		return NULL;

 	/*
 	 * Is it already mapped?  Perhaps overlapped by a previous
 	 * mapping.
 	 */
 	v = p_block_mapped(p);
 	if (v)
 		goto out;

 	if (slab_is_available()) {
 		struct vm_struct *area;
 		area = get_vm_area_caller(size, VM_IOREMAP, caller);
 		if (area == 0)
 			return NULL;
 		area->phys_addr = p;
 		v = (unsigned long) area->addr;
 	} else {
 		v = (ioremap_bot -= size);
 	}

 	/*
 	 * Should check if it is a candidate for a BAT mapping
 	 */

 	err = 0;
 	for (i = 0; i < size && err == 0; i += PAGE_SIZE)
 		err = map_kernel_page(v + i, p + i, prot);
 	if (err) {
 		if (slab_is_available())
 			vunmap((void *)v);
 		return NULL;
 	}

 out:
 	return (void __iomem *) (v + ((unsigned long)addr & ~PAGE_MASK));
 }
 EXPORT_SYMBOL(__ioremap);

 void iounmap(volatile void __iomem *addr)
 {
 	/*
 	 * If mapped by BATs then there is nothing to do.
 	 * Calling vfree() generates a benign warning.
 	 */
 	if (v_block_mapped((unsigned long)addr))
 		return;

 	if (addr > high_memory && (unsigned long) addr < ioremap_bot)
 		vunmap((void *) (PAGE_MASK & (unsigned long)addr));
 }
 EXPORT_SYMBOL(iounmap);

 int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
 {
 	pmd_t *pd;
 	pte_t *pg;
 	int err = -ENOMEM;

 	/* Use upper 10 bits of VA to index the first level map */
 	pd = pmd_offset(pud_offset(pgd_offset_k(va), va), va);
 	/* Use middle 10 bits of VA to index the second-level map */
 	pg = pte_alloc_kernel(pd, va);
 	if (pg != 0) {
 		err = 0;
 		/* The PTE should never be already set nor present in the
 		 * hash table
 		 */
 		BUG_ON((pte_present(*pg) | pte_hashpte(*pg)) && pgprot_val(prot));
 		set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT, prot));
 	}
 	smp_wmb();
 	return err;
 }

 /*
  * Map in a chunk of physical memory starting at start.
  */
 static void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
 {
 	unsigned long v, s;
 	phys_addr_t p;
 	int ktext;

 	s = offset;
 	v = PAGE_OFFSET + s;
 	p = memstart_addr + s;
 	for (; s < top; s += PAGE_SIZE) {
 		ktext = ((char *)v >= _stext && (char *)v < etext) ||
 			((char *)v >= _sinittext && (char *)v < _einittext);
 		map_kernel_page(v, p, ktext ? PAGE_KERNEL_TEXT : PAGE_KERNEL);
 #ifdef CONFIG_PPC_BOOK3S_32
 		if (ktext)
 			hash_preload(&init_mm, v, false, 0x300);
 #endif
 		v += PAGE_SIZE;
 		p += PAGE_SIZE;
 	}
 }

 void __init mapin_ram(void)
 {
 	unsigned long s, top;

 #ifndef CONFIG_WII
 	top = total_lowmem;
 	s = mmu_mapin_ram(top);
 	__mapin_ram_chunk(s, top);
 #else
 	if (!wii_hole_size) {
 		s = mmu_mapin_ram(total_lowmem);
 		__mapin_ram_chunk(s, total_lowmem);
 	} else {
 		top = wii_hole_start;
 		s = mmu_mapin_ram(top);
 		__mapin_ram_chunk(s, top);

 		top = memblock_end_of_DRAM();
 		s = wii_mmu_mapin_mem2(top);
 		__mapin_ram_chunk(s, top);
 	}
 #endif
 }

 /* Scan the real Linux page tables and return a PTE pointer for
  * a virtual address in a context.
  * Returns true (1) if PTE was found, zero otherwise.  The pointer to
  * the PTE pointer is unmodified if PTE is not found.
  */
 static int
 get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
 {
         pgd_t	*pgd;
 	pud_t	*pud;
         pmd_t	*pmd;
         pte_t	*pte;
         int     retval = 0;

         pgd = pgd_offset(mm, addr & PAGE_MASK);
         if (pgd) {
 		pud = pud_offset(pgd, addr & PAGE_MASK);
 		if (pud && pud_present(*pud)) {
 			pmd = pmd_offset(pud, addr & PAGE_MASK);
 			if (pmd_present(*pmd)) {
 				pte = pte_offset_map(pmd, addr & PAGE_MASK);
 				if (pte) {
 					retval = 1;
 					*ptep = pte;
 					if (pmdp)
 						*pmdp = pmd;
 					/* XXX caller needs to do pte_unmap, yuck */
 				}
 			}
 		}
         }
         return(retval);
 }

 static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
 {
 	pte_t *kpte;
 	pmd_t *kpmd;
 	unsigned long address;

