Commit 8eb07b18 authored by Rashmica Gupta's avatar Rashmica Gupta Committed by Michael Ellerman
Browse files

powerpc/mm: Dump linux pagetables 



Useful to be able to dump the kernels page tables to check permissions
and memory types - derived from arm64's implementation.

Add a debugfs file to check the page tables. To use this the PPC_PTDUMP
config option must be selected.

Signed-off-by: default avatarRashmica Gupta <rashmicy@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 8f272a5d

arch/powerpc/Kconfig.debug

+12 −0
Original line number Diff line number Diff line
@@ -354,4 +354,16 @@ config FAIL_IOMMU 


	  If you are unsure, say N.



config PPC_PTDUMP

        bool "Export kernel pagetable layout to userspace via debugfs"

        depends on DEBUG_KERNEL

        select DEBUG_FS

        help

	  This option exports the state of the kernel pagetables to a

	  debugfs file. This is only useful for kernel developers who are

	  working in architecture specific areas of the kernel - probably

	  not a good idea to enable this feature in a production kernel.



	  If you are unsure, say N.



endmenu

arch/powerpc/mm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -42,3 +42,4 @@ obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o 
obj-$(CONFIG_HIGHMEM)		+= highmem.o

obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o

obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_iommu.o

obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o

arch/powerpc/mm/dump_linuxpagetables.c

0 → 100644
+440 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2016, Rashmica Gupta, IBM Corp.

 *

 * This traverses the kernel pagetables and dumps the

 * information about the used sections of memory to

 * /sys/kernel/debug/kernel_pagetables.

 *

 * Derived from the arm64 implementation:

 * Copyright (c) 2014, The Linux Foundation, Laura Abbott.

 * (C) Copyright 2008 Intel Corporation, Arjan van de Ven.

 *

 * 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; version 2

 * of the License.

 */

#include <linux/debugfs.h>

#include <linux/fs.h>

#include <linux/io.h>

#include <linux/mm.h>

#include <linux/sched.h>

#include <linux/seq_file.h>

#include <asm/fixmap.h>

#include <asm/pgtable.h>

#include <linux/const.h>

#include <asm/page.h>

#include <asm/pgalloc.h>



/*

 * To visualise what is happening,

 *

 *  - PTRS_PER_P** = how many entries there are in the corresponding P**

 *  - P**_SHIFT = how many bits of the address we use to index into the

 * corresponding P**

 *  - P**_SIZE is how much memory we can access through the table - not the

 * size of the table itself.

 * P**={PGD, PUD, PMD, PTE}

 *

 *

 * Each entry of the PGD points to a PUD. Each entry of a PUD points to a

 * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to

 * a page.

 *

 * In the case where there are only 3 levels, the PUD is folded into the

 * PGD: every PUD has only one entry which points to the PMD.

 *

 * 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 - ie PTEs that are virtually contiguous

 * with the same PTE flags are chunked together. This is to make it clear how

 * different areas of the kernel virtual memory are used.

 *

 */

struct pg_state {

	struct seq_file *seq;

	const struct addr_marker *marker;

	unsigned long start_address;

	unsigned int level;

	u64 current_flags;

};



struct addr_marker {

	unsigned long start_address;

	const char *name;

};



static struct addr_marker address_markers[] = {

	{ 0,	"Start of kernel VM" },

	{ 0,	"vmalloc() Area" },

	{ 0,	"vmalloc() End" },

	{ 0,	"isa I/O start" },

	{ 0,	"isa I/O end" },

	{ 0,	"phb I/O start" },

	{ 0,	"phb I/O end" },

	{ 0,	"I/O remap start" },

	{ 0,	"I/O remap end" },

	{ 0,	"vmemmap start" },

	{ -1,	NULL },

};



struct flag_info {

	u64		mask;

	u64		val;

	const char	*set;

	const char	*clear;

	bool		is_val;

	int		shift;

};



