arch/i386/mm/init.c - kernel/msm-4.19 - Gitiles

 /*
  *  linux/arch/i386/mm/init.c
  *
  *  Copyright (C) 1995  Linus Torvalds
  *
  *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
  */

 #include <linux/config.h>
 #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/bootmem.h>
 #include <linux/slab.h>
 #include <linux/proc_fs.h>
 #include <linux/efi.h>
 #include <linux/memory_hotplug.h>
 #include <linux/initrd.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/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/sections.h>

 unsigned int __VMALLOC_RESERVE = 128 << 20;

 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 unsigned long highstart_pfn, highend_pfn;

 static int noinline do_test_wp_bit(void);

 /*
  * 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
 	pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
 	set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
 	pud = pud_offset(pgd, 0);
 	if (pmd_table != pmd_offset(pud, 0))
 		BUG();
 #else
 	pud = pud_offset(pgd, 0);
 	pmd_table = pmd_offset(pud, 0);
 #endif

 	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_none(*pmd)) {
 		pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
 		set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
 		if (page_table != pte_offset_kernel(pmd, 0))
 			BUG();

 		return page_table;
 	}

 	return pte_offset_kernel(pmd, 0);
 }

 /*
  * 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)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	int pgd_idx, pmd_idx;
 	unsigned long vaddr;

 	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++) {
 		if (pgd_none(*pgd))
 			one_md_table_init(pgd);
 		pud = pud_offset(pgd, vaddr);
 		pmd = pmd_offset(pud, vaddr);
 		for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) {
 			if (pmd_none(*pmd))
 				one_page_table_init(pmd);

 			vaddr += PMD_SIZE;
 		}
 		pmd_idx = 0;
 	}
 }

 static inline int is_kernel_text(unsigned long addr)
 {
 	if (addr >= PAGE_OFFSET && 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.
  */
 static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
 {
 	unsigned long pfn;
 	pgd_t *pgd;
 	pmd_t *pmd;
 	pte_t *pte;
 	int pgd_idx, pmd_idx, pte_ofs;

 	pgd_idx = pgd_index(PAGE_OFFSET);
 	pgd = pgd_base + pgd_idx;
 	pfn = 0;

 	for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
 		pmd = one_md_table_init(pgd);
 		if (pfn >= max_low_pfn)
 			continue;
 		for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
 			unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;

 			/* Map with big pages if possible, otherwise create normal page tables. */
 			if (cpu_has_pse) {
 				unsigned int address2 = (pfn + PTRS_PER_PTE - 1) * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;

 				if (is_kernel_text(address) || is_kernel_text(address2))
 					set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
 				else
 					set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));
 				pfn += PTRS_PER_PTE;
 			} else {
 				pte = one_page_table_init(pmd);

 				for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn; pte++, pfn++, pte_ofs++) {
 						if (is_kernel_text(address))
 							set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 						else
 							set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));
 				}
 			}
 		}
 	}
 }

 static inline int page_kills_ppro(unsigned long pagenr)
 {
 	if (pagenr >= 0x70000 && pagenr <= 0x7003F)
 		return 1;
 	return 0;
 }

 extern int is_available_memory(efi_memory_desc_t *);

 int page_is_ram(unsigned long pagenr)
 {
 	int i;
 	unsigned long addr, end;

 	if (efi_enabled) {
 		efi_memory_desc_t *md;
 		void *p;

 		for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 			md = p;
 			if (!is_available_memory(md))
 				continue;
 			addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 			end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;

 			if ((pagenr >= addr) && (pagenr < end))
 				return 1;
 		}
 		return 0;
 	}

 	for (i = 0; i < e820.nr_map; i++) {

 		if (e820.map[i].type != E820_RAM)	/* not usable memory */
 			continue;
 		/*
 		 *	!!!FIXME!!! Some BIOSen report areas as RAM that
 		 *	are not. Notably the 640->1Mb area. We need a sanity
 		 *	check here.
 		 */
 		addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 		end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
 		if  ((pagenr >= addr) && (pagenr < end))
 			return 1;
 	}
 	return 0;
 }

 #ifdef CONFIG_HIGHMEM
 pte_t *kmap_pte;
 pgprot_t kmap_prot;

