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

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.comSigned-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
/* 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 */
...@@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST ...@@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST
depends on STRICT_KERNEL_RWX depends on STRICT_KERNEL_RWX
---help--- ---help---
This option enables a testcase for the setting rodata read-only. 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.
...@@ -109,3 +109,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o ...@@ -109,3 +109,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o
obj-$(CONFIG_HMM_MIRROR) += hmm.o obj-$(CONFIG_HMM_MIRROR) += hmm.o
obj-$(CONFIG_MEMFD_CREATE) += memfd.o obj-$(CONFIG_MEMFD_CREATE) += memfd.o
obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
// 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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