static const struct flag_info flag_array[] = {

	{

#ifdef CONFIG_PPC_STD_MMU_64

		.mask	= _PAGE_PRIVILEGED,

		.val	= 0,

#else

		.mask	= _PAGE_USER,

		.val	= _PAGE_USER,

#endif

		.set	= "user",

		.clear	= "    ",

	}, {

		.mask	= _PAGE_RW,

		.val	= _PAGE_RW,

		.set	= "rw",

		.clear	= "ro",

	}, {

		.mask	= _PAGE_EXEC,

		.val	= _PAGE_EXEC,

		.set	= " X ",

		.clear	= "   ",

	}, {

		.mask	= _PAGE_PTE,

		.val	= _PAGE_PTE,

		.set	= "pte",

		.clear	= "   ",

	}, {

		.mask	= _PAGE_PRESENT,

		.val	= _PAGE_PRESENT,

		.set	= "present",

		.clear	= "       ",

	}, {

#ifdef CONFIG_PPC_STD_MMU_64

		.mask	= H_PAGE_HASHPTE,

		.val	= H_PAGE_HASHPTE,

#else

		.mask	= _PAGE_HASHPTE,

		.val	= _PAGE_HASHPTE,

#endif

		.set	= "hpte",

		.clear	= "    ",

	}, {

#ifndef CONFIG_PPC_STD_MMU_64

		.mask	= _PAGE_GUARDED,

		.val	= _PAGE_GUARDED,

		.set	= "guarded",

		.clear	= "       ",

	}, {

#endif

		.mask	= _PAGE_DIRTY,

		.val	= _PAGE_DIRTY,

		.set	= "dirty",

		.clear	= "     ",

	}, {

		.mask	= _PAGE_ACCESSED,

		.val	= _PAGE_ACCESSED,

		.set	= "accessed",

		.clear	= "        ",

	}, {

#ifndef CONFIG_PPC_STD_MMU_64

		.mask	= _PAGE_WRITETHRU,

		.val	= _PAGE_WRITETHRU,

		.set	= "write through",

		.clear	= "             ",

	}, {

#endif

		.mask	= _PAGE_NO_CACHE,

		.val	= _PAGE_NO_CACHE,

		.set	= "no cache",

		.clear	= "        ",

	}, {

		.mask	= H_PAGE_BUSY,

		.val	= H_PAGE_BUSY,

		.set	= "busy",

	}, {

#ifdef CONFIG_PPC_64K_PAGES

		.mask	= H_PAGE_COMBO,

		.val	= H_PAGE_COMBO,

		.set	= "combo",

	}, {

		.mask	= H_PAGE_4K_PFN,

		.val	= H_PAGE_4K_PFN,

		.set	= "4K_pfn",

	}, {

#endif

		.mask	= H_PAGE_F_GIX,

		.val	= H_PAGE_F_GIX,

		.set	= "f_gix",

		.is_val	= true,

		.shift	= H_PAGE_F_GIX_SHIFT,

	}, {

		.mask	= H_PAGE_F_SECOND,

		.val	= H_PAGE_F_SECOND,

		.set	= "f_second",

	}, {

		.mask	= _PAGE_SPECIAL,

		.val	= _PAGE_SPECIAL,

		.set	= "special",

	}

};



struct pgtable_level {

	const struct flag_info *flag;

	size_t num;

	u64 mask;

};



static struct pgtable_level pg_level[] = {

	{

	}, { /* pgd */

		.flag	= flag_array,

		.num	= ARRAY_SIZE(flag_array),

	}, { /* pud */

		.flag	= flag_array,

		.num	= ARRAY_SIZE(flag_array),

	}, { /* pmd */

		.flag	= flag_array,

		.num	= ARRAY_SIZE(flag_array),

	}, { /* pte */

		.flag	= flag_array,

		.num	= ARRAY_SIZE(flag_array),

	},

};



static void dump_flag_info(struct pg_state *st, const struct flag_info

		*flag, u64 pte, int num)

{

	unsigned int i;



	for (i = 0; i < num; i++, flag++) {

		const char *s = NULL;

		u64 val;



		/* flag not defined so don't check it */

		if (flag->mask == 0)

			continue;

		/* Some 'flags' are actually values */

		if (flag->is_val) {

			val = pte & flag->val;

			if (flag->shift)

				val = val >> flag->shift;

			seq_printf(st->seq, "  %s:%llx", flag->set, val);

		} else {

			if ((pte & flag->mask) == flag->val)

				s = flag->set;

			else

				s = flag->clear;

			if (s)

				seq_printf(st->seq, "  %s", s);

		}

		st->current_flags &= ~flag->mask;

	}

	if (st->current_flags != 0)

		seq_printf(st->seq, "  unknown flags:%llx", st->current_flags);

}



static void dump_addr(struct pg_state *st, unsigned long addr)

{

	static const char units[] = "KMGTPE";

	const char *unit = units;

	unsigned long delta;



	seq_printf(st->seq, "0x%016lx-0x%016lx   ", st->start_address, addr-1);

	delta = (addr - st->start_address) >> 10;

	/* Work out what appropriate unit to use */

	while (!(delta & 1023) && unit[1]) {

		delta >>= 10;

		unit++;

	}

	seq_printf(st->seq, "%9lu%c", delta, *unit);



}



static void note_page(struct pg_state *st, unsigned long addr,

	       unsigned int level, u64 val)

{

	u64 flag = val & pg_level[level].mask;

	/* At first no level is set */

	if (!st->level) {

		st->level = level;

		st->current_flags = flag;

		st->start_address = addr;

		seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);

	/*

	 * Dump the section of virtual memory when:

	 *   - the PTE flags from one entry to the next differs.