 #define kmap_get_fixmap_pte(vaddr)					\
 	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;
 }

 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	unsigned long vaddr;

 	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 __meminit free_new_highpage(struct page *page)
 {
 	init_page_count(page);
 	__free_page(page);
 	totalhigh_pages++;
 }

 void __init add_one_highpage_init(struct page *page, int pfn, int bad_ppro)
 {
 	if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
 		ClearPageReserved(page);
 		free_new_highpage(page);
 	} else
 		SetPageReserved(page);
 }

 static int add_one_highpage_hotplug(struct page *page, unsigned long pfn)
 {
 	free_new_highpage(page);
 	totalram_pages++;
 #ifdef CONFIG_FLATMEM
 	max_mapnr = max(pfn, max_mapnr);
 #endif
 	num_physpages++;
 	return 0;
 }

 /*
  * Not currently handling the NUMA case.
  * Assuming single node and all memory that
  * has been added dynamically that would be
  * onlined here is in HIGHMEM
  */
 void online_page(struct page *page)
 {
 	ClearPageReserved(page);
 	add_one_highpage_hotplug(page, page_to_pfn(page));
 }


 #ifdef CONFIG_NUMA
 extern void set_highmem_pages_init(int);
 #else
 static void __init set_highmem_pages_init(int bad_ppro)
 {
 	int pfn;
 	for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
 		add_one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
 	totalram_pages += totalhigh_pages;
 }
 #endif /* CONFIG_FLATMEM */

 #else
 #define kmap_init() do { } while (0)
 #define permanent_kmaps_init(pgd_base) do { } while (0)
 #define set_highmem_pages_init(bad_ppro) do { } while (0)
 #endif /* CONFIG_HIGHMEM */

 unsigned long long __PAGE_KERNEL = _PAGE_KERNEL;
 EXPORT_SYMBOL(__PAGE_KERNEL);
 unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;

 #ifdef CONFIG_NUMA
 extern void __init remap_numa_kva(void);
 #else
 #define remap_numa_kva() do {} while (0)
 #endif

 static void __init pagetable_init (void)
 {
 	unsigned long vaddr;
 	pgd_t *pgd_base = swapper_pg_dir;

 #ifdef CONFIG_X86_PAE
 	int i;
 	/* Init entries of the first-level page table to the zero page */
 	for (i = 0; i < PTRS_PER_PGD; i++)
 		set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
 #endif

 	/* Enable PSE if available */
 	if (cpu_has_pse) {
 		set_in_cr4(X86_CR4_PSE);
 	}

 	/* Enable PGE if available */
 	if (cpu_has_pge) {
 		set_in_cr4(X86_CR4_PGE);
 		__PAGE_KERNEL |= _PAGE_GLOBAL;
 		__PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
 	}

 	kernel_physical_mapping_init(pgd_base);
 	remap_numa_kva();

 	/*
 	 * 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;
 	page_table_range_init(vaddr, 0, pgd_base);

 	permanent_kmaps_init(pgd_base);

 #ifdef CONFIG_X86_PAE
 	/*
 	 * Add low memory identity-mappings - SMP needs it when
 	 * starting up on an AP from real-mode. In the non-PAE
 	 * case we already have these mappings through head.S.
 	 * All user-space mappings are explicitly cleared after
 	 * SMP startup.
 	 */
 	set_pgd(&pgd_base[0], pgd_base[USER_PTRS_PER_PGD]);
 #endif
 }

 #ifdef CONFIG_SOFTWARE_SUSPEND
 /*
  * Swap suspend & friends need this for resume because things like the intel-agp
  * driver might have split up a kernel 4MB mapping.
  */
 char __nosavedata swsusp_pg_dir[PAGE_SIZE]
 	__attribute__ ((aligned (PAGE_SIZE)));

 static inline void save_pg_dir(void)
 {
 	memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
 }
 #else
 static inline void save_pg_dir(void)
 {
 }
 #endif

 void zap_low_mappings (void)
 {
 	int i;

 	save_pg_dir();

