Commit 30d621f6 authored by Steven Price's avatar Steven Price Committed by Linus Torvalds
Browse files

mm: add generic ptdump 

Add a generic version of page table dumping that architectures can opt-in
to.

Link: http://lkml.kernel.org/r/20191218162402.45610-20-steven.price@arm.com


Signed-off-by: default avatarSteven Price <steven.price@arm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zong Li <zong.li@sifive.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c5cfae12

include/linux/ptdump.h

0 → 100644
+21 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#ifndef _LINUX_PTDUMP_H

#define _LINUX_PTDUMP_H



#include <linux/mm_types.h>



struct ptdump_range {

	unsigned long start;

	unsigned long end;

};



struct ptdump_state {

	void (*note_page)(struct ptdump_state *st, unsigned long addr,

			  int level, unsigned long val);

	const struct ptdump_range *range;

};



void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm);



#endif /* _LINUX_PTDUMP_H */

mm/Kconfig.debug

+21 −0
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@@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST 
    depends on STRICT_KERNEL_RWX

    ---help---

      This option enables a testcase for the setting rodata read-only.



config GENERIC_PTDUMP

	bool



config PTDUMP_CORE

	bool



config PTDUMP_DEBUGFS

	bool "Export kernel pagetable layout to userspace via debugfs"

	depends on DEBUG_KERNEL

	depends on DEBUG_FS

	depends on GENERIC_PTDUMP

	select PTDUMP_CORE

	help

	  Say Y here if you want to show the kernel pagetable layout in a

	  debugfs file. This information is only useful for kernel developers

	  who are working in architecture specific areas of the kernel.

	  It is probably not a good idea to enable this feature in a production

	  kernel.



	  If in doubt, say N.

mm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -109,3 +109,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o 
obj-$(CONFIG_HMM_MIRROR) += hmm.o

obj-$(CONFIG_MEMFD_CREATE) += memfd.o

obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o

obj-$(CONFIG_PTDUMP_CORE) += ptdump.o

mm/ptdump.c

0 → 100644
+139 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <linux/pagewalk.h>

#include <linux/ptdump.h>

#include <linux/kasan.h>



#ifdef CONFIG_KASAN

/*

 * This is an optimization for KASAN=y case. Since all kasan page tables

 * eventually point to the kasan_early_shadow_page we could call note_page()

 * right away without walking through lower level page tables. This saves

 * us dozens of seconds (minutes for 5-level config) while checking for

 * W+X mapping or reading kernel_page_tables debugfs file.

 */

static inline int note_kasan_page_table(struct mm_walk *walk,

					unsigned long addr)

{

	struct ptdump_state *st = walk->private;



	st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0]));



	walk->action = ACTION_CONTINUE;



	return 0;

}

#endif



static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,

			    unsigned long next, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;

	pgd_t val = READ_ONCE(*pgd);



#if CONFIG_PGTABLE_LEVELS > 4 && defined(CONFIG_KASAN)

	if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d)))

		return note_kasan_page_table(walk, addr);

#endif



	if (pgd_leaf(val))

		st->note_page(st, addr, 1, pgd_val(val));



	return 0;

}



static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,

			    unsigned long next, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;

	p4d_t val = READ_ONCE(*p4d);



#if CONFIG_PGTABLE_LEVELS > 3 && defined(CONFIG_KASAN)

	if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))

		return note_kasan_page_table(walk, addr);

#endif



	if (p4d_leaf(val))

		st->note_page(st, addr, 2, p4d_val(val));



	return 0;

}



static int ptdump_pud_entry(pud_t *pud, unsigned long addr,

			    unsigned long next, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;

	pud_t val = READ_ONCE(*pud);



#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_KASAN)

	if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))

		return note_kasan_page_table(walk, addr);

#endif



	if (pud_leaf(val))

		st->note_page(st, addr, 3, pud_val(val));



	return 0;

}



static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,

			    unsigned long next, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;

	pmd_t val = READ_ONCE(*pmd);



#if defined(CONFIG_KASAN)

	if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))

		return note_kasan_page_table(walk, addr);

#endif



	if (pmd_leaf(val))

		st->note_page(st, addr, 4, pmd_val(val));



	return 0;

}



static int ptdump_pte_entry(pte_t *pte, unsigned long addr,

			    unsigned long next, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;



	st->note_page(st, addr, 5, pte_val(READ_ONCE(*pte)));



	return 0;

}



static int ptdump_hole(unsigned long addr, unsigned long next,

		       int depth, struct mm_walk *walk)

{

	struct ptdump_state *st = walk->private;



	st->note_page(st, addr, depth + 1, 0);



	return 0;

}



static const struct mm_walk_ops ptdump_ops = {

	.pgd_entry	= ptdump_pgd_entry,

	.p4d_entry	= ptdump_p4d_entry,

	.pud_entry	= ptdump_pud_entry,

	.pmd_entry	= ptdump_pmd_entry,

	.pte_entry	= ptdump_pte_entry,

	.pte_hole	= ptdump_hole,

};



void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)

{

	const struct ptdump_range *range = st->range;



	down_read(&mm->mmap_sem);

	while (range->start != range->end) {

		walk_page_range_novma(mm, range->start, range->end,

				      &ptdump_ops, st);

		range++;

	}

	up_read(&mm->mmap_sem);



	/* Flush out the last page */

	st->note_page(st, 0, 0, 0);

}

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