	 *   - we change levels in the tree.

	 *   - the address is in a different section of memory and is thus

	 *   used for a different purpose, regardless of the flags.

	 */

	} else if (flag != st->current_flags || level != st->level ||

		   addr >= st->marker[1].start_address) {



		/* Check the PTE flags */

		if (st->current_flags) {

			dump_addr(st, addr);



			/* Dump all the flags */

			if (pg_level[st->level].flag)

				dump_flag_info(st, pg_level[st->level].flag,

					  st->current_flags,

					  pg_level[st->level].num);



			seq_puts(st->seq, "\n");

		}



		/*

		 * Address indicates we have passed the end of the

		 * current section of virtual memory

		 */

		while (addr >= st->marker[1].start_address) {

			st->marker++;

			seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);

		}

		st->start_address = addr;

		st->current_flags = flag;

		st->level = level;

	}

}



static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)

{

	pte_t *pte = pte_offset_kernel(pmd, 0);

	unsigned long addr;

	unsigned int i;



	for (i = 0; i < PTRS_PER_PTE; i++, pte++) {

		addr = start + i * PAGE_SIZE;

		note_page(st, addr, 4, pte_val(*pte));



	}

}



static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)

{

	pmd_t *pmd = pmd_offset(pud, 0);

	unsigned long addr;

	unsigned int i;



	for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {

		addr = start + i * PMD_SIZE;

		if (!pmd_none(*pmd))

			/* pmd exists */

			walk_pte(st, pmd, addr);

		else

			note_page(st, addr, 3, pmd_val(*pmd));

	}

}



static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)

{

	pud_t *pud = pud_offset(pgd, 0);

	unsigned long addr;

	unsigned int i;



	for (i = 0; i < PTRS_PER_PUD; i++, pud++) {

		addr = start + i * PUD_SIZE;

		if (!pud_none(*pud))

			/* pud exists */

			walk_pmd(st, pud, addr);

		else

			note_page(st, addr, 2, pud_val(*pud));

	}

}



static void walk_pagetables(struct pg_state *st)

{

	pgd_t *pgd = pgd_offset_k(0UL);

	unsigned int i;

	unsigned long addr;



	/*

	 * Traverse the linux pagetable structure and dump pages that are in

	 * the hash pagetable.

	 */

	for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {

		addr = KERN_VIRT_START + i * PGDIR_SIZE;

		if (!pgd_none(*pgd))

			/* pgd exists */

			walk_pud(st, pgd, addr);

		else

			note_page(st, addr, 1, pgd_val(*pgd));

	}

}



static void populate_markers(void)

{

	address_markers[0].start_address = PAGE_OFFSET;

	address_markers[1].start_address = VMALLOC_START;

	address_markers[2].start_address = VMALLOC_END;

	address_markers[3].start_address = ISA_IO_BASE;

	address_markers[4].start_address = ISA_IO_END;

	address_markers[5].start_address = PHB_IO_BASE;

	address_markers[6].start_address = PHB_IO_END;

	address_markers[7].start_address = IOREMAP_BASE;

	address_markers[8].start_address = IOREMAP_END;

#ifdef CONFIG_PPC_STD_MMU_64

	address_markers[9].start_address =  H_VMEMMAP_BASE;

#else

	address_markers[9].start_address =  VMEMMAP_BASE;

#endif

}



static int ptdump_show(struct seq_file *m, void *v)

{

	struct pg_state st = {

		.seq = m,

		.start_address = KERN_VIRT_START,

		.marker = address_markers,

	};

	/* Traverse kernel page tables */

	walk_pagetables(&st);

	note_page(&st, 0, 0, 0);

	return 0;

}





static int ptdump_open(struct inode *inode, struct file *file)

{

	return single_open(file, ptdump_show, NULL);

}



static const struct file_operations ptdump_fops = {

	.open		= ptdump_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= single_release,

};



static void build_pgtable_complete_mask(void)

{

	unsigned int i, j;



	for (i = 0; i < ARRAY_SIZE(pg_level); i++)

		if (pg_level[i].flag)

			for (j = 0; j < pg_level[i].num; j++)

				pg_level[i].mask |= pg_level[i].flag[j].mask;

}



static int ptdump_init(void)

{

	struct dentry *debugfs_file;



	populate_markers();

	build_pgtable_complete_mask();

	debugfs_file = debugfs_create_file("kernel_pagetables", 0400, NULL,

			NULL, &ptdump_fops);

	return debugfs_file ? 0 : -ENOMEM;

}

device_initcall(ptdump_init);

CRA Git | Maintained and supported by SUSTech CRA and CCSE