 	/*
 	 * Zap initial low-memory mappings.
 	 *
 	 * Note that "pgd_clear()" doesn't do it for
 	 * us, because pgd_clear() is a no-op on i386.
 	 */
 	for (i = 0; i < USER_PTRS_PER_PGD; i++)
 #ifdef CONFIG_X86_PAE
 		set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
 #else
 		set_pgd(swapper_pg_dir+i, __pgd(0));
 #endif
 	flush_tlb_all();
 }

 static int disable_nx __initdata = 0;
 u64 __supported_pte_mask __read_mostly = ~_PAGE_NX;

 /*
  * noexec = on|off
  *
  * Control non executable mappings.
  *
  * on      Enable
  * off     Disable
  */
 void __init noexec_setup(const char *str)
 {
 	if (!strncmp(str, "on",2) && cpu_has_nx) {
 		__supported_pte_mask |= _PAGE_NX;
 		disable_nx = 0;
 	} else if (!strncmp(str,"off",3)) {
 		disable_nx = 1;
 		__supported_pte_mask &= ~_PAGE_NX;
 	}
 }

 int nx_enabled = 0;
 #ifdef CONFIG_X86_PAE

 static void __init set_nx(void)
 {
 	unsigned int v[4], l, h;

 	if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
 		cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
 		if ((v[3] & (1 << 20)) && !disable_nx) {
 			rdmsr(MSR_EFER, l, h);
 			l |= EFER_NX;
 			wrmsr(MSR_EFER, l, h);
 			nx_enabled = 1;
 			__supported_pte_mask |= _PAGE_NX;
 		}
 	}
 }

 /*
  * Enables/disables executability of a given kernel page and
  * returns the previous setting.
  */
 int __init set_kernel_exec(unsigned long vaddr, int enable)
 {
 	pte_t *pte;
 	int ret = 1;

 	if (!nx_enabled)
 		goto out;

 	pte = lookup_address(vaddr);
 	BUG_ON(!pte);

 	if (!pte_exec_kernel(*pte))
 		ret = 0;

 	if (enable)
 		pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
 	else
 		pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
 	__flush_tlb_all();
 out:
 	return ret;
 }

 #endif

 /*
  * 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)
 {
 #ifdef CONFIG_X86_PAE
 	set_nx();
 	if (nx_enabled)
 		printk("NX (Execute Disable) protection: active\n");
 #endif

 	pagetable_init();

 	load_cr3(swapper_pg_dir);

 #ifdef CONFIG_X86_PAE
 	/*
 	 * We will bail out later - printk doesn't work right now so
 	 * the user would just see a hanging kernel.
 	 */
 	if (cpu_has_pae)
 		set_in_cr4(X86_CR4_PAE);
 #endif
 	__flush_tlb_all();

 	kmap_init();
 }

 /*
  * Test if the WP bit works in supervisor mode. It isn't supported on 386's
  * and also on some strange 486's (NexGen etc.). 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("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("No.\n");
 #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("Ok.\n");
 	}
 }

 static void __init set_max_mapnr_init(void)
 {
 #ifdef CONFIG_HIGHMEM
 	num_physpages = highend_pfn;
 #else
 	num_physpages = max_low_pfn;
 #endif
 #ifdef CONFIG_FLATMEM
 	max_mapnr = num_physpages;
 #endif
 }

 static struct kcore_list kcore_mem, kcore_vmalloc;

 void __init mem_init(void)
 {
 	extern int ppro_with_ram_bug(void);
 	int codesize, reservedpages, datasize, initsize;
 	int tmp;
 	int bad_ppro;

 #ifdef CONFIG_FLATMEM
 	if (!mem_map)
 		BUG();
 #endif

 	bad_ppro = ppro_with_ram_bug();

 #ifdef CONFIG_HIGHMEM
 	/* check that fixmap and pkmap do not overlap */
 	if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
 		printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
 		printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
 				PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
 		BUG();
 	}
 #endif

 	set_max_mapnr_init();

 #ifdef CONFIG_HIGHMEM
 	high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
 #else
 	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 #endif

 	/* 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++;

 	set_highmem_pages_init(bad_ppro);

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

 	kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT);
 	kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 		   VMALLOC_END-VMALLOC_START);

 	printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
 		(unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
 		num_physpages << (PAGE_SHIFT-10),
 		codesize >> 10,
 		reservedpages << (PAGE_SHIFT-10),
 		datasize >> 10,
 		initsize >> 10,
 		(unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
 	       );

