arch/arm64/mm/ptdump.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
  * Debug helper to dump the current kernel pagetables of the system
  * so that we can see what the various memory ranges are set to.
  *
  * Derived from x86 and arm implementation:
  * (C) Copyright 2008 Intel Corporation
  *
  * Author: Arjan van de Ven <arjan@linux.intel.com>
  */
 #include <linux/debugfs.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/io.h>
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/ptdump.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>

 #include <asm/fixmap.h>
 #include <asm/kasan.h>
 #include <asm/memory.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/ptdump.h>


 enum address_markers_idx {
 	PAGE_OFFSET_NR = 0,
 	PAGE_END_NR,
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	KASAN_START_NR,
 #endif
 };

 static struct addr_marker address_markers[] = {
 	{ PAGE_OFFSET,			"Linear Mapping start" },
 	{ 0 /* PAGE_END */,		"Linear Mapping end" },
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	{ 0 /* KASAN_SHADOW_START */,	"Kasan shadow start" },
 	{ KASAN_SHADOW_END,		"Kasan shadow end" },
 #endif
 	{ BPF_JIT_REGION_START,		"BPF start" },
 	{ BPF_JIT_REGION_END,		"BPF end" },
 	{ MODULES_VADDR,		"Modules start" },
 	{ MODULES_END,			"Modules end" },
 	{ VMALLOC_START,		"vmalloc() area" },
 	{ VMALLOC_END,			"vmalloc() end" },
 	{ FIXADDR_START,		"Fixmap start" },
 	{ FIXADDR_TOP,			"Fixmap end" },
 	{ PCI_IO_START,			"PCI I/O start" },
 	{ PCI_IO_END,			"PCI I/O end" },
 	{ VMEMMAP_START,		"vmemmap start" },
 	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },
 	{ -1,				NULL },
 };

 #define pt_dump_seq_printf(m, fmt, args...)	\
 ({						\
 	if (m)					\
 		seq_printf(m, fmt, ##args);	\
 })

 #define pt_dump_seq_puts(m, fmt)	\
 ({					\
 	if (m)				\
 		seq_printf(m, fmt);	\
 })

 /*
  * The page dumper groups page table entries of the same type into a single
  * description. It uses pg_state to track the range information while
  * iterating over the pte entries. When the continuity is broken it then
  * dumps out a description of the range.
  */
 struct pg_state {
 	struct ptdump_state ptdump;
 	struct seq_file *seq;
 	const struct addr_marker *marker;
 	unsigned long start_address;
 	int level;
 	u64 current_prot;
 	bool check_wx;
 	unsigned long wx_pages;
 	unsigned long uxn_pages;
 };

 struct prot_bits {
 	u64		mask;
 	u64		val;
 	const char	*set;
 	const char	*clear;
 };

 static const struct prot_bits pte_bits[] = {
 	{
 		.mask	= PTE_VALID,
 		.val	= PTE_VALID,
 		.set	= " ",
 		.clear	= "F",
 	}, {
 		.mask	= PTE_USER,
 		.val	= PTE_USER,
 		.set	= "USR",
 		.clear	= "   ",
 	}, {
 		.mask	= PTE_RDONLY,
 		.val	= PTE_RDONLY,
 		.set	= "ro",
 		.clear	= "RW",
 	}, {
 		.mask	= PTE_PXN,
 		.val	= PTE_PXN,
 		.set	= "NX",
 		.clear	= "x ",
 	}, {
 		.mask	= PTE_SHARED,
 		.val	= PTE_SHARED,
 		.set	= "SHD",
 		.clear	= "   ",
 	}, {
 		.mask	= PTE_AF,
 		.val	= PTE_AF,
 		.set	= "AF",
 		.clear	= "  ",
 	}, {
 		.mask	= PTE_NG,
 		.val	= PTE_NG,
 		.set	= "NG",
 		.clear	= "  ",
 	}, {
 		.mask	= PTE_CONT,
 		.val	= PTE_CONT,
 		.set	= "CON",
 		.clear	= "   ",
 	}, {
 		.mask	= PTE_TABLE_BIT,
 		.val	= PTE_TABLE_BIT,
 		.set	= "   ",
 		.clear	= "BLK",
 	}, {
 		.mask	= PTE_UXN,
 		.val	= PTE_UXN,
 		.set	= "UXN",
 		.clear	= "   ",
 	}, {
 		.mask	= PTE_GP,
 		.val	= PTE_GP,
 		.set	= "GP",
 		.clear	= "  ",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_DEVICE_nGnRnE),
 		.set	= "DEVICE/nGnRnE",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_DEVICE_nGnRE),
 		.set	= "DEVICE/nGnRE",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_NORMAL_NC),
 		.set	= "MEM/NORMAL-NC",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_NORMAL),
 		.set	= "MEM/NORMAL",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_NORMAL_TAGGED),
 		.set	= "MEM/NORMAL-TAGGED",
 	}
 };