 	BUG_ON(PageHighMem(page));
 	address = (unsigned long)page_address(page);

 	if (v_block_mapped(address))
 		return 0;
 	if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
 		return -EINVAL;
 	__set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
 	pte_unmap(kpte);

 	return 0;
 }

 /*
  * Change the page attributes of an page in the linear mapping.
  *
  * THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
  */
 static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 {
 	int i, err = 0;
 	unsigned long flags;
 	struct page *start = page;

 	local_irq_save(flags);
 	for (i = 0; i < numpages; i++, page++) {
 		err = __change_page_attr_noflush(page, prot);
 		if (err)
 			break;
 	}
 	wmb();
 	local_irq_restore(flags);
 	flush_tlb_kernel_range((unsigned long)page_address(start),
 			       (unsigned long)page_address(page));
 	return err;
 }

 void mark_initmem_nx(void)
 {
 	struct page *page = virt_to_page(_sinittext);
 	unsigned long numpages = PFN_UP((unsigned long)_einittext) -
 				 PFN_DOWN((unsigned long)_sinittext);

 	change_page_attr(page, numpages, PAGE_KERNEL);
 }

 #ifdef CONFIG_STRICT_KERNEL_RWX
 void mark_rodata_ro(void)
 {
 	struct page *page;
 	unsigned long numpages;

 	page = virt_to_page(_stext);
 	numpages = PFN_UP((unsigned long)_etext) -
 		   PFN_DOWN((unsigned long)_stext);

 	change_page_attr(page, numpages, PAGE_KERNEL_ROX);
 	/*
 	 * mark .rodata as read only. Use __init_begin rather than __end_rodata
 	 * to cover NOTES and EXCEPTION_TABLE.
 	 */
 	page = virt_to_page(__start_rodata);
 	numpages = PFN_UP((unsigned long)__init_begin) -
 		   PFN_DOWN((unsigned long)__start_rodata);

 	change_page_attr(page, numpages, PAGE_KERNEL_RO);
 }
 #endif

 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	if (PageHighMem(page))
 		return;

 	change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 }
 #endif /* CONFIG_DEBUG_PAGEALLOC */
	/*
	* This file contains the routines setting up the linux page tables.
	* -- paulus
	*
	* Derived from arch/ppc/mm/init.c:
	* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
	*
	* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
	* and Cort Dougan (PReP) (cort@cs.nmt.edu)
	* Copyright (C) 1996 Paul Mackerras
	*
	* Derived from "arch/i386/mm/init.c"
	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/mm.h>
	#include <linux/vmalloc.h>
	#include <linux/init.h>
	#include <linux/highmem.h>
	#include <linux/memblock.h>
	#include <linux/slab.h>

	#include <asm/pgtable.h>
	#include <asm/pgalloc.h>
	#include <asm/fixmap.h>
	#include <asm/io.h>
	#include <asm/setup.h>
	#include <asm/sections.h>

	#include "mmu_decl.h"

	unsigned long ioremap_bot;
	EXPORT_SYMBOL(ioremap_bot); /* aka VMALLOC_END */

	extern char etext[], _stext[], _sinittext[], _einittext[];

	__ref pte_t pte_alloc_one_kernel(struct mm_struct mm)
	{
	if (!slab_is_available())
	return memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);

	return (pte_t *)pte_fragment_alloc(mm, 1);
	}

	pgtable_t pte_alloc_one(struct mm_struct *mm)
	{
	return (pgtable_t)pte_fragment_alloc(mm, 0);
	}

	void __iomem *
	ioremap(phys_addr_t addr, unsigned long size)
	{
	pgprot_t prot = pgprot_noncached(PAGE_KERNEL);

	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
	}
	EXPORT_SYMBOL(ioremap);

	void __iomem *
	ioremap_wc(phys_addr_t addr, unsigned long size)
	{
	pgprot_t prot = pgprot_noncached_wc(PAGE_KERNEL);

	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
	}
	EXPORT_SYMBOL(ioremap_wc);

	void __iomem *
	ioremap_wt(phys_addr_t addr, unsigned long size)
	{
	pgprot_t prot = pgprot_cached_wthru(PAGE_KERNEL);