 #ifdef CONFIG_X86_PAE
 	if (!cpu_has_pae)
 		panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
 #endif
 	if (boot_cpu_data.wp_works_ok < 0)
 		test_wp_bit();

 	/*
 	 * Subtle. SMP is doing it's boot stuff late (because it has to
 	 * fork idle threads) - but it also needs low mappings for the
 	 * protected-mode entry to work. We zap these entries only after
 	 * the WP-bit has been tested.
 	 */
 #ifndef CONFIG_SMP
 	zap_low_mappings();
 #endif
 }

 /*
  * this is for the non-NUMA, single node SMP system case.
  * Specifically, in the case of x86, we will always add
  * memory to the highmem for now.
  */
 #ifndef CONFIG_NEED_MULTIPLE_NODES
 int add_memory(u64 start, u64 size)
 {
 	struct pglist_data *pgdata = &contig_page_data;
 	struct zone *zone = pgdata->node_zones + MAX_NR_ZONES-1;
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;

 	return __add_pages(zone, start_pfn, nr_pages);
 }

 int remove_memory(u64 start, u64 size)
 {
 	return -EINVAL;
 }
 #endif

 kmem_cache_t *pgd_cache;
 kmem_cache_t *pmd_cache;

 void __init pgtable_cache_init(void)
 {
 	if (PTRS_PER_PMD > 1) {
 		pmd_cache = kmem_cache_create("pmd",
 					PTRS_PER_PMD*sizeof(pmd_t),
 					PTRS_PER_PMD*sizeof(pmd_t),
 					0,
 					pmd_ctor,
 					NULL);
 		if (!pmd_cache)
 			panic("pgtable_cache_init(): cannot create pmd cache");
 	}
 	pgd_cache = kmem_cache_create("pgd",
 				PTRS_PER_PGD*sizeof(pgd_t),
 				PTRS_PER_PGD*sizeof(pgd_t),
 				0,
 				pgd_ctor,
 				PTRS_PER_PMD == 1 ? pgd_dtor : NULL);
 	if (!pgd_cache)
 		panic("pgtable_cache_init(): Cannot create pgd cache");
 }

 /*
  * 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 int noinline do_test_wp_bit(void)
 {
 	char tmp_reg;
 	int flag;

 	__asm__ __volatile__(
 		"	movb %0,%1	\n"
 		"1:	movb %1,%0	\n"
 		"	xorl %2,%2	\n"
 		"2:			\n"
 		".section __ex_table,\"a\"\n"
 		"	.align 4	\n"
 		"	.long 1b,2b	\n"
 		".previous		\n"
 		:"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
 		 "=q" (tmp_reg),
 		 "=r" (flag)
 		:"2" (1)
 		:"memory");

 	return flag;
 }

 #ifdef CONFIG_DEBUG_RODATA

 extern char __start_rodata, __end_rodata;
 void mark_rodata_ro(void)
 {
 	unsigned long addr = (unsigned long)&__start_rodata;

 	for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
 		change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);

 	printk ("Write protecting the kernel read-only data: %luk\n",
 			(unsigned long)(&__end_rodata - &__start_rodata) >> 10);

 	/*
 	 * change_page_attr() requires a global_flush_tlb() call after it.
 	 * We do this after the printk so that if something went wrong in the
 	 * change, the printk gets out at least to give a better debug hint
 	 * of who is the culprit.
 	 */
 	global_flush_tlb();
 }
 #endif

 void free_init_pages(char *what, unsigned long begin, unsigned long end)
 {
 	unsigned long addr;

 	for (addr = begin; addr < end; addr += PAGE_SIZE) {
 		ClearPageReserved(virt_to_page(addr));
 		init_page_count(virt_to_page(addr));
 		memset((void *)addr, 0xcc, PAGE_SIZE);
 		free_page(addr);
 		totalram_pages++;
 	}
 	printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
 }

 void free_initmem(void)
 {
 	free_init_pages("unused kernel memory",
 			(unsigned long)(&__init_begin),
 			(unsigned long)(&__init_end));
 }