 struct pg_level {
 	const struct prot_bits *bits;
 	const char *name;
 	size_t num;
 	u64 mask;
 };

 static struct pg_level pg_level[] = {
 	{ /* pgd */
 		.name	= "PGD",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
 	}, { /* p4d */
 		.name	= "P4D",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
 	}, { /* pud */
 		.name	= (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
 	}, { /* pmd */
 		.name	= (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
 	}, { /* pte */
 		.name	= "PTE",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
 	},
 };

 static void dump_prot(struct pg_state *st, const struct prot_bits *bits,
 			size_t num)
 {
 	unsigned i;

 	for (i = 0; i < num; i++, bits++) {
 		const char *s;

 		if ((st->current_prot & bits->mask) == bits->val)
 			s = bits->set;
 		else
 			s = bits->clear;

 		if (s)
 			pt_dump_seq_printf(st->seq, " %s", s);
 	}
 }

 static void note_prot_uxn(struct pg_state *st, unsigned long addr)
 {
 	if (!st->check_wx)
 		return;

 	if ((st->current_prot & PTE_UXN) == PTE_UXN)
 		return;

 	WARN_ONCE(1, "arm64/mm: Found non-UXN mapping at address %p/%pS\n",
 		  (void *)st->start_address, (void *)st->start_address);

 	st->uxn_pages += (addr - st->start_address) / PAGE_SIZE;
 }

 static void note_prot_wx(struct pg_state *st, unsigned long addr)
 {
 	if (!st->check_wx)
 		return;
 	if ((st->current_prot & PTE_RDONLY) == PTE_RDONLY)
 		return;
 	if ((st->current_prot & PTE_PXN) == PTE_PXN)
 		return;

 	WARN_ONCE(1, "arm64/mm: Found insecure W+X mapping at address %p/%pS\n",
 		  (void *)st->start_address, (void *)st->start_address);

 	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
 }

 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 		      u64 val)
 {
 	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
 	static const char units[] = "KMGTPE";
 	u64 prot = 0;

 	if (level >= 0)
 		prot = val & pg_level[level].mask;

 	if (st->level == -1) {
 		st->level = level;
 		st->current_prot = prot;
 		st->start_address = addr;
 		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 	} else if (prot != st->current_prot || level != st->level ||
 		   addr >= st->marker[1].start_address) {
 		const char *unit = units;
 		unsigned long delta;

 		if (st->current_prot) {
 			note_prot_uxn(st, addr);
 			note_prot_wx(st, addr);
 		}

 		pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx   ",
 				   st->start_address, addr);

 		delta = (addr - st->start_address) >> 10;
 		while (!(delta & 1023) && unit[1]) {
 			delta >>= 10;
 			unit++;
 		}
 		pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
 				   pg_level[st->level].name);
 		if (st->current_prot && pg_level[st->level].bits)
 			dump_prot(st, pg_level[st->level].bits,
 				  pg_level[st->level].num);
 		pt_dump_seq_puts(st->seq, "\n");

 		if (addr >= st->marker[1].start_address) {
 			st->marker++;
 			pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 		}

 		st->start_address = addr;
 		st->current_prot = prot;
 		st->level = level;
 	}

 	if (addr >= st->marker[1].start_address) {
 		st->marker++;
 		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 	}

 }

 void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
 {
 	unsigned long end = ~0UL;
 	struct pg_state st;

 	if (info->base_addr < TASK_SIZE_64)
 		end = TASK_SIZE_64;

 	st = (struct pg_state){
 		.seq = s,
 		.marker = info->markers,
 		.level = -1,
 		.ptdump = {
 			.note_page = note_page,
 			.range = (struct ptdump_range[]){
 				{info->base_addr, end},
 				{0, 0}
 			}
 		}
 	};

 	ptdump_walk_pgd(&st.ptdump, info->mm, NULL);
 }

 static void __init ptdump_initialize(void)
 {
 	unsigned i, j;