	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
	}
	EXPORT_SYMBOL(ioremap_wt);

	void __iomem *
	ioremap_coherent(phys_addr_t addr, unsigned long size)
	{
	pgprot_t prot = pgprot_cached(PAGE_KERNEL);

	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
	}
	EXPORT_SYMBOL(ioremap_coherent);

	void __iomem *
	ioremap_prot(phys_addr_t addr, unsigned long size, unsigned long flags)
	{
	pte_t pte = __pte(flags);

	/* writeable implies dirty for kernel addresses */
	if (pte_write(pte))
	pte = pte_mkdirty(pte);

	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
	pte = pte_exprotect(pte);
	pte = pte_mkprivileged(pte);

	return __ioremap_caller(addr, size, pte_pgprot(pte), __builtin_return_address(0));
	}
	EXPORT_SYMBOL(ioremap_prot);

	void __iomem *
	__ioremap(phys_addr_t addr, unsigned long size, unsigned long flags)
	{
	return __ioremap_caller(addr, size, __pgprot(flags), __builtin_return_address(0));
	}

	void __iomem *
	__ioremap_caller(phys_addr_t addr, unsigned long size, pgprot_t prot, void *caller)
	{
	unsigned long v, i;
	phys_addr_t p;
	int err;

	/*
	* Choose an address to map it to.
	* Once the vmalloc system is running, we use it.
	* Before then, we use space going down from IOREMAP_TOP
	* (ioremap_bot records where we're up to).
	*/
	p = addr & PAGE_MASK;
	size = PAGE_ALIGN(addr + size) - p;

	/*
	* If the address lies within the first 16 MB, assume it's in ISA
	* memory space
	*/
	if (p < 1610241024)
	p += _ISA_MEM_BASE;

	#ifndef CONFIG_CRASH_DUMP
	/*
	* Don't allow anybody to remap normal RAM that we're using.
	* mem_init() sets high_memory so only do the check after that.
	*/
	if (slab_is_available() && p <= virt_to_phys(high_memory - 1) &&
	page_is_ram(__phys_to_pfn(p))) {
	printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
	(unsigned long long)p, __builtin_return_address(0));
	return NULL;
	}
	#endif

	if (size == 0)
	return NULL;

	/*
	* Is it already mapped? Perhaps overlapped by a previous
	* mapping.
	*/
	v = p_block_mapped(p);
	if (v)
	goto out;

	if (slab_is_available()) {
	struct vm_struct *area;
	area = get_vm_area_caller(size, VM_IOREMAP, caller);
	if (area == 0)
	return NULL;
	area->phys_addr = p;
	v = (unsigned long) area->addr;
	} else {
	v = (ioremap_bot -= size);
	}

	/*
	* Should check if it is a candidate for a BAT mapping
	*/

	err = 0;
	for (i = 0; i < size && err == 0; i += PAGE_SIZE)
	err = map_kernel_page(v + i, p + i, prot);
	if (err) {
	if (slab_is_available())
	vunmap((void *)v);
	return NULL;
	}

	out:
	return (void __iomem *) (v + ((unsigned long)addr & ~PAGE_MASK));
	}
	EXPORT_SYMBOL(__ioremap);

	void iounmap(volatile void __iomem *addr)
	{
	/*
	* If mapped by BATs then there is nothing to do.
	* Calling vfree() generates a benign warning.
	*/
	if (v_block_mapped((unsigned long)addr))
	return;

	if (addr > high_memory && (unsigned long) addr < ioremap_bot)
	vunmap((void *) (PAGE_MASK & (unsigned long)addr));
	}
	EXPORT_SYMBOL(iounmap);

	int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
	{
	pmd_t *pd;
	pte_t *pg;
	int err = -ENOMEM;

	/* Use upper 10 bits of VA to index the first level map */
	pd = pmd_offset(pud_offset(pgd_offset_k(va), va), va);
	/* Use middle 10 bits of VA to index the second-level map */
	pg = pte_alloc_kernel(pd, va);
	if (pg != 0) {
	err = 0;
	/* The PTE should never be already set nor present in the
	* hash table
	*/
	BUG_ON((pte_present(pg) \| pte_hashpte(pg)) && pgprot_val(prot));
	set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT, prot));
	}
	smp_wmb();
	return err;
	}