 #ifdef CONFIG_BLK_DEV_INITRD
 void free_initrd_mem(unsigned long start, unsigned long end)
 {
 	free_init_pages("initrd memory", start, end);
 }
 #endif
	/*
	* linux/arch/i386/mm/init.c
	*
	* Copyright (C) 1995 Linus Torvalds
	*
	* Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
	*/

	#include <linux/config.h>
	#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/bootmem.h>
	#include <linux/slab.h>
	#include <linux/proc_fs.h>
	#include <linux/efi.h>
	#include <linux/memory_hotplug.h>
	#include <linux/initrd.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/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/sections.h>

	unsigned int __VMALLOC_RESERVE = 128 << 20;

	DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
	unsigned long highstart_pfn, highend_pfn;

	static int noinline do_test_wp_bit(void);

	/*
	* 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
	pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
	set_pgd(pgd, __pgd(__pa(pmd_table) \| _PAGE_PRESENT));
	pud = pud_offset(pgd, 0);
	if (pmd_table != pmd_offset(pud, 0))
	BUG();
	#else
	pud = pud_offset(pgd, 0);
	pmd_table = pmd_offset(pud, 0);
	#endif

	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_none(*pmd)) {
	pte_t page_table = (pte_t ) alloc_bootmem_low_pages(PAGE_SIZE);
	set_pmd(pmd, __pmd(__pa(page_table) \| _PAGE_TABLE));
	if (page_table != pte_offset_kernel(pmd, 0))
	BUG();

	return page_table;
	}

	return pte_offset_kernel(pmd, 0);
	}

	/*
	* 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)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	int pgd_idx, pmd_idx;
	unsigned long vaddr;

	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++) {
	if (pgd_none(*pgd))
	one_md_table_init(pgd);
	pud = pud_offset(pgd, vaddr);
	pmd = pmd_offset(pud, vaddr);
	for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) {
	if (pmd_none(*pmd))
	one_page_table_init(pmd);

	vaddr += PMD_SIZE;
	}
	pmd_idx = 0;
	}
	}

	static inline int is_kernel_text(unsigned long addr)
	{
	if (addr >= PAGE_OFFSET && 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.
	*/
	static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
	{
	unsigned long pfn;
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t *pte;
	int pgd_idx, pmd_idx, pte_ofs;

	pgd_idx = pgd_index(PAGE_OFFSET);
	pgd = pgd_base + pgd_idx;
	pfn = 0;

	for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
	pmd = one_md_table_init(pgd);
	if (pfn >= max_low_pfn)
	continue;
	for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
	unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;

	/* Map with big pages if possible, otherwise create normal page tables. */
	if (cpu_has_pse) {
	unsigned int address2 = (pfn + PTRS_PER_PTE - 1) * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;

	if (is_kernel_text(address) \|\| is_kernel_text(address2))
	set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
	else
	set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));
	pfn += PTRS_PER_PTE;
	} else {
	pte = one_page_table_init(pmd);

	for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn; pte++, pfn++, pte_ofs++) {
	if (is_kernel_text(address))
	set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
	else
	set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));
	}
	}
	}
	}
	}

	static inline int page_kills_ppro(unsigned long pagenr)
	{
	if (pagenr >= 0x70000 && pagenr <= 0x7003F)
	return 1;
	return 0;
	}

	extern int is_available_memory(efi_memory_desc_t *);

	int page_is_ram(unsigned long pagenr)
	{
	int i;
	unsigned long addr, end;

	if (efi_enabled) {
	efi_memory_desc_t *md;
	void *p;

	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
	md = p;
	if (!is_available_memory(md))
	continue;
	addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
	end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;

	if ((pagenr >= addr) && (pagenr < end))
	return 1;
	}
	return 0;
	}

	for (i = 0; i < e820.nr_map; i++) {

	if (e820.map[i].type != E820_RAM) /* not usable memory */
	continue;
	/*
	* !!!FIXME!!! Some BIOSen report areas as RAM that
	* are not. Notably the 640->1Mb area. We need a sanity
	* check here.
	*/
	addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
	end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
	if ((pagenr >= addr) && (pagenr < end))
	return 1;
	}
	return 0;
	}

	#ifdef CONFIG_HIGHMEM
	pte_t *kmap_pte;
	pgprot_t kmap_prot;