 	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
 		if (pg_level[i].bits)
 			for (j = 0; j < pg_level[i].num; j++)
 				pg_level[i].mask |= pg_level[i].bits[j].mask;
 }

 static struct ptdump_info kernel_ptdump_info = {
 	.mm		= &init_mm,
 	.markers	= address_markers,
 	.base_addr	= PAGE_OFFSET,
 };

 void ptdump_check_wx(void)
 {
 	struct pg_state st = {
 		.seq = NULL,
 		.marker = (struct addr_marker[]) {
 			{ 0, NULL},
 			{ -1, NULL},
 		},
 		.level = -1,
 		.check_wx = true,
 		.ptdump = {
 			.note_page = note_page,
 			.range = (struct ptdump_range[]) {
 				{PAGE_OFFSET, ~0UL},
 				{0, 0}
 			}
 		}
 	};

 	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);

 	if (st.wx_pages || st.uxn_pages)
 		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
 			st.wx_pages, st.uxn_pages);
 	else
 		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 }

 static int __init ptdump_init(void)
 {
 	address_markers[PAGE_END_NR].start_address = PAGE_END;
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	address_markers[KASAN_START_NR].start_address = KASAN_SHADOW_START;
 #endif
 	ptdump_initialize();
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
 	return 0;
 }
 device_initcall(ptdump_init);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (c) 2014, The Linux Foundation. All rights reserved.
	* Debug helper to dump the current kernel pagetables of the system
	* so that we can see what the various memory ranges are set to.
	*
	* Derived from x86 and arm implementation:
	* (C) Copyright 2008 Intel Corporation
	*
	* Author: Arjan van de Ven <arjan@linux.intel.com>
	*/
	#include <linux/debugfs.h>
	#include <linux/errno.h>
	#include <linux/fs.h>
	#include <linux/io.h>
	#include <linux/init.h>
	#include <linux/mm.h>
	#include <linux/ptdump.h>
	#include <linux/sched.h>
	#include <linux/seq_file.h>

	#include <asm/fixmap.h>
	#include <asm/kasan.h>
	#include <asm/memory.h>
	#include <asm/pgtable-hwdef.h>
	#include <asm/ptdump.h>


	enum address_markers_idx {
	PAGE_OFFSET_NR = 0,
	PAGE_END_NR,
	#if defined(CONFIG_KASAN_GENERIC) \|\| defined(CONFIG_KASAN_SW_TAGS)
	KASAN_START_NR,
	#endif
	};

	static struct addr_marker address_markers[] = {
	{ PAGE_OFFSET, "Linear Mapping start" },
	{ 0 /* PAGE_END */, "Linear Mapping end" },
	#if defined(CONFIG_KASAN_GENERIC) \|\| defined(CONFIG_KASAN_SW_TAGS)
	{ 0 /* KASAN_SHADOW_START */, "Kasan shadow start" },
	{ KASAN_SHADOW_END, "Kasan shadow end" },
	#endif
	{ BPF_JIT_REGION_START, "BPF start" },
	{ BPF_JIT_REGION_END, "BPF end" },
	{ MODULES_VADDR, "Modules start" },
	{ MODULES_END, "Modules end" },
	{ VMALLOC_START, "vmalloc() area" },
	{ VMALLOC_END, "vmalloc() end" },
	{ FIXADDR_START, "Fixmap start" },
	{ FIXADDR_TOP, "Fixmap end" },
	{ PCI_IO_START, "PCI I/O start" },
	{ PCI_IO_END, "PCI I/O end" },
	{ VMEMMAP_START, "vmemmap start" },
	{ VMEMMAP_START + VMEMMAP_SIZE, "vmemmap end" },
	{ -1, NULL },
	};

	#define pt_dump_seq_printf(m, fmt, args...) \
	({ \
	if (m) \
	seq_printf(m, fmt, ##args); \
	})

	#define pt_dump_seq_puts(m, fmt) \
	({ \
	if (m) \
	seq_printf(m, fmt); \
	})