	/*
	* Map in a chunk of physical memory starting at start.
	*/
	static void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
	{
	unsigned long v, s;
	phys_addr_t p;
	int ktext;

	s = offset;
	v = PAGE_OFFSET + s;
	p = memstart_addr + s;
	for (; s < top; s += PAGE_SIZE) {
	ktext = ((char )v >= _stext && (char )v < etext) \|\|
	((char )v >= _sinittext && (char )v < _einittext);
	map_kernel_page(v, p, ktext ? PAGE_KERNEL_TEXT : PAGE_KERNEL);
	#ifdef CONFIG_PPC_BOOK3S_32
	if (ktext)
	hash_preload(&init_mm, v, false, 0x300);
	#endif
	v += PAGE_SIZE;
	p += PAGE_SIZE;
	}
	}

	void __init mapin_ram(void)
	{
	unsigned long s, top;

	#ifndef CONFIG_WII
	top = total_lowmem;
	s = mmu_mapin_ram(top);
	__mapin_ram_chunk(s, top);
	#else
	if (!wii_hole_size) {
	s = mmu_mapin_ram(total_lowmem);
	__mapin_ram_chunk(s, total_lowmem);
	} else {
	top = wii_hole_start;
	s = mmu_mapin_ram(top);
	__mapin_ram_chunk(s, top);

	top = memblock_end_of_DRAM();
	s = wii_mmu_mapin_mem2(top);
	__mapin_ram_chunk(s, top);
	}
	#endif
	}

	/* Scan the real Linux page tables and return a PTE pointer for
	* a virtual address in a context.
	* Returns true (1) if PTE was found, zero otherwise. The pointer to
	* the PTE pointer is unmodified if PTE is not found.
	*/
	static int
	get_pteptr(struct mm_struct mm, unsigned long addr, pte_t ptep, pmd_t *pmdp)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int retval = 0;

	pgd = pgd_offset(mm, addr & PAGE_MASK);
	if (pgd) {
	pud = pud_offset(pgd, addr & PAGE_MASK);
	if (pud && pud_present(*pud)) {
	pmd = pmd_offset(pud, addr & PAGE_MASK);
	if (pmd_present(*pmd)) {
	pte = pte_offset_map(pmd, addr & PAGE_MASK);
	if (pte) {
	retval = 1;
	*ptep = pte;
	if (pmdp)
	*pmdp = pmd;
	/* XXX caller needs to do pte_unmap, yuck */
	}
	}
	}
	}
	return(retval);
	}

	static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
	{
	pte_t *kpte;
	pmd_t *kpmd;
	unsigned long address;

	BUG_ON(PageHighMem(page));
	address = (unsigned long)page_address(page);

	if (v_block_mapped(address))
	return 0;
	if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
	return -EINVAL;
	__set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
	pte_unmap(kpte);

	return 0;
	}

	/*
	* Change the page attributes of an page in the linear mapping.
	*
	* THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
	*/
	static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
	{
	int i, err = 0;
	unsigned long flags;
	struct page *start = page;

	local_irq_save(flags);
	for (i = 0; i < numpages; i++, page++) {
	err = __change_page_attr_noflush(page, prot);
	if (err)
	break;
	}
	wmb();
	local_irq_restore(flags);
	flush_tlb_kernel_range((unsigned long)page_address(start),
	(unsigned long)page_address(page));
	return err;
	}

	void mark_initmem_nx(void)
	{
	struct page *page = virt_to_page(_sinittext);
	unsigned long numpages = PFN_UP((unsigned long)_einittext) -
	PFN_DOWN((unsigned long)_sinittext);

	change_page_attr(page, numpages, PAGE_KERNEL);
	}

	#ifdef CONFIG_STRICT_KERNEL_RWX
	void mark_rodata_ro(void)
	{
	struct page *page;
	unsigned long numpages;

	page = virt_to_page(_stext);
	numpages = PFN_UP((unsigned long)_etext) -
	PFN_DOWN((unsigned long)_stext);

	change_page_attr(page, numpages, PAGE_KERNEL_ROX);
	/*
	* mark .rodata as read only. Use __init_begin rather than __end_rodata
	* to cover NOTES and EXCEPTION_TABLE.
	*/
	page = virt_to_page(__start_rodata);
	numpages = PFN_UP((unsigned long)__init_begin) -
	PFN_DOWN((unsigned long)__start_rodata);

	change_page_attr(page, numpages, PAGE_KERNEL_RO);
	}
	#endif

	#ifdef CONFIG_DEBUG_PAGEALLOC
	void __kernel_map_pages(struct page *page, int numpages, int enable)
	{
	if (PageHighMem(page))
	return;

	change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
	}
	#endif /* CONFIG_DEBUG_PAGEALLOC */