	#define kmap_get_fixmap_pte(vaddr) \
	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;
	}

	static void __init permanent_kmaps_init(pgd_t *pgd_base)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	unsigned long vaddr;

	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 __meminit free_new_highpage(struct page *page)
	{
	init_page_count(page);
	__free_page(page);
	totalhigh_pages++;
	}

	void __init add_one_highpage_init(struct page *page, int pfn, int bad_ppro)
	{
	if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
	ClearPageReserved(page);
	free_new_highpage(page);
	} else
	SetPageReserved(page);
	}

	static int add_one_highpage_hotplug(struct page *page, unsigned long pfn)
	{
	free_new_highpage(page);
	totalram_pages++;
	#ifdef CONFIG_FLATMEM
	max_mapnr = max(pfn, max_mapnr);
	#endif
	num_physpages++;
	return 0;
	}

	/*
	* Not currently handling the NUMA case.
	* Assuming single node and all memory that
	* has been added dynamically that would be
	* onlined here is in HIGHMEM
	*/
	void online_page(struct page *page)
	{
	ClearPageReserved(page);
	add_one_highpage_hotplug(page, page_to_pfn(page));
	}


	#ifdef CONFIG_NUMA
	extern void set_highmem_pages_init(int);
	#else
	static void __init set_highmem_pages_init(int bad_ppro)
	{
	int pfn;
	for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
	add_one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
	totalram_pages += totalhigh_pages;
	}
	#endif /* CONFIG_FLATMEM */

	#else
	#define kmap_init() do { } while (0)
	#define permanent_kmaps_init(pgd_base) do { } while (0)
	#define set_highmem_pages_init(bad_ppro) do { } while (0)
	#endif /* CONFIG_HIGHMEM */

	unsigned long long __PAGE_KERNEL = _PAGE_KERNEL;
	EXPORT_SYMBOL(__PAGE_KERNEL);
	unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;

	#ifdef CONFIG_NUMA
	extern void __init remap_numa_kva(void);
	#else
	#define remap_numa_kva() do {} while (0)
	#endif

	static void __init pagetable_init (void)
	{
	unsigned long vaddr;
	pgd_t *pgd_base = swapper_pg_dir;

	#ifdef CONFIG_X86_PAE
	int i;
	/* Init entries of the first-level page table to the zero page */
	for (i = 0; i < PTRS_PER_PGD; i++)
	set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) \| _PAGE_PRESENT));
	#endif

	/* Enable PSE if available */
	if (cpu_has_pse) {
	set_in_cr4(X86_CR4_PSE);
	}

	/* Enable PGE if available */
	if (cpu_has_pge) {
	set_in_cr4(X86_CR4_PGE);
	__PAGE_KERNEL \|= _PAGE_GLOBAL;
	__PAGE_KERNEL_EXEC \|= _PAGE_GLOBAL;
	}

	kernel_physical_mapping_init(pgd_base);
	remap_numa_kva();

	/*
	* 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;
	page_table_range_init(vaddr, 0, pgd_base);

	permanent_kmaps_init(pgd_base);

	#ifdef CONFIG_X86_PAE
	/*
	* Add low memory identity-mappings - SMP needs it when
	* starting up on an AP from real-mode. In the non-PAE
	* case we already have these mappings through head.S.
	* All user-space mappings are explicitly cleared after
	* SMP startup.
	*/
	set_pgd(&pgd_base[0], pgd_base[USER_PTRS_PER_PGD]);
	#endif
	}

	#ifdef CONFIG_SOFTWARE_SUSPEND
	/*
	* Swap suspend & friends need this for resume because things like the intel-agp
	* driver might have split up a kernel 4MB mapping.
	*/
	char __nosavedata swsusp_pg_dir[PAGE_SIZE]
	__attribute__ ((aligned (PAGE_SIZE)));

	static inline void save_pg_dir(void)
	{
	memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
	}
	#else
	static inline void save_pg_dir(void)
	{
	}
	#endif

	void zap_low_mappings (void)
	{
	int i;

	save_pg_dir();