	/*
	* The page dumper groups page table entries of the same type into a single
	* description. It uses pg_state to track the range information while
	* iterating over the pte entries. When the continuity is broken it then
	* dumps out a description of the range.
	*/
	struct pg_state {
	struct ptdump_state ptdump;
	struct seq_file *seq;
	const struct addr_marker *marker;
	unsigned long start_address;
	int level;
	u64 current_prot;
	bool check_wx;
	unsigned long wx_pages;
	unsigned long uxn_pages;
	};

	struct prot_bits {
	u64 mask;
	u64 val;
	const char *set;
	const char *clear;
	};

	static const struct prot_bits pte_bits[] = {
	{
	.mask = PTE_VALID,
	.val = PTE_VALID,
	.set = " ",
	.clear = "F",
	}, {
	.mask = PTE_USER,
	.val = PTE_USER,
	.set = "USR",
	.clear = " ",
	}, {
	.mask = PTE_RDONLY,
	.val = PTE_RDONLY,
	.set = "ro",
	.clear = "RW",
	}, {
	.mask = PTE_PXN,
	.val = PTE_PXN,
	.set = "NX",
	.clear = "x ",
	}, {
	.mask = PTE_SHARED,
	.val = PTE_SHARED,
	.set = "SHD",
	.clear = " ",
	}, {
	.mask = PTE_AF,
	.val = PTE_AF,
	.set = "AF",
	.clear = " ",
	}, {
	.mask = PTE_NG,
	.val = PTE_NG,
	.set = "NG",
	.clear = " ",
	}, {
	.mask = PTE_CONT,
	.val = PTE_CONT,
	.set = "CON",
	.clear = " ",
	}, {
	.mask = PTE_TABLE_BIT,
	.val = PTE_TABLE_BIT,
	.set = " ",
	.clear = "BLK",
	}, {
	.mask = PTE_UXN,
	.val = PTE_UXN,
	.set = "UXN",
	.clear = " ",
	}, {
	.mask = PTE_GP,
	.val = PTE_GP,
	.set = "GP",
	.clear = " ",
	}, {
	.mask = PTE_ATTRINDX_MASK,
	.val = PTE_ATTRINDX(MT_DEVICE_nGnRnE),
	.set = "DEVICE/nGnRnE",
	}, {
	.mask = PTE_ATTRINDX_MASK,
	.val = PTE_ATTRINDX(MT_DEVICE_nGnRE),
	.set = "DEVICE/nGnRE",
	}, {
	.mask = PTE_ATTRINDX_MASK,
	.val = PTE_ATTRINDX(MT_NORMAL_NC),
	.set = "MEM/NORMAL-NC",
	}, {
	.mask = PTE_ATTRINDX_MASK,
	.val = PTE_ATTRINDX(MT_NORMAL),
	.set = "MEM/NORMAL",
	}, {
	.mask = PTE_ATTRINDX_MASK,
	.val = PTE_ATTRINDX(MT_NORMAL_TAGGED),
	.set = "MEM/NORMAL-TAGGED",
	}
	};

	struct pg_level {
	const struct prot_bits *bits;
	const char *name;
	size_t num;
	u64 mask;
	};

	static struct pg_level pg_level[] = {
	{ /* pgd */
	.name = "PGD",
	.bits = pte_bits,
	.num = ARRAY_SIZE(pte_bits),
	}, { /* p4d */
	.name = "P4D",
	.bits = pte_bits,
	.num = ARRAY_SIZE(pte_bits),
	}, { /* pud */
	.name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
	.bits = pte_bits,
	.num = ARRAY_SIZE(pte_bits),
	}, { /* pmd */
	.name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
	.bits = pte_bits,
	.num = ARRAY_SIZE(pte_bits),
	}, { /* pte */
	.name = "PTE",
	.bits = pte_bits,
	.num = ARRAY_SIZE(pte_bits),
	},
	};

	static void dump_prot(struct pg_state st, const struct prot_bits bits,
	size_t num)
	{
	unsigned i;

	for (i = 0; i < num; i++, bits++) {
	const char *s;

	if ((st->current_prot & bits->mask) == bits->val)
	s = bits->set;
	else
	s = bits->clear;

	if (s)
	pt_dump_seq_printf(st->seq, " %s", s);
	}
	}

	static void note_prot_uxn(struct pg_state *st, unsigned long addr)
	{
	if (!st->check_wx)
	return;

	if ((st->current_prot & PTE_UXN) == PTE_UXN)
	return;

	WARN_ONCE(1, "arm64/mm: Found non-UXN mapping at address %p/%pS\n",
	(void )st->start_address, (void )st->start_address);

	st->uxn_pages += (addr - st->start_address) / PAGE_SIZE;
	}

	static void note_prot_wx(struct pg_state *st, unsigned long addr)
	{
	if (!st->check_wx)
	return;
	if ((st->current_prot & PTE_RDONLY) == PTE_RDONLY)
	return;
	if ((st->current_prot & PTE_PXN) == PTE_PXN)
	return;

	WARN_ONCE(1, "arm64/mm: Found insecure W+X mapping at address %p/%pS\n",
	(void )st->start_address, (void )st->start_address);

	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
	}

	static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
	u64 val)
	{
	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
	static const char units[] = "KMGTPE";
	u64 prot = 0;

	if (level >= 0)
	prot = val & pg_level[level].mask;

	if (st->level == -1) {
	st->level = level;
	st->current_prot = prot;
	st->start_address = addr;
	pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
	} else if (prot != st->current_prot \|\| level != st->level \|\|
	addr >= st->marker[1].start_address) {
	const char *unit = units;
	unsigned long delta;

	if (st->current_prot) {
	note_prot_uxn(st, addr);
	note_prot_wx(st, addr);
	}

	pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx ",
	st->start_address, addr);

	delta = (addr - st->start_address) >> 10;
	while (!(delta & 1023) && unit[1]) {
	delta >>= 10;
	unit++;
	}
	pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
	pg_level[st->level].name);
	if (st->current_prot && pg_level[st->level].bits)
	dump_prot(st, pg_level[st->level].bits,
	pg_level[st->level].num);
	pt_dump_seq_puts(st->seq, "\n");

	if (addr >= st->marker[1].start_address) {
	st->marker++;
	pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
	}

	st->start_address = addr;
	st->current_prot = prot;
	st->level = level;
	}

	if (addr >= st->marker[1].start_address) {
	st->marker++;
	pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
	}

	}

	void ptdump_walk(struct seq_file s, struct ptdump_info info)
	{
	unsigned long end = ~0UL;
	struct pg_state st;

	if (info->base_addr < TASK_SIZE_64)
	end = TASK_SIZE_64;

	st = (struct pg_state){
	.seq = s,
	.marker = info->markers,
	.level = -1,
	.ptdump = {
	.note_page = note_page,
	.range = (struct ptdump_range[]){
	{info->base_addr, end},
	{0, 0}
	}
	}
	};

	ptdump_walk_pgd(&st.ptdump, info->mm, NULL);
	}

	static void __init ptdump_initialize(void)
	{
	unsigned i, j;

	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
	if (pg_level[i].bits)
	for (j = 0; j < pg_level[i].num; j++)
	pg_level[i].mask \|= pg_level[i].bits[j].mask;
	}

	static struct ptdump_info kernel_ptdump_info = {
	.mm = &init_mm,
	.markers = address_markers,
	.base_addr = PAGE_OFFSET,
	};

	void ptdump_check_wx(void)
	{
	struct pg_state st = {
	.seq = NULL,
	.marker = (struct addr_marker[]) {
	{ 0, NULL},
	{ -1, NULL},
	},
	.level = -1,
	.check_wx = true,
	.ptdump = {
	.note_page = note_page,
	.range = (struct ptdump_range[]) {
	{PAGE_OFFSET, ~0UL},
	{0, 0}
	}
	}
	};

	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);

	if (st.wx_pages \|\| st.uxn_pages)
	pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
	st.wx_pages, st.uxn_pages);
	else
	pr_info("Checked W+X mappings: passed, no W+X pages found\n");
	}

	static int __init ptdump_init(void)
	{
	address_markers[PAGE_END_NR].start_address = PAGE_END;
	#if defined(CONFIG_KASAN_GENERIC) \|\| defined(CONFIG_KASAN_SW_TAGS)
	address_markers[KASAN_START_NR].start_address = KASAN_SHADOW_START;
	#endif
	ptdump_initialize();
	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
	return 0;
	}
	device_initcall(ptdump_init);