	/*
	* Zap initial low-memory mappings.
	*
	* Note that "pgd_clear()" doesn't do it for
	* us, because pgd_clear() is a no-op on i386.
	*/
	for (i = 0; i < USER_PTRS_PER_PGD; i++)
	#ifdef CONFIG_X86_PAE
	set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
	#else
	set_pgd(swapper_pg_dir+i, __pgd(0));
	#endif
	flush_tlb_all();
	}

	static int disable_nx __initdata = 0;
	u64 __supported_pte_mask __read_mostly = ~_PAGE_NX;

	/*
	* noexec = on\|off
	*
	* Control non executable mappings.
	*
	* on Enable
	* off Disable
	*/
	void __init noexec_setup(const char *str)
	{
	if (!strncmp(str, "on",2) && cpu_has_nx) {
	__supported_pte_mask \|= _PAGE_NX;
	disable_nx = 0;
	} else if (!strncmp(str,"off",3)) {
	disable_nx = 1;
	__supported_pte_mask &= ~_PAGE_NX;
	}
	}

	int nx_enabled = 0;
	#ifdef CONFIG_X86_PAE

	static void __init set_nx(void)
	{
	unsigned int v[4], l, h;

	if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
	cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
	if ((v[3] & (1 << 20)) && !disable_nx) {
	rdmsr(MSR_EFER, l, h);
	l \|= EFER_NX;
	wrmsr(MSR_EFER, l, h);
	nx_enabled = 1;
	__supported_pte_mask \|= _PAGE_NX;
	}
	}
	}

	/*
	* Enables/disables executability of a given kernel page and
	* returns the previous setting.
	*/
	int __init set_kernel_exec(unsigned long vaddr, int enable)
	{
	pte_t *pte;
	int ret = 1;

	if (!nx_enabled)
	goto out;

	pte = lookup_address(vaddr);
	BUG_ON(!pte);

	if (!pte_exec_kernel(*pte))
	ret = 0;

	if (enable)
	pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
	else
	pte->pte_high \|= 1 << (_PAGE_BIT_NX - 32);
	__flush_tlb_all();
	out:
	return ret;
	}

	#endif

	/*
	* 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)
	{
	#ifdef CONFIG_X86_PAE
	set_nx();
	if (nx_enabled)
	printk("NX (Execute Disable) protection: active\n");
	#endif

	pagetable_init();

	load_cr3(swapper_pg_dir);

	#ifdef CONFIG_X86_PAE
	/*
	* We will bail out later - printk doesn't work right now so
	* the user would just see a hanging kernel.
	*/
	if (cpu_has_pae)
	set_in_cr4(X86_CR4_PAE);
	#endif
	__flush_tlb_all();

	kmap_init();
	}

	/*
	* Test if the WP bit works in supervisor mode. It isn't supported on 386's
	* and also on some strange 486's (NexGen etc.). 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("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("No.\n");
	#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("Ok.\n");
	}
	}

	static void __init set_max_mapnr_init(void)
	{
	#ifdef CONFIG_HIGHMEM
	num_physpages = highend_pfn;
	#else
	num_physpages = max_low_pfn;
	#endif
	#ifdef CONFIG_FLATMEM
	max_mapnr = num_physpages;
	#endif
	}

	static struct kcore_list kcore_mem, kcore_vmalloc;

	void __init mem_init(void)
	{
	extern int ppro_with_ram_bug(void);
	int codesize, reservedpages, datasize, initsize;
	int tmp;
	int bad_ppro;

	#ifdef CONFIG_FLATMEM
	if (!mem_map)
	BUG();
	#endif

	bad_ppro = ppro_with_ram_bug();

	#ifdef CONFIG_HIGHMEM
	/* check that fixmap and pkmap do not overlap */
	if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
	printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
	printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
	PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
	BUG();
	}
	#endif

	set_max_mapnr_init();

	#ifdef CONFIG_HIGHMEM
	high_memory = (void ) __va(highstart_pfn PAGE_SIZE - 1) + 1;
	#else
	high_memory = (void ) __va(max_low_pfn PAGE_SIZE - 1) + 1;
	#endif

	/* 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++;

	set_highmem_pages_init(bad_ppro);

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

	kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT);
	kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
	VMALLOC_END-VMALLOC_START);

	printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
	(unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
	num_physpages << (PAGE_SHIFT-10),
	codesize >> 10,
	reservedpages << (PAGE_SHIFT-10),
	datasize >> 10,
	initsize >> 10,
	(unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
	);

	#ifdef CONFIG_X86_PAE
	if (!cpu_has_pae)
	panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
	#endif
	if (boot_cpu_data.wp_works_ok < 0)
	test_wp_bit();

	/*
	* Subtle. SMP is doing it's boot stuff late (because it has to
	* fork idle threads) - but it also needs low mappings for the
	* protected-mode entry to work. We zap these entries only after
	* the WP-bit has been tested.
	*/
	#ifndef CONFIG_SMP
	zap_low_mappings();
	#endif
	}

	/*
	* this is for the non-NUMA, single node SMP system case.
	* Specifically, in the case of x86, we will always add
	* memory to the highmem for now.
	*/
	#ifndef CONFIG_NEED_MULTIPLE_NODES
	int add_memory(u64 start, u64 size)
	{
	struct pglist_data *pgdata = &contig_page_data;
	struct zone *zone = pgdata->node_zones + MAX_NR_ZONES-1;
	unsigned long start_pfn = start >> PAGE_SHIFT;
	unsigned long nr_pages = size >> PAGE_SHIFT;

	return __add_pages(zone, start_pfn, nr_pages);
	}

	int remove_memory(u64 start, u64 size)
	{
	return -EINVAL;
	}
	#endif

	kmem_cache_t *pgd_cache;
	kmem_cache_t *pmd_cache;

	void __init pgtable_cache_init(void)
	{
	if (PTRS_PER_PMD > 1) {
	pmd_cache = kmem_cache_create("pmd",
	PTRS_PER_PMD*sizeof(pmd_t),
	PTRS_PER_PMD*sizeof(pmd_t),
	0,
	pmd_ctor,
	NULL);
	if (!pmd_cache)
	panic("pgtable_cache_init(): cannot create pmd cache");
	}
	pgd_cache = kmem_cache_create("pgd",
	PTRS_PER_PGD*sizeof(pgd_t),
	PTRS_PER_PGD*sizeof(pgd_t),
	0,
	pgd_ctor,
	PTRS_PER_PMD == 1 ? pgd_dtor : NULL);
	if (!pgd_cache)
	panic("pgtable_cache_init(): Cannot create pgd cache");
	}

	/*
	* 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 int noinline do_test_wp_bit(void)
	{
	char tmp_reg;
	int flag;

	__asm__ __volatile__(
	" movb %0,%1 \n"
	"1: movb %1,%0 \n"
	" xorl %2,%2 \n"
	"2: \n"
	".section __ex_table,\"a\"\n"
	" .align 4 \n"
	" .long 1b,2b \n"
	".previous \n"
	:"=m" ((char )fix_to_virt(FIX_WP_TEST)),
	"=q" (tmp_reg),
	"=r" (flag)
	:"2" (1)
	:"memory");

	return flag;
	}

	#ifdef CONFIG_DEBUG_RODATA

	extern char __start_rodata, __end_rodata;
	void mark_rodata_ro(void)
	{
	unsigned long addr = (unsigned long)&__start_rodata;

	for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
	change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);

	printk ("Write protecting the kernel read-only data: %luk\n",
	(unsigned long)(&__end_rodata - &__start_rodata) >> 10);

	/*
	* change_page_attr() requires a global_flush_tlb() call after it.
	* We do this after the printk so that if something went wrong in the
	* change, the printk gets out at least to give a better debug hint
	* of who is the culprit.
	*/
	global_flush_tlb();
	}
	#endif

	void free_init_pages(char *what, unsigned long begin, unsigned long end)
	{
	unsigned long addr;

	for (addr = begin; addr < end; addr += PAGE_SIZE) {
	ClearPageReserved(virt_to_page(addr));
	init_page_count(virt_to_page(addr));
	memset((void *)addr, 0xcc, PAGE_SIZE);
	free_page(addr);
	totalram_pages++;
	}
	printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
	}

	void free_initmem(void)
	{
	free_init_pages("unused kernel memory",
	(unsigned long)(&__init_begin),
	(unsigned long)(&__init_end));
	}

	#ifdef CONFIG_BLK_DEV_INITRD
	void free_initrd_mem(unsigned long start, unsigned long end)
	{
	free_init_pages("initrd memory", start, end);
	}